import { afterEach, describe, expect, it, vi } from 'vitest';
import { deserialize } from 'bson';
import sharp from 'sharp';
import trace from './trace.js';

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

/** Build a small PNG with an opaque circle in the center on a transparent bg. */
async function makePng(size = 20): Promise<Buffer> {
  const rgba = Buffer.alloc(size * size * 4);
  const cx = size / 2;
  const cy = size / 2;
  const r = size / 3;
  for (let y = 0; y < size; y++) {
    for (let x = 0; x < size; x++) {
      if (Math.hypot(x - cx, y - cy) <= r) {
        const i = (y * size + x) * 4;
        rgba[i] = 255;
        rgba[i + 1] = 255;
        rgba[i + 2] = 255;
        rgba[i + 3] = 255;
      }
    }
  }
  return sharp(rgba, { raw: { width: size, height: size, channels: 4 } })
    .png()
    .toBuffer();
}

function stubFetch(body: Buffer) {
  vi.stubGlobal(
    'fetch',
    vi.fn().mockResolvedValue(
      new Response(new Uint8Array(body), {
        headers: { 'content-type': 'image/png' },
      }),
    ),
  );
}

describe('trace route', () => {
  it('rejects a missing url', async () => {
    const res = await trace.request('/');
    expect(res.status).toBe(400);
    expect(await res.json()).toEqual({ error: 'Required' });
  });

  it('rejects a non-http url', async () => {
    const res = await trace.request('/?url=file%3A%2F%2F%2Fetc%2Fpasswd');
    expect(res.status).toBe(400);
  });

  it('returns 502 when the upstream fetch fails', async () => {
    vi.stubGlobal(
      'fetch',
      vi.fn().mockResolvedValue(new Response('error', { status: 500 })),
    );
    const res = await trace.request('/?url=https%3A%2F%2Fexample.com%2Fa.png');
    expect(res.status).toBe(502);
  });

  it('returns a BSON shape by default', async () => {
    stubFetch(await makePng());
    const res = await trace.request('/?url=https%3A%2F%2Fexample.com%2Fa.png');
    expect(res.status).toBe(200);
    expect(res.headers.get('content-type')).toBe('application/octet-stream');

    const result = deserialize(new Uint8Array(await res.arrayBuffer()));
    expect(result.format).toBe('shape');
    expect(result.mode).toBe('alpha');
    expect(result.width).toBe(20);
    expect(result.height).toBe(20);
    expect(typeof result.svg).toBe('string');
    expect(result.svg).toContain('<svg');
    expect(result.shape).toBeDefined();
    expect(result.shape.outline.length).toBeGreaterThan(3);
  });

  it('returns a raw SVG when format=svg', async () => {
    stubFetch(await makePng());
    const res = await trace.request(
      '/?url=https%3A%2F%2Fexample.com%2Fa.png&format=svg',
    );
    expect(res.status).toBe(200);
    const result = deserialize(new Uint8Array(await res.arrayBuffer()));
    expect(result.format).toBe('svg');
    expect(result.shape).toBeUndefined();
    expect(typeof result.svg).toBe('string');
  });

  it('supports bw mode', async () => {
    stubFetch(await makePng());
    const res = await trace.request(
      '/?url=https%3A%2F%2Fexample.com%2Fa.png&mode=bw',
    );
    expect(res.status).toBe(200);
    const result = deserialize(new Uint8Array(await res.arrayBuffer()));
    expect(result.mode).toBe('bw');
    expect(result.shape.outline.length).toBeGreaterThan(3);
  });

  it('applies an inset offset to the shape', async () => {
    stubFetch(await makePng());
    const res = await trace.request(
      '/?url=https%3A%2F%2Fexample.com%2Fa.png&offset=-2',
    );
    expect(res.status).toBe(200);
    const result = deserialize(new Uint8Array(await res.arrayBuffer()));
    expect(result.offset).toBe(-2);
    expect(result.shape.outline.length).toBeGreaterThan(3);
    // An inset of 2px on a 20px circle must be visibly smaller.
    const extent = (pts: number[][]) => [
      Math.min(...pts.map((p) => p[0]!)),
      Math.max(...pts.map((p) => p[0]!)),
    ];
    const [minX, maxX] = extent(result.shape.outline);
    expect((maxX ?? 0) - (minX ?? 0)).toBeLessThan(20);
  });

  it('applies an outset offset to the shape', async () => {
    stubFetch(await makePng());
    const res = await trace.request(
      '/?url=https%3A%2F%2Fexample.com%2Fa.png&offset=2',
    );
    expect(res.status).toBe(200);
    const result = deserialize(new Uint8Array(await res.arrayBuffer()));
    expect(result.offset).toBe(2);
    expect(result.shape.outline.length).toBeGreaterThan(3);
  });

  it('rejects a non-numeric offset', async () => {
    stubFetch(await makePng());
    const res = await trace.request(
      '/?url=https%3A%2F%2Fexample.com%2Fa.png&offset=abc',
    );
    expect(res.status).toBe(400);
  });

  it('omits offset when not requested', async () => {
    stubFetch(await makePng());
    const res = await trace.request('/?url=https%3A%2F%2Fexample.com%2Fa.png');
    const result = deserialize(new Uint8Array(await res.arrayBuffer()));
    expect(result.offset).toBeUndefined();
  });
});