import React from 'react';
import '@testing-library/jest-dom';
import { render, screen, waitFor, fireEvent, act } from '@testing-library/react';
import { MemoryRouter, Route, Routes } from 'react-router-dom';
import { describe, it, expect, vi, beforeEach } from 'vitest';
import FeedItems from './FeedItems';

describe('FeedItems Component', () => {
  beforeEach(() => {
    vi.resetAllMocks();
    global.fetch = vi.fn();
    window.HTMLElement.prototype.scrollIntoView = vi.fn();

    // Mock IntersectionObserver
    class MockIntersectionObserver {
      observe = vi.fn();
      unobserve = vi.fn();
      disconnect = vi.fn();
    }
    window.IntersectionObserver = MockIntersectionObserver as any;
  });

  it('renders loading state', () => {
    (global.fetch as any).mockImplementation(() => new Promise(() => { }));
    render(
      <MemoryRouter initialEntries={['/feed/1']}>
        <Routes>
          <Route path="/feed/:feedId" element={<FeedItems />} />
        </Routes>
      </MemoryRouter>
    );
    expect(screen.getByText(/loading items/i)).toBeInTheDocument();
  });

  it('renders items for a feed', async () => {
    const mockItems = [
      {
        _id: 101,
        title: 'Item One',
        url: 'http://example.com/1',
        publish_date: '2023-01-01',
        read: false,
      },
      {
        _id: 102,
        title: 'Item Two',
        url: 'http://example.com/2',
        publish_date: '2023-01-02',
        read: true,
      },
    ];

    (global.fetch as any).mockResolvedValueOnce({
      ok: true,
      json: async () => mockItems,
    });

    render(
      <MemoryRouter initialEntries={['/feed/1']}>
        <Routes>
          <Route path="/feed/:feedId" element={<FeedItems />} />
        </Routes>
      </MemoryRouter>
    );

    await waitFor(() => {
      expect(screen.getByText('Item One')).toBeInTheDocument();
    });

    const params = new URLSearchParams();
    params.append('feed_id', '1');
    params.append('read_filter', 'unread');
    expect(global.fetch).toHaveBeenCalledWith(`/api/stream?${params.toString()}`, expect.anything());
  });

  it('handles keyboard shortcuts', async () => {
    const mockItems = [
      { _id: 101, title: 'Item 1', url: 'u1', read: false, starred: false },
      { _id: 102, title: 'Item 2', url: 'u2', read: true, starred: false },
    ];

    (global.fetch as any).mockResolvedValue({
      ok: true,
      json: async () => mockItems,
    });

    render(
      <MemoryRouter>
        <FeedItems />
      </MemoryRouter>
    );

    await waitFor(() => {
      expect(screen.getByText('Item 1')).toBeVisible();
    });

    // Press 'j' to select first item (index 0 -> 1 because it starts at -1... wait logic says min(prev+1))
    // init -1. j -> 0.
    fireEvent.keyDown(window, { key: 'j' });

    // Item 1 (index 0) should be selected.
    // It's unread, so it should be marked read.
    await waitFor(() => {
      expect(global.fetch).toHaveBeenCalledWith(
        '/api/item/101',
        expect.objectContaining({
          method: 'PUT',
          body: JSON.stringify({ read: true, starred: false }),
          credentials: 'include',
        })
      );
    });

    // Press 'j' again -> index 1 (Item 2)
    fireEvent.keyDown(window, { key: 'j' });

    // Item 2 is already read, so no markRead call expected for it (mocks clear? no).
    // let's check selection class if possible, but testing library doesn't easily check class on div wrapper unless we query it.

    // Press 's' to star Item 2
    fireEvent.keyDown(window, { key: 's' });

    await waitFor(() => {
      expect(global.fetch).toHaveBeenCalledWith(
        '/api/item/102',
        expect.objectContaining({
          method: 'PUT',
          body: JSON.stringify({ read: true, starred: true }),
          credentials: 'include', // toggled to true
        })
      );
    });
  });

  it('marks items as read when scrolled past', async () => {
    const mockItems = [{ _id: 101, title: 'Item 1', url: 'u1', read: false, starred: false }];
    (global.fetch as any).mockResolvedValue({
      ok: true,
      json: async () => mockItems,
    });

    // Capture both callbacks
    const observerCallbacks: IntersectionObserverCallback[] = [];

    // Override the mock to capture both callbacks
    class MockIntersectionObserver {
      constructor(callback: IntersectionObserverCallback) {
        observerCallbacks.push(callback);
      }
      observe = vi.fn();
      unobserve = vi.fn();
      disconnect = vi.fn();
    }
    window.IntersectionObserver = MockIntersectionObserver as any;

    render(
      <MemoryRouter>
        <FeedItems />
      </MemoryRouter>
    );

    await waitFor(() => {
      expect(screen.getByText('Item 1')).toBeVisible();
    });

    // Wait for observers to be created
    await waitFor(() => {
      expect(observerCallbacks.length).toBeGreaterThan(0);
    });

    // Simulate item leaving viewport at the top
    // Element index is 0
    const entry = {
      isIntersecting: false,
      boundingClientRect: { top: -50 } as DOMRectReadOnly,
      target: { getAttribute: () => '0' } as unknown as Element,
      intersectionRatio: 0,
      time: 0,
      rootBounds: null,
      intersectionRect: {} as DOMRectReadOnly,
    } as IntersectionObserverEntry;

    // Call the last itemObserver (second-to-last in the array, since sentinelObserver is last)
    act(() => {
      const lastItemObserver = observerCallbacks[observerCallbacks.length - 2];
      lastItemObserver([entry], {} as IntersectionObserver);
    });

    await waitFor(() => {
      expect(global.fetch).toHaveBeenCalledWith(
        '/api/item/101',
        expect.objectContaining({
          method: 'PUT',
          body: JSON.stringify({ read: true, starred: false }),
        })
      );
    });
  });

  it('loads more items when sentinel becomes visible', async () => {
    const initialItems = [{ _id: 101, title: 'Item 1', url: 'u1', read: true, starred: false }];
    const moreItems = [{ _id: 100, title: 'Item 0', url: 'u0', read: true, starred: false }];

    (global.fetch as any)
      .mockResolvedValueOnce({ ok: true, json: async () => initialItems })
      .mockResolvedValueOnce({ ok: true, json: async () => moreItems });

    const observerCallbacks: IntersectionObserverCallback[] = [];
    class MockIntersectionObserver {
      constructor(callback: IntersectionObserverCallback) {
        observerCallbacks.push(callback);
      }
      observe = vi.fn();
      unobserve = vi.fn();
      disconnect = vi.fn();
    }
    window.IntersectionObserver = MockIntersectionObserver as any;

    render(
      <MemoryRouter>
        <FeedItems />
      </MemoryRouter>
    );

    await waitFor(() => {
      expect(screen.getByText('Item 1')).toBeInTheDocument();
    });

    // Wait for observers to be created (effect runs multiple times)
    await waitFor(() => {
      expect(observerCallbacks.length).toBeGreaterThan(0);
    });

    // Simulate sentinel becoming visible
    const entry = {
      isIntersecting: true,
      target: { id: 'load-more-sentinel' } as unknown as Element,
      boundingClientRect: {} as DOMRectReadOnly,
      intersectionRatio: 1,
      time: 0,
      rootBounds: null,
      intersectionRect: {} as DOMRectReadOnly,
    } as IntersectionObserverEntry;

    // Call the last sentinelObserver (second of the last pair created)
    act(() => {
      const lastSentinelObserver = observerCallbacks[observerCallbacks.length - 1];
      lastSentinelObserver([entry], {} as IntersectionObserver);
    });

    await waitFor(() => {
      expect(screen.getByText('Item 0')).toBeInTheDocument();
      const params = new URLSearchParams();
      params.append('max_id', '101');
      params.append('read_filter', 'unread');
      expect(global.fetch).toHaveBeenCalledWith(`/api/stream?${params.toString()}`, expect.anything());
    });
  });
});