import Database from 'better-sqlite3';
import crypto from 'crypto';

/**
 * Ensure data invariants after schema migration. Idempotent — safe to run
 * on every boot. Uses raw better-sqlite3 handle (not Drizzle ORM).
 */
export function ensureDefaults(db: Database.Database): void {
  // 1. Ensure the single-row instance_settings row exists
  const row = db.prepare('SELECT id FROM instance_settings WHERE id = 1').get();
  if (!row) {
    db.prepare(
      `INSERT OR IGNORE INTO instance_settings
        (id, max_bitrate_kbps, min_bitrate_kbps, bitrate_step_kbps,
         allowed_resolutions, allowed_framerates, max_resolution, max_framerate, updated_at)
       VALUES (1, 20000, 500, 500, ?, ?, 1080, 60, ?)`
    ).run('540,720,1080', '30,45,60', Date.now());
    console.log('[defaults] Inserted default instance_settings row');
  }

  // 2. Ensure a unique Snowflake worker ID is persisted (0-1023)
  const settings = db.prepare('SELECT worker_id FROM instance_settings WHERE id = 1').get() as
    { worker_id: number | null } | undefined;
  if (!settings || settings.worker_id === null) {
    const workerId = crypto.randomInt(0, 1024);
    db.prepare('UPDATE instance_settings SET worker_id = ? WHERE id = 1').run(workerId);
    console.log(`[defaults] Generated Snowflake worker ID: ${workerId}`);
  }

  // 2b. Ensure a persistent instance epoch (incarnation UUID) exists. A fresh
  // DB mints a new one — this is the discriminator for detecting resets.
  // The id=1 row is guaranteed by step 1's INSERT OR IGNORE above.
  const epochRow = db.prepare('SELECT instance_id FROM instance_settings WHERE id = 1').get() as
    { instance_id: string | null } | undefined;
  if (!epochRow || epochRow.instance_id === null) {
    const instanceId = crypto.randomUUID();
    const res = db.prepare('UPDATE instance_settings SET instance_id = ? WHERE id = 1').run(instanceId);
    if (res.changes !== 1) throw new Error('ensureDefaults: instance_settings id=1 row missing — cannot mint epoch');
    console.log('[defaults] Generated instance epoch');
  }

  // 3. Ensure at least one admin exists (promote earliest registered user)
  const anyAdmin = db.prepare('SELECT id FROM users WHERE is_admin = 1 LIMIT 1').get();
  if (!anyAdmin) {
    const firstUser = db.prepare(
      'SELECT id FROM users ORDER BY created_at ASC LIMIT 1'
    ).get() as { id: string } | undefined;
    if (firstUser) {
      db.prepare('UPDATE users SET is_admin = 1 WHERE id = ?').run(firstUser.id);
      console.log(`[defaults] Promoted first user ${firstUser.id} to admin`);
    }
  }
}

/**
 * One-time, idempotent recovery of 1-on-1 DM threads broken before the DM
 * tombstone fix: those had the deleted partner's dm_members row removed, making
 * the thread UI-unreachable. For each ownerId-NULL channel with exactly one
 * member, re-insert membership for any distinct dm_messages author that is
 * missing from dm_members and still exists in users. Safe to run every boot.
 */
export function backfillOneOnOneDmMembership(db: Database.Database): void {
  const broken = db.prepare(`
    SELECT dc.id AS channelId
    FROM dm_channels dc
    WHERE dc.owner_id IS NULL
      AND (SELECT COUNT(*) FROM dm_members dm WHERE dm.dm_channel_id = dc.id) = 1
  `).all() as { channelId: string }[];
  if (broken.length === 0) return;

  const missingAuthors = db.prepare(`
    SELECT DISTINCT msg.user_id AS userId
    FROM dm_messages msg
    JOIN users u ON u.id = msg.user_id
    WHERE msg.dm_channel_id = ?
      AND msg.user_id NOT IN (SELECT user_id FROM dm_members WHERE dm_channel_id = ?)
  `);
  const insertMember = db.prepare('INSERT INTO dm_members (dm_channel_id, user_id, closed) VALUES (?, ?, 0)');

  let restored = 0;
  const run = db.transaction(() => {
    for (const { channelId } of broken) {
      const authors = missingAuthors.all(channelId, channelId) as { userId: string }[];
      for (const { userId } of authors) { insertMember.run(channelId, userId); restored++; }
    }
  });
  run();
  if (restored > 0) console.log(`[backfill] restored ${restored} deleted-partner DM membership row(s)`);
}