feat: add Spotify OAuth service with token management

2026-08-18 00:26:29 +00:00 · 2026-02-21 00:21:52 +01:00
parent be7e44e14b
commit 395b2fec8e
2 changed files with 869 additions and 0 deletions
@@ -0,0 +1,443 @@
+// Package spotify provides Spotify OAuth integration and token management
+// for the SoundTouch service, ported from soundcork's Python implementation.
+package spotify
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	// SpotifyAuthorizeURL is the Spotify OAuth authorization endpoint.
+	SpotifyAuthorizeURL = "https://accounts.spotify.com/authorize"
+	// SpotifyTokenURL is the Spotify OAuth token endpoint.
+	SpotifyTokenURL = "https://accounts.spotify.com/api/token"
+	// SpotifyAPIBase is the base URL for the Spotify Web API.
+	SpotifyAPIBase = "https://api.spotify.com/v1"
+	// SpotifyScopes are the OAuth scopes required for speaker playback and user info.
+	SpotifyScopes = "streaming user-read-private user-read-email user-read-playback-state user-modify-playback-state"
+)
+
+// SpotifyAccount represents a stored Spotify account with tokens.
+type SpotifyAccount struct {
+	UserID       string `json:"user_id"`
+	DisplayName  string `json:"display_name"`
+	Email        string `json:"email"`
+	AccessToken  string `json:"access_token"`
+	RefreshToken string `json:"refresh_token"`
+	ExpiresAt    int64  `json:"expires_at"`
+}
+
+// SpotifyService manages Spotify OAuth flow and token lifecycle.
+type SpotifyService struct {
+	clientID     string
+	clientSecret string
+	redirectURI  string
+	dataDir      string
+	mu           sync.RWMutex
+	accounts     map[string]*SpotifyAccount
+
+	// Overridable URLs for testing
+	tokenURL string
+	apiBase  string
+}
+
+// NewSpotifyService creates a new SpotifyService and loads any persisted accounts.
+func NewSpotifyService(clientID, clientSecret, redirectURI, dataDir string) *SpotifyService {
+	s := &SpotifyService{
+		clientID:     clientID,
+		clientSecret: clientSecret,
+		redirectURI:  redirectURI,
+		dataDir:      dataDir,
+		accounts:     make(map[string]*SpotifyAccount),
+		tokenURL:     SpotifyTokenURL,
+		apiBase:      SpotifyAPIBase,
+	}
+	if err := s.load(); err != nil {
+		log.Printf("[Spotify] Failed to load accounts: %v", err)
+	}
+	return s
+}
+
+// BuildAuthorizeURL constructs the Spotify OAuth authorization URL.
+func (s *SpotifyService) BuildAuthorizeURL() string {
+	params := url.Values{
+		"client_id":     {s.clientID},
+		"response_type": {"code"},
+		"redirect_uri":  {s.redirectURI},
+		"scope":         {SpotifyScopes},
+	}
+	return SpotifyAuthorizeURL + "?" + params.Encode()
+}
+
+// ExchangeCodeAndStore exchanges an authorization code for tokens,
+// fetches the user profile, and stores the account.
+func (s *SpotifyService) ExchangeCodeAndStore(code string) error {
+	// Exchange code for tokens
+	tokenResp, err := s.exchangeCode(code)
+	if err != nil {
+		return fmt.Errorf("token exchange: %w", err)
+	}
+
+	accessToken, _ := tokenResp["access_token"].(string)
+	refreshToken, _ := tokenResp["refresh_token"].(string)
+	expiresIn, _ := tokenResp["expires_in"].(float64)
+	if expiresIn == 0 {
+		expiresIn = 3600
+	}
+
+	// Fetch user profile
+	profile, err := s.getUserProfile(accessToken)
+	if err != nil {
+		return fmt.Errorf("fetch profile: %w", err)
+	}
+
+	userID, _ := profile["id"].(string)
+	displayName, _ := profile["display_name"].(string)
+	email, _ := profile["email"].(string)
+
+	account := &SpotifyAccount{
+		UserID:       userID,
+		DisplayName:  displayName,
+		Email:        email,
+		AccessToken:  accessToken,
+		RefreshToken: refreshToken,
+		ExpiresAt:    time.Now().Unix() + int64(expiresIn),
+	}
+
+	s.mu.Lock()
+	s.accounts[userID] = account
+	s.mu.Unlock()
+
+	if err := s.save(); err != nil {
+		return fmt.Errorf("save accounts: %w", err)
+	}
+
+	log.Printf("[Spotify] Account linked: %s (%s)", displayName, userID)
+	return nil
+}
+
+func (s *SpotifyService) exchangeCode(code string) (map[string]interface{}, error) {
+	data := url.Values{
+		"grant_type":   {"authorization_code"},
+		"code":         {code},
+		"redirect_uri": {s.redirectURI},
+	}
+
+	req, err := http.NewRequest(http.MethodPost, s.tokenURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.SetBasicAuth(s.clientID, s.clientSecret)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("token request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("token exchange failed (%d): %s", resp.StatusCode, string(body))
+	}
+
+	var result map[string]interface{}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, fmt.Errorf("parse response: %w", err)
+	}
+	return result, nil
+}
+
+func (s *SpotifyService) getUserProfile(accessToken string) (map[string]interface{}, error) {
+	req, err := http.NewRequest(http.MethodGet, s.apiBase+"/me", nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("profile request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("profile fetch failed (%d): %s", resp.StatusCode, string(body))
+	}
+
+	var result map[string]interface{}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, fmt.Errorf("parse profile: %w", err)
+	}
+	return result, nil
+}
+
+// RefreshAccessToken refreshes the access token for the given account.
+func (s *SpotifyService) RefreshAccessToken(account *SpotifyAccount) error {
+	data := url.Values{
+		"grant_type":    {"refresh_token"},
+		"refresh_token": {account.RefreshToken},
+	}
+
+	req, err := http.NewRequest(http.MethodPost, s.tokenURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.SetBasicAuth(s.clientID, s.clientSecret)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("refresh request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("token refresh failed (%d): %s", resp.StatusCode, string(body))
+	}
+
+	var result map[string]interface{}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return fmt.Errorf("parse response: %w", err)
+	}
+
+	s.mu.Lock()
+	account.AccessToken, _ = result["access_token"].(string)
+	expiresIn, _ := result["expires_in"].(float64)
+	if expiresIn == 0 {
+		expiresIn = 3600
+	}
+	account.ExpiresAt = time.Now().Unix() + int64(expiresIn)
+	if newRefresh, ok := result["refresh_token"].(string); ok && newRefresh != "" {
+		account.RefreshToken = newRefresh
+	}
+	s.mu.Unlock()
+
+	if err := s.save(); err != nil {
+		return fmt.Errorf("save accounts: %w", err)
+	}
+
+	return nil
+}
+
+// GetFreshToken returns a valid access token and username, refreshing if needed.
+func (s *SpotifyService) GetFreshToken() (accessToken, username string, err error) {
+	s.mu.RLock()
+	if len(s.accounts) == 0 {
+		s.mu.RUnlock()
+		return "", "", fmt.Errorf("no Spotify accounts linked")
+	}
+
+	// Get the first account
+	var account *SpotifyAccount
+	for _, a := range s.accounts {
+		account = a
+		break
+	}
+	s.mu.RUnlock()
+
+	// Check if token needs refresh (expired or within 60s of expiry)
+	if account.ExpiresAt < time.Now().Unix()+60 {
+		if err := s.RefreshAccessToken(account); err != nil {
+			return "", "", fmt.Errorf("refresh token: %w", err)
+		}
+	}
+
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return account.AccessToken, account.UserID, nil
+}
+
+// GetAccounts returns a copy of all accounts with tokens stripped for API responses.
+func (s *SpotifyService) GetAccounts() []SpotifyAccount {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	result := make([]SpotifyAccount, 0, len(s.accounts))
+	for _, a := range s.accounts {
+		result = append(result, SpotifyAccount{
+			UserID:      a.UserID,
+			DisplayName: a.DisplayName,
+			Email:       a.Email,
+			ExpiresAt:   a.ExpiresAt,
+			// AccessToken and RefreshToken deliberately omitted
+		})
+	}
+	return result
+}
+
+// ResolveEntity resolves a Spotify URI to a name and image URL.
+func (s *SpotifyService) ResolveEntity(uri string) (name, imageURL string, err error) {
+	entityType, entityID, err := parseSpotifyURI(uri)
+	if err != nil {
+		return "", "", err
+	}
+
+	accessToken, _, err := s.GetFreshToken()
+	if err != nil {
+		return "", "", fmt.Errorf("get token: %w", err)
+	}
+
+	apiURL := fmt.Sprintf("%s/%s/%s", s.apiBase, entityType, entityID)
+	req, err := http.NewRequest(http.MethodGet, apiURL, nil)
+	if err != nil {
+		return "", "", err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", "", fmt.Errorf("API request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", "", fmt.Errorf("read response: %w", err)
+	}
+
+	if resp.StatusCode == http.StatusNotFound {
+		return "", "", fmt.Errorf("Spotify entity not found")
+	}
+	if resp.StatusCode != http.StatusOK {
+		return "", "", fmt.Errorf("Spotify API error (%d): %s", resp.StatusCode, string(body))
+	}
+
+	var data map[string]interface{}
+	if err := json.Unmarshal(body, &data); err != nil {
+		return "", "", fmt.Errorf("parse response: %w", err)
+	}
+
+	name, _ = data["name"].(string)
+	if name == "" {
+		name = "Unknown"
+	}
+
+	// Extract image URL — location varies by entity type
+	imageURL = extractImageURL(data, entityType)
+
+	return name, imageURL, nil
+}
+
+// extractImageURL extracts the first image URL from a Spotify API response.
+// For tracks, images are stored on the album object.
+func extractImageURL(data map[string]interface{}, entityType string) string {
+	images, _ := data["images"].([]interface{})
+	if len(images) == 0 && entityType == "tracks" {
+		// Tracks store images on the album
+		album, _ := data["album"].(map[string]interface{})
+		if album != nil {
+			images, _ = album["images"].([]interface{})
+		}
+	}
+
+	if len(images) > 0 {
+		if img, ok := images[0].(map[string]interface{}); ok {
+			url, _ := img["url"].(string)
+			return url
+		}
+	}
+	return ""
+}
+
+// parseSpotifyURI parses a Spotify URI like "spotify:track:abc" into
+// the pluralized API type ("tracks") and ID ("abc").
+func parseSpotifyURI(uri string) (entityType, entityID string, err error) {
+	parts := strings.Split(uri, ":")
+	if len(parts) != 3 || parts[0] != "spotify" {
+		return "", "", fmt.Errorf("invalid Spotify URI format: %s", uri)
+	}
+
+	typ := parts[1]
+	id := parts[2]
+
+	validTypes := map[string]string{
+		"track":    "tracks",
+		"album":    "albums",
+		"playlist": "playlists",
+		"artist":   "artists",
+	}
+
+	plural, ok := validTypes[typ]
+	if !ok {
+		return "", "", fmt.Errorf("unsupported Spotify entity type: %s", typ)
+	}
+
+	return plural, id, nil
+}
+
+// save persists accounts to disk as JSON.
+func (s *SpotifyService) save() error {
+	s.mu.RLock()
+	data := make(map[string]*SpotifyAccount, len(s.accounts))
+	for k, v := range s.accounts {
+		data[k] = v
+	}
+	s.mu.RUnlock()
+
+	dir := filepath.Join(s.dataDir, "spotify")
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return fmt.Errorf("create directory: %w", err)
+	}
+
+	jsonData, err := json.MarshalIndent(data, "", "  ")
+	if err != nil {
+		return fmt.Errorf("marshal accounts: %w", err)
+	}
+
+	path := filepath.Join(dir, "accounts.json")
+	if err := os.WriteFile(path, jsonData, 0600); err != nil {
+		return fmt.Errorf("write file: %w", err)
+	}
+
+	return nil
+}
+
+// load reads persisted accounts from disk.
+func (s *SpotifyService) load() error {
+	path := filepath.Join(s.dataDir, "spotify", "accounts.json")
+
+	jsonData, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil // No accounts file yet, not an error
+		}
+		return fmt.Errorf("read file: %w", err)
+	}
+
+	var accounts map[string]*SpotifyAccount
+	if err := json.Unmarshal(jsonData, &accounts); err != nil {
+		return fmt.Errorf("unmarshal accounts: %w", err)
+	}
+
+	s.mu.Lock()
+	s.accounts = accounts
+	s.mu.Unlock()
+
+	log.Printf("[Spotify] Loaded %d account(s)", len(accounts))
+	return nil
+}
@@ -0,0 +1,426 @@
+package spotify
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestBuildAuthorizeURL(t *testing.T) {
+	svc := NewSpotifyService("test-client-id", "test-secret", "http://localhost/callback", t.TempDir())
+
+	url := svc.BuildAuthorizeURL()
+
+	if !strings.Contains(url, "client_id=test-client-id") {
+		t.Errorf("URL should contain client_id, got: %s", url)
+	}
+	if !strings.Contains(url, "redirect_uri=") {
+		t.Errorf("URL should contain redirect_uri, got: %s", url)
+	}
+	if !strings.Contains(url, "scope=") {
+		t.Errorf("URL should contain scope, got: %s", url)
+	}
+	if !strings.Contains(url, "response_type=code") {
+		t.Errorf("URL should contain response_type=code, got: %s", url)
+	}
+	if !strings.HasPrefix(url, SpotifyAuthorizeURL) {
+		t.Errorf("URL should start with %s, got: %s", SpotifyAuthorizeURL, url)
+	}
+}
+
+func TestGetAccountsStripsTokens(t *testing.T) {
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", t.TempDir())
+
+	// Manually add an account with tokens
+	svc.mu.Lock()
+	svc.accounts["user1"] = &SpotifyAccount{
+		UserID:       "user1",
+		DisplayName:  "Test User",
+		Email:        "test@example.com",
+		AccessToken:  "secret-access-token",
+		RefreshToken: "secret-refresh-token",
+		ExpiresAt:    time.Now().Add(1 * time.Hour).Unix(),
+	}
+	svc.mu.Unlock()
+
+	accounts := svc.GetAccounts()
+
+	if len(accounts) != 1 {
+		t.Fatalf("expected 1 account, got %d", len(accounts))
+	}
+
+	if accounts[0].AccessToken != "" {
+		t.Errorf("AccessToken should be stripped, got: %s", accounts[0].AccessToken)
+	}
+	if accounts[0].RefreshToken != "" {
+		t.Errorf("RefreshToken should be stripped, got: %s", accounts[0].RefreshToken)
+	}
+	if accounts[0].UserID != "user1" {
+		t.Errorf("UserID should be preserved, got: %s", accounts[0].UserID)
+	}
+	if accounts[0].DisplayName != "Test User" {
+		t.Errorf("DisplayName should be preserved, got: %s", accounts[0].DisplayName)
+	}
+}
+
+func TestGetFreshTokenRefreshesExpired(t *testing.T) {
+	// Set up a mock Spotify token endpoint
+	tokenServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			t.Errorf("expected POST, got %s", r.Method)
+		}
+		if err := r.ParseForm(); err != nil {
+			t.Fatal(err)
+		}
+		if r.Form.Get("grant_type") != "refresh_token" {
+			t.Errorf("expected grant_type=refresh_token, got %s", r.Form.Get("grant_type"))
+		}
+		if r.Form.Get("refresh_token") != "my-refresh-token" {
+			t.Errorf("expected refresh_token=my-refresh-token, got %s", r.Form.Get("refresh_token"))
+		}
+
+		// Verify Basic Auth
+		user, pass, ok := r.BasicAuth()
+		if !ok || user != "cid" || pass != "csecret" {
+			t.Errorf("expected Basic Auth cid:csecret, got %s:%s (ok=%v)", user, pass, ok)
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"access_token":  "new-access-token",
+			"token_type":    "Bearer",
+			"expires_in":    3600,
+			"refresh_token": "new-refresh-token",
+		})
+	}))
+	defer tokenServer.Close()
+
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", t.TempDir())
+
+	// Override the token URL for testing
+	svc.tokenURL = tokenServer.URL
+
+	// Add an account with an expired token
+	svc.mu.Lock()
+	svc.accounts["user1"] = &SpotifyAccount{
+		UserID:       "user1",
+		DisplayName:  "Test User",
+		AccessToken:  "old-expired-token",
+		RefreshToken: "my-refresh-token",
+		ExpiresAt:    time.Now().Add(-1 * time.Hour).Unix(), // expired
+	}
+	svc.mu.Unlock()
+
+	accessToken, username, err := svc.GetFreshToken()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if accessToken != "new-access-token" {
+		t.Errorf("expected new-access-token, got %s", accessToken)
+	}
+	if username != "user1" {
+		t.Errorf("expected user1, got %s", username)
+	}
+
+	// Verify the account was updated
+	svc.mu.RLock()
+	account := svc.accounts["user1"]
+	svc.mu.RUnlock()
+
+	if account.RefreshToken != "new-refresh-token" {
+		t.Errorf("refresh token should be updated, got %s", account.RefreshToken)
+	}
+}
+
+func TestResolveEntityParsesURI(t *testing.T) {
+	tests := []struct {
+		uri          string
+		expectedType string
+		expectedID   string
+		shouldErr    bool
+	}{
+		{"spotify:track:abc123", "tracks", "abc123", false},
+		{"spotify:album:xyz789", "albums", "xyz789", false},
+		{"spotify:playlist:pl1", "playlists", "pl1", false},
+		{"spotify:artist:ar1", "artists", "ar1", false},
+		{"invalid-uri", "", "", true},
+		{"spotify:invalid_type:id", "", "", true},
+		{"spotify:track", "", "", true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.uri, func(t *testing.T) {
+			entityType, entityID, err := parseSpotifyURI(tc.uri)
+			if tc.shouldErr {
+				if err == nil {
+					t.Errorf("expected error for URI %s", tc.uri)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error for URI %s: %v", tc.uri, err)
+			}
+			if entityType != tc.expectedType {
+				t.Errorf("expected type %s, got %s", tc.expectedType, entityType)
+			}
+			if entityID != tc.expectedID {
+				t.Errorf("expected id %s, got %s", tc.expectedID, entityID)
+			}
+		})
+	}
+}
+
+func TestResolveEntityFetchesFromAPI(t *testing.T) {
+	// Mock Spotify API
+	apiServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Check Authorization header
+		auth := r.Header.Get("Authorization")
+		if auth != "Bearer fresh-token" {
+			t.Errorf("expected Bearer fresh-token, got %s", auth)
+		}
+
+		switch r.URL.Path {
+		case "/tracks/abc123":
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"name": "Test Track",
+				"album": map[string]interface{}{
+					"images": []map[string]interface{}{
+						{"url": "http://img.example.com/track.jpg"},
+					},
+				},
+			})
+		case "/albums/xyz789":
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"name": "Test Album",
+				"images": []map[string]interface{}{
+					{"url": "http://img.example.com/album.jpg"},
+				},
+			})
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer apiServer.Close()
+
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", t.TempDir())
+	svc.apiBase = apiServer.URL
+
+	// Add a non-expired account
+	svc.mu.Lock()
+	svc.accounts["user1"] = &SpotifyAccount{
+		UserID:       "user1",
+		AccessToken:  "fresh-token",
+		RefreshToken: "refresh",
+		ExpiresAt:    time.Now().Add(1 * time.Hour).Unix(),
+	}
+	svc.mu.Unlock()
+
+	// Test track (images come from album)
+	name, imageURL, err := svc.ResolveEntity("spotify:track:abc123")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if name != "Test Track" {
+		t.Errorf("expected Test Track, got %s", name)
+	}
+	if imageURL != "http://img.example.com/track.jpg" {
+		t.Errorf("expected track image URL, got %s", imageURL)
+	}
+
+	// Test album (images at top level)
+	name, imageURL, err = svc.ResolveEntity("spotify:album:xyz789")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if name != "Test Album" {
+		t.Errorf("expected Test Album, got %s", name)
+	}
+	if imageURL != "http://img.example.com/album.jpg" {
+		t.Errorf("expected album image URL, got %s", imageURL)
+	}
+}
+
+func TestSaveAndLoad(t *testing.T) {
+	dir := t.TempDir()
+
+	// Create and populate
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", dir)
+	svc.mu.Lock()
+	svc.accounts["user1"] = &SpotifyAccount{
+		UserID:       "user1",
+		DisplayName:  "Test User",
+		Email:        "test@example.com",
+		AccessToken:  "at",
+		RefreshToken: "rt",
+		ExpiresAt:    1234567890,
+	}
+	svc.accounts["user2"] = &SpotifyAccount{
+		UserID:       "user2",
+		DisplayName:  "User Two",
+		Email:        "two@example.com",
+		AccessToken:  "at2",
+		RefreshToken: "rt2",
+		ExpiresAt:    9876543210,
+	}
+	svc.mu.Unlock()
+
+	// Save
+	if err := svc.save(); err != nil {
+		t.Fatalf("save failed: %v", err)
+	}
+
+	// Verify file exists
+	accountsFile := filepath.Join(dir, "spotify", "accounts.json")
+	if _, err := os.Stat(accountsFile); os.IsNotExist(err) {
+		t.Fatal("accounts.json was not created")
+	}
+
+	// Load into new service
+	svc2 := NewSpotifyService("cid", "csecret", "http://localhost/cb", dir)
+
+	svc2.mu.RLock()
+	defer svc2.mu.RUnlock()
+
+	if len(svc2.accounts) != 2 {
+		t.Fatalf("expected 2 accounts after load, got %d", len(svc2.accounts))
+	}
+
+	u1, ok := svc2.accounts["user1"]
+	if !ok {
+		t.Fatal("user1 not found after load")
+	}
+	if u1.DisplayName != "Test User" {
+		t.Errorf("expected Test User, got %s", u1.DisplayName)
+	}
+	if u1.AccessToken != "at" {
+		t.Errorf("expected at, got %s", u1.AccessToken)
+	}
+	if u1.ExpiresAt != 1234567890 {
+		t.Errorf("expected ExpiresAt 1234567890, got %d", u1.ExpiresAt)
+	}
+}
+
+func TestExchangeCodeAndStore(t *testing.T) {
+	// Mock token endpoint
+	tokenServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := r.ParseForm(); err != nil {
+			t.Fatal(err)
+		}
+
+		switch r.Form.Get("grant_type") {
+		case "authorization_code":
+			if r.Form.Get("code") != "test-auth-code" {
+				t.Errorf("expected code=test-auth-code, got %s", r.Form.Get("code"))
+			}
+			user, pass, ok := r.BasicAuth()
+			if !ok || user != "cid" || pass != "csecret" {
+				t.Errorf("bad Basic Auth: %s:%s ok=%v", user, pass, ok)
+			}
+
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"access_token":  "new-at",
+				"refresh_token": "new-rt",
+				"expires_in":    3600,
+			})
+		default:
+			t.Errorf("unexpected grant_type: %s", r.Form.Get("grant_type"))
+			http.Error(w, "bad request", 400)
+		}
+	}))
+	defer tokenServer.Close()
+
+	// Mock profile endpoint
+	profileServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		auth := r.Header.Get("Authorization")
+		if auth != "Bearer new-at" {
+			t.Errorf("expected Bearer new-at, got %s", auth)
+		}
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"id":           "spotify-user-123",
+			"display_name": "Spotify User",
+			"email":        "user@spotify.com",
+		})
+	}))
+	defer profileServer.Close()
+
+	dir := t.TempDir()
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", dir)
+	svc.tokenURL = tokenServer.URL
+	svc.apiBase = profileServer.URL
+
+	err := svc.ExchangeCodeAndStore("test-auth-code")
+	if err != nil {
+		t.Fatalf("ExchangeCodeAndStore failed: %v", err)
+	}
+
+	// Verify account stored
+	svc.mu.RLock()
+	account, ok := svc.accounts["spotify-user-123"]
+	svc.mu.RUnlock()
+
+	if !ok {
+		t.Fatal("account not found after exchange")
+	}
+	if account.DisplayName != "Spotify User" {
+		t.Errorf("expected Spotify User, got %s", account.DisplayName)
+	}
+	if account.Email != "user@spotify.com" {
+		t.Errorf("expected user@spotify.com, got %s", account.Email)
+	}
+	if account.AccessToken != "new-at" {
+		t.Errorf("expected new-at, got %s", account.AccessToken)
+	}
+	if account.RefreshToken != "new-rt" {
+		t.Errorf("expected new-rt, got %s", account.RefreshToken)
+	}
+
+	// Verify saved to disk
+	accountsFile := filepath.Join(dir, "spotify", "accounts.json")
+	data, err := os.ReadFile(accountsFile)
+	if err != nil {
+		t.Fatalf("failed to read accounts file: %v", err)
+	}
+	if !strings.Contains(string(data), "spotify-user-123") {
+		t.Error("accounts file should contain the user ID")
+	}
+}
+
+func TestGetFreshTokenNoAccounts(t *testing.T) {
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", t.TempDir())
+
+	_, _, err := svc.GetFreshToken()
+	if err == nil {
+		t.Error("expected error when no accounts exist")
+	}
+}
+
+func TestGetFreshTokenNotExpired(t *testing.T) {
+	svc := NewSpotifyService("cid", "csecret", "http://localhost/cb", t.TempDir())
+
+	svc.mu.Lock()
+	svc.accounts["user1"] = &SpotifyAccount{
+		UserID:       "user1",
+		AccessToken:  "valid-token",
+		RefreshToken: "rt",
+		ExpiresAt:    time.Now().Add(1 * time.Hour).Unix(),
+	}
+	svc.mu.Unlock()
+
+	token, username, err := svc.GetFreshToken()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if token != "valid-token" {
+		t.Errorf("expected valid-token, got %s", token)
+	}
+	if username != "user1" {
+		t.Errorf("expected user1, got %s", username)
+	}
+}