import { assertEquals } from "@std/assert";
import { struct } from "@hertzg/binstruct/struct";
import { u16le, u32le, s32le } from "@hertzg/binstruct/numeric";

// Define BMP file header structure (little-endian format)
const bmpHeaderCoder = struct({
  signature: u16le(), // "BM" (0x4D42)
  fileSize: u32le(),  // Size of the BMP file in bytes
  reserved1: u16le(), // Reserved field (must be 0)
  reserved2: u16le(), // Reserved field (must be 0)
  dataOffset: u32le(), // Offset to image data
});

// Define DIB header structure (BITMAPINFOHEADER format)
const dibHeaderCoder = struct({
  headerSize: u32le(),     // Size of DIB header (40 bytes for BITMAPINFOHEADER)
  width: s32le(),          // Image width in pixels
  height: s32le(),         // Image height in pixels (positive = bottom-up)
  colorPlanes: u16le(),    // Number of color planes (must be 1)
  bitsPerPixel: u16le(),   // Bits per pixel (1, 4, 8, 16, 24, 32)
  compression: u32le(),     // Compression method (0 = none)
  imageSize: u32le(),      // Size of image data in bytes
  xPixelsPerMeter: s32le(), // Horizontal resolution (pixels per meter)
  yPixelsPerMeter: s32le(), // Vertical resolution (pixels per meter)
  colorsInPalette: u32le(), // Number of colors in palette (0 = 2^n)
  importantColors: u32le(), // Number of important colors (0 = all)
});

// Create sample BMP data
const bmpData = {
  signature: 0x4D42, // "BM"
  fileSize: 54,      // Header size (14 + 40 bytes)
  reserved1: 0,
  reserved2: 0,
  dataOffset: 54,    // Offset to pixel data
};

const buffer = new Uint8Array(100);
const bytesWritten = bmpHeaderCoder.encode(bmpData, buffer);
const [decoded, bytesRead] = bmpHeaderCoder.decode(buffer);
assertEquals(decoded, bmpData);
assertEquals(bytesWritten, bytesRead);