import type { Token, DicePool } from "./types";

/**
 * 词法分析器 - 将输入字符串转换为令牌流
 */
export function tokenize(input: string): Token[] {
  const tokens: Token[] = [];
  let i = 0;
  const str = input.replace(/\s+/g, ""); // 移除所有空格

  while (i < str.length) {
    const char = str[i];

    // 修饰符 kh/kl/dh/dl - 必须在检查 'd' 骰子之前检查
    if (char === "k" || char === "d") {
      const rest = str.slice(i).toLowerCase();
      if (rest.startsWith("kh")) {
        i += 2;
        let countStr = "";
        while (i < str.length && /\d/.test(str[i])) {
          countStr += str[i];
          i++;
        }
        tokens.push({ type: "modifier", modType: "kh", count: parseInt(countStr) || 1 });
        continue;
      } else if (rest.startsWith("kl")) {
        i += 2;
        let countStr = "";
        while (i < str.length && /\d/.test(str[i])) {
          countStr += str[i];
          i++;
        }
        tokens.push({ type: "modifier", modType: "kl", count: parseInt(countStr) || 1 });
        continue;
      } else if (rest.startsWith("dh")) {
        i += 2;
        let countStr = "";
        while (i < str.length && /\d/.test(str[i])) {
          countStr += str[i];
          i++;
        }
        tokens.push({ type: "modifier", modType: "dh", count: parseInt(countStr) || 1 });
        continue;
      } else if (rest.startsWith("dl")) {
        i += 2;
        let countStr = "";
        while (i < str.length && /\d/.test(str[i])) {
          countStr += str[i];
          i++;
        }
        tokens.push({ type: "modifier", modType: "dl", count: parseInt(countStr) || 1 });
        continue;
      }
    }

    // 数字字面量
    if (/\d/.test(char)) {
      let numStr = "";
      while (i < str.length && /\d/.test(str[i])) {
        numStr += str[i];
        i++;
      }
      const num = parseInt(numStr);

      // 检查是否是 NdX 格式
      if (str[i] === "d" || str[i] === "D") {
        i++; // 跳过 'd'
        let sidesStr = "";
        while (i < str.length && /\d/.test(str[i])) {
          sidesStr += str[i];
          i++;
        }
        const sides = parseInt(sidesStr);
        tokens.push({ type: "dice", count: num, sides });
      } else {
        tokens.push({ type: "number", value: num });
      }
      continue;
    }

    // 单独的 dX 格式（等同于 1dX）
    if (char === "d" || char === "D") {
      i++;
      let sidesStr = "";
      while (i < str.length && /\d/.test(str[i])) {
        sidesStr += str[i];
        i++;
      }
      if (sidesStr.length > 0) {
        const sides = parseInt(sidesStr);
        tokens.push({ type: "dice", count: 1, sides });
      }
      continue;
    }

    // 骰池开始
    if (char === "{") {
      tokens.push({ type: "pool_start" });
      i++;
      continue;
    }

    // 骰池结束
    if (char === "}") {
      tokens.push({ type: "pool_end" });
      i++;
      continue;
    }

    // 逗号
    if (char === ",") {
      tokens.push({ type: "comma" });
      i++;
      continue;
    }

    // 加号
    if (char === "+") {
      tokens.push({ type: "plus" });
      i++;
      continue;
    }

    // 减号
    if (char === "-") {
      tokens.push({ type: "minus" });
      i++;
      continue;
    }

    // 未知字符，跳过
    i++;
  }

  return tokens;
}

/**
 * 语法分析器 - 将令牌流转换为骰池列表
 */
export function parse(tokens: Token[]): DicePool[] {
  const pools: DicePool[] = [];
  let i = 0;
  let currentSign = 1; // 当前符号，1 为正，-1 为负

  while (i < tokens.length) {
    const token = tokens[i];

    // 处理运算符
    if (token.type === "plus") {
      currentSign = 1;
      i++;
      continue;
    }

    if (token.type === "minus") {
      currentSign = -1;
      i++;
      continue;
    }

    // 解析骰池
    const pool = parsePool(tokens, i, currentSign);
    if (pool) {
      pools.push(pool.pool);
      i = pool.nextIndex;
      currentSign = 1; // 重置符号
    } else {
      i++;
    }
  }

  return pools;
}

/**
 * 解析单个骰池
 */
function parsePool(
  tokens: Token[],
  startIndex: number,
  sign: number
): { pool: DicePool; nextIndex: number } | null {
  const dice: DicePool["dice"] = [];
  let i = startIndex;
  let modifier: DicePool["modifier"] = undefined;

  const token = tokens[i];
  if (!token) return null;

  // 骰池字面量 {d4, d6, ...}
  if (token.type === "pool_start") {
    i++; // 跳过 {
    while (i < tokens.length && tokens[i].type !== "pool_end") {
      if (tokens[i].type === "comma") {
        i++;
        continue;
      }

      const token = tokens[i];
      if (token.type === "dice") {
        for (let j = 0; j < token.count; j++) {
          dice.push({
            sides: token.sides,
            value: 0,
            isNegative: sign < 0,
          });
        }
        i++;
      } else if (token.type === "number") {
        // 数字作为 0 面骰子（固定值）
        dice.push({
          sides: 0,
          value: token.value,
          isNegative: sign < 0,
        });
        i++;
      } else {
        i++;
      }
    }
    i++; // 跳过 }
  }
  // 单个骰子或数字
  else if (token.type === "dice") {
    for (let j = 0; j < token.count; j++) {
      dice.push({
        sides: token.sides,
        value: 0,
        isNegative: sign < 0,
      });
    }
    i++;
  } else if (token.type === "number") {
    dice.push({
      sides: 0,
      value: token.value,
      isNegative: sign < 0,
    });
    i++;
  } else {
    return null;
  }

  // 检查修饰符
  if (i < tokens.length && tokens[i].type === "modifier") {
    const mod = tokens[i] as Extract<Token, { type: "modifier" }>;
    modifier = { type: mod.modType, count: mod.count };
    i++;
  }

  return {
    pool: { dice, modifier, isNegative: sign < 0 },
    nextIndex: i,
  };
}