import { taipeiParts } from "../schedule/time-utils.js";

export interface ParsedReminderRequest {
  content: string; // 去除時間片語與「提醒我」之後的委託內容
  triggerAt: Date;
}

// J-1 自然語句解析：中文數字／阿拉伯數字時刻皆可辨識。
const CHINESE_HOUR_WORDS: [string, number][] = [
  ["十二", 12],
  ["十一", 11],
  ["十", 10],
  ["九", 9],
  ["八", 8],
  ["七", 7],
  ["六", 6],
  ["五", 5],
  ["四", 4],
  ["三", 3],
  ["兩", 2],
  ["二", 2],
  ["一", 1],
];

function parseHour(segment: string): number | null {
  const arabic = segment.match(/(\d{1,2})\s*[點点:時]/);
  if (arabic) {
    return Number(arabic[1]);
  }
  for (const [word, value] of CHINESE_HOUR_WORDS) {
    if (segment.includes(`${word}點`) || segment.includes(`${word}点`)) {
      return value;
    }
  }
  return null;
}

function parseMinute(segment: string): number {
  if (segment.includes("半")) {
    return 30;
  }
  const explicit = segment.match(/[點点](\d{1,2})分/);
  if (explicit) {
    return Number(explicit[1]);
  }
  const colon = segment.match(/:(\d{1,2})/);
  if (colon) {
    return Number(colon[1]);
  }
  return 0;
}

// 依 24 小時制／上下午標記／模糊小時（1~12，取最接近的未來時刻）解析出候選小時（依時間先後排序）。
function resolveHourCandidates(segment: string, hour: number): number[] {
  const isPM = /下午|晚上|傍晚|中午(?!.*上午)/.test(segment) && hour !== 12;
  const isAM = /早上|上午|凌晨/.test(segment);
  if (isPM) {
    return [hour === 12 ? 12 : hour + 12];
  }
  if (isAM) {
    return [hour === 12 ? 0 : hour];
  }
  if (hour >= 13 || hour === 0) {
    return [hour];
  }
  if (hour === 12) {
    return [12, 0];
  }
  return [hour, hour + 12];
}

function buildTaipeiDateTime(now: Date, hour: number, minute: number): Date {
  const { year, month, day } = taipeiParts(now);
  // Asia/Taipei 為 UTC+8：當地 HH:MM 對應 UTC (HH-8):MM（JS Date.UTC 會自動處理跨日進位/退位）。
  return new Date(Date.UTC(year, month - 1, day, hour - 8, minute, 0, 0));
}

function nearestFutureOccurrence(now: Date, candidateHours: number[], minute: number): Date {
  for (const hour of candidateHours) {
    const candidate = buildTaipeiDateTime(now, hour, minute);
    if (candidate.getTime() > now.getTime()) {
      return candidate;
    }
  }
  const fallback = buildTaipeiDateTime(now, candidateHours[0], minute);
  return new Date(fallback.getTime() + 24 * 60 * 60 * 1000);
}

// 解析「單次提醒」型委託，例如「三點提醒我開會」「晚上八點半提醒我倒垃圾」。
// 無法辨識時間片語時回傳 null（呼叫端可視為一般對話，不建立任務）。
export function parseReminderRequest(text: string, now: Date = new Date()): ParsedReminderRequest | null {
  const match = text.match(/^(.*?)提醒我(.+)$/);
  if (!match) {
    return null;
  }
  const [, timeSegment, rawContent] = match;

  const hour = parseHour(timeSegment);
  if (hour === null) {
    return null;
  }
  const minute = parseMinute(timeSegment);
  const candidates = resolveHourCandidates(timeSegment, hour);
  const triggerAt = nearestFutureOccurrence(now, candidates, minute);

  const content = rawContent.trim().replace(/^[，,、]/, "").trim();
  if (!content) {
    return null;
  }

  return { content, triggerAt };
}