import { mount } from '@vue/test-utils';
import { createSSRApp, defineComponent, h, nextTick, ref } from 'vue';
import { renderToString } from '@vue/server-renderer';
import { afterEach, describe, expect, it, vi } from 'vitest';
import {
  createAdaptiveQualityController,
  type AdaptiveQualityController,
  type QualityDecision,
} from '@/journey/adaptive-quality';
import type { QualityTier } from '@/journey/motion-policy';

afterEach(() => {
  vi.restoreAllMocks();
  vi.unstubAllGlobals();
});

describe('adaptive quality controller', () => {
  it('starts a fresh epoch with a two-visible-second warm-up', () => {
    const controller = createAdaptiveQualityController('high');
    controller.enterRunningEpoch(1000);

    expect(controller.sampleFrame(2900, 2921)).toBeNull();
    expect(controller.snapshot()).toEqual({
      maximum: 'high',
      actual: 'high',
      epoch: 1,
      coolingDownUntil: null,
      eligibleSamples: 0,
      consecutiveBadLowWindows: 0,
    });

    expect(controller.sampleFrame(3000, 3021)).toBeNull();
    expect(controller.snapshot().eligibleSamples).toBe(1);
  });

  it('requires both five visible seconds and 120 eligible samples before closing a window', () => {
    const bySamples = createAdaptiveQualityController('high');
    bySamples.enterRunningEpoch(0);
    for (let index = 0; index < 120; index += 1) {
      expect(bySamples.sampleFrame(2000 + index, 2016 + index)).toBeNull();
    }
    expect(bySamples.snapshot().eligibleSamples).toBe(120);
    expect(bySamples.sampleFrame(6999, 7015)).toBeNull();
    expect(bySamples.snapshot().eligibleSamples).toBe(0);

    const byTime = createAdaptiveQualityController('high');
    byTime.enterRunningEpoch(0);
    for (let index = 0; index < 119; index += 1) {
      const start = 2000 + (index * 5000 / 118);
      expect(byTime.sampleFrame(start, start + 16)).toBeNull();
    }
    expect(byTime.snapshot().eligibleSamples).toBe(119);
  });

  it.each([
    ['high', 20, null],
    ['high', 20.01, 'medium'],
    ['medium', 25, null],
    ['medium', 25.01, 'low'],
  ] as const)('uses strict %s p95 threshold behavior at %s ms', (tier, p95, expectedNext) => {
    const controller = createAdaptiveQualityController(tier);
    controller.enterRunningEpoch(0);

    const result = feedWindow(controller, 2000, p95);

    if (expectedNext === null) {
      expect(result.decision).toBeNull();
      expect(controller.snapshot().actual).toBe(tier);
    } else {
      expect(result.decision).toEqual({
        previous: tier,
        next: expectedNext,
        reason: 'p95-window',
      });
    }
  });

  it('uses nearest-rank p95 rather than interpolation', () => {
    const sixSlow = createAdaptiveQualityController('high');
    sixSlow.enterRunningEpoch(0);
    const six = feedWindow(sixSlow, 2000, 21, 6);
    expect(six.decision).toBeNull();

    const sevenSlow = createAdaptiveQualityController('high');
    sevenSlow.enterRunningEpoch(0);
    const seven = feedWindow(sevenSlow, 2000, 21, 7);
    expect(seven.decision).toMatchObject({ previous: 'high', next: 'medium' });
  });

  it('requires two consecutive bad Low windows and resets the counter after a good one', () => {
    const controller = createAdaptiveQualityController('low');
    controller.enterRunningEpoch(0);

    const firstBad = feedWindow(controller, 2000, 40.01);
    expect(firstBad.decision).toBeNull();
    expect(controller.snapshot().consecutiveBadLowWindows).toBe(1);

    const good = feedWindow(controller, firstBad.end, 40);
    expect(good.decision).toBeNull();
    expect(controller.snapshot().consecutiveBadLowWindows).toBe(0);

    const nextBad = feedWindow(controller, good.end, 40.01);
    expect(nextBad.decision).toBeNull();
    expect(controller.snapshot().consecutiveBadLowWindows).toBe(1);

    const secondBad = feedWindow(controller, nextBad.end, 40.01);
    expect(secondBad.decision).toEqual({
      previous: 'low',
      next: 'static',
      reason: 'two-bad-low-windows',
    });
  });

  it.each([
    ['high', 'medium'],
    ['medium', 'low'],
    ['low', 'static'],
  ] as const)('downgrades %s immediately for a same-epoch interval over 250 ms', (tier, next) => {
    const controller = createAdaptiveQualityController(tier);
    controller.enterRunningEpoch(0);
    expect(controller.sampleFrame(2000, 2250)).toBeNull();

    expect(controller.sampleFrame(2250, 2500.01)).toEqual({
      previous: tier,
      next,
      reason: 'catastrophic-frame',
    });
  });

  it('rejects intervals spanning a pause/hidden epoch and resets its RAF baseline and window', () => {
    const controller = createAdaptiveQualityController('high');
    controller.enterRunningEpoch(0);
    controller.sampleFrame(2000, 2016);
    controller.leaveRunningEpoch();

    expect(controller.snapshot()).toMatchObject({ epoch: null, eligibleSamples: 0 });
    expect(controller.sampleFrame(2016, 9000)).toBeNull();

    controller.enterRunningEpoch(9000);
    expect(controller.sampleFrame(2016, 9016)).toBeNull();
    expect(controller.sampleFrame(10900, 10921)).toBeNull();
    expect(controller.snapshot().eligibleSamples).toBe(0);
    expect(controller.sampleFrame(11000, 11021)).toBeNull();
    expect(controller.snapshot().eligibleSamples).toBe(1);
  });

  it('counts the downgrade cooldown only in visible running time and performs a new warm-up', () => {
    const controller = createAdaptiveQualityController('high');
    controller.enterRunningEpoch(0);
    const downgrade = feedWindow(controller, 2000, 20.01);
    expect(downgrade.decision).toMatchObject({ next: 'medium' });
    const firstCooldownUntil = controller.snapshot().coolingDownUntil;
    expect(firstCooldownUntil).toBe(downgrade.end + 30000);

    controller.leaveRunningEpoch();
    controller.enterRunningEpoch(100000);
    expect(controller.snapshot().coolingDownUntil).toBe(130000);
    expect(controller.sampleFrame(129900, 129926)).toBeNull();
    expect(controller.snapshot().eligibleSamples).toBe(0);
    expect(controller.sampleFrame(131900, 131926)).toBeNull();
    expect(controller.snapshot().eligibleSamples).toBe(0);
    expect(controller.sampleFrame(132000, 132026)).toBeNull();
    expect(controller.snapshot().eligibleSamples).toBe(1);
  });

  it('resets the epoch/window on resize, downgrades to a lower maximum, and never auto-upgrades', () => {
    const controller = createAdaptiveQualityController('high');
    controller.enterRunningEpoch(0);
    controller.sampleFrame(2000, 2016);

    expect(controller.setMaximum('medium', 'resize')).toEqual({
      previous: 'high',
      next: 'medium',
      reason: 'maximum-change',
    });
    expect(controller.snapshot()).toMatchObject({
      maximum: 'medium',
      actual: 'medium',
      epoch: null,
      eligibleSamples: 0,
      consecutiveBadLowWindows: 0,
    });

    expect(controller.setMaximum('high', 'resize')).toBeNull();
    expect(controller.snapshot()).toMatchObject({ maximum: 'high', actual: 'medium' });
  });

  it('allows a deliberate manual maximum change to upgrade within that selected maximum', () => {
    const controller = createAdaptiveQualityController('medium');

    expect(controller.setMaximum('high', 'manual')).toEqual({
      previous: 'medium',
      next: 'high',
      reason: 'maximum-change',
    });
    expect(controller.snapshot()).toMatchObject({ maximum: 'high', actual: 'high' });
  });
});

describe('useAdaptiveQuality', () => {
  it('imports and renders on the server without browser globals', async () => {
    vi.resetModules();
    vi.stubGlobal('window', undefined);
    vi.stubGlobal('document', undefined);
    const { useAdaptiveQuality } = await import('@/composables/useAdaptiveQuality');
    const maximum = ref<'static'>('static');
    const sceneState = ref('static');
    const pageLifecycle = ref<'active'>('active');
    const app = createSSRApp(defineComponent({
      setup() {
        const adaptive = useAdaptiveQuality({ maximum, sceneState, pageLifecycle });
        return () => h('output', adaptive.snapshot.value.actual);
      },
    }));

    await expect(renderToString(app)).resolves.toBe('<output>static</output>');
  });

  it('tracks only visible active running epochs and tears down its lifecycle listener', async () => {
    const { useAdaptiveQuality } = await import('@/composables/useAdaptiveQuality');
    let visibility: DocumentVisibilityState = 'visible';
    Object.defineProperty(document, 'visibilityState', {
      configurable: true,
      get: () => visibility,
    });
    const maximum = ref<'high' | 'medium'>('high');
    const sceneState = ref('running');
    const pageLifecycle = ref<'active' | 'frozen'>('active');
    let now = 1000;
    const documentAdd = vi.spyOn(document, 'addEventListener');
    const documentRemove = vi.spyOn(document, 'removeEventListener');
    const wrapper = mount(defineComponent({
      setup: () => useAdaptiveQuality({ maximum, sceneState, pageLifecycle, now: () => now }),
      template: '<output />',
    }));

    expect(wrapper.vm.snapshot.epoch).toBe(1);
    expect(documentAdd).toHaveBeenCalledWith('visibilitychange', expect.any(Function), { passive: true });

    visibility = 'hidden';
    now = 2000;
    document.dispatchEvent(new Event('visibilitychange'));
    expect(wrapper.vm.snapshot.epoch).toBeNull();

    visibility = 'visible';
    now = 5000;
    document.dispatchEvent(new Event('visibilitychange'));
    expect(wrapper.vm.snapshot.epoch).toBe(2);

    pageLifecycle.value = 'frozen';
    await nextTick();
    expect(wrapper.vm.snapshot.epoch).toBeNull();

    pageLifecycle.value = 'active';
    sceneState.value = 'running';
    now = 7000;
    await nextTick();
    expect(wrapper.vm.snapshot.epoch).toBe(3);

    maximum.value = 'medium';
    now = 8000;
    await nextTick();
    expect(wrapper.vm.snapshot).toMatchObject({ maximum: 'medium', actual: 'medium', epoch: 4 });

    wrapper.unmount();
    expect(wrapper.vm.snapshot.epoch).toBeNull();
    expect(documentRemove).toHaveBeenCalledWith('visibilitychange', expect.any(Function), { passive: true });
  });

  it('never lets a visitor request bypass the device-resolved maximum', async () => {
    const { useAdaptiveQuality } = await import('@/composables/useAdaptiveQuality');
    Object.defineProperty(document, 'visibilityState', {
      configurable: true,
      value: 'visible',
    });
    const maximum = ref<QualityTier>('low');
    const sceneState = ref('running');
    const pageLifecycle = ref<'active'>('active');
    const wrapper = mount(defineComponent({
      setup: () => useAdaptiveQuality({ maximum, sceneState, pageLifecycle, now: () => 0 }),
      template: '<output />',
    }));

    expect(wrapper.vm.setMaximum('high', 'manual')).toBeNull();
    expect(wrapper.vm.snapshot).toMatchObject({ maximum: 'low', actual: 'low' });

    wrapper.unmount();
  });
});

function feedWindow(
  controller: AdaptiveQualityController,
  windowStart: number,
  slowDuration: number,
  slowCount = 120,
): { decision: QualityDecision | null; end: number } {
  let decision: QualityDecision | null = null;
  let end = windowStart;
  for (let index = 0; index < 120; index += 1) {
    const start = windowStart + (index * 5000 / 119);
    const duration = index >= 120 - slowCount ? slowDuration : 16;
    end = start + duration;
    decision = controller.sampleFrame(start, end);
  }
  return { decision, end };
}