defmodule Sutra.Cardano.Address.Parser do
  @moduledoc """
    Contains function to encode and decode Cardano addresses based on cip-0019
    https://cips.cardano.org/cip/CIP-0019

  """

  import Bitwise, only: [band: 2, bor: 2, <<<: 2, &&&: 2, >>>: 2]

  alias Sutra.Cardano.Address
  alias Sutra.Cardano.Address.Credential
  alias Sutra.Cardano.Address.Parser
  alias Sutra.Cardano.Address.Pointer

  defimpl CBOR.Encoder, for: Address do
    @impl true
    def encode_into(address, _acc) do
      Parser.encode(address)
    end
  end

  @doc """
  Encode an [Address] to CBOR.

  Byron addresses are not supported

  Shelley address description from CIP-0019:

    Header type (tttt....)  Payment Part     Delegation Part
    (0) 0000....            PaymentKeyHash   StakeKeyHash
    (1) 0001....            ScriptHash       StakeKeyHash
    (2) 0010....            PaymentKeyHash   ScriptHash
    (3) 0011....            ScriptHash       ScriptHash
    (4) 0100....            PaymentKeyHash   Pointer
    (5) 0101....            ScriptHash       Pointer
    (6) 0110....            PaymentKeyHash   ø
    (7) 0111....            ScriptHash       ø

    Header type (....tttt)
    (0) ....0000 testnet
    (1) ....0001 mainnet

  For example, `61....(56 chars / 28 bytes)....` is an enterprise address (6, only a payment key) on mainnet (1).

  Stake address description from CIP-0019:

    Header type (tttt....)  Stake Reference
    (14) 1110....           StakeKeyHash
    (15) 1111....           ScriptHash


  """
  @spec encode(Address.t()) :: binary()
  def encode(%Address{} = address) do
    network = if address.network == :mainnet, do: "1", else: "0"

    {header_type, payload} =
      do_encode_address(
        address.address_type,
        address.payment_credential,
        address.stake_credential
      )

    (header_type <> network <> payload) |> Base.decode16!(case: :lower)
  end

  defp do_encode_address(:shelley, payment_credential, stake_credential) do
    case {payment_credential, stake_credential} do
      # (0) 0000.... PaymentKeyHash StakeKeyHash
      {%Credential{credential_type: :vkey} = p_cred, %Credential{credential_type: :vkey} = s_cred} ->
        {"0", p_cred.hash <> s_cred.hash}

      # (1) 0001.... ScriptHash StakeKeyHash
      {%Credential{credential_type: :script} = p_cred,
       %Credential{credential_type: :vkey} = s_cred} ->
        {"1", p_cred.hash <> s_cred.hash}

      # (2) 0010.... PaymentKeyHash ScriptHash
      {%Credential{credential_type: :vkey} = p_cred,
       %Credential{credential_type: :script} = s_cred} ->
        {"2", p_cred.hash <> s_cred.hash}

      # (3) 0011.... ScriptHash ScriptHash
      {%Credential{credential_type: :script} = p_cred,
       %Credential{credential_type: :script} = s_cred} ->
        {"3", p_cred.hash <> s_cred.hash}

      # (4) 0100.... PaymentKeyHash Pointer
      {%Credential{credential_type: :vkey} = p_cred, %Pointer{} = pointer} ->
        pointer_val =
          encode_variable_length(pointer.slot) <>
            encode_variable_length(pointer.tx_index) <> encode_variable_length(pointer.cert_index)

        {"4", p_cred.hash <> Base.encode16(pointer_val, case: :lower)}

      # (5) 0101.... ScriptHash Pointer
      {%Credential{credential_type: :script} = p_cred, %Pointer{} = pointer} ->
        pointer_val =
          encode_variable_length(pointer.slot) <>
            encode_variable_length(pointer.tx_index) <> encode_variable_length(pointer.cert_index)

        {"5", p_cred.hash <> Base.encode16(pointer_val, case: :lower)}

      # (6) 0110.... PaymentKeyHash  ø
      {%Credential{credential_type: :vkey} = p_cred, nil} ->
        {"6", p_cred.hash}

      # (7) 0111.... ScriptHash  ø
      {%Credential{credential_type: :script} = p_cred, nil} ->
        {"7", p_cred.hash}
    end
  end

  defp do_encode_address(:reward, nil, %Credential{} = stake_cred) do
    case stake_cred.credential_type do
      # (14) 1110.... StakeKeyHash
      :vkey -> {"e", stake_cred.hash}
      # (15) 1111.... ScriptHash
      :script -> {"f", stake_cred.hash}
    end
  end

  @spec decode(binary()) :: Address.t()
  def decode(bytes) do
    <<t1::1, t2::1, t3::1, t4::1, n1::1, n2::1, n3::1, n4::1, rest::bitstring>> = bytes
    address_header = [t1, t2, t3, t4]
    decoded_address = do_decode_bytes(address_header, rest)

    %Address{
      network: get_network([n1, n2, n3, n4]),
      address_type: decoded_address.address_type,
      payment_credential: decoded_address.payment_credential,
      stake_credential: decoded_address.stake_credential
    }
  end

  # (0) ....0000 testnet
  defp get_network([0, 0, 0, 0]), do: :testnet
  # (1) ....0001 mainnet
  defp get_network([0, 0, 0, 1]), do: :mainnet

  # (0) 0000.... PaymentKeyHash StakeKeyHash
  defp do_decode_bytes([0, 0, 0, 0], bytes) do
    %{
      payment_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      stake_credential: %Credential{
        hash: binary_slice(bytes, 28, 28) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      address_type: :shelley
    }
  end

  # (1) 0001.... ScriptHash StakeKeyHash
  defp do_decode_bytes([0, 0, 0, 1], bytes) do
    %{
      payment_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      stake_credential: %Credential{
        hash: binary_slice(bytes, 28, 28) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      address_type: :shelley
    }
  end

  # (2) 0010.... PaymentKeyHash ScriptHash
  defp do_decode_bytes([0, 0, 1, 0], bytes) do
    %{
      payment_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      stake_credential: %Credential{
        hash: binary_slice(bytes, 28, 28) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      address_type: :shelley
    }
  end

  # (3) 0011.... ScriptHash ScriptHash
  defp do_decode_bytes([0, 0, 1, 1], bytes) do
    %{
      payment_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      stake_credential: %Credential{
        hash: binary_slice(bytes, 28, 28) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      address_type: :shelley
    }
  end

  # (4) 0100.... PaymentKeyHash Pointer
  defp do_decode_bytes([0, 1, 0, 0], bytes) do
    bytes_list = :binary.bin_to_list(bytes)
    {payment, pointer_bytes} = Enum.split(bytes_list, 28)

    {slot, remaining} = decode_variable_length(pointer_bytes)
    {index, remaining} = decode_variable_length(remaining)
    {cert_index, _} = decode_variable_length(remaining)

    %{
      payment_credential: %Credential{
        hash: :binary.list_to_bin(payment) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      stake_credential: %Pointer{slot: slot, tx_index: index, cert_index: cert_index},
      address_type: :shelley
    }
  end

  # (5) 0101.... ScriptHash Pointer
  defp do_decode_bytes([0, 1, 0, 1], bytes) do
    bytes_list = :binary.bin_to_list(bytes)
    {payment, pointer_bytes} = Enum.split(bytes_list, 28)

    {slot, remaining} = decode_variable_length(pointer_bytes)
    {index, remaining} = decode_variable_length(remaining)
    {cert_index, _} = decode_variable_length(remaining)

    %{
      payment_credential: %Credential{
        hash: :binary.list_to_bin(payment) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      stake_credential: %Pointer{slot: slot, tx_index: index, cert_index: cert_index},
      address_type: :shelley
    }
  end

  # (6) 0110.... PaymentKeyHash  ø
  defp do_decode_bytes([0, 1, 1, 0], bytes) do
    %{
      payment_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      stake_credential: nil,
      address_type: :shelley
    }
  end

  # (7) 0111.... ScriptHash  ø
  defp do_decode_bytes([0, 1, 1, 1], bytes) do
    %{
      payment_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      stake_credential: nil,
      address_type: :shelley
    }
  end

  # (8) 1000.... Byron
  defp do_decode_bytes([1, 0, 0, 0], _bytes) do
    raise "Not implemented: Byron Address"
  end

  # (9) 1110.... StakeKeyHash
  defp do_decode_bytes([1, 1, 1, 0], bytes) do
    %{
      payment_credential: nil,
      stake_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :vkey
      },
      address_type: :reward
    }
  end

  # (10) 1111.... ScriptHash
  defp do_decode_bytes([1, 1, 1, 1], bytes) do
    %{
      payment_credential: nil,
      stake_credential: %Credential{
        hash: binary_slice(bytes, 0, 28) |> Base.encode16(case: :lower),
        credential_type: :script
      },
      address_type: :reward
    }
  end

  defp do_decode_bytes(_, _), do: raise("Invalid address type")

  defp decode_variable_length(bytes) do
    Enum.reduce_while(bytes, {0, bytes}, fn byte, {val, [_ | t]} ->
      new_val = bor(val <<< 7, band(byte, 127))

      if band(byte, 128) == 0 do
        {:halt, {new_val, t}}
      else
        {:cont, {new_val, t}}
      end
    end)
  end

  defp encode_variable_length(val) when val >= 0 do
    bit_length = Integer.to_string(val, 2) |> String.length()

    {_, _, buff} =
      Enum.reduce_while(0..bit_length, {bit_length, val >>> 7, [val &&& 127]}, fn _,
                                                                                  {l, v, buff} ->
        if l > 7 do
          new_val = v >>> 7
          new_buff_val = (v &&& 127) + 128
          {:cont, {l - 7, new_val, [new_buff_val | buff]}}
        else
          {:halt, {l, v, buff}}
        end
      end)

    :binary.list_to_bin(buff)
  end
end