/***********************************************************************************************************************************************************************
 * File Name: certificate.controller.js  (client)
 * Type of Program: Controller
 * Description: Issues a PDF certificate for a completed course.
 *              A certificate is available only when the user has passed the course assessment.
 *              Certificate records are persisted (findOrCreate) so the same cert_no/ref_no is
 *              returned on every subsequent download.
 *
 * Author: Kenneth Obsequio (@lash0000)
 * Date Created: Jun. 18, 2026
 ***********************************************************************************************************************************************************************/
'use strict';

const R                       = require('../../utils/response.util');
const mdl_Users               = require('../../models/users/users.mdl');
const { generateCertificate } = require('../../services/certificate.service');
const { formatDuration }      = require('../../utils/duration.util');
const { fmtDate }             = require('../../utils/datetime.util');

const {
  Course,
  CourseAssessment,
  QuizAttempt,
  Certificate,
  CourseInstructor,
} = require('../../models/courses/courses.associations');

const notDeleted = { deletedAt: null };

// ─── Helpers ───────────────────────────────────────────────────────────────────

// cert_no format: YYYYMM-{userId:6}-{userCertSeq:5}
// userCertSeq = how many certs this user will have after this insert
async function buildCertNo(userId) {
  const count  = await Certificate.count({ where: { user_id: userId } });
  const seq    = String(count + 1).padStart(5, '0');
  const uid    = String(userId).padStart(6, '0');
  const now    = new Date();
  const YYYYMM = `${now.getFullYear()}${String(now.getMonth() + 1).padStart(2, '0')}`;
  return `${YYYYMM}-${uid}-${seq}`;
}

// ref_no format: PP-YYYYMM-{globalSeq:5}  (unique across all certs)
async function buildRefNo() {
  const count  = await Certificate.count();
  const seq    = String(count + 1).padStart(5, '0');
  const now    = new Date();
  const YYYYMM = `${now.getFullYear()}${String(now.getMonth() + 1).padStart(2, '0')}`;
  return `PP-${YYYYMM}-${seq}`;
}

function formatInstructors(rows) {
  const names = rows.map(r => r.display_name);
  if (names.length === 0) return '';
  if (names.length === 1) return names[0];
  if (names.length === 2) return `${names[0]} and ${names[1]}`;
  return `${names[0]}, ${names[1]} and et. al`;
}

// ─── GET /api/client/certificates/:courseUuid ──────────────────────────────────

exports.getCertificate = async (req, res) => {
  try {
    const { courseUuid } = req.params;
    const user_id        = req.user.user_id;

    // ── 1. Resolve course ──────────────────────────────────────────────────────
    const course = await Course.findOne({
      where:      { uuid: courseUuid, ...notDeleted },
      attributes: ['course_id', 'title', 'course_code', 'duration_seconds'],
      include: [
        {
          model:      CourseAssessment,
          as:         'assessment',
          attributes: ['assessment_id'],
          required:   false,
        },
        {
          model:      CourseInstructor,
          as:         'instructors',
          attributes: ['display_name', 'order_index'],
          required:   false,
          order:      [['order_index', 'ASC']],
        },
      ],
    });

    if (!course) return R.error(res, 'Course not found.', 404);

    if (!course.assessment) {
      return R.error(res, 'This course does not have an assessment — no certificate available.', 404);
    }

    // ── 2. Verify the user passed ──────────────────────────────────────────────
    const passedAttempt = await QuizAttempt.findOne({
      where: {
        user_id,
        assessment_id: course.assessment.assessment_id,
        passed:        true,
      },
      order:      [['createdAt', 'DESC']],
      attributes: ['score', 'createdAt'],
    });

    if (!passedAttempt) {
      return R.error(res, 'Certificate not available — course assessment not passed yet.', 403);
    }

    // ── 3. Get user's name ─────────────────────────────────────────────────────
    const user     = await mdl_Users.findByPk(user_id, { attributes: ['personal_info'] });
    const fullName = user?.personal_info?.name?.full_name?.trim() || 'Participant';

    // ── 4. Resolve or create the certificate record ────────────────────────────
    // CockroachDB does not support findOrCreate (uses temp PL/pgSQL functions).
    let cert = await Certificate.findOne({ where: { user_id, course_id: course.course_id } });
    if (!cert) {
      cert = await Certificate.create({
        user_id,
        course_id:   course.course_id,
        cert_no:     await buildCertNo(user_id),
        ref_no:      await buildRefNo(),
        instructors: formatInstructors(course.instructors ?? []),
        score:       passedAttempt.score ?? null,
        length_str:  formatDuration(course.duration_seconds),
        issued_at:   passedAttempt.createdAt,
      });
    }

    // Always use live instructors from course_instructors table for the PDF.
    // Keep the snapshot in sync so it reflects the current state.
    const liveInstructors = formatInstructors(course.instructors ?? []);
    if (liveInstructors !== (cert.instructors ?? '')) {
      await cert.update({ instructors: liveInstructors });
    }

    // ── 5. Format issued date as MM/DD/YY HH:MM AM/PM ───────────────────────────
    const issuedDate = new Date(cert.issued_at);
    const dateStr    = fmtDate(issuedDate);

    // ── 6. Generate PDF ────────────────────────────────────────────────────────
    const pdf = await generateCertificate({
      name:        fullName,
      course:      course.title,
      date:        dateStr,
      cert_no:     cert.cert_no,
      ref_no:      cert.ref_no,
      instructors: liveInstructors,
      length:      cert.length_str  ?? '',
    });

    // ── 7. Stream response ─────────────────────────────────────────────────────
    const nameParts  = fullName.trim().split(/\s+/);
    const lastName   = nameParts.length > 1 ? nameParts[nameParts.length - 1] : nameParts[0];
    const firstName  = nameParts.length > 1 ? nameParts.slice(0, -1).join(' ') : '';
    const safeTitle  = course.title.replace(/[/\\:*?"<>|]/g, '').trim();
    const filename   = `${lastName},${firstName}_${safeTitle}_${cert.cert_no}.pdf`;
    const asciiName  = filename.replace(/[^\x20-\x7E]/g, '_').replace(/"/g, '_');
    const encodedName = encodeURIComponent(filename);

    res.set({
      'Content-Type':        'application/pdf',
      'Content-Disposition': `attachment; filename="${asciiName}"; filename*=UTF-8''${encodedName}`,
      'Content-Length':      pdf.length,
    });

    return res.send(pdf);
  } catch (err) {
    console.error('[CLIENT][CERTIFICATE]', err);
    return R.error(res, 'Could not generate certificate.', 500);
  }
};