CUB-135: Subscribe to SSE in React and update UI

2026-05-09 18:09:56 -04:00
10 changed files with 301 additions and 855 deletions
--- a/backend/cmd/server/main.go
+++ b/backend/cmd/server/main.go
@@ -11,10 +11,8 @@ 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() {
@@ -42,11 +40,6 @@ 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()
@@ -54,19 +47,6 @@ func main() {

 	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, sseBC)

--- a/backend/internal/clients/moonraker.go
+++ b/backend/internal/clients/moonraker.go
@@ -1,161 +0,0 @@
-// 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
-}
--- a/backend/internal/clients/mqtt.go
+++ b/backend/internal/clients/mqtt.go
@@ -1,119 +0,0 @@
-// 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",
-	}
-}
--- a/backend/internal/workers/moonraker_poller.go
+++ b/backend/internal/workers/moonraker_poller.go
@@ -1,321 +0,0 @@
-// 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
-}
--- a/backend/internal/workers/mqtt_subscriber.go
+++ b/backend/internal/workers/mqtt_subscriber.go
@@ -1,223 +0,0 @@
-// 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)
-}
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -1,24 +1,34 @@
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
 import { BrowserRouter, Routes, Route } from 'react-router-dom'
 import InventoryPage from './pages/InventoryPage'
+import ToastContainer from './components/ToastContainer'
+import { useSSE } from './hooks/useSSE'

 const queryClient = new QueryClient()

+function SSEProvider({ children }: { children: React.ReactNode }) {
+  useSSE()
+  return <>{children}</>
+}
+
 export default function App() {
  return (
    <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>
+        <SSEProvider>
+          <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>
+          <ToastContainer />
+        </SSEProvider>
      </BrowserRouter>
    </QueryClientProvider>
  )
--- a/frontend/src/components/PrinterStatusBadge.tsx
+++ b/frontend/src/components/PrinterStatusBadge.tsx
@@ -0,0 +1,17 @@
+import { Printer } from 'lucide-react'
+
+const STYLES = {
+  online: 'bg-emerald-600 text-white',
+  offline: 'bg-slate-600 text-slate-200',
+  printing: 'bg-blue-600 text-white animate-pulse',
+}
+
+export default function PrinterStatusBadge({ status, name }: { status: string; name?: string }) {
+  const style = STYLES[status as keyof typeof STYLES] ?? STYLES.offline
+  return (
+    <span className={`inline-flex items-center gap-1.5 rounded-full px-2.5 py-1 text-xs font-medium ${style}`}>
+      <Printer size={12} />
+      {name ? `${name} · ${status}` : status}
+    </span>
+  )
+}
--- a/frontend/src/components/ToastContainer.tsx
+++ b/frontend/src/components/ToastContainer.tsx
@@ -0,0 +1,70 @@
+import { useEffect, useState, useCallback } from 'react'
+import { X, CheckCircle, AlertTriangle, Info } from 'lucide-react'
+import { addToastListener, type ToastMessage } from '../hooks/useSSE'
+
+const ICONS = {
+  info: Info,
+  success: CheckCircle,
+  warning: AlertTriangle,
+}
+
+const STYLES = {
+  info: 'border-blue-600 bg-blue-900/40 text-blue-100',
+  success: 'border-emerald-600 bg-emerald-900/40 text-emerald-100',
+  warning: 'border-amber-600 bg-amber-900/40 text-amber-100',
+}
+
+export default function ToastContainer() {
+  const [toasts, setToasts] = useState<ToastMessage[]>([])
+
+  const remove = useCallback((id: string) => {
+    setToasts(prev => prev.filter(t => t.id !== id))
+  }, [])
+
+  useEffect(() => {
+    return addToastListener((toast) => {
+      setToasts(prev => {
+        // Prevent duplicate identical toasts within 3 seconds
+        const now = Date.now()
+        const recent = prev.filter(
+          t => t.title === toast.title && now - parseInt(t.id.split('-').pop() || '0', 10) < 3000
+        )
+        if (recent.length > 0) return prev
+        return [...prev.slice(-4), toast]
+      })
+      // Auto-dismiss after 5 seconds
+      setTimeout(() => remove(toast.id), 5000)
+    })
+  }, [remove])
+
+  return (
+    <div className="fixed bottom-4 right-4 z-50 flex flex-col gap-2 max-w-sm w-full pointer-events-none">
+      {toasts.map((toast) => {
+        const Icon = ICONS[toast.type]
+        return (
+          <div
+            key={toast.id}
+            className={`pointer-events-auto rounded-lg border px-4 py-3 shadow-lg backdrop-blur-sm transition-all ${STYLES[toast.type]}`}
+          >
+            <div className="flex items-start gap-3">
+              <Icon size={18} className="mt-0.5 shrink-0" />
+              <div className="flex-1 min-w-0">
+                <p className="text-sm font-semibold leading-snug">{toast.title}</p>
+                {toast.body && (
+                  <p className="text-xs opacity-80 mt-0.5">{toast.body}</p>
+                )}
+              </div>
+              <button
+                onClick={() => remove(toast.id)}
+                className="shrink-0 -mr-1 -mt-1 p-1 rounded hover:bg-white/10 text-current opacity-70 hover:opacity-100 transition-opacity"
+                aria-label="Dismiss"
+              >
+                <X size={14} />
+              </button>
+            </div>
+          </div>
+        )
+      })}
+    </div>
+  )
+}
--- a/frontend/src/hooks/.gitkeep
+++ b/frontend/src/hooks/.gitkeep
--- a/frontend/src/hooks/useSSE.ts
+++ b/frontend/src/hooks/useSSE.ts
@@ -0,0 +1,193 @@
+import { useEffect, useRef, useCallback } from 'react'
+import { useQueryClient } from '@tanstack/react-query'
+
+export type SSEEventType =
+  | 'printer.status'
+  | 'job.started'
+  | 'job.completed'
+  | 'filament.low'
+
+export interface SSEEvent {
+  type: SSEEventType
+  payload: unknown
+  timestamp: string
+}
+
+export interface ToastMessage {
+  id: string
+  type: 'info' | 'success' | 'warning'
+  title: string
+  body?: string
+}
+
+let toastListeners: Array<(toast: ToastMessage) => void> = []
+
+export function addToastListener(cb: (toast: ToastMessage) => void) {
+  toastListeners.push(cb)
+  return () => {
+    toastListeners = toastListeners.filter(l => l !== cb)
+  }
+}
+
+function emitToast(toast: ToastMessage) {
+  toastListeners.forEach(cb => cb(toast))
+}
+
+const RECONNECT_BASE_MS = 1000
+const RECONNECT_MAX_MS = 30000
+
+export function useSSE(enabled = true) {
+  const queryClient = useQueryClient()
+  const esRef = useRef<EventSource | null>(null)
+  const reconnectTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const attemptRef = useRef(0)
+
+  const connect = useCallback(() => {
+    if (!enabled) return
+    if (esRef.current) {
+      esRef.current.close()
+    }
+
+    const es = new EventSource('/api/events')
+    esRef.current = es
+
+    es.onopen = () => {
+      attemptRef.current = 0
+    }
+
+    es.addEventListener('printer.status', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          printer_id: number
+          printer_name: string
+          status: string
+        }
+        // Update printer list cache if it exists
+        queryClient.setQueryData(['printers'], (old: unknown) => {
+          if (!Array.isArray(old)) return old
+          return old.map((p: any) =>
+            p.id === payload.printer_id
+              ? { ...p, status: payload.status, name: payload.printer_name }
+              : p
+          )
+        })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('job.started', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          job_id: number
+          job_name: string
+          printer_id: number
+          spool_id?: number
+        }
+        emitToast({
+          id: `job-started-${payload.job_id}-${Date.now()}`,
+          type: 'info',
+          title: `Job started: ${payload.job_name}`,
+          body: `Printer #${payload.printer_id}`,
+        })
+        // Invalidate print jobs list
+        queryClient.invalidateQueries({ queryKey: ['print-jobs'] })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('job.completed', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          job_id: number
+          job_name: string
+          printer_id: number
+          duration_seconds?: number
+          total_grams_used?: number
+          total_cost_usd?: number
+        }
+        const parts: string[] = []
+        if (payload.duration_seconds != null) {
+          const mins = Math.round(payload.duration_seconds / 60)
+          parts.push(`${mins} min`)
+        }
+        if (payload.total_grams_used != null) {
+          parts.push(`${payload.total_grams_used.toFixed(1)} g used`)
+        }
+        emitToast({
+          id: `job-completed-${payload.job_id}-${Date.now()}`,
+          type: 'success',
+          title: `Job completed: ${payload.job_name}`,
+          body: parts.join(' · ') || `Printer #${payload.printer_id}`,
+        })
+        queryClient.invalidateQueries({ queryKey: ['print-jobs'] })
+        queryClient.invalidateQueries({ queryKey: ['filaments'] })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('filament.low', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          spool_id: number
+          spool_name: string
+          remaining_grams: number
+          threshold_grams: number
+        }
+        emitToast({
+          id: `filament-low-${payload.spool_id}-${Date.now()}`,
+          type: 'warning',
+          title: `Low filament: ${payload.spool_name}`,
+          body: `${payload.remaining_grams} g remaining (threshold ${payload.threshold_grams} g)`,
+        })
+        // Update filament inventory cache in place for instant UI feedback
+        queryClient.setQueryData(['filaments'], (old: unknown) => {
+          if (!old || typeof old !== 'object') return old
+          const o = old as { data?: Array<Record<string, unknown>>; total?: number }
+          if (!Array.isArray(o.data)) return old
+          return {
+            ...o,
+            data: o.data.map((f) =>
+              (f.id as number) === payload.spool_id
+                ? { ...f, remaining_grams: payload.remaining_grams }
+                : f
+            ),
+          }
+        })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.onerror = () => {
+      es.close()
+      // Exponential backoff with jitter
+      const base = Math.min(RECONNECT_MAX_MS, RECONNECT_BASE_MS * 2 ** attemptRef.current)
+      const jitter = Math.random() * 1000
+      const delay = base + jitter
+      attemptRef.current += 1
+      reconnectTimerRef.current = setTimeout(() => {
+        connect()
+      }, delay)
+    }
+  }, [enabled, queryClient])
+
+  useEffect(() => {
+    connect()
+    return () => {
+      if (reconnectTimerRef.current) {
+        clearTimeout(reconnectTimerRef.current)
+      }
+      if (esRef.current) {
+        esRef.current.close()
+        esRef.current = null
+      }
+    }
+  }, [connect])
+}