defmodule Odinsea.World.Party do
  @moduledoc """
  Party management service.
  Ported from src/handling/world/MapleParty.java
  
  Manages party state including members, leader, and operations.
  Supports cross-channel party functionality.
  """

  use GenServer

  require Logger

  alias Odinsea.Channel.Packets

  @max_party_size 6
  @loot_rules [:free_for_all, :round_robin, :master, :master_looter]

  # ============================================================================
  # Client API
  # ============================================================================

  def start_link(_) do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  @doc """
  Creates a new party with the given leader character.
  Returns {:ok, party_id} on success, {:error, reason} on failure.
  """
  def create_party(leader_character) do
    GenServer.call(__MODULE__, {:create_party, leader_character})
  end

  @doc """
  Creates a party linked to an expedition.
  """
  def create_expedition_party(leader_character, expedition_id) do
    GenServer.call(__MODULE__, {:create_expedition_party, leader_character, expedition_id})
  end

  @doc """
  Gets a party by ID.
  Returns the party struct or nil if not found.
  """
  def get_party(party_id) do
    GenServer.call(__MODULE__, {:get_party, party_id})
  end

  @doc """
  Updates party with a member operation (join, leave, expel, etc.).
  """
  def update_party(party_id, operation, character) do
    GenServer.call(__MODULE__, {:update_party, party_id, operation, character})
  end

  @doc """
  Disbands a party.
  """
  def disband_party(party_id, leader_id) do
    GenServer.call(__MODULE__, {:disband_party, party_id, leader_id})
  end

  @doc """
  Changes the party leader.
  """
  def change_leader(party_id, new_leader_id, current_leader_id) do
    GenServer.call(__MODULE__, {:change_leader, party_id, new_leader_id, current_leader_id})
  end

  @doc """
  Sets a character's online status in the party.
  """
  def set_online(party_id, character_id, online, channel) do
    GenServer.call(__MODULE__, {:set_online, party_id, character_id, online, channel})
  end

  @doc """
  Updates character info (level, job, map) for a party member.
  """
  def update_member(party_id, character) do
    GenServer.call(__MODULE__, {:update_member, party_id, character})
  end

  @doc """
  Gets all parties (for admin/debug purposes).
  """
  def get_all_parties do
    GenServer.call(__MODULE__, :get_all_parties)
  end

  @doc """
  Gets party members for broadcasting.
  Returns list of {character_id, channel} tuples.
  """
  def get_member_channels(party_id) do
    GenServer.call(__MODULE__, {:get_member_channels, party_id})
  end

  @doc """
  Broadcasts a packet to all party members except the sender.
  """
  def broadcast_to_party(party_id, packet, except_character_id \\ nil) do
    GenServer.cast(__MODULE__, {:broadcast_to_party, party_id, packet, except_character_id})
  end

  # ============================================================================
  # Server Callbacks
  # ============================================================================

  @impl true
  def init(_) do
    state = %{
      parties: %{},
      next_id: 1
    }

    Logger.info("Party service initialized")
    {:ok, state}
  end

  @impl true
  def handle_call({:create_party, leader}, _from, state) do
    party_id = state.next_id
    
    party = %{
      id: party_id,
      leader_id: leader.id,
      members: [create_party_character(leader)],
      expedition_id: -1,
      disbanded: false,
      loot_rule: :free_for_all,
      created_at: System.system_time(:second)
    }

    new_state = %{
      state
      | parties: Map.put(state.parties, party_id, party),
        next_id: party_id + 1
    }

    Logger.info("Party #{party_id} created by #{leader.name}")
    {:reply, {:ok, party}, new_state}
  end

  @impl true
  def handle_call({:create_expedition_party, leader, expedition_id}, _from, state) do
    party_id = state.next_id
    
    party = %{
      id: party_id,
      leader_id: leader.id,
      members: [create_party_character(leader)],
      expedition_id: expedition_id,
      disbanded: false,
      loot_rule: :free_for_all,
      created_at: System.system_time(:second)
    }

    new_state = %{
      state
      | parties: Map.put(state.parties, party_id, party),
        next_id: party_id + 1
    }

    Logger.info("Expedition party #{party_id} created for expedition #{expedition_id}")
    {:reply, {:ok, party}, new_state}
  end

  @impl true
  def handle_call({:get_party, party_id}, _from, state) do
    party = Map.get(state.parties, party_id)
    
    # Don't return disbanded parties
    if party && party.disbanded do
      {:reply, nil, state}
    else
      {:reply, party, state}
    end
  end

  @impl true
  def handle_call({:update_party, party_id, operation, character}, _from, state) do
    case Map.get(state.parties, party_id) do
      nil ->
        {:reply, {:error, :party_not_found}, state}

      party when party.disbanded ->
        {:reply, {:error, :party_disbanded}, state}

      party ->
        case apply_operation(party, operation, character) do
          {:ok, updated_party, result} ->
            new_state = %{state | parties: Map.put(state.parties, party_id, updated_party)}
            
            # Broadcast update to party members
            broadcast_party_update(updated_party, operation, character)
            
            {:reply, {:ok, result}, new_state}

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

  @impl true
  def handle_call({:disband_party, party_id, leader_id}, _from, state) do
    case Map.get(state.parties, party_id) do
      nil ->
        {:reply, {:error, :party_not_found}, state}

      %{leader_id: actual_leader} when actual_leader != leader_id ->
        {:reply, {:error, :not_leader}, state}

      party ->
        updated_party = %{party | disbanded: true, members: []}
        
        # Notify all members
        broadcast_party_disband(party)
        
        # Remove from state after a delay (for cleanup)
        :timer.apply_after(60_000, __MODULE__, :cleanup_party, [party_id])
        
        Logger.info("Party #{party_id} disbanded by leader #{leader_id}")
        {:reply, :ok, %{state | parties: Map.put(state.parties, party_id, updated_party)}}
    end
  end

  @impl true
  def handle_call({:change_leader, party_id, new_leader_id, current_leader_id}, _from, state) do
    case Map.get(state.parties, party_id) do
      nil ->
        {:reply, {:error, :party_not_found}, state}

      %{leader_id: actual_leader} when actual_leader != current_leader_id ->
        {:reply, {:error, :not_leader}, state}

      party ->
        # Check if new leader is in party
        unless Enum.any?(party.members, fn m -> m.id == new_leader_id end) do
          {:reply, {:error, :not_in_party}, state}
        else
          updated_party = %{party | leader_id: new_leader_id}
          
          broadcast_leader_changed(updated_party, new_leader_id)
          
          Logger.info("Party #{party_id} leader changed to #{new_leader_id}")
          {:reply, :ok, %{state | parties: Map.put(state.parties, party_id, updated_party)}}
        end
    end
  end

  @impl true
  def handle_call({:set_online, party_id, character_id, online, channel}, _from, state) do
    case Map.get(state.parties, party_id) do
      nil ->
        {:reply, {:error, :party_not_found}, state}

      party when party.disbanded ->
        {:reply, {:error, :party_disbanded}, state}

      party ->
        members = Enum.map(party.members, fn member ->
          if member.id == character_id do
            %{member | online: online, channel: channel}
          else
            member
          end
        end)

        updated_party = %{party | members: members}
        
        # Broadcast online status change
        broadcast_member_online(updated_party, character_id, online)
        
        {:reply, :ok, %{state | parties: Map.put(state.parties, party_id, updated_party)}}
    end
  end

  @impl true
  def handle_call({:update_member, party_id, character}, _from, state) do
    case Map.get(state.parties, party_id) do
      nil ->
        {:reply, {:error, :party_not_found}, state}

      party when party.disbanded ->
        {:reply, {:error, :party_disbanded}, state}

      party ->
        members = Enum.map(party.members, fn member ->
          if member.id == character.id do
            update_party_character(member, character)
          else
            member
          end
        end)

        updated_party = %{party | members: members}
        {:reply, :ok, %{state | parties: Map.put(state.parties, party_id, updated_party)}}
    end
  end

  @impl true
  def handle_call(:get_all_parties, _from, state) do
    active_parties = state.parties
    |> Map.values()
    |> Enum.reject(fn p -> p.disbanded end)
    
    {:reply, active_parties, state}
  end

  @impl true
  def handle_call({:get_member_channels, party_id}, _from, state) do
    case Map.get(state.parties, party_id) do
      nil -> {:reply, [], state}
      %{disbanded: true} -> {:reply, [], state}
      party ->
        channels = party.members
        |> Enum.filter(fn m -> m.online end)
        |> Enum.map(fn m -> {m.id, m.channel} end)
        {:reply, channels, state}
    end
  end

  @impl true
  def handle_cast({:broadcast_to_party, party_id, packet, except_id}, state) do
    case Map.get(state.parties, party_id) do
      nil -> :ok
      %{disbanded: true} -> :ok
      party ->
        # Broadcast to all online members except sender
        Enum.each(party.members, fn member ->
          if member.online && member.id != except_id do
            # Get character PID and send packet
            case Registry.lookup(Odinsea.CharacterRegistry, member.id) do
              [{pid, _}] -> send(pid, {:send_packet, packet})
              [] -> :ok
            end
          end
        end)
    end
    
    {:noreply, state}
  end

  # ============================================================================
  # Party Operations
  # ============================================================================

  defp apply_operation(party, :join, character) do
    if length(party.members) >= @max_party_size do
      {:error, :party_full}
    else
      # Check if already in party
      if Enum.any?(party.members, fn m -> m.id == character.id end) do
        {:error, :already_in_party}
      else
        party_char = create_party_character(character)
        updated_party = %{party | members: party.members ++ [party_char]}
        {:ok, updated_party, party_char}
      end
    end
  end

  defp apply_operation(party, :leave, character) do
    members = Enum.reject(party.members, fn m -> m.id == character.id end)
    
    # If leader leaves and there are other members, promote next member
    updated_party = if party.leader_id == character.id && length(members) > 0 do
      [new_leader | _] = members
      %{party | members: members, leader_id: new_leader.id}
    else
      %{party | members: members}
    end
    
    {:ok, updated_party, :ok}
  end

  defp apply_operation(party, :expel, character) do
    # Only leader can expel
    members = Enum.reject(party.members, fn m -> m.id == character.id end)
    updated_party = %{party | members: members}
    {:ok, updated_party, :ok}
  end

  defp apply_operation(party, :silent_update, character) do
    # Update member info without broadcasting
    members = Enum.map(party.members, fn member ->
      if member.id == character.id do
        update_party_character(member, character)
      else
        member
      end
    end)
    
    {:ok, %{party | members: members}, :ok}
  end

  defp apply_operation(party, :log_onoff, character) do
    members = Enum.map(party.members, fn member ->
      if member.id == character.id do
        %{member | online: character.online, channel: character.channel}
      else
        member
      end
    end)
    
    {:ok, %{party | members: members}, :ok}
  end

  defp apply_operation(_party, operation, _character) do
    {:error, {:unknown_operation, operation}}
  end

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

  defp create_party_character(character) do
    %{
      id: character.id,
      name: character.name,
      level: character.level,
      job: character.job,
      channel: character.channel_id || 1,
      map_id: character.map_id || 100000000,
      online: true,
      # Door info for mystic door skill
      door_town: 999999999,
      door_target: 999999999,
      door_skill: 0,
      door_x: 0,
      door_y: 0
    }
  end

  defp update_party_character(existing, character) do
    %{
      existing
      | level: character.level || existing.level,
        job: character.job || existing.job,
        channel: character.channel_id || existing.channel,
        map_id: character.map_id || existing.map_id
    }
  end

  defp broadcast_party_update(party, operation, character) do
    # Build party update packet and broadcast to members
    Enum.each(party.members, fn member ->
      if member.online && member.id != character.id do
        # Send party update packet
        case Registry.lookup(Odinsea.CharacterRegistry, member.id) do
          [{pid, _}] -> 
            packet = build_party_update_packet(party, operation, character)
            send(pid, {:send_packet, packet})
          [] -> :ok
        end
      end
    end)
  end

  defp broadcast_party_disband(party) do
    Enum.each(party.members, fn member ->
      if member.online do
        case Registry.lookup(Odinsea.CharacterRegistry, member.id) do
          [{pid, _}] -> 
            packet = build_party_disband_packet(party.id)
            send(pid, {:send_packet, packet})
          [] -> :ok
        end
      end
    end)
  end

  defp broadcast_leader_changed(party, new_leader_id) do
    Enum.each(party.members, fn member ->
      if member.online do
        case Registry.lookup(Odinsea.CharacterRegistry, member.id) do
          [{pid, _}] -> 
            packet = build_leader_change_packet(party.id, new_leader_id)
            send(pid, {:send_packet, packet})
          [] -> :ok
        end
      end
    end)
  end

  defp broadcast_member_online(party, character_id, online) do
    Enum.each(party.members, fn member ->
      if member.online && member.id != character_id do
        case Registry.lookup(Odinsea.CharacterRegistry, member.id) do
          [{pid, _}] -> 
            packet = build_member_online_packet(party.id, character_id, online)
            send(pid, {:send_packet, packet})
          [] -> :ok
        end
      end
    end)
  end

  # ============================================================================
  # Packet Builders (to be implemented in Channel.Packets)
  # ============================================================================

  defp build_party_update_packet(_party, _operation, _character) do
    # TODO: Implement party update packet
    # For now, return empty (needs proper packet structure)
    <<>>
  end

  defp build_party_disband_packet(_party_id) do
    # TODO: Implement party disband packet
    <<>>
  end

  defp build_leader_change_packet(_party_id, _new_leader_id) do
    # TODO: Implement leader change packet
    <<>>
  end

  defp build_member_online_packet(_party_id, _character_id, _online) do
    # TODO: Implement member online packet
    <<>>
  end

  @doc """
  Cleanup a disbanded party (called after delay).
  """
  def cleanup_party(party_id) do
    GenServer.cast(__MODULE__, {:cleanup_party, party_id})
  end

  @impl true
  def handle_cast({:cleanup_party, party_id}, state) do
    case Map.get(state.parties, party_id) do
      %{disbanded: true} ->
        {:noreply, %{state | parties: Map.delete(state.parties, party_id)}}
      _ ->
        {:noreply, state}
    end
  end
end