const TZ_OFFSET_MIN = Number(process.env.TEMPORAL_RECALL_TZ_OFFSET_MIN ?? 480);

/** @param {Date} d */
function toLocalParts(d) {
  const shifted = new Date(d.getTime() + TZ_OFFSET_MIN * 60_000);
  return {
    year: shifted.getUTCFullYear(),
    month: shifted.getUTCMonth(),
    day: shifted.getUTCDate(),
  };
}

/** @param {{ year: number, month: number, day: number }} p @param {number} h @param {number} m */
function partsToDate(p, h = 0, m = 0) {
  const utcMs =
    Date.UTC(p.year, p.month, p.day, h, m, 0, 0) - TZ_OFFSET_MIN * 60_000;
  return new Date(utcMs);
}

/** @param {Date} anchor @param {number} deltaDays */
function addDays(anchor, deltaDays) {
  const p = toLocalParts(anchor);
  return partsToDate({ year: p.year, month: p.month, day: p.day + deltaDays }, 0, 0);
}

const WEEKDAY_MAP = {
  一: 1,
  二: 2,
  三: 3,
  四: 4,
  五: 5,
  六: 6,
  日: 7,
  天: 7,
};

function parseHour(text, hourRaw, minuteRaw) {
  let hour = Number(hourRaw);
  let minute = minuteRaw != null && minuteRaw !== '' ? Number(minuteRaw) : 0;
  if (Number.isNaN(hour)) return null;
  if (Number.isNaN(minute)) minute = 0;

  if (/下午|晚上|傍晚/.test(text) && hour >= 1 && hour <= 11) hour += 12;
  if (/中午/.test(text) && hour >= 1 && hour <= 10) hour += 12;
  if (/凌晨/.test(text) && hour === 12) hour = 0;
  if (hour === 24) hour = 0;
  if (hour < 0 || hour > 23 || minute < 0 || minute > 59) return null;
  return { hour, minute };
}

function resolveDayOffset(text) {
  if (/大后天/.test(text)) return 3;
  if (/后天/.test(text)) return 2;
  if (/明天|明日/.test(text)) return 1;
  if (/今天|今日/.test(text)) return 0;
  if (/昨天|昨日/.test(text)) return -1;
  if (/前天/.test(text)) return -2;
  return null;
}

function resolveWeekday(text, anchor) {
  const m = text.match(/(下?周|这个星期|这星期|本周)?([一二三四五六日天])/);
  if (!m) return null;
  const target = WEEKDAY_MAP[m[2]];
  if (!target) return null;
  const p = toLocalParts(anchor);
  const anchorDate = partsToDate(p, 0, 0);
  const anchorDow = new Date(anchorDate.getTime() + TZ_OFFSET_MIN * 60_000).getUTCDay();
  const anchorMonBased = anchorDow === 0 ? 7 : anchorDow;
  let delta = target - anchorMonBased;
  if (delta <= 0) delta += 7;
  if (/下周/.test(m[1] ?? '')) delta += 7;
  return addDays(anchor, delta);
}

function resolveMonthDay(text, anchor) {
  const m = text.match(/(\d{1,2})\s*月\s*(\d{1,2})\s*日/);
  if (!m) return null;
  const month = Number(m[1]) - 1;
  const day = Number(m[2]);
  const p = toLocalParts(anchor);
  let year = p.year;
  if (month < p.month || (month === p.month && day < p.day)) year += 1;
  return partsToDate({ year, month, day }, 0, 0);
}

const CN_DIGIT = {
  零: 0,
  〇: 0,
  一: 1,
  二: 2,
  两: 2,
  三: 3,
  四: 4,
  五: 5,
  六: 6,
  七: 7,
  八: 8,
  九: 9,
  十: 10,
};

function parseChineseNumber(raw) {
  const s = String(raw ?? '').trim();
  if (!s) return null;
  if (/^\d+$/.test(s)) return Number(s);
  if (s === '十') return 10;
  if (s.startsWith('十')) {
    const tail = CN_DIGIT[s[1]];
    return tail != null ? 10 + tail : null;
  }
  if (s.endsWith('十')) {
    const head = CN_DIGIT[s[0]];
    return head != null ? head * 10 : null;
  }
  if (s.includes('十')) {
    const [a, b] = s.split('十');
    const head = a ? CN_DIGIT[a] ?? null : 1;
    const tail = b ? CN_DIGIT[b] ?? null : 0;
    if (head == null || tail == null) return null;
    return head * 10 + tail;
  }
  return CN_DIGIT[s] ?? null;
}

function findTimeInText(text) {
  const cnPattern =
    /(上午|早上|中午|下午|晚上|傍晚|凌晨)?\s*([零〇一二两三四五六七八九十]{1,3})\s*(?:点|时)\s*(?:([零〇一二两三四五六七八九十]{1,3})\s*分?)?/;
  const cnMatch = text.match(cnPattern);
  if (cnMatch) {
    const hour = parseChineseNumber(cnMatch[2]);
    const minute = cnMatch[3] ? parseChineseNumber(cnMatch[3]) : 0;
    if (hour != null) {
      const parsed = parseHour(text, hour, minute ?? 0);
      if (parsed) return parsed;
    }
  }

  const patterns = [
    /(上午|早上|中午|下午|晚上|傍晚|凌晨)?\s*(\d{1,2})\s*(?:[:：点时])\s*(\d{1,2})?\s*(?:分)?/,
    /(\d{1,2})\s*[:：]\s*(\d{2})/,
  ];
  for (const re of patterns) {
    const m = text.match(re);
    if (!m) continue;
    const parsed = parseHour(text, m[2] ?? m[1], m[3] ?? m[2]);
    if (parsed) return parsed;
  }
  return null;
}

function hasFutureIntent(text) {
  return /明天|明日|后天|大后天|下周|周一|周二|周三|周四|周五|周六|周日|星期|安排|预约|会议|截止|之前|前要/.test(
    text,
  );
}

/**
 * 从中文文本抽取计划/事件发生时间（相对 observed_time 锚点）。
 *
 * @param {string} text
 * @param {string | Date} observedAt
 * @returns {{ event_time: string | null, confidence: number, status: 'planned' | 'mentioned' | 'unknown' }}
 */
export function extractEventTime(text, observedAt) {
  const raw = String(text ?? '').trim();
  if (!raw) {
    return { event_time: null, confidence: 0, status: 'unknown' };
  }

  const anchor = observedAt instanceof Date ? observedAt : new Date(observedAt);
  if (Number.isNaN(anchor.getTime())) {
    return { event_time: null, confidence: 0, status: 'unknown' };
  }

  let baseDay = null;
  let dayConfidence = 0;

  const dayOffset = resolveDayOffset(raw);
  if (dayOffset != null) {
    baseDay = addDays(anchor, dayOffset);
    dayConfidence = 0.88;
  }

  if (!baseDay) {
    baseDay = resolveWeekday(raw, anchor);
    if (baseDay) dayConfidence = 0.75;
  }

  if (!baseDay) {
    baseDay = resolveMonthDay(raw, anchor);
    if (baseDay) dayConfidence = 0.8;
  }

  const timePart = findTimeInText(raw);
  if (baseDay && timePart) {
    const p = toLocalParts(baseDay);
    const dt = partsToDate(p, timePart.hour, timePart.minute);
    return {
      event_time: dt.toISOString(),
      confidence: Math.min(0.95, dayConfidence + 0.1),
      status: 'planned',
    };
  }

  if (baseDay) {
    const p = toLocalParts(baseDay);
    return {
      event_time: partsToDate(p, 9, 0).toISOString(),
      confidence: dayConfidence * 0.85,
      status: 'planned',
    };
  }

  if (timePart && /今天|今日/.test(raw)) {
    const p = toLocalParts(anchor);
    return {
      event_time: partsToDate(p, timePart.hour, timePart.minute).toISOString(),
      confidence: 0.82,
      status: 'planned',
    };
  }

  if (hasFutureIntent(raw)) {
    return { event_time: null, confidence: 0.35, status: 'mentioned' };
  }

  return { event_time: null, confidence: 0, status: 'unknown' };
}

/**
 * 判断 timeline item 是否与查询时间窗相关（observed 或 event 命中）。
 */
export function itemMatchesTimeWindow(item, time, temporalMode) {
  const mentionStart = new Date(time?.mention_range?.start ?? 0).getTime();
  const mentionEnd = new Date(time?.mention_range?.end ?? 0).getTime();
  const eventStart = time?.event_range?.start
    ? new Date(time.event_range.start).getTime()
    : mentionStart;
  const eventEnd = time?.event_range?.end
    ? new Date(time.event_range.end).getTime()
    : mentionEnd;
  const observed = new Date(item.observed_time).getTime();
  const event = item.event_time ? new Date(item.event_time).getTime() : null;

  const inMention = observed >= mentionStart && observed < mentionEnd;
  const inEvent = event != null && event >= eventStart && event < eventEnd;

  switch (temporalMode) {
    case 'OCCURRED_IN':
      return inEvent || (!event && inMention);
    case 'MENTIONED_IN':
    case 'CREATED_IN':
      return inMention;
    case 'PLANNED_IN':
    case 'DUE_IN':
      return inEvent || inMention;
    default:
      return inMention || inEvent;
  }
}

/**
 * 为 DB 检索扩展 observed 窗口（捕获「昨天说明天」类输入）。
 */
export function expandObservedFetchRange(time, temporalMode) {
  const start = new Date(time?.mention_range?.start ?? Date.now());
  const end = new Date(time?.mention_range?.end ?? Date.now());
  if (['PLANNED_IN', 'OCCURRED_IN', 'AMBIGUOUS', 'DUE_IN'].includes(temporalMode ?? '')) {
    start.setDate(start.getDate() - 14);
  }
  return { start: start.toISOString(), end: end.toISOString() };
}