defmodule Forge.Crypto do
  @moduledoc """
  Crypto related functions
  """

  @doc """
  Generate an Ethereum compatible sha3

    iex> Forge.Crypto.sha3("hello")
    <<28, 138, 255, 149, 6, 133, 194, 237, 75, 195, 23, 79, 52, 114, 40, 123, 86, 217, 81, 123, 156, 148, 129, 39, 49, 154, 9, 167, 163, 109, 234, 200>>

    iex> Forge.Crypto.sha3("hello", :upper)
    "1C8AFF950685C2ED4BC3174F3472287B56D9517B9C948127319A09A7A36DEAC8"

    iex> Forge.Crypto.sha3("hello", :lower)
    "1c8aff950685c2ed4bc3174f3472287b56d9517b9c948127319a09a7a36deac8"
  """
  @spec sha3(binary) :: binary
  def sha3(data), do: :keccakf1600.hash(:sha3_256, data)

  @spec sha3(binary, :upper | :lower) :: binary
  def sha3(data, :upper), do: data |> sha3() |> Base.encode16()
  def sha3(data, :lower), do: data |> sha3() |> Base.encode16(case: :lower)

  @doc """
  Sign data with private key
  """
  @spec ecdsa_sign!(binary, binary) :: binary
  def ecdsa_sign!(data, <<encoded_private_key::binary-size(64)>>) do
    ecdsa_sign!(data, Base.decode16!(encoded_private_key))
  end

  def ecdsa_sign!(data, <<private_key::binary-size(32)>>) do
    {:ok, signature} = :libsecp256k1.ecdsa_sign(data, private_key, :default, <<>>)
    signature
  end

  @doc """
  Verify signature with public key
  """
  @spec ecdsa_verify(binary, binary, binary) :: :ok | :error
  def ecdsa_verify(data, signature, <<encoded_public_key::binary-size(130)>>) do
    ecdsa_verify(data, signature, Base.decode16!(encoded_public_key))
  end

  def ecdsa_verify(data, signature, <<4::size(8), _::binary-size(64)>> = public_key) do
    :libsecp256k1.ecdsa_verify(data, signature, public_key)
  end

  @doc """
  Create a random private key
  """
  @spec create_private_key :: String.t()
  def create_private_key, do: :crypto.strong_rand_bytes(32)

  @doc """
  Create a public key based on private key
  """
  @spec create_public_key(String.t()) :: String.t()
  def create_public_key(<<encoded_private_key::binary-size(64)>>) do
    encoded_private_key |> Base.decode16!() |> create_public_key()
  end

  def create_public_key(private_key) do
    {:ok, public_key} = :libsecp256k1.ec_pubkey_create(private_key, :uncompressed)
    public_key
  end

  @doc """
  Create wallet address based on public key
  """
  @spec create_wallet_address(String.t()) :: String.t()
  def create_wallet_address(<<encoded_public_key::binary-size(130)>>) do
    encoded_public_key |> Base.decode16!() |> create_wallet_address()
  end

  def create_wallet_address(public_key) do
    <<4::size(8), key::binary-size(64)>> = public_key
    <<_::binary-size(12), address::binary-size(20)>> = sha3(key)
    Base.encode16(address, case: :lower)
  end

  @doc """
  Generate a tendermint tx hash based on tx data

    iex> Forge.Crypto.get_tx_hash("hello")
    "2CF24DBA5FB0A30E26E83B2AC5B9E29E1B161E5C"
  """
  @spec get_tx_hash(String.t()) :: String.t()
  def get_tx_hash(data) do
    <<hash::binary-size(20), _::binary>> = :crypto.hash(:sha256, data)
    Base.encode16(hash)
  end
end