// ==UserScript==
// @name         THU PDF Downloader - 清华大学图书馆/PDF.js 强制下载
// @namespace    http://tampermonkey.net/
// @version      2.5
// @description  专门针对清华大学图书馆、学位论文等 PDF.js 访问限制场景。直接从浏览器内存中提取 PDF 原始流并下载，支持页面标题重命名。
// @author       王一航
// @match        *://newetds.lib.tsinghua.edu.cn/*
// @match        *://*/*
// @grant        none
// @license      MIT
// @downloadURL https://update.greasyfork.icu/scripts/565801/THU%20PDF%20Downloader%20-%20%E6%B8%85%E5%8D%8E%E5%A4%A7%E5%AD%A6%E5%9B%BE%E4%B9%A6%E9%A6%86PDFjs%20%E5%BC%BA%E5%88%B6%E4%B8%8B%E8%BD%BD.user.js
// @updateURL https://update.greasyfork.icu/scripts/565801/THU%20PDF%20Downloader%20-%20%E6%B8%85%E5%8D%8E%E5%A4%A7%E5%AD%A6%E5%9B%BE%E4%B9%A6%E9%A6%86PDFjs%20%E5%BC%BA%E5%88%B6%E4%B8%8B%E8%BD%BD.meta.js
// ==/UserScript==

(function() {
    'use strict';

    // === UI 配置 ===
    const CONFIG = {
        mainColor: '#660874', // 清华紫
        hoverColor: '#8c259d',
        textColor: '#ffffff',
        position: { bottom: '20px', right: '20px' },
        zIndex: '2147483647'
    };

    // 定义按钮创建逻辑（封装成函数，稍后调用）
    function initButton(app) {
        // 防止重复添加
        if (document.getElementById('thu-pdf-downloader-container')) return;

        const container = document.createElement('div');
        container.id = 'thu-pdf-downloader-container';
        
        // 注入样式
        const style = document.createElement('style');
        style.innerHTML = `
            #thu-pdf-downloader-container {
                position: fixed;
                bottom: ${CONFIG.position.bottom};
                right: ${CONFIG.position.right};
                z-index: ${CONFIG.zIndex};
                font-family: sans-serif;
            }
            #thu-pdf-btn {
                display: flex;
                align-items: center;
                justify-content: center;
                background-color: ${CONFIG.mainColor};
                color: ${CONFIG.textColor};
                border: none;
                border-radius: 4px;
                padding: 8px 16px;
                font-size: 14px;
                font-weight: 600;
                cursor: pointer;
                box-shadow: 0 2px 5px rgba(0,0,0,0.2);
                transition: all 0.2s ease;
                user-select: none;
            }
            #thu-pdf-btn:hover {
                background-color: ${CONFIG.hoverColor};
                transform: translateY(-1px);
            }
            #thu-pdf-btn svg {
                width: 16px;
                height: 16px;
                margin-right: 8px;
                fill: currentColor;
            }
        `;
        document.head.appendChild(style);

        const btn = document.createElement('div');
        btn.id = 'thu-pdf-btn';
        btn.innerHTML = `
            <svg viewBox="0 0 24 24"><path d="M5,20H19V18H5M19,9H15V3H9V9H5L12,16L19,9Z" /></svg>
            <span>下载 PDF</span>
        `;
        btn.title = "检测到 PDF.js 实例，点击强制下载";

        // 点击事件
        btn.onclick = async () => {
            const updateState = (text, bg) => {
                btn.querySelector('span').innerText = text;
                if(bg) btn.style.backgroundColor = bg;
            };

            updateState('处理中...', '#555');

            try {
                // 直接使用传入的 app 实例，不再递归查找，确保 100% 准确
                const data = await app.pdfDocument.getData();
                const blob = new Blob([data], { type: 'application/pdf' });
                const url = URL.createObjectURL(blob);
                
                const rawTitle = document.title || 'downloaded_document';
                const safeTitle = rawTitle.replace(/[\\/:*?"<>|]/g, '_').trim();
                
                const a = document.createElement('a');
                a.href = url;
                a.download = `${safeTitle}.pdf`;
                document.body.appendChild(a);
                a.click();
                
                setTimeout(() => {
                    document.body.removeChild(a);
                    URL.revokeObjectURL(url);
                    updateState('成功!', '#28a745');
                    setTimeout(() => updateState('下载 PDF', CONFIG.mainColor), 2000);
                }, 100);

            } catch (err) {
                console.error("[THU-PDF] Error:", err);
                alert("下载出错，请检查控制台");
                updateState('出错', '#dc3545');
            }
        };

        container.appendChild(btn);
        document.body.appendChild(container);
        console.log("[THU-PDF] 按钮已注入 (针对当前 Context)");
    }

    // === 核心修改：轮询检测机制 ===
    // 不再默认显示按钮，而是查找是否存在 PDFViewerApplication
    const checkInterval = setInterval(() => {
        // 1. 检测全局对象是否存在
        if (window.PDFViewerApplication && window.PDFViewerApplication.pdfDocument) {
            clearInterval(checkInterval);
            initButton(window.PDFViewerApplication);
        }
    }, 1000); // 每秒检查一次

    // 10秒后停止检测，节省性能 (可根据网络情况调整)
    setTimeout(() => clearInterval(checkInterval), 15000);

})();