export interface MDFPWMMetadata {
  title?: string;
  artist?: string;
  album?: string;
}

function toS1(str: string): Buffer {
  const utf8 = Buffer.from(str, "utf-8");
  const len = utf8.length;
  return Buffer.concat([Buffer.from([len]), utf8]);
}

export function writeMDFPWMv3(
  left: Buffer,
  right: Buffer,
  meta: MDFPWMMetadata = {}
): Buffer {
  if (left.length !== right.length) {
    throw new Error("Left and right DFPWM buffers must be the same length");
  }

  let length = left.byteLength*2;
  const mdfpwm = []
  mdfpwm.push(Buffer.from("MDFPWM\x03", "ascii"));
  mdfpwm.push(Buffer.alloc(4));
  mdfpwm.push(toS1(meta.artist || ""));
  mdfpwm.push(toS1(meta.title || ""));
  mdfpwm.push(toS1(meta.album || ""));
  mdfpwm[1]!.writeUint32LE(length)

  for(let i =0; i < length / 12000; i++) {
    const lStart = i * 6000;
    const rStart = i * 6000;

    const lChunk = left.subarray(lStart, lStart + 6000);
    mdfpwm.push(lChunk);
    if (lChunk.length < 6000) {
        mdfpwm.push(Buffer.alloc(6000 - lChunk.length, 0x55));
    }

    const rChunk = right.subarray(rStart, rStart + 6000);
    mdfpwm.push(rChunk);
    if (rChunk.length < 6000) {
        mdfpwm.push(Buffer.alloc(6000 - rChunk.length, 0x55));
    }
  }

  return Buffer.concat(mdfpwm)
}