defmodule Odinsea.Net.Processor do
  @moduledoc """
  Central packet routing/dispatch system.
  Ported from Java PacketProcessor.java

  Routes incoming packets to appropriate handlers based on:
  - Server type (Login, Channel, Shop)
  - Packet opcode
  """

  require Logger

  alias Odinsea.Net.Packet.In
  alias Odinsea.Net.Opcodes

  @type server_type :: :login | :channel | :shop
  @type client_state :: map()

  # ==================================================================================================
  # Main Entry Point
  # ==================================================================================================

  @doc """
  Main packet handler entry point.
  Routes packets to appropriate server-specific handlers.

  ## Parameters
  - `opcode` - The packet opcode (integer)
  - `packet` - The InPacket struct (already read past opcode)
  - `client_state` - The client's state map
  - `server_type` - :login | :channel | :shop

  ## Returns
  - `{:ok, new_state}` - Success with updated state
  - `{:error, reason, state}` - Error with reason
  - `{:disconnect, reason}` - Client should be disconnected
  """
  def handle(opcode, %In{} = packet, client_state, server_type) do
    # Pre-process common packets that apply to all server types
    case preprocess(opcode, packet, client_state) do
      {:handled, new_state} ->
        {:ok, new_state}

      :continue ->
        # Route to server-specific handler
        case server_type do
          :login ->
            handle_login(opcode, packet, client_state)

          :shop ->
            handle_shop(opcode, packet, client_state)

          :channel ->
            handle_channel(opcode, packet, client_state)

          _ ->
            Logger.warning("Unknown server type: #{inspect(server_type)}")
            {:ok, client_state}
        end
    end
  rescue
    e ->
      Logger.error("Packet processing error: #{inspect(e)}")
      {:error, :processing_error, client_state}
  end

  # ==================================================================================================
  # Pre-Processing (Common Packets)
  # ==================================================================================================

  @doc """
  Pre-processes packets that are common across all server types.
  Returns {:handled, state} if the packet was fully handled.
  Returns :continue if the packet should be routed to server-specific handlers.
  """
  # Define opcodes as module attributes for use in guards
  @cp_security_packet Opcodes.cp_security_packet()
  @cp_alive_ack Opcodes.cp_alive_ack()
  @cp_client_dump_log Opcodes.cp_client_dump_log()
  @cp_hardware_info Opcodes.cp_hardware_info()
  @cp_inject_packet Opcodes.cp_inject_packet()
  @cp_set_code_page Opcodes.cp_set_code_page()
  @cp_window_focus Opcodes.cp_window_focus()
  @cp_exception_log Opcodes.cp_exception_log()

  defp preprocess(opcode, packet, state) do
    case opcode do
      # Security packet - always handled in pre-process
      @cp_security_packet ->
        handle_security_packet(packet, state)
        {:handled, state}

      # Alive acknowledgement - keep connection alive
      @cp_alive_ack ->
        handle_alive_ack(state)
        {:handled, state}

      # Client dump log - debugging/crash reports
      @cp_client_dump_log ->
        handle_dump_log(packet, state)
        {:handled, state}

      # Hardware info - client machine identification
      @cp_hardware_info ->
        handle_hardware_info(packet, state)
        {:handled, state}

      # Packet injection attempt - security violation
      @cp_inject_packet ->
        handle_inject_packet(packet, state)
        {:disconnect, :packet_injection}

      # Code page settings
      @cp_set_code_page ->
        handle_code_page(packet, state)
        {:handled, state}

      # Window focus - anti-cheat detection
      @cp_window_focus ->
        handle_window_focus(packet, state)
        {:handled, state}

      # Exception log from client
      @cp_exception_log ->
        handle_exception_log(packet, state)
        {:handled, state}

      # Not a common packet, continue to server-specific handling
      _ ->
        :continue
    end
  end

  # Login opcodes as module attributes
  @cp_client_hello Opcodes.cp_client_hello()
  @cp_check_password Opcodes.cp_check_password()
  @cp_world_info_request Opcodes.cp_world_info_request()
  @cp_select_world Opcodes.cp_select_world()
  @cp_check_user_limit Opcodes.cp_check_user_limit()
  @cp_check_duplicated_id Opcodes.cp_check_duplicated_id()
  @cp_create_new_character Opcodes.cp_create_new_character()
  @cp_create_ultimate Opcodes.cp_create_ultimate()
  @cp_delete_character Opcodes.cp_delete_character()
  @cp_select_character Opcodes.cp_select_character()
  @cp_check_spw_request Opcodes.cp_check_spw_request()
  @cp_rsa_key Opcodes.cp_rsa_key()

  # ==================================================================================================
  # Login Server Packet Handlers
  # ==================================================================================================

  @doc """
  Routes packets for the Login server.
  Delegates to Odinsea.Login.Handler module.
  """
  defp handle_login(opcode, packet, state) do
    alias Odinsea.Login.Handler

    case opcode do
      # Permission request (client hello / initial handshake)
      @cp_client_hello ->
        Handler.on_permission_request(packet, state)

      # Password check (login authentication)
      @cp_check_password ->
        Handler.on_check_password(packet, state)

      # World info request (server list)
      @cp_world_info_request ->
        Handler.on_world_info_request(state)

      # Select world
      @cp_select_world ->
        Handler.on_select_world(packet, state)

      # Check user limit (channel population check)
      @cp_check_user_limit ->
        Handler.on_check_user_limit(state)

      # Check duplicated ID (character name availability)
      @cp_check_duplicated_id ->
        Handler.on_check_duplicated_id(packet, state)

      # Create new character
      @cp_create_new_character ->
        Handler.on_create_new_character(packet, state)

      # Create ultimate (Cygnus Knights)
      @cp_create_ultimate ->
        Handler.on_create_ultimate(packet, state)

      # Delete character
      @cp_delete_character ->
        Handler.on_delete_character(packet, state)

      # Select character (enter game)
      @cp_select_character ->
        Handler.on_select_character(packet, state)

      # Second password check
      @cp_check_spw_request ->
        Handler.on_check_spw_request(packet, state)

      # RSA key request
      @cp_rsa_key ->
        Handler.on_rsa_key(packet, state)

      # Unhandled login packet
      _ ->
        Logger.debug("Unhandled login packet: opcode=0x#{Integer.to_string(opcode, 16)}")
        {:ok, state}
    end
  end

  # Channel opcodes as module attributes
  @cp_migrate_in Opcodes.cp_migrate_in()
  @cp_move_player Opcodes.cp_move_player()
  @cp_general_chat Opcodes.cp_general_chat()
  @cp_change_map Opcodes.cp_change_map()

  # ==================================================================================================
  # Channel Server Packet Handlers
  # ==================================================================================================

  @doc """
  Routes packets for the Channel server (game world).
  Delegates to appropriate handler modules.
  """
  defp handle_channel(opcode, packet, state) do
    # TODO: Implement channel packet routing
    # Will route to:
    # - Odinsea.Channel.Handler.Player (movement, attacks, skills)
    # - Odinsea.Channel.Handler.Inventory (items, equipment)
    # - Odinsea.Channel.Handler.Mob (monster interactions)
    # - Odinsea.Channel.Handler.NPC (NPC dialogs, shops)
    # - Odinsea.Channel.Handler.Chat (chat, party, guild)
    # - etc.

    case opcode do
      # Migrate in from login server
      @cp_migrate_in ->
        {character_id, _} = In.decode_int(packet)
        handle_migrate_in(character_id, state)

      # Player movement
      @cp_move_player ->
        {:ok, state}  # TODO: Implement

      # General chat
      @cp_general_chat ->
        {:ok, state}  # TODO: Implement

      # Change map
      @cp_change_map ->
        {:ok, state}  # TODO: Implement

      # Unhandled channel packet
      _ ->
        Logger.debug("Unhandled channel packet: opcode=0x#{Integer.to_string(opcode, 16)}")
        {:ok, state}
    end
  end

  # Shop opcodes as module attributes
  @cp_buy_cs_item Opcodes.cp_buy_cs_item()
  @cp_coupon_code Opcodes.cp_coupon_code()
  @cp_cs_update Opcodes.cp_cs_update()

  # ==================================================================================================
  # Cash Shop Server Packet Handlers
  # ==================================================================================================

  @doc """
  Routes packets for the Cash Shop server.
  Delegates to Odinsea.Shop.Handler module.
  """
  defp handle_shop(opcode, packet, state) do
    # TODO: Implement cash shop packet routing

    case opcode do
      # Migrate in from channel server
      @cp_migrate_in ->
        {character_id, _} = In.decode_int(packet)
        handle_migrate_in(character_id, state)

      # Buy cash item
      @cp_buy_cs_item ->
        {:ok, state}  # TODO: Implement

      # Coupon code
      @cp_coupon_code ->
        {:ok, state}  # TODO: Implement

      # Cash shop update
      @cp_cs_update ->
        {:ok, state}  # TODO: Implement

      # Leave cash shop
      @cp_change_map ->
        {:ok, state}  # TODO: Implement

      # Unhandled shop packet
      _ ->
        Logger.debug("Unhandled shop packet: opcode=0x#{Integer.to_string(opcode, 16)}")
        {:ok, state}
    end
  end

  # ==================================================================================================
  # Common Packet Implementations
  # ==================================================================================================

  defp handle_security_packet(_packet, _state) do
    # Security packet - just acknowledge
    # In the Java version, this is a no-op that returns true in preProcess
    :ok
  end

  defp handle_alive_ack(state) do
    # Update last alive time
    new_state = Map.put(state, :last_alive, System.system_time(:millisecond))
    Logger.debug("Alive ack received from #{state.ip}")
    {:ok, new_state}
  end

  defp handle_dump_log(packet, state) do
    {call_type, packet} = In.decode_short(packet)
    {error_code, packet} = In.decode_int(packet)
    {backup_buffer_size, packet} = In.decode_short(packet)
    {raw_seq, packet} = In.decode_int(packet)
    {p_type, packet} = In.decode_short(packet)
    {backup_buffer, _packet} = In.decode_buffer(packet, backup_buffer_size - 6)

    log_msg = "[ClientDumpLog] RawSeq: #{raw_seq} CallType: #{call_type} " <>
              "ErrorCode: #{error_code} BufferSize: #{backup_buffer_size} " <>
              "Type: 0x#{Integer.to_string(p_type, 16)} " <>
              "Packet: #{inspect(backup_buffer, limit: :infinity)}"

    Logger.warning(log_msg)
    :ok
  end

  defp handle_hardware_info(packet, state) do
    {hardware_info, _packet} = In.decode_string(packet)
    new_state = Map.put(state, :hardware_info, hardware_info)
    Logger.debug("Hardware info: #{hardware_info}")
    {:ok, new_state}
  end

  defp handle_inject_packet(packet, state) do
    start = packet.position
    finish = byte_size(packet.data) - 2

    # Read opcode at end
    packet = %{packet | position: finish}
    {opcode, _packet} = In.decode_short(packet)

    # Get hex string of injected packet
    injected_data = binary_part(packet.data, start, finish - start)

    player_name = Map.get(state, :character_name, "<none>")
    player_id = Map.get(state, :character_id, 0)

    Logger.error(
      "[InjectPacket] [Session #{state.ip}] [Player #{player_name} - #{player_id}] " <>
      "[OpCode 0x#{Integer.to_string(opcode, 16)}] #{inspect(injected_data, limit: :infinity)}"
    )

    :ok
  end

  defp handle_code_page(packet, state) do
    {code_page, packet} = In.decode_int(packet)
    {code_page_read, _packet} = In.decode_int(packet)

    new_state =
      state
      |> Map.put(:code_page, code_page)
      |> Map.put(:code_page_read, code_page_read)

    Logger.debug("Code page set: #{code_page}, read: #{code_page_read}")
    {:ok, new_state}
  end

  defp handle_window_focus(packet, state) do
    {focus, _packet} = In.decode_byte(packet)

    if focus == 0 do
      player_name = Map.get(state, :character_name, "<none>")
      player_id = Map.get(state, :character_id, 0)

      Logger.warning(
        "[WindowFocus] Client lost focus [Session #{state.ip}] [Player #{player_name} - #{player_id}]"
      )
    end

    :ok
  end

  defp handle_exception_log(packet, state) do
    {exception_msg, _packet} = In.decode_string(packet)

    Logger.warning("[ClientExceptionLog] [Session #{state.ip}] #{exception_msg}")
    :ok
  end

  defp handle_migrate_in(character_id, state) do
    # TODO: Load character from database, restore session
    Logger.info("Migrate in: character_id=#{character_id}")
    new_state = Map.put(state, :character_id, character_id)
    {:ok, new_state}
  end
end