defmodule ExecutionPlane.Protocols.JsonRpc.Adapter do
  @moduledoc """
  Execution Plane-owned JSON-RPC framing adapter for persistent lanes.

  Family kits keep protocol-session orchestration and provider semantics above
  this adapter while the canonical request/response framing and correlation live
  below them.
  """

  defstruct next_id: 0,
            ready_matcher: nil

  @type t :: %__MODULE__{
          next_id: non_neg_integer(),
          ready_matcher: (map() -> boolean()) | nil
        }

  @spec init(keyword()) :: {:ok, t(), [binary()]}
  def init(opts) when is_list(opts) do
    {:ok,
     %__MODULE__{
       next_id: Keyword.get(opts, :request_id_start, 0),
       ready_matcher: Keyword.get(opts, :ready_matcher)
     }, []}
  end

  @spec encode_once(term()) :: binary()
  def encode_once(request) do
    {:ok, _id, frame, _state} = encode_request(request, %__MODULE__{})
    frame
  end

  @spec encode_request(term(), t()) ::
          {:ok, term(), binary(), t()} | {:error, term()}
  def encode_request(request, %__MODULE__{} = state) do
    with {:ok, id, message} <- normalize_request(request, state.next_id) do
      next_id = if is_integer(id), do: max(state.next_id, id + 1), else: state.next_id
      frame = [Jason.encode_to_iodata!(message), "\n"] |> IO.iodata_to_binary()
      {:ok, id, frame, %{state | next_id: next_id}}
    end
  end

  @spec encode_notification(term(), t()) ::
          {:ok, binary(), t()} | {:error, term()}
  def encode_notification(notification, %__MODULE__{} = state) do
    with {:ok, message} <- normalize_notification(notification) do
      frame = [Jason.encode_to_iodata!(message), "\n"] |> IO.iodata_to_binary()
      {:ok, frame, state}
    end
  end

  @spec handle_inbound(binary(), t()) :: {:ok, [term()], t()}
  def handle_inbound(frame, %__MODULE__{} = state) when is_binary(frame) do
    case Jason.decode(frame) do
      {:ok, %{} = message} ->
        events =
          []
          |> maybe_add_ready_event(message, state.ready_matcher)
          |> Kernel.++([classify_message(message)])
          |> Enum.reject(&(&1 == :ignore))

        {:ok, events, state}

      {:ok, other} ->
        {:ok, [{:protocol_error, {:invalid_json_rpc_message, other}}], state}

      {:error, error} ->
        {:ok, [{:protocol_error, {:invalid_json, Exception.message(error)}}], state}
    end
  end

  @spec encode_peer_reply(term(), {:ok, term()} | {:error, term()}, t()) :: {:ok, binary(), t()}
  def encode_peer_reply(correlation_key, {:ok, result}, %__MODULE__{} = state) do
    frame =
      %{"id" => correlation_key, "result" => result}
      |> Jason.encode_to_iodata!()
      |> then(&IO.iodata_to_binary([&1, "\n"]))

    {:ok, frame, state}
  end

  def encode_peer_reply(correlation_key, {:error, reason}, %__MODULE__{} = state) do
    frame =
      %{"id" => correlation_key, "error" => normalize_error(reason)}
      |> Jason.encode_to_iodata!()
      |> then(&IO.iodata_to_binary([&1, "\n"]))

    {:ok, frame, state}
  end

  defp normalize_request(%{} = request, next_id) do
    method = Map.get(request, :method) || Map.get(request, "method")
    params = Map.get(request, :params) || Map.get(request, "params")
    id = Map.get(request, :id) || Map.get(request, "id") || next_id

    if is_binary(method) do
      base =
        request
        |> Map.new(fn {key, value} -> {to_string(key), value} end)
        |> Map.put("id", id)
        |> Map.put("method", method)

      {:ok, id, put_optional(base, "params", params)}
    else
      {:error, {:invalid_request, request}}
    end
  end

  defp normalize_request({method, params}, next_id) when is_binary(method) do
    {:ok, next_id, put_optional(%{"id" => next_id, "method" => method}, "params", params)}
  end

  defp normalize_request(method, next_id) when is_binary(method) do
    {:ok, next_id, %{"id" => next_id, "method" => method}}
  end

  defp normalize_request(other, _next_id), do: {:error, {:invalid_request, other}}

  defp normalize_notification(%{} = notification) do
    method = Map.get(notification, :method) || Map.get(notification, "method")
    params = Map.get(notification, :params) || Map.get(notification, "params")

    if is_binary(method) do
      base =
        notification
        |> Map.new(fn {key, value} -> {to_string(key), value} end)
        |> Map.put("method", method)

      {:ok, put_optional(base, "params", params)}
    else
      {:error, {:invalid_notification, notification}}
    end
  end

  defp normalize_notification({method, params}) when is_binary(method) do
    {:ok, put_optional(%{"method" => method}, "params", params)}
  end

  defp normalize_notification(method) when is_binary(method) do
    {:ok, %{"method" => method}}
  end

  defp normalize_notification(other), do: {:error, {:invalid_notification, other}}

  defp classify_message(%{"id" => id, "method" => _method} = message),
    do: {:peer_request, id, message}

  defp classify_message(%{"id" => id, "result" => result}),
    do: {:response, id, {:ok, result}}

  defp classify_message(%{"id" => id, "error" => error}),
    do: {:response, id, {:error, error}}

  defp classify_message(%{"method" => _method} = message), do: {:notification, message}
  defp classify_message(_message), do: :ignore

  defp maybe_add_ready_event(events, _message, nil), do: events

  defp maybe_add_ready_event(events, message, ready_matcher) when is_function(ready_matcher, 1) do
    if ready_matcher.(message) do
      [{:ready, message} | events]
    else
      events
    end
  end

  defp normalize_error(%{"code" => code, "message" => message} = error)
       when is_integer(code) and is_binary(message),
       do: error

  defp normalize_error(%{code: code, message: message} = error)
       when is_integer(code) and is_binary(message) do
    error
    |> Map.new(fn {key, value} -> {to_string(key), value} end)
    |> put_optional("data", Map.get(error, :data))
  end

  defp normalize_error({code, message}) when is_integer(code) and is_binary(message) do
    %{"code" => code, "message" => message}
  end

  defp normalize_error({code, message, data}) when is_integer(code) and is_binary(message) do
    %{"code" => code, "message" => message, "data" => data}
  end

  defp normalize_error(:timeout) do
    %{"code" => -32_000, "message" => "peer request handler timed out"}
  end

  defp normalize_error({:handler_exit, reason}) do
    %{"code" => -32_000, "message" => "peer request handler exited", "data" => inspect(reason)}
  end

  defp normalize_error({:handler_start_failed, reason}) do
    %{
      "code" => -32_000,
      "message" => "peer request handler failed to start",
      "data" => inspect(reason)
    }
  end

  defp normalize_error(:unsupported_peer_request) do
    %{"code" => -32_601, "message" => "unsupported peer request"}
  end

  defp normalize_error(reason) when is_binary(reason) do
    %{"code" => -32_000, "message" => reason}
  end

  defp normalize_error(reason) when is_atom(reason) do
    %{"code" => -32_000, "message" => Atom.to_string(reason)}
  end

  defp normalize_error(reason) do
    %{"code" => -32_000, "message" => inspect(reason)}
  end

  defp put_optional(map, _key, nil), do: map
  defp put_optional(map, _key, []), do: map
  defp put_optional(map, key, value), do: Map.put(map, key, value)
end