defmodule JSONRPC2.Spec.Request do
  @moduledoc """
  Struct which represents JSONRPC request.
  """

  alias JSONRPC2.Spec

  @type t :: %__MODULE__{
    id: Spec.id(),
    method: Spec.method(),
    params: Spec.params(),
    jsonrpc: String.t()
  }

  @derive JSON.Encoder

  defstruct [:id, :method, :params, jsonrpc: "2.0"]

  defguard is_id(value) when is_integer(value) or is_binary(value) or is_nil(value)
  defguard is_params(value) when is_map(value) or is_list(value)

  @doc """
  Build a request struct from input data

  Example:

      iex> Request.parse(%{"id" => 123, "method" => "add", "params" => %{"x" => 15, "y" => 51}, "jsonrpc" => "2.0"})
      {:ok, %Request{id: 123, method: "add", params: %{"x" => 15, "y" => 51}, jsonrpc: "2.0"}}

      iex> Request.parse(%{"id" => nil, "method" => "add", "params" => %{"x" => 15, "y" => 51}, "jsonrpc" => "2.0"})
      {:ok, %Request{id: nil, method: "add", params: %{"x" => 15, "y" => 51}, jsonrpc: "2.0"}}

      iex> Request.parse(%{"id" => 123, "method" => "add", "params" => %{"x" => 15, "y" => 51}})
      {:invalid, 123}

      iex> Request.parse(%{"method" => "add", "params" => %{"x" => 15, "y" => 51}, "jsonrpc" => "2.0"})
      {:invalid, nil}
  """
  def parse(%{"id" => id, "method" => method, "params" => params, "jsonrpc" => "2.0"}) do
    init(method, params, id)
  end

  def parse(%{"id" => id}) do
    {:invalid, id}
  end

  def parse(_) do
    {:invalid, nil}
  end

  @doc """
  Validate a request struct
  """
  @spec valid?(t()) :: :ok | :invalid
  def valid?(%__MODULE__{id: _, method: method, params: params}) do
    if(is_binary(method) && is_params(params), do: :ok, else: :invalid)
  end

  @doc """
  Instantiate a request struct
  """
  @spec new(Spec.method(), Spec.params(), Spec.id()) :: t()
  def new(method, params, id) do
    %__MODULE__{id: id, method: method, params: params}
  end

  defp init(method, params, id) when is_binary(method) and is_params(params) and is_id(id) do
    {:ok, new(method, params, id)}
  end

  defp init(_method, _params, id) do
    {:invalid, id}
  end
end