flatrender/services/render/internal/devworker/devworker.go

// Package devworker runs an in-process mock render worker so the full render
// flow works in development without a Windows After Effects node.
//
// When enabled (RENDER_DEV_WORKER=true) it polls for Queued jobs, claims the
// oldest, and drives it through the render steps — emitting progress and live
// preview frames exactly like a real node agent would — then marks it Done.
//
// It is NEVER started in production; real render nodes claim jobs over the
// internal API instead.
package devworker

import (
	"bytes"
	"context"
	"encoding/base64"
	"image"
	"image/color"
	"image/draw"
	"image/png"
	"log"
	"time"

	"github.com/flatrender/render-svc/internal/db"
	"github.com/google/uuid"
)

type Worker struct {
	store    *db.Store
	interval time.Duration
}

func New(store *db.Store) *Worker {
	return &Worker{store: store, interval: 2 * time.Second}
}

// Run blocks until ctx is cancelled, processing one job at a time.
func (w *Worker) Run(ctx context.Context) {
	log.Printf("[devworker] mock render worker started (poll %s) — NOT for production", w.interval)
	ticker := time.NewTicker(w.interval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			log.Printf("[devworker] stopped")
			return
		case <-ticker.C:
			w.tick(ctx)
		}
	}
}

func (w *Worker) tick(ctx context.Context) {
	jobID, err := w.store.DevClaimNextQueued(ctx)
	if err != nil {
		log.Printf("[devworker] claim error: %v", err)
		return
	}
	if jobID == uuid.Nil {
		return // queue empty
	}
	log.Printf("[devworker] claimed job %s — simulating render", jobID)
	w.simulate(ctx, jobID)
}

// simulate drives a single job through the render steps with progress + preview.
func (w *Worker) simulate(ctx context.Context, jobID uuid.UUID) {
	steps := []struct {
		step string
		pct  int
	}{
		{"Preparing", 5},
		{"TemplateCache", 15},
		{"JsxGen", 25},
		{"Rendering", 40},
		{"Rendering", 60},
		{"Rendering", 80},
		{"Optimisation", 88},
		{"Video", 92},
		{"Uploading", 97},
	}

	for _, s := range steps {
		select {
		case <-ctx.Done():
			return
		case <-time.After(1200 * time.Millisecond):
		}
		if err := w.store.UpdateJobStepProgress(ctx, jobID, s.step, s.pct); err != nil {
			// Job was cancelled / deleted mid-flight — stop quietly.
			log.Printf("[devworker] job %s no longer updatable (%v) — abandoning", jobID, err)
			return
		}
		_ = w.store.UpdateJobPreview(ctx, jobID, previewB64(s.pct))
		log.Printf("[devworker] job %s — %s %d%%", jobID, s.step, s.pct)
	}

	// Complete (no export — dev renders produce no downloadable artifact).
	if _, err := w.store.CompleteJob(ctx, jobID, nil); err != nil {
		log.Printf("[devworker] complete job %s failed: %v", jobID, err)
		return
	}
	log.Printf("[devworker] job %s done", jobID)
}

// previewB64 builds a 320×180 PNG with a progress bar — same idea as the node
// agent's GeneratePreviewB64, kept local so render-svc has no node-agent dep.
func previewB64(pct int) string {
	const w, h = 320, 180
	img := image.NewRGBA(image.Rect(0, 0, w, h))
	draw.Draw(img, img.Bounds(), &image.Uniform{color.RGBA{15, 17, 30, 255}}, image.Point{}, draw.Src)

	barY, barH := h/2-6, 12
	draw.Draw(img, image.Rect(20, barY, w-20, barY+barH),
		&image.Uniform{color.RGBA{30, 34, 56, 255}}, image.Point{}, draw.Src)

	if pct > 0 {
		fillW := int(float64(w-40) * float64(pct) / 100.0)
		if fillW < 2 {
			fillW = 2
		}
		r := uint8(76 - int(float64(pct)*0.3))
		g := uint8(110 + int(float64(pct)*0.8))
		b := uint8(245 - int(float64(pct)*1.3))
		draw.Draw(img, image.Rect(20, barY, 20+fillW, barY+barH),
			&image.Uniform{color.RGBA{r, g, b, 255}}, image.Point{}, draw.Src)
	}

	var buf bytes.Buffer
	_ = png.Encode(&buf, img)
	return base64.StdEncoding.EncodeToString(buf.Bytes())
}