exw3/lib/exw3.ex

defmodule ExW3 do

  defmodule Contract do
    use Agent
    
    def at(abi, address) do
      { :ok, pid } = Agent.start_link(fn -> %{abi: abi, address: address} end)
      pid
    end

    def get(contract, key) do
      Agent.get(contract, &Map.get(&1, key))
    end

    @doc """
    Puts the `value` for the given `key` in the `contract`.
    """
    def put(contract, key, value) do
      Agent.update(contract, &Map.put(&1, key, value))
    end

    def deploy(bin_filename, options) do
      {:ok, bin} = File.read(Path.join(System.cwd(), bin_filename))
      tx = %{
        from: options[:from],
        data: bin,
        gas: options[:gas]
      }
      {:ok, tx_receipt_id} = Ethereumex.HttpClient.eth_send_transaction(tx)
      {:ok, tx_receipt} = Ethereumex.HttpClient.eth_get_transaction_receipt(tx_receipt_id)

      tx_receipt["contractAddress"]
    end

    def method(contract_agent, name, args \\ [], options \\ %{}) do
      if get(contract_agent, :abi)[name]["constant"] do
        data = ExW3.encode_inputs(get(contract_agent, :abi), name, args)
        {:ok, output } = Ethereumex.HttpClient.eth_call(%{
          to: get(contract_agent, :address),
          data: data
        })
        [ :ok ] ++ ExW3.decode_output(get(contract_agent, :abi), name, output) |> List.to_tuple
      else
        Ethereumex.HttpClient.eth_send_transaction(Map.merge(%{
          to: get(contract_agent, :address),
          data: ExW3.encode_inputs(get(contract_agent, :abi), name, args)
        }, options))
      end
    end

  end

  def reformat_abi abi do
    Map.new Enum.map(abi, fn x -> {x["name"], x} end)
  end

  def load_abi file_path do
    file = File.read Path.join(System.cwd, file_path)
    case file do
      {:ok, abi} -> reformat_abi Poison.Parser.parse! abi
      err -> err
    end
  end

  def decode_output abi, name, output do
    {:ok, trim_output} = String.slice(output, 2..String.length(output)) |> Base.decode16(case: :lower)
    output_types = Enum.map abi[name]["outputs"], fn x -> x["type"] end
    output_signature = Enum.join [name, "(", Enum.join(output_types, ")"), ")"]
    ABI.decode(output_signature, trim_output)
  end

  def encode_inputs abi, name, inputs do
    input_types = Enum.map abi[name]["inputs"], fn x -> x["type"] end
    input_signature = Enum.join [name, "(", Enum.join(input_types, ","), ")"]
    ABI.encode(input_signature, inputs) |> Base.encode16(case: :lower)
  end

  def accounts do
    case Ethereumex.HttpClient.eth_accounts do
      {:ok, accounts} -> accounts
      err -> err
    end
  end

  #Converts ethereum hex string to decimal number
  defp to_decimal hex_string do
    hex_string
    |> String.slice(2..-1)
    |> String.to_integer(16)
  end

  def block_number do
    case Ethereumex.HttpClient.eth_block_number do
      {:ok, block_number} -> 
        block_number |> to_decimal
      err -> err
    end
  end

  def balance account do
    case Ethereumex.HttpClient.eth_get_balance(account) do
      {:ok, balance} -> 
        balance |> to_decimal
      err -> err
    end
  end

  defp keys_to_decimal map, keys do
    Map.new(
      Enum.map keys, fn k ->
        { k, Map.get(map, k) |> to_decimal }
      end
    )
  end

  def tx_receipt tx_id do
    case Ethereumex.HttpClient.eth_get_transaction_receipt(tx_id) do
      {:ok, receipt} -> 
        Map.merge receipt, keys_to_decimal(receipt, ["blockNumber", "cumulativeGasUsed", "gasUsed"])
      err -> err
    end
  end

end