const http = require('http');
const https = require('https');
const url = require('url');
const querystring = require('querystring');
const fs = require('fs');
const path = require('path');

const requestTimeout = 10000; // 10 seconds
const cacheDir = path.join(__dirname, '.cache');
const args = process.argv.slice(2);

let port = 9001;
let apiEndpoint = 'https://oss.x-php.com/alist/link';

// 解析命令行参数
args.forEach(arg => {
    const [key, value] = arg.split('=');
    if (key === 'port') {
        port = parseInt(value, 10);
    } else if (key === 'api') {
        apiEndpoint = value;
    }
});

// 确保缓存目录存在
if (!fs.existsSync(cacheDir)) {
    fs.mkdirSync(cacheDir);
}

const server = http.createServer(async (req, res) => {
    if (req.url === '/favicon.ico') {
        res.writeHead(204);
        res.end();
        return;
    }

    const parsedUrl = url.parse(req.url, true);
    const reqPath = parsedUrl.pathname;
    const sign = parsedUrl.query.sign || '';

    // 只要reqPath的文件名，不要路径
    const reqName = parsedUrl.pathname.split('/').pop();
    const cacheMetaFile = path.join(cacheDir, `${reqName.replace(/\//g, '_')}.meta`);
    const cacheContentFile = path.join(cacheDir, `${reqName.replace(/\//g, '_')}.content`);
    const tempCacheContentFile = path.join(cacheDir, `${reqName.replace(/\//g, '_')}.temp`);

    if (!sign || reqPath === '/') {
        res.writeHead(400, { 'Content-Type': 'text/plain' });
        res.end('Bad Request: Missing sign or path');
        return;
    }

    if (isCacheValid(cacheMetaFile, cacheContentFile)) {
        serveFromCache(cacheMetaFile, cacheContentFile, res);
    } else {
        try {
            const apiData = await fetchApiData(reqPath, sign);
            if (apiData.code === 200 && apiData.data && apiData.data.url) {
                const { url: realUrl, cloudtype, expiration } = apiData.data;
                const data = { realUrl, cloudtype, expiration: expiration * 1000 };

                if (expiration > 0) {
                    fs.writeFileSync(cacheMetaFile, JSON.stringify(data));
                }

                // 如果 cacheContentFile 存在 直接调用它
                if (fs.existsSync(cacheContentFile)) {
                    serveFromCache(cacheMetaFile, cacheContentFile, res);
                    return;
                }
                fetchAndServe(data, tempCacheContentFile, cacheContentFile, res);
            } else {
                res.writeHead(502, { 'Content-Type': 'text/plain' });
                res.end(apiData.message || 'Bad Gateway');
            }
        } catch (error) {
            res.writeHead(502, { 'Content-Type': 'text/plain' });
            res.end('Bad Gateway: Failed to decode JSON' + error);
        }
    }
});

const isCacheValid = (cacheMetaFile, cacheContentFile) => {
    if (!fs.existsSync(cacheMetaFile) || !fs.existsSync(cacheContentFile)) return false;

    const cacheData = JSON.parse(fs.readFileSync(cacheMetaFile, 'utf8'));
    return cacheData.expiration > Date.now();
};

const fetchApiData = (reqPath, sign) => {
    return new Promise((resolve, reject) => {
        const postData = querystring.stringify({ path: reqPath, sign });

        const apiReq = https.request(apiEndpoint, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded',
                'Accept': 'application/json',
                'Content-Length': Buffer.byteLength(postData),
                'sign': sign
            },
            timeout: requestTimeout
        }, (apiRes) => {
            let data = '';
            apiRes.on('data', chunk => data += chunk);
            apiRes.on('end', () => {
                try {
                    resolve(JSON.parse(data));
                } catch (error) {
                    reject(error);
                }
            });
        });

        apiReq.on('error', reject);
        apiReq.write(postData);
        apiReq.end();
    });
};

const fetchAndServe = (data, tempCacheContentFile, cacheContentFile, res) => {
    https.get(data.realUrl, { timeout: requestTimeout * 10 }, (realRes) => {
        // 创建临时缓存文件流
        const cacheStream = fs.createWriteStream(tempCacheContentFile, { flags: 'w' });

        res.writeHead(realRes.statusCode, {
            ...realRes.headers,
            'Cloud-Type': data.cloudtype,
            'Cloud-Expiration': data.expiration,
        });

        realRes.pipe(cacheStream);
        realRes.pipe(res);

        realRes.on('end', () => {
            // 下载完成后，将临时文件重命名为最终缓存文件
            fs.renameSync(tempCacheContentFile, cacheContentFile);
            cacheStream.end();
        });

        realRes.on('error', (e) => {
            if (!res.headersSent) {
                res.writeHead(502, { 'Content-Type': 'text/plain' });
                res.end(`Bad Gateway: ${data.realUrl}`);
            }
            fs.unlinkSync(tempCacheContentFile); // 删除临时文件
        });
    }).on('error', (e) => {
        if (!res.headersSent) {
            res.writeHead(502, { 'Content-Type': 'text/plain' });
            res.end(`Bad Gateway: ${data.realUrl}`);
        }
        fs.unlinkSync(tempCacheContentFile); // 删除临时文件
    });
};

const serveFromCache = (cacheMetaFile, cacheContentFile, res) => {
    const cacheData = JSON.parse(fs.readFileSync(cacheMetaFile, 'utf8'));
    const readStream = fs.createReadStream(cacheContentFile);

    readStream.on('open', () => {
        res.writeHead(200, {
            'Content-Type': 'application/octet-stream',
            'Cloud-Type': cacheData.cloudtype,
            'Cloud-Expiration': cacheData.expiration,
        });
        readStream.pipe(res);
    });

    readStream.on('error', (err) => {
        if (!res.headersSent) {
            res.writeHead(500, { 'Content-Type': 'text/plain' });
            res.end('Internal Server Error: Unable to read cache content file');
        }
    });
};

server.listen(port, () => {
    console.log(`Proxy server is running on http://localhost:${port}`);
});

// Graceful shutdown
process.on('SIGINT', () => {
    console.log('Received SIGINT. Shutting down gracefully...');
    server.close(() => {
        console.log('Server closed.');
        process.exit(0);
    });

    // Force shutdown after 10 seconds if not closed
    setTimeout(() => {
        console.error('Forcing shutdown...');
        process.exit(1);
    }, 10000);
});