package main

import (
	"encoding/json"
	"fmt"
	"net/url"
	"strings"

	"github.com/navidrome/navidrome/plugins/pdk/go/host"
	"github.com/navidrome/navidrome/plugins/pdk/go/pdk"
	"github.com/navidrome/navidrome/plugins/pdk/go/scrobbler"
)

// hashKey returns a hex-encoded FNV-1a hash of s, for use as a cache key suffix.
func hashKey(s string) string {
	const offset64 uint64 = 14695981039346656037
	const prime64 uint64 = 1099511628211
	h := offset64
	for i := 0; i < len(s); i++ {
		h ^= uint64(s[i])
		h *= prime64
	}
	return fmt.Sprintf("%016x", h)
}

const (
	spotifyCacheTTLHit  int64 = 30 * 24 * 60 * 60 // 30 days for resolved track IDs
	spotifyCacheTTLMiss int64 = 4 * 60 * 60       // 4 hours for misses (retry later)
)

// listenBrainzResult captures the relevant field from ListenBrainz Labs JSON responses.
// The API returns spotify_track_ids as an array of strings.
type listenBrainzResult struct {
	SpotifyTrackIDs []string `json:"spotify_track_ids"`
}

// spotifySearchURL builds a Spotify search URL from one or more terms.
// Empty terms are ignored. Returns "" if all terms are empty.
func spotifySearchURL(terms ...string) string {
	query := strings.TrimSpace(strings.Join(terms, " "))
	if query == "" {
		return ""
	}
	return "https://open.spotify.com/search/" + url.PathEscape(query)
}

// spotifyCacheKey returns a deterministic cache key for a track's Spotify URL.
func spotifyCacheKey(artist, title, album string) string {
	return "spotify.url." + hashKey(strings.ToLower(artist)+"\x00"+strings.ToLower(title)+"\x00"+strings.ToLower(album))
}

// trySpotifyFromMBID calls the ListenBrainz spotify-id-from-mbid endpoint.
func trySpotifyFromMBID(mbid string) string {
	body := fmt.Sprintf(`[{"recording_mbid":%q}]`, mbid)
	resp, err := host.HTTPSend(host.HTTPRequest{
		Method:  "POST",
		URL:     "https://labs.api.listenbrainz.org/spotify-id-from-mbid/json",
		Headers: map[string]string{"Content-Type": "application/json"},
		Body:    []byte(body),
	})
	if err != nil {
		pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz MBID lookup request failed: %v", err))
		return ""
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		pdk.Log(pdk.LogDebug, fmt.Sprintf("ListenBrainz MBID lookup failed: HTTP %d, body=%s", resp.StatusCode, string(resp.Body)))
		return ""
	}
	id := parseSpotifyID(resp.Body)
	if id == "" {
		pdk.Log(pdk.LogDebug, fmt.Sprintf("ListenBrainz MBID lookup returned no spotify_track_id for mbid=%s, body=%s", mbid, string(resp.Body)))
	}
	return id
}

// trySpotifyFromMetadata calls the ListenBrainz spotify-id-from-metadata endpoint.
func trySpotifyFromMetadata(artist, title, album string) string {
	payload := fmt.Sprintf(`[{"artist_name":%q,"track_name":%q,"release_name":%q}]`, artist, title, album)

	pdk.Log(pdk.LogDebug, fmt.Sprintf("ListenBrainz metadata request: %s", payload))

	resp, err := host.HTTPSend(host.HTTPRequest{
		Method:  "POST",
		URL:     "https://labs.api.listenbrainz.org/spotify-id-from-metadata/json",
		Headers: map[string]string{"Content-Type": "application/json"},
		Body:    []byte(payload),
	})
	if err != nil {
		pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz metadata lookup request failed: %v", err))
		return ""
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		pdk.Log(pdk.LogDebug, fmt.Sprintf("ListenBrainz metadata lookup failed: HTTP %d, body=%s", resp.StatusCode, string(resp.Body)))
		return ""
	}
	pdk.Log(pdk.LogDebug, fmt.Sprintf("ListenBrainz metadata response: HTTP %d, body=%s", resp.StatusCode, string(resp.Body)))
	id := parseSpotifyID(resp.Body)
	if id == "" {
		pdk.Log(pdk.LogDebug, fmt.Sprintf("ListenBrainz metadata returned no spotify_track_id for %q - %q", artist, title))
	}
	return id
}

// parseSpotifyID extracts the first spotify track ID from a ListenBrainz Labs JSON response.
// The response is an array of objects with spotify_track_ids arrays; we take the first non-empty ID.
func parseSpotifyID(body []byte) string {
	var results []listenBrainzResult
	if err := json.Unmarshal(body, &results); err != nil {
		return ""
	}
	for _, r := range results {
		for _, id := range r.SpotifyTrackIDs {
			if isValidSpotifyID(id) {
				return id
			}
		}
	}
	return ""
}

// isValidSpotifyID checks that a Spotify track ID is non-empty and contains only base-62 characters.
func isValidSpotifyID(id string) bool {
	if len(id) == 0 {
		return false
	}
	for i := 0; i < len(id); i++ {
		c := id[i]
		if !((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')) {
			return false
		}
	}
	return true
}

// resolveSpotifyURL resolves a direct Spotify track URL via ListenBrainz Labs,
// falling back to a search URL. Results are cached.
func resolveSpotifyURL(track scrobbler.TrackInfo) string {
	var primary string
	if len(track.Artists) > 0 {
		primary = track.Artists[0].Name
	}

	cacheKey := spotifyCacheKey(primary, track.Title, track.Album)

	if cached, exists, err := host.CacheGetString(cacheKey); err == nil && exists {
		pdk.Log(pdk.LogDebug, fmt.Sprintf("Spotify URL cache hit for %q - %q → %s", primary, track.Title, cached))
		return cached
	}

	pdk.Log(pdk.LogDebug, fmt.Sprintf("Resolving Spotify URL for: artist=%q title=%q album=%q mbid=%q", primary, track.Title, track.Album, track.MBZRecordingID))

	// 1. Try MBID lookup (most accurate)
	if track.MBZRecordingID != "" {
		if trackID := trySpotifyFromMBID(track.MBZRecordingID); trackID != "" {
			directURL := "https://open.spotify.com/track/" + trackID
			_ = host.CacheSetString(cacheKey, directURL, spotifyCacheTTLHit)
			pdk.Log(pdk.LogInfo, fmt.Sprintf("Resolved Spotify via MBID for %q: %s", track.Title, directURL))
			return directURL
		}
		pdk.Log(pdk.LogDebug, "MBID lookup did not return a Spotify ID, trying metadata…")
	} else {
		pdk.Log(pdk.LogDebug, "No MBZRecordingID available, skipping MBID lookup")
	}

	// 2. Try metadata lookup
	if primary != "" && track.Title != "" {
		if trackID := trySpotifyFromMetadata(primary, track.Title, track.Album); trackID != "" {
			directURL := "https://open.spotify.com/track/" + trackID
			_ = host.CacheSetString(cacheKey, directURL, spotifyCacheTTLHit)
			pdk.Log(pdk.LogInfo, fmt.Sprintf("Resolved Spotify via metadata for %q - %q: %s", primary, track.Title, directURL))
			return directURL
		}
	}

	// 3. Fallback to search URL
	searchURL := spotifySearchURL(track.Artist, track.Title)
	_ = host.CacheSetString(cacheKey, searchURL, spotifyCacheTTLMiss)
	pdk.Log(pdk.LogInfo, fmt.Sprintf("Spotify resolution missed, falling back to search URL for %q - %q: %s", primary, track.Title, searchURL))
	return searchURL
}