class BgSwitcher {
    constructor(images, options = {}) {
        this.images = images;
        // 从localStorage中读取保存的索引
        const savedIndex = localStorage.getItem('bgSwitcherIndex');
        if (savedIndex !== null && !isNaN(savedIndex)) {
            this.index = parseInt(savedIndex);
        } else {
            this.index = 0;
        }
        this.container = options.container || document.body;
        this.interval = options.interval || 3000;
        this.effect = options.effect || BgSwitcher.fadeEffect;
        this.timer = null;
        this.apiTimer = null;
        this.apiUrl = null;
        this.apiInterval = 30000;
        this.startTime = 0;
        // 从localStorage中读取保存的剩余时间
        const savedRemainingTime = localStorage.getItem('bgSwitcherRemainingTime');
        this.remainingTime = savedRemainingTime !== null && !isNaN(savedRemainingTime) && savedRemainingTime >= 0 ? parseInt(savedRemainingTime) : this.interval;
        this.bgLayer = document.createElement('div');
        this.isInitialLoad = true;

        // 从localStorage中读取API模式状态
        const isApiMode = localStorage.getItem('bgSwitcherIsApiMode') === 'true';
        if (isApiMode) {
            this.apiUrl = localStorage.getItem('bgSwitcherApiUrl') || null;
            const savedApiInterval = localStorage.getItem('bgSwitcherApiInterval');
            this.apiInterval = savedApiInterval !== null && !isNaN(savedApiInterval) ? parseInt(savedApiInterval) : 30000;
        }
        // 监听页面可见性变化
        this.handleVisibilityChange = this.handleVisibilityChange.bind(this);
        document.addEventListener('visibilitychange', this.handleVisibilityChange);

        // 监听页面卸载事件，确保保存状态
        this.handleBeforeUnload = this.handleBeforeUnload.bind(this);
        window.addEventListener('beforeunload', this.handleBeforeUnload);
        this.bgLayer.style.position = 'fixed';
        this.bgLayer.style.top = 0;
        this.bgLayer.style.left = 0;
        this.bgLayer.style.width = '100vw';
        this.bgLayer.style.height = '100vh';
        this.bgLayer.style.zIndex = '-1';
        this.bgLayer.style.transition = 'opacity 1s';
        this.bgLayer.style.opacity = 1;
        this.bgLayer.style.backgroundSize = 'cover';
        this.bgLayer.style.backgroundColor = '#000000';
        this.bgLayer.style.backgroundPosition = 'center';
        this.bgLayer.style.filter = 'brightness(0.68)'
        this.container.style.backgroundColor = '#000000';
    }

    setBg(url) {
        // 切换时先预加载目标图片，加载完成后再切换显示
        const img = new Image();
        img.onload = () => {
            if (this.isInitialLoad) {
                // 初始加载时，先设置背景图再添加到页面
                this.bgLayer.style.backgroundImage = `url(${url})`;
                this.container.appendChild(this.bgLayer);
                this.isInitialLoad = false;
            } else {
                this.effect(this.bgLayer, url);
            }
            if(!this.isApiMode) {
                this.scheduleNext();
            }
        };
        img.onerror = () => {
            // 加载失败时处理
            console.warn('背景图片加载失败:', url);
            if (this.isInitialLoad) {
                // 初始加载失败时，也添加背景层到页面
                this.container.appendChild(this.bgLayer);
                this.isInitialLoad = false;
            }
        };
        img.src = url;
    }

    next() {
        const nextIndex = (this.index + 1) % this.images.length;
        const nextUrl = this.images[nextIndex];
        // 切换前先预加载
        const img = new Image();
        img.onload = () => {
            this.index = nextIndex;
            // 保存索引到localStorage
            localStorage.setItem('bgSwitcherIndex', this.index);
            this.effect(this.bgLayer, nextUrl);
            this.scheduleNext();
        };
        img.onerror = () => {
            // 加载失败时跳过
            console.warn('背景图片加载失败:', nextUrl);
            this.scheduleNext();
        };
        img.src = nextUrl;
    }

    prev() {
        const prevIndex = (this.index - 1 + this.images.length) % this.images.length;
        const prevUrl = this.images[prevIndex];
        // 切换前先预加载
        const img = new Image();
        img.onload = () => {
            this.index = prevIndex;
            // 保存索引到localStorage
            localStorage.setItem('bgSwitcherIndex', this.index);
            this.effect(this.bgLayer, prevUrl);
            this.scheduleNext();
        };
        img.onerror = () => {
            // 加载失败时跳过
            console.warn('背景图片加载失败:', prevUrl);
            this.scheduleNext();
        };
        img.src = prevUrl;
    }

    start() {
        if (this.timer || this.apiTimer) return;

        // 如果处于API模式，启动API请求
        if (this.apiUrl) {
            this.fetchRandomWallpaper();
        } else {
            // 否则使用默认轮播
            this.setBg(this.images[this.index]);
        }
    }

    /**
     * 安排下一次背景切换
     */
    scheduleNext() {
        if (this.timer) {
            clearTimeout(this.timer);
        }

        // 记录开始时间
        this.startTime = Date.now();

        // 使用剩余时间或默认间隔
        const timeToWait = this.remainingTime > 0 ? this.remainingTime : this.interval;

        this.timer = setTimeout(() => {
            this.remainingTime = this.interval; // 重置剩余时间
            // 保存剩余时间到localStorage
            localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
            this.next();
        }, timeToWait);
    }

    /**
     * 处理页面可见性变化
     */
    handleVisibilityChange() {
        if (document.hidden) {
            // 页面不可见时，暂停计时器并计算剩余时间
            if (this.timer) {
                const elapsedTime = Date.now() - this.startTime;
                this.remainingTime = Math.max(0, this.remainingTime - elapsedTime);
                // 保存剩余时间到localStorage
                localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
                clearTimeout(this.timer);
                this.timer = null;
            }
            // 暂停API计时器
            if (this.apiTimer) {
                const elapsedTime = Date.now() - this.startTime;
                this.remainingTime = Math.max(0, this.remainingTime - elapsedTime);
                // 保存剩余时间到localStorage
                localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
                clearTimeout(this.apiTimer);
                this.apiTimer = null;
            }
        } else {
            // 页面可见时，恢复计时器
            if (!this.timer && !this.apiTimer && !this.apiUrl) {
                // 如果没有活跃的计时器，使用默认的轮播
                this.scheduleNext();
            } else if (this.apiTimer === null && this.apiUrl) {
                // 如果处于API模式但计时器未运行，恢复API请求
                this.scheduleNextApiRequest();
            }
        }
    }

    /**
     * 处理页面卸载事件，确保保存状态
     */
    handleBeforeUnload() {
        // 保存当前索引
        localStorage.setItem('bgSwitcherIndex', this.index);

        // 保存API模式状态
        localStorage.setItem('bgSwitcherIsApiMode', !!this.apiUrl);
        if (this.apiUrl) {
            localStorage.setItem('bgSwitcherApiUrl', this.apiUrl);
            localStorage.setItem('bgSwitcherApiInterval', this.apiInterval);
        }

        // 如果计时器在运行，计算并保存剩余时间
        if (this.timer || this.apiTimer) {
            const elapsedTime = Date.now() - this.startTime;
            this.remainingTime = Math.max(0, this.remainingTime - elapsedTime);
            localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
        }
    }

    stop() {
        if (this.timer) {
            clearTimeout(this.timer);
            this.timer = null;
        }
        // 重置剩余时间
        this.remainingTime = this.interval;
        // 保存剩余时间到localStorage
        localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
    }

    /**
     * 从API获取随机壁纸并定期更新
     * @param {string} apiUrl - 获取随机壁纸的API地址
     * @param {number} interval - 请求间隔时间(毫秒)
     */
    startRandomApiSwitch(apiUrl, interval = 30000) {
        this.stop(); // 停止当前的轮播
        this.apiInterval = interval;
        this.apiUrl = apiUrl;

        // 创建专用的API计时器
        this.apiTimer = null;

        // 立即请求一次
        this.fetchRandomWallpaper();
    }

    /**
     * 从API获取随机壁纸
     */
    fetchRandomWallpaper() {
        // 记录开始时间，用于计算剩余时间
        this.startTime = Date.now();
        this.remainingTime = this.apiInterval;

        fetch(this.apiUrl)
            .then(response => {
                console.log(response);
                
                if (!response.ok) {
                    throw new Error(`HTTP error! status: ${response.status}`);
                }
                return response.json();
            })
            .then(data => {
                // 假设API返回的数据格式为 { wallpaperUrl: '图片地址' }
                const wallpaperUrl = data.wallpaperUrl || data.url || data.image;
                if (wallpaperUrl) {
                    // 预加载图片
                    const img = new Image();
                    img.onload = () => {
                        if (this.isInitialLoad) {
                            // 初始加载时，先设置背景图再添加到页面
                            this.container.appendChild(this.bgLayer);
                            this.isInitialLoad = false;
                        }
                        // 保存当前索引（使用-1标记这是API获取的图片）
                        this.index = -1;
                        localStorage.setItem('bgSwitcherIndex', -1);
                        this.effect(this.bgLayer, wallpaperUrl);
                        this.scheduleNextApiRequest();
                    };
                    img.onerror = () => {
                        console.warn('API返回的壁纸加载失败:', wallpaperUrl);
                        this.scheduleNextApiRequest();
                    };
                    img.src = wallpaperUrl;
                    
                } else {
                    console.warn('背景图片加载失败:', url);
                    if (this.isInitialLoad) {
                        console.warn('API返回的数据格式不正确，未找到壁纸地址');
                        // 初始加载失败时，也添加背景层到页面
                        this.container.appendChild(this.bgLayer);
                        this.isInitialLoad = false;
                    }
                    this.scheduleNextApiRequest();
                }
            })
            .catch(error => {
                console.error('获取随机壁纸失败:', error);
                this.scheduleNextApiRequest();
            });
    }

    /**
     * 安排下一次API请求
     */
    scheduleNextApiRequest() {
        if (this.apiTimer) {
            clearTimeout(this.apiTimer);
        }

        // 使用剩余时间或默认间隔
        const timeToWait = this.remainingTime > 0 ? this.remainingTime : this.apiInterval;

        this.apiTimer = setTimeout(() => {
            this.remainingTime = this.apiInterval; // 重置剩余时间
            localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
            this.fetchRandomWallpaper();
        }, timeToWait);
    }

    /**
     * 停止API随机壁纸请求
     */
    stopRandomApiSwitch() {
        if (this.apiTimer) {
            clearTimeout(this.apiTimer);
            this.apiTimer = null;
        }
        this.apiUrl = null
        // 重置剩余时间
        this.remainingTime = this.interval;
        localStorage.setItem('bgSwitcherRemainingTime', this.remainingTime);
    }

    static fadeEffect(layer, url) {
        layer.style.transition = 'opacity 1s';
        layer.style.opacity = 0;
        setTimeout(() => {
            layer.style.backgroundImage = `url(${url})`;
            layer.style.opacity = 1;
        }, 500);
    }
}

// 使用示例
// 1. 默认本地图片轮播
// const images = [
//     '/static/bg2.webp',
//     '/static/bg.jpg',
// ];
// const bgSwitcher = new BgSwitcher(images, { interval: 5000 });
// 启动轮播
// bgSwitcher.start();

// 2. 随机API壁纸示例
// 创建一个新的BgSwitcher实例用于API模式
const apiBgSwitcher = new BgSwitcher([], { interval: 5000 }); // API模式不需要本地图片列表

// 模拟API函数，实际使用时替换为真实API地址
function createMockWallpaperApi() {
    // 模拟壁纸地址库
    const mockWallpapers = [
        '/static/bg2.webp',
        '/static/bg.jpg',
    ];

    // 创建一个简单的服务器端点
    if (window.mockWallpaperServer) {
        clearInterval(window.mockWallpaperServer);
    }

    // 模拟API响应
    window.fetchRandomWallpaper = function () {
        return new Promise((resolve) => {
            setTimeout(() => {
                const randomIndex = Math.floor(Math.random() * mockWallpapers.length);
                resolve({
                    ok: true,
                    json() {
                        return {
                            wallpaperUrl: mockWallpapers[randomIndex]
                        }
                    }
                });
            }, 500);
        });
    };

    // 替换原生fetch以模拟API调用
    window.originalFetch = window.fetch;
    window.fetch = function (url) {
        if (url === '/api/random-wallpaper') {
            return window.fetchRandomWallpaper();
        }
        return window.originalFetch(url);
    };

    console.log('模拟壁纸API已启动');
}

// 初始化模拟API
createMockWallpaperApi();

// 启动API模式的随机壁纸切换（每10秒请求一次）
apiBgSwitcher.startRandomApiSwitch('/api/random-wallpaper', 10000);

fetch("https://pic.xieyaxin.top/random.php")
    .then(response => {
        if(response.body instanceof ReadableStream) {
            return response.blob()
        }
        return response.json()
    })
    .then(data => {
        console.log(URL.createObjectURL(data));

    })

// 要停止API模式，使用
// apiBgSwitcher.stopRandomApiSwitch();

// 要切换回本地图片轮播，使用
// apiBgSwitcher.stopRandomApiSwitch();
// apiBgSwitcher.start();

// 启动默认轮播
// bgSwitcher.start();