import zlib from "node:zlib";

function crc32(buffer) {
  let table = [];
  for (let n = 0; n < 256; n += 1) {
    let c = n;
    for (let k = 0; k < 8; k += 1) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
    table[n] = c >>> 0;
  }
  let crc = 0xffffffff;
  for (const byte of buffer) crc = table[(crc ^ byte) & 0xff] ^ (crc >>> 8);
  return (crc ^ 0xffffffff) >>> 0;
}

function chunk(type, data) {
  const length = Buffer.alloc(4);
  length.writeUInt32BE(data.length);
  const typed = Buffer.concat([Buffer.from(type, "ascii"), data]);
  const crc = Buffer.alloc(4);
  crc.writeUInt32BE(crc32(typed));
  return Buffer.concat([length, typed, crc]);
}

// Mostly flat images so the fixtures compress small; the tests identify slides
// by asset ID rather than by pixels.
export function makePng(width, height, [r, g, b]) {
  const header = Buffer.alloc(13);
  header.writeUInt32BE(width, 0);
  header.writeUInt32BE(height, 4);
  header[8] = 8;
  header[9] = 2;
  const raw = Buffer.alloc(height * (1 + width * 3));
  for (let y = 0; y < height; y += 1) {
    const offset = y * (1 + width * 3);
    raw[offset] = 0;
    for (let x = 0; x < width; x += 1) {
      const p = offset + 1 + x * 3;
      raw[p] = r;
      raw[p + 1] = g;
      raw[p + 2] = x < 64 && y < 64 ? 255 : b;
    }
  }
  return Buffer.concat([
    Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]),
    chunk("IHDR", header),
    chunk("IDAT", zlib.deflateSync(raw, { level: 9 })),
    chunk("IEND", Buffer.alloc(0)),
  ]);
}

export const FIXTURES = [
  { name: "wide-a", width: 1920, height: 1080, rgb: [200, 30, 30] },
  { name: "wide-b", width: 1920, height: 1080, rgb: [30, 200, 30] },
  { name: "wide-c", width: 1280, height: 720, rgb: [30, 30, 200] },
  { name: "wide-d", width: 1920, height: 1080, rgb: [200, 200, 30] },
  { name: "portrait", width: 1080, height: 1920, rgb: [180, 60, 200] },
  { name: "square", width: 1200, height: 1200, rgb: [60, 180, 200] },
  { name: "standalone", width: 1920, height: 1080, rgb: [240, 140, 20] },
];

const API = process.env.DISPLAY_BASE_URL || "http://127.0.0.1:5199";

// Uploads are content-addressed, so re-running the suite reuses the same assets
// instead of piling up duplicates.
export async function ensureFixtures(request) {
  const existing = await (await request.fetch(`${API}/api/assets`)).json();
  const byName = new Map(existing.assets.map((asset) => [asset.displayName, asset]));
  for (const fixture of FIXTURES) {
    if (byName.has(fixture.name)) continue;
    const response = await request.fetch(`${API}/api/assets`, {
      method: "POST",
      multipart: {
        files: {
          name: `${fixture.name}.png`,
          mimeType: "image/png",
          buffer: makePng(fixture.width, fixture.height, fixture.rgb),
        },
      },
    });
    if (!response.ok()) {
      throw new Error(`fixture upload failed: ${response.status()} ${await response.text()}`);
    }
  }
  const refreshed = await (await request.fetch(`${API}/api/assets`)).json();
  return Object.fromEntries(refreshed.assets.map((asset) => [asset.displayName, asset]));
}