function bufferToHex (buffer: ArrayBuffer): string {
  const bytes = new Uint8Array(buffer)
  let hex = ''
  for (let i = 0; i < bytes.length; i++) {
    hex += bytes[i].toString(16).padStart(2, '0')
  }
  return hex
}

export async function sha256 (str: string): Promise<string> {
  const data = new TextEncoder().encode(str)
  const digest = await crypto.subtle.digest('SHA-256', data)
  return bufferToHex(digest)
}

export async function hmacSha256 (str: string, key: string): Promise<string> {
  const encoder = new TextEncoder()
  const cryptoKey = await crypto.subtle.importKey(
    'raw',
    encoder.encode(key),
    { name: 'HMAC', hash: 'SHA-256' },
    false,
    ['sign']
  )
  const signature = await crypto.subtle.sign('HMAC', cryptoKey, encoder.encode(str))
  return bufferToHex(signature)
}