const { normalizePermissionKeys } = require('../../rbac');

function createSessionService(options) {
  const sessionCookieName = String(options && options.sessionCookieName || '').trim();
  const sessionMaxAgeMs = Number(options && options.sessionMaxAgeMs);
  const hashSessionToken = options && options.hashSessionToken;
  const createSessionToken = options && options.createSessionToken;

  if (!sessionCookieName || !Number.isFinite(sessionMaxAgeMs) || typeof hashSessionToken !== 'function' || typeof createSessionToken !== 'function') {
    throw new Error('createSessionService requires the session dependencies.');
  }

  function parseCookies(cookieHeader) {
    return String(cookieHeader || '').split(/;\s*/).reduce(function (cookies, pair) {
      if (!pair) {
        return cookies;
      }
      const separatorIndex = pair.indexOf('=');
      if (separatorIndex === -1) {
        return cookies;
      }
      const name = decodeURIComponent(pair.slice(0, separatorIndex).trim());
      const value = decodeURIComponent(pair.slice(separatorIndex + 1).trim());
      if (name) {
        cookies[name] = value;
      }
      return cookies;
    }, {});
  }

  function serializeCookie(name, value, options) {
    const parts = [`${encodeURIComponent(name)}=${encodeURIComponent(value)}`];
    if (options && options.maxAge !== undefined) {
      parts.push(`Max-Age=${Math.max(0, Math.trunc(Number(options.maxAge) / 1000))}`);
    }
    parts.push('Path=/');
    parts.push('HttpOnly');
    parts.push('SameSite=Lax');
    return parts.join('; ');
  }

  function clearSessionCookie(res) {
    res.setHeader('Set-Cookie', serializeCookie(sessionCookieName, '', { maxAge: 0 }));
  }

  function setSessionCookie(res, token) {
    res.setHeader('Set-Cookie', serializeCookie(sessionCookieName, token, { maxAge: sessionMaxAgeMs }));
  }

  async function loadCurrentUser(pool, req) {
    const cookies = parseCookies(req.headers.cookie || '');
    const token = cookies[sessionCookieName];
    if (!token) {
      return null;
    }

    const tokenHash = hashSessionToken(token);
    const [rows] = await pool.query(
      `SELECT s.user_id, u.id, u.name, u.username
      FROM a_sessions s
      JOIN a_users u ON u.id = s.user_id
       WHERE s.session_hash = ?
         AND s.expires_at > NOW()
       LIMIT 1`,
      [tokenHash]
    );
    if (!rows.length) {
      return null;
    }

    const userId = Number(rows[0].id);
    const [roleRows] = await pool.query(
      `SELECT r.role_key
      FROM a_user_roles ur
      JOIN a_roles r ON r.id = ur.role_id
       WHERE ur.user_id = ?
       ORDER BY r.name ASC`,
      [userId]
    );
    const [permissionRows] = await pool.query(
      `SELECT p.permission_key
      FROM a_user_roles ur
      JOIN a_role_permissions rp ON rp.role_id = ur.role_id
      JOIN a_permissions p ON p.id = rp.permission_id
       WHERE ur.user_id = ?
       ORDER BY p.section_name ASC, p.name ASC`,
      [userId]
    );

    await pool.query('UPDATE a_sessions SET last_used_at = CURRENT_TIMESTAMP, modified_by = ? WHERE session_hash = ?', [rows[0].user_id, tokenHash]);
    return Object.assign({}, rows[0], {
      roleKeys: roleRows.map(function (row) {
        return String(row.role_key || '').trim();
      }).filter(Boolean),
      permissionKeys: normalizePermissionKeys(permissionRows.map(function (row) {
        return String(row.permission_key || '').trim();
      }))
    });
  }

  async function createUserSession(pool, userId) {
    const token = createSessionToken();
    const tokenHash = hashSessionToken(token);
    const expiresAt = new Date(Date.now() + sessionMaxAgeMs);
    await pool.query(
      'INSERT INTO a_sessions (session_hash, user_id, expires_at, created_by, modified_by) VALUES (?, ?, ?, ?, ?)',
      [tokenHash, userId, expiresAt, userId, userId]
    );
    return token;
  }

  function requireAuth(req, res, next) {
    if (req.currentUser) {
      return next();
    }
    res.redirect('/login?message=' + encodeURIComponent('Please sign in to continue.'));
  }

  return {
    parseCookies: parseCookies,
    serializeCookie: serializeCookie,
    clearSessionCookie: clearSessionCookie,
    setSessionCookie: setSessionCookie,
    loadCurrentUser: loadCurrentUser,
    createUserSession: createUserSession,
    requireAuth: requireAuth
  };
}

module.exports = { createSessionService };