/**
 * URL 重定向解析：在浏览器导航前尽可能解析 HTTP 级重定向链。
 */
'use strict';

const http = require('http');
const https = require('https');

const REDIRECT_STATUS = new Set([301, 302, 303, 307, 308]);

/**
 * 发起单次 HEAD/GET，不自动跟随重定向。
 */
function fetchOnce(method, url, timeoutMs) {
    return new Promise((resolve, reject) => {
        const parsed = new URL(url);
        const lib = parsed.protocol === 'https:' ? https : http;
        const req = lib.request(
            url,
            { method, timeout: timeoutMs, headers: { 'User-Agent': 'Mozilla/5.0 (compatible; puppeteer-api/1.0)' } },
            (res) => {
                res.resume();
                resolve({ statusCode: res.statusCode || 0, headers: res.headers || {} });
            }
        );
        req.on('timeout', () => {
            req.destroy();
            reject(new Error('REDIRECT_TIMEOUT'));
        });
        req.on('error', reject);
        req.end();
    });
}

/**
 * 跟随 HTTP 重定向，返回最终 URL（无法解析时返回原始 URL）。
 */
async function resolveHttpRedirects(startUrl, { maxRedirects = 10, timeoutMs = 12000 } = {}) {
    let current = startUrl;
    for (let i = 0; i < maxRedirects; i++) {
        let response;
        try {
            response = await fetchOnce('HEAD', current, timeoutMs);
        } catch (_) {
            response = await fetchOnce('GET', current, timeoutMs);
        }
        if (!REDIRECT_STATUS.has(response.statusCode)) {
            return current;
        }
        const location = response.headers.location;
        if (!location) {
            return current;
        }
        current = new URL(location, current).href;
    }
    return current;
}

/**
 * 从分享页 URL 提取 token 参数（星河等云控）。
 */
function extractShareTokenFromUrl(pageUrl) {
    try {
        return new URL(pageUrl).searchParams.get('token') || '';
    } catch (_) {
        return '';
    }
}

module.exports = {
    resolveHttpRedirects,
    extractShareTokenFromUrl,
};