defmodule Odinsea.AntiCheat.LieDetector do
  @moduledoc """
  Lie detector (Anti-Macro) system for bot detection.
  
  Ported from: client.AntiMacro.java, tools.packet.AntiMacroPacket.java
  
  The lie detector system:
  - Sends a CAPTCHA image to the player
  - Player has 60 seconds to respond
  - If failed, player is punished (HP/MP to 0)
  - If passed, reward can be given
  
  ## Response Types
  
  - 0x00: Req_Fail_InvalidCharacterName
  - 0x01: Req_Fail_NotAttack
  - 0x02: Req_Fail_NotAvailableTime
  - 0x03: Req_Fail_SolvingQuestion
  - 0x04: Pended
  - 0x05: Success
  - 0x06: Res
  - 0x07: Res_Fail
  - 0x08: Res_TargetFail
  - 0x09: Res_Success
  - 0x0A: Res_TargetSuccess
  - 0x0B: Res_Reward
  
  ## State
  
  - `character_id`: The character being tested
  - `in_progress`: Whether a test is currently running
  - `passed`: Whether the player has passed
  - `attempt`: Remaining attempts (-1 = failed)
  - `answer`: The correct answer
  - `tester`: Who initiated the test
  - `type`: 0 = item, 1 = admin
  - `last_time`: Timestamp of last test
  """

  use GenServer

  require Logger

  alias Odinsea.Game.Character
  alias Odinsea.World

  @table :lie_detectors

  # Test timeout in milliseconds (60 seconds)
  @test_timeout 60_000

  # Cooldown between tests (10 minutes)
  @test_cooldown 600_000

  # Reward for passing (meso)
  @pass_reward 5000

  # Punishment for failing (meso to tester)
  @fail_reward_to_TESTER 7000

  # =============================================================================
  # Response Types
  # =============================================================================

  defmodule ResponseType do
    @moduledoc "Lie detector response types"
    
    def req_fail_invalid_character_name, do: 0x00
    def req_fail_not_attack, do: 0x01
    def req_fail_not_available_time, do: 0x02
    def req_fail_solving_question, do: 0x03
    def pended, do: 0x04
    def success, do: 0x05
    def res, do: 0x06
    def res_fail, do: 0x07
    def res_target_fail, do: 0x08
    def res_success, do: 0x09
    def res_target_success, do: 0x0A
    def res_reward, do: 0x0B
  end

  # =============================================================================
  # Public API
  # =============================================================================

  @doc """
  Starts the lie detector system and creates ETS table.
  """
  def start_system do
    case :ets.info(@table) do
      :undefined -> 
        :ets.new(@table, [:set, :public, :named_table, read_concurrency: true])
        :ok
      _ -> 
        :ok
    end
  end

  @doc """
  Starts a lie detector session for a character.
  """
  def start_session(character_id) do
    start_system()
    
    case lookup_session(character_id) do
      nil ->
        # Create new session
        session = %{
          character_id: character_id,
          in_progress: false,
          passed: false,
          attempt: 1,
          answer: nil,
          tester: "",
          type: 0,
          last_time: 0,
          timer_ref: nil
        }
        
        :ets.insert(@table, {character_id, session})
        {:ok, session}
        
      existing ->
        {:ok, existing}
    end
  end

  @doc """
  Ends a lie detector session.
  """
  def end_session(character_id) do
    case lookup_session(character_id) do
      nil -> :ok
      session ->
        # Cancel any pending timer
        if session.timer_ref do
          Process.cancel_timer(session.timer_ref)
        end
        
        :ets.delete(@table, character_id)
        :ok
    end
  end

  @doc """
  Starts a lie detector test for a character.
  
  Options:
  - `tester`: Who initiated the test (default: "Admin")
  - `is_item`: Whether started via item (default: false)
  - `another_attempt`: Whether this is a retry (default: false)
  """
  def start_test(character_id, opts \\ []) do
    tester = Keyword.get(opts, :tester, "Admin")
    is_item = Keyword.get(opts, :is_item, false)
    another_attempt = Keyword.get(opts, :another_attempt, false)
    
    # Ensure session exists
    {:ok, session} = start_session(character_id)
    
    # Check if can start test
    cond do
      not another_attempt and session.passed and is_item ->
        {:error, :already_passed}
        
      not another_attempt and session.in_progress ->
        {:error, :already_in_progress}
        
      not another_attempt and session.attempt == -1 ->
        {:error, :already_failed}
        
      true ->
        do_start_test(character_id, tester, is_item, session)
    end
  end

  @doc """
  Validates a lie detector response from a player.
  """
  def validate_response(character_id, response) do
    case lookup_session(character_id) do
      nil ->
        {:error, :no_session}
        
      session ->
        if not session.in_progress do
          {:error, :not_in_progress}
        else
          # Cancel timeout timer
          if session.timer_ref do
            Process.cancel_timer(session.timer_ref)
          end
          
          # Check answer
          if String.upcase(response) == String.upcase(session.answer) do
            # Correct!
            handle_pass(character_id, session)
          else
            # Wrong!
            handle_fail(character_id, session)
          end
        end
    end
  end

  @doc """
  Checks if a character can be tested (cooldown check).
  """
  def can_test?(character_id) do
    case lookup_session(character_id) do
      nil -> true
      session ->
        now = System.system_time(:millisecond)
        now > session.last_time + @test_cooldown
    end
  end

  @doc """
  Gets the current state of a lie detector session.
  """
  def get_session(character_id) do
    lookup_session(character_id)
  end

  @doc """
  Admin command to start lie detector on a player.
  """
  def admin_start_lie_detector(target_name, admin_name \\ "Admin") do
    # Look up character by name
    case World.find_character_by_name(target_name) do
      nil ->
        {:error, :character_not_found}
        
      character ->
        character_id = Map.get(character, :id)
        start_test(character_id, tester: admin_name, is_item: false)
    end
  end

  # =============================================================================
  # Packet Builders
  # =============================================================================

  @doc """
  Builds the lie detector packet with CAPTCHA image.
  
  Ported from: AntiMacroPacket.sendLieDetector()
  """
  def build_lie_detector_packet(image_data, attempts_remaining) do
    # Opcode will be added by packet builder
    packet = <<>>
    
    # Response type: 0x06 (Res)
    packet = packet <> <<ResponseType.res()>>
    
    # Action: 4 (show CAPTCHA)
    packet = packet <> <<4>>
    
    # Attempts remaining
    packet = packet <> <<attempts_remaining>>
    
    # JPEG image data
    packet = packet <> encode_jpeg(image_data)
    
    packet
  end

  @doc """
  Builds a lie detector response packet.
  
  Ported from: AntiMacroPacket.LieDetectorResponse()
  """
  def build_response_packet(msg_type, msg2 \\ 0) do
    packet = <<>>
    packet = packet <> <<msg_type>>
    packet = packet <> <<msg2>>
    packet
  end

  @doc """
  Builds various lie detector message packets.
  """
  def build_message_packet(type, opts \\ []) do
    packet = <<>>
    packet = packet <> <<type>>
    
    case type do
      4 -> # Save screenshot
        packet = packet <> <<0>>
        packet = packet <> encode_string(Keyword.get(opts, :filename, ""))
        
      5 -> # Success with tester name
        packet = packet <> <<1>>
        packet = packet <> encode_string(Keyword.get(opts, :tester, ""))
        
      6 -> # Admin picture
        packet = packet <> <<4>>
        packet = packet <> <<1>>
        # Image data would go here
        
      7 -> # Failed
        packet = packet <> <<4>>
        
      9 -> # Success/Passed
        packet = packet <> <<Keyword.get(opts, :result, 0)>>
        
      10 -> # Passed message
        packet = packet <> <<0>>
        packet = packet <> encode_string(Keyword.get(opts, :message, ""))
        packet = packet <> encode_string("")
        
      _ ->
        packet = packet <> <<0>>
    end
    
    packet
  end

  # =============================================================================
  # Private Functions
  # =============================================================================

  defp lookup_session(character_id) do
    case :ets.lookup(@table, character_id) do
      [{^character_id, session}] -> session
      [] -> nil
    end
  end

  defp update_session(character_id, updates) do
    case lookup_session(character_id) do
      nil -> :error
      session ->
        new_session = Map.merge(session, updates)
        :ets.insert(@table, {character_id, new_session})
        {:ok, new_session}
    end
  end

  defp do_start_test(character_id, tester, is_item, session) do
    # Generate CAPTCHA
    {answer, image_data} = generate_captcha()
    
    # Update session
    new_attempt = session.attempt - 1
    
    {:ok, new_session} = update_session(character_id, %{
      in_progress: true,
      passed: false,
      attempt: new_attempt,
      answer: answer,
      tester: tester,
      type: if(is_item, do: 0, else: 1),
      last_time: System.system_time(:millisecond)
    })
    
    # Schedule timeout
    timer_ref = Process.send_after(
      self(),
      {:lie_detector_timeout, character_id, is_item},
      @test_timeout
    )
    
    update_session(character_id, %{timer_ref: timer_ref})
    
    # Build packet
    packet = build_lie_detector_packet(image_data, new_attempt + 1)
    
    # Send to character
    send_to_character(character_id, packet)
    
    {:ok, new_session}
  end

  defp handle_pass(character_id, session) do
    # Mark as passed
    update_session(character_id, %{
      in_progress: false,
      passed: true,
      attempt: 1,
      last_time: System.system_time(:millisecond)
    })
    
    # Send success packet
    packet = build_response_packet(ResponseType.res_success(), 0)
    send_to_character(character_id, packet)
    
    # Give reward if applicable
    if session.type == 0 do
      # Item-initiated, give reward
      give_reward(character_id)
    end
    
    # Log
    Logger.info("[LieDetector] Character #{character_id} passed the test")
    
    :ok
  end

  defp handle_fail(character_id, session) do
    if session.attempt == -1 do
      # Out of attempts - execute punishment
      execute_punishment(character_id, session)
    else
      # Try again
      start_test(character_id, 
        tester: session.tester, 
        is_item: session.type == 0,
        another_attempt: true
      )
    end
  end

  defp execute_punishment(character_id, session) do
    # Update session
    update_session(character_id, %{
      in_progress: false,
      passed: false,
      attempt: -1
    })
    
    # Send fail packet
    packet = build_response_packet(ResponseType.res_fail(), 0)
    send_to_character(character_id, packet)
    
    # Punish character (set HP/MP to 0)
    punish_character(character_id)
    
    # Reward tester if applicable
    if session.tester != "" and session.tester != "Admin" do
      reward_tester(session.tester, character_id)
    end
    
    # Broadcast to GMs
    broadcast_gm_alert(character_id)
    
    # Log
    Logger.warning("[LieDetector] Character #{character_id} failed the test - punished")
    
    :ok
  end

  defp punish_character(character_id) do
    # Set HP and MP to 0
    Character.set_hp(character_id, 0)
    Character.set_mp(character_id, 0)
    
    # Update stats
    Character.update_single_stat(character_id, :hp, 0)
    Character.update_single_stat(character_id, :mp, 0)
  end

  defp reward_tester(tester_name, failed_character_id) do
    # Find tester
    case World.find_character_by_name(tester_name) do
      nil ->
        :ok
        
      tester ->
        # Give meso reward
        Character.gain_meso(Map.get(tester, :id), @fail_reward_to_TESTER, true)
        
        # Send message
        msg = "#{failed_character_id} did not pass the lie detector test. You received #{@fail_reward_to_TESTER} meso."
        Character.drop_message(Map.get(tester, :id), 5, msg)
    end
  end

  defp give_reward(character_id) do
    # Give reward for passing
    Character.gain_meso(character_id, @pass_reward, true)
    
    # Send reward packet
    packet = build_response_packet(ResponseType.res_reward(), 1)
    send_to_character(character_id, packet)
  end

  defp send_to_character(character_id, packet) do
    # This would send the packet through the character's client connection
    # Implementation depends on the channel client system
    :ok
  end

  defp broadcast_gm_alert(character_id) do
    # TODO: Broadcast to GMs through World service
    Logger.info("[LieDetector] GM Alert: Character #{character_id} failed lie detector")
    :ok
  end

  defp generate_captcha do
    # Generate a simple text CAPTCHA
    # In production, this would generate an image
    
    # Random 4-6 character alphanumeric code
    chars = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
    length = Enum.random(4..6)
    
    answer = 
      1..length
      |> Enum.map(fn _ -> String.at(chars, Enum.random(0..(String.length(chars) - 1))) end)
      |> Enum.join()
    
    # For now, return a placeholder image
    # In production, this would generate a JPEG image with the text
    image_data = generate_captcha_image(answer)
    
    {answer, image_data}
  end

  defp generate_captcha_image(answer) do
    # Placeholder - in production, this would use an image generation library
    # or pre-generated CAPTCHA images
    
    # Return a simple binary representation
    # Real implementation would use something like:
    # - Mogrify (ImageMagick wrapper)
    # - Imagine (Elixir image library)
    # - Pre-generated CAPTCHA images stored in priv/
    
    <<0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 
      String.length(answer)::32, answer::binary>>
  end

  defp encode_string(str) do
    len = String.length(str)
    <<len::16-little, str::binary>>
  end

  defp encode_jpeg(data) do
    # Prepend length and data
    len = byte_size(data)
    <<len::32-little, data::binary>>
  end

  # =============================================================================
  # GenServer for timeout handling
  # =============================================================================

  defmodule TimeoutHandler do
    @moduledoc "Handles lie detector timeouts"
    
    use GenServer
    
    alias Odinsea.AntiCheat.LieDetector
    
    def start_link(_opts) do
      GenServer.start_link(__MODULE__, [], name: __MODULE__)
    end
    
    def init(_) do
      {:ok, %{}}
    end
    
    def handle_info({:lie_detector_timeout, character_id, is_item}, state) do
      # Timeout occurred - treat as failure
      case LieDetector.lookup_session(character_id) do
        nil -> 
          {:noreply, state}
          
        session ->
          if session.in_progress do
            # Execute timeout punishment
            LieDetector.execute_punishment(character_id, session)
          end
          {:noreply, state}
      end
    end
  end
end