const express = require('express');
const crypto = require('crypto');
const router = express.Router();

// 内存存储验证码（生产环境建议使用Redis）
const captchaStore = new Map();

/**
 * 生成随机验证码字符串
 * @param {number} length 验证码长度
 * @returns {string} 验证码字符串
 */
function generateCaptchaText(length = 4) {
  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
  let result = '';
  for (let i = 0; i < length; i++) {
    result += chars.charAt(Math.floor(Math.random() * chars.length));
  }
  return result;
}

/**
 * 生成SVG验证码图片
 * @param {string} text 验证码文本
 * @returns {string} SVG字符串
 */
function generateCaptchaSVG(text) {
  const width = 120;
  const height = 40;
  const fontSize = 18;
  
  // 生成随机颜色
  const getRandomColor = () => {
    const colors = ['#FF6B6B', '#4ECDC4', '#45B7D1', '#96CEB4', '#FFEAA7', '#DDA0DD', '#98D8C8'];
    return colors[Math.floor(Math.random() * colors.length)];
  };
  
  // 生成干扰线
  const generateNoise = () => {
    let noise = '';
    for (let i = 0; i < 3; i++) {
      const x1 = Math.random() * width;
      const y1 = Math.random() * height;
      const x2 = Math.random() * width;
      const y2 = Math.random() * height;
      noise += `<line x1="${x1}" y1="${y1}" x2="${x2}" y2="${y2}" stroke="${getRandomColor()}" stroke-width="1" opacity="0.3"/>`;
    }
    return noise;
  };
  
  // 生成干扰点
  const generateDots = () => {
    let dots = '';
    for (let i = 0; i < 20; i++) {
      const x = Math.random() * width;
      const y = Math.random() * height;
      const r = Math.random() * 2 + 1;
      dots += `<circle cx="${x}" cy="${y}" r="${r}" fill="${getRandomColor()}" opacity="0.4"/>`;
    }
    return dots;
  };
  
  // 生成文字
  let textElements = '';
  const charWidth = width / text.length;
  
  for (let i = 0; i < text.length; i++) {
    const char = text[i];
    const x = charWidth * i + charWidth / 2;
    const y = height / 2 + fontSize / 3;
    const rotation = (Math.random() - 0.5) * 30; // 随机旋转角度
    const color = getRandomColor();
    
    textElements += `
      <text x="${x}" y="${y}" 
            font-family="Arial, sans-serif" 
            font-size="${fontSize}" 
            font-weight="bold" 
            fill="${color}" 
            text-anchor="middle" 
            transform="rotate(${rotation} ${x} ${y})">
        ${char}
      </text>`;
  }
  
  const svg = `
    <svg width="${width}" height="${height}" xmlns="http://www.w3.org/2000/svg">
      <defs>
        <linearGradient id="bg" x1="0%" y1="0%" x2="100%" y2="100%">
          <stop offset="0%" style="stop-color:#f8f9fa;stop-opacity:1" />
          <stop offset="100%" style="stop-color:#e9ecef;stop-opacity:1" />
        </linearGradient>
      </defs>
      <rect width="${width}" height="${height}" fill="url(#bg)" stroke="#dee2e6" stroke-width="1"/>
      ${generateNoise()}
      ${generateDots()}
      ${textElements}
    </svg>`;
  
  return svg;
}

/**
 * 生成验证码接口
 */
router.get('/generate', (req, res) => {
  try {
    // 生成验证码文本
    const captchaText = generateCaptchaText();
    
    // 生成唯一ID
    const captchaId = crypto.randomUUID();
    
    // 存储验证码（5分钟过期）
    captchaStore.set(captchaId, {
      text: captchaText.toLowerCase(), // 存储小写用于比较
      expires: Date.now() + 5 * 60 * 1000 // 5分钟过期
    });
    
    // 生成SVG图片
    const svgImage = generateCaptchaSVG(captchaText);
    
    res.json({
      success: true,
      data: {
        captchaId,
        image: `data:image/svg+xml;base64,${Buffer.from(svgImage).toString('base64')}`
      }
    });
  } catch (error) {
    console.error('生成验证码失败:', error);
    res.status(500).json({
      success: false,
      message: '生成验证码失败'
    });
  }
});

/**
 * 验证验证码接口
 * @param {string} captchaId 验证码ID
 * @param {string} captchaText 用户输入的验证码
 */
router.post('/verify', (req, res) => {
  try {
    const { captchaId, captchaText } = req.body;
    
    if (!captchaId || !captchaText) {
      return res.status(400).json({
        success: false,
        message: '验证码ID和验证码不能为空'
      });
    }
    
    // 获取存储的验证码
    const storedCaptcha = captchaStore.get(captchaId);
    
    if (!storedCaptcha) {
      return res.status(400).json({
        success: false,
        message: '验证码不存在或已过期'
      });
    }
    
    // 检查是否过期
    if (Date.now() > storedCaptcha.expires) {
      captchaStore.delete(captchaId);
      return res.status(400).json({
        success: false,
        message: '验证码已过期'
      });
    }
    
    // 验证验证码（不区分大小写）
    const isValid = storedCaptcha.text === captchaText.toLowerCase();
    
    // 验证后删除验证码（无论成功失败）
    captchaStore.delete(captchaId);
    
    if (isValid) {
      res.json({
        success: true,
        message: '验证码验证成功'
      });
    } else {
      res.status(400).json({
        success: false,
        message: '验证码错误'
      });
    }
  } catch (error) {
    console.error('验证验证码失败:', error);
    res.status(500).json({
      success: false,
      message: '验证验证码失败'
    });
  }
});

// 清理过期验证码的定时任务
setInterval(() => {
  const now = Date.now();
  for (const [id, captcha] of captchaStore.entries()) {
    if (now > captcha.expires) {
      captchaStore.delete(id);
    }
  }
}, 60 * 1000); // 每分钟清理一次

// 导出验证函数供其他模块使用
module.exports = router;
module.exports.verifyCaptcha = (captchaId, captchaText) => {
  const captcha = captchaStore.get(captchaId);
  if (!captcha) {
    return false; // 验证码不存在或已过期
  }
  
  if (captcha.text.toLowerCase() !== captchaText.toLowerCase()) {
    return false; // 验证码错误
  }
  
  // 验证成功后删除验证码（一次性使用）
  captchaStore.delete(captchaId);
  return true;
};