// ==UserScript==
// @name         LinuxDO URL 更改优化
// @namespace    Neuroplexus_Do_State-Manager
// @version      1.1
// @description  优化 linux.do 论坛的历史记录管理, 当 URL 更改时, 不进行不必要的历史记录堆栈增加.
// @author       Neuroplexus
// @match        https://linux.do/t/topic/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    
    // 保存原始的历史方法
    const originalPushState = window.history.pushState;
    const originalReplaceState = window.history.replaceState;
    
    // 用于存储状态的数组
    let stateStack = [];
    let currentStateIndex = -1;
    
    // 获取当前 topic ID
    function getTopicId(url) {
        const match = url.match(/\/t\/topic\/(\d+)/);
        return match ? match[1] : null;
    }
    
    // 添加状态到栈中
    function addToStateStack(state, title, url) {
        // 如果不是在栈顶,删除当前位置之后的所有状态
        if (currentStateIndex < stateStack.length - 1) {
            stateStack = stateStack.slice(0, currentStateIndex + 1);
        }
        
        stateStack.push({
            state: state,
            title: title,
            url: url
        });
        currentStateIndex++;
    }
    
    // 重写 pushState 方法
    window.history.pushState = function(state, title, url) {
        const currentTopicId = getTopicId(window.location.href);
        const newTopicId = getTopicId(url);
        
        // 如果在同一个 topic 内导航,使用增强的 replaceState
        if (currentTopicId && newTopicId && currentTopicId === newTopicId) {
            addToStateStack(state, title, url);
            return originalReplaceState.call(this, state, title, url);
        }
        
        // 其他情况使用原始的 pushState
        addToStateStack(state, title, url);
        return originalPushState.call(this, state, title, url);
    };
    
    // 重写 replaceState 方法
    window.history.replaceState = function(state, title, url) {
        if (currentStateIndex >= 0) {
            stateStack[currentStateIndex] = {
                state: state,
                title: title,
                url: url
            };
        }
        return originalReplaceState.call(this, state, title, url);
    };
    
    // 监听 popstate 事件(前进/后退按钮触发)
    window.addEventListener('popstate', function(event) {
        // 查找目标状态在栈中的位置
        const targetUrl = window.location.href;
        const targetIndex = stateStack.findIndex(item => item.url === targetUrl);
        
        if (targetIndex !== -1) {
            currentStateIndex = targetIndex;
            // 不需要手动调用 replaceState,因为浏览器已经更新了 URL
        }
    });
    
    // 初始化当前页面状态
    addToStateStack(history.state, document.title, window.location.href);
})();