// ==UserScript==
// @name         Global Image Quick Saver PC
// @namespace    https://docs.scriptcat.org/
// @version      0.0.1
// @description  Alt/Option + 左键快速保存图片，全站可用，强拦截网站跳转，支持跨域图片下载
// @author       AmzBasara
// @match        *://*/*
// @grant        GM_download
// @noframes
// @run-at       document-start
// ==/UserScript==

(function () {
    'use strict';

    const SITE_NAME_MAP = {
        chatgpt: 'ChatGPT'
    };

    const IMAGE_EXT_REG = /\.(jpg|jpeg|png|webp|gif|bmp|avif|svg)(\?|#|$)/i;

    let suppressUntil = 0;
    let lastDownloadUrl = '';

    function isAltLeftClick(event) {
        return event.button === 0 && event.altKey;
    }

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

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

    function findImageElement(target) {
        if (!target) return null;

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

        return target.closest?.('img') || null;
    }

    function getImageUrl(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 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);

            // 正常 URL 路径里带后缀
            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();
            }

            // 兼容这种代理图片：
            // https://img03.sogoucdn.com/.../?appid=122&url=https://xxx.jpg
            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 getDateTimeString() {
        const d = new Date();

        const yyyy = d.getFullYear();
        const MM = String(d.getMonth() + 1).padStart(2, '0');
        const dd = String(d.getDate()).padStart(2, '0');

        const hh = String(d.getHours()).padStart(2, '0');
        const mm = String(d.getMinutes()).padStart(2, '0');
        const ss = String(d.getSeconds()).padStart(2, '0');

        // Windows 安全格式，不能用冒号
        return `${yyyy}-${MM}-${dd} ${hh}-${mm}-${ss}`;
    }

    function getFilename(url, mimeType = '') {
        const siteName = getSiteName();
        const dateTime = getDateTimeString();
        const ext = getExtFromMime(mimeType) || getExtFromUrl(url) || 'jpg';

        return sanitizeFilename(`${siteName}-${dateTime}.${ext}`);
    }

    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 = getFilename(url, blob.type);

        triggerDownloadByA(objectUrl, filename);

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

    async function saveImageUrl(url) {
        if (!url) {
            console.warn('[Image Quick Saver] 没有找到图片地址');
            return;
        }

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

        console.log('[Image Quick Saver] 尝试下载：', absoluteUrl);

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

        // blob: 只能 fetch 当前页面里的 blob
        if (absoluteUrl.startsWith('blob:')) {
            try {
                await downloadByFetch(absoluteUrl);
                return;
            } catch (err) {
                console.warn('[Image Quick Saver] blob fetch 失败：', err);
                triggerDownloadByA(absoluteUrl, filename);
                return;
            }
        }

        // 普通 http/https 图片，优先 GM_download，跨域更稳
        try {
            await downloadByGM(absoluteUrl, filename);
            return;
        } catch (err) {
            console.warn('[Image Quick Saver] GM_download 失败，尝试 fetch：', err);
        }

        try {
            await downloadByFetch(absoluteUrl);
            return;
        } catch (err) {
            console.warn('[Image Quick Saver] fetch 失败，尝试 a[download]：', err);
        }

        triggerDownloadByA(absoluteUrl, filename);
    }

    function handleAltImageEvent(event) {
        if (!isAltLeftClick(event)) return;

        const img = findImageElement(event.target);
        if (!img) return;

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

        suppressUntil = Date.now() + 1500;
        lastDownloadUrl = url;

        suppressEvent(event);

        saveImageUrl(url);
    }

    /**
     * 第一组：真正触发下载。
     * pointerdown 比 mousedown 更早，很多现代站点会优先监听 pointer 事件。
     */
    window.addEventListener('pointerdown', handleAltImageEvent, true);
    document.addEventListener('pointerdown', handleAltImageEvent, true);

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

    /**
     * 第二组：只负责阻止网站后续事件。
     * 防止网站在 pointerup / mouseup / click 阶段打开 blob 页面。
     */
    [
        'pointerup',
        'mouseup',
        'click',
        'auxclick',
        'dblclick'
    ].forEach(eventName => {
        window.addEventListener(
            eventName,
            function (event) {
                if (!shouldSuppress()) return;

                const img = findImageElement(event.target);
                if (!img) return;

                suppressEvent(event);
            },
            true
        );

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

                const img = findImageElement(event.target);
                if (!img) return;

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

    console.log('[Image Quick Saver] 已启用：Alt/Option + 左键保存图片，强拦截跳转版');
})();