import { describe, expect, it } from "vitest";
import { encodeWav } from "../src/audio/wav";

const str = (b: Uint8Array, off: number, n: number) =>
  String.fromCharCode(...b.subarray(off, off + n));

describe("encodeWav", () => {
  it("writes a well-formed 24-bit mono PCM header by default", () => {
    const b = encodeWav(new Float32Array(10), 96000);
    const v = new DataView(b.buffer);
    expect(b.length).toBe(44 + 30);
    expect(str(b, 0, 4)).toBe("RIFF");
    expect(v.getUint32(4, true)).toBe(b.length - 8);
    expect(str(b, 8, 4)).toBe("WAVE");
    expect(str(b, 12, 4)).toBe("fmt ");
    expect(v.getUint16(20, true)).toBe(1);
    expect(v.getUint16(22, true)).toBe(1);
    expect(v.getUint32(24, true)).toBe(96000);
    expect(v.getUint32(28, true)).toBe(288000);
    expect(v.getUint16(32, true)).toBe(3);
    expect(v.getUint16(34, true)).toBe(24);
    expect(str(b, 36, 4)).toBe("data");
    expect(v.getUint32(40, true)).toBe(30);
  });

  it("quantizes 24-bit samples as the reference simulator does, little-endian two's complement", () => {
    const b = encodeWav([0, 1, -1, 0.5, 2, NaN], 8000, 24);
    const s = (i: number) => {
      const off = 44 + 3 * i;
      let x = b[off] | (b[off + 1] << 8) | (b[off + 2] << 16);
      if (x >= 1 << 23) x -= 1 << 24;
      return x;
    };
    expect(s(0)).toBe(0);
    expect(s(1)).toBe(8388607);
    expect(s(2)).toBe(-8388607);
    expect(s(3)).toBe(4194304);
    expect(s(4)).toBe(8388607);
    expect(s(5)).toBe(0);
  });

  it("still writes 16-bit files when asked", () => {
    const b = encodeWav([0, 1, -1, 0.5, 2, -3, NaN, Infinity], 8000, 16);
    const v = new DataView(b.buffer);
    expect(v.getUint16(34, true)).toBe(16);
    const s = (i: number) => v.getInt16(44 + 2 * i, true);
    expect(s(0)).toBe(0);
    expect(s(1)).toBe(32767);
    expect(s(2)).toBe(-32767);
    expect(s(3)).toBe(16384);
    expect(s(4)).toBe(32767);
    expect(s(5)).toBe(-32767);
    expect(s(6)).toBe(0);
    expect(s(7)).toBe(0);
  });
});