// Сбор статистики TG-каналов.
// Сейчас: getChatMemberCount (подписчики).
// Потом: TGStat API (views, ERR, прирост).
//
// Вызывается из cron'а раз в час: POST /api/channel-stats/collect

const axios = require('axios');
const { query } = require('../config/db');
const settings = require('./settings');

/**
 * Собрать подписчиков для одного канала через Bot API.
 */
async function collectMembersForChannel(channel) {
  if (!channel.bot_token || !channel.tg_channel_id) return null;
  const base = await settings.get('TELEGRAM_API_BASE', 'https://api.telegram.org');
  try {
    const res = await axios.post(
      `${base}/bot${channel.bot_token}/getChatMemberCount`,
      { chat_id: channel.tg_channel_id },
      { timeout: 10000 }
    );
    if (!res.data?.ok) return null;
    return res.data.result; // число
  } catch (err) {
    console.warn(`[stats] getChatMemberCount failed channel=${channel.id}: ${err.message}`);
    return null;
  }
}

/**
 * Собрать и сохранить статистику для всех активных системных TG-каналов.
 */
async function collectAll() {
  const { rows: channels } = await query(
    `SELECT id, name, platform, bot_token, tg_channel_id
     FROM channels
     WHERE is_system = true AND is_active = true AND platform = 'telegram'`
  );

  const results = [];
  for (const ch of channels) {
    const members = await collectMembersForChannel(ch);
    if (members === null) {
      results.push({ channel_id: ch.id, name: ch.name, ok: false });
      continue;
    }
    // Сохраняем только если значение изменилось или нет записи за последние 55 мин
    // (чтобы не дублировать при частых вызовах)
    const { rows: last } = await query(
      `SELECT members FROM channel_stats
       WHERE channel_id=$1 AND captured_at > NOW() - INTERVAL '55 minutes'
       ORDER BY captured_at DESC LIMIT 1`,
      [ch.id]
    );
    if (last.length && last[0].members === members) {
      results.push({ channel_id: ch.id, name: ch.name, ok: true, members, saved: false, reason: 'no change' });
      continue;
    }
    await query(
      `INSERT INTO channel_stats (channel_id, members) VALUES ($1, $2)`,
      [ch.id, members]
    );
    console.log(`[stats] channel=${ch.name} members=${members}`);
    results.push({ channel_id: ch.id, name: ch.name, ok: true, members, saved: true });
  }
  return results;
}

/**
 * Получить историю подписчиков за последние N дней.
 */
async function getMembersHistory(channelId, days = 30) {
  const { rows } = await query(
    `SELECT
       date_trunc('hour', captured_at) AS hour,
       MAX(members) AS members
     FROM channel_stats
     WHERE channel_id=$1
       AND captured_at > NOW() - INTERVAL '${parseInt(days)} days'
     GROUP BY 1
     ORDER BY 1 ASC`,
    [channelId]
  );
  return rows;
}

/**
 * Получить текущую сводку по каналу.
 */
async function getChannelSummary(channelId) {
  // Последнее значение
  const { rows: latest } = await query(
    `SELECT members, captured_at FROM channel_stats
     WHERE channel_id=$1 ORDER BY captured_at DESC LIMIT 1`,
    [channelId]
  );
  // 24 часа назад
  const { rows: yesterday } = await query(
    `SELECT members FROM channel_stats
     WHERE channel_id=$1
       AND captured_at BETWEEN NOW() - INTERVAL '25 hours' AND NOW() - INTERVAL '23 hours'
     ORDER BY captured_at DESC LIMIT 1`,
    [channelId]
  );
  // 7 дней назад
  const { rows: weekAgo } = await query(
    `SELECT members FROM channel_stats
     WHERE channel_id=$1
       AND captured_at BETWEEN NOW() - INTERVAL '7 days 1 hour' AND NOW() - INTERVAL '6 days 23 hours'
     ORDER BY captured_at DESC LIMIT 1`,
    [channelId]
  );
  // Кол-во постов
  const { rows: postsCount } = await query(
    `SELECT COUNT(*) AS cnt FROM posts WHERE channel_id=$1`, [channelId]
  );

  const current = latest[0]?.members ?? null;
  const prev24h = yesterday[0]?.members ?? null;
  const prev7d  = weekAgo[0]?.members ?? null;

  return {
    members:       current,
    captured_at:   latest[0]?.captured_at ?? null,
    delta_24h:     current !== null && prev24h !== null ? current - prev24h : null,
    delta_7d:      current !== null && prev7d  !== null ? current - prev7d  : null,
    posts_total:   parseInt(postsCount[0]?.cnt ?? 0),
  };
}

module.exports = { collectAll, collectMembersForChannel, getMembersHistory, getChannelSummary };