import { parseTimeScope } from '../temporal-recall-service/time-parser.mjs';

export const RAIN_DEFAULT_DAYS = 3;

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

/** @param {Date} anchor @param {number} deltaDays */
function addDays(anchor, deltaDays) {
  const shifted = new Date(anchor.getTime() + TZ_OFFSET_MIN * 60_000);
  const ms =
    Date.UTC(
      shifted.getUTCFullYear(),
      shifted.getUTCMonth(),
      shifted.getUTCDate() + deltaDays,
      0,
      0,
      0,
      0,
    ) - TZ_OFFSET_MIN * 60_000;
  return new Date(ms);
}

/** @param {Date} anchor */
function endOfDay(anchor) {
  const p = new Date(anchor.getTime() + TZ_OFFSET_MIN * 60_000);
  const ms =
    Date.UTC(p.getUTCFullYear(), p.getUTCMonth(), p.getUTCDate() + 1, 0, 0, 0, 0) -
    TZ_OFFSET_MIN * 60_000;
  return new Date(ms);
}

const AMBIGUOUS_TIME_PATTERNS = [
  /前几天/u,
  /那段(?:时间|日子)/u,
  /上次(?:那)?(?:段|个)/u,
  /大概.{0,6}(?:昨天|前天|上周|几)/u,
  /左右/u,
  /不太确定.{0,8}时间/u,
];

const EXPLICIT_TIME_HINT =
  /昨天|昨日|今天|今日|明天|明日|前天|后天|上周|这周|本周|这个月|本月|上个月|\d{1,2}\s*月|\d{1,2}\s*[：:]\d{2}|最近\s*\d+\s*天|最近一周|最近1周|\d{4}-\d{2}-\d{2}/u;

/**
 * @param {string} query
 * @param {Date} [now]
 */
export function resolveRainTimeRange(query, now = new Date()) {
  const text = String(query ?? '').trim();

  for (const pattern of AMBIGUOUS_TIME_PATTERNS) {
    if (pattern.test(text)) {
      return {
        needsClarification: true,
        clarificationQuestion:
          '请说明要分析 MeInput 输入记录的起止时间（例如「9月2日 18:00 到 9月4日 10:00」，或「昨天全天」）。若你不补充，我将默认使用近 3 天。',
        range: null,
        source: 'ambiguous',
        label: null,
      };
    }
  }

  if (!EXPLICIT_TIME_HINT.test(text)) {
    const end = endOfDay(now);
    const start = addDays(now, -RAIN_DEFAULT_DAYS);
    return {
      needsClarification: false,
      range: { start: start.toISOString(), end: end.toISOString() },
      source: 'default_3d',
      label: `近${RAIN_DEFAULT_DAYS}天`,
    };
  }

  const scope = parseTimeScope(text, now);
  const isDefaultFallback =
    scope.rule_hits?.includes('time:default_week') ||
    scope.rule_hits?.includes('time:recent_fuzzy');

  if (isDefaultFallback && /最近|近期|这几天/u.test(text) && !/最近\s*\d+\s*天/u.test(text)) {
    const end = endOfDay(now);
    const start = addDays(now, -RAIN_DEFAULT_DAYS);
    return {
      needsClarification: false,
      range: { start: start.toISOString(), end: end.toISOString() },
      source: 'default_3d',
      label: `近${RAIN_DEFAULT_DAYS}天`,
    };
  }

  return {
    needsClarification: false,
    range: scope.mention_range,
    source: 'user_explicit',
    label: scope.relative_label,
  };
}

export function formatRainTimeRangeLabel(range, meta = {}) {
  if (!range?.start || !range?.end) return meta.label ?? '未指定';
  const start = range.start.slice(0, 16).replace('T', ' ');
  const end = range.end.slice(0, 16).replace('T', ' ');
  const suffix = meta.source === 'default_3d' ? '（默认近3天）' : '';
  return `${start} ~ ${end}${suffix}`;
}