defmodule Raxol.Plugins.HotReloadManager do
  @moduledoc """
  Advanced hot-reload system for Plugin System v2.0.

  Features:
  - Intelligent code change detection
  - State preservation during reloads
  - Dependency-aware reloading
  - Rollback on failure
  - Development-friendly hot-swapping
  - Production-safe reload strategies
  """

  use Raxol.Core.Behaviours.BaseManager
  alias Raxol.Core.Runtime.Log
  # Aliases will be used when implementing full functionality
  # alias Raxol.Plugins.{PluginSystemV2, DependencyResolverV2, PluginSandbox}

  @type plugin_id :: String.t()
  @type reload_strategy :: :hot_swap | :graceful_restart | :dependency_cascade
  @type reload_options :: %{
          strategy: reload_strategy(),
          preserve_state: boolean(),
          backup_enabled: boolean(),
          dependency_handling:
            :ignore | :reload_dependents | :block_if_dependents,
          timeout_ms: non_neg_integer()
        }

  @type file_change :: %{
          path: String.t(),
          type: :created | :modified | :deleted,
          plugin_id: plugin_id(),
          timestamp: DateTime.t()
        }

  defstruct watched_paths: %{},
            plugin_states: %{},
            reload_queue: [],
            file_watcher_pid: nil,
            dependency_graph: %{},
            reload_history: [],
            backup_states: %{},
            active_reloads: %{}

  # Hot-Reload API

  # start_link is provided by BaseManager

  @doc """
  Enables hot-reload for a plugin with specified options.
  """
  def enable_hot_reload(plugin_id, plugin_path, opts \\ %{}) do
    GenServer.call(
      __MODULE__,
      {:enable_hot_reload, plugin_id, plugin_path, opts}
    )
  end

  @doc """
  Disables hot-reload for a plugin.
  """
  def disable_hot_reload(plugin_id) do
    GenServer.call(__MODULE__, {:disable_hot_reload, plugin_id})
  end

  @doc """
  Manually triggers a hot-reload for a plugin.
  """
  def reload_plugin(plugin_id, opts \\ %{}) do
    GenServer.call(__MODULE__, {:reload_plugin, plugin_id, opts}, 30_000)
  end

  @doc """
  Rolls back a plugin to its previous state.
  """
  def rollback_plugin(plugin_id) do
    GenServer.call(__MODULE__, {:rollback_plugin, plugin_id})
  end

  @doc """
  Gets hot-reload status for a plugin.
  """
  def get_reload_status(plugin_id) do
    GenServer.call(__MODULE__, {:get_reload_status, plugin_id})
  end

  @doc """
  Lists all plugins with hot-reload enabled.
  """
  def list_watched_plugins do
    GenServer.call(__MODULE__, :list_watched_plugins)
  end

  @doc """
  Gets reload history for debugging.
  """
  def get_reload_history(plugin_id \\ nil) do
    GenServer.call(__MODULE__, {:get_reload_history, plugin_id})
  end

  # Default Reload Options

  @doc """
  Returns default hot-reload options for development.
  """
  def development_options do
    %{
      strategy: :hot_swap,
      preserve_state: true,
      backup_enabled: true,
      dependency_handling: :reload_dependents,
      timeout_ms: 10_000
    }
  end

  @doc """
  Returns conservative hot-reload options for production.
  """
  def production_options do
    %{
      strategy: :graceful_restart,
      preserve_state: false,
      backup_enabled: true,
      dependency_handling: :block_if_dependents,
      timeout_ms: 30_000
    }
  end

  # GenServer Implementation

  @impl true
  def init_manager(opts) do
    state = %__MODULE__{
      watched_paths: %{},
      plugin_states: %{},
      reload_queue: [],
      file_watcher_pid: start_file_watcher(opts),
      dependency_graph: %{},
      reload_history: [],
      backup_states: %{},
      active_reloads: %{}
    }

    Log.info("Initialized with file watching")
    {:ok, state}
  end

  @impl true
  def handle_manager_call(
        {:enable_hot_reload, plugin_id, plugin_path, opts},
        _from,
        state
      ) do
    case enable_hot_reload_impl(plugin_id, plugin_path, opts, state) do
      {:ok, updated_state} ->
        Log.info(
          "[HotReloadManager] Enabled hot-reload for #{plugin_id} at #{plugin_path}"
        )

        {:reply, :ok, updated_state}

      {:error, reason} ->
        {:reply, {:error, reason}, state}
    end
  end

  @impl true
  def handle_manager_call({:disable_hot_reload, plugin_id}, _from, state) do
    case disable_hot_reload_impl(plugin_id, state) do
      {:ok, updated_state} ->
        Log.info("Disabled hot-reload for #{plugin_id}")
        {:reply, :ok, updated_state}

      {:error, reason} ->
        {:reply, {:error, reason}, state}
    end
  end

  @impl true
  def handle_manager_call({:reload_plugin, plugin_id, opts}, _from, state) do
    case reload_plugin_impl(plugin_id, opts, state) do
      {:ok, updated_state} ->
        {:reply, :ok, updated_state}

      {:error, reason} ->
        {:reply, {:error, reason}, state}
    end
  end

  @impl true
  def handle_manager_call({:rollback_plugin, plugin_id}, _from, state) do
    case rollback_plugin_impl(plugin_id, state) do
      {:ok, updated_state} ->
        Log.info("Rolled back plugin #{plugin_id}")
        {:reply, :ok, updated_state}

      {:error, reason} ->
        {:reply, {:error, reason}, state}
    end
  end

  @impl true
  def handle_manager_call({:get_reload_status, plugin_id}, _from, state) do
    status = get_reload_status_impl(plugin_id, state)
    {:reply, {:ok, status}, state}
  end

  @impl true
  def handle_manager_call(:list_watched_plugins, _from, state) do
    watched_plugins = Map.keys(state.watched_paths)
    {:reply, {:ok, watched_plugins}, state}
  end

  @impl true
  def handle_manager_call({:get_reload_history, plugin_id}, _from, state) do
    history = filter_reload_history(state.reload_history, plugin_id)
    {:reply, {:ok, history}, state}
  end

  @impl true
  def handle_manager_info({:file_changed, file_change}, state) do
    case handle_file_change(file_change, state) do
      {:ok, updated_state} ->
        {:noreply, updated_state}

      {:error, reason} ->
        Log.error(
          "[HotReloadManager] Failed to handle file change: #{inspect(reason)}"
        )

        {:noreply, state}
    end
  end

  @impl true
  def handle_manager_info({:reload_timeout, plugin_id}, state) do
    Log.error("Reload timeout for plugin #{plugin_id}")
    updated_active = Map.delete(state.active_reloads, plugin_id)
    {:noreply, %{state | active_reloads: updated_active}}
  end

  # Private Implementation

  defp enable_hot_reload_impl(plugin_id, plugin_path, opts, state) do
    case Map.get(state.watched_paths, plugin_id) do
      nil ->
        watch_config = %{
          plugin_id: plugin_id,
          path: plugin_path,
          options: merge_default_options(opts),
          enabled: true,
          last_change: nil
        }

        updated_watched = Map.put(state.watched_paths, plugin_id, watch_config)

        # Add to file watcher
        add_path_to_watcher(plugin_path, plugin_id, state.file_watcher_pid)

        {:ok, %{state | watched_paths: updated_watched}}

      _existing ->
        {:error, :already_watching}
    end
  end

  defp disable_hot_reload_impl(plugin_id, state) do
    case Map.get(state.watched_paths, plugin_id) do
      nil ->
        {:error, :not_watching}

      watch_config ->
        # Remove from file watcher
        remove_path_from_watcher(
          watch_config.path,
          plugin_id,
          state.file_watcher_pid
        )

        updated_watched = Map.delete(state.watched_paths, plugin_id)
        {:ok, %{state | watched_paths: updated_watched}}
    end
  end

  defp reload_plugin_impl(plugin_id, opts, state) do
    case Map.get(state.watched_paths, plugin_id) do
      nil ->
        {:error, :not_watching}

      watch_config ->
        merged_opts = Map.merge(watch_config.options, opts)

        case perform_reload(plugin_id, merged_opts, state) do
          {:ok, updated_state} ->
            # Record successful reload
            history_entry = %{
              plugin_id: plugin_id,
              timestamp: DateTime.utc_now(),
              action: :reload,
              strategy: merged_opts.strategy,
              success: true,
              # Would measure actual duration
              duration_ms: 0
            }

            final_state = %{
              updated_state
              | reload_history: [history_entry | updated_state.reload_history]
            }

            {:ok, final_state}

          {:error, reason} ->
            # Record failed reload
            history_entry = %{
              plugin_id: plugin_id,
              timestamp: DateTime.utc_now(),
              action: :reload,
              strategy: merged_opts.strategy,
              success: false,
              error: reason,
              duration_ms: 0
            }

            updated_history_state = %{
              state
              | reload_history: [history_entry | state.reload_history]
            }

            # Attempt rollback if backup enabled
            case merged_opts.backup_enabled do
              true ->
                case rollback_plugin_impl(plugin_id, updated_history_state) do
                  {:ok, final_state} ->
                    Log.warning(
                      "[HotReloadManager] Reload failed, rolled back #{plugin_id}"
                    )

                    {:ok, final_state}

                  {:error, rollback_error} ->
                    Log.error(
                      "[HotReloadManager] Reload and rollback both failed for #{plugin_id}"
                    )

                    {:error,
                     {:reload_and_rollback_failed, reason, rollback_error}}
                end

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

  defp perform_reload(plugin_id, opts, state) do
    Log.info(
      "[HotReloadManager] Starting #{opts.strategy} reload for #{plugin_id}"
    )

    # Create backup if enabled
    state_with_backup =
      if opts.backup_enabled do
        create_plugin_backup(plugin_id, state)
      else
        state
      end

    # Mark as actively reloading
    updated_active =
      Map.put(state_with_backup.active_reloads, plugin_id, DateTime.utc_now())

    active_state = %{state_with_backup | active_reloads: updated_active}

    # Set timeout
    Process.send_after(self(), {:reload_timeout, plugin_id}, opts.timeout_ms)

    # Perform reload based on strategy
    case opts.strategy do
      :hot_swap ->
        perform_hot_swap_reload(plugin_id, opts, active_state)

      :graceful_restart ->
        perform_graceful_restart_reload(plugin_id, opts, active_state)

      :dependency_cascade ->
        perform_dependency_cascade_reload(plugin_id, opts, active_state)
    end
  end

  defp perform_hot_swap_reload(plugin_id, opts, state) do
    # 1. Preserve current state if requested
    preserved_state =
      if opts.preserve_state do
        get_plugin_state(plugin_id)
      else
        nil
      end

    # 2. Reload the plugin module
    case reload_plugin_module(plugin_id) do
      :ok ->
        # 3. Restore state if preserved
        case preserved_state do
          nil -> :ok
          state_data -> restore_plugin_state(plugin_id, state_data)
        end

        # 4. Remove from active reloads
        updated_active = Map.delete(state.active_reloads, plugin_id)
        {:ok, %{state | active_reloads: updated_active}}

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

  defp perform_graceful_restart_reload(plugin_id, opts, state) do
    # 1. Gracefully stop the plugin
    case stop_plugin_gracefully(plugin_id, opts.timeout_ms) do
      :ok ->
        # 2. Reload the plugin module
        case reload_plugin_module(plugin_id) do
          :ok ->
            # 3. Restart the plugin
            case start_plugin(plugin_id) do
              :ok ->
                updated_active = Map.delete(state.active_reloads, plugin_id)
                {:ok, %{state | active_reloads: updated_active}}

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

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

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

  defp perform_dependency_cascade_reload(plugin_id, opts, state) do
    # 1. Find all dependent plugins
    dependents = find_dependent_plugins(plugin_id, state.dependency_graph)

    # 2. Reload in dependency order
    plugins_to_reload = [plugin_id | dependents]

    Enum.reduce_while(plugins_to_reload, {:ok, state}, fn current_plugin,
                                                          {:ok, acc_state} ->
      case perform_hot_swap_reload(current_plugin, opts, acc_state) do
        {:ok, updated_state} ->
          {:cont, {:ok, updated_state}}

        {:error, reason} ->
          {:halt, {:error, {current_plugin, reason}}}
      end
    end)
  end

  defp rollback_plugin_impl(plugin_id, state) do
    case Map.get(state.backup_states, plugin_id) do
      nil ->
        {:error, :no_backup_available}

      backup_state ->
        case restore_plugin_from_backup(plugin_id, backup_state) do
          :ok ->
            # Remove backup after successful rollback
            updated_backups = Map.delete(state.backup_states, plugin_id)

            history_entry = %{
              plugin_id: plugin_id,
              timestamp: DateTime.utc_now(),
              action: :rollback,
              success: true
            }

            {:ok,
             %{
               state
               | backup_states: updated_backups,
                 reload_history: [history_entry | state.reload_history]
             }}

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

  defp handle_file_change(file_change, state) do
    plugin_id = file_change.plugin_id

    case Map.get(state.watched_paths, plugin_id) do
      nil ->
        {:error, :plugin_not_watched}

      watch_config ->
        # Check if enough time has passed since last change (debouncing)
        if should_trigger_reload(watch_config, file_change) do
          # Add to reload queue
          updated_queue = [plugin_id | state.reload_queue]

          # Trigger reload after short delay (allow multiple file changes)
          Process.send_after(self(), {:process_reload_queue}, 100)

          updated_watch_config = %{
            watch_config
            | last_change: file_change.timestamp
          }

          updated_watched =
            Map.put(state.watched_paths, plugin_id, updated_watch_config)

          {:ok,
           %{
             state
             | reload_queue: updated_queue,
               watched_paths: updated_watched
           }}
        else
          {:ok, state}
        end
    end
  end

  # Helper Functions

  defp start_file_watcher(_opts) do
    # Mock implementation - would start actual file watcher
    Log.debug("Started file watcher")
    :mock_file_watcher
  end

  defp merge_default_options(opts) do
    Map.merge(development_options(), opts)
  end

  defp add_path_to_watcher(path, plugin_id, _watcher_pid) do
    Log.debug("Watching #{path} for #{plugin_id}")
    :ok
  end

  defp remove_path_from_watcher(path, plugin_id, _watcher_pid) do
    Log.debug("Stopped watching #{path} for #{plugin_id}")
    :ok
  end

  defp create_plugin_backup(plugin_id, state) do
    # Create backup of current plugin state
    backup_data = %{
      timestamp: DateTime.utc_now(),
      state: get_plugin_state(plugin_id),
      module_info: get_plugin_module_info(plugin_id)
    }

    updated_backups = Map.put(state.backup_states, plugin_id, backup_data)
    %{state | backup_states: updated_backups}
  end

  defp get_plugin_state(_plugin_id) do
    # Mock implementation - would get actual plugin state
    %{mock_state: true}
  end

  defp restore_plugin_state(_plugin_id, _state_data) do
    # Mock implementation - would restore plugin state
    :ok
  end

  defp reload_plugin_module(_plugin_id) do
    # Mock implementation - would reload plugin module
    Log.info("Reloading plugin module")
    :ok
  end

  defp stop_plugin_gracefully(_plugin_id, _timeout) do
    # Mock implementation - would gracefully stop plugin
    Log.info("Stopping plugin gracefully")
    :ok
  end

  defp start_plugin(_plugin_id) do
    # Mock implementation - would start plugin
    Log.info("Starting plugin")
    :ok
  end

  defp find_dependent_plugins(_plugin_id, _dependency_graph) do
    # Mock implementation - would find dependent plugins
    []
  end

  defp restore_plugin_from_backup(_plugin_id, _backup_state) do
    # Mock implementation - would restore from backup
    Log.info("Restoring plugin from backup")
    :ok
  end

  defp should_trigger_reload(watch_config, file_change) do
    case watch_config.last_change do
      nil ->
        true

      last_change ->
        # Debounce: only trigger if more than 500ms since last change
        DateTime.diff(file_change.timestamp, last_change, :millisecond) > 500
    end
  end

  defp get_reload_status_impl(plugin_id, state) do
    %{
      watching: Map.has_key?(state.watched_paths, plugin_id),
      actively_reloading: Map.has_key?(state.active_reloads, plugin_id),
      backup_available: Map.has_key?(state.backup_states, plugin_id),
      last_reload: get_last_reload_time(plugin_id, state.reload_history)
    }
  end

  defp filter_reload_history(history, nil), do: history

  defp filter_reload_history(history, plugin_id) do
    Enum.filter(history, fn entry -> entry.plugin_id == plugin_id end)
  end

  defp get_last_reload_time(plugin_id, history) do
    case Enum.find(history, fn entry ->
           entry.plugin_id == plugin_id and entry.success
         end) do
      nil -> nil
      entry -> entry.timestamp
    end
  end

  defp get_plugin_module_info(_plugin_id) do
    # Mock implementation - would get module information
    %{version: "1.0.0", loaded_at: DateTime.utc_now()}
  end
end
