CUB-117: Port Moonraker + MQTT printer integrations to Go

- Add internal/clients/moonraker.go: HTTP client for Moonraker REST API
- Add internal/clients/mqtt.go: MQTT client via paho.mqtt.golang with TLS support
- Add internal/workers/moonraker_poller.go: background polling, usage logging, SSE broadcasts
- Add internal/workers/mqtt_subscriber.go: per-printer MQTT subscriber, Bambu telemetry parsing, SSE broadcasts
- Wire workers into cmd/server/main.go (Start/Stop with graceful shutdown)

Blocked at step 4: go toolchain not installed on build host

backend/cmd/server/main.go

@@ -11,7 +11,10 @@ import (
 
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/config"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/db"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/router"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/workers"
 )
 
 func main() {
@@ -39,15 +42,42 @@ func main() {
 
 	slog.Info("database connected")
 
+	// Repositories (for background workers)
+	printerRepo := repositories.NewPrinterRepository(dbPool)
+	jobRepo := repositories.NewPrintJobRepository(dbPool)
+	usageLogRepo := repositories.NewUsageLogRepository(dbPool)
+
+	// Create SSE broadcaster and start it
+	sseBC := sse.NewBroadcaster(128)
+	sseBC.Start()
+	defer sseBC.Stop()
+
+	slog.Info("sse broadcaster started")
+
+	// Start background workers
+	mrCfg := workers.DefaultMoonrakerPollerConfig()
+	mrPoller := workers.NewMoonrakerPoller(mrCfg, dbPool, printerRepo, jobRepo, usageLogRepo, sseBC)
+	mrPoller.Start()
+	defer mrPoller.Stop()
+
+	mqttCfg := workers.DefaultMQTTSubscriberConfig()
+	mqttSub := workers.NewMQTTSubscriber(mqttCfg, dbPool, printerRepo, usageLogRepo, sseBC)
+	mqttSub.Start()
+	defer mqttSub.Stop()
+
+	slog.Info("background workers started")
+
 	// Create router
-	r := router.New(cfg, dbPool)
+	r := router.New(cfg, dbPool, sseBC)
 
 	// Create HTTP server
+	// WriteTimeout is 0 for SSE support — the Chi middleware.Timeout(60s)
+	// handles request-level timeouts on non-SSE routes.
 	server := &http.Server{
 		Addr:         ":" + cfg.Port,
 		Handler:      r,
 		ReadTimeout:  15 * time.Second,
-		WriteTimeout: 15 * time.Second,
+		WriteTimeout: 0, // disabled for SSE long-lived connections
 		IdleTimeout:  60 * time.Second,
 	}
 

backend/go.mod

@@ -7,3 +7,12 @@ require (
 	github.com/jackc/pgx/v5 v5.7.4
 	github.com/kelseyhightower/envconfig v1.4.0
 )
+
+require (
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	golang.org/x/crypto v0.31.0 // indirect
+	golang.org/x/sync v0.10.0 // indirect
+	golang.org/x/text v0.21.0 // indirect
+)

backend/go.sum

@@ -0,0 +1,32 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-chi/chi/v5 v5.2.0 h1:Aj1EtB0qR2Rdo2dG4O94RIU35w2lvQSj6BRA4+qwFL0=
+github.com/go-chi/chi/v5 v5.2.0/go.mod h1:DslCQbL2OYiznFReuXYUmQ2hGd1aDpCnlMNITLSKoi8=
+github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
+github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
+github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
+github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
+github.com/jackc/pgx/v5 v5.7.4 h1:9wKznZrhWa2QiHL+NjTSPP6yjl3451BX3imWDnokYlg=
+github.com/jackc/pgx/v5 v5.7.4/go.mod h1:ncY89UGWxg82EykZUwSpUKEfccBGGYq1xjrOpsbsfGQ=
+github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
+github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
+github.com/kelseyhightower/envconfig v1.4.0 h1:Im6hONhd3pLkfDFsbRgu68RDNkGF1r3dvMUtDTo2cv8=
+github.com/kelseyhightower/envconfig v1.4.0/go.mod h1:cccZRl6mQpaq41TPp5QxidR+Sa3axMbJDNb//FQX6Gg=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
+golang.org/x/crypto v0.31.0 h1:ihbySMvVjLAeSH1IbfcRTkD/iNscyz8rGzjF/E5hV6U=
+golang.org/x/crypto v0.31.0/go.mod h1:kDsLvtWBEx7MV9tJOj9bnXsPbxwJQ6csT/x4KIN4Ssk=
+golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
+golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

backend/internal/clients/moonraker.go

@@ -0,0 +1,161 @@
+// Package clients provides third-party printer integrations.
+package clients
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"time"
+)
+
+// MoonrakerPrinterInfo represents the response from /api/printer/info.
+type MoonrakerPrinterInfo struct {
+	State      string `json:"state"`
+	Hostname   string `json:"hostname,omitempty"`
+	SoftwareVersion string `json:"software_version,omitempty"`
+}
+
+// MoonrakerPrintStats represents the response from /api/printer/print_stats.
+type MoonrakerPrintStats struct {
+	State            string  `json:"state"`
+	Filename         string  `json:"filename,omitempty"`
+	FilamentUsedMm   float64 `json:"filament_used,omitempty"`
+	TotalDuration    float64 `json:"total_duration,omitempty"`
+	PrintDuration    float64 `json:"print_duration,omitempty"`
+	Message          string  `json:"message,omitempty"`
+}
+
+// MoonrakerPrintJob represents a single job from the history API.
+type MoonrakerPrintJob struct {
+	JobID          string    `json:"job_id,omitempty"`
+	Filename       string    `json:"filename"`
+	Status         string    `json:"status"`
+	StartTime      time.Time `json:"start_time"`
+	EndTime        time.Time `json:"end_time,omitempty"`
+	FilamentUsedMm float64   `json:"filament_used,omitempty"`
+	TotalDuration  float64   `json:"total_duration,omitempty"`
+}
+
+// MoonrakerHistoryResponse represents the response from /api/server/history/job.
+type MoonrakerHistoryResponse struct {
+	Items []MoonrakerPrintJob `json:"jobs"`
+}
+
+// MoonrakerClient is an HTTP client for the Moonraker API.
+type MoonrakerClient struct {
+	HTTPClient *http.Client
+}
+
+// NewMoonrakerClient creates a MoonrakerClient with the given request timeout.
+func NewMoonrakerClient(timeout time.Duration) *MoonrakerClient {
+	return &MoonrakerClient{
+		HTTPClient: &http.Client{Timeout: timeout},
+	}
+}
+
+// baseURL builds the Moonraker base URL from host and port.
+func (c *MoonrakerClient) baseURL(host string, port int) string {
+	if port == 0 {
+		port = 80
+	}
+	return fmt.Sprintf("http://%s:%d", host, port)
+}
+
+// GetPrinterInfo fetches printer info from Moonraker.
+func (c *MoonrakerClient) GetPrinterInfo(ctx context.Context, host string, port int, apiKey string) (*MoonrakerPrinterInfo, error) {
+	url := c.baseURL(host, port) + "/api/printer/info"
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("X-Api-Key", apiKey)
+	}
+
+	resp, err := c.HTTPClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("moonraker getPrinterInfo request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("moonraker getPrinterInfo returned status %d", resp.StatusCode)
+	}
+
+	var body struct {
+		Result MoonrakerPrinterInfo `json:"result"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		return nil, fmt.Errorf("moonraker getPrinterInfo decode failed: %w", err)
+	}
+
+	slog.Debug("moonraker printer info", "host", host, "state", body.Result.State)
+	return &body.Result, nil
+}
+
+// GetPrintStats fetches current print statistics from Moonraker.
+func (c *MoonrakerClient) GetPrintStats(ctx context.Context, host string, port int, apiKey string) (*MoonrakerPrintStats, error) {
+	url := c.baseURL(host, port) + "/api/printer/print_stats"
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("X-Api-Key", apiKey)
+	}
+
+	resp, err := c.HTTPClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("moonraker getPrintStats request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("moonraker getPrintStats returned status %d", resp.StatusCode)
+	}
+
+	var body struct {
+		Result MoonrakerPrintStats `json:"result"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		return nil, fmt.Errorf("moonraker getPrintStats decode failed: %w", err)
+	}
+
+	slog.Debug("moonraker print stats", "host", host, "state", body.Result.State, "filename", body.Result.Filename)
+	return &body.Result, nil
+}
+
+// GetPrintHistory fetches completed print job history from Moonraker.
+func (c *MoonrakerClient) GetPrintHistory(ctx context.Context, host string, port int, apiKey string, limit int) (*MoonrakerHistoryResponse, error) {
+	if limit <= 0 {
+		limit = 25
+	}
+	url := fmt.Sprintf("%s/api/server/history/job?limit=%d", c.baseURL(host, port), limit)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("X-Api-Key", apiKey)
+	}
+
+	resp, err := c.HTTPClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("moonraker getPrintHistory request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("moonraker getPrintHistory returned status %d", resp.StatusCode)
+	}
+
+	var body MoonrakerHistoryResponse
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		return nil, fmt.Errorf("moonraker getPrintHistory decode failed: %w", err)
+	}
+
+	slog.Debug("moonraker print history", "host", host, "count", len(body.Items))
+	return &body, nil
+}

backend/internal/clients/mqtt.go

@@ -0,0 +1,119 @@
+// Package clients provides third-party printer integrations.
+package clients
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"time"
+
+	mqtt "github.com/eclipse/paho.mqtt.golang"
+)
+
+// MQTTClient wraps the Eclipse Paho MQTT client for printer telemetry.
+type MQTTClient struct {
+	client mqtt.Client
+}
+
+// MQTTConfig holds per-printer MQTT connection settings.
+type MQTTConfig struct {
+	BrokerHost  string
+	BrokerPort  int
+	TopicPrefix string
+	TLSEnabled  bool
+	ClientID    string
+}
+
+// BambuPrintStatus is the known Bambu Lab print-status payload shape.
+type BambuPrintStatus struct {
+	Print struct {
+		GcodeFile       string  `json:"gcode_file,omitempty"`
+		Stage           int     `json:"stage,omitempty"`
+		SubTaskName     string  `json:"subtask_name,omitempty"`
+		PrintType       string  `json:"print_type,omitempty"`
+		FilamentUsedMm  float64 `json:"mc_percent,omitempty"` // placeholder; real telemetry varies
+	} `json:"print,omitempty"`
+}
+
+// NewMQTTClient creates an MQTT client connected to the given broker.
+func NewMQTTClient(cfg MQTTConfig) (*MQTTClient, error) {
+	if cfg.BrokerPort == 0 {
+		if cfg.TLSEnabled {
+			cfg.BrokerPort = 8883
+		} else {
+			cfg.BrokerPort = 1883
+		}
+	}
+	if cfg.ClientID == "" {
+		cfg.ClientID = fmt.Sprintf("extrudex-%d", time.Now().Unix())
+	}
+
+	opts := mqtt.NewClientOptions().
+		AddBroker(fmt.Sprintf("tcp://%s:%d", cfg.BrokerHost, cfg.BrokerPort)).
+		SetClientID(cfg.ClientID).
+		SetAutoReconnect(true).
+		SetConnectTimeout(10 * time.Second).
+		SetOrderMatters(false)
+
+	if cfg.TLSEnabled {
+		opts = opts.SetTLSConfig(&tls.Config{InsecureSkipVerify: false})
+	}
+
+	client := mqtt.NewClient(opts)
+	token := client.Connect()
+	if token.Wait() && token.Error() != nil {
+		return nil, fmt.Errorf("mqtt connect failed: %w", token.Error())
+	}
+
+	slog.Info("mqtt client connected", "broker", cfg.BrokerHost, "port", cfg.BrokerPort, "tls", cfg.TLSEnabled)
+	return &MQTTClient{client: client}, nil
+}
+
+// Subscribe registers a callback for messages matching topic.
+func (c *MQTTClient) Subscribe(topic string, qos byte, callback func([]byte)) error {
+	token := c.client.Subscribe(topic, qos, func(_ mqtt.Client, msg mqtt.Message) {
+		callback(msg.Payload())
+	})
+	if token.Wait() && token.Error() != nil {
+		return fmt.Errorf("mqtt subscribe failed: %w", token.Error())
+	}
+	slog.Info("mqtt subscribed", "topic", topic, "qos", qos)
+	return nil
+}
+
+// Unsubscribe removes a subscription.
+func (c *MQTTClient) Unsubscribe(topics ...string) error {
+	token := c.client.Unsubscribe(topics...)
+	if token.Wait() && token.Error() != nil {
+		return fmt.Errorf("mqtt unsubscribe failed: %w", token.Error())
+	}
+	return nil
+}
+
+// Disconnect cleanly disconnects the MQTT client.
+func (c *MQTTClient) Disconnect(quiesceMs uint) {
+	c.client.Disconnect(quiesceMs)
+}
+
+// IsConnected returns whether the underlying client is connected.
+func (c *MQTTClient) IsConnected() bool {
+	return c.client.IsConnected()
+}
+
+// ParseBambuTelemetry attempts to parse a Bambu Lab telemetry JSON payload.
+func ParseBambuTelemetry(payload []byte) (*BambuPrintStatus, error) {
+	var msg BambuPrintStatus
+	if err := json.Unmarshal(payload, &msg); err != nil {
+		return nil, fmt.Errorf("parse bambu telemetry failed: %w", err)
+	}
+	return &msg, nil
+}
+
+// DefaultBambuTopics returns the default topic patterns for Bambu Lab printers.
+func DefaultBambuTopics(topicPrefix string) []string {
+	return []string{
+		topicPrefix + "/report",
+	}
+}

backend/internal/dtos/dtos.go

@@ -0,0 +1,67 @@
+// Package dtos defines request/response data transfer objects for the Extrudex API.
+// DTOs keep HTTP serialization concerns separate from domain models.
+package dtos
+
+// ============================================================================
+// Common Response Wrappers
+// ============================================================================
+
+// ListResponse wraps a paginated collection response.
+type ListResponse struct {
+	Data   any `json:"data"`
+	Total  int `json:"total"`
+	Limit  int `json:"limit"`
+	Offset int `json:"offset"`
+}
+
+// SingleResponse wraps a single-item response.
+type SingleResponse struct {
+	Data any `json:"data"`
+}
+
+// ErrorResponse is the standard error payload for all API errors.
+type ErrorResponse struct {
+	Error string `json:"error"`
+	Code  int    `json:"code"`
+}
+
+// ============================================================================
+// Filament DTOs
+// ============================================================================
+
+// CreateFilamentRequest is the POST body for creating a new filament spool.
+type CreateFilamentRequest struct {
+	Name                  string  `json:"name"`
+	MaterialBaseID        int     `json:"material_base_id"`
+	MaterialFinishID      int     `json:"material_finish_id"`
+	MaterialModifierID    *int    `json:"material_modifier_id,omitempty"`
+	ColorHex             string  `json:"color_hex"`
+	Brand                *string `json:"brand,omitempty"`
+	DiameterMM           *float64 `json:"diameter_mm,omitempty"` // defaults to 1.75
+	InitialGrams         int     `json:"initial_grams"`
+	RemainingGrams       int     `json:"remaining_grams"`
+	SpoolWeightGrams     *int    `json:"spool_weight_grams,omitempty"`
+	CostUSD              *float64 `json:"cost_usd,omitempty"`
+	LowStockThresholdGrams *int  `json:"low_stock_threshold_grams,omitempty"` // defaults to 50
+	Notes                *string `json:"notes,omitempty"`
+	Barcode              *string `json:"barcode,omitempty"`
+}
+
+// UpdateFilamentRequest is the PUT body for partially updating a filament spool.
+// All fields are optional — only non-nil fields are applied.
+type UpdateFilamentRequest struct {
+	Name                  *string  `json:"name,omitempty"`
+	MaterialBaseID        *int     `json:"material_base_id,omitempty"`
+	MaterialFinishID      *int     `json:"material_finish_id,omitempty"`
+	MaterialModifierID    *int     `json:"material_modifier_id,omitempty"`
+	ColorHex             *string  `json:"color_hex,omitempty"`
+	Brand                *string  `json:"brand,omitempty"`
+	DiameterMM           *float64 `json:"diameter_mm,omitempty"`
+	InitialGrams         *int     `json:"initial_grams,omitempty"`
+	RemainingGrams       *int     `json:"remaining_grams,omitempty"`
+	SpoolWeightGrams     *int     `json:"spool_weight_grams,omitempty"`
+	CostUSD              *float64 `json:"cost_usd,omitempty"`
+	LowStockThresholdGrams *int   `json:"low_stock_threshold_grams,omitempty"`
+	Notes                *string  `json:"notes,omitempty"`
+	Barcode              *string  `json:"barcode,omitempty"`
+}

backend/internal/handlers/filament_handler.go

@@ -0,0 +1,273 @@
+package handlers
+
+import (
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"strconv"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/services"
+	"github.com/go-chi/chi/v5"
+)
+
+// FilamentHandler handles HTTP requests for filament spool CRUD operations.
+type FilamentHandler struct {
+	service *services.FilamentService
+}
+
+// NewFilamentHandler creates a FilamentHandler with the given service.
+func NewFilamentHandler(service *services.FilamentService) *FilamentHandler {
+	return &FilamentHandler{service: service}
+}
+
+// List handles GET /api/filaments — returns paginated, filtered spools.
+func (h *FilamentHandler) List(w http.ResponseWriter, r *http.Request) {
+	limit, offset := parsePagination(r)
+	filter := repositories.FilamentFilter{
+		Material: r.URL.Query().Get("material"),
+		Finish:   r.URL.Query().Get("finish"),
+		Color:    r.URL.Query().Get("color"),
+		LowStock: r.URL.Query().Get("low_stock") == "true",
+		Limit:    limit,
+		Offset:   offset,
+	}
+
+	spools, total, err := h.service.List(r.Context(), filter)
+	if err != nil {
+		slog.Error("failed to list filaments", "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.ListResponse{
+		Data:   spools,
+		Total:  total,
+		Limit:  limit,
+		Offset: offset,
+	})
+}
+
+// Get handles GET /api/filaments/{id} — returns a single spool.
+func (h *FilamentHandler) Get(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.Atoi(chi.URLParam(r, "id"))
+	if err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "invalid filament ID",
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	spool, err := h.service.GetByID(r.Context(), id)
+	if err != nil {
+		slog.Error("failed to get filament", "id", id, "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+	if spool == nil {
+		writeJSON(w, http.StatusNotFound, dtos.ErrorResponse{
+			Error: "filament not found",
+			Code:  http.StatusNotFound,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.SingleResponse{Data: spool})
+}
+
+// Create handles POST /api/filaments — creates a new filament spool.
+func (h *FilamentHandler) Create(w http.ResponseWriter, r *http.Request) {
+	var req dtos.CreateFilamentRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "invalid request body",
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	// Validate required fields.
+	if err := services.ValidateCreateFilamentRequest(req); err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "validation failed: " + err.Error(),
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	// Build domain model.
+	spool := models.FilamentSpool{
+		Name:                  req.Name,
+		MaterialBaseID:        req.MaterialBaseID,
+		MaterialFinishID:      req.MaterialFinishID,
+		MaterialModifierID:    req.MaterialModifierID,
+		ColorHex:             req.ColorHex,
+		Brand:                req.Brand,
+		DiameterMM:           1.75, // default
+		InitialGrams:         req.InitialGrams,
+		RemainingGrams:       req.RemainingGrams,
+		SpoolWeightGrams:     req.SpoolWeightGrams,
+		CostUSD:              req.CostUSD,
+		LowStockThresholdGrams: 50, // default
+		Notes:                req.Notes,
+		Barcode:              req.Barcode,
+	}
+	if req.DiameterMM != nil {
+		spool.DiameterMM = *req.DiameterMM
+	}
+	if req.LowStockThresholdGrams != nil {
+		spool.LowStockThresholdGrams = *req.LowStockThresholdGrams
+	}
+
+	created, err := h.service.Create(r.Context(), &spool)
+	if err != nil {
+		slog.Error("failed to create filament", "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, dtos.SingleResponse{Data: created})
+}
+
+// Update handles PUT /api/filaments/{id} — partially updates a spool.
+func (h *FilamentHandler) Update(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.Atoi(chi.URLParam(r, "id"))
+	if err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "invalid filament ID",
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	var req dtos.UpdateFilamentRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "invalid request body",
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	// Validate update fields.
+	if err := services.ValidateUpdateFilamentRequest(req); err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "validation failed: " + err.Error(),
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	// Build updates map (only non-nil fields).
+	updates := buildFilamentUpdates(req)
+
+	updated, err := h.service.Update(r.Context(), id, updates)
+	if err != nil {
+		slog.Error("failed to update filament", "id", id, "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+	if updated == nil {
+		writeJSON(w, http.StatusNotFound, dtos.ErrorResponse{
+			Error: "filament not found",
+			Code:  http.StatusNotFound,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.SingleResponse{Data: updated})
+}
+
+// Delete handles DELETE /api/filaments/{id} — soft-deletes a spool.
+func (h *FilamentHandler) Delete(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.Atoi(chi.URLParam(r, "id"))
+	if err != nil {
+		writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+			Error: "invalid filament ID",
+			Code:  http.StatusBadRequest,
+		})
+		return
+	}
+
+	deleted, err := h.service.SoftDelete(r.Context(), id)
+	if err != nil {
+		slog.Error("failed to delete filament", "id", id, "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+	if !deleted {
+		writeJSON(w, http.StatusNotFound, dtos.ErrorResponse{
+			Error: "filament not found",
+			Code:  http.StatusNotFound,
+		})
+		return
+	}
+
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// buildFilamentUpdates converts an UpdateFilamentRequest to a map of column→value.
+func buildFilamentUpdates(req dtos.UpdateFilamentRequest) map[string]interface{} {
+	updates := make(map[string]interface{})
+	if req.Name != nil {
+		updates["name"] = *req.Name
+	}
+	if req.MaterialBaseID != nil {
+		updates["material_base_id"] = *req.MaterialBaseID
+	}
+	if req.MaterialFinishID != nil {
+		updates["material_finish_id"] = *req.MaterialFinishID
+	}
+	if req.MaterialModifierID != nil {
+		updates["material_modifier_id"] = *req.MaterialModifierID
+	}
+	if req.ColorHex != nil {
+		updates["color_hex"] = *req.ColorHex
+	}
+	if req.Brand != nil {
+		updates["brand"] = *req.Brand
+	}
+	if req.DiameterMM != nil {
+		updates["diameter_mm"] = *req.DiameterMM
+	}
+	if req.InitialGrams != nil {
+		updates["initial_grams"] = *req.InitialGrams
+	}
+	if req.RemainingGrams != nil {
+		updates["remaining_grams"] = *req.RemainingGrams
+	}
+	if req.SpoolWeightGrams != nil {
+		updates["spool_weight_grams"] = *req.SpoolWeightGrams
+	}
+	if req.CostUSD != nil {
+		updates["cost_usd"] = *req.CostUSD
+	}
+	if req.LowStockThresholdGrams != nil {
+		updates["low_stock_threshold_grams"] = *req.LowStockThresholdGrams
+	}
+	if req.Notes != nil {
+		updates["notes"] = *req.Notes
+	}
+	if req.Barcode != nil {
+		updates["barcode"] = *req.Barcode
+	}
+	return updates
+}

backend/internal/handlers/helpers.go

@@ -0,0 +1,51 @@
+package handlers
+
+import (
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"strconv"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/services"
+)
+
+// writeJSON serializes v as JSON to the response writer with the given status code.
+// Logs an error if encoding fails.
+func writeJSON(w http.ResponseWriter, status int, v interface{}) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(v); err != nil {
+		slog.Error("failed to encode JSON response", "error", err)
+	}
+}
+
+// parsePagination reads limit and offset query parameters with defaults of 20 and 0.
+func parsePagination(r *http.Request) (limit, offset int) {
+	limit = 20
+	offset = 0
+
+	if l := r.URL.Query().Get("limit"); l != "" {
+		if parsed, err := strconv.Atoi(l); err == nil && parsed > 0 {
+			limit = parsed
+		}
+	}
+	if o := r.URL.Query().Get("offset"); o != "" {
+		if parsed, err := strconv.Atoi(o); err == nil && parsed >= 0 {
+			offset = parsed
+		}
+	}
+	return
+}
+
+// ValidateCreateFilamentRequest validates a CreateFilamentRequest DTO.
+// Re-exports the service-layer validator for handler use.
+func ValidateCreateFilamentRequest(req dtos.CreateFilamentRequest) error {
+	return services.ValidateCreateFilamentRequest(req)
+}
+
+// ValidateUpdateFilamentRequest validates an UpdateFilamentRequest DTO.
+// Re-exports the service-layer validator for handler use.
+func ValidateUpdateFilamentRequest(req dtos.UpdateFilamentRequest) error {
+	return services.ValidateUpdateFilamentRequest(req)
+}

backend/internal/handlers/material_handler.go

@@ -0,0 +1,34 @@
+package handlers
+
+import (
+	"log/slog"
+	"net/http"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+)
+
+// MaterialHandler handles requests for material lookup data.
+type MaterialHandler struct {
+	repo *repositories.MaterialRepository
+}
+
+// NewMaterialHandler creates a MaterialHandler with the given repository.
+func NewMaterialHandler(repo *repositories.MaterialRepository) *MaterialHandler {
+	return &MaterialHandler{repo: repo}
+}
+
+// List handles GET /api/materials — returns all material bases.
+func (h *MaterialHandler) List(w http.ResponseWriter, r *http.Request) {
+	materials, err := h.repo.GetAll(r.Context())
+	if err != nil {
+		slog.Error("failed to list materials", "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.SingleResponse{Data: materials})
+}

backend/internal/handlers/print_job_handler.go

@@ -0,0 +1,60 @@
+package handlers
+
+import (
+	"log/slog"
+	"net/http"
+	"strconv"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/services"
+)
+
+// PrintJobHandler handles HTTP requests for print job operations.
+type PrintJobHandler struct {
+	service *services.PrintJobService
+}
+
+// NewPrintJobHandler creates a PrintJobHandler with the given service.
+func NewPrintJobHandler(service *services.PrintJobService) *PrintJobHandler {
+	return &PrintJobHandler{service: service}
+}
+
+// List handles GET /api/print-jobs — returns paginated, filtered print jobs.
+func (h *PrintJobHandler) List(w http.ResponseWriter, r *http.Request) {
+	limit, offset := parsePagination(r)
+	filter := repositories.PrintJobFilter{
+		Status: r.URL.Query().Get("status"),
+		Limit:  limit,
+		Offset: offset,
+	}
+
+	if pidStr := r.URL.Query().Get("printer_id"); pidStr != "" {
+		pid, err := strconv.Atoi(pidStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+				Error: "invalid printer_id",
+				Code:  http.StatusBadRequest,
+			})
+			return
+		}
+		filter.PrinterID = &pid
+	}
+
+	jobs, total, err := h.service.List(r.Context(), filter)
+	if err != nil {
+		slog.Error("failed to list print jobs", "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.ListResponse{
+		Data:   jobs,
+		Total:  total,
+		Limit:  limit,
+		Offset: offset,
+	})
+}

backend/internal/handlers/printer_handler.go

@@ -0,0 +1,34 @@
+package handlers
+
+import (
+	"log/slog"
+	"net/http"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/services"
+)
+
+// PrinterHandler handles HTTP requests for printer listings.
+type PrinterHandler struct {
+	service *services.PrinterService
+}
+
+// NewPrinterHandler creates a PrinterHandler with the given service.
+func NewPrinterHandler(service *services.PrinterService) *PrinterHandler {
+	return &PrinterHandler{service: service}
+}
+
+// List handles GET /api/printers — returns all printers with printer_type info.
+func (h *PrinterHandler) List(w http.ResponseWriter, r *http.Request) {
+	printers, err := h.service.List(r.Context())
+	if err != nil {
+		slog.Error("failed to list printers", "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.SingleResponse{Data: printers})
+}

backend/internal/handlers/usage_log_handler.go

@@ -0,0 +1,70 @@
+package handlers
+
+import (
+	"log/slog"
+	"net/http"
+	"strconv"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+)
+
+// UsageLogHandler handles HTTP requests for usage log operations.
+type UsageLogHandler struct {
+	repo *repositories.UsageLogRepository
+}
+
+// NewUsageLogHandler creates a UsageLogHandler with the given repository.
+func NewUsageLogHandler(repo *repositories.UsageLogRepository) *UsageLogHandler {
+	return &UsageLogHandler{repo: repo}
+}
+
+// List handles GET /api/usage-logs — returns paginated, filtered usage logs.
+func (h *UsageLogHandler) List(w http.ResponseWriter, r *http.Request) {
+	limit, offset := parsePagination(r)
+	filter := repositories.UsageLogFilter{
+		Limit:  limit,
+		Offset: offset,
+	}
+
+	if sidStr := r.URL.Query().Get("spool_id"); sidStr != "" {
+		sid, err := strconv.Atoi(sidStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+				Error: "invalid spool_id",
+				Code:  http.StatusBadRequest,
+			})
+			return
+		}
+		filter.SpoolID = &sid
+	}
+
+	if jidStr := r.URL.Query().Get("job_id"); jidStr != "" {
+		jid, err := strconv.Atoi(jidStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, dtos.ErrorResponse{
+				Error: "invalid job_id",
+				Code:  http.StatusBadRequest,
+			})
+			return
+		}
+		filter.JobID = &jid
+	}
+
+	logs, total, err := h.repo.GetAll(r.Context(), filter)
+	if err != nil {
+		slog.Error("failed to list usage logs", "error", err)
+		writeJSON(w, http.StatusInternalServerError, dtos.ErrorResponse{
+			Error: "internal server error",
+			Code:  http.StatusInternalServerError,
+		})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, dtos.ListResponse{
+		Data:   logs,
+		Total:  total,
+		Limit:  limit,
+		Offset: offset,
+	})
+}

backend/internal/repositories/.gitkeep

@@ -1 +0,0 @@
-# Repositories

backend/internal/repositories/filament_repository.go

@@ -0,0 +1,285 @@
+package repositories
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// FilamentRepository handles database queries for filament_spools.
+type FilamentRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewFilamentRepository creates a FilamentRepository backed by the given pool.
+func NewFilamentRepository(pool *pgxpool.Pool) *FilamentRepository {
+	return &FilamentRepository{pool: pool}
+}
+
+// FilamentFilter holds query parameters for listing filament spools.
+type FilamentFilter struct {
+	Material string // filter by material_base name (case-insensitive)
+	Finish   string // filter by material_finish name (case-insensitive)
+	Color    string // filter by exact color_hex match
+	LowStock bool   // if true, filter for remaining_grams <= low_stock_threshold_grams
+	Limit    int
+	Offset   int
+}
+
+// spoolScanFields is the common SELECT column list for filament spools with JOINs.
+const spoolScanFields = `
+	s.id, s.name,
+	s.material_base_id,
+	COALESCE(mb.name, '') as material_base_name,
+	COALESCE(mb.density_g_cm3, 0) as material_base_density_g_cm3,
+	COALESCE(mb.extrusion_temp_min, NULL::int) as material_base_extrusion_temp_min,
+	COALESCE(mb.extrusion_temp_max, NULL::int) as material_base_extrusion_temp_max,
+	COALESCE(mb.bed_temp_min, NULL::int) as material_base_bed_temp_min,
+	COALESCE(mb.bed_temp_max, NULL::int) as material_base_bed_temp_max,
+	COALESCE(mb.created_at, s.created_at) as material_base_created_at,
+	COALESCE(mb.updated_at, s.created_at) as material_base_updated_at,
+	s.material_finish_id,
+	COALESCE(mf.name, '') as material_finish_name,
+	mf.description as material_finish_description,
+	COALESCE(mf.created_at, s.created_at) as material_finish_created_at,
+	COALESCE(mf.updated_at, s.created_at) as material_finish_updated_at,
+	s.material_modifier_id,
+	mm.name as material_modifier_name,
+	mm.description as material_modifier_description,
+	mm.created_at as material_modifier_created_at,
+	mm.updated_at as material_modifier_updated_at,
+	s.color_hex, s.brand, s.diameter_mm,
+	s.initial_grams, s.remaining_grams, s.spool_weight_grams,
+	s.cost_usd, s.low_stock_threshold_grams,
+	s.notes, s.barcode,
+	s.deleted_at, s.created_at, s.updated_at`
+
+const spoolFromJoins = `
+	FROM filament_spools s
+	LEFT JOIN material_bases mb ON s.material_base_id = mb.id
+	LEFT JOIN material_finishes mf ON s.material_finish_id = mf.id
+	LEFT JOIN material_modifiers mm ON s.material_modifier_id = mm.id`
+
+// scanSpoolWithJoins scans a full spool row including all JOINed tables.
+func scanSpoolWithJoins(row interface{ Scan(...interface{}) error }) (models.FilamentSpool, error) {
+	var s models.FilamentSpool
+	var mb models.MaterialBase
+	var mf models.MaterialFinish
+	var mfDesc *string
+	var modifierID *int
+	var modName, modDesc *string
+	var modCreatedAt, modUpdatedAt *time.Time
+
+	err := row.Scan(
+		&s.ID, &s.Name,
+		&s.MaterialBaseID,
+		&mb.Name, &mb.DensityGCm3,
+		&mb.ExtrusionTempMin, &mb.ExtrusionTempMax,
+		&mb.BedTempMin, &mb.BedTempMax,
+		&mb.CreatedAt, &mb.UpdatedAt,
+		&s.MaterialFinishID,
+		&mf.Name, &mfDesc,
+		&mf.CreatedAt, &mf.UpdatedAt,
+		&modifierID,
+		&modName, &modDesc,
+		&modCreatedAt, &modUpdatedAt,
+		&s.ColorHex, &s.Brand, &s.DiameterMM,
+		&s.InitialGrams, &s.RemainingGrams, &s.SpoolWeightGrams,
+		&s.CostUSD, &s.LowStockThresholdGrams,
+		&s.Notes, &s.Barcode,
+		&s.DeletedAt, &s.CreatedAt, &s.UpdatedAt,
+	)
+	if err != nil {
+		return s, err
+	}
+
+	mb.ID = s.MaterialBaseID
+	s.MaterialBase = &mb
+
+	mf.ID = s.MaterialFinishID
+	if mfDesc != nil {
+		mf.Description = mfDesc
+	}
+	s.MaterialFinish = &mf
+
+	s.MaterialModifierID = modifierID
+	if modifierID != nil && modName != nil {
+		mm := models.MaterialModifier{
+			ID:   *modifierID,
+			Name: *modName,
+		}
+		if modDesc != nil {
+			mm.Description = modDesc
+		}
+		if modCreatedAt != nil {
+			mm.CreatedAt = *modCreatedAt
+		}
+		if modUpdatedAt != nil {
+			mm.UpdatedAt = *modUpdatedAt
+		}
+		s.MaterialModifier = &mm
+	}
+
+	return s, nil
+}
+
+// GetAll returns filament spools matching the given filters, with pagination.
+// Returns results, total matching count, and any error.
+func (r *FilamentRepository) GetAll(ctx context.Context, filter FilamentFilter) ([]models.FilamentSpool, int, error) {
+	conditions := []string{"s.deleted_at IS NULL"}
+	args := []interface{}{}
+	argIdx := 1
+
+	if filter.Material != "" {
+		conditions = append(conditions, fmt.Sprintf("LOWER(mb.name) = LOWER($%d)", argIdx))
+		args = append(args, filter.Material)
+		argIdx++
+	}
+	if filter.Finish != "" {
+		conditions = append(conditions, fmt.Sprintf("LOWER(mf.name) = LOWER($%d)", argIdx))
+		args = append(args, filter.Finish)
+		argIdx++
+	}
+	if filter.Color != "" {
+		conditions = append(conditions, fmt.Sprintf("s.color_hex = $%d", argIdx))
+		args = append(args, filter.Color)
+		argIdx++
+	}
+	if filter.LowStock {
+		conditions = append(conditions, "s.remaining_grams <= s.low_stock_threshold_grams")
+	}
+
+	whereClause := ""
+	if len(conditions) > 0 {
+		whereClause = "WHERE " + strings.Join(conditions, " AND ")
+	}
+
+	// Count total.
+	var total int
+	countQuery := "SELECT COUNT(*) " + spoolFromJoins + " " + whereClause
+	if err := r.pool.QueryRow(ctx, countQuery, args...).Scan(&total); err != nil {
+		return nil, 0, err
+	}
+
+	// Query with pagination.
+	dataQuery := "SELECT " + spoolScanFields + " " + spoolFromJoins + " " +
+		whereClause +
+		" ORDER BY s.name ASC" +
+		fmt.Sprintf(" LIMIT $%d OFFSET $%d", argIdx, argIdx+1)
+
+	dataArgs := make([]interface{}, len(args))
+	copy(dataArgs, args)
+	dataArgs = append(dataArgs, filter.Limit, filter.Offset)
+
+	rows, err := r.pool.Query(ctx, dataQuery, dataArgs...)
+	if err != nil {
+		return nil, 0, err
+	}
+	defer rows.Close()
+
+	var spools []models.FilamentSpool
+	for rows.Next() {
+		s, err := scanSpoolWithJoins(rows)
+		if err != nil {
+			return nil, 0, err
+		}
+		spools = append(spools, s)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, 0, err
+	}
+	if spools == nil {
+		spools = []models.FilamentSpool{}
+	}
+
+	return spools, total, nil
+}
+
+// GetByID returns a single filament spool by ID with JOINed data.
+// Returns nil if not found or soft-deleted.
+func (r *FilamentRepository) GetByID(ctx context.Context, id int) (*models.FilamentSpool, error) {
+	query := "SELECT " + spoolScanFields + " " + spoolFromJoins +
+		" WHERE s.id = $1 AND s.deleted_at IS NULL"
+
+	row := r.pool.QueryRow(ctx, query, id)
+	s, err := scanSpoolWithJoins(row)
+	if err != nil {
+		return nil, err
+	}
+	return &s, nil
+}
+
+// Create inserts a new filament spool and returns the created spool with JOINed data.
+func (r *FilamentRepository) Create(ctx context.Context, spool *models.FilamentSpool) (*models.FilamentSpool, error) {
+	var id int
+	err := r.pool.QueryRow(ctx, `
+		INSERT INTO filament_spools (
+			name, material_base_id, material_finish_id, material_modifier_id,
+			color_hex, brand, diameter_mm, initial_grams, remaining_grams,
+			spool_weight_grams, cost_usd, low_stock_threshold_grams,
+			notes, barcode
+		) VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14)
+		RETURNING id
+	`,
+		spool.Name, spool.MaterialBaseID, spool.MaterialFinishID, spool.MaterialModifierID,
+		spool.ColorHex, spool.Brand, spool.DiameterMM, spool.InitialGrams, spool.RemainingGrams,
+		spool.SpoolWeightGrams, spool.CostUSD, spool.LowStockThresholdGrams,
+		spool.Notes, spool.Barcode,
+	).Scan(&id)
+	if err != nil {
+		return nil, err
+	}
+
+	return r.GetByID(ctx, id)
+}
+
+// Update applies partial updates to an existing filament spool.
+// Only non-nil fields in the update map are applied.
+// Returns the updated spool.
+func (r *FilamentRepository) Update(ctx context.Context, id int, updates map[string]interface{}) (*models.FilamentSpool, error) {
+	if len(updates) == 0 {
+		return r.GetByID(ctx, id)
+	}
+
+	setClauses := []string{"updated_at = NOW()"}
+	args := []interface{}{}
+	argIdx := 1
+
+	for col, val := range updates {
+		setClauses = append(setClauses, fmt.Sprintf("%s = $%d", col, argIdx))
+		args = append(args, val)
+		argIdx++
+	}
+
+	args = append(args, id)
+	query := fmt.Sprintf("UPDATE filament_spools SET %s WHERE id = $%d AND deleted_at IS NULL",
+		strings.Join(setClauses, ", "), argIdx)
+
+	result, err := r.pool.Exec(ctx, query, args...)
+	if err != nil {
+		return nil, err
+	}
+	if result.RowsAffected() == 0 {
+		return nil, nil // not found or deleted
+	}
+
+	return r.GetByID(ctx, id)
+}
+
+// SoftDelete marks a filament spool as deleted by setting deleted_at = NOW().
+// Returns true if a row was affected.
+func (r *FilamentRepository) SoftDelete(ctx context.Context, id int) (bool, error) {
+	result, err := r.pool.Exec(ctx, `
+		UPDATE filament_spools
+		SET deleted_at = NOW(), updated_at = NOW()
+		WHERE id = $1 AND deleted_at IS NULL
+	`, id)
+	if err != nil {
+		return false, err
+	}
+	return result.RowsAffected() > 0, nil
+}

backend/internal/repositories/material_repository.go

@@ -0,0 +1,54 @@
+// Package repositories provides data access logic backed by PostgreSQL via pgxpool.
+package repositories
+
+import (
+	"context"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// MaterialRepository handles database queries for material lookup tables.
+type MaterialRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewMaterialRepository creates a MaterialRepository backed by the given pool.
+func NewMaterialRepository(pool *pgxpool.Pool) *MaterialRepository {
+	return &MaterialRepository{pool: pool}
+}
+
+// GetAll returns all material bases ordered by name.
+func (r *MaterialRepository) GetAll(ctx context.Context) ([]models.MaterialBase, error) {
+	rows, err := r.pool.Query(ctx, `
+		SELECT id, name, density_g_cm3, extrusion_temp_min, extrusion_temp_max,
+		       bed_temp_min, bed_temp_max, created_at, updated_at
+		FROM material_bases
+		ORDER BY name
+	`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var materials []models.MaterialBase
+	for rows.Next() {
+		var m models.MaterialBase
+		if err := rows.Scan(
+			&m.ID, &m.Name, &m.DensityGCm3,
+			&m.ExtrusionTempMin, &m.ExtrusionTempMax,
+			&m.BedTempMin, &m.BedTempMax,
+			&m.CreatedAt, &m.UpdatedAt,
+		); err != nil {
+			return nil, err
+		}
+		materials = append(materials, m)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	if materials == nil {
+		materials = []models.MaterialBase{}
+	}
+	return materials, nil
+}

backend/internal/repositories/print_job_repository.go

@@ -0,0 +1,157 @@
+package repositories
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// PrintJobRepository handles database queries for print_jobs.
+type PrintJobRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewPrintJobRepository creates a PrintJobRepository backed by the given pool.
+func NewPrintJobRepository(pool *pgxpool.Pool) *PrintJobRepository {
+	return &PrintJobRepository{pool: pool}
+}
+
+// PrintJobFilter holds query parameters for listing print jobs.
+type PrintJobFilter struct {
+	Status    string // filter by job_status name (case-insensitive)
+	PrinterID *int   // filter by printer_id
+	Limit     int
+	Offset    int
+}
+
+// scanPrintJobWithJoins scans a print_job row with JOINed tables.
+func (r *PrintJobRepository) scanPrintJobWithJoins(row interface{ Scan(...interface{}) error }) (models.PrintJob, error) {
+	var pj models.PrintJob
+	var js models.JobStatus
+
+	err := row.Scan(
+		&pj.ID, &pj.PrinterID, &pj.FilamentSpoolID,
+		&pj.JobName, &pj.FileName,
+		&pj.JobStatusID,
+		&pj.StartedAt, &pj.CompletedAt,
+		&pj.DurationSeconds, &pj.EstimatedDurationSeconds,
+		&pj.TotalMMExtruded, &pj.TotalGramsUsed, &pj.TotalCostUSD,
+		&pj.Notes,
+		&pj.DeletedAt, &pj.CreatedAt, &pj.UpdatedAt,
+		&js.ID, &js.Name,
+		&js.CreatedAt, &js.UpdatedAt,
+	)
+	if err != nil {
+		return pj, err
+	}
+
+	pj.JobStatus = &js
+	return pj, nil
+}
+
+// GetAll returns print jobs matching the given filters, with pagination.
+func (r *PrintJobRepository) GetAll(ctx context.Context, filter PrintJobFilter) ([]models.PrintJob, int, error) {
+	conditions := []string{"pj.deleted_at IS NULL"}
+	args := []interface{}{}
+	argIdx := 1
+
+	if filter.Status != "" {
+		conditions = append(conditions, fmt.Sprintf("LOWER(js.name) = LOWER($%d)", argIdx))
+		args = append(args, filter.Status)
+		argIdx++
+	}
+	if filter.PrinterID != nil {
+		conditions = append(conditions, fmt.Sprintf("pj.printer_id = $%d", argIdx))
+		args = append(args, *filter.PrinterID)
+		argIdx++
+	}
+
+	whereClause := ""
+	if len(conditions) > 0 {
+		whereClause = "WHERE " + strings.Join(conditions, " AND ")
+	}
+
+	// Count.
+	var total int
+	countQuery := `SELECT COUNT(*)
+		FROM print_jobs pj
+		LEFT JOIN job_statuses js ON pj.job_status_id = js.id
+	` + " " + whereClause
+	if err := r.pool.QueryRow(ctx, countQuery, args...).Scan(&total); err != nil {
+		return nil, 0, err
+	}
+
+	// Query with pagination.
+	dataQuery := `SELECT
+		pj.id, pj.printer_id, pj.filament_spool_id,
+		pj.job_name, pj.file_name,
+		pj.job_status_id,
+		pj.started_at, pj.completed_at,
+		pj.duration_seconds, pj.estimated_duration_seconds,
+		pj.total_mm_extruded, pj.total_grams_used, pj.total_cost_usd,
+		pj.notes,
+		pj.deleted_at, pj.created_at, pj.updated_at,
+		js.id, js.name,
+		js.created_at, js.updated_at
+	FROM print_jobs pj
+	LEFT JOIN job_statuses js ON pj.job_status_id = js.id
+	` + whereClause +
+		" ORDER BY pj.created_at DESC" +
+		fmt.Sprintf(" LIMIT $%d OFFSET $%d", argIdx, argIdx+1)
+
+	dataArgs := make([]interface{}, len(args))
+	copy(dataArgs, args)
+	dataArgs = append(dataArgs, filter.Limit, filter.Offset)
+
+	rows, err := r.pool.Query(ctx, dataQuery, dataArgs...)
+	if err != nil {
+		return nil, 0, err
+	}
+	defer rows.Close()
+
+	var jobs []models.PrintJob
+	for rows.Next() {
+		pj, err := r.scanPrintJobWithJoins(rows)
+		if err != nil {
+			return nil, 0, err
+		}
+		jobs = append(jobs, pj)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, 0, err
+	}
+	if jobs == nil {
+		jobs = []models.PrintJob{}
+	}
+
+	return jobs, total, nil
+}
+
+// GetByID returns a single print job by ID with JOINed job_status.
+func (r *PrintJobRepository) GetByID(ctx context.Context, id int) (*models.PrintJob, error) {
+	row := r.pool.QueryRow(ctx, `
+		SELECT
+			pj.id, pj.printer_id, pj.filament_spool_id,
+			pj.job_name, pj.file_name,
+			pj.job_status_id,
+			pj.started_at, pj.completed_at,
+			pj.duration_seconds, pj.estimated_duration_seconds,
+			pj.total_mm_extruded, pj.total_grams_used, pj.total_cost_usd,
+			pj.notes,
+			pj.deleted_at, pj.created_at, pj.updated_at,
+			js.id, js.name,
+			js.created_at, js.updated_at
+		FROM print_jobs pj
+		LEFT JOIN job_statuses js ON pj.job_status_id = js.id
+		WHERE pj.id = $1 AND pj.deleted_at IS NULL
+	`, id)
+
+	pj, err := r.scanPrintJobWithJoins(row)
+	if err != nil {
+		return nil, err
+	}
+	return &pj, nil
+}

backend/internal/repositories/printer_repository.go

@@ -0,0 +1,78 @@
+package repositories
+
+import (
+	"context"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// PrinterRepository handles database queries for printers.
+type PrinterRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewPrinterRepository creates a PrinterRepository backed by the given pool.
+func NewPrinterRepository(pool *pgxpool.Pool) *PrinterRepository {
+	return &PrinterRepository{pool: pool}
+}
+
+// scanPrinterWithType scans a printer row with JOINed printer_type.
+func (r *PrinterRepository) scanPrinterWithType(row interface{ Scan(...interface{}) error }) (models.Printer, error) {
+	var p models.Printer
+	var pt models.PrinterType
+
+	err := row.Scan(
+		&p.ID, &p.Name, &p.PrinterTypeID,
+		&p.Manufacturer, &p.Model,
+		&p.MoonrakerURL, &p.MoonrakerAPIKey,
+		&p.MQTTBrokerHost, &p.MQTTTopicPrefix,
+		&p.MQTTTLSEnabled, &p.IsActive,
+		&p.CreatedAt, &p.UpdatedAt,
+		&pt.ID, &pt.Name,
+		&pt.CreatedAt, &pt.UpdatedAt,
+	)
+	if err != nil {
+		return p, err
+	}
+
+	p.PrinterType = &pt
+	return p, nil
+}
+
+// GetAll returns all printers joined with their printer_type, ordered by name.
+func (r *PrinterRepository) GetAll(ctx context.Context) ([]models.Printer, error) {
+	rows, err := r.pool.Query(ctx, `
+		SELECT p.id, p.name, p.printer_type_id,
+		       p.manufacturer, p.model,
+		       p.moonraker_url, p.moonraker_api_key,
+		       p.mqtt_broker_host, p.mqtt_topic_prefix,
+		       p.mqtt_tls_enabled, p.is_active,
+		       p.created_at, p.updated_at,
+		       pt.id, pt.name,
+		       pt.created_at, pt.updated_at
+		FROM printers p
+		JOIN printer_types pt ON p.printer_type_id = pt.id
+		ORDER BY p.name
+	`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var printers []models.Printer
+	for rows.Next() {
+		p, err := r.scanPrinterWithType(rows)
+		if err != nil {
+			return nil, err
+		}
+		printers = append(printers, p)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	if printers == nil {
+		printers = []models.Printer{}
+	}
+	return printers, nil
+}

backend/internal/repositories/usage_log_repository.go

@@ -0,0 +1,96 @@
+package repositories
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// UsageLogRepository handles database queries for usage_logs.
+type UsageLogRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewUsageLogRepository creates a UsageLogRepository backed by the given pool.
+func NewUsageLogRepository(pool *pgxpool.Pool) *UsageLogRepository {
+	return &UsageLogRepository{pool: pool}
+}
+
+// UsageLogFilter holds query parameters for listing usage logs.
+type UsageLogFilter struct {
+	SpoolID *int // filter by filament_spool_id
+	JobID   *int // filter by print_job_id
+	Limit   int
+	Offset  int
+}
+
+// GetAll returns usage logs matching the given filters, with pagination.
+func (r *UsageLogRepository) GetAll(ctx context.Context, filter UsageLogFilter) ([]models.UsageLog, int, error) {
+	conditions := []string{"1=1"}
+	args := []interface{}{}
+	argIdx := 1
+
+	if filter.SpoolID != nil {
+		conditions = append(conditions, fmt.Sprintf("ul.filament_spool_id = $%d", argIdx))
+		args = append(args, *filter.SpoolID)
+		argIdx++
+	}
+	if filter.JobID != nil {
+		conditions = append(conditions, fmt.Sprintf("ul.print_job_id = $%d", argIdx))
+		args = append(args, *filter.JobID)
+		argIdx++
+	}
+
+	whereClause := "WHERE " + fmt.Sprintf("%s", conditions[0])
+	for _, c := range conditions[1:] {
+		whereClause += " AND " + c
+	}
+
+	// Count.
+	var total int
+	countQuery := "SELECT COUNT(*) FROM usage_logs ul " + whereClause
+	if err := r.pool.QueryRow(ctx, countQuery, args...).Scan(&total); err != nil {
+		return nil, 0, err
+	}
+
+	// Query with pagination.
+	dataQuery := `SELECT id, print_job_id, filament_spool_id, mm_extruded,
+	       grams_used, cost_usd, logged_at, created_at
+	FROM usage_logs ul
+	` + whereClause +
+		" ORDER BY ul.logged_at DESC" +
+		fmt.Sprintf(" LIMIT $%d OFFSET $%d", argIdx, argIdx+1)
+
+	dataArgs := make([]interface{}, len(args))
+	copy(dataArgs, args)
+	dataArgs = append(dataArgs, filter.Limit, filter.Offset)
+
+	rows, err := r.pool.Query(ctx, dataQuery, dataArgs...)
+	if err != nil {
+		return nil, 0, err
+	}
+	defer rows.Close()
+
+	var logs []models.UsageLog
+	for rows.Next() {
+		var l models.UsageLog
+		if err := rows.Scan(
+			&l.ID, &l.PrintJobID, &l.FilamentSpoolID,
+			&l.MMExtruded, &l.GramsUsed, &l.CostUSD,
+			&l.LoggedAt, &l.CreatedAt,
+		); err != nil {
+			return nil, 0, err
+		}
+		logs = append(logs, l)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, 0, err
+	}
+	if logs == nil {
+		logs = []models.UsageLog{}
+	}
+
+	return logs, total, nil
+}

backend/internal/router/router.go

@@ -1,19 +1,21 @@
 package router
 
 import (
-	"log/slog"
 	"net/http"
 	"time"
 
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/config"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/handlers"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/services"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 // New creates and configures a Chi router with all middleware and handlers mounted.
-func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
+func New(cfg *config.Config, dbPool *pgxpool.Pool, sseBC *sse.Broadcaster) chi.Router {
 	r := chi.NewRouter()
 
 	// Middleware
@@ -21,7 +23,7 @@ func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
 	r.Use(middleware.RealIP)
 	r.Use(middleware.Logger)
 	r.Use(middleware.Recoverer)
-	r.Use(middleware.Timeout(60 * time.Second))
+	// Timeout middleware is applied per-route below to exclude SSE
 
 	// CORS
 	r.Use(func(next http.Handler) http.Handler {
@@ -37,9 +39,52 @@ func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
 		})
 	})
 
-	// Health check
+	// Health check (with timeout)
 	healthHandler := handlers.NewHealthHandler(dbPool)
-	r.Get("/health", healthHandler.ServeHTTP)
+	r.With(middleware.Timeout(30 * time.Second)).Get("/health", healthHandler.ServeHTTP)
+
+	// ── Repositories ──────────────────────────────────────────────────────
+	materialRepo := repositories.NewMaterialRepository(dbPool)
+	filamentRepo := repositories.NewFilamentRepository(dbPool)
+	printerRepo := repositories.NewPrinterRepository(dbPool)
+	printJobRepo := repositories.NewPrintJobRepository(dbPool)
+	usageLogRepo := repositories.NewUsageLogRepository(dbPool)
+
+	// ── Services ──────────────────────────────────────────────────────────
+	filamentService := services.NewFilamentService(filamentRepo)
+	printerService := services.NewPrinterService(printerRepo)
+	printJobService := services.NewPrintJobService(printJobRepo)
+
+	// ── Handlers ──────────────────────────────────────────────────────────
+	materialHandler := handlers.NewMaterialHandler(materialRepo)
+	filamentHandler := handlers.NewFilamentHandler(filamentService)
+	printerHandler := handlers.NewPrinterHandler(printerService)
+	printJobHandler := handlers.NewPrintJobHandler(printJobService)
+	usageLogHandler := handlers.NewUsageLogHandler(usageLogRepo)
+
+	// ── API Routes (with timeout) ─────────────────────────────────────────
+	r.Route("/api", func(r chi.Router) {
+		r.Use(middleware.Timeout(60 * time.Second))
+		r.Get("/materials", materialHandler.List)
+
+		r.Route("/filaments", func(r chi.Router) {
+			r.Get("/", filamentHandler.List)
+			r.Post("/", filamentHandler.Create)
+			r.Route("/{id}", func(r chi.Router) {
+				r.Get("/", filamentHandler.Get)
+				r.Put("/", filamentHandler.Update)
+				r.Delete("/", filamentHandler.Delete)
+			})
+		})
+
+		r.Get("/printers", printerHandler.List)
+		r.Get("/print-jobs", printJobHandler.List)
+		r.Get("/usage-logs", usageLogHandler.List)
+
+		// SSE Events stream
+		sseHandler := sse.NewHandler(sseBC)
+		r.Get("/events", sseHandler.ServeHTTP)
+	})
 
 	return r
 }

backend/internal/services/.gitkeep

@@ -1 +0,0 @@
-# Services

backend/internal/services/services.go

@@ -0,0 +1,82 @@
+// Package services contains business logic and application services.
+package services
+
+import (
+	"context"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+)
+
+// FilamentService wraps FilamentRepository with business logic and validation.
+type FilamentService struct {
+	repo *repositories.FilamentRepository
+}
+
+// NewFilamentService creates a FilamentService backed by the given repository.
+func NewFilamentService(repo *repositories.FilamentRepository) *FilamentService {
+	return &FilamentService{repo: repo}
+}
+
+// List returns paginated filament spools filtered by the given criteria.
+func (s *FilamentService) List(ctx context.Context, filter repositories.FilamentFilter) ([]models.FilamentSpool, int, error) {
+	return s.repo.GetAll(ctx, filter)
+}
+
+// GetByID returns a single filament spool by ID.
+func (s *FilamentService) GetByID(ctx context.Context, id int) (*models.FilamentSpool, error) {
+	return s.repo.GetByID(ctx, id)
+}
+
+// Create validates and creates a new filament spool.
+func (s *FilamentService) Create(ctx context.Context, spool *models.FilamentSpool) (*models.FilamentSpool, error) {
+	if err := validateFilamentSpool(spool); err != nil {
+		return nil, err
+	}
+	return s.repo.Create(ctx, spool)
+}
+
+// Update applies partial updates to a filament spool after validation.
+func (s *FilamentService) Update(ctx context.Context, id int, updates map[string]interface{}) (*models.FilamentSpool, error) {
+	return s.repo.Update(ctx, id, updates)
+}
+
+// SoftDelete marks a filament spool as deleted.
+func (s *FilamentService) SoftDelete(ctx context.Context, id int) (bool, error) {
+	return s.repo.SoftDelete(ctx, id)
+}
+
+// PrinterService wraps PrinterRepository.
+type PrinterService struct {
+	repo *repositories.PrinterRepository
+}
+
+// NewPrinterService creates a PrinterService backed by the given repository.
+func NewPrinterService(repo *repositories.PrinterRepository) *PrinterService {
+	return &PrinterService{repo: repo}
+}
+
+// List returns all printers.
+func (s *PrinterService) List(ctx context.Context) ([]models.Printer, error) {
+	return s.repo.GetAll(ctx)
+}
+
+// PrintJobService wraps PrintJobRepository.
+type PrintJobService struct {
+	repo *repositories.PrintJobRepository
+}
+
+// NewPrintJobService creates a PrintJobService backed by the given repository.
+func NewPrintJobService(repo *repositories.PrintJobRepository) *PrintJobService {
+	return &PrintJobService{repo: repo}
+}
+
+// List returns paginated print jobs filtered by the given criteria.
+func (s *PrintJobService) List(ctx context.Context, filter repositories.PrintJobFilter) ([]models.PrintJob, int, error) {
+	return s.repo.GetAll(ctx, filter)
+}
+
+// GetByID returns a single print job by ID.
+func (s *PrintJobService) GetByID(ctx context.Context, id int) (*models.PrintJob, error) {
+	return s.repo.GetByID(ctx, id)
+}

backend/internal/services/validation.go

@@ -0,0 +1,74 @@
+package services
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/dtos"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+)
+
+// colorHexPattern validates hex color strings like #FF0000 or #ff0000.
+var colorHexPattern = regexp.MustCompile(`^#[0-9A-Fa-f]{6}$`)
+
+// validateFilamentSpool performs validation on a FilamentSpool entity.
+// Returns a descriptive error on failure.
+func validateFilamentSpool(s *models.FilamentSpool) error {
+	if s.Name == "" {
+		return errors.New("name is required")
+	}
+	if s.MaterialBaseID <= 0 {
+		return errors.New("material_base_id is required")
+	}
+	if s.MaterialFinishID <= 0 {
+		return errors.New("material_finish_id is required")
+	}
+	if !colorHexPattern.MatchString(s.ColorHex) {
+		return fmt.Errorf("color_hex must be a valid hex color (e.g., #FF0000)")
+	}
+	if s.InitialGrams <= 0 {
+		return errors.New("initial_grams must be greater than 0")
+	}
+	if s.RemainingGrams < 0 {
+		return errors.New("remaining_grams must be >= 0")
+	}
+	return nil
+}
+
+// ValidateCreateFilamentRequest validates a creation DTO.
+func ValidateCreateFilamentRequest(req dtos.CreateFilamentRequest) error {
+	if req.Name == "" {
+		return errors.New("name is required")
+	}
+	if req.MaterialBaseID <= 0 {
+		return errors.New("material_base_id is required")
+	}
+	if req.MaterialFinishID <= 0 {
+		return errors.New("material_finish_id is required")
+	}
+	if !colorHexPattern.MatchString(req.ColorHex) {
+		return fmt.Errorf("color_hex must be a valid hex color (e.g., #FF0000)")
+	}
+	if req.InitialGrams <= 0 {
+		return errors.New("initial_grams must be greater than 0")
+	}
+	if req.RemainingGrams < 0 {
+		return errors.New("remaining_grams must be >= 0")
+	}
+	return nil
+}
+
+// ValidateUpdateFilamentRequest validates partial update fields.
+func ValidateUpdateFilamentRequest(req dtos.UpdateFilamentRequest) error {
+	if req.ColorHex != nil && !colorHexPattern.MatchString(*req.ColorHex) {
+		return fmt.Errorf("color_hex must be a valid hex color (e.g., #FF0000)")
+	}
+	if req.InitialGrams != nil && *req.InitialGrams <= 0 {
+		return errors.New("initial_grams must be greater than 0")
+	}
+	if req.RemainingGrams != nil && *req.RemainingGrams < 0 {
+		return errors.New("remaining_grams must be >= 0")
+	}
+	return nil
+}

backend/internal/sse/broadcaster.go

@@ -0,0 +1,133 @@
+package sse
+
+import (
+	"log/slog"
+	"sync"
+)
+
+// client represents a single SSE subscriber — identified by its send channel.
+type client struct {
+	ch chan string
+}
+
+// Broadcaster receives Events on its input channel and fans them out to every
+// connected client. Subscribe adds a new client; Unsubscribe removes one.
+// Start must be called before the broadcaster accepts events.
+type Broadcaster struct {
+	input       chan Event
+	subscribe   chan client
+	unsubscribe chan client
+	clients     map[chan string]struct{}
+	done        chan struct{}
+	once        sync.Once
+}
+
+// NewBroadcaster creates a Broadcaster. bufSize controls the buffer depth for
+// the input channel as well as for each per-client outbound channel.
+func NewBroadcaster(bufSize int) *Broadcaster {
+	if bufSize <= 0 {
+		bufSize = 64
+	}
+	return &Broadcaster{
+		input:       make(chan Event, bufSize),
+		subscribe:   make(chan client),
+		unsubscribe: make(chan client),
+		clients:     make(map[chan string]struct{}),
+		done:        make(chan struct{}),
+	}
+}
+
+// Publish pushes an event into the broadcaster. Safe for concurrent use.
+func (b *Broadcaster) Publish(ev Event) {
+	select {
+	case b.input <- ev:
+	case <-b.done:
+		// Silently drop during shutdown.
+	}
+}
+
+// Start launches the broadcaster's fan-out loop in a goroutine.
+// It must be called before Publish is used.
+func (b *Broadcaster) Start() {
+	go b.loop()
+}
+
+// Stop terminates the fan-out loop and closes all client channels.
+// It is safe to call multiple times.
+func (b *Broadcaster) Stop() {
+	b.once.Do(func() {
+		close(b.done)
+	})
+}
+
+// Subscribe returns a new client channel that receives SSE-formatted strings.
+func (b *Broadcaster) Subscribe() chan string {
+	c := client{ch: make(chan string, 64)}
+	select {
+	case b.subscribe <- c:
+	case <-b.done:
+		// Broadcaster already stopped — return a closed chan so the handler
+		// can bail out quickly.
+		ch := make(chan string)
+		close(ch)
+		return ch
+	}
+	return c.ch
+}
+
+// Unsubscribe removes a client channel and closes it.
+func (b *Broadcaster) Unsubscribe(ch chan string) {
+	c := client{ch: ch}
+	select {
+	case b.unsubscribe <- c:
+	case <-b.done:
+		// Already shutting down — channels will be cleaned up by Stop.
+	}
+}
+
+// loop is the core fan-out goroutine.
+func (b *Broadcaster) loop() {
+	for {
+		select {
+		case ev := <-b.input:
+			sse := ev.toSSE()
+			for ch := range b.clients {
+				// Non-blocking send — slow clients are dropped.
+				select {
+				case ch <- sse:
+				default:
+					slog.Warn("sse broadcaster: dropping event for slow client", "type", ev.Type)
+				}
+			}
+
+		case c := <-b.subscribe:
+			b.clients[c.ch] = struct{}{}
+			slog.Debug("sse broadcaster: client connected", "total_clients", len(b.clients))
+
+		case c := <-b.unsubscribe:
+			if _, ok := b.clients[c.ch]; ok {
+				delete(b.clients, c.ch)
+				close(c.ch)
+				slog.Debug("sse broadcaster: client disconnected", "total_clients", len(b.clients))
+			}
+
+		case <-b.done:
+			// Drain remaining events in input before shutting down.
+			for ev := range b.input {
+				sse := ev.toSSE()
+				for ch := range b.clients {
+					select {
+					case ch <- sse:
+					default:
+					}
+				}
+			}
+			// Close all remaining client channels.
+			for ch := range b.clients {
+				close(ch)
+			}
+			b.clients = nil
+			return
+		}
+	}
+}

backend/internal/sse/events.go

@@ -0,0 +1,92 @@
+// Package sse provides Server-Sent Events infrastructure for real-time updates.
+// Includes event types, a central broadcaster, and an HTTP handler.
+package sse
+
+import (
+	"encoding/json"
+	"time"
+)
+
+// EventType identifies the category of an SSE event.
+type EventType string
+
+const (
+	EventPrinterStatus  EventType = "printer.status"
+	EventJobStarted     EventType = "job.started"
+	EventJobCompleted   EventType = "job.completed"
+	EventFilamentLow    EventType = "filament.low"
+)
+
+// Event is a JSON-serializable SSE event pushed through the broadcaster.
+type Event struct {
+	Type      EventType       `json:"type"`
+	Payload   json.RawMessage `json:"payload"`
+	Timestamp time.Time       `json:"timestamp"`
+}
+
+// PrinterStatusPayload carries printer online/offline/printing state.
+type PrinterStatusPayload struct {
+	PrinterID   int    `json:"printer_id"`
+	PrinterName string `json:"printer_name"`
+	Status      string `json:"status"` // "online", "offline", "printing"
+}
+
+// JobStartedPayload carries initial print job info.
+type JobStartedPayload struct {
+	JobID      int    `json:"job_id"`
+	JobName    string `json:"job_name"`
+	PrinterID  int    `json:"printer_id"`
+	SpoolID    *int   `json:"spool_id,omitempty"`
+}
+
+// JobCompletedPayload carries final print job data including usage.
+type JobCompletedPayload struct {
+	JobID           int     `json:"job_id"`
+	JobName         string  `json:"job_name"`
+	PrinterID       int     `json:"printer_id"`
+	DurationSeconds *int    `json:"duration_seconds,omitempty"`
+	TotalGramsUsed  *float64 `json:"total_grams_used,omitempty"`
+	TotalCostUSD    *float64 `json:"total_cost_usd,omitempty"`
+}
+
+// FilamentLowPayload alerts that a spool is below its threshold.
+type FilamentLowPayload struct {
+	SpoolID       int    `json:"spool_id"`
+	SpoolName     string `json:"spool_name"`
+	RemainingGrams int   `json:"remaining_grams"`
+	ThresholdGrams int   `json:"threshold_grams"`
+}
+
+// NewEvent creates an Event with the current timestamp from a typed payload.
+func NewEvent(eventType EventType, payload any) (Event, error) {
+	raw, err := json.Marshal(payload)
+	if err != nil {
+		return Event{}, err
+	}
+	return Event{
+		Type:      eventType,
+		Payload:   raw,
+		Timestamp: time.Now().UTC(),
+	}, nil
+}
+
+// MustEvent creates an Event and panics on marshal failure (for use with
+// known-good payloads in tests and internal wiring).
+func MustEvent(eventType EventType, payload any) Event {
+	ev, err := NewEvent(eventType, payload)
+	if err != nil {
+		panic("sse.MustEvent: failed to marshal payload: " + err.Error())
+	}
+	return ev
+}
+
+// toSSE formats this Event as a standard SSE message string ready to be
+// written to a response writer. The format is:
+//
+//	event: <type>
+//	data: <json>
+//
+func (e Event) toSSE() string {
+	data, _ := json.Marshal(e)
+	return "event: " + string(e.Type) + "\n" + "data: " + string(data) + "\n\n"
+}

backend/internal/sse/handler.go

@@ -0,0 +1,59 @@
+package sse
+
+import (
+	"net/http"
+)
+
+// Handler is the HTTP handler for the GET /api/events SSE stream.
+// It registers a client with the broadcaster, streams events as they arrive,
+// and unregisters on disconnect.
+type Handler struct {
+	bc *Broadcaster
+}
+
+// NewHandler creates a Handler backed by the given Broadcaster.
+func NewHandler(bc *Broadcaster) *Handler {
+	return &Handler{bc: bc}
+}
+
+// ServeHTTP implements the SSE streaming endpoint.
+// Flusher is required; clients that do not support flushing receive a 501.
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	flusher, ok := w.(http.Flusher)
+	if !ok {
+		http.Error(w, "streaming not supported", http.StatusNotImplemented)
+		return
+	}
+
+	// SSE-specific headers
+	w.Header().Set("Content-Type", "text/event-stream")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Connection", "keep-alive")
+	w.Header().Set("X-Accel-Buffering", "no") // Disable nginx buffering
+
+	// Write headers immediately
+	flusher.Flush()
+
+	// Subscribe to the broadcaster
+	ch := h.bc.Subscribe()
+	defer h.bc.Unsubscribe(ch)
+
+	// Use request context for cancellation when the client disconnects.
+	ctx := r.Context()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case msg, ok := <-ch:
+			if !ok {
+				return
+			}
+			_, err := w.Write([]byte(msg))
+			if err != nil {
+				return
+			}
+			flusher.Flush()
+		}
+	}
+}

backend/internal/workers/moonraker_poller.go

@@ -0,0 +1,321 @@
+// Package workers provides background goroutines for printer telemetry.
+package workers
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"strconv"
+	"time"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/clients"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// MoonrakerPollerConfig controls the background polling behaviour.
+type MoonrakerPollerConfig struct {
+	PollInterval   time.Duration
+	RequestTimeout time.Duration
+}
+
+// DefaultMoonrakerPollerConfig returns sensible defaults.
+func DefaultMoonrakerPollerConfig() MoonrakerPollerConfig {
+	return MoonrakerPollerConfig{
+		PollInterval:   30 * time.Second,
+		RequestTimeout: 10 * time.Second,
+	}
+}
+
+// MoonrakerPoller periodically polls Moonraker printers for status and usage.
+type MoonrakerPoller struct {
+	cfg         MoonrakerPollerConfig
+	client      *clients.MoonrakerClient
+	printerRepo *repositories.PrinterRepository
+	jobRepo     *repositories.PrintJobRepository
+	usageRepo   *repositories.UsageLogRepository
+	sseBC       *sse.Broadcaster
+	pool        *pgxpool.Pool
+	stop        chan struct{}
+}
+
+// NewMoonrakerPoller creates a poller. It uses the pool directly for
+// transaction-scoped writes that the repository layer cannot span.
+func NewMoonrakerPoller(
+	cfg MoonrakerPollerConfig,
+	pool *pgxpool.Pool,
+	printerRepo *repositories.PrinterRepository,
+	jobRepo *repositories.PrintJobRepository,
+	usageRepo *repositories.UsageLogRepository,
+	sseBC *sse.Broadcaster,
+) *MoonrakerPoller {
+	return &MoonrakerPoller{
+		cfg:         cfg,
+		client:      clients.NewMoonrakerClient(cfg.RequestTimeout),
+		printerRepo: printerRepo,
+		jobRepo:     jobRepo,
+		usageRepo:   usageRepo,
+		sseBC:       sseBC,
+		pool:        pool,
+		stop:        make(chan struct{}),
+	}
+}
+
+// Start begins the polling loop in a goroutine.
+func (p *MoonrakerPoller) Start() {
+	go p.loop()
+}
+
+// Stop signals the loop to exit.
+func (p *MoonrakerPoller) Stop() {
+	close(p.stop)
+}
+
+func (p *MoonrakerPoller) loop() {
+	ticker := time.NewTicker(p.cfg.PollInterval)
+	defer ticker.Stop()
+
+	// Immediate first tick.
+	p.pollCycle()
+
+	for {
+		select {
+		case <-ticker.C:
+			p.pollCycle()
+		case <-p.stop:
+			slog.Info("moonraker poller stopped")
+			return
+		}
+	}
+}
+
+func (p *MoonrakerPoller) pollCycle() {
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	printers, err := p.printerRepo.GetAll(ctx)
+	if err != nil {
+		slog.Error("moonraker poller: failed to list printers", "error", err)
+		return
+	}
+
+	for _, printer := range printers {
+		if !printer.IsActive || printer.MoonrakerURL == nil || *printer.MoonrakerURL == "" {
+			continue
+		}
+
+		if err := p.pollPrinter(ctx, printer); err != nil {
+			slog.Warn("moonraker poller: poll failed",
+				"printer", printer.Name,
+				"error", err,
+			)
+		}
+	}
+}
+
+// pollPrinter performs a single Moonraker poll for a printer.
+func (p *MoonrakerPoller) pollPrinter(ctx context.Context, printer models.Printer) error {
+	host := *printer.MoonrakerURL
+	var apiKey string
+	if printer.MoonrakerAPIKey != nil {
+		apiKey = *printer.MoonrakerAPIKey
+	}
+
+	// Fetch printer info (status)
+	info, err := p.client.GetPrinterInfo(ctx, host, 80, apiKey)
+	if err != nil {
+		p.broadcastStatus(printer.ID, printer.Name, "offline")
+		return err
+	}
+
+	status := mapMoonrakerState(info.State)
+	p.broadcastStatus(printer.ID, printer.Name, status)
+
+	// Fetch print stats
+	stats, err := p.client.GetPrintStats(ctx, host, 80, apiKey)
+	if err != nil {
+		return fmt.Errorf("getPrintStats failed: %w", err)
+	}
+
+	if status == "printing" && stats.Filename != "" {
+		p.broadcastJobStarted(printer.ID, stats.Filename)
+	}
+
+	if isCompleteState(stats.State) && stats.FilamentUsedMm > 0 {
+		// Record usage
+		if err := p.recordUsage(ctx, printer, stats); err != nil {
+			slog.Error("moonraker poller: record usage failed",
+				"printer", printer.Name, "error", err)
+		} else {
+			p.broadcastJobCompleted(printer.ID, stats.Filename, stats.FilamentUsedMm)
+		}
+	}
+
+	return nil
+}
+
+func (p *MoonrakerPoller) recordUsage(ctx context.Context, printer models.Printer, stats *clients.MoonrakerPrintStats) error {
+	// Find active spool for printer — for now use the first active spool
+	// or fallback to the one referenced by the printer if available.
+	// In a real scenario we'd query AMS slots or fallback logic.
+	// Here we simply look for the most recently used spool in usage_logs.
+	var spoolID int
+	row := p.pool.QueryRow(ctx, `
+		SELECT filament_spool_id FROM usage_logs
+		WHERE print_job_id IN (
+			SELECT id FROM print_jobs WHERE printer_id = $1
+		)
+		ORDER BY logged_at DESC LIMIT 1
+	`, printer.ID)
+	_ = row.Scan(&spoolID)
+
+	if spoolID == 0 {
+		// No prior usage — skip recording (no known spool to deduct from)
+		slog.Warn("moonraker poller: no known spool for printer; skipping usage record",
+			"printer", printer.Name)
+		return nil
+	}
+
+	// Compute grams from mm extruded using defaults (1.75mm diameter, PLA density 1.24)
+	grams := calculateGrams(stats.FilamentUsedMm, 1.75, 1.24)
+
+	// Create a print job record
+	var jobID int
+	err := p.pool.QueryRow(ctx, `
+		INSERT INTO print_jobs (printer_id, filament_spool_id, job_name, file_name, job_status_id,
+			started_at, completed_at, duration_seconds, total_mm_extruded, total_grams_used)
+		VALUES ($1, $2, $3, $4, 4, $5, $6, $7, $8, $9)
+		RETURNING id
+	`, printer.ID, spoolID, stats.Filename, stats.Filename,
+		time.Now().Add(-time.Duration(stats.TotalDuration)*time.Second),
+		time.Now(),
+		int(stats.TotalDuration),
+		stats.FilamentUsedMm,
+		grams,
+	).Scan(&jobID)
+
+	if err != nil {
+		return fmt.Errorf("insert print_job failed: %w", err)
+	}
+
+	// Create usage_log
+	_, err = p.pool.Exec(ctx, `
+		INSERT INTO usage_logs (print_job_id, filament_spool_id, mm_extruded, grams_used, logged_at)
+		VALUES ($1, $2, $3, $4, NOW())
+	`, jobID, spoolID, stats.FilamentUsedMm, grams)
+
+	if err != nil {
+		return fmt.Errorf("insert usage_log failed: %w", err)
+	}
+
+	slog.Info("moonraker poller: recorded usage",
+		"printer", printer.Name,
+		"job", stats.Filename,
+		"mm", stats.FilamentUsedMm,
+		"grams", grams,
+	)
+	return nil
+}
+
+func (p *MoonrakerPoller) broadcastStatus(printerID int, name, status string) {
+	if p.sseBC == nil {
+		return
+	}
+	ev, err := sse.NewEvent(sse.EventPrinterStatus, sse.PrinterStatusPayload{
+		PrinterID:   printerID,
+		PrinterName: name,
+		Status:      status,
+	})
+	if err != nil {
+		return
+	}
+	p.sseBC.Publish(ev)
+}
+
+func (p *MoonrakerPoller) broadcastJobStarted(printerID int, jobName string) {
+	if p.sseBC == nil {
+		return
+	}
+	ev, err := sse.NewEvent(sse.EventJobStarted, sse.JobStartedPayload{
+		JobName:   jobName,
+		PrinterID: printerID,
+	})
+	if err != nil {
+		return
+	}
+	p.sseBC.Publish(ev)
+}
+
+func (p *MoonrakerPoller) broadcastJobCompleted(printerID int, jobName string, mmExtruded float64) {
+	if p.sseBC == nil {
+		return
+	}
+	grams := calculateGrams(mmExtruded, 1.75, 1.24)
+	gramsInt := int(grams)
+	ev, err := sse.NewEvent(sse.EventJobCompleted, sse.JobCompletedPayload{
+		JobName:        jobName,
+		PrinterID:      printerID,
+		TotalGramsUsed: &gramsInt,
+	})
+	if err != nil {
+		return
+	}
+	p.sseBC.Publish(ev)
+}
+
+func mapMoonrakerState(state string) string {
+	switch state {
+	case "printing":
+		return "printing"
+	case "paused":
+		return "paused"
+	case "complete", "standby", "cancelled":
+		return "idle"
+	case "error":
+		return "error"
+	default:
+		return "offline"
+	}
+}
+
+func isCompleteState(state string) bool {
+	return state == "complete" || state == "completed"
+}
+
+func calculateGrams(mmExtruded, diameterMm, densityGcm3 float64) float64 {
+	if mmExtruded <= 0 {
+		return 0
+	}
+	radiusCm := diameterMm / 2.0 / 10.0
+	crossSection := 3.141592653589793 * radiusCm * radiusCm
+	volumeCm3 := (mmExtruded / 10.0) * crossSection
+	return volumeCm3 * densityGcm3
+}
+
+// ---------------------------------------------------------------------------
+// Helper for port parsing (Moonraker URL may contain port)
+// ---------------------------------------------------------------------------
+
+func extractHostPort(rawURL string) (string, int) {
+	// Very simplistic: if rawURL contains ":" after a dot, parse host:port.
+	// Otherwise assume host only and return port 80.
+	if rawURL == "" {
+		return "", 80
+	}
+	for i := len(rawURL) - 1; i >= 0; i-- {
+		if rawURL[i] == ':' {
+			portStr := rawURL[i+1:]
+			port, err := strconv.Atoi(portStr)
+			if err == nil {
+				return rawURL[:i], port
+			}
+			break
+		}
+		if rawURL[i] == '/' {
+			break
+		}
+	}
+	return rawURL, 80
+}

backend/internal/workers/mqtt_subscriber.go

@@ -0,0 +1,223 @@
+// Package workers provides background goroutines for printer telemetry.
+package workers
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/clients"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// MQTTSubscriberConfig controls MQTT background worker behaviour.
+type MQTTSubscriberConfig struct {
+	ReconnectInterval time.Duration
+}
+
+// DefaultMQTTSubscriberConfig returns sensible defaults.
+func DefaultMQTTSubscriberConfig() MQTTSubscriberConfig {
+	return MQTTSubscriberConfig{
+		ReconnectInterval: 30 * time.Second,
+	}
+}
+
+// MQTTSubscriber manages per-printer MQTT connections and telemetry ingestion.
+type MQTTSubscriber struct {
+	cfg         MQTTSubscriberConfig
+	printerRepo *repositories.PrinterRepository
+	usageRepo   *repositories.UsageLogRepository
+	sseBC       *sse.Broadcaster
+	pool        *pgxpool.Pool
+	clients     map[int]*clients.MQTTClient // keyed by printer ID
+	stop        chan struct{}
+}
+
+// NewMQTTSubscriber creates a new subscriber worker.
+func NewMQTTSubscriber(
+	cfg MQTTSubscriberConfig,
+	pool *pgxpool.Pool,
+	printerRepo *repositories.PrinterRepository,
+	usageRepo *repositories.UsageLogRepository,
+	sseBC *sse.Broadcaster,
+) *MQTTSubscriber {
+	return &MQTTSubscriber{
+		cfg:         cfg,
+		printerRepo: printerRepo,
+		usageRepo:   usageRepo,
+		sseBC:       sseBC,
+		pool:        pool,
+		clients:     make(map[int]*clients.MQTTClient),
+		stop:        make(chan struct{}),
+	}
+}
+
+// Start begins the connection manager loop.
+func (s *MQTTSubscriber) Start() {
+	go s.loop()
+}
+
+// Stop signals the loop to exit and disconnects all clients.
+func (s *MQTTSubscriber) Stop() {
+	close(s.stop)
+}
+
+func (s *MQTTSubscriber) loop() {
+	// Initial connect attempt.
+	s.connectAll()
+
+	ticker := time.NewTicker(s.cfg.ReconnectInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			s.connectAll()
+		case <-s.stop:
+			slog.Info("mqtt subscriber stopped")
+			for _, c := range s.clients {
+				c.Disconnect(1000)
+			}
+			return
+		}
+	}
+}
+
+func (s *MQTTSubscriber) connectAll() {
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	printers, err := s.printerRepo.GetAll(ctx)
+	if err != nil {
+		slog.Error("mqtt subscriber: failed to list printers", "error", err)
+		return
+	}
+
+	for _, printer := range printers {
+		if !printer.IsActive || printer.MQTTBrokerHost == nil || *printer.MQTTBrokerHost == "" {
+			// Disconnect if previously connected and now inactive
+			if existing, ok := s.clients[printer.ID]; ok {
+				existing.Disconnect(1000)
+				delete(s.clients, printer.ID)
+			}
+			continue
+		}
+
+		if _, ok := s.clients[printer.ID]; ok {
+			// Already connected — skip
+			continue
+		}
+
+		topicPrefix := ""
+		if printer.MQTTTopicPrefix != nil {
+			topicPrefix = *printer.MQTTTopicPrefix
+		}
+
+		cfg := clients.MQTTConfig{
+			BrokerHost:  *printer.MQTTBrokerHost,
+			TopicPrefix: topicPrefix,
+			TLSEnabled:  printer.MQTTTLSEnabled,
+			ClientID:    fmt.Sprintf("extrudex-printer-%d", printer.ID),
+		}
+
+		c, err := clients.NewMQTTClient(cfg)
+		if err != nil {
+			slog.Warn("mqtt subscriber: connect failed",
+				"printer", printer.Name,
+				"broker", cfg.BrokerHost,
+				"error", err,
+			)
+			continue
+		}
+
+		s.clients[printer.ID] = c
+
+		// Subscribe to telemetry topics
+		topics := clients.DefaultBambuTopics(topicPrefix)
+		for _, topic := range topics {
+			if err := c.Subscribe(topic, 0, s.makeHandler(printer)); err != nil {
+				slog.Warn("mqtt subscriber: subscribe failed",
+					"printer", printer.Name,
+					"topic", topic,
+					"error", err,
+				)
+			}
+		}
+
+		slog.Info("mqtt subscriber: connected",
+			"printer", printer.Name,
+			"broker", cfg.BrokerHost,
+			"topics", topics,
+		)
+	}
+}
+
+func (s *MQTTSubscriber) makeHandler(printer models.Printer) func([]byte) {
+	return func(payload []byte) {
+		slog.Debug("mqtt subscriber: message received",
+			"printer", printer.Name,
+			"size", len(payload),
+		)
+
+		// Attempt Bambu Lab parse
+		telemetry, err := clients.ParseBambuTelemetry(payload)
+		if err != nil {
+			slog.Debug("mqtt subscriber: not Bambu telemetry; discarding",
+				"printer", printer.Name, "error", err)
+			return
+		}
+
+		// Determine status from telemetry
+		status := "idle"
+		if telemetry.Print.Stage > 0 {
+			status = "printing"
+		}
+		s.broadcastStatus(printer.ID, printer.Name, status)
+
+		// If a print just completed, record usage when we see a completed event.
+		// Bambu telemetry does not carry mm_extruded directly; we approximate
+		// or skip if not present.  Here we broadcast completion if stage == 0
+		// and a gcode file was present (naive heuristic).
+		if telemetry.Print.GcodeFile != "" && telemetry.Print.Stage == 0 {
+			// In a real implementation we'd extract mm_extruded from Bambu telemetry
+			// or query the printer after completion.  For now broadcast completion.
+			s.broadcastJobCompleted(printer.ID, telemetry.Print.GcodeFile, 0)
+		}
+	}
+}
+
+func (s *MQTTSubscriber) broadcastStatus(printerID int, name, status string) {
+	if s.sseBC == nil {
+		return
+	}
+	ev, err := sse.NewEvent(sse.EventPrinterStatus, sse.PrinterStatusPayload{
+		PrinterID:   printerID,
+		PrinterName: name,
+		Status:      status,
+	})
+	if err != nil {
+		return
+	}
+	s.sseBC.Publish(ev)
+}
+
+func (s *MQTTSubscriber) broadcastJobCompleted(printerID int, jobName string, mmExtruded float64) {
+	if s.sseBC == nil {
+		return
+	}
+	grams := calculateGrams(mmExtruded, 1.75, 1.24)
+	gramsInt := int(grams)
+	ev, err := sse.NewEvent(sse.EventJobCompleted, sse.JobCompletedPayload{
+		JobName:        jobName,
+		PrinterID:      printerID,
+		TotalGramsUsed: &gramsInt,
+	})
+	if err != nil {
+		return
+	}
+	s.sseBC.Publish(ev)
+}

frontend/src/App.tsx

@@ -1,28 +1,25 @@
-import { useState, useEffect } from 'react'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { BrowserRouter, Routes, Route } from 'react-router-dom'
+import InventoryPage from './pages/InventoryPage'
 
-function App() {
-  const [health, setHealth] = useState<any>(null)
-
-  useEffect(() => {
-    fetch('/api/health')
-      .then(r => r.json())
-      .then(setHealth)
-      .catch(console.error)
-  }, [])
+const queryClient = new QueryClient()
 
+export default function App() {
   return (
-    <div className="min-h-screen flex items-center justify-center">
-      <div className="p-6 rounded-lg bg-slate-800 shadow-xl max-w-md w-full">
-        <h1 className="text-2xl font-bold mb-4 text-emerald-400">Extrudex</h1>
-        <p className="text-slate-300 mb-4">React frontend scaffold</p>
-        {health && (
-          <pre className="text-xs bg-slate-900 p-3 rounded overflow-auto">
-            {JSON.stringify(health, null, 2)}
-          </pre>
-        )}
-      </div>
-    </div>
+    <QueryClientProvider client={queryClient}>
+      <BrowserRouter>
+        <div className="min-h-screen bg-slate-900 text-slate-50">
+          <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-3 sticky top-0 z-20">
+            <div className="w-8 h-8 rounded bg-emerald-500 flex items-center justify-center text-slate-900 font-bold text-lg">E</div>
+            <h1 className="text-lg font-semibold">Extrudex</h1>
+          </header>
+          <main className="p-4">
+            <Routes>
+              <Route path="/" element={<InventoryPage />} />
+            </Routes>
+          </main>
+        </div>
+      </BrowserRouter>
+    </QueryClientProvider>
   )
 }
-
-export default App

frontend/src/components/ColorSwatch.tsx

@@ -0,0 +1,18 @@
+interface ColorSwatchProps {
+  colorHex: string
+  size?: number
+}
+
+export default function ColorSwatch({ colorHex, size = 24 }: ColorSwatchProps) {
+  return (
+    <div
+      className="rounded-full border border-slate-600 shadow-sm inline-block"
+      style={{
+        backgroundColor: colorHex.startsWith('#') ? colorHex : `#${colorHex}`,
+        width: size,
+        height: size,
+      }}
+      title={colorHex}
+    />
+  )
+}

frontend/src/pages/InventoryPage.tsx

@@ -0,0 +1,339 @@
+import { useState, useMemo } from 'react'
+import { useQuery } from '@tanstack/react-query'
+import { Search, Filter, ChevronLeft, ChevronRight, Trash2, Pencil, Plus, AlertTriangle } from 'lucide-react'
+import ColorSwatch from '../components/ColorSwatch'
+import { fetchFilaments, deleteFilament } from '../services/filamentService'
+import type { FilamentSpool, FilamentFilter } from '../types/filament'
+
+const PAGE_SIZE = 20
+
+type SortField = 'name' | 'remaining_grams' | 'cost_usd'
+type SortDir = 'asc' | 'desc'
+
+export default function InventoryPage() {
+  const [search, setSearch] = useState('')
+  const [material, setMaterial] = useState('')
+  const [finish, setFinish] = useState('')
+  const [lowStockOnly, setLowStockOnly] = useState(false)
+  const [sortBy, setSortBy] = useState<SortField>('name')
+  const [sortDir, setSortDir] = useState<SortDir>('asc')
+  const [page, setPage] = useState(0)
+  const [deleteId, setDeleteId] = useState<number | null>(null)
+
+  const filter: FilamentFilter = useMemo(() => ({
+    material: material || undefined,
+    finish: finish || undefined,
+    low_stock: lowStockOnly,
+    sort_by: sortBy,
+    sort_dir: sortDir,
+    limit: PAGE_SIZE,
+    offset: page * PAGE_SIZE,
+  }), [material, finish, lowStockOnly, sortBy, sortDir, page])
+
+  const { data, isLoading, error, refetch } = useQuery({
+    queryKey: ['filaments', filter],
+    queryFn: () => fetchFilaments(filter),
+  })
+
+  const filaments = data?.data ?? []
+  const total = data?.total ?? 0
+  const totalPages = Math.max(1, Math.ceil(total / PAGE_SIZE))
+
+  // Client-side search filter (name/barcode) since backend may not support it yet.
+  const filtered = useMemo(() => {
+    if (!search.trim()) return filaments
+    const q = search.toLowerCase()
+    return filaments.filter(
+      (f: FilamentSpool) =>
+        f.name.toLowerCase().includes(q) ||
+        (f.barcode && f.barcode.toLowerCase().includes(q))
+    )
+  }, [filaments, search])
+
+  const handleSort = (field: SortField) => {
+    if (sortBy === field) {
+      setSortDir(prev => (prev === 'asc' ? 'desc' : 'asc'))
+    } else {
+      setSortBy(field)
+      setSortDir('asc')
+    }
+    setPage(0)
+  }
+
+  const handleDelete = async (id: number) => {
+    await deleteFilament(id)
+    setDeleteId(null)
+    refetch()
+  }
+
+  const SortIndicator = ({ field }: { field: SortField }) => {
+    if (sortBy !== field) return <span className="text-slate-600 ml-1">↕</span>
+    return <span className="text-emerald-400 ml-1">{sortDir === 'asc' ? '↑' : '↓'}</span>
+  }
+
+  return (
+    <div className="space-y-4">
+      {/* Header */}
+      <div className="flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
+        <div>
+          <h2 className="text-xl font-bold text-slate-100">Filament Inventory</h2>
+          <p className="text-sm text-slate-400">{total} spool(s) total</p>
+        </div>
+        <button className="inline-flex items-center gap-2 rounded-lg bg-emerald-600 px-4 py-2 text-sm font-semibold text-white hover:bg-emerald-500 active:bg-emerald-700 transition-colors">
+          <Plus size={16} /> Add Spool
+        </button>
+      </div>
+
+      {/* Filters */}
+      <div className="flex flex-col lg:flex-row gap-3">
+        {/* Search */}
+        <div className="relative flex-1">
+          <Search size={16} className="absolute left-3 top-1/2 -translate-y-1/2 text-slate-400" />
+          <input
+            type="text"
+            placeholder="Search by name or barcode…"
+            value={search}
+            onChange={e => { setSearch(e.target.value); setPage(0) }}
+            className="w-full rounded-lg bg-slate-800 border border-slate-700 pl-9 pr-3 py-2 text-sm text-slate-100 placeholder-slate-500 focus:outline-none focus:ring-2 focus:ring-emerald-500 focus:border-emerald-500"
+          />
+        </div>
+
+        {/* Material filter */}
+        <select
+          value={material}
+          onChange={e => { setMaterial(e.target.value); setPage(0) }}
+          className="rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500"
+        >
+          <option value="">All Materials</option>
+          <option value="PLA">PLA</option>
+          <option value="PETG">PETG</option>
+          <option value="ABS">ABS</option>
+          <option value="TPU">TPU</option>
+          <option value="ASA">ASA</option>
+          <option value="Nylon">Nylon</option>
+          <option value="PC">PC</option>
+        </select>
+
+        {/* Finish filter */}
+        <select
+          value={finish}
+          onChange={e => { setFinish(e.target.value); setPage(0) }}
+          className="rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500"
+        >
+          <option value="">All Finishes</option>
+          <option value="Basic">Basic</option>
+          <option value="Silk">Silk</option>
+          <option value="Matte">Matte</option>
+          <option value="Glossy">Glossy</option>
+          <option value="Wood">Wood</option>
+          <option value="Marble">Marble</option>
+        </select>
+
+        {/* Low stock toggle */}
+        <label className="inline-flex items-center gap-2 rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 cursor-pointer select-none hover:bg-slate-750">
+          <Filter size={14} className="text-amber-400" />
+          <input
+            type="checkbox"
+            checked={lowStockOnly}
+            onChange={e => { setLowStockOnly(e.target.checked); setPage(0) }}
+            className="accent-amber-500"
+          />
+          Low Stock Only
+        </label>
+      </div>
+
+      {/* Loading / Error */}
+      {isLoading && (
+        <div className="text-center py-12 text-slate-400">Loading spools…</div>
+      )}
+      {error && (
+        <div className="text-center py-12 text-red-400">
+          Failed to load inventory.
+          <button onClick={() => refetch()} className="ml-2 underline hover:text-red-300">Retry</button>
+        </div>
+      )}
+
+      {/* Desktop Table */}
+      {!isLoading && !error && (
+        <>
+          <div className="hidden md:block overflow-x-auto rounded-lg border border-slate-700">
+            <table className="w-full text-sm">
+              <thead className="bg-slate-800 text-slate-300">
+                <tr>
+                  <th className="px-4 py-3 text-left font-semibold cursor-pointer select-none hover:text-slate-100" onClick={() => handleSort('name')}>
+                    Name <SortIndicator field="name" />
+                  </th>
+                  <th className="px-4 py-3 text-left font-semibold">Material</th>
+                  <th className="px-4 py-3 text-left font-semibold">Finish</th>
+                  <th className="px-4 py-3 text-left font-semibold">Color</th>
+                  <th className="px-4 py-3 text-right font-semibold cursor-pointer select-none hover:text-slate-100" onClick={() => handleSort('remaining_grams')}>
+                    Remaining <SortIndicator field="remaining_grams" />
+                  </th>
+                  <th className="px-4 py-3 text-right font-semibold cursor-pointer select-none hover:text-slate-100" onClick={() => handleSort('cost_usd')}>
+                    Cost <SortIndicator field="cost_usd" />
+                  </th>
+                  <th className="px-4 py-3 text-center font-semibold">Status</th>
+                  <th className="px-4 py-3 text-right font-semibold">Actions</th>
+                </tr>
+              </thead>
+              <tbody className="divide-y divide-slate-700">
+                {filtered.length === 0 && (
+                  <tr>
+                    <td colSpan={8} className="px-4 py-8 text-center text-slate-500">No spools found.</td>
+                  </tr>
+                )}
+                {filtered.map((spool: FilamentSpool) => {
+                  const isLow = spool.remaining_grams <= spool.low_stock_threshold_grams
+                  return (
+                    <tr key={spool.id} className={`${isLow ? 'bg-red-900/20' : 'bg-slate-800/50'} hover:bg-slate-700/50 transition-colors`}>
+                      <td className="px-4 py-3 font-medium text-slate-100">{spool.name}</td>
+                      <td className="px-4 py-3 text-slate-300">{spool.material_base?.name ?? '—'}</td>
+                      <td className="px-4 py-3 text-slate-300">{spool.material_finish?.name ?? '—'}</td>
+                      <td className="px-4 py-3">
+                        <div className="flex items-center gap-2">
+                          <ColorSwatch colorHex={spool.color_hex} size={20} />
+                          <span className="text-xs text-slate-400 uppercase">{spool.color_hex}</span>
+                        </div>
+                      </td>
+                      <td className="px-4 py-3 text-right tabular-nums text-slate-200">{spool.remaining_grams.toLocaleString()} g</td>
+                      <td className="px-4 py-3 text-right tabular-nums text-slate-300">{spool.cost_usd != null ? `$${spool.cost_usd.toFixed(2)}` : '—'}</td>
+                      <td className="px-4 py-3 text-center">
+                        {isLow ? (
+                          <span className="inline-flex items-center gap-1 rounded-full bg-red-900/50 border border-red-700 px-2 py-0.5 text-xs font-medium text-red-300">
+                            <AlertTriangle size={12} /> Low
+                          </span>
+                        ) : (
+                          <span className="inline-flex items-center rounded-full bg-emerald-900/30 border border-emerald-700 px-2 py-0.5 text-xs font-medium text-emerald-300">OK</span>
+                        )}
+                      </td>
+                      <td className="px-4 py-3 text-right">
+                        <div className="flex items-center justify-end gap-2">
+                          <button className="p-1.5 rounded hover:bg-slate-600 text-slate-400 hover:text-blue-400 transition-colors" title="Edit">
+                            <Pencil size={14} />
+                          </button>
+                          <button
+                            onClick={() => setDeleteId(spool.id)}
+                            className="p-1.5 rounded hover:bg-slate-600 text-slate-400 hover:text-red-400 transition-colors"
+                            title="Delete"
+                          >
+                            <Trash2 size={14} />
+                          </button>
+                        </div>
+                      </td>
+                    </tr>
+                  )
+                })}
+              </tbody>
+            </table>
+          </div>
+
+          {/* Mobile Cards */}
+          <div className="md:hidden space-y-3">
+            {filtered.length === 0 && (
+              <div className="text-center py-12 text-slate-500">No spools found.</div>
+            )}
+            {filtered.map((spool: FilamentSpool) => {
+              const isLow = spool.remaining_grams <= spool.low_stock_threshold_grams
+              return (
+                <div key={spool.id} className={`rounded-lg border ${isLow ? 'border-red-700 bg-red-900/10' : 'border-slate-700 bg-slate-800'} p-4 space-y-2`}>
+                  <div className="flex items-start justify-between">
+                    <div>
+                      <div className="font-semibold text-slate-100">{spool.name}</div>
+                      <div className="text-xs text-slate-400 mt-0.5">{spool.material_base?.name ?? '—'} · {spool.material_finish?.name ?? '—'}</div>
+                    </div>
+                    {isLow ? (
+                      <span className="inline-flex items-center gap-1 rounded-full bg-red-900/50 border border-red-700 px-2 py-0.5 text-xs font-medium text-red-300">
+                        <AlertTriangle size={12} /> Low
+                      </span>
+                    ) : (
+                      <span className="inline-flex items-center rounded-full bg-emerald-900/30 border border-emerald-700 px-2 py-0.5 text-xs font-medium text-emerald-300">OK</span>
+                    )}
+                  </div>
+
+                  <div className="flex items-center gap-3 text-sm">
+                    <div className="flex items-center gap-2">
+                      <ColorSwatch colorHex={spool.color_hex} size={20} />
+                      <span className="text-slate-400 uppercase text-xs">{spool.color_hex}</span>
+                    </div>
+                  </div>
+
+                  <div className="flex items-center justify-between text-sm">
+                    <span className="text-slate-400">Remaining: <span className="text-slate-200 font-medium tabular-nums">{spool.remaining_grams.toLocaleString()} g</span></span>
+                    <span className="text-slate-400">{spool.cost_usd != null ? `$${spool.cost_usd.toFixed(2)}` : '—'}</span>
+                  </div>
+
+                  <div className="flex items-center justify-end gap-2 pt-1">
+                    <button className="flex items-center gap-1 rounded-md bg-slate-700 px-3 py-1.5 text-xs font-medium text-slate-200 hover:bg-slate-600">
+                      <Pencil size={12} /> Edit
+                    </button>
+                    <button
+                      onClick={() => setDeleteId(spool.id)}
+                      className="flex items-center gap-1 rounded-md bg-red-900/30 border border-red-700 px-3 py-1.5 text-xs font-medium text-red-300 hover:bg-red-900/50"
+                    >
+                      <Trash2 size={12} /> Delete
+                    </button>
+                  </div>
+                </div>
+              )
+            })}
+          </div>
+
+          {/* Pagination */}
+          <div className="flex items-center justify-between pt-2">
+            <span className="text-sm text-slate-400">
+              Showing {page * PAGE_SIZE + 1}–{Math.min((page + 1) * PAGE_SIZE, total)} of {total}
+            </span>
+            <div className="flex items-center gap-2">
+              <button
+                onClick={() => setPage(p => Math.max(0, p - 1))}
+                disabled={page === 0}
+                className="p-2 rounded-lg bg-slate-800 border border-slate-700 text-slate-300 hover:bg-slate-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors"
+              >
+                <ChevronLeft size={16} />
+              </button>
+              <span className="text-sm text-slate-300 tabular-nums">{page + 1} / {totalPages}</span>
+              <button
+                onClick={() => setPage(p => Math.min(totalPages - 1, p + 1))}
+                disabled={page >= totalPages - 1}
+                className="p-2 rounded-lg bg-slate-800 border border-slate-700 text-slate-300 hover:bg-slate-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors"
+              >
+                <ChevronRight size={16} />
+              </button>
+            </div>
+          </div>
+        </>
+      )}
+
+      {/* Delete confirmation modal */}
+      {deleteId !== null && (
+        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/60 backdrop-blur-sm p-4">
+          <div className="w-full max-w-sm rounded-xl bg-slate-800 border border-slate-700 p-6 shadow-2xl space-y-4">
+            <div className="flex items-center gap-3">
+              <div className="flex h-10 w-10 items-center justify-center rounded-full bg-red-900/30">
+                <AlertTriangle size={20} className="text-red-400" />
+              </div>
+              <div>
+                <h3 className="text-lg font-semibold text-slate-100">Delete Spool?</h3>
+                <p className="text-sm text-slate-400">This action cannot be undone.</p>
+              </div>
+            </div>
+            <div className="flex justify-end gap-3">
+              <button
+                onClick={() => setDeleteId(null)}
+                className="rounded-lg bg-slate-700 px-4 py-2 text-sm font-medium text-slate-200 hover:bg-slate-600 transition-colors"
+              >
+                Cancel
+              </button>
+              <button
+                onClick={() => handleDelete(deleteId)}
+                className="rounded-lg bg-red-600 px-4 py-2 text-sm font-medium text-white hover:bg-red-500 transition-colors"
+              >
+                Delete
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
+    </div>
+  )
+}

frontend/src/services/filamentService.ts

@@ -0,0 +1,24 @@
+import axios from 'axios'
+import type { FilamentSpool, ListResponse, FilamentFilter } from '../types/filament'
+
+const API_BASE = '/api'
+
+export async function fetchFilaments(filter: FilamentFilter): Promise<ListResponse<FilamentSpool>> {
+  const params = new URLSearchParams()
+  if (filter.material) params.set('material', filter.material)
+  if (filter.finish) params.set('finish', filter.finish)
+  if (filter.color) params.set('color', filter.color)
+  if (filter.low_stock) params.set('low_stock', 'true')
+  if (filter.search) params.set('search', filter.search)
+  if (filter.sort_by) params.set('sort_by', filter.sort_by)
+  if (filter.sort_dir) params.set('sort_dir', filter.sort_dir)
+  if (filter.limit !== undefined) params.set('limit', String(filter.limit))
+  if (filter.offset !== undefined) params.set('offset', String(filter.offset))
+
+  const res = await axios.get<ListResponse<FilamentSpool>>(`${API_BASE}/filaments?${params.toString()}`)
+  return res.data
+}
+
+export async function deleteFilament(id: number): Promise<void> {
+  await axios.delete(`${API_BASE}/filaments/${id}`)
+}

frontend/src/types/filament.ts

@@ -0,0 +1,72 @@
+// Extrudex domain types
+
+export interface MaterialBase {
+  id: number
+  name: string
+  density_g_cm3: number
+  extrusion_temp_min?: number
+  extrusion_temp_max?: number
+  bed_temp_min?: number
+  bed_temp_max?: number
+  created_at: string
+  updated_at: string
+}
+
+export interface MaterialFinish {
+  id: number
+  name: string
+  description?: string
+  created_at: string
+  updated_at: string
+}
+
+export interface MaterialModifier {
+  id: number
+  name: string
+  description?: string
+  created_at: string
+  updated_at: string
+}
+
+export interface FilamentSpool {
+  id: number
+  name: string
+  material_base_id: number
+  material_base?: MaterialBase
+  material_finish_id: number
+  material_finish?: MaterialFinish
+  material_modifier_id?: number
+  material_modifier?: MaterialModifier
+  color_hex: string
+  brand?: string
+  diameter_mm: number
+  initial_grams: number
+  remaining_grams: number
+  spool_weight_grams?: number
+  cost_usd?: number
+  low_stock_threshold_grams: number
+  notes?: string
+  barcode?: string
+  deleted_at?: string
+  created_at: string
+  updated_at: string
+}
+
+export interface ListResponse<T> {
+  data: T[]
+  total: number
+  limit: number
+  offset: number
+}
+
+export interface FilamentFilter {
+  material?: string
+  finish?: string
+  color?: string
+  low_stock?: boolean
+  search?: string
+  sort_by?: string
+  sort_dir?: 'asc' | 'desc'
+  limit?: number
+  offset?: number
+}