libnovel/backend/cmd/backend/main.go

// Command backend is the LibNovel HTTP API server.
//
// It exposes all endpoints consumed by the SvelteKit UI: book/chapter reads,
// scrape-task creation, presigned MinIO URLs, audio-task creation, reading
// progress, live novelfire.net search, and Kokoro voice list.
//
// All heavy lifting (scraping, TTS generation) is delegated to the runner
// binary via PocketBase task records. The backend never scrapes directly.
//
// Usage:
//
//	backend          # start HTTP server (blocks until SIGINT/SIGTERM)
package main

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/getsentry/sentry-go"
	"github.com/libnovel/backend/internal/backend"
	"github.com/libnovel/backend/internal/config"
	"github.com/libnovel/backend/internal/kokoro"
	"github.com/libnovel/backend/internal/meili"
	"github.com/libnovel/backend/internal/otelsetup"
	"github.com/libnovel/backend/internal/storage"
)

// version and commit are set at build time via -ldflags.
var (
	version = "dev"
	commit  = "unknown"
)

func main() {
	if err := run(); err != nil {
		fmt.Fprintf(os.Stderr, "backend: fatal: %v\n", err)
		os.Exit(1)
	}
}

func run() error {
	cfg := config.Load()

	// ── Sentry / GlitchTip error tracking ────────────────────────────────────
	if dsn := os.Getenv("GLITCHTIP_DSN"); dsn != "" {
		if err := sentry.Init(sentry.ClientOptions{
			Dsn:              dsn,
			Release:          version + "@" + commit,
			TracesSampleRate: 0.1,
		}); err != nil {
			fmt.Fprintf(os.Stderr, "backend: sentry init warning: %v\n", err)
		} else {
			defer sentry.Flush(2 * time.Second)
		}
	}

	// ── Logger ───────────────────────────────────────────────────────────────
	log := buildLogger(cfg.LogLevel)
	log.Info("backend starting",
		"version", version,
		"commit", commit,
		"addr", cfg.HTTP.Addr,
	)

	// ── Context: cancel on SIGINT / SIGTERM ──────────────────────────────────
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	// ── OpenTelemetry tracing ─────────────────────────────────────────────────
	otelShutdown, err := otelsetup.Init(ctx, version)
	if err != nil {
		return fmt.Errorf("init otel: %w", err)
	}
	if otelShutdown != nil {
		defer otelShutdown()
		log.Info("otel tracing enabled", "endpoint", os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT"))
	}

	// ── Storage ──────────────────────────────────────────────────────────────
	store, err := storage.NewStore(ctx, cfg, log)
	if err != nil {
		return fmt.Errorf("init storage: %w", err)
	}

	// ── Kokoro (voice list only; audio generation is done by the runner) ─────
	var kokoroClient kokoro.Client
	if cfg.Kokoro.URL != "" {
		kokoroClient = kokoro.New(cfg.Kokoro.URL)
		log.Info("kokoro voices enabled", "url", cfg.Kokoro.URL)
	} else {
		log.Info("KOKORO_URL not set — voice list will use built-in fallback")
		kokoroClient = &noopKokoro{}
	}

	// ── Meilisearch (search reads only; indexing is the runner's job) ────────
	var searchIndex meili.Client
	if cfg.Meilisearch.URL != "" {
		searchIndex = meili.New(cfg.Meilisearch.URL, cfg.Meilisearch.APIKey)
		log.Info("meilisearch search enabled", "url", cfg.Meilisearch.URL)
	} else {
		log.Info("MEILI_URL not set — search will use PocketBase substring fallback")
		searchIndex = meili.NoopClient{}
	}

	// ── Backend server ───────────────────────────────────────────────────────
	srv := backend.New(
		backend.Config{
			Addr:         cfg.HTTP.Addr,
			DefaultVoice: cfg.Kokoro.DefaultVoice,
			Version:      version,
			Commit:       commit,
		},
		backend.Dependencies{
			BookReader:    store,
			RankingStore:  store,
			AudioStore:    store,
			PresignStore:  store,
			ProgressStore: store,
			CoverStore:    store,
			Producer:      store,
			TaskReader:    store,
			SearchIndex:   searchIndex,
			Kokoro:        kokoroClient,
			Log:           log,
		},
	)

	return srv.ListenAndServe(ctx)
}

// ── Helpers ───────────────────────────────────────────────────────────────────

func buildLogger(level string) *slog.Logger {
	var lvl slog.Level
	switch level {
	case "debug":
		lvl = slog.LevelDebug
	case "warn":
		lvl = slog.LevelWarn
	case "error":
		lvl = slog.LevelError
	default:
		lvl = slog.LevelInfo
	}
	return slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: lvl}))
}

// noopKokoro is a no-op implementation used when KOKORO_URL is not set.
// The backend only uses Kokoro for the voice list; audio generation is the
// runner's responsibility. With no URL the built-in fallback list is served.
type noopKokoro struct{}

func (n *noopKokoro) GenerateAudio(_ context.Context, _, _ string) ([]byte, error) {
	return nil, fmt.Errorf("kokoro not configured (KOKORO_URL is empty)")
}

func (n *noopKokoro) ListVoices(_ context.Context) ([]string, error) {
	return nil, nil
}