/**
 * M3U Playlist Dead Link Checker
 * Checks URLs in an M3U playlist and logs dead links for Forgejo Actions.
 */

const fs = require('fs');
const https = require('https');
const http = require('http');
const { URL } = require('url');

// Configuration
const M3U_FILE = 'mystique.m3u';
const REQUEST_TIMEOUT = 10000; // 10 seconds
const MAX_RETRIES = 2;
const DELAY_BETWEEN_REQUESTS = 1000; // 1 second
const USER_AGENT = 'M3U-Checker/1.0';

class M3UChecker {
    constructor() {
        this.repoOwner = process.env.REPO_OWNER;
        this.repoName = process.env.REPO_NAME;
    }

    /**
     * Parse M3U file and extract URLs with metadata
     */
    parseM3U(filepath) {
        if (!fs.existsSync(filepath)) {
            throw new Error(`${filepath} not found!`);
        }

        const content = fs.readFileSync(filepath, 'utf8');
        const lines = content.split('\n').map(line => line.trim()).filter(line => line);
        
        const entries = [];
        let currentExtinf = null;

        for (const line of lines) {
            if (line.startsWith('#EXTINF:')) {
                // Parse EXTINF line: #EXTINF:duration,title
                const match = line.match(/^#EXTINF:([^,]*),(.+)$/);
                if (match) {
                    currentExtinf = {
                        duration: match[1].trim(),
                        title: match[2].trim()
                    };
                } else {
                    currentExtinf = { duration: '', title: 'Unknown' };
                }
            } else if (!line.startsWith('#') && this.isValidUrl(line)) {
                // This should be a URL
                const entry = {
                    url: line,
                    title: currentExtinf ? currentExtinf.title : 'Unknown',
                    duration: currentExtinf ? currentExtinf.duration : ''
                };
                entries.push(entry);
                currentExtinf = null;
            }
        }

        return entries;
    }

    /**
     * Basic URL validation
     */
    isValidUrl(urlString) {
        try {
            new URL(urlString);
            return true;
        } catch {
            return false;
        }
    }

    /**
     * Check if URL is accessible
     * Returns Promise<{isAlive: boolean, error: string, statusCode: number}>
     */
    async checkUrl(url) {
        for (let attempt = 0; attempt < MAX_RETRIES; attempt++) {
            try {
                const result = await this.makeRequest(url);
                if (result.statusCode < 400) {
                    return { isAlive: true, error: '', statusCode: result.statusCode };
                } else {
                    return { isAlive: false, error: `HTTP ${result.statusCode}`, statusCode: result.statusCode };
                }
            } catch (error) {
                if (attempt === MAX_RETRIES - 1) {
                    return { isAlive: false, error: error.message, statusCode: 0 };
                }
                // Wait before retry
                await this.sleep(DELAY_BETWEEN_REQUESTS * (attempt + 1));
            }
        }
    }

    /**
     * Make HTTP request with timeout
     */
    makeRequest(url) {
        return new Promise((resolve, reject) => {
            const urlObj = new URL(url);
            const isHttps = urlObj.protocol === 'https:';
            const lib = isHttps ? https : http;

            const options = {
                hostname: urlObj.hostname,
                port: urlObj.port || (isHttps ? 443 : 80),
                path: urlObj.pathname + urlObj.search,
                method: 'HEAD',
                timeout: REQUEST_TIMEOUT,
                headers: {
                    'User-Agent': USER_AGENT
                }
            };

            const req = lib.request(options, (res) => {
                // If HEAD is not allowed, try GET with range
                if (res.statusCode === 405) {
                    this.makeGetRequest(url).then(resolve).catch(reject);
                    return;
                }
                resolve({ statusCode: res.statusCode });
            });

            req.on('timeout', () => {
                req.destroy();
                reject(new Error(`Timeout after ${REQUEST_TIMEOUT}ms`));
            });

            req.on('error', (error) => {
                if (error.code === 'ECONNREFUSED') {
                    reject(new Error('Connection refused'));
                } else if (error.code === 'ENOTFOUND') {
                    reject(new Error('Host not found'));
                } else if (error.code === 'ETIMEDOUT') {
                    reject(new Error('Connection timeout'));
                } else {
                    reject(new Error(`Connection error: ${error.message}`));
                }
            });

            req.end();
        });
    }

    /**
     * Make GET request with range header (fallback for servers that don't support HEAD)
     */
    makeGetRequest(url) {
        return new Promise((resolve, reject) => {
            const urlObj = new URL(url);
            const isHttps = urlObj.protocol === 'https:';
            const lib = isHttps ? https : http;

            const options = {
                hostname: urlObj.hostname,
                port: urlObj.port || (isHttps ? 443 : 80),
                path: urlObj.pathname + urlObj.search,
                method: 'GET',
                timeout: REQUEST_TIMEOUT,
                headers: {
                    'User-Agent': USER_AGENT,
                    'Range': 'bytes=0-1024'
                }
            };

            const req = lib.request(options, (res) => {
                // Consume response to prevent memory leak
                res.on('data', () => {});
                res.on('end', () => {
                    resolve({ statusCode: res.statusCode });
                });
            });

            req.on('timeout', () => {
                req.destroy();
                reject(new Error(`Timeout after ${REQUEST_TIMEOUT}ms`));
            });

            req.on('error', (error) => {
                reject(error);
            });

            req.end();
        });
    }

    /**
     * Sleep utility
     */
    sleep(ms) {
        return new Promise(resolve => setTimeout(resolve, ms));
    }

    /**
     * Log dead link information
     */
    logDeadLink(entry, error, statusCode) {
        console.log(`\n🔴 DEAD LINK FOUND:`);
        console.log(`   Title: ${entry.title}`);
        console.log(`   URL: ${entry.url}`);
        console.log(`   Error: ${error}`);
        console.log(`   Status Code: ${statusCode || 'N/A'}`);
        console.log(`   Duration: ${entry.duration || 'Unknown'}`);
        console.log(`   Repository: ${this.repoOwner}/${this.repoName}`);
    }

    /**
     * Main function to check M3U playlist
     */
    async runCheck() {
        console.log(`🎵 M3U Playlist Dead Link Checker`);
        console.log(`=====================================`);
        
        try {
            console.log(`📂 Parsing ${M3U_FILE}...`);
            const entries = this.parseM3U(M3U_FILE);
            console.log(`🔍 Found ${entries.length} URLs to check\n`);

            if (entries.length === 0) {
                console.log('❌ No URLs found in playlist');
                return;
            }

            const deadLinks = [];
            let aliveCount = 0;

            for (let i = 0; i < entries.length; i++) {
                const entry = entries[i];
                const progress = `[${(i + 1).toString().padStart(3)}/${entries.length}]`;
                
                console.log(`${progress} Checking: ${entry.title}`);
                
                const result = await this.checkUrl(entry.url);

                if (result.isAlive) {
                    aliveCount++;
                    console.log(`   ✅ Alive (${result.statusCode})`);
                } else {
                    deadLinks.push({ entry, error: result.error, statusCode: result.statusCode });
                    console.log(`   ❌ Dead (${result.error})`);
                    
                    // Log dead link details immediately
                    this.logDeadLink(entry, result.error, result.statusCode);
                }
                
                // Add delay between requests
                if (i < entries.length - 1) {
                    await this.sleep(DELAY_BETWEEN_REQUESTS);
                }
            }

            // Final summary
            console.log(`\n📊 CHECK COMPLETED`);
            console.log(`===================`);
            console.log(`✅ Alive: ${aliveCount}`);
            console.log(`❌ Dead: ${deadLinks.length}`);
            console.log(`📈 Success Rate: ${((aliveCount / entries.length) * 100).toFixed(1)}%`);

            if (deadLinks.length > 0) {
                console.log(`\n🚨 DEAD LINKS SUMMARY:`);
                console.log(`=======================`);
                deadLinks.forEach(({ entry, error }, index) => {
                    console.log(`${(index + 1).toString().padStart(2)}. ${entry.title}`);
                    console.log(`    URL: ${entry.url}`);
                    console.log(`    Error: ${error}`);
                    console.log('');
                });
            } else {
                console.log(`\n🎉 All links are alive! No issues found.`);
            }

        } catch (error) {
            console.error(`❌ Error during check: ${error.message}`);
            process.exit(1);
        }
    }
}

// Run the checker
if (require.main === module) {
    const checker = new M3UChecker();
    checker.runCheck().catch(error => {
        console.error(`💥 Fatal error: ${error.message}`);
        process.exit(1);
    });
}