export type BitDepth = 8 | 16 | 24

export interface ExportOptions {
  sampleRate: number
  bitDepth?: BitDepth
}

function encodeWAV(samples: Float32Array, sampleRate: number, bitDepth: BitDepth): Blob {
  const numChannels = 1
  const bytesPerSample = bitDepth / 8
  const blockAlign = numChannels * bytesPerSample
  const byteRate = sampleRate * blockAlign
  const dataSize = samples.length * bytesPerSample
  const bufferSize = 44 + dataSize

  const buffer = new ArrayBuffer(bufferSize)
  const view = new DataView(buffer)

  const writeString = (offset: number, string: string) => {
    for (let i = 0; i < string.length; i++) {
      view.setUint8(offset + i, string.charCodeAt(i))
    }
  }

  writeString(0, 'RIFF')
  view.setUint32(4, 36 + dataSize, true)
  writeString(8, 'WAVE')
  writeString(12, 'fmt ')
  view.setUint32(16, 16, true)
  view.setUint16(20, 1, true)
  view.setUint16(22, numChannels, true)
  view.setUint32(24, sampleRate, true)
  view.setUint32(28, byteRate, true)
  view.setUint16(32, blockAlign, true)
  view.setUint16(34, bitDepth, true)
  writeString(36, 'data')
  view.setUint32(40, dataSize, true)

  const maxValue = Math.pow(2, bitDepth - 1) - 1
  let offset = 44

  for (let i = 0; i < samples.length; i++) {
    const sample = Math.max(-1, Math.min(1, samples[i]))
    const intSample = Math.round(sample * maxValue)

    if (bitDepth === 8) {
      view.setUint8(offset, intSample + 128)
      offset += 1
    } else if (bitDepth === 16) {
      view.setInt16(offset, intSample, true)
      offset += 2
    } else if (bitDepth === 24) {
      const bytes = [
        intSample & 0xff,
        (intSample >> 8) & 0xff,
        (intSample >> 16) & 0xff
      ]
      view.setUint8(offset, bytes[0])
      view.setUint8(offset + 1, bytes[1])
      view.setUint8(offset + 2, bytes[2])
      offset += 3
    }
  }

  return new Blob([buffer], { type: 'audio/wav' })
}

export function exportToWav(
  samples: Float32Array,
  options: ExportOptions
): Blob {
  const bitDepth = options.bitDepth || 8
  return encodeWAV(samples, options.sampleRate, bitDepth)
}

export function createDownloadUrl(blob: Blob): string {
  return URL.createObjectURL(blob)
}

export function revokeDownloadUrl(url: string): void {
  URL.revokeObjectURL(url)
}