// ==UserScript==
// @name         ChromaFlow
// @namespace    http://tampermonkey.net/
// @version      8.0
// @description  网页文字渐变色辅助阅读 (Ctrl+Shift+B 开关)：读长文对话不串行。
// @description:en  Reading focus with color gradients (Ctrl+Shift+B).
// @author       Lain1984
// @license      MIT
// @match        *://*/*
// @grant        GM_addStyle
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';

    let isEnabled = true;

    // ==========================================
    // 1. 高对比度调色盘
    // ==========================================
    const THEMES = {
        light: { c1: [210, 0, 0], mid: [30, 30, 30], c2: [0, 0, 210] },
        dark: { c1: [255, 100, 100], mid: [220, 220, 220], c2: [100, 150, 255] }
    };

    function interpolateColor(color1, color2, factor) {
        return [
            Math.round(color1[0] + factor * (color2[0] - color1[0])),
            Math.round(color1[1] + factor * (color2[1] - color1[1])),
            Math.round(color1[2] + factor * (color2[2] - color1[2]))
        ];
    }

    // ==========================================
    // 2. 环境探测与分词
    // ==========================================
    function getRealBackgroundColor() {
        const bodyBg = window.getComputedStyle(document.body).backgroundColor;
        if (bodyBg !== 'rgba(0, 0, 0, 0)' && bodyBg !== 'transparent') return bodyBg;
        if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) return 'rgb(30, 30, 30)';
        return 'rgb(255, 255, 255)';
    }

    function isDarkTheme(colorStr) {
        const rgbMatch = colorStr.match(/\d+/g);
        if (!rgbMatch || rgbMatch.length < 3) return false;
        return ((rgbMatch[0] * 299) + (rgbMatch[1] * 587) + (rgbMatch[2] * 114)) / 1000 < 128;
    }

    function tokenizeText(text) {
        const regex = /[\u4E00-\u9FFF]|\s+|[^\s\u4E00-\u9FFF]+/g;
        let result = [];
        let match;
        while ((match = regex.exec(text)) !== null) result.push(match[0]);
        return result;
    }

    // ==========================================
    // 3. 白名单与黑名单 (防止破坏 UI)
    // ==========================================
    // 【核心新增】：加入了 [data-testid="tweetText"] 以完美支持 X (Twitter) 的推文正文
    const TARGET_SELECTORS = 'p, li, blockquote, dd, dt, ms-cmark-node, .text-base, .markdown, .markdown-body, .prose, [data-testid="tweetText"]';
    
    // 黑名单保持不变，严格保护代码块和输入框
    const IGNORE_SELECTORS = 'code, pre, kbd, button, input, textarea, select, [contenteditable="true"], .inline-code';

    // ==========================================
    // 4. 安全拆词引擎 (DOM 操作)
    // ==========================================
    function wrapTextNodesSafely() {
        const blocks = document.querySelectorAll(TARGET_SELECTORS);
        
        blocks.forEach(block => {
            if (block.closest(IGNORE_SELECTORS)) return; 

            const walker = document.createTreeWalker(block, NodeFilter.SHOW_TEXT, {
                acceptNode: function(node) {
                    if (!node.nodeValue.trim()) return NodeFilter.FILTER_SKIP;
                    const parent = node.parentNode;
                    if (!parent) return NodeFilter.FILTER_SKIP;
                    
                    if (parent.classList.contains('beeline-word')) return NodeFilter.FILTER_REJECT;
                    if (parent.closest(IGNORE_SELECTORS)) return NodeFilter.FILTER_REJECT;
                    
                    return NodeFilter.FILTER_ACCEPT;
                }
            });

            let textNodes = [];
            let currentNode;
            while (currentNode = walker.nextNode()) textNodes.push(currentNode);

            textNodes.forEach(node => {
                const fragment = document.createDocumentFragment();
                const tokens = tokenizeText(node.nodeValue);
                
                tokens.forEach(token => {
                    if (token.trim() === '') {
                        fragment.appendChild(document.createTextNode(token));
                    } else {
                        const span = document.createElement('span');
                        span.textContent = token;
                        span.className = 'beeline-word';
                        span.style.transition = 'color 0.2s ease';
                        fragment.appendChild(span);
                    }
                });
                node.parentNode.replaceChild(fragment, node);
            });
        });
    }

    // ==========================================
    // 5. 全局流体上色引擎 (支持无限滚动)
    // ==========================================
    function applyGlobalColors() {
        const spans = Array.from(document.querySelectorAll('.beeline-word'));
        if (spans.length === 0) return;

        const isDark = isDarkTheme(getRealBackgroundColor());
        const theme = isDark ? THEMES.dark : THEMES.light;

        let lines = [];
        let currentLine = [];
        let lastY = -1;

        spans.forEach(span => {
            const rect = span.getBoundingClientRect();
            if (rect.width === 0 && rect.height === 0) return; 
            
            const absoluteY = Math.round((rect.top + window.scrollY) / 8) * 8; 
            
            if (lastY === -1 || Math.abs(absoluteY - lastY) > 8) { 
                if (currentLine.length > 0) lines.push(currentLine);
                currentLine = [span];
                lastY = absoluteY;
            } else {
                currentLine.push(span);
            }
        });
        if (currentLine.length > 0) lines.push(currentLine);

        lines.forEach((lineSpans, lineIndex) => {
            const isOdd = lineIndex % 2 !== 0; 
            const lineLength = lineSpans.length;

            lineSpans.forEach((span, wordIndex) => {
                let progress = lineLength > 1 ? wordIndex / (lineLength - 1) : 0.5;
                if (isOdd) progress = 1 - progress; 

                let rgb;
                if (progress < 0.45) rgb = interpolateColor(theme.c1, theme.mid, progress / 0.45);
                else if (progress > 0.55) rgb = interpolateColor(theme.mid, theme.c2, (progress - 0.55) / 0.45);
                else rgb = theme.mid;

                const colorStr = `rgb(${rgb[0]}, ${rgb[1]}, ${rgb[2]})`;
                span.style.color = colorStr;
                
                // 保留 X/Twitter 话题和链接的原生下划线体验
                if (span.closest('a')) {
                    span.style.textDecoration = 'underline';
                    span.style.textDecorationColor = colorStr;
                }
            });
        });
    }

    // ==========================================
    // 6. 智能防抖扫描系统
    // ==========================================
    let updateTimeout = null;

    function triggerUpdate() {
        if (!isEnabled) return;
        
        // 缩短防抖时间到 600ms，让 X 在无限往下滚动刷推文时颜色能更快跟上
        clearTimeout(updateTimeout);
        updateTimeout = setTimeout(() => {
            wrapTextNodesSafely();
            applyGlobalColors();
        }, 600);
    }

    const observer = new MutationObserver((mutations) => {
        let hasValidMutation = false;
        for (let m of mutations) {
            if (m.target.nodeType === 1 && m.target.classList.contains('beeline-word')) continue;
            hasValidMutation = true;
            break;
        }
        if (hasValidMutation) triggerUpdate();
    });

    observer.observe(document.body, { childList: true, characterData: true, subtree: true });

    setTimeout(triggerUpdate, 500);

    // ==========================================
    // 7. 窗口重绘与快捷键
    // ==========================================
    let resizeTimer;
    window.addEventListener('resize', () => {
        if (!isEnabled) return;
        clearTimeout(resizeTimer);
        resizeTimer = setTimeout(applyGlobalColors, 300);
    });

    document.addEventListener('keydown', function(e) {
        if ((e.ctrlKey || e.metaKey) && e.shiftKey && (e.key === 'b' || e.key === 'B')) {
            e.preventDefault();
            isEnabled = !isEnabled;
            
            if (!isEnabled) {
                document.querySelectorAll('.beeline-word').forEach(span => {
                    span.style.color = ''; 
                    if (span.closest('a')) span.style.textDecoration = '';
                });
            } else {
                triggerUpdate(); 
            }
        }
    });

})();