// ==UserScript==
// @name         Auto Mobile→Desktop Redirect (Enhanced)
// @namespace    https://github.com/downwarjers/WebTweaks
// @version      1.1.3
// @description  當訪問手機版網頁（如 `m.`, `mobile.` 開頭或包含 `/mobile/` 路徑）時，自動嘗試跳轉回桌面版網址。內建防無限迴圈機制（檢查 Referrer 與 SessionStorage 計數），避免在只有手機版的網站上卡死。
// @author       downwarjers
// @license      MIT
// @match        *://*/*
// @run-at       document-start
// @grant        none
// @downloadURL https://raw.githubusercontent.com/downwarjers/WebTweaks/main/UserScripts/auto-redirect-to-desktop-web/auto-redirect-to-desktop-web.user.js
// @updateURL   https://raw.githubusercontent.com/downwarjers/WebTweaks/main/UserScripts/auto-redirect-to-desktop-web/auto-redirect-to-desktop-web.user.js
// ==/UserScript==

(function() {
    'use strict';

    const MAX_REDIRECT_COUNT = 3; // 降低上限，減少閃爍
    const SESSION_STORAGE_KEY = 'prog_auto_redirect_count';
    const ONE_MINUTE = 60 * 1000;

    // --- 檢查並更新跳轉計數 ---
    const now = Date.now();
    let record = null;
    
    try {
        record = JSON.parse(sessionStorage.getItem(SESSION_STORAGE_KEY));
    } catch (e) {
        record = null;
    }

    if (!record || (now - record.ts) > ONE_MINUTE) {
        record = { count: 0, ts: now };
    }

    // 若短時間內嘗試次數過多，直接中止，保護瀏覽器
    if (record.count >= MAX_REDIRECT_COUNT) {
        console.warn('PROG: 跳轉次數過多，判定為無效跳轉或死路，停止執行。');
        return;
    }

    // --- 判斷並執行跳轉 ---
    const host = window.location.hostname;
    const path = window.location.pathname;
    const search = window.location.search;
    const hash = window.location.hash;
    const protocol = window.location.protocol;

    let newUrl = null;

    // 1. 處理子網域模式 (m.domain.com -> www.domain.com)
    // 這裡優化邏輯：有些網站不是轉 www，而是直接去掉 m.
    if (/^m\./i.test(host)) {
        newUrl = `${protocol}//${host.replace(/^m\./i, 'www.')}${path}${search}${hash}`;
    } else if (/^mobile\./i.test(host)) {
        newUrl = `${protocol}//${host.replace(/^mobile\./i, '')}${path}${search}${hash}`;
    } else if (/\.m\./i.test(host)) {
        newUrl = `${protocol}//${host.replace(/\.m\./i, '.')}${path}${search}${hash}`;
    }
    
    // 2. 處理路徑模式 (domain.com/mobile/ -> domain.com/)
    if (!newUrl && path.toLowerCase().includes('/mobile/')) {
        const newPath = path.toLowerCase().replace('/mobile/', '/');
        newUrl = `${protocol}//${host}${newPath}${search}${hash}`;
    }
    
    // 3. 檢查特殊網址參數 (?view=mobile)
    if (!newUrl && search.toLowerCase().includes('view=mobile')) {
        const newSearch = search.replace(/(\?|&)view=mobile/i, '').replace(/^\?/, '');
        newUrl = `${protocol}//${host}${path}${newSearch ? '?' + newSearch : ''}${hash}`;
    }

    if (newUrl && newUrl !== window.location.href) {
        
        // [核心防護] 檢查 Referrer (來源)
        // 如果來源網址包含了我們要跳轉的目標網址 (例如從 www 被踢回 m)，則停止跳轉
        // 這解決了 "只有手機版網站" 或 "強制手機版" 造成的無窮迴圈
        if (document.referrer && (newUrl.includes(document.referrer) || document.referrer.includes(newUrl))) {
            console.warn(`PROG: 偵測到被伺服器踢回 (來源: ${document.referrer})，停止跳轉。`);
            // 既然被踢回來，代表這次 session 也不用再試了，直接把計數器填滿
            record.count = MAX_REDIRECT_COUNT + 1;
            sessionStorage.setItem(SESSION_STORAGE_KEY, JSON.stringify(record));
            return;
        }

        // 累計計數
        record.count++;
        sessionStorage.setItem(SESSION_STORAGE_KEY, JSON.stringify(record));

        console.log(`PROG: 偵測到手機版，跳轉至 ${newUrl} (第 ${record.count} 次)`);
        window.location.replace(newUrl);
    }

})();