/***********************************************************************************************************************************************************************
 * File Name: achievements.service.js
 * Type of Program: Service
 * Description: Registry-based achievement auto-grant system.
 *              To add a new achievement — add an entry to utils/achievements.data.js.
 *              To trigger one — call grantAchievement(user_id, key, metadata).
 *
 * Author: Kenneth Obsequio (@lash0000)
 * Date Created: Jun. 11, 2026
 ***********************************************************************************************************************************************************************/
'use strict';

const { Op }                     = require('sequelize');
const mdl_Achievements           = require('../models/users/achievements.mdl');
const mdl_AchievementDefinitions = require('../models/users/achievement_definitions.mdl');
const mdl_Users                  = require('../models/users/users.mdl');
const { EARLY_ACCESS_CUTOFF }    = require('../data/achievements.data');
const UserNotification  = require('../models/notifications/user_notification.mdl');
const { NOTIFICATION_REGISTRY } = require('../data/notifications.data');

// ─── Core grant function ──────────────────────────────────────────────────────

/**
 * Grant an achievement to a user if not already granted.
 * Safe to call multiple times — idempotent via findOrCreate.
 *
 * @param {string|number} user_id
 * @param {string}        key        — must exist in the achievement_definitions catalog
 * @param {Object}        metadata   — optional extra data (course_id, score, etc.)
 * @param {string|number} granted_by — null = system, user_id = admin manual grant
 * @returns {{ achievement, created }} or null on error
 */
async function grantAchievement(user_id, key, metadata = {}, granted_by = null) {
  const def = await mdl_AchievementDefinitions.findOne({ where: { key, is_active: true } });
  if (!def) {
    console.warn(`[ACHIEVEMENTS] Unknown or inactive achievement key: "${key}"`);
    return null;
  }

  try {
    // CockroachDB doesn't support findOrCreate — use findOne + create
    const existing = await mdl_Achievements.findOne({ where: { user_id, key } });
    if (existing) return { achievement: existing, created: false };

    const achievement = await mdl_Achievements.create({
      user_id,
      type:        def.type,
      key:         def.key,
      label:       def.label,
      description: def.description,
      icon:        def.icon,
      granted_by:  granted_by ?? null,
      granted_at:  new Date(),
      metadata,
    });

    console.log(`[ACHIEVEMENTS] Granted "${key}" to user ${user_id}`);

    // Fire-and-forget — notification failure never blocks the achievement grant
    UserNotification.create({
      user_id,
      ...NOTIFICATION_REGISTRY.achievement.build({
        label:       def.label,
        description: def.description,
        key:         def.key,
      }),
    }).catch(err => console.error(`[ACHIEVEMENTS] Failed to emit notification for "${key}":`, err));

    return { achievement, created: true };
  } catch (err) {
    // Ignore unique constraint violation (race condition) — already granted
    if (err?.parent?.code === '23505') return null;
    console.error(`[ACHIEVEMENTS] Failed to grant "${key}" to user ${user_id}:`, err);
    return null;
  }
}

// ─── Convenience triggers ─────────────────────────────────────────────────────
// Call these from controllers after the relevant event occurs.

/** Call after verifyOTP / register succeeds */
async function onUserRegistered(user_id) {
  const user = await mdl_Users.findByPk(user_id, { attributes: ['user_id', 'createdAt'] });
  if (!user) return;
  if (new Date(user.createdAt) <= EARLY_ACCESS_CUTOFF) {
    await grantAchievement(user_id, 'early_access');
  }
}

/** Call after captureOrder succeeds and tier is activated */
async function onTierActivated(user_id, tier) {
  if (tier === 'premium')   await grantAchievement(user_id, 'premium_first_time');
  if (tier === 'exclusive') await grantAchievement(user_id, 'exclusive_first_time');
}

/** Call after a course is marked complete for a user */
async function onCourseCompleted(user_id, course_id, totalCompleted, course_title = null) {
  await grantAchievement(user_id, 'first_course_completed', { course_id, course_title });
  if (totalCompleted >= 5)  await grantAchievement(user_id, 'courses_completed_5');
  if (totalCompleted >= 10) await grantAchievement(user_id, 'courses_completed_10');
}

/** Call after a perfect quiz score */
async function onPerfectQuiz(user_id, quiz_id) {
  await grantAchievement(user_id, 'perfect_quiz_score', { quiz_id });
}

/** Call after a single task's requirements are all satisfied for a user */
async function onTaskCompleted(user_id, task_id, task_name = null) {
  await grantAchievement(user_id, 'first_task_completed', { task_id, task_name });
}

/** Call after every task in a task list is complete for a user */
async function onTaskListCompleted(user_id, task_list_id, task_list_name = null) {
  await grantAchievement(user_id, 'task_list_finisher', { task_list_id, task_list_name });
}

/** Call after profile is fully filled out */
async function onProfileCompleted(user_id) {
  await grantAchievement(user_id, 'profile_completed');
}

/** Call after a successful referral */
async function onReferral(user_id, referred_user_id) {
  await grantAchievement(user_id, 'first_referral', { referred_user_id });
}

// ─── Admin manual grant ───────────────────────────────────────────────────────

/** Manually grant any achievement from admin panel */
async function adminGrantAchievement(user_id, key, admin_id, metadata = {}) {
  return grantAchievement(user_id, key, metadata, admin_id);
}

// ─── Backfill ─────────────────────────────────────────────────────────────────

/** Run once to grant early_access to all existing eligible users */
async function backfillEarlyAccess() {
  const users = await mdl_Users.findAll({
    where:      { createdAt: { [Op.lte]: EARLY_ACCESS_CUTOFF } },
    attributes: ['user_id'],
    paranoid:   false,
  });

  console.log(`[ACHIEVEMENTS] Backfilling early_access for ${users.length} users...`);
  for (const user of users) {
    await grantAchievement(user.user_id, 'early_access');
  }
  console.log('[ACHIEVEMENTS] Backfill complete.');
}

// ─── Exports ──────────────────────────────────────────────────────────────────

module.exports = {
  grantAchievement,

  // Convenience triggers
  onUserRegistered,
  onTierActivated,
  onCourseCompleted,
  onPerfectQuiz,
  onProfileCompleted,
  onReferral,
  onTaskCompleted,
  onTaskListCompleted,

  // Admin
  adminGrantAchievement,

  // Backfill
  backfillEarlyAccess,
};