export function filledDataView(bytes) {
  const ab = new ArrayBuffer(bytes.length)
  const dv = new DataView(ab)

  for (let i = 0; i < bytes.length; i++) {
    dv.setInt8(i, bytes[i])
  }

  return dv
}

export function sizedDataView(length) {
  const ab = new ArrayBuffer(length)
  return new DataView(ab)
}

export function expectDataViewEqual(actual, expected) {
  const actualBytes = new Uint8Array(actual.buffer, actual.byteOffset, actual.byteLength)
  const expectedBytes = new Uint8Array(expected.buffer, expected.byteOffset, expected.byteLength)
  const arraysToString = () => {
    return `actual:   [${Array.from(actualBytes).map(byte => '0x' + byte.toString(16)).join(', ')}]\n` +
      `expected: [${Array.from(expectedBytes).map(byte => '0x' + byte.toString(16)).join(', ')}]`
  }

  if (actualBytes.length !== expectedBytes.length) {
    throw new Error(`DataView length mismatch: actual: ${actualBytes.length}, expected: ${expectedBytes.length}\n` + arraysToString())
  }

  for (let i = 0; i < actualBytes.length; i++) {
    if (actualBytes[i] !== expectedBytes[i]) {
      throw new Error(
        `Byte mismatch at offset ${i}: 0x${actualBytes[i].toString(16)} !== 0x${expectedBytes[i].toString(16)}\n` + arraysToString()
      )
    }
  }
}