const express = require('express');
const bcrypt = require('bcryptjs');
const pool = require('../db');
const { requirePermission } = require('../middleware/auth');
const { logCuratorAction } = require('../audit-log');
const { ALL_PERMISSIONS, normalizePermissions } = require('../permissions');

const router = express.Router();

const USER_SELECT = `id, username, role, permissions, is_active, created_at, last_login_at`;

function mapUser(row) {
  return {
    id: row.id,
    username: row.username,
    role: row.role,
    permissions: row.role === 'admin' ? [...ALL_PERMISSIONS] : normalizePermissions(row.permissions),
    is_active: row.is_active !== false,
    created_at: row.created_at,
    last_login_at: row.last_login_at,
  };
}

function parseRole(raw) {
  if (raw === 'admin' || raw === 'curator') return raw;
  return null;
}

async function countActiveAdmins(client = pool) {
  const { rows } = await client.query(
    `SELECT COUNT(*)::int AS n FROM users WHERE role = 'admin' AND is_active = true`
  );
  return rows[0].n;
}

async function clearUserSessions(userId) {
  // connect-pg-simple stores session JSON with userId
  await pool.query(`DELETE FROM session WHERE (sess->>'userId')::int = $1`, [userId]);
}

/** Keep users_id_seq ahead of existing rows (restore inserts explicit ids). */
async function syncUsersIdSequence() {
  await pool.query(
    `SELECT setval(
       pg_get_serial_sequence('users', 'id'),
       GREATEST(1, COALESCE((SELECT MAX(id) FROM users), 1)),
       true
     )`
  );
}

router.use(requirePermission('users'));

router.get('/', async (_req, res) => {
  try {
    const { rows } = await pool.query(
      `SELECT ${USER_SELECT} FROM users ORDER BY username ASC`
    );
    res.json({ users: rows.map(mapUser), permissions: ALL_PERMISSIONS });
  } catch (err) {
    console.error('Users list error:', err.message);
    res.status(500).json({ error: 'Failed to list users' });
  }
});

router.post('/', async (req, res) => {
  try {
    const username =
      typeof req.body?.username === 'string' ? req.body.username.trim() : '';
    const password = typeof req.body?.password === 'string' ? req.body.password : '';
    const role = parseRole(req.body?.role) || 'curator';
    const permissions = normalizePermissions(req.body?.permissions);

    if (!username || username.length < 2 || username.length > 64) {
      return res.status(400).json({ error: 'Username must be 2–64 characters' });
    }
    if (!/^[a-zA-Z0-9._-]+$/.test(username)) {
      return res.status(400).json({ error: 'Username may only contain letters, numbers, . _ -' });
    }
    if (!password || password.length < 8) {
      return res.status(400).json({ error: 'Password must be at least 8 characters' });
    }
    if (role === 'admin' && req.curatorUser.role !== 'admin') {
      return res.status(403).json({ error: 'Only admins can create admin accounts' });
    }

    const passwordHash = await bcrypt.hash(password, 10);
    const storedPermissions = role === 'admin' ? ALL_PERMISSIONS : permissions;

    const { rows: taken } = await pool.query(
      `SELECT username FROM users WHERE LOWER(username) = LOWER($1) LIMIT 1`,
      [username]
    );
    if (taken[0]) {
      return res.status(409).json({ error: 'Username already exists' });
    }

    await syncUsersIdSequence();

    const { rows } = await pool.query(
      `INSERT INTO users (username, password_hash, role, permissions, is_active)
       VALUES ($1, $2, $3, $4::text[], true)
       RETURNING ${USER_SELECT}`,
      [username, passwordHash, role, storedPermissions]
    );

    await logCuratorAction({
      userId: req.curatorUser.id,
      action: 'user.create',
      resourceType: 'user',
      resourceId: rows[0].id,
      details: { username, role, permissions: storedPermissions },
      req,
    });

    res.status(201).json({ user: mapUser(rows[0]) });
  } catch (err) {
    if (err.code === '23505') {
      if (err.constraint === 'users_pkey') {
        console.error('Users create PK conflict (sequence lag):', err.detail || err.message);
        return res.status(409).json({
          error: 'Could not allocate user id — retry create (sequence was out of sync)',
        });
      }
      return res.status(409).json({ error: 'Username already exists' });
    }
    console.error('Users create error:', err.message);
    res.status(500).json({ error: 'Failed to create user' });
  }
});

router.patch('/:id', async (req, res) => {
  try {
    const id = parseInt(req.params.id, 10);
    if (!Number.isFinite(id)) return res.status(400).json({ error: 'Invalid id' });

    const { rows: existingRows } = await pool.query(
      `SELECT ${USER_SELECT} FROM users WHERE id = $1`,
      [id]
    );
    if (!existingRows[0]) return res.status(404).json({ error: 'User not found' });
    const existing = existingRows[0];

    let role = existing.role;
    if (req.body?.role !== undefined) {
      const parsed = parseRole(req.body.role);
      if (!parsed) return res.status(400).json({ error: 'Invalid role' });
      if (parsed === 'admin' && req.curatorUser.role !== 'admin') {
        return res.status(403).json({ error: 'Only admins can promote to admin' });
      }
      if (existing.role === 'admin' && parsed !== 'admin' && req.curatorUser.role !== 'admin') {
        return res.status(403).json({ error: 'Only admins can demote admins' });
      }
      role = parsed;
    }

    let permissions = normalizePermissions(existing.permissions);
    if (req.body?.permissions !== undefined) {
      permissions = normalizePermissions(req.body.permissions);
    }
    if (role === 'admin') {
      permissions = [...ALL_PERMISSIONS];
    }

    let isActive = existing.is_active !== false;
    if (req.body?.is_active !== undefined) {
      if (typeof req.body.is_active !== 'boolean') {
        return res.status(400).json({ error: 'is_active must be boolean' });
      }
      isActive = req.body.is_active;
    }

    if (
      existing.role === 'admin' &&
      existing.is_active !== false &&
      (role !== 'admin' || !isActive)
    ) {
      const admins = await countActiveAdmins();
      if (admins <= 1) {
        return res.status(400).json({ error: 'Cannot deactivate or demote the last active admin' });
      }
    }

    const { rows } = await pool.query(
      `UPDATE users
       SET role = $2, permissions = $3::text[], is_active = $4
       WHERE id = $1
       RETURNING ${USER_SELECT}`,
      [id, role, permissions, isActive]
    );

    if (!isActive) {
      await clearUserSessions(id);
    }

    await logCuratorAction({
      userId: req.curatorUser.id,
      action: 'user.update',
      resourceType: 'user',
      resourceId: id,
      details: {
        username: rows[0].username,
        role,
        permissions,
        is_active: isActive,
      },
      req,
    });

    res.json({ user: mapUser(rows[0]) });
  } catch (err) {
    console.error('Users update error:', err.message);
    res.status(500).json({ error: 'Failed to update user' });
  }
});

router.post('/:id/password', async (req, res) => {
  try {
    const id = parseInt(req.params.id, 10);
    if (!Number.isFinite(id)) return res.status(400).json({ error: 'Invalid id' });

    const password = typeof req.body?.password === 'string' ? req.body.password : '';
    if (!password || password.length < 8) {
      return res.status(400).json({ error: 'Password must be at least 8 characters' });
    }

    const { rows: existingRows } = await pool.query(
      `SELECT id, username, role FROM users WHERE id = $1`,
      [id]
    );
    if (!existingRows[0]) return res.status(404).json({ error: 'User not found' });

    if (existingRows[0].role === 'admin' && req.curatorUser.role !== 'admin' && req.curatorUser.id !== id) {
      return res.status(403).json({ error: 'Only admins can reset another admin password' });
    }

    const passwordHash = await bcrypt.hash(password, 10);
    await pool.query(`UPDATE users SET password_hash = $2 WHERE id = $1`, [id, passwordHash]);
    await clearUserSessions(id);

    await logCuratorAction({
      userId: req.curatorUser.id,
      action: 'user.reset_password',
      resourceType: 'user',
      resourceId: id,
      details: { username: existingRows[0].username },
      req,
    });

    res.json({ ok: true });
  } catch (err) {
    console.error('Users password error:', err.message);
    res.status(500).json({ error: 'Failed to reset password' });
  }
});

module.exports = router;