/***********************************************************************************************************************************************************************
 * File Name: trustedDevice.service.js
 * Type of Program: Service
 * Description: Lets a login from an already-verified device skip the OTP
 *              gate. A device is trusted the first time its user clears an
 *              OTP; trust rolls forward 30 days on each trusted login and is
 *              tied to both an opaque cookie token (device_trust) and a
 *              User-Agent fingerprint, so a stolen cookie alone isn't enough
 *              once the fingerprint no longer matches. Ordinary logout does
 *              NOT revoke trust or clear the device_trust cookie — expires_at
 *              is the only thing that ends the OTP-skip window in the normal
 *              case, so logging out and back in on the same device still
 *              skips OTP until the 30-day window actually lapses. Trust is
 *              only force-revoked by password change/reset, admin ban/
 *              deactivate/force-logout, or a single session being explicitly
 *              terminated.
 * Author: Kenneth Obsequio
 * Date Created: Jul. 5, 2026
 ***********************************************************************************************************************************************************************
 * HOW TO USE:
 *   const trustedDevice = require('../services/trustedDevice.service');
 *   const fingerprintHash = trustedDevice.getFingerprintHash(req);
 *   const trusted = await trustedDevice.findValid(user.user_id, req.cookies.device_trust, fingerprintHash);
 *   if (trusted) { ...skip OTP... }
 *   await trustedDevice.issueOrRefresh(res, user.user_id, fingerprintHash, session.session_id);
 ***********************************************************************************************************************************************************************/
const crypto = require('crypto');
const mdl_TrustedDevices = require('../models/users/trusted_devices.mdl');
const { parseUA } = require('../utils/session_info.util');
const { hashToken } = require('../utils/token.util');

const TRUST_DAYS = 30;
const COOKIE_NAME = 'device_trust';

const getFingerprintHash = (req) => {
  const { browser, os, device } = parseUA(req.headers['user-agent']);
  return crypto.createHash('sha256').update(`${browser}|${os}|${device}`).digest('hex');
};

const cookieOptions = (maxAge) => ({
  httpOnly: true,
  secure:   process.env.NODE_ENV === 'production',
  sameSite: process.env.NODE_ENV === 'production' ? 'strict' : 'lax',
  maxAge,
});

/**
 * Looks up a non-revoked, non-expired trusted device matching both the
 * cookie token and the current request's fingerprint.
 *
 * Fails safe: any lookup error (e.g. table not migrated yet) is treated as
 * "not trusted" rather than propagating — a broken trust check should never
 * take down the login/OTP path itself, it should just fall back to OTP.
 * @returns {Promise<import('../models/users/trusted_devices.mdl')|null>}
 */
const findValid = async (userId, rawToken, fingerprintHash) => {
  if (!rawToken) return null;

  try {
    const row = await mdl_TrustedDevices.findOne({
      where: {
        user_id:           userId,
        device_token_hash: hashToken(rawToken),
        fingerprint_hash:  fingerprintHash,
        revoked_at:        null,
      },
    });
    return (row && new Date(row.expires_at) > new Date()) ? row : null;
  } catch (err) {
    console.error('[TRUSTED DEVICE] findValid failed, falling back to OTP:', err.message);
    return null;
  }
};

/**
 * Marks the current device as trusted for TRUST_DAYS, rolling the window
 * forward on repeat use, and sets the device_trust cookie.
 *
 * Fails safe: called after tokens/session are already minted, so a failure
 * here (e.g. table not migrated yet) must not break an otherwise-successful
 * login — it just means this device won't skip OTP next time.
 */
const issueOrRefresh = async (res, userId, fingerprintHash, sessionId) => {
  try {
    const rawToken = crypto.randomBytes(32).toString('hex');
    const expiresAt = new Date(Date.now() + TRUST_DAYS * 24 * 60 * 60 * 1000);
    const fields = {
      device_token_hash: hashToken(rawToken),
      expires_at:        expiresAt,
      revoked_at:        null,
      last_session_id:   sessionId,
    };

    // Plain find-then-create/update rather than findOrCreate() — Sequelize's
    // postgres findOrCreate() relies on a temp PL/pgSQL function for atomicity
    // that CockroachDB doesn't support ("cannot create user-defined functions
    // under a temporary schema").
    const row = await mdl_TrustedDevices.findOne({ where: { user_id: userId, fingerprint_hash: fingerprintHash } });
    if (row) {
      await row.update(fields);
    } else {
      await mdl_TrustedDevices.create({ user_id: userId, fingerprint_hash: fingerprintHash, ...fields });
    }

    res.cookie(COOKIE_NAME, rawToken, cookieOptions(TRUST_DAYS * 24 * 60 * 60 * 1000));
  } catch (err) {
    console.error('[TRUSTED DEVICE] issueOrRefresh failed:', err.message);
  }
};

/**
 * Revokes trust for one specific device by its cookie token. Not called by
 * the normal logout flow (see auth.controller.js exports.logout) — ordinary
 * logout intentionally leaves trust intact. Kept as a primitive for a
 * future explicit "forget this device" action, should one be added.
 */
const revokeByToken = async (userId, rawToken) => {
  if (!rawToken) return;
  try {
    await mdl_TrustedDevices.update(
      { revoked_at: new Date() },
      { where: { user_id: userId, device_token_hash: hashToken(rawToken), revoked_at: null } }
    );
  } catch (err) {
    console.error('[TRUSTED DEVICE] revokeByToken failed:', err.message);
  }
};

const revokeAllForUser = async (userId) => {
  try {
    await mdl_TrustedDevices.update(
      { revoked_at: new Date() },
      { where: { user_id: userId, revoked_at: null } }
    );
  } catch (err) {
    console.error('[TRUSTED DEVICE] revokeAllForUser failed:', err.message);
  }
};

const revokeBySessionId = async (sessionId) => {
  if (!sessionId) return;
  try {
    await mdl_TrustedDevices.update(
      { revoked_at: new Date() },
      { where: { last_session_id: sessionId, revoked_at: null } }
    );
  } catch (err) {
    console.error('[TRUSTED DEVICE] revokeBySessionId failed:', err.message);
  }
};

module.exports = {
  COOKIE_NAME,
  getFingerprintHash,
  findValid,
  issueOrRefresh,
  revokeByToken,
  revokeAllForUser,
  revokeBySessionId,
};