import { jalaliToDate } from '@/lib/jalali';

export type ActivityThreadEntry = {
  at: Date | null;
  dateLabel: string;
  timeLabel: string;
  author: string;
  body: string;
};

const STAMP = /^\[(.+?) ساعت (\S+?)(?: — (.+))?\]$/;

/** یادداشت فعالیت را به نظرهای جدا با مهر تاریخ/ساعت/نویسنده تبدیل می‌کند. */
export function parseActivityThread(raw: string | null | undefined): ActivityThreadEntry[] | null {
  const text = (raw ?? '').replace(/\r\n/g, '\n').trim();
  if (!text) return null;

  const entries: ActivityThreadEntry[] = [];
  const preamble: string[] = [];
  let current: ActivityThreadEntry | null = null;
  let sawStamp = false;

  for (const line of text.split('\n')) {
    const match = line.trim().match(STAMP);
    if (match) {
      sawStamp = true;
      if (current) entries.push(trimEntry(current));
      current = {
        at: stampToDate(match[1] ?? '', match[2] ?? ''),
        dateLabel: (match[1] ?? '').trim(),
        timeLabel: (match[2] ?? '').trim(),
        author: (match[3] ?? '').trim(),
        body: '',
      };
      continue;
    }
    if (current) current.body += `${current.body ? '\n' : ''}${line}`;
    else preamble.push(line);
  }
  if (current) entries.push(trimEntry(current));
  if (!sawStamp) return null;

  const head = preamble.join('\n').trim();
  if (head) {
    entries.unshift({ at: null, dateLabel: '', timeLabel: '', author: '', body: head });
  }
  return entries;
}

function trimEntry(entry: ActivityThreadEntry): ActivityThreadEntry {
  return { ...entry, body: entry.body.trim() };
}

function latinDigits(value: string): string {
  const fa = '۰۱۲۳۴۵۶۷۸۹';
  const ar = '٠١٢٣٤٥٦٧٨٩';
  return value.replace(/[۰-۹٠-٩]/g, (ch) => {
    const faIndex = fa.indexOf(ch);
    return String(faIndex >= 0 ? faIndex : ar.indexOf(ch));
  });
}

function stampToDate(dateLabel: string, timeLabel: string): Date | null {
  const date = latinDigits(dateLabel).match(/(\d{4})\/(\d{1,2})\/(\d{1,2})/);
  if (!date) return null;
  const at = jalaliToDate(Number(date[1]), Number(date[2]), Number(date[3]));
  if (Number.isNaN(at.getTime())) return null;
  const time = latinDigits(timeLabel).match(/(\d{1,2}):(\d{2})/);
  if (time) at.setHours(Number(time[1]), Number(time[2]), 0, 0);
  return at;
}