defmodule OrgGarden.Server do
  @moduledoc """
  Manages the serve mode lifecycle.

  This GenServer encapsulates the full serve mode workflow:
  1. Run initial export pipeline
  2. Start supervised Watcher + Quartz under DynamicSupervisor
  3. Handle graceful shutdown on termination

  ## Usage

      # Start the server (blocks until stopped)
      {:ok, pid} = OrgGarden.Server.start_link(
        notes_dir: "/path/to/notes",
        output_dir: "/path/to/output"
      )

      # Stop gracefully
      OrgGarden.Server.stop()
  """

  use GenServer

  require Logger

  alias OrgGarden.Config

  @transforms [OrgGarden.Transforms.Citations]

  # -------------------------------------------------------------------
  # Client API
  # -------------------------------------------------------------------

  @doc """
  Start the serve mode server.

  ## Options

    * `:notes_dir` — path to org-roam notes (required)
    * `:output_dir` — output base directory (required)
    * `:content_dir` — markdown output directory (default: output_dir/content)
    * `:port` — HTTP server port (default: from config)
    * `:ws_port` — WebSocket port (default: from config)
  """
  def start_link(opts) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @doc """
  Stop the server gracefully.
  """
  def stop(timeout \\ 10_000) do
    GenServer.stop(__MODULE__, :normal, timeout)
  end

  @doc """
  Check if the server is running.
  """
  def running? do
    Process.whereis(__MODULE__) != nil
  end

  # -------------------------------------------------------------------
  # GenServer callbacks
  # -------------------------------------------------------------------

  @impl true
  def init(opts) do
    Process.flag(:trap_exit, true)

    notes_dir = Keyword.fetch!(opts, :notes_dir)
    output_dir = Keyword.fetch!(opts, :output_dir)
    content_dir = Keyword.get(opts, :content_dir, Path.join(output_dir, "content"))
    http_port = Keyword.get(opts, :port, Config.get(:http_port, 8080))
    ws_port = Keyword.get(opts, :ws_port, Config.get(:ws_port, 3001))

    pipeline_opts = Config.pipeline_opts()

    state = %{
      notes_dir: notes_dir,
      output_dir: output_dir,
      content_dir: content_dir,
      pipeline_opts: pipeline_opts,
      http_port: http_port,
      ws_port: ws_port,
      supervisor_pid: nil
    }

    # Run initial pipeline synchronously
    :ok = run_initial_pipeline(state)

    # Start supervised components
    case start_supervisor(state) do
      {:ok, sup_pid} ->
        Logger.info("Server started on http://localhost:#{http_port}")
        Logger.info("Watching #{notes_dir} for changes")
        {:ok, %{state | supervisor_pid: sup_pid}}

      {:error, reason} ->
        {:stop, reason}
    end
  end

  @impl true
  def handle_info({:EXIT, pid, reason}, %{supervisor_pid: pid} = state) do
    Logger.error("Supervisor exited: #{inspect(reason)}")
    {:stop, {:supervisor_exit, reason}, state}
  end

  @impl true
  def handle_info({:EXIT, _pid, reason}, state) do
    Logger.warning("Linked process exited: #{inspect(reason)}")
    {:noreply, state}
  end

  @impl true
  def terminate(reason, state) do
    Logger.info("Server shutting down: #{inspect(reason)}")

    if state.supervisor_pid do
      # Stop the supervisor gracefully
      DynamicSupervisor.terminate_child(OrgGarden.DynamicSupervisor, state.supervisor_pid)
    end

    :ok
  end

  # -------------------------------------------------------------------
  # Private functions
  # -------------------------------------------------------------------

  defp run_initial_pipeline(state) do
    %{
      notes_dir: notes_dir,
      output_dir: output_dir,
      content_dir: content_dir,
      pipeline_opts: pipeline_opts
    } = state

    Logger.info("Running initial export pipeline...")

    # Wipe content directory
    wipe(content_dir)

    # Export all org files
    case OrgGarden.Export.export_all(notes_dir, output_dir) do
      {:ok, 0, []} ->
        Logger.warning("No .org files found in #{notes_dir}")
        # Still generate index (will be empty or have default content)
        OrgGarden.Index.generate(content_dir)
        :ok

      {:ok, count, []} ->
        Logger.info("Exported #{count} file(s)")

        # Run transforms
        {:ok, stats} = OrgGarden.run(content_dir, @transforms, pipeline_opts)

        Enum.each(stats, fn {mod, c} ->
          Logger.info("#{inspect(mod)}: #{c} file(s) modified")
        end)

        # Generate index
        OrgGarden.Index.generate(content_dir)
        :ok

      {:ok, count, failures} ->
        Logger.warning("Exported #{count} file(s), #{length(failures)} failed")

        Enum.each(failures, fn {f, {:error, {:emacs_exit, code}}} ->
          Logger.warning("  failed: #{Path.basename(f)} (emacs exit code #{code})")
        end)

        # Continue with transforms and index anyway
        {:ok, stats} = OrgGarden.run(content_dir, @transforms, pipeline_opts)

        Enum.each(stats, fn {mod, c} ->
          Logger.info("#{inspect(mod)}: #{c} file(s) modified")
        end)

        # Generate index
        OrgGarden.Index.generate(content_dir)
        :ok
    end
  end

  defp start_supervisor(state) do
    %{
      notes_dir: notes_dir,
      output_dir: output_dir,
      content_dir: content_dir,
      pipeline_opts: pipeline_opts,
      http_port: http_port,
      ws_port: ws_port
    } = state

    child_spec = {
      OrgGarden.Supervisor,
      [
        notes_dir: notes_dir,
        output_dir: output_dir,
        content_dir: content_dir,
        pipeline_opts: pipeline_opts,
        transforms: @transforms,
        port: http_port,
        ws_port: ws_port
      ]
    }

    DynamicSupervisor.start_child(OrgGarden.DynamicSupervisor, child_spec)
  end

  defp wipe(content_dir) do
    Logger.info("Wiping #{content_dir}")
    File.mkdir_p!(content_dir)

    content_dir
    |> File.ls!()
    |> Enum.reject(&(&1 == ".gitkeep"))
    |> Enum.each(fn entry ->
      Path.join(content_dir, entry) |> File.rm_rf!()
    end)
  end
end