SpotiFLAC/backend/songlink.go

package backend

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"time"
)

type SongLinkClient struct {
	client           *http.Client
	lastAPICallTime  time.Time
	apiCallCount     int
	apiCallResetTime time.Time
}

type SongLinkURLs struct {
	TidalURL  string `json:"tidal_url"`
	DeezerURL string `json:"deezer_url"`
	AmazonURL string `json:"amazon_url"`
}

func NewSongLinkClient() *SongLinkClient {
	return &SongLinkClient{
		client: &http.Client{
			Timeout: 30 * time.Second,
		},
		apiCallResetTime: time.Now(),
	}
}

func (s *SongLinkClient) GetAllURLsFromSpotify(spotifyTrackID string) (*SongLinkURLs, error) {
	// Rate limiting: max 10 requests per minute (song.link API limit)
	now := time.Now()
	if now.Sub(s.apiCallResetTime) >= time.Minute {
		s.apiCallCount = 0
		s.apiCallResetTime = now
	}

	// If we've hit the limit, wait until the next minute
	if s.apiCallCount >= 9 {
		waitTime := time.Minute - now.Sub(s.apiCallResetTime)
		if waitTime > 0 {
			fmt.Printf("Rate limit reached, waiting %v...\n", waitTime.Round(time.Second))
			time.Sleep(waitTime)
			s.apiCallCount = 0
			s.apiCallResetTime = time.Now()
		}
	}

	// Add delay between requests (7 seconds to be safe)
	if !s.lastAPICallTime.IsZero() {
		timeSinceLastCall := now.Sub(s.lastAPICallTime)
		minDelay := 7 * time.Second
		if timeSinceLastCall < minDelay {
			waitTime := minDelay - timeSinceLastCall
			fmt.Printf("Rate limiting: waiting %v...\n", waitTime.Round(time.Second))
			time.Sleep(waitTime)
		}
	}

	// Decode base64 API URL
	spotifyBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly9vcGVuLnNwb3RpZnkuY29tL3RyYWNrLw==")
	spotifyURL := fmt.Sprintf("%s%s", string(spotifyBase), spotifyTrackID)

	apiBase, _ := base64.StdEncoding.DecodeString("aHR0cHM6Ly9hcGkuc29uZy5saW5rL3YxLWFscGhhLjEvbGlua3M/dXJsPQ==")
	apiURL := fmt.Sprintf("%s%s", string(apiBase), url.QueryEscape(spotifyURL))

	req, err := http.NewRequest("GET", apiURL, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	fmt.Println("Getting streaming URLs from song.link...")

	// Retry logic for rate limit errors
	maxRetries := 3
	var resp *http.Response
	for i := 0; i < maxRetries; i++ {
		resp, err = s.client.Do(req)
		if err != nil {
			return nil, fmt.Errorf("failed to get URLs: %w", err)
		}

		// Update rate limit tracking
		s.lastAPICallTime = time.Now()
		s.apiCallCount++

		if resp.StatusCode == 429 {
			resp.Body.Close()
			if i < maxRetries-1 {
				waitTime := 15 * time.Second
				fmt.Printf("Rate limited by API, waiting %v before retry...\n", waitTime)
				time.Sleep(waitTime)
				continue
			}
			return nil, fmt.Errorf("API rate limit exceeded after %d retries", maxRetries)
		}

		if resp.StatusCode != 200 {
			resp.Body.Close()
			return nil, fmt.Errorf("API returned status %d", resp.StatusCode)
		}

		break
	}
	defer resp.Body.Close()

	var songLinkResp struct {
		LinksByPlatform map[string]struct {
			URL string `json:"url"`
		} `json:"linksByPlatform"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&songLinkResp); err != nil {
		return nil, fmt.Errorf("failed to decode response: %w", err)
	}

	urls := &SongLinkURLs{}

	// Extract Tidal URL
	if tidalLink, ok := songLinkResp.LinksByPlatform["tidal"]; ok && tidalLink.URL != "" {
		urls.TidalURL = tidalLink.URL
		fmt.Printf("✓ Tidal URL found\n")
	}

	// Extract Deezer URL
	if deezerLink, ok := songLinkResp.LinksByPlatform["deezer"]; ok && deezerLink.URL != "" {
		urls.DeezerURL = deezerLink.URL
		fmt.Printf("✓ Deezer URL found\n")
	}

	// Extract Amazon URL
	if amazonLink, ok := songLinkResp.LinksByPlatform["amazonMusic"]; ok && amazonLink.URL != "" {
		amazonURL := amazonLink.URL
		// Convert album URL to track URL if needed
		if len(amazonURL) > 0 {
			urls.AmazonURL = amazonURL
			fmt.Printf("✓ Amazon URL found\n")
		}
	}

	// Check if at least one URL was found
	if urls.TidalURL == "" && urls.DeezerURL == "" && urls.AmazonURL == "" {
		return nil, fmt.Errorf("no streaming URLs found")
	}

	return urls, nil
}