/***********************************************************************************************************************************************************************
 * File Name    : issue_certificates.cron.js
 * Type         : Cron Job
 * Description  : Issues certificates for users who passed a course assessment.
 *                Runs every hour on the hour and processes any
 *                pending_certificates row where issue_at <= NOW() and
 *                processed_at IS NULL.
 *
 *                For each ready row it:
 *                  1. Grants the course_completed_<uuid> achievement (the key
 *                     MyCertificates / Profile use to display certificate cards).
 *                  2. Persists the certificate record (cert_no/ref_no) via
 *                     services/certificate-record.service.js, so course.certificate
 *                     is populated immediately instead of only on first PDF download.
 *                  3. Sends a 'certificate_issued' UserNotification.
 *                  4. Marks the row processed_at = NOW() so it never fires again.
 *
 *                Safety pattern: processed_at is set only after both step 1 and
 *                step 2 succeed. If the process restarts mid-run the row will be
 *                picked up again on the next tick — both DB writes are idempotent.
 *
 * Schedule     : Every hour on the hour ("0 * * * *"). Registered by
 *                cron/client.cron.js.
 *
 * Author: Kenneth Obsequio (@lash0000)
 * Date Created: Jun. 24, 2026
 ***********************************************************************************************************************************************************************/
'use strict';

const { Op }             = require('sequelize');
const PendingCertificate = require('../../models/courses/pending_certificate.mdl');
const mdl_Achievements   = require('../../models/users/achievements.mdl');
const UserNotification   = require('../../models/notifications/user_notification.mdl');
const CronNotificationSetting = require('../../models/notifications/cron_notification_setting.mdl');
const { NOTIFICATION_REGISTRY } = require('../../data/notifications.data');
const { ensureCertificateRecord } = require('../../services/certificate-record.service');

async function run() {
    // Certificate/achievement issuance always happens — only the notification step is skippable.
    const settings = await CronNotificationSetting.findOne({ where: { job_name: 'issueCertificates' } });
    const notificationsEnabled = !settings || settings.enabled;

    // ── 1. Fetch all rows ready to process ────────────────────────────────────
    let rows;
    try {
        rows = await PendingCertificate.findAll({
            where: {
                issue_at:     { [Op.lte]: new Date() },
                processed_at: null,
            },
            raw: true,
        });
    } catch (err) {
        console.error('[CRON][ISSUE CERTS] Failed to query pending_certificates:', err);
        return;
    }

    if (rows.length === 0) return;

    console.log(`[CRON][ISSUE CERTS] Processing ${rows.length} pending certificate(s).`);

    for (const row of rows) {
        const { pending_id, user_id, course_uuid, course_title } = row;
        const achKey = `course_completed_${course_uuid}`;

        try {
            // ── 2. Grant course_completed_<uuid> achievement (idempotent) ──────
            const existing = await mdl_Achievements.findOne({ where: { user_id, key: achKey } });
            if (!existing) {
                await mdl_Achievements.create({
                    user_id,
                    type:        'milestone',
                    key:         achKey,
                    label:       'Certificate of Completion',
                    description: course_title ?? '',
                    granted_at:  new Date(),
                    metadata:    { courseTitle: course_title, courseUuid: course_uuid },
                });
            }

            // ── 3. Persist the actual certificate record (cert_no/ref_no) so
            //      course.certificate is populated immediately, instead of only
            //      lazily on first PDF download ────────────────────────────────
            await ensureCertificateRecord({ userId: user_id, courseId: row.course_id });

            // ── 4. Send certificate_issued notification ─────────────────────────
            if (notificationsEnabled) {
                await UserNotification.create({
                    user_id,
                    ...NOTIFICATION_REGISTRY.certificate_issued.build({
                        courseTitle: course_title ?? '',
                        courseUuid:  course_uuid,
                    }),
                });
            }

            // ── 5. Mark row processed ─────────────────────────────────────────
            await PendingCertificate.update(
                { processed_at: new Date() },
                { where: { pending_id } }
            );

            console.log(`[CRON][ISSUE CERTS] Issued certificate for user ${user_id} / course ${course_uuid}.`);
        } catch (err) {
            // Log and continue — next tick will retry this row
            if (err?.parent?.code !== '23505') {
                console.error(`[CRON][ISSUE CERTS] Failed for pending_id ${pending_id}:`, err);
            } else {
                // Unique constraint: achievement already exists — still mark processed
                await PendingCertificate.update(
                    { processed_at: new Date() },
                    { where: { pending_id } }
                ).catch(() => {});
            }
        }
    }
}

module.exports = {
    name:     'issueCertificates',
    schedule: '0 * * * *',
    run,
};