defmodule Odinsea.Channel.Handler.Buddy do
  @moduledoc """
  Handles buddy list operations.
  Ported from src/handling/channel/handler/BuddyListHandler.java
  
  Manages buddy list add, remove, and accept operations.
  """

  require Logger

  alias Odinsea.Net.Packet.In
  alias Odinsea.Channel.Packets
  alias Odinsea.Game.Character
  alias Odinsea.Database.Context

  @max_buddy_list 100
  @default_capacity 20

  @doc """
  Handles buddy list operations (CP_BUDDYLIST_MODIFY).
  Ported from BuddyListHandler.BuddyOperation()
  
  Mode:
  - 1: Add buddy
  - 2: Accept buddy
  - 3: Delete buddy
  """
  def handle_buddy_operation(packet, client_state) do
    with {:ok, character_pid} <- get_character(client_state),
         {:ok, character} <- Character.get_state(character_pid) do
      
      {mode, packet} = In.decode_byte(packet)
      
      case mode do
        1 -> handle_add_buddy(packet, character, client_state)
        2 -> handle_accept_buddy(packet, character, client_state)
        3 -> handle_delete_buddy(packet, character, client_state)
        _ -> 
          Logger.warning("Unknown buddy operation mode: #{mode}")
          {:ok, client_state}
      end
    else
      {:error, reason} ->
        Logger.warning("Buddy operation failed: #{inspect(reason)}")
        {:ok, client_state}
    end
  end

  # ============================================================================
  # Add Buddy Handler
  # ============================================================================

  defp handle_add_buddy(packet, character, client_state) do
    {add_name, packet} = In.decode_string(packet)
    {group_name, _packet} = In.decode_string(packet)
    
    # Validate inputs
    if String.length(add_name) > 13 || String.length(group_name) > 16 do
      {:ok, client_state}
    else
      # Check if already in buddy list
      existing = find_buddy(character.buddies, add_name)
      
      cond do
        existing && existing.group == group_name ->
          # Already in list with same group
          send_buddy_message(client_state, 11)
          
        existing && !existing.pending ->
          # Update group
          updated_buddies = update_buddy_group(character.buddies, add_name, group_name)
          Character.update_buddies(character.id, updated_buddies)
          
          # Send updated buddy list
          buddy_list_packet = Packets.update_buddylist(updated_buddies, 10)
          send_packet(client_state, buddy_list_packet)
          
        length(character.buddies) >= @max_buddy_list ->
          # Buddy list full
          send_buddy_message(client_state, 11)
          
        true ->
          # Try to find and add buddy
          add_buddy_to_list(add_name, group_name, character, client_state)
      end
      
      {:ok, client_state}
    end
  end

  defp add_buddy_to_list(add_name, group_name, character, client_state) do
    # Try to find character on current channel
    case Odinsea.Channel.Players.find_by_name(client_state.channel_id, add_name) do
      {:ok, target_character} ->
        # Check if can add (not GM hiding, not blacklisted)
        if can_add_buddy?(character, target_character) do
          # Check target's buddy list capacity
          if length(target_character.buddies) >= @default_capacity do
            send_buddy_message(client_state, 12)
          else
            # Send buddy request to target
            send_buddy_request(target_character, character)
            
            # Add pending buddy to our list
            buddy = create_buddy_entry(target_character, group_name, -1, true)
            updated_buddies = character.buddies ++ [buddy]
            Character.update_buddies(character.id, updated_buddies)
            
            # Send updated buddy list
            buddy_list_packet = Packets.update_buddylist(updated_buddies, 10)
            send_packet(client_state, buddy_list_packet)
          end
        else
          send_buddy_message(client_state, 15)
        end
        
      {:error, :not_found} ->
        # Try to find in database
        case Context.get_character_by_name(add_name) do
          nil ->
            send_buddy_message(client_state, 15)
            
          target_db ->
            # Check if target can accept buddy
            if target_db.gm_level < 3 do
              # Check buddy capacity in database
              case get_buddy_count_from_db(target_db.id) do
                {:ok, count} when count >= @default_capacity ->
                  send_buddy_message(client_state, 12)
                  
                _ ->
                  # Add pending to database
                  insert_pending_buddy(target_db.id, character.id, group_name)
                  
                  # Add pending buddy to our list
                  buddy = create_buddy_entry_from_db(target_db, group_name, true)
                  updated_buddies = character.buddies ++ [buddy]
                  Character.update_buddies(character.id, updated_buddies)
                  
                  # Send updated buddy list
                  buddy_list_packet = Packets.update_buddylist(updated_buddies, 10)
                  send_packet(client_state, buddy_list_packet)
              end
            else
              send_buddy_message(client_state, 15)
            end
        end
    end
  end

  # ============================================================================
  # Accept Buddy Handler
  # ============================================================================

  defp handle_accept_buddy(packet, character, client_state) do
    {other_cid, _packet} = In.decode_int(packet)
    
    # Find pending buddy
    buddy = Enum.find(character.buddies, fn b -> 
      b.character_id == other_cid && b.pending 
    end)
    
    if buddy && length(character.buddies) < @max_buddy_list do
      # Accept the buddy
      updated_buddy = %{buddy | pending: false, visible: true, group: "ETC"}
      
      # Update buddy in list
      updated_buddies = Enum.map(character.buddies, fn b ->
        if b.character_id == other_cid do
          updated_buddy
        else
          b
        end
      end)
      
      Character.update_buddies(character.id, updated_buddies)
      
      # Try to find channel
      channel = find_buddy_channel(other_cid)
      
      # Send updated buddy list
      buddy_list_packet = Packets.update_buddylist(updated_buddies, 10)
      send_packet(client_state, buddy_list_packet)
      
      # Notify other player if online
      if channel > 0 do
        notify_buddy_added(other_cid, character, "ETC")
      end
      
      # Update in database
      accept_buddy_in_db(character.id, other_cid)
    else
      send_buddy_message(client_state, 11)
    end
    
    {:ok, client_state}
  end

  # ============================================================================
  # Delete Buddy Handler
  # ============================================================================

  defp handle_delete_buddy(packet, character, client_state) do
    {other_cid, _packet} = In.decode_int(packet)
    
    # Find buddy
    buddy = Enum.find(character.buddies, fn b -> b.character_id == other_cid end)
    
    if buddy do
      # Notify other player if online and visible
      if buddy.visible do
        channel = find_buddy_channel(other_cid)
        if channel > 0 do
          notify_buddy_removed(other_cid, character.id)
        end
      end
      
      # Remove from our list
      updated_buddies = Enum.reject(character.buddies, fn b -> 
        b.character_id == other_cid 
      end)
      
      Character.update_buddies(character.id, updated_buddies)
      
      # Send updated buddy list
      buddy_list_packet = Packets.update_buddylist(updated_buddies, 18)
      send_packet(client_state, buddy_list_packet)
      
      # Remove from database
      remove_buddy_from_db(character.id, other_cid)
    end
    
    {:ok, client_state}
  end

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

  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

  defp find_buddy(buddies, name) do
    name_lower = String.downcase(name)
    Enum.find(buddies, fn b -> 
      String.downcase(b.name) == name_lower 
    end)
  end

  defp update_buddy_group(buddies, name, group_name) do
    Enum.map(buddies, fn b ->
      if String.downcase(b.name) == String.downcase(name) do
        %{b | group: group_name}
      else
        b
      end
    end)
  end

  defp can_add_buddy?(character, target) do
    # Check if target is GM hiding
    if target.gm? && !character.gm? do
      false
    else
      # Check blacklist
      target_character = 
        case Registry.lookup(Odinsea.CharacterRegistry, target.id) do
          [{pid, _}] -> 
            case Character.get_state(pid) do
              {:ok, state} -> state
              _ -> nil
            end
          [] -> nil
        end
      
      if target_character do
        not Enum.member?(target_character.blacklist, String.downcase(character.name))
      else
        true
      end
    end
  end

  defp create_buddy_entry(character, group, channel, pending) do
    %{
      character_id: character.id,
      name: character.name,
      group: group,
      channel: channel,
      visible: !pending,
      pending: pending,
      level: character.level,
      job: character.job
    }
  end

  defp create_buddy_entry_from_db(character, group, pending) do
    %{
      character_id: character.id,
      name: character.name,
      group: group,
      channel: -1,
      visible: !pending,
      pending: pending,
      level: character.level,
      job: character.job
    }
  end

  defp send_buddy_request(target_character, from_character) do
    case Registry.lookup(Odinsea.CharacterRegistry, target_character.id) do
      [{pid, _}] ->
        request_packet = Packets.request_buddylist_add(
          from_character.id,
          from_character.name,
          from_character.level,
          from_character.job
        )
        send(pid, {:send_packet, request_packet})
      [] -> :ok
    end
  end

  defp notify_buddy_added(target_id, from_character, group) do
    case Registry.lookup(Odinsea.CharacterRegistry, target_id) do
      [{pid, _}] ->
        # Add buddy entry for target
        buddy_entry = create_buddy_entry(from_character, group, 1, false)
        
        # Update target's buddies
        case Character.get_state(pid) do
          {:ok, target_state} ->
            updated_buddies = target_state.buddies ++ [buddy_entry]
            Character.update_buddies(target_id, updated_buddies)
            
            # Send update packet
            buddy_list_packet = Packets.update_buddylist(updated_buddies, 10)
            send(pid, {:send_packet, buddy_list_packet})
          _ -> :ok
        end
      [] -> :ok
    end
  end

  defp notify_buddy_removed(target_id, remover_id) do
    case Registry.lookup(Odinsea.CharacterRegistry, target_id) do
      [{pid, _}] ->
        case Character.get_state(pid) do
          {:ok, target_state} ->
            updated_buddies = Enum.reject(target_state.buddies, fn b -> 
              b.character_id == remover_id 
            end)
            
            Character.update_buddies(target_id, updated_buddies)
            
            buddy_list_packet = Packets.update_buddylist(updated_buddies, 18)
            send(pid, {:send_packet, buddy_list_packet})
          _ -> :ok
        end
      [] -> :ok
    end
  end

  defp find_buddy_channel(character_id) do
    # Try to find character on any channel
    # For now, just check current channel's registry
    case Registry.lookup(Odinsea.CharacterRegistry, character_id) do
      [{_pid, _}] -> 1  # Found, return channel
      [] -> -1  # Not found
    end
  end

  defp send_buddy_message(client_state, code) do
    packet = Packets.buddylist_message(code)
    send_packet(client_state, packet)
  end

  defp send_packet(client_state, packet) do
    if client_state.socket do
      :gen_tcp.send(client_state.socket, packet)
    end
  end

  # ============================================================================
  # Database Functions (Stubs)
  # ============================================================================

  defp get_buddy_count_from_db(character_id) do
    # TODO: Query buddies table for count
    {:ok, 0}
  end

  defp insert_pending_buddy(target_id, character_id, group_name) do
    # TODO: Insert pending buddy into database
    Logger.debug("Insert pending buddy: target=#{target_id}, from=#{character_id}, group=#{group_name}")
    :ok
  end

  defp accept_buddy_in_db(character_id, other_id) do
    # TODO: Update buddy status in database
    Logger.debug("Accept buddy in DB: #{character_id} <-> #{other_id}")
    :ok
  end

  defp remove_buddy_from_db(character_id, other_id) do
    # TODO: Remove buddy from database
    Logger.debug("Remove buddy from DB: #{character_id} X #{other_id}")
    :ok
  end
end