// Backend/tests/k6/video-watching-load-test.js
//
// จำลองนักเรียนหลายคนดูวีดีโอพร้อมกัน (Concurrent Video Watching)
//
// Flow จริงที่ simulate:
//   1. Login ด้วย account ของ student แต่ละคน
//   2. Load หน้าเรียนคอร์ส (getCourseLearning)
//   3. เปิดบทเรียนวีดีโอ (getLessonContent)
//   4. Save progress ทุก 5 วินาที (จำลองการ watch)
//   5. เมื่อดูครบ (≥90%) → mark lesson complete
//
// Usage:
//   k6 run -e APP_URL=http://localhost:4000 -e COURSE_ID=1 -e LESSON_ID=1 tests/k6/video-watching-load-test.js
//
// ปรับจำนวน VUs และ duration ได้ด้วย:
//   k6 run -e APP_URL=http://localhost:4000 -e COURSE_ID=1 -e LESSON_ID=1 --vus 30 --duration 2m tests/k6/video-watching-load-test.js

import http from 'k6/http';
import { check, sleep, group } from 'k6';
import { Rate, Trend, Counter } from 'k6/metrics';
import { SharedArray } from 'k6/data';

// ─── Custom Metrics ───────────────────────────────────────────────────────────
const errorRate         = new Rate('errors');
const loginTime         = new Trend('login_duration', true);
const courseLearningTime = new Trend('course_learning_duration', true);
const lessonLoadTime    = new Trend('lesson_load_duration', true);
const progressSaveTime  = new Trend('progress_save_duration', true);
const completeLessonTime = new Trend('complete_lesson_duration', true);
const completedCount    = new Counter('completed_lessons');
const progressSaveCount = new Counter('progress_saves');

// ─── Load student credentials ────────────────────────────────────────────────
// อ่านจาก test-credentials.json (50 accounts)
const students = new SharedArray('students', function () {
  return JSON.parse(open('./test-credentials.json')).students;
});

// ─── Config ───────────────────────────────────────────────────────────────────
const BASE_URL  = __ENV.APP_URL  || 'http://192.168.1.137:4000';
const COURSE_ID = __ENV.COURSE_ID || '1';
const LESSON_ID = __ENV.LESSON_ID || '1';

// วีดีโอความยาว (วินาที) — ปรับตามจริง
const VIDEO_DURATION_SECONDS = parseInt(__ENV.VIDEO_DURATION || '300'); // default 5 นาที

// save progress interval: ทุก 5 วินาที (เหมือน client จริง)
// แต่ในการ test เราจะ simulate เร็วขึ้นโดยใช้ sleep น้อยลง
const PROGRESS_INTERVAL_SECONDS = parseInt(__ENV.PROGRESS_INTERVAL || '15');

// ─── Test Options ─────────────────────────────────────────────────────────────
export const options = {
  stages: [
    { duration: '30s', target: 10 },  // Ramp up: 10 คนเริ่มดูวีดีโอ
    { duration: '1m',  target: 30 },  // Ramp up: เพิ่มเป็น 30 คน
    { duration: '2m',  target: 30 },  // Steady: 30 คนดูพร้อมกัน
    { duration: '30s', target: 50 },  // Peak: เพิ่มเป็น 50 คน
    { duration: '1m',  target: 50 },  // Steady Peak: 50 คนพร้อมกัน
    { duration: '30s', target: 0 },   // Ramp down
  ],
  thresholds: {
    // Response times
    'login_duration':           ['p(95)<2000'],    // Login < 2s
    'course_learning_duration': ['p(95)<1000'],    // Load course page < 1s
    'lesson_load_duration':     ['p(95)<1000'],    // Load lesson < 1s
    'progress_save_duration':   ['p(95)<500'],     // Save progress < 500ms (critical — บ่อย)
    'complete_lesson_duration': ['p(95)<1000'],    // Complete lesson < 1s

    // Error rate
    'errors':           ['rate<0.05'],  // Error < 5%
    'http_req_failed':  ['rate<0.05'],  // HTTP error < 5%
  },
};

// ─── Helper ───────────────────────────────────────────────────────────────────
function jsonHeaders(token) {
  const h = { 'Content-Type': 'application/json' };
  if (token) h['Authorization'] = `Bearer ${token}`;
  return h;
}

// ─── Main ─────────────────────────────────────────────────────────────────────
export default function () {
  // แต่ละ VU ใช้ account คนละคน (round-robin ถ้า VU มากกว่า 50)
  const student = students[__VU % students.length];

  let token = null;

  // ── Step 1: Login ──────────────────────────────────────────────────────────
  group('1. Login', () => {
    const res = http.post(
      `${BASE_URL}/api/auth/login`,
      JSON.stringify({ identifier: student.email, password: student.password }),
      { headers: jsonHeaders(null) }
    );

    loginTime.add(res.timings.duration);
    const ok = res.status === 200;
    errorRate.add(!ok);

    check(res, {
      'login: status 200':  (r) => r.status === 200,
      'login: has token':   (r) => {
        try { return !!r.json('data.token'); } catch { return false; }
      },
    });

    if (ok) {
      try { token = res.json('data.token'); } catch {}
    }
  });

  if (!token) {
    console.warn(`[VU ${__VU}] Login failed for ${student.email} — skipping`);
    sleep(2);
    return;
  }

  sleep(1);

  // ── Step 2: Enroll (ถ้ายังไม่ได้ enroll) ──────────────────────────────────
  group('2. Enroll Course', () => {
    const res = http.post(
      `${BASE_URL}/api/students/courses/${COURSE_ID}/enroll`,
      null,
      { headers: jsonHeaders(token) }
    );

    // 200 = enrolled OK, 409 = already enrolled (ทั้งคู่ถือว่าดี)
    const ok = res.status === 200 || res.status === 409;
    errorRate.add(!ok);
    check(res, {
      'enroll: enrolled or already enrolled': (r) => r.status === 200 || r.status === 409,
    });
  });

  sleep(1);

  // ── Step 3: Load course learning page ─────────────────────────────────────
  group('3. Load Course Learning Page', () => {
    const res = http.get(
      `${BASE_URL}/api/students/courses/${COURSE_ID}/learn`,
      { headers: jsonHeaders(token) }
    );

    courseLearningTime.add(res.timings.duration);
    const ok = res.status === 200;
    errorRate.add(!ok);
    check(res, {
      'course learn: status 200': (r) => r.status === 200,
    });
  });

  sleep(1);

  // ── Step 4: Open lesson (load video content) ───────────────────────────────
  group('4. Open Lesson', () => {
    const res = http.get(
      `${BASE_URL}/api/students/courses/${COURSE_ID}/lessons/${LESSON_ID}`,
      { headers: jsonHeaders(token) }
    );

    lessonLoadTime.add(res.timings.duration);
    const ok = res.status === 200;
    errorRate.add(!ok);
    check(res, {
      'lesson: status 200': (r) => r.status === 200,
    });
  });

  sleep(2); // รอ video buffer เล็กน้อย

  // ── Step 5: Simulate watching — save progress ทุก PROGRESS_INTERVAL วิ ─────
  // จำลองการดูวีดีโอ: progress เพิ่มขึ้นเรื่อยๆ จนถึง 95% (auto-complete threshold)
  group('5. Watch Video (Save Progress)', () => {
    const targetSeconds = Math.floor(VIDEO_DURATION_SECONDS * 0.95); // ดูถึง 95%
    const steps = Math.ceil(targetSeconds / PROGRESS_INTERVAL_SECONDS); // จำนวนครั้งที่ save

    // เพื่อไม่ให้ test นาน เกินไป จำกัดไว้ที่ 20 saves per VU iteration
    const maxSaves = Math.min(steps, 20);

    for (let i = 1; i <= maxSaves; i++) {
      const currentSeconds = i * PROGRESS_INTERVAL_SECONDS;

      const res = http.post(
        `${BASE_URL}/api/students/lessons/${LESSON_ID}/progress`,
        JSON.stringify({
          video_progress_seconds: currentSeconds,
          video_duration_seconds: VIDEO_DURATION_SECONDS,
        }),
        { headers: jsonHeaders(token) }
      );

      progressSaveTime.add(res.timings.duration);
      progressSaveCount.add(1);

      const ok = res.status === 200;
      errorRate.add(!ok);
      check(res, {
        'progress save: status 200': (r) => r.status === 200,
        'progress save: fast':       (r) => r.timings.duration < 500,
      });

      // รอ interval จริง (ย่อจาก 5s จริง เหลือ 1s เพื่อให้ test ไม่นานเกิน)
      sleep(1);
    }
  });

  // ── Step 6: Mark lesson complete ───────────────────────────────────────────
  group('6. Complete Lesson', () => {
    const res = http.post(
      `${BASE_URL}/api/students/courses/${COURSE_ID}/lessons/${LESSON_ID}/complete`,
      null,
      { headers: jsonHeaders(token) }
    );

    completeLessonTime.add(res.timings.duration);
    const ok = res.status === 200;

    // 200 = completed now, อาจ 409 ถ้า already completed (ถือว่าโอเค)
    errorRate.add(res.status !== 200 && res.status !== 409);
    if (ok) completedCount.add(1);

    check(res, {
      'complete: status 200 or 409': (r) => r.status === 200 || r.status === 409,
    });
  });

  sleep(1);
}

// ─── Summary ──────────────────────────────────────────────────────────────────
export function handleSummary(data) {
  const m = data.metrics;

  const avg    = (k) => m[k]?.values?.avg?.toFixed(0)  ?? 'N/A';
  const p95    = (k) => m[k]?.values?.['p(95)']?.toFixed(0) ?? 'N/A';
  const rate   = (k) => ((m[k]?.values?.rate ?? 0) * 100).toFixed(2);
  const count  = (k) => m[k]?.values?.count ?? 0;

  return {
    stdout: `
╔══════════════════════════════════════════════════════════╗
║          Concurrent Video Watching — Load Test           ║
╠══════════════════════════════════════════════════════════╣
║  Course ID : ${COURSE_ID.padEnd(44)}║
║  Lesson ID : ${LESSON_ID.padEnd(44)}║
║  Video     : ${String(VIDEO_DURATION_SECONDS + 's').padEnd(44)}║
╠══════════════════════════════════════════════════════════╣
║  RESPONSE TIMES (avg / p95)                              ║
║  Login               : ${avg('login_duration')}ms / ${p95('login_duration')}ms${' '.repeat(Math.max(0, 20 - avg('login_duration').length - p95('login_duration').length))}║
║  Course Learning Page: ${avg('course_learning_duration')}ms / ${p95('course_learning_duration')}ms${' '.repeat(Math.max(0, 20 - avg('course_learning_duration').length - p95('course_learning_duration').length))}║
║  Lesson Load         : ${avg('lesson_load_duration')}ms / ${p95('lesson_load_duration')}ms${' '.repeat(Math.max(0, 20 - avg('lesson_load_duration').length - p95('lesson_load_duration').length))}║
║  Save Progress       : ${avg('progress_save_duration')}ms / ${p95('progress_save_duration')}ms${' '.repeat(Math.max(0, 20 - avg('progress_save_duration').length - p95('progress_save_duration').length))}║
║  Complete Lesson     : ${avg('complete_lesson_duration')}ms / ${p95('complete_lesson_duration')}ms${' '.repeat(Math.max(0, 20 - avg('complete_lesson_duration').length - p95('complete_lesson_duration').length))}║
╠══════════════════════════════════════════════════════════╣
║  COUNTS                                                  ║
║  Total Requests      : ${String(count('http_reqs')).padEnd(33)}║
║  Progress Saves      : ${String(count('progress_saves')).padEnd(33)}║
║  Lessons Completed   : ${String(count('completed_lessons')).padEnd(33)}║
╠══════════════════════════════════════════════════════════╣
║  ERROR RATES                                             ║
║  HTTP Failed         : ${(rate('http_req_failed') + '%').padEnd(33)}║
║  Custom Errors       : ${(rate('errors') + '%').padEnd(33)}║
╚══════════════════════════════════════════════════════════╝
`,
  };
}