defmodule SyntropyWeb.Api.AgentController do
  use SyntropyWeb, :controller

  alias Syntropy.{ClusterInventory, EventRecorder, LatticeSupervisor, TaskScheduler}
  alias SyntropyWeb.Api.{AgentJSON, AgentRequest, ControllerHelpers, Listing}

  @spec index(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def index(conn, params) do
    case Listing.parse_opts(params, [:q, :perspective]) do
      {:ok, opts} ->
        agents = Listing.filter_agents(ClusterInventory.cluster_agents(), opts)
        limit = Keyword.fetch!(opts, :limit)

        json(conn, %{
          data: agents |> Enum.take(limit) |> Enum.map(&AgentJSON.agent/1),
          meta: %{has_more: length(agents) > limit, next_cursor: nil}
        })

      {:error, :invalid_cursor} ->
        ControllerHelpers.invalid_request(conn, "Invalid cursor.", [])
    end
  end

  @spec show(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def show(conn, %{"id" => agent_id}) do
    case ClusterInventory.find_agent(agent_id) do
      nil -> ControllerHelpers.not_found(conn, "Agent", agent_id)
      agent -> json(conn, %{data: AgentJSON.agent(agent)})
    end
  end

  @spec create(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def create(conn, params) do
    with {:ok, request} <- AgentRequest.parse(params),
         {:ok, agent_id} <-
           LatticeSupervisor.add_agent(request.name, request.perspective, request.opts) do
      agent = LatticeSupervisor.get_agent(agent_id)

      EventRecorder.record("agent_created", %{
        agent_id: agent.id,
        runtime_id: agent.runtime_id,
        node_id: agent.node_id,
        agent_name: agent.name,
        perspective: agent.perspective,
        source: "api"
      })

      conn
      |> put_status(:created)
      |> json(%{data: AgentJSON.agent(agent)})
    else
      {:error, errors} when is_list(errors) ->
        ControllerHelpers.invalid_request(conn, "Invalid agent request.", errors)

      {:error, {:already_started, _pid}} ->
        ControllerHelpers.conflict(
          conn,
          "agent_exists",
          "An agent with this id is already running."
        )

      {:error, _reason} ->
        ControllerHelpers.conflict(conn, "agent_not_started", "The agent could not be started.")
    end
  end

  @spec delete(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def delete(conn, %{"id" => agent_id}) do
    case LatticeSupervisor.get_agent(agent_id) do
      nil ->
        ControllerHelpers.not_found(conn, "Agent", agent_id)

      agent ->
        if agent.runtime_id in TaskScheduler.active_agent_ids() do
          ControllerHelpers.conflict(
            conn,
            "agent_busy",
            "Agent #{agent_id} is executing an active run and cannot be removed."
          )
        else
          remove_agent(conn, agent)
        end
    end
  end

  defp remove_agent(conn, agent) do
    case LatticeSupervisor.remove_agent(agent.id) do
      :ok ->
        EventRecorder.record("agent_removed", %{
          agent_id: agent.id,
          runtime_id: agent.runtime_id,
          node_id: agent.node_id,
          agent_name: agent.name,
          perspective: agent.perspective,
          source: "api"
        })

        json(conn, %{data: %{id: agent.id, removed: true}})

      {:error, :not_found} ->
        ControllerHelpers.not_found(conn, "Agent", agent.id)
    end
  end
end