defmodule EditorDiagnostics do
  @moduledoc """
  This is the EditorDiagnostics Agent. It is the Agent to which you will report
  all of your diagnostics. Once the compile step is complete, the
  EditorDiagnostics Compiler will then collect all diagnostic messages from this
  Agent and shut it down.
  """
  use Agent
  alias Mix.Task.Compiler.Diagnostic

  defp ensure_started() do
    case Agent.start(fn -> [] end, name: {:global, __MODULE__}) do
      {:ok, _} -> :ok
      {:error, {:already_started, _}} -> :ok
      response -> response
    end
  end

  @doc """
  Reports an :error or :warning to be output to the editor.

  ## Examples

      iex> EditorDiagnostics.report(:error, "something went wrong", "some/file.ex", 22)
      :ok

      iex> EditorDiagnostics.report(:error, "something went wrong", "some/file.ex", 22, "my_project")
      :ok

  """
  @spec report(Diagnostic.severity(), String.t(), Path.t(), Diagnostic.position(), String.t()) ::
          :ok
  def report(severity, message, file, position, compiler_name \\ "editor_diagnostics") do
    diagnostic = %Diagnostic{
      compiler_name: compiler_name,
      file: file,
      message: message,
      position: position,
      severity: severity
    }

    :ok = ensure_started()
    Agent.update({:global, __MODULE__}, &[diagnostic | &1])
  end

  @doc """
  Collects a list of the reported errors and shuts down the agent.

  ## Examples

      iex> EditorDiagnostics.collect()
      [{:error, "something went wrong", "some/file.ex", 22}]

  """
  def collect() do
    :ok = ensure_started()
    diagnostics = Agent.get({:global, __MODULE__}, & &1)
    Agent.stop({:global, __MODULE__})
    diagnostics
  end
end