NaviWatcher/internal/musicbrainz/client_test.go

package musicbrainz

import (
	"context"
	"net/http"
	"net/http/httptest"
	"sync"
	"testing"
	"time"

	"golang.org/x/time/rate"
	"naviwatcher/internal/config"
)

func TestNewClient_ValidConfig(t *testing.T) {
	cfg := config.MusicBrainzConfig{
		UserAgent: "naviwatcher/0.1.0 (test@example.com)",
	}

	client := NewClient(cfg)

	if client == nil {
		t.Fatal("NewClient() returned nil client")
	}

	if client.httpClient == nil {
		t.Fatal("NewClient() returned client with nil http.Client")
	}

	if client.userAgent != cfg.UserAgent {
		t.Errorf("NewClient().userAgent = %q, want %q", client.userAgent, cfg.UserAgent)
	}

	expectedBaseURL := "https://musicbrainz.org/ws/2"
	if client.baseURL != expectedBaseURL {
		t.Errorf("NewClient().baseURL = %q, want %q", client.baseURL, expectedBaseURL)
	}

	if client.rateLimiter == nil {
		t.Fatal("NewClient() returned client with nil rate limiter")
	}
}

func TestDoGet_Success(t *testing.T) {
	var mu sync.Mutex
	var gotUserAgent, gotAccept string

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		mu.Lock()
		gotUserAgent = r.Header.Get("User-Agent")
		gotAccept = r.Header.Get("Accept")
		mu.Unlock()
		w.Header().Set("Content-Type", "application/xml")
		w.Write([]byte(`<metadata><test>ok</test></metadata>`))
	}))
	defer server.Close()

	cfg := config.MusicBrainzConfig{
		UserAgent: "naviwatcher/0.1.0 (test@example.com)",
	}

	rl := rate.NewLimiter(rate.Limit(1000), 1000) // high rate to avoid blocking in tests
	client := &MusicBrainzClient{
		httpClient:  server.Client(),
		userAgent:   cfg.UserAgent,
		baseURL:     server.URL,
		rateLimiter: rl,
	}

	body, err := client.doGet(context.Background(), "/test")
	if err != nil {
		t.Fatalf("doGet() error = %v", err)
	}

	if string(body) != `<metadata><test>ok</test></metadata>` {
		t.Errorf("doGet() body = %q", string(body))
	}

	mu.Lock()
	if gotUserAgent == "" {
		t.Error("doGet() request missing User-Agent header")
	}
	if gotAccept != "application/xml" {
		t.Errorf("doGet() Accept header = %q, want %q", gotAccept, "application/xml")
	}
	mu.Unlock()
}

func TestDoGet_Non200Status(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte("Rate limit exceeded"))
	}))
	defer server.Close()

	cfg := config.MusicBrainzConfig{
		UserAgent: "naviwatcher/0.1.0 (test@example.com)",
	}

	rl := rate.NewLimiter(rate.Limit(1000), 1000)
	client := &MusicBrainzClient{
		httpClient:  server.Client(),
		userAgent:   cfg.UserAgent,
		baseURL:     server.URL,
		rateLimiter: rl,
	}

	_, err := client.doGet(context.Background(), "/test")
	if err == nil {
		t.Fatal("doGet() expected error for non-200 status, got nil")
	}
}

func TestDoGet_ServerUnreachable(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
	server.Close()

	cfg := config.MusicBrainzConfig{
		UserAgent: "naviwatcher/0.1.0 (test@example.com)",
	}

	rl := rate.NewLimiter(rate.Limit(1000), 1000)
	client := &MusicBrainzClient{
		httpClient:  server.Client(),
		userAgent:   cfg.UserAgent,
		baseURL:     server.URL,
		rateLimiter: rl,
	}

	_, err := client.doGet(context.Background(), "/test")
	if err == nil {
		t.Fatal("doGet() expected error for unreachable server, got nil")
	}
}

func TestDoGet_ContextCancellation(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte(`<metadata><test>ok</test></metadata>`))
	}))
	defer server.Close()

	cfg := config.MusicBrainzConfig{
		UserAgent: "naviwatcher/0.1.0 (test@example.com)",
	}

	// Use a rate limiter with 0 burst to force blocking on Wait
	rl := rate.NewLimiter(rate.Limit(0), 0)
	client := &MusicBrainzClient{
		httpClient:  server.Client(),
		userAgent:   cfg.UserAgent,
		baseURL:     server.URL,
		rateLimiter: rl,
	}

	ctx, cancel := context.WithCancel(context.Background())
	cancel() // cancel immediately

	_, err := client.doGet(ctx, "/test")
	if err == nil {
		t.Fatal("doGet() expected error for cancelled context, got nil")
	}
}

func TestRateLimiter_OnePerSecond(t *testing.T) {
	// Verify that the rate limiter enforces approximately 1 request per second
	rl := rate.NewLimiter(rate.Limit(1), 1)

	// First request should be immediate (burst of 1)
	start := time.Now()
	if err := rl.Wait(context.Background()); err != nil {
		t.Fatalf("first Wait() error: %v", err)
	}
	elapsed := time.Since(start)
	if elapsed > 200*time.Millisecond {
		t.Errorf("first Wait() took %v, expected near-instant", elapsed)
	}

	// Second request should block for approximately 1 second
	start = time.Now()
	if err := rl.Wait(context.Background()); err != nil {
		t.Fatalf("second Wait() error: %v", err)
	}
	elapsed = time.Since(start)
	if elapsed < 800*time.Millisecond {
		t.Errorf("second Wait() took %v, expected at least ~1s", elapsed)
	}
	if elapsed > 2*time.Second {
		t.Errorf("second Wait() took %v, expected less than 2s", elapsed)
	}
}

func TestRateLimiter_BurstBehavior(t *testing.T) {
	// With burst=1, the first request should be immediate
	rl := rate.NewLimiter(rate.Limit(1), 1)

	start := time.Now()
	rl.Wait(context.Background())
	elapsed := time.Since(start)

	if elapsed > 200*time.Millisecond {
		t.Errorf("burst Wait() took %v, expected near-instant", elapsed)
	}
}