// ==UserScript==
// @name         图片快速保存
// @namespace    https://docs.scriptcat.org/
// @version      0.0.2
// @description  按 Alt/Option 高亮可下载图片，左键点击快速保存，支持 img、blob、background-image
// @author       You
// @match        *://*/*
// @grant        GM_download
// @noframes
// @run-at       document-start
// ==/UserScript==

(function () {
    'use strict';

    /******************************************************************
     * 配置区
     ******************************************************************/

    const CONFIG = {
        /**
         * 触发快捷键
         *
         * 可选值：
         * alt   ：Windows/Linux 的 Alt，macOS 的 Option
         * ctrl  ：Ctrl / Control
         * shift ：Shift
         * meta  ：Windows 键 / macOS Command
         *
         * 当前需求：Alt / Option
         */
        modifierKey: 'alt',

        /**
         * 文件名格式
         *
         * 可用变量：
         * {site}     当前网站名，例如 ChatGPT / XChina / Fuliba2024
         * {datetime} 当前日期时间
         * {ext}      图片后缀，例如 jpg / png / webp
         *
         * 示例：
         * '{site}-{datetime}.{ext}'
         * '{datetime}-{site}.{ext}'
         * '{site}/{datetime}.{ext}'  // 某些脚本管理器可能支持子目录，浏览器原生下载不一定支持
         */
        filenameFormat: '{site}-{datetime}.{ext}',

        /**
         * 时间格式
         *
         * 可用变量：
         * YYYY 年
         * MM   月
         * DD   日
         * HH   时
         * mm   分
         * ss   秒
         *
         * 注意：
         * Windows 文件名不能包含英文冒号 :
         * 所以默认用 HH-mm-ss，而不是 HH:mm:ss
         */
        datetimeFormat: 'YYYY-MM-DD HH-mm-ss',

        /**
         * 高亮阴影颜色
         */
        highlightColor: '#409EFF',

        /**
         * 是否启用可下载图片高亮
         */
        enableHighlight: true,

        /**
         * 防止网站点击事件继续跳转的拦截时间，单位毫秒
         */
        suppressDuration: 1500
    };

    /**
     * 站点名特殊映射
     * 只影响文件名，不影响下载功能
     */
    const SITE_NAME_MAP = {
        chatgpt: 'ChatGPT',
        xchina: 'XChina'
    };

    /******************************************************************
     * 常量区
     ******************************************************************/

    const IMAGE_EXT_REG = /\.(jpg|jpeg|png|webp|gif|bmp|avif|svg)(\?|#|$)/i;
    const HIGHLIGHT_CLASS = 'image-quick-save-highlight';
    const HIGHLIGHT_STYLE_ID = 'image-quick-save-style';

    /******************************************************************
     * 状态区
     ******************************************************************/

    let modifierMode = false;
    let suppressUntil = 0;
    let scanTimer = null;
    let highlightedElements = new Set();

    injectHighlightStyle();

    /******************************************************************
     * 快捷键判断
     ******************************************************************/

    function isModifierPressed(event) {
        switch (CONFIG.modifierKey) {
            case 'alt':
                return event.altKey;
            case 'ctrl':
                return event.ctrlKey;
            case 'shift':
                return event.shiftKey;
            case 'meta':
                return event.metaKey;
            default:
                return event.altKey;
        }
    }

    function getModifierEventKeyName() {
        switch (CONFIG.modifierKey) {
            case 'alt':
                return 'Alt';
            case 'ctrl':
                return 'Control';
            case 'shift':
                return 'Shift';
            case 'meta':
                return 'Meta';
            default:
                return 'Alt';
        }
    }

    function isModifierLeftClick(event) {
        return event.button === 0 && isModifierPressed(event);
    }

    /******************************************************************
     * 高亮样式
     ******************************************************************/

    function injectHighlightStyle() {
        const style = document.createElement('style');
        style.id = HIGHLIGHT_STYLE_ID;
        style.textContent = `
            .${HIGHLIGHT_CLASS} {
                box-shadow:
                    0 0 0 3px ${CONFIG.highlightColor},
                    0 0 12px 4px ${CONFIG.highlightColor} !important;
                cursor: pointer !important;
                transition: box-shadow 0.12s ease !important;
            }
        `;

        const append = () => {
            if (!document.getElementById(HIGHLIGHT_STYLE_ID)) {
                document.documentElement.appendChild(style);
            }
        };

        if (document.documentElement) {
            append();
        } else {
            document.addEventListener('DOMContentLoaded', append, { once: true });
        }
    }

    /******************************************************************
     * 事件拦截
     ******************************************************************/

    function shouldSuppress() {
        return Date.now() < suppressUntil;
    }

    function suppressEvent(event) {
        event.preventDefault();
        event.stopPropagation();
        event.stopImmediatePropagation();
    }

    /******************************************************************
     * 图片识别
     ******************************************************************/

    function getBackgroundImageUrl(element) {
        if (!element || element.nodeType !== 1) return '';

        const style = window.getComputedStyle(element);
        const bg = style.backgroundImage || '';

        if (!bg || bg === 'none') return '';

        const match = bg.match(/url\(["']?(.*?)["']?\)/i);
        if (!match || !match[1]) return '';

        return match[1];
    }

    function isDownloadableImageUrl(url) {
        if (!url) return false;

        return (
            url.startsWith('blob:') ||
            url.startsWith('data:image/') ||
            IMAGE_EXT_REG.test(url)
        );
    }

    function getImgUrl(img) {
        if (!img) return '';

        return (
            img.currentSrc ||
            img.src ||
            img.getAttribute('src') ||
            img.getAttribute('data-src') ||
            img.getAttribute('data-original') ||
            img.getAttribute('data-lazy-src') ||
            img.getAttribute('data-url') ||
            ''
        );
    }

    function getImageUrl(element) {
        if (!element || element.nodeType !== 1) return '';

        if (element.tagName === 'IMG') {
            return getImgUrl(element);
        }

        const bgUrl = getBackgroundImageUrl(element);
        if (bgUrl) {
            return bgUrl;
        }

        const link = element.closest?.('a[href]');
        if (link) {
            const href = link.href || link.getAttribute('href') || '';
            if (isDownloadableImageUrl(href)) {
                return href;
            }
        }

        return '';
    }

    function findDownloadElement(target) {
        if (!target || target.nodeType !== 1) return null;

        const img = target.closest?.('img');
        if (img && getImgUrl(img)) {
            return img;
        }

        let el = target;

        while (el && el !== document.documentElement && el.nodeType === 1) {
            const bgUrl = getBackgroundImageUrl(el);
            if (bgUrl) {
                return el;
            }

            const link = el.closest?.('a[href]');
            if (link) {
                const href = link.href || link.getAttribute('href') || '';
                if (isDownloadableImageUrl(href)) {
                    return link;
                }
            }

            el = el.parentElement;
        }

        return null;
    }

    /******************************************************************
     * 高亮扫描
     ******************************************************************/

    function scanAndHighlightImages() {
        if (!modifierMode || !CONFIG.enableHighlight) return;

        clearHighlights();

        const candidates = new Set();

        document.querySelectorAll('img').forEach(img => {
            if (getImgUrl(img)) {
                candidates.add(img);
            }
        });

        document.querySelectorAll('[style*="background-image"], [role="img"], .img').forEach(el => {
            if (getBackgroundImageUrl(el)) {
                candidates.add(el);
            }
        });

        document.querySelectorAll('a[href]').forEach(a => {
            const href = a.href || a.getAttribute('href') || '';
            if (isDownloadableImageUrl(href)) {
                candidates.add(a);
            }
        });

        candidates.forEach(el => {
            if (!isVisibleElement(el)) return;

            el.classList.add(HIGHLIGHT_CLASS);
            highlightedElements.add(el);
        });
    }

    function isVisibleElement(el) {
        if (!el || el.nodeType !== 1) return false;

        const rect = el.getBoundingClientRect();
        if (rect.width < 8 || rect.height < 8) return false;

        const style = window.getComputedStyle(el);
        if (style.display === 'none') return false;
        if (style.visibility === 'hidden') return false;
        if (Number(style.opacity) === 0) return false;

        return true;
    }

    function clearHighlights() {
        highlightedElements.forEach(el => {
            try {
                el.classList.remove(HIGHLIGHT_CLASS);
            } catch (_) {}
        });

        highlightedElements.clear();
    }

    function scheduleScan() {
        if (!modifierMode || !CONFIG.enableHighlight) return;

        clearTimeout(scanTimer);
        scanTimer = setTimeout(scanAndHighlightImages, 80);
    }

    /******************************************************************
     * 文件名生成
     ******************************************************************/

    function sanitizeFilename(name) {
        return String(name || '')
            .replace(/[\\/:*?"<>|]/g, '_')
            .replace(/\s+/g, ' ')
            .trim()
            .slice(0, 150);
    }

    function getExtFromMime(mimeType) {
        const map = {
            'image/jpeg': 'jpg',
            'image/jpg': 'jpg',
            'image/png': 'png',
            'image/webp': 'webp',
            'image/gif': 'gif',
            'image/svg+xml': 'svg',
            'image/bmp': 'bmp',
            'image/avif': 'avif'
        };

        return map[String(mimeType || '').toLowerCase()] || '';
    }

    function getExtFromUrl(url) {
        try {
            const u = new URL(url, location.href);

            let match = u.pathname.match(/\.(jpg|jpeg|png|webp|gif|bmp|avif|svg)$/i);
            if (match) {
                return match[1].toLowerCase() === 'jpeg' ? 'jpg' : match[1].toLowerCase();
            }

            const innerUrl = u.searchParams.get('url');
            if (innerUrl) {
                match = innerUrl.match(/\.(jpg|jpeg|png|webp|gif|bmp|avif|svg)(\?|#|$)/i);
                if (match) {
                    return match[1].toLowerCase() === 'jpeg' ? 'jpg' : match[1].toLowerCase();
                }
            }
        } catch (_) {}

        return '';
    }

    function getSiteName() {
        const hostname = location.hostname || 'image';

        if (hostname === 'localhost') {
            return 'Localhost';
        }

        if (/^\d+\.\d+\.\d+\.\d+$/.test(hostname)) {
            return sanitizeFilename(hostname);
        }

        const host = hostname.replace(/^www\./i, '');
        const parts = host.split('.').filter(Boolean);

        let core = parts[0] || 'image';

        if (parts.length >= 2) {
            core = parts[parts.length - 2];

            const last = parts[parts.length - 1];
            const secondLast = parts[parts.length - 2];

            if (
                parts.length >= 3 &&
                ['uk', 'jp', 'cn', 'au', 'hk'].includes(last) &&
                ['co', 'com', 'net', 'org', 'gov', 'edu'].includes(secondLast)
            ) {
                core = parts[parts.length - 3];
            }
        }

        const lowerCore = core.toLowerCase();

        if (SITE_NAME_MAP[lowerCore]) {
            return sanitizeFilename(SITE_NAME_MAP[lowerCore]);
        }

        const pretty = core
            .split(/[-_]+/)
            .filter(Boolean)
            .map(word => word.charAt(0).toUpperCase() + word.slice(1))
            .join('');

        return sanitizeFilename(pretty || 'Image');
    }

    function pad2(value) {
        return String(value).padStart(2, '0');
    }

    function formatDateTime(date, format) {
        const tokens = {
            YYYY: String(date.getFullYear()),
            MM: pad2(date.getMonth() + 1),
            DD: pad2(date.getDate()),
            HH: pad2(date.getHours()),
            mm: pad2(date.getMinutes()),
            ss: pad2(date.getSeconds())
        };

        return String(format || 'YYYY-MM-DD HH-mm-ss').replace(
            /YYYY|MM|DD|HH|mm|ss/g,
            token => tokens[token]
        );
    }

    function getDateTimeString() {
        return formatDateTime(new Date(), CONFIG.datetimeFormat);
    }

    function buildFilename(url, mimeType = '') {
        const site = getSiteName();
        const datetime = getDateTimeString();
        const ext = getExtFromMime(mimeType) || getExtFromUrl(url) || 'jpg';

        const filename = CONFIG.filenameFormat
            .replaceAll('{site}', site)
            .replaceAll('{datetime}', datetime)
            .replaceAll('{ext}', ext);

        return sanitizeFilename(filename);
    }

    /******************************************************************
     * 下载逻辑
     ******************************************************************/

    function triggerDownloadByA(href, filename) {
        const a = document.createElement('a');
        a.href = href;
        a.download = filename;
        a.rel = 'noopener noreferrer';
        a.style.display = 'none';

        document.documentElement.appendChild(a);
        a.click();
        a.remove();
    }

    function downloadByGM(url, filename) {
        return new Promise((resolve, reject) => {
            if (typeof GM_download !== 'function') {
                reject(new Error('GM_download 不可用'));
                return;
            }

            GM_download({
                url,
                name: filename,
                saveAs: false,
                onload: resolve,
                onerror: reject,
                ontimeout: reject
            });
        });
    }

    async function downloadByFetch(url) {
        const response = await fetch(url, {
            credentials: 'omit',
            cache: 'no-store'
        });

        if (!response.ok) {
            throw new Error(`HTTP ${response.status}`);
        }

        const blob = await response.blob();
        const objectUrl = URL.createObjectURL(blob);
        const filename = buildFilename(url, blob.type);

        triggerDownloadByA(objectUrl, filename);

        setTimeout(() => {
            URL.revokeObjectURL(objectUrl);
        }, 3000);
    }

    async function saveImageUrl(url) {
        if (!url) {
            console.warn('[图片快速保存] 没有找到图片地址');
            return;
        }

        const absoluteUrl = new URL(url, location.href).href;
        const filename = buildFilename(absoluteUrl);

        console.log('[图片快速保存] 尝试下载：', absoluteUrl);

        if (absoluteUrl.startsWith('data:image/')) {
            triggerDownloadByA(absoluteUrl, filename);
            return;
        }

        if (absoluteUrl.startsWith('blob:')) {
            try {
                await downloadByFetch(absoluteUrl);
                return;
            } catch (err) {
                console.warn('[图片快速保存] blob fetch 失败：', err);
                triggerDownloadByA(absoluteUrl, filename);
                return;
            }
        }

        try {
            await downloadByGM(absoluteUrl, filename);
            return;
        } catch (err) {
            console.warn('[图片快速保存] GM_download 失败，尝试 fetch：', err);
        }

        try {
            await downloadByFetch(absoluteUrl);
            return;
        } catch (err) {
            console.warn('[图片快速保存] fetch 失败，尝试 a[download]：', err);
        }

        triggerDownloadByA(absoluteUrl, filename);
    }

    /******************************************************************
     * 快捷键模式
     ******************************************************************/

    window.addEventListener(
        'keydown',
        function (event) {
            if (event.key !== getModifierEventKeyName()) return;
            if (modifierMode) return;

            modifierMode = true;
            scanAndHighlightImages();
        },
        true
    );

    window.addEventListener(
        'keyup',
        function (event) {
            if (event.key !== getModifierEventKeyName()) return;

            modifierMode = false;
            clearHighlights();
        },
        true
    );

    window.addEventListener(
        'blur',
        function () {
            modifierMode = false;
            clearHighlights();
        },
        true
    );

    window.addEventListener(
        'scroll',
        scheduleScan,
        true
    );

    const observer = new MutationObserver(function () {
        scheduleScan();
    });

    function startObserver() {
        if (!document.documentElement) return;

        observer.observe(document.documentElement, {
            childList: true,
            subtree: true,
            attributes: true,
            attributeFilter: ['src', 'srcset', 'style', 'class']
        });
    }

    if (document.documentElement) {
        startObserver();
    } else {
        document.addEventListener('DOMContentLoaded', startObserver, { once: true });
    }

    /******************************************************************
     * 鼠标点击保存
     ******************************************************************/

    function handleModifierImageEvent(event) {
        if (!isModifierLeftClick(event)) return;

        const element = findDownloadElement(event.target);
        if (!element) return;

        const url = getImageUrl(element);
        if (!url) return;

        suppressUntil = Date.now() + CONFIG.suppressDuration;

        suppressEvent(event);
        saveImageUrl(url);
    }

    window.addEventListener('pointerdown', handleModifierImageEvent, true);
    document.addEventListener('pointerdown', handleModifierImageEvent, true);

    window.addEventListener('mousedown', handleModifierImageEvent, true);
    document.addEventListener('mousedown', handleModifierImageEvent, true);

    [
        'pointerup',
        'mouseup',
        'click',
        'auxclick',
        'dblclick'
    ].forEach(eventName => {
        window.addEventListener(
            eventName,
            function (event) {
                if (!shouldSuppress()) return;

                const element = findDownloadElement(event.target);
                if (!element) return;

                suppressEvent(event);
            },
            true
        );

        document.addEventListener(
            eventName,
            function (event) {
                if (!shouldSuppress()) return;

                const element = findDownloadElement(event.target);
                if (!element) return;

                suppressEvent(event);
            },
            true
        );
    });

    console.log('[图片快速保存] 已启用：按快捷键高亮图片，点击快速保存');
})();