ttrpg-tools/src/components/md-commander/hooks/dice-engine/roller.ts

import type { DicePool, DicePoolResult, DieResult, RollResult } from "./types";
import { tokenize, parse } from "./parser";

/**
 * 掷骰子
 */
export function rollDie(sides: number): number {
  if (sides === 0) return 0; // 固定数字
  return Math.floor(Math.random() * sides) + 1;
}

/**
 * 掷骰池
 */
export function rollDicePool(pool: DicePool): DicePoolResult {
  // 分离骰子和固定数字
  const diceToRoll = pool.dice.filter((die) => die.sides > 0);
  const fixedNumbers = pool.dice.filter((die) => die.sides === 0);

  // 只掷真正的骰子
  const rolls: DieResult[] = diceToRoll.map((die) => ({
    sides: die.sides,
    value: rollDie(die.sides),
    isNegative: die.isNegative,
  }));

  // 添加固定数字
  const allRolls: DieResult[] = [
    ...rolls,
    ...fixedNumbers.map((die) => ({
      sides: 0,
      value: die.value,
      isNegative: die.isNegative,
    })),
  ];

  // 应用修饰符（只对有面数的骰子生效）
  const { keptRolls, droppedRolls } = applyModifier(rolls, pool.modifier);

  // 固定数字总是保留
  const finalKeptRolls = [
    ...keptRolls,
    ...allRolls.filter((r) => r.sides === 0),
  ];

  // 计算小计
  const subtotal = finalKeptRolls.reduce((sum, roll) => {
    return sum + (roll.isNegative ? -roll.value : roll.value);
  }, 0);

  return {
    pool,
    rolls: allRolls,
    keptRolls: finalKeptRolls,
    droppedRolls,
    subtotal,
  };
}

/**
 * 应用修饰符
 */
export function applyModifier(
  rolls: DieResult[],
  modifier: DicePool["modifier"],
): { keptRolls: DieResult[]; droppedRolls: DieResult[] } {
  if (!modifier) {
    return { keptRolls: rolls, droppedRolls: [] };
  }

  // 按值排序
  const sorted = [...rolls].sort((a, b) => a.value - b.value);

  switch (modifier.type) {
    case "kh": // Keep Highest - 保留最大的 N 个
    case "dh": {
      // Drop Highest - 丢弃最大的 N 个
      const count = modifier.count;
      const higher = sorted.slice(-count);
      const rest = sorted.slice(0, -count);
      if (modifier.type === "kh") {
        return { keptRolls: higher, droppedRolls: rest };
      } else {
        return { keptRolls: rest, droppedRolls: higher };
      }
    }
    case "kl": // Keep Lowest - 保留最小的 N 个
    case "dl": {
      // Drop Lowest - 丢弃最小的 N 个
      const count = modifier.count;
      const lower = sorted.slice(0, count);
      const rest = sorted.slice(count);
      if (modifier.type === "kl") {
        return { keptRolls: lower, droppedRolls: rest };
      } else {
        return { keptRolls: rest, droppedRolls: lower };
      }
    }
  }
}

/**
 * 执行完整的掷骰
 */
export function roll(formula: string): RollResult {
  const tokens = tokenize(formula);
  const pools = parse(tokens);

  const poolResults = pools.map((pool) => rollDicePool(pool));

  const total = poolResults.reduce((sum, result) => sum + result.subtotal, 0);

  // Generate detail expressions (both HTML and plain text)
  const htmlSpans: string[] = [];
  const textSpans: string[] = [];
  for (const result of poolResults) {
    for (const roll of result.rolls) {
      const isKept = result.keptRolls.some((kept) => kept === roll);
      if (roll.sides === 0) {
        const sign = roll.isNegative ? "-" : "";
        htmlSpans.push(`<strong>${sign}${roll.value}</strong>`);
        textSpans.push(`${sign}${roll.value}`);
      } else if (isKept) {
        htmlSpans.push(`<strong>[${roll.value}]</strong>`);
        textSpans.push(`[${roll.value}]`);
      } else {
        htmlSpans.push(`<span class="text-gray-400">[${roll.value}]</span>`);
        textSpans.push(`[${roll.value}]`);
      }
    }
  }

  const rollHtml = htmlSpans.join(" + ");
  const rollText = textSpans.join(" + ");
  const detail = `<strong>${total}</strong> = ${rollHtml}`;
  const plainDetail = `${total} = ${rollText}`;

  return {
    pools: poolResults,
    total,
    detail,
    plainDetail,
  };
}