defmodule Odinsea.Game.ReactorFactory do
  @moduledoc """
  Reactor Factory - loads and caches reactor template data.
  
  This module loads reactor metadata (states, types, items, timeouts) from cached JSON files.
  The JSON files should be exported from the Java server's WZ data providers.
  
  Reactor data is cached in ETS for fast lookups.
  
  Ported from Java: src/server/maps/MapleReactorFactory.java
  """

  use GenServer
  require Logger

  alias Odinsea.Game.{Reactor, ReactorStats}

  # ETS table name
  @reactor_stats :odinsea_reactor_stats

  # Data file path
  @reactor_data_file "data/reactors.json"

  ## Public API

  @doc "Starts the ReactorFactory GenServer"
  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @doc """
  Gets reactor stats by reactor ID.
  Returns nil if not found.
  """
  @spec get_reactor_stats(integer()) :: ReactorStats.t() | nil
  def get_reactor_stats(reactor_id) do
    case :ets.lookup(@reactor_stats, reactor_id) do
      [{^reactor_id, stats}] -> stats
      [] -> nil
    end
  end

  @doc """
  Gets a reactor instance by ID.
  Returns nil if stats not found.
  """
  @spec get_reactor(integer()) :: Reactor.t() | nil
  def get_reactor(reactor_id) do
    case get_reactor_stats(reactor_id) do
      nil -> nil
      stats -> Reactor.new(reactor_id, stats)
    end
  end

  @doc """
  Creates a reactor instance with position and properties.
  """
  @spec create_reactor(integer(), integer(), integer(), integer(), String.t(), integer()) :: Reactor.t() | nil
  def create_reactor(reactor_id, x, y, facing_direction \\ 0, name \\ "", delay \\ -1) do
    case get_reactor_stats(reactor_id) do
      nil -> 
        Logger.warning("Reactor stats not found for reactor_id=#{reactor_id}")
        nil
      
      stats ->
        %Reactor{
          reactor_id: reactor_id,
          stats: stats,
          x: x,
          y: y,
          facing_direction: facing_direction,
          name: name,
          delay: delay,
          state: 0,
          alive: true,
          timer_active: false,
          custom: false
        }
    end
  end

  @doc """
  Checks if reactor stats exist.
  """
  @spec reactor_exists?(integer()) :: boolean()
  def reactor_exists?(reactor_id) do
    :ets.member(@reactor_stats, reactor_id)
  end

  @doc """
  Gets all loaded reactor IDs.
  """
  @spec get_all_reactor_ids() :: [integer()]
  def get_all_reactor_ids do
    :ets.select(@reactor_stats, [{{:"$1", :_}, [], [:"$1"]}])
  end

  @doc """
  Gets the number of loaded reactors.
  """
  @spec get_reactor_count() :: integer()
  def get_reactor_count do
    :ets.info(@reactor_stats, :size)
  end

  @doc """
  Reloads reactor data from files.
  """
  def reload do
    GenServer.call(__MODULE__, :reload, :infinity)
  end

  ## GenServer Callbacks

  @impl true
  def init(_opts) do
    # Create ETS table
    :ets.new(@reactor_stats, [:set, :public, :named_table, read_concurrency: true])

    # Load data
    load_reactor_data()

    {:ok, %{}}
  end

  @impl true
  def handle_call(:reload, _from, state) do
    Logger.info("Reloading reactor data...")
    load_reactor_data()
    {:reply, :ok, state}
  end

  ## Private Functions

  defp load_reactor_data do
    priv_dir = :code.priv_dir(:odinsea) |> to_string()
    file_path = Path.join(priv_dir, @reactor_data_file)

    load_reactors_from_file(file_path)

    count = :ets.info(@reactor_stats, :size)
    Logger.info("Loaded #{count} reactor templates")
  end

  defp load_reactors_from_file(file_path) do
    case File.read(file_path) do
      {:ok, content} ->
        case Jason.decode(content) do
          {:ok, reactors} when is_map(reactors) ->
            # Clear existing data
            :ets.delete_all_objects(@reactor_stats)
            
            # Load reactors and handle links
            links = process_reactors(reactors, %{})
            
            # Resolve links
            resolve_links(links)
            
            :ok

          {:error, reason} ->
            Logger.warning("Failed to parse reactors JSON: #{inspect(reason)}")
            create_fallback_reactors()
        end

      {:error, :enoent} ->
        Logger.warning("Reactors file not found: #{file_path}, using fallback data")
        create_fallback_reactors()

      {:error, reason} ->
        Logger.error("Failed to read reactors: #{inspect(reason)}")
        create_fallback_reactors()
    end
  end

  defp process_reactors(reactors, links) do
    Enum.reduce(reactors, links, fn {reactor_id_str, reactor_data}, acc_links ->
      reactor_id = String.to_integer(reactor_id_str)
      
      # Check if this is a link to another reactor
      link_target = reactor_data["link"]
      
      if link_target && link_target > 0 do
        # Store link for later resolution
        Map.put(acc_links, reactor_id, link_target)
      else
        # Build stats from data
        stats = ReactorStats.from_json(reactor_data)
        :ets.insert(@reactor_stats, {reactor_id, stats})
        acc_links
      end
    end)
  end

  defp resolve_links(links) do
    Enum.each(links, fn {reactor_id, target_id} ->
      case :ets.lookup(@reactor_stats, target_id) do
        [{^target_id, target_stats}] ->
          # Copy target stats for linked reactor
          :ets.insert(@reactor_stats, {reactor_id, target_stats})
        
        [] ->
          Logger.warning("Link target not found: #{target_id} for reactor #{reactor_id}")
      end
    end)
  end

  # Fallback data for basic testing
  defp create_fallback_reactors do
    # Common reactors from MapleStory
    fallback_reactors = [
      %{
        reactor_id: 100000,  # Normal box
        states: %{
          "0" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      },
      %{
        reactor_id: 200000,  # Herb
        activate_by_touch: true,
        states: %{
          "0" => %{type: 2, next_state: 1, timeout: -1, can_touch: 2},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      },
      %{
        reactor_id: 200100,  # Vein
        activate_by_touch: true,
        states: %{
          "0" => %{type: 2, next_state: 1, timeout: -1, can_touch: 2},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      },
      %{
        reactor_id: 200200,  # Gold Flower
        activate_by_touch: true,
        states: %{
          "0" => %{type: 2, next_state: 1, timeout: -1, can_touch: 2},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      },
      %{
        reactor_id: 200300,  # Silver Flower
        activate_by_touch: true,
        states: %{
          "0" => %{type: 2, next_state: 1, timeout: -1, can_touch: 2},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      },
      %{
        reactor_id: 100011,  # Mysterious Herb
        activate_by_touch: true,
        states: %{
          "0" => %{type: 2, next_state: 1, timeout: -1, can_touch: 2},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      },
      %{
        reactor_id: 200011,  # Mysterious Vein
        activate_by_touch: true,
        states: %{
          "0" => %{type: 2, next_state: 1, timeout: -1, can_touch: 2},
          "1" => %{type: 999, next_state: -1, timeout: -1, can_touch: 0}
        }
      }
    ]

    Enum.each(fallback_reactors, fn reactor_data ->
      stats = ReactorStats.from_json(reactor_data)
      :ets.insert(@reactor_stats, {reactor_data.reactor_id, stats})
    end)

    Logger.info("Created #{length(fallback_reactors)} fallback reactor templates")
  end
end