// ==UserScript==
// @name         ChromaFlow
// @namespace    http://tampermonkey.net/
// @version      6.0
// @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(el) {
        let bg = 'rgba(0, 0, 0, 0)';
        while (el && el.nodeType === 1) {
            bg = window.getComputedStyle(el).backgroundColor;
            if (bg !== 'rgba(0, 0, 0, 0)' && bg !== 'transparent' && bg !== '') return bg;
            el = el.parentNode;
        }
        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) {
        // 匹配单个汉字，或连续英文字母/数字，或标点/空格
        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. 核心目标：白名单与黑名单
    // ==========================================
    // 白名单：只有这些容器里的文字才配被当做“文章”阅读
    // 包含标准 HTML 标签，以及 AI Studio/ChatGPT/Claude 常见的富文本容器
    const TARGET_SELECTORS = 'p, li, blockquote, dd, dt, ms-cmark-node, .text-base, .markdown, .markdown-body, .prose';

    // 黑名单：在白名单里，如果遇到这些元素，立刻跳过（防破坏代码块）
    const IGNORE_SELECTORS = 'code, pre, kbd, button, input, textarea, select, [contenteditable="true"], .inline-code';

    // ==========================================
    // 4. 文本切割与染色引擎
    // ==========================================
    function processBlock(block) {
        if (!isEnabled || block.dataset.beelineProcessed === "true") return;
        if (block.closest(IGNORE_SELECTORS)) return; // 再次确认不在代码块内

        // --- 步骤 A: 将纯文本替换为包裹 span 的单词/汉字 ---
        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_SKIP;
                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 text = node.nodeValue;
            const parent = node.parentNode;
            const fragment = document.createDocumentFragment();
            const tokens = tokenizeText(text);

            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);
                }
            });
            parent.replaceChild(fragment, node);
        });

        block.dataset.beelineProcessed = "true";
        colorizeBlock(block); // 切割完毕立刻上色
    }

    function colorizeBlock(block) {
        if (!document.body.contains(block) || !isEnabled) return;

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

        const spans = Array.from(block.querySelectorAll('.beeline-word'));
        if (spans.length === 0) return;

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

        // --- 步骤 B: 物理测算 Y 轴换行 (带容差) ---
        spans.forEach(span => {
            const rect = span.getBoundingClientRect();
            if (rect.width === 0 && rect.height === 0) return;

            // 将 Y 坐标归一化到 5px 的网格中，防止同一行中英文高度差异被误判为换行
            const y = Math.round(rect.top / 5) * 5;

            if (lastY === -1 || Math.abs(y - lastY) > 5) {
                if (currentLine.length > 0) lines.push(currentLine);
                currentLine = [span];
                lastY = y;
            } else {
                currentLine.push(span);
            }
        });
        if (currentLine.length > 0) lines.push(currentLine);

        // --- 步骤 C: 渲染渐变色 ---
        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;

                if (span.closest('a')) {
                    span.style.textDecoration = 'underline';
                    span.style.textDecorationColor = colorStr;
                }
            });
        });
    }

    // ==========================================
    // 5. 扫描调度系统 (低耗能心跳)
    // ==========================================
    function scanAndProcess() {
        if (!isEnabled) return;
        // 只寻找白名单内的容器
        const blocks = document.querySelectorAll(TARGET_SELECTORS);
        blocks.forEach(block => {
            // 如果还未处理，则执行切割+上色
            if (block.dataset.beelineProcessed !== "true") {
                processBlock(block);
            }
        });
    }

    let needsUpdate = true;
    const observer = new MutationObserver(() => needsUpdate = true);
    observer.observe(document.body, { childList: true, characterData: true, subtree: true });

    setInterval(() => {
        if (needsUpdate && isEnabled) {
            scanAndProcess();
            needsUpdate = false;
        }
    }, 400);

    // ==========================================
    // 6. 窗口重绘与快捷键
    // ==========================================
    let resizeTimer;
    window.addEventListener('resize', () => {
        if (!isEnabled) return;
        clearTimeout(resizeTimer);
        resizeTimer = setTimeout(() => {
            // 窗口改变时，只重新测算坐标和上色，不需要重新切割 DOM，性能极高
            document.querySelectorAll(TARGET_SELECTORS).forEach(block => {
                if (block.dataset.beelineProcessed === "true") colorizeBlock(block);
            });
        }, 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 {
                needsUpdate = true;
            }
        }
    });

})();