defmodule Odinsea.Channel.Handler.Pickup do
  @moduledoc """
  Handles drop pickup from the map (item and meso drops).
  Ported from src/handling/channel/handler/InventoryHandler.java
  
  This handler processes CP_ItemPickup (0x10C) packets when a player
  attempts to pick up a drop from the map.
  """

  require Logger

  alias Odinsea.Net.Packet.{In, Out}
  alias Odinsea.Net.Opcodes
  alias Odinsea.Game.{Character, Drop, Map}
  alias Odinsea.Channel.Packets

  @doc """
  Handles item pickup from map (CP_ItemPickup).
  
  Packet structure:
  - tick (4 bytes): Client tick count
  - oid (4 bytes): Object ID of the drop on the map
  
  Ported from InventoryHandler.handlePickup()
  """
  def handle_item_pickup(packet, client_state) do
    with {:ok, character_pid} <- get_character(client_state),
         {:ok, character} <- Character.get_state(character_pid) do
      
      # Decode packet
      {_tick, packet} = In.decode_int(packet)
      {drop_oid, _packet} = In.decode_int(packet)

      Logger.debug("Item pickup attempt: character=#{character.name}, drop_oid=#{drop_oid}")

      # Attempt to pick up the drop
      case attempt_pickup_drop(character, character_pid, drop_oid, client_state.channel_id) do
        {:ok, :meso, amount} ->
          Logger.debug("Picked up meso: #{amount}")
          # Send pickup success response
          send_pickup_result(client_state, 0, 0)
          {:ok, client_state}

        {:ok, :item, item} ->
          Logger.debug("Picked up item: #{item.item_id}")
          # Send pickup success response
          send_pickup_result(client_state, 0, 0)
          {:ok, client_state}

        {:error, reason} ->
          Logger.debug("Pickup failed: #{reason}")
          # Send failure response (enable actions to unblock client)
          send_enable_actions(client_state)
          {:ok, client_state}
      end
    else
      {:error, reason} ->
        Logger.warning("Item pickup failed: #{inspect(reason)}")
        send_enable_actions(client_state)
        {:ok, client_state}
    end
  end

  @doc """
  Handles pet item pickup request (CP_PetDropPickUpRequest).
  
  Similar to player pickup but initiated by pet movement.
  """
  def handle_pet_item_pickup(packet, client_state) do
    with {:ok, character_pid} <- get_character(client_state),
         {:ok, character} <- Character.get_state(character_pid) do
      
      # Decode packet
      {_tick, packet} = In.decode_int(packet)
      {pet_slot, packet} = In.decode_byte(packet)
      {drop_oid, _packet} = In.decode_int(packet)

      Logger.debug("Pet item pickup attempt: character=#{character.name}, pet_slot=#{pet_slot}, drop_oid=#{drop_oid}")

      # Attempt to pick up the drop (pets have same rules but different animation)
      case attempt_pickup_drop(character, character_pid, drop_oid, client_state.channel_id, pet_slot) do
        {:ok, :meso, amount} ->
          Logger.debug("Pet picked up meso: #{amount}")
          {:ok, client_state}

        {:ok, :item, item} ->
          Logger.debug("Pet picked up item: #{item.item_id}")
          {:ok, client_state}

        {:error, _reason} ->
          {:ok, client_state}
      end
    else
      {:error, _reason} ->
        {:ok, client_state}
    end
  end

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

  defp attempt_pickup_drop(character, character_pid, drop_oid, channel_id, pet_slot \\ nil) do
    # Call Map.pickup_drop to atomically attempt pickup
    case Map.pickup_drop(character.map_id, channel_id, drop_oid, character.id) do
      {:ok, drop} ->
        # Successfully claimed the drop, now process it
        process_pickup(character, character_pid, drop, channel_id, pet_slot)

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

  defp process_pickup(character, character_pid, %Drop{} = drop, channel_id, pet_slot) do
    cond do
      Drop.meso?(drop) ->
        process_meso_pickup(character, character_pid, drop, channel_id, pet_slot)

      Drop.item?(drop) ->
        process_item_pickup(character, character_pid, drop, channel_id, pet_slot)

      true ->
        {:error, :invalid_drop}
    end
  end

  defp process_meso_pickup(character, character_pid, %Drop{meso: amount} = drop, channel_id, pet_slot) do
    # Add meso to character
    case Character.gain_meso(character_pid, amount, true) do
      {:ok, _new_meso} ->
        # Broadcast pickup animation to all players on map
        broadcast_pickup(character.map_id, channel_id, drop.oid, character.id, pet_slot)
        
        # Show meso gain in chat (optional)
        # send_meso_gain_message(client_state, amount)
        
        {:ok, :meso, amount}

      {:error, reason} ->
        Logger.warning("Failed to add meso: #{reason}")
        {:error, :gain_meso_failed}
    end
  end

  defp process_item_pickup(character, character_pid, %Drop{} = drop, channel_id, pet_slot) do
    # Check inventory space
    inventory_type = get_inventory_type(drop.item_id)
    
    case Character.check_inventory_space(character_pid, inventory_type, drop.quantity) do
      {:ok, _slot} ->
        # Add item to inventory
        item_to_add = drop.item || create_item_from_drop(drop)
        
        case Character.add_item_from_drop(character_pid, item_to_add) do
          {:ok, added_item} ->
            # Broadcast pickup animation
            broadcast_pickup(character.map_id, channel_id, drop.oid, character.id, pet_slot)
            
            {:ok, :item, added_item}

          {:error, reason} ->
            Logger.warning("Failed to add item to inventory: #{reason}")
            # Item couldn't be added - drop would normally be returned to map
            # but for simplicity we just fail
            {:error, :add_item_failed}
        end

      {:error, :inventory_full} ->
        # Send inventory full message to client
        {:error, :inventory_full}

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

  defp create_item_from_drop(%Drop{} = drop) do
    # Create a basic item struct from drop data
    %{
      item_id: drop.item_id,
      quantity: drop.quantity,
      position: 0  # Will be assigned by inventory
    }
  end

  defp get_inventory_type(item_id) do
    # Determine inventory type from item ID
    type_prefix = div(item_id, 1_000_000)
    
    case type_prefix do
      1 -> :equip
      2 -> :use
      3 -> :setup
      4 -> :etc
      5 -> :cash
      _ -> :etc
    end
  end

  defp broadcast_pickup(map_id, channel_id, drop_oid, character_id, nil) do
    # Player pickup - animation type 2
    remove_packet = Packets.remove_drop(drop_oid, 2, character_id)
    Map.broadcast(map_id, channel_id, remove_packet)
  end

  defp broadcast_pickup(map_id, channel_id, drop_oid, character_id, pet_slot) do
    # Pet pickup - animation type 5
    remove_packet = Packets.remove_drop(drop_oid, 5, character_id, pet_slot)
    Map.broadcast(map_id, channel_id, remove_packet)
  end

  defp send_pickup_result(client_state, _result, _item_id) do
    # Send inventory update or status packet
    # For now, just enable actions
    send_enable_actions(client_state)
  end

  defp send_enable_actions(client_state) do
    # Send enable actions packet to allow further client actions
    enable_packet = Packets.enable_actions()
    send_packet(client_state, enable_packet)
  end

  defp send_packet(client_state, data) when is_pid(client_state) do
    send(client_state, {:send_packet, data})
  end

  defp send_packet(client_state, data) do
    if client_state.client_pid do
      send(client_state.client_pid, {:send_packet, data})
    end
  end

  defp get_character(client_state) do
    case client_state.character_id do
      nil ->
        {:error, :no_character}

      character_id ->
        case Registry.lookup(Odinsea.CharacterRegistry, character_id) do
          [{pid, _}] -> {:ok, pid}
          [] -> {:error, :character_not_found}
        end
    end
  end
end