/**
 * iTunes Search API integration for fetching release years
 * API Documentation: https://performance-partners.apple.com/search-api
 */

interface ItunesResult {
    wrapperType: string;
    kind: string;
    artistName: string;
    collectionName: string;
    trackName: string;
    releaseDate: string;
    primaryGenreName: string;
}

interface ItunesResponse {
    resultCount: number;
    results: ItunesResult[];
}

// Rate limiting state
let lastRequestTime = 0;
let blockedUntil = 0;
const MIN_INTERVAL = 2000; // 2 seconds = 30 requests per minute
const BLOCK_DURATION = 60000; // 60 seconds pause after 403

// Mutex for serializing requests
let requestQueue = Promise.resolve<any>(null);

/**
 * Get the earliest release year for a song from iTunes
 * @param artist Artist name
 * @param title Song title
 * @returns Release year or null if not found
 */
export async function getReleaseYearFromItunes(artist: string, title: string): Promise<number | null> {
    // Queue the request to ensure sequential execution and rate limiting
    const result = requestQueue.then(() => executeRequest(artist, title));

    // Update queue to wait for this request
    requestQueue = result.catch(() => null);

    return result;
}

async function executeRequest(artist: string, title: string): Promise<number | null> {
    try {
        // Check if blocked
        const now = Date.now();
        if (now < blockedUntil) {
            const waitTime = blockedUntil - now;
            console.log(`iTunes API blocked (403/429). Waiting ${Math.ceil(waitTime / 1000)}s before next request...`);
            await new Promise(resolve => setTimeout(resolve, waitTime));
        }

        // Enforce rate limit (min interval)
        const timeSinceLast = Date.now() - lastRequestTime;
        if (timeSinceLast < MIN_INTERVAL) {
            const delay = MIN_INTERVAL - timeSinceLast;
            await new Promise(resolve => setTimeout(resolve, delay));
        }

        // Construct search URL
        const term = encodeURIComponent(`${artist} ${title}`);
        const url = `https://itunes.apple.com/search?term=${term}&entity=song&limit=10`;

        const response = await fetch(url, {
            headers: {
                'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36',
                'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8',
                'Accept-Language': 'en-US,en;q=0.9'
            }
        });

        lastRequestTime = Date.now();

        if (response.status === 403 || response.status === 429) {
            console.warn(`iTunes API rate limit hit (${response.status}). Pausing for 60s.`);
            blockedUntil = Date.now() + BLOCK_DURATION;
            return null;
        }

        if (!response.ok) {
            console.error(`iTunes API error: ${response.status} ${response.statusText}`);
            return null;
        }

        const data: ItunesResponse = await response.json();

        if (data.resultCount === 0) {
            return null;
        }

        // Filter for exact(ish) matches to avoid wrong songs
        // and find the earliest release date
        let earliestYear: number | null = null;
        const normalizedTitle = title.toLowerCase().replace(/[^\w\s]/g, '');
        const normalizedArtist = artist.toLowerCase().replace(/[^\w\s]/g, '');

        for (const result of data.results) {
            // Basic validation that it's the right song
            const resTitle = result.trackName.toLowerCase().replace(/[^\w\s]/g, '');
            const resArtist = result.artistName.toLowerCase().replace(/[^\w\s]/g, '');

            // Check if title and artist are contained in the result (fuzzy match)
            if (resTitle.includes(normalizedTitle) && resArtist.includes(normalizedArtist)) {
                if (result.releaseDate) {
                    const year = new Date(result.releaseDate).getFullYear();
                    if (!isNaN(year)) {
                        if (earliestYear === null || year < earliestYear) {
                            earliestYear = year;
                        }
                    }
                }
            }
        }

        return earliestYear;

    } catch (error) {
        console.error(`Error fetching release year from iTunes for "${title}" by "${artist}":`, error);
        return null;
    }
}