// ==UserScript==
// @name         查看图片
// @namespace    http://tampermonkey.net/
// @version      3.6
// @description  每次打开重新筛选，保持浏览位置；优先大图≥1000×1000，跳过广告；右下角动态按钮，刷新基于页码定位，支持跳转
// @author       Cooper
// @match        *://*/*
// ==/UserScript==

(function() {
    'use strict';

    let lastViewedSrc = null;
    let pendingPageIndex = null;   // 用于刷新时指定目标页码（非 null 时优先使用）

    // 按钮容器
    const btnBox = document.createElement("div");
    btnBox.style = `
        position:fixed; bottom:15%; right:5%;
        display:flex; flex-direction:column; align-items:center;
        gap:4px; z-index:1000000001;
    `;
    document.body.appendChild(btnBox);

    // 重载当前页按钮
    const reloadCurrentBtn = document.createElement("button");
    reloadCurrentBtn.textContent = "↺";
    reloadCurrentBtn.title = "刷新并回到当前页码（不改变页码，重载图片）";
    reloadCurrentBtn.style = `
        width:40px; height:40px; border-radius:20px;
        border:1px dashed #0d6efd;
        color:#0d6efd; font-size:18px; padding:3px 3px;
        background-color:transparent;
        display:none;
    `;
    btnBox.appendChild(reloadCurrentBtn);

    // 返回上一张并刷新按钮
    const refreshPrevBtn = document.createElement("button");
    refreshPrevBtn.textContent = "↻";
    refreshPrevBtn.title = "返回上一页码并刷新（页码-1）";
    refreshPrevBtn.style = `
        width:40px; height:40px; border-radius:20px;
        border:1px dashed #0d6efd;
        color:#0d6efd; font-size:18px; padding:3px 3px;
        background-color:transparent;
        display:none;
    `;
    btnBox.appendChild(refreshPrevBtn);

    // ON 按钮
    const flip = document.createElement("button");
    flip.textContent = "ON";
    flip.style = `
        width:40px; height:40px; border-radius:20px;
        border:1px dashed #0d6efd;
        color:#0d6efd; font-size:16px; padding:3px 3px;
        background-color:transparent;
    `;
    btnBox.appendChild(flip);

    // 跳转按钮
    const jumpBtn = document.createElement("button");
    jumpBtn.textContent = "跳";
    jumpBtn.style = `
        width:40px; height:40px; border-radius:20px;
        border:1px dashed #0d6efd;
        color:#0d6efd; font-size:14px; padding:3px 3px;
        background-color:transparent;
        display:none;
    `;
    btnBox.appendChild(jumpBtn);

    let flag = false;

    const viewerState = {
        images: null,
        jump: null,
        total: 0,
        _currentIdx: 0
    };

    // ↺ 重载当前页：记录当前页码
    reloadCurrentBtn.addEventListener("click", (e) => {
        e.stopPropagation();
        if (!flag || !viewerState.images || viewerState.images.length === 0) {
            alert("请先打开图片浏览器 (点击ON)");
            return;
        }
        pendingPageIndex = viewerState._currentIdx ?? 0;
        turnOFF();
        flag = false;
        turnON();
        flag = true;
    });

    // ↻ 返回上一页并刷新：当前页码-1（最小为0）
    refreshPrevBtn.addEventListener("click", (e) => {
        e.stopPropagation();
        if (!flag || !viewerState.images || viewerState.images.length === 0) {
            alert("请先打开图片浏览器 (点击ON)");
            return;
        }
        const curIdx = viewerState._currentIdx ?? 0;
        pendingPageIndex = Math.max(0, curIdx - 1);
        turnOFF();
        flag = false;
        turnON();
        flag = true;
    });

    flip.addEventListener("click", (e) => {
        e.stopPropagation();
        if (!flag) {
            turnON();
        } else {
            turnOFF();
        }
        flag = !flag;
        toggleExtraButtons(flag);
    });

    jumpBtn.addEventListener("click", (e) => {
        e.stopPropagation();
        if (!viewerState.jump) {
            alert("请先打开图片浏览器 (点击ON)");
            return;
        }
        const currentIdx = viewerState._currentIdx ?? 0;
        const numStr = prompt(`请输入图片序号 (1-${viewerState.total})`, currentIdx + 1);
        if (numStr === null) return;
        const num = parseInt(numStr);
        if (isNaN(num) || num < 1 || num > viewerState.total) {
            alert(`请输入 1 到 ${viewerState.total} 之间的数字`);
            return;
        }
        viewerState.jump(num - 1);
    });

    function toggleExtraButtons(visible) {
        reloadCurrentBtn.style.display = visible ? 'block' : 'none';
        refreshPrevBtn.style.display = visible ? 'block' : 'none';
        jumpBtn.style.display = visible ? 'block' : 'none';
    }

    function turnON() {
        const overlay = document.createElement("div");
        overlay.id = "img-overlay";
        overlay.style = `
            position:fixed; top:0; left:0;
            width:100%; height:100%;
            background-color:rgba(0, 0, 0, 0.8);
            display:flex; justify-content:center;
            z-index:999999999;
        `;
        document.body.appendChild(overlay);

        const imgContainer = document.createElement("div");
        imgContainer.style = `
            position:relative;
            width:100%; height:100%;
            max-width:800px; margin:0;
            display:flex; align-items:center; justify-content:center;
        `;
        overlay.appendChild(imgContainer);

        const currentImg = document.createElement("img");
        currentImg.style = `
            width:100%; height:100%;
            object-fit:contain; display:block;
        `;
        currentImg.alt = "正在重新筛选并恢复位置…";
        currentImg.style.color = 'white';
        imgContainer.appendChild(currentImg);

        const imgElements = Array.from(document.querySelectorAll("img"));
        const seen = new Set();
        const uniqueImgs = [];
        for (const img of imgElements) {
            if (img.src && !seen.has(img.src)) {
                seen.add(img.src);
                uniqueImgs.push(img);
            }
        }

        const MIN_SIZE = 1000;

        const checkIsLarge = (img) => new Promise((resolve) => {
            if (img.complete && img.naturalWidth > 0) {
                resolve(img.naturalWidth >= MIN_SIZE && img.naturalHeight >= MIN_SIZE);
                return;
            }
            const testImg = new Image();
            const timeout = setTimeout(() => {
                testImg.src = '';
                resolve(false);
            }, 2000);
            testImg.onload = () => {
                clearTimeout(timeout);
                resolve(testImg.naturalWidth >= MIN_SIZE && testImg.naturalHeight >= MIN_SIZE);
            };
            testImg.onerror = () => {
                clearTimeout(timeout);
                resolve(false);
            };
            testImg.src = img.src;
        });

        const startQuickFilter = async () => {
            let firstLargeIndex = -1;
            for (let i = 0; i < uniqueImgs.length; i++) {
                const large = await checkIsLarge(uniqueImgs[i]);
                if (large) {
                    firstLargeIndex = i;
                    break;
                }
            }

            let images = [];
            if (firstLargeIndex === -1) {
                images = uniqueImgs.map(img => img.src);
            } else {
                images = uniqueImgs.slice(firstLargeIndex).map(img => img.src);
            }

            // 决定起始索引：优先 pendingPageIndex，其次 lastViewedSrc 匹配，再默认为 0
            let startIndex = 0;
            if (pendingPageIndex !== null) {
                // 刷新按钮指定的页码，确保在合法范围
                startIndex = Math.min(pendingPageIndex, images.length - 1);
                startIndex = Math.max(0, startIndex);
                pendingPageIndex = null; // 用后即清
            } else if (lastViewedSrc && images.length > 0) {
                const foundIdx = images.indexOf(lastViewedSrc);
                if (foundIdx !== -1) {
                    startIndex = foundIdx;
                }
            }

            document.body.removeChild(overlay);
            openViewer(images, startIndex);
        };

        startQuickFilter();
    }

    function openViewer(images, startIndex) {
        const overlay = document.createElement("div");
        overlay.id = "img-overlay";
        overlay.style = `
            position:fixed; top:0; left:0;
            width:100%; height:100%;
            background-color:rgba(0, 0, 0, 0.8);
            display:flex; justify-content:center;
            z-index:999999999;
        `;
        document.body.appendChild(overlay);

        const imgContainer = document.createElement("div");
        imgContainer.style = `
            position:relative;
            width:100%; height:100%;
            max-width:800px; margin:0;
            display:flex; align-items:center; justify-content:center;
        `;
        overlay.appendChild(imgContainer);

        const currentImg = document.createElement("img");
        currentImg.style = `
            width:100%; height:100%;
            object-fit:contain; display:block;
        `;
        imgContainer.appendChild(currentImg);

        let currentIdx = startIndex;

        const showCurrentImg = () => {
            currentImg.src = images[currentIdx];
            currentImg.alt = `${currentIdx + 1}/${images.length}`;
            flip.textContent = currentIdx + 1;
            viewerState._currentIdx = currentIdx;
        };

        showCurrentImg();

        const updateLastSrc = () => {
            if (images.length > 0 && currentIdx >= 0 && currentIdx < images.length) {
                lastViewedSrc = images[currentIdx];
            }
        };
        updateLastSrc();

        viewerState.images = images;
        viewerState.jump = (index) => {
            if (index >= 0 && index < images.length) {
                currentIdx = index;
                showCurrentImg();
                updateLastSrc();
            }
        };
        viewerState.total = images.length;
        viewerState._currentIdx = currentIdx;

        overlay.addEventListener("click", (e) => {
            e.stopPropagation();
            const screenHeight = window.innerHeight;
            const clickY = e.clientY;
            if (clickY < screenHeight / 2) {
                if (currentIdx > 0) currentIdx--;
            } else {
                if (currentIdx < images.length - 1) currentIdx++;
            }
            showCurrentImg();
            updateLastSrc();
        });
    }

    function turnOFF() {
        const overlay = document.getElementById("img-overlay");
        if (overlay) {
            document.body.removeChild(overlay);
            flip.textContent = "ON";
            viewerState.jump = null;
            viewerState.total = 0;
            viewerState._currentIdx = 0;
            viewerState.images = null;
        }
    }
})();