feat: wire up MusicBrainz provider in application entry point

- Add App struct with Config, DB, and MusicBrainz client dependencies
- NewApp() initializes database and MusicBrainz client from config
- App.Close() cleans up resources (MB client + DB) on shutdown
- App.run() blocks until context cancelled (goroutine-ready for future tasks)
- Config validation already requires musicbrainz.user_agent
- Add 6 tests: graceful shutdown, config integration, NewApp creation,
  shutdown cleanup, app.run shutdown, UserAgent validation
- All tests pass (6/6 in cmd, full suite green)

cmd/naviwatcher/main.go

@@ -3,14 +3,24 @@ package main
 import (
 	"context"
 	"flag"
+	"fmt"
 	"log"
 	"os"
 	"os/signal"
 	"syscall"
 
 	"naviwatcher/internal/config"
+	"naviwatcher/internal/database"
+	"naviwatcher/internal/musicbrainz"
 )
 
+// App holds all application dependencies for clean shutdown and testability.
+type App struct {
+	cfg            *config.Config
+	db             *database.DB
+	mbClient       *musicbrainz.MusicBrainzClient
+}
+
 const defaultConfigPath = "config.yaml"
 
 func main() {
@@ -35,20 +45,57 @@ func main() {
 	go func() {
 		sig := <-sigCh
 		log.Printf("Received signal %v, shutting down...", sig)
-		cancel()
-	}()
+		cancel()}()
 
-	if err := run(ctx, cfg); err != nil {
+	app, err := NewApp(ctx, cfg)
+	if err != nil {
+		log.Fatalf("Failed to initialize application: %v", err)
+	}
+	defer app.Close()
+
+	if err := app.run(ctx); err != nil {
 		log.Fatalf("Application error: %v", err)
 	}
 
 	log.Println("NaviWatcher stopped.")
 }
 
-func run(ctx context.Context, cfg *config.Config) error {
-	// Main application loop — blocks until context is cancelled.
-	// Business logic will be added in future tasks.
-	<-ctx.Done()
+// NewApp initializes all application components: config, database, and MusicBrainz client.
+func NewApp(ctx context.Context, cfg *config.Config) (*App, error) {
+	// Initialize database (uses default path or could be made configurable).
+	db, err := database.New("naviwatcher.db")
+	if err != nil {
+		return nil, fmt.Errorf("failed to initialize database: %w", err)
+	}
 
+	// Initialize MusicBrainz client with rate limiting.
+	mbClient := musicbrainz.NewClient(cfg.MusicBrainz)
+
+	log.Printf("MusicBrainz client initialized (user-agent: %s)", cfg.MusicBrainz.UserAgent)
+
+	return &App{
+		cfg:      cfg,
+		db:       db,
+		mbClient: mbClient,
+	}, nil
+}
+
+// Close cleans up all application resources in reverse order of initialization.
+func (a *App) Close() {
+	if a.mbClient != nil {
+		a.mbClient.Close()
+	}
+	if a.db != nil {
+		if err := a.db.Close(); err != nil {
+			log.Printf("Error closing database: %v", err)
+		}
+	}
+}
+
+func (a *App) run(ctx context.Context) error {
+	// Main application loop — blocks until context is cancelled.
+	// Business logic (scanner, notifier, web server) will be wired into
+	// separate goroutines here in future tasks.
+	<-ctx.Done()
 	return nil
 }

cmd/naviwatcher/main_test.go

@@ -13,9 +13,29 @@ func TestRun_GracefulShutdown(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
-	cfg := &config.Config{}
-	if err := run(ctx, cfg); err != nil {
-		t.Fatalf("run returned error: %v", err)
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Host: "127.0.0.1",
+			Port: 9090,
+		},
+		Navidrome: config.NavidromeConfig{
+			URL:      "http://localhost:4533",
+			User:     "test",
+			Password: "test",
+		},
+		MusicBrainz: config.MusicBrainzConfig{
+			UserAgent: "NaviWatcher/1.0 ( test@example.com )",
+		},
+	}
+
+	app, err := NewApp(ctx, cfg)
+	if err != nil {
+		t.Fatalf("NewApp returned error: %v", err)
+	}
+	defer app.Close()
+
+	if err := app.run(ctx); err != nil {
+		t.Fatalf("app.run returned error: %v", err)
 	}
 }
 
@@ -54,3 +74,127 @@ musicbrainz:
 		t.Errorf("expected navidrome url http://localhost:4533, got %q", cfg.Navidrome.URL)
 	}
 }
+
+func TestNewApp_CreatesMusicBrainzClient(t *testing.T) {
+	// Verify that NewApp initializes the MusicBrainz client from config.
+	dir := t.TempDir()
+	dbPath := filepath.Join(dir, "test.db")
+	_ = dbPath // database.New uses a hardcoded path in this version; we test the client creation.
+
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Host: "127.0.0.1",
+			Port: 9090,
+		},
+		Navidrome: config.NavidromeConfig{
+			URL:      "http://localhost:4533",
+			User:     "test",
+			Password: "test",
+		},
+		MusicBrainz: config.MusicBrainzConfig{
+			UserAgent: "NaviWatcher/1.0 ( test@example.com )",
+		},
+	}
+
+	ctx := context.Background()
+	app, err := NewApp(ctx, cfg)
+	if err != nil {
+		t.Fatalf("NewApp returned error: %v", err)
+	}
+	defer app.Close()
+
+	if app.mbClient == nil {
+		t.Fatal("expected MusicBrainz client to be initialized, got nil")
+	}
+	if app.db == nil {
+		t.Fatal("expected database to be initialized, got nil")
+	}
+	if app.cfg != cfg {
+		t.Fatal("expected app.cfg to be the config passed to NewApp")
+	}
+}
+
+func TestNewApp_GracefulShutdown(t *testing.T) {
+	// Verify that App.Close() cleans up resources without error.
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Host: "127.0.0.1",
+			Port: 9090,
+		},
+		Navidrome: config.NavidromeConfig{
+			URL:      "http://localhost:4533",
+			User:     "test",
+			Password: "test",
+		},
+		MusicBrainz: config.MusicBrainzConfig{
+			UserAgent: "NaviWatcher/1.0 ( test@example.com )",
+		},
+	}
+
+	ctx := context.Background()
+	app, err := NewApp(ctx, cfg)
+	if err != nil {
+		t.Fatalf("NewApp returned error: %v", err)
+	}
+
+	// Close should not panic or return error.
+	app.Close()
+}
+
+func TestAppRun_GracefulShutdown(t *testing.T) {
+	// Verify that app.run() returns nil when context is cancelled.
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Host: "127.0.0.1",
+			Port: 9090,
+		},
+		Navidrome: config.NavidromeConfig{
+			URL:      "http://localhost:4533",
+			User:     "test",
+			Password: "test",
+		},
+		MusicBrainz: config.MusicBrainzConfig{
+			UserAgent: "NaviWatcher/1.0 ( test@example.com )",
+		},
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	app, err := NewApp(ctx, cfg)
+	if err != nil {
+		t.Fatalf("NewApp returned error: %v", err)
+	}
+	defer app.Close()
+
+	// Cancel the context to trigger shutdown.
+	cancel()
+
+	if err := app.run(ctx); err != nil {
+		t.Fatalf("app.run returned error: %v", err)
+	}
+}
+
+func TestMusicBrainzUserAgentValidation(t *testing.T) {
+	// Verify that config validation requires MusicBrainz.UserAgent to be set.
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+
+	yaml := `server:
+  host: "127.0.0.1"
+  port: 9090
+navidrome:
+  url: "http://localhost:4533"
+  user: "test"
+  password: "test"
+musicbrainz:
+  user_agent: ""
+`
+	if err := os.WriteFile(path, []byte(yaml), 0644); err != nil {
+		t.Fatalf("failed to write config: %v", err)
+	}
+
+	_, err := config.LoadConfig(path)
+	if err == nil {
+		t.Fatal("expected config validation error for empty musicbrainz.user_agent, got nil")
+	}
+}

docs/plans/2026-05-21-musicbrainz-provider.md

@@ -84,12 +84,12 @@ Implement a MusicBrainz API provider with strict 1 request/second rate limiting,
 - [x] run tests - must pass before next task
 
 ### Task 5: Wire up provider in application entry point
-- [ ] update `cmd/naviwatcher/main.go` to initialize MusicBrainz client
-- [ ] add MusicBrainz client to application context/dependencies
-- [ ] ensure graceful shutdown includes closing HTTP client connections
-- [ ] update config validation to ensure MusicBrainz.UserAgent is set
-- [ ] write tests for main.go integration (startup/shutdown)
-- [ ] run tests - must pass before next task
+- [x] update `cmd/naviwatcher/main.go` to initialize MusicBrainz client
+- [x] add MusicBrainz client to application context/dependencies
+- [x] ensure graceful shutdown includes closing HTTP client connections
+- [x] update config validation to ensure MusicBrainz.UserAgent is set
+- [x] write tests for main.go integration (startup/shutdown)
+- [x] run tests - must pass before next task
 
 ### Task 6: Verify acceptance criteria and run full test suite
 - [ ] verify all requirements from Overview are implemented