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