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

export type ActivityThreadEntry = {
  at: Date | null;
  dateLabel: string;
  timeLabel: string;
  author: string;
  body: string;
  /** شناسهٔ فایل‌های چسبیده به این یادداشت (عکس/صوت/فایل) */
  attachmentIds?: string[];
};

const STAMP = /^\[(.+?) ساعت (\S+?)(?: — (.+))?\]$/;
const ATTACHMENTS = /^\[\[attachments:([^\]]+)\]\]$/i;
const COMMENT_MEDIA_WINDOW_MS = 3 * 60 * 1000;

/** 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 trimmed = line.trim();
    const stamp = trimmed.match(STAMP);
    if (stamp) {
      sawStamp = true;
      if (current) entries.push(trimEntry(current));
      current = {
        at: stampToDate(stamp[1] ?? '', stamp[2] ?? ''),
        dateLabel: (stamp[1] ?? '').trim(),
        timeLabel: (stamp[2] ?? '').trim(),
        author: (stamp[3] ?? '').trim(),
        body: '',
        attachmentIds: [],
      };
      continue;
    }
    const attach = trimmed.match(ATTACHMENTS);
    if (attach && current) {
      current.attachmentIds = attach[1]!
        .split(',')
        .map((id) => id.trim())
        .filter(Boolean);
      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,
      attachmentIds: [],
    });
  }
  return entries;
}

/** برگرداندن متن ذخیره‌شونده از نظرهای جدا. */
export function serializeActivityThread(entries: ActivityThreadEntry[]): string {
  return entries
    .map((entry) => {
      const ids = (entry.attachmentIds ?? []).filter(Boolean);
      const attachLine = ids.length ? `\n[[attachments:${ids.join(',')}]]` : '';
      if (!entry.dateLabel) return `${entry.body}${attachLine}`.trim();
      const stamp = `[${entry.dateLabel} ساعت ${entry.timeLabel}${entry.author ? ` — ${entry.author}` : ''}]`;
      return entry.body ? `${stamp}\n${entry.body}${attachLine}` : `${stamp}${attachLine}`;
    })
    .filter((chunk) => chunk.trim())
    .join('\n\n');
}

/** فایل‌ها را به یادداشت‌ها می‌چسباند: اول با شناسهٔ صریح، بعد با نزدیکی زمان. */
export function bindThreadMedia<T extends { id: string; createdAt: string }>(
  entries: ActivityThreadEntry[],
  images: T[],
  windowMs = COMMENT_MEDIA_WINDOW_MS,
): { blocks: Array<ActivityThreadEntry & { media: T[] }>; loose: T[] } {
  const blocks = entries.map((entry) => ({ ...entry, media: [] as T[] }));
  const byId = new Map(images.map((image) => [image.id, image]));
  const used = new Set<string>();

  blocks.forEach((block) => {
    for (const id of block.attachmentIds ?? []) {
      const image = byId.get(id);
      if (!image || used.has(id)) continue;
      block.media.push(image);
      used.add(id);
    }
  });

  for (const image of images) {
    if (used.has(image.id)) continue;
    const at = new Date(image.createdAt).getTime();
    if (Number.isNaN(at)) continue;
    let best = -1;
    let bestDelta = Number.POSITIVE_INFINITY;
    blocks.forEach((block, index) => {
      if (!block.at) return;
      const delta = block.at.getTime() - at;
      if (delta >= -60_000 && delta < bestDelta) {
        best = index;
        bestDelta = delta;
      }
    });
    if (best >= 0 && bestDelta <= windowMs) {
      blocks[best]!.media.push(image);
      used.add(image.id);
    }
  }

  const firstStamp = blocks.find((block) => block.at)?.at?.getTime() ?? Number.POSITIVE_INFINITY;
  const preamble = blocks.find((block) => !block.at);
  const loose: T[] = [];
  for (const image of images) {
    if (used.has(image.id)) continue;
    const at = new Date(image.createdAt).getTime();
    if (preamble && !Number.isNaN(at) && at < firstStamp) preamble.media.push(image);
    else loose.push(image);
  }
  return { blocks, loose };
}

function trimEntry(entry: ActivityThreadEntry): ActivityThreadEntry {
  return {
    ...entry,
    body: entry.body.trim(),
    attachmentIds: [...new Set((entry.attachmentIds ?? []).filter(Boolean))],
  };
}

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;
}