import { mount } from '@vue/test-utils';
import { createSSRApp, defineComponent, h, nextTick } from 'vue';
import { renderToString } from '@vue/server-renderer';
import { afterEach, describe, expect, it, vi } from 'vitest';
import { createScrollDriveController } from '@/journey/scroll-drive-controller';

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

describe('scroll drive controller', () => {
  it('starts and resets at a deterministic cruise snapshot', () => {
    const controller = createScrollDriveController();

    expect(controller.reset()).toEqual({
      scrollY: 0,
      routeProgress: 0,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
    expect(controller.reset({ scrollY: 250, now: 10, maxScrollY: 1000 })).toEqual({
      scrollY: 250,
      routeProgress: 0.25,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
  });

  it('uses the literal rise formula for a fixed finite sample', () => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: 0, now: 0, maxScrollY: 1000 });

    const snapshot = controller.sample({ scrollY: 50, now: 100, maxScrollY: 1000 });

    expect(snapshot.scrollY).toBe(50);
    expect(snapshot.routeProgress).toBe(0.05);
    expect(snapshot.direction).toBe(1);
    expect(snapshot.acceleration).toBeCloseTo(0.13416140243841887, 14);
    expect(snapshot.driveSpeed).toBeCloseTo(0.2900123499995034, 14);
  });

  it('uses the literal 420 ms decay formula when scrolling stops', () => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: 0, now: 0, maxScrollY: 1000 });
    controller.sample({ scrollY: 500, now: 100, maxScrollY: 1000 });

    const snapshot = controller.sample({ scrollY: 500, now: 200, maxScrollY: 1000 });

    expect(snapshot.direction).toBe(0);
    expect(snapshot.acceleration).toBeCloseTo(0.5286815391938753, 14);
    expect(snapshot.driveSpeed).toBeCloseTo(0.6135188621389778, 14);
  });

  it.each([
    ['NaN scroll position', { scrollY: Number.NaN, now: 10, maxScrollY: 1000 }],
    ['infinite scroll position', { scrollY: Number.POSITIVE_INFINITY, now: 10, maxScrollY: 1000 }],
    ['NaN timestamp', { scrollY: 10, now: Number.NaN, maxScrollY: 1000 }],
    ['infinite timestamp', { scrollY: 10, now: Number.POSITIVE_INFINITY, maxScrollY: 1000 }],
    ['NaN range', { scrollY: 10, now: 10, maxScrollY: Number.NaN }],
    ['infinite range', { scrollY: 10, now: 10, maxScrollY: Number.POSITIVE_INFINITY }],
  ])('falls back to finite cruise for an invalid sample: %s', (_label, input) => {
    const controller = createScrollDriveController();

    expect(controller.sample(input)).toEqual({
      scrollY: 0,
      routeProgress: 0,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
  });

  it.each([
    ['zero', 100],
    ['negative', 99],
  ])('emits cruise and does not integrate a %s dt', (_label, now) => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: 0, now: 100, maxScrollY: 1000 });

    expect(controller.sample({ scrollY: 500, now, maxScrollY: 1000 })).toEqual({
      scrollY: 500,
      routeProgress: 0.5,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
  });

  it('integrates an exact 250 ms interval', () => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: 0, now: 0, maxScrollY: 1000 });

    const snapshot = controller.sample({ scrollY: 625, now: 250, maxScrollY: 1000 });

    expect(snapshot.direction).toBe(1);
    expect(snapshot.acceleration).toBeCloseTo(0.9378234759778836, 14);
    expect(snapshot.driveSpeed).toBeCloseTo(0.9490152503018645, 14);
  });

  it('resets transient velocity and establishes a baseline after a gap over 250 ms', () => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: 0, now: 0, maxScrollY: 1000 });
    controller.sample({ scrollY: 500, now: 100, maxScrollY: 1000 });

    expect(controller.sample({ scrollY: 500, now: 351, maxScrollY: 1000 })).toEqual({
      scrollY: 500,
      routeProgress: 0.5,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
    expect(controller.sample({ scrollY: 600, now: 451, maxScrollY: 1000 }).direction).toBe(1);
  });

  it.each([
    ['downward', 0, 1000, 1],
    ['upward', 1000, 0, -1],
  ] as const)('clamps a maximum %s delta while preserving signed direction', (_label, start, end, direction) => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: start, now: 0, maxScrollY: 1000 });

    const snapshot = controller.sample({ scrollY: end, now: 100, maxScrollY: 1000 });

    expect(snapshot.direction).toBe(direction);
    expect(snapshot.acceleration).toBeCloseTo(0.6708070121920944, 14);
    expect(snapshot.driveSpeed).toBeCloseTo(0.7300617499975173, 14);
  });

  it.each([0, -1])('emits zero progress cruise for a non-positive range of %s', (maxScrollY) => {
    const controller = createScrollDriveController();

    expect(controller.sample({ scrollY: 500, now: 100, maxScrollY })).toEqual({
      scrollY: 500,
      routeProgress: 0,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
  });

  it('uses a denominator of at least one CSS pixel for a fractional scroll range', () => {
    const controller = createScrollDriveController();

    expect(controller.reset({ scrollY: 0.25, now: 100, maxScrollY: 0.5 }).routeProgress).toBe(0.25);
  });

  it('clamps route progress and recomputes it when the range changes during smoothing', () => {
    const controller = createScrollDriveController();
    controller.sample({ scrollY: 0, now: 0, maxScrollY: 1000 });
    controller.sample({ scrollY: 500, now: 100, maxScrollY: 1000 });

    expect(controller.sample({ scrollY: 500, now: 200, maxScrollY: 2000 })).toMatchObject({
      routeProgress: 0.25,
      acceleration: expect.closeTo(0.5286815391938753, 14),
    });
    expect(controller.reset({ scrollY: -10, now: 300, maxScrollY: 1000 }).routeProgress).toBe(0);
    expect(controller.reset({ scrollY: 1010, now: 400, maxScrollY: 1000 }).routeProgress).toBe(1);
  });
});

describe('useScrollDrive', () => {
  it('imports and renders on the server without browser globals', async () => {
    vi.resetModules();
    vi.stubGlobal('window', undefined);
    vi.stubGlobal('document', undefined);
    const { useScrollDrive } = await import('@/composables/useScrollDrive');
    const app = createSSRApp(defineComponent({
      setup() {
        const drive = useScrollDrive();
        return () => h('output', drive.value.driveSpeed.toString());
      },
    }));

    await expect(renderToString(app)).resolves.toBe('<output>0.18</output>');
  });

  it('initializes deterministically, batches passive events, resets visibility gaps, and tears down', async () => {
    const { useScrollDrive } = await import('@/composables/useScrollDrive');
    let visibility: DocumentVisibilityState = 'visible';
    Object.defineProperty(document, 'visibilityState', {
      configurable: true,
      get: () => visibility,
    });
    Object.defineProperties(document.documentElement, {
      scrollTop: { configurable: true, writable: true, value: 250 },
      scrollHeight: { configurable: true, value: 1500 },
      clientHeight: { configurable: true, value: 500 },
    });

    const visualViewport = new EventTarget() as VisualViewport;
    Object.defineProperty(visualViewport, 'height', { configurable: true, value: 500 });
    Object.defineProperty(window, 'visualViewport', { configurable: true, value: visualViewport });

    const callbacks = new Map<number, FrameRequestCallback>();
    let nextFrameId = 1;
    vi.stubGlobal('requestAnimationFrame', vi.fn((callback: FrameRequestCallback) => {
      const id = nextFrameId++;
      callbacks.set(id, callback);
      return id;
    }));
    vi.stubGlobal('cancelAnimationFrame', vi.fn((id: number) => callbacks.delete(id)));
    vi.spyOn(performance, 'now').mockReturnValue(100);
    const windowAdd = vi.spyOn(window, 'addEventListener');
    const documentAdd = vi.spyOn(document, 'addEventListener');
    const viewportAdd = vi.spyOn(visualViewport, 'addEventListener');

    const wrapper = mount(defineComponent({
      setup() {
        return { drive: useScrollDrive() };
      },
      template: '<output>{{ drive.routeProgress }}</output>',
    }));
    const drive = () => wrapper.vm.drive;

    expect(drive()).toMatchObject({
      scrollY: 250,
      routeProgress: 0.25,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });
    expect(callbacks).toHaveLength(0);
    expect(windowAdd).toHaveBeenCalledWith('scroll', expect.any(Function), { passive: true });
    expect(windowAdd).toHaveBeenCalledWith('resize', expect.any(Function), { passive: true });
    expect(documentAdd).toHaveBeenCalledWith('visibilitychange', expect.any(Function), { passive: true });
    expect(viewportAdd).toHaveBeenCalledWith('resize', expect.any(Function), { passive: true });
    expect(viewportAdd).toHaveBeenCalledWith('scroll', expect.any(Function), { passive: true });

    document.documentElement.scrollTop = 750;
    window.dispatchEvent(new Event('scroll'));
    window.dispatchEvent(new Event('scroll'));
    window.dispatchEvent(new Event('resize'));
    visualViewport.dispatchEvent(new Event('resize'));
    expect(callbacks).toHaveLength(1);

    const firstFrame = [...callbacks.entries()][0]!;
    callbacks.delete(firstFrame[0]);
    firstFrame[1](200);
    await nextTick();
    expect(drive()).toMatchObject({
      scrollY: 750,
      routeProgress: 0.75,
      direction: 1,
      acceleration: expect.closeTo(0.6708070121920944, 14),
      driveSpeed: expect.closeTo(0.7300617499975173, 14),
    });

    window.dispatchEvent(new Event('scroll'));
    expect(callbacks).toHaveLength(1);
    visibility = 'hidden';
    document.dispatchEvent(new Event('visibilitychange'));
    expect(callbacks).toHaveLength(0);
    expect(drive()).toMatchObject({ acceleration: 0, driveSpeed: 0.18 });

    visibility = 'visible';
    document.dispatchEvent(new Event('visibilitychange'));
    expect(callbacks).toHaveLength(1);
    const visibleFrame = [...callbacks.entries()][0]!;
    callbacks.delete(visibleFrame[0]);
    visibleFrame[1](1000);
    await nextTick();
    expect(drive()).toMatchObject({
      scrollY: 750,
      routeProgress: 0.75,
      direction: 0,
      acceleration: 0,
      driveSpeed: 0.18,
    });

    window.dispatchEvent(new Event('scroll'));
    expect(callbacks).toHaveLength(1);
    wrapper.unmount();
    expect(callbacks).toHaveLength(0);
    window.dispatchEvent(new Event('scroll'));
    visualViewport.dispatchEvent(new Event('scroll'));
    document.dispatchEvent(new Event('visibilitychange'));
    expect(callbacks).toHaveLength(0);
  });
});