import { ref, computed, reactive } from 'vue';

/**
 * 生成随机字符串
 * @param length 字符串长度
 * @returns 随机字符串
 */
function generateRandomString(length: number): string {
  // 使用更简单的字符集，避免混淆字符
  const characters = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ';
  let result = '';
  for (let i = 0; i < length; i++) {
    result += characters.charAt(Math.floor(Math.random() * characters.length));
  }
  return result;
}

/**
 * 为验证码文本生成SVG
 * @param text 验证码文本
 * @returns SVG 字符串
 */
function generateCaptchaSvg(text: string): string {
  const width = 150;
  const height = 50;
  const fontSize = 30;
  const letters = text.split('');

  // 文字元素（确保可读性）
  const textElements = letters.map((char, index) => {
    const x = (width / text.length) * (index + 0.5);
    const y = height / 2 + fontSize / 3; 
    const fill = `hsl(${Math.random() * 360}, 70%, 80%)`; // 提高亮度，增加可读性

    return `<text
      x="${x}"
      y="${y}"
      font-size="${fontSize}"
      font-family="Arial, sans-serif"
      font-weight="bold"
      text-anchor="middle"
      fill="${fill}"
      style="letter-spacing: 1px;"
    >${char}</text>`;
  }).join('');

  // 生成干扰线
  let lines = '';
  
  // 添加2-4条随机曲线
  for (let i = 0; i < 3; i++) {
    const startX = Math.random() * width * 0.2;
    const startY = Math.random() * height;
    const endX = width - Math.random() * width * 0.2;
    const endY = Math.random() * height;
    const control1X = width * 0.3 + Math.random() * width * 0.2;
    const control1Y = Math.random() * height;
    const control2X = width * 0.5 + Math.random() * width * 0.2;
    const control2Y = Math.random() * height;

    // 使用贝塞尔曲线创建更自然的干扰线
    lines += `<path 
      d="M ${startX} ${startY} C ${control1X} ${control1Y}, ${control2X} ${control2Y}, ${endX} ${endY}" 
      stroke="rgba(255, 255, 255, ${0.2 + Math.random() * 0.3})" 
      stroke-width="${1 + Math.random()}" 
      fill="none"
    />`;
  }
  
  // 添加5-10个随机点
  for (let i = 0; i < 8; i++) {
    const x = Math.random() * width;
    const y = Math.random() * height;
    const radius = 1 + Math.random() * 2;
    
    lines += `<circle
      cx="${x}"
      cy="${y}"
      r="${radius}"
      fill="rgba(255, 255, 255, ${0.4 + Math.random() * 0.4})"
    />`;
  }

  return `
    <svg
      xmlns="http://www.w3.org/2000/svg"
      width="${width}"
      height="${height}"
      viewBox="0 0 ${width} ${height}"
      style="background-color: rgba(55, 65, 81, 0.5); border-radius: 6px; border: 1px solid rgba(107, 114, 128, 0.5);"
    >
      ${lines}
      ${textElements}
    </svg>
  `;
}

/**
 * 验证码组件
 * @param length 验证码长度
 * @returns 验证码相关状态和方法
 */
export function useCaptcha(length: number = 4) {
  // 使用状态对象存储所有相关状态
  const state = reactive({
    captchaText: '',      // 验证码文本
    userInput: '',        // 用户输入
    svgHtml: '',          // 验证码SVG
    error: '',            // 错误信息
  });

  /**
   * 生成新的验证码
   */
  const generateCaptcha = () => {
    // 生成新的验证码文本
    const newText = generateRandomString(length);
    
    // 更新状态
    state.captchaText = newText;
    state.userInput = ''; // 清空用户输入
    state.error = ''; // 清除错误
    
    // 生成验证码SVG
    state.svgHtml = generateCaptchaSvg(newText);
  };

  /**
   * 验证用户输入
   * @returns 是否验证通过
   */
  const validateCaptcha = (): boolean => {
    // 确保userInput和captchaText都被处理为大写字符串进行比较
    const normalizedInput = (state.userInput || '').toUpperCase().trim();
    const normalizedCaptcha = (state.captchaText || '').toUpperCase().trim();
    
    if (!normalizedInput) {
      state.error = '请输入验证码';
      return false;
    }
    
    // 验证用户输入是否与验证码匹配
    const isValid = normalizedInput === normalizedCaptcha;
    
    if (!isValid) {
      state.error = '验证码错误';
      generateCaptcha(); // 错误后自动刷新
      return false;
    }
    
    state.error = '';
    return true;
  };
  
  /**
   * 获取当前验证码文本
   */
  const getCurrentCaptcha = () => {
    return state.captchaText;
  };

  // 初始化生成第一个验证码
  generateCaptcha();

  return {
    state,
    userInput: computed({
      get: () => state.userInput,
      set: (value) => { state.userInput = value; }
    }),
    captchaSvg: computed(() => state.svgHtml),
    error: computed(() => state.error),
    generateCaptcha,
    validateCaptcha,
    getCurrentCaptcha,
  };
}