import * as jose from "jose"

export function hashCode(s: string) {
  let h = 0
  const l = s.length
  let i = 0
  if (l > 0) while (i < l) h = ((h << 5) + h + s.charCodeAt(i++)) | 0
  return h
}

export const ephemeralCode = async (length: number, secret: string) => {
  const code: number[] = []
  while (code.length < length) {
    const buffer = crypto.getRandomValues(new Uint8Array(length * 2))
    for (const byte of buffer) {
      if (byte < 250 && code.length < length) {
        code.push(byte % 10)
      }
    }
  }
  const codeStr = code.join("")
  const iterations = 600000
  const encoder = new TextEncoder()
  const bytes = encoder.encode(codeStr)
  const salt = encoder.encode(secret)
  const keyMaterial = await crypto.subtle.importKey(
    "raw",
    bytes,
    "PBKDF2",
    false,
    ["deriveBits"],
  )
  const hash = await crypto.subtle.deriveBits(
    {
      name: "PBKDF2",
      hash: "SHA-256",
      salt: salt,
      iterations,
    },
    keyMaterial,
    256,
  )
  const hashB64 = jose.base64url.encode(new Uint8Array(hash))
  return {
    hash: hashB64,
    code: codeStr,
  }
}

export const verifyEphemeralCode = async (
  code: string,
  hashB64: string,
  secret: string,
) => {
  const encoder = new TextEncoder()
  const codeBytes = encoder.encode(code)
  const salt = encoder.encode(secret)
  const params = {
    name: "PBKDF2",
    hash: "SHA-256",
    salt,
    iterations: 600000,
  }
  const keyMaterial = await crypto.subtle.importKey(
    "raw",
    codeBytes,
    "PBKDF2",
    false,
    ["deriveBits"],
  )
  const hash = await crypto.subtle.deriveBits(params, keyMaterial, 256)
  const hashBase64 = jose.base64url.encode(new Uint8Array(hash))
  return hashBase64 === hashB64
}