defmodule Odinsea.Scripting.EventInstance do
  @moduledoc """
  Event Instance Manager for individual event/quest instances.
  
  Each event instance represents a running copy of a party quest or event,
  with its own state, players, maps, and timers.
  
  ## State
  
  Event instances track:
  - Players registered to the event
  - Monsters spawned
  - Kill counts per player
  - Map instances (cloned maps for PQ)
  - Custom properties
  - Event timer
  
  ## Lifecycle
  
  1. EventManager creates instance via `new/3`
  2. Script `setup/2` is called
  3. Players register via `register_player/2`
  4. Event callbacks fire as things happen
  5. Instance disposes when complete or empty
  """

  require Logger

  alias Odinsea.Game.Character

  # ============================================================================
  # Types
  # ============================================================================

  @type t :: %__MODULE__{
    event_manager: Odinsea.Scripting.EventManager.t() | nil,
    name: String.t(),
    channel: integer(),
    players: [integer()],
    disconnected: [integer()],
    monsters: [integer()],
    kill_count: %{integer() => integer()},
    map_ids: [integer()],
    is_instanced: [boolean()],
    properties: %{String.t() => String.t()},
    timer_started: boolean(),
    time_started: integer() | nil,
    event_time: integer() | nil,
    disposed: boolean()
  }

  defstruct [
    :event_manager,
    :name,
    :channel,
    players: [],
    disconnected: [],
    monsters: [],
    kill_count: %{},
    map_ids: [],
    is_instanced: [],
    properties: %{},
    timer_started: false,
    time_started: nil,
    event_time: nil,
    disposed: false
  ]

  # ============================================================================
  # Constructor
  # ============================================================================

  @doc """
  Creates a new event instance.
  
  ## Parameters
    - `event_manager` - Parent EventManager
    - `name` - Unique instance name
    - `channel` - Channel number
  """
  @spec new(Odinsea.Scripting.EventManager.t() | nil, String.t(), integer()) :: t()
  def new(event_manager, name, channel) do
    %__MODULE__{
      event_manager: event_manager,
      name: name,
      channel: channel
    }
  end

  # ============================================================================
  # Player Management
  # ============================================================================

  @doc """
  Registers a player to this event instance.
  
  ## Parameters
    - `eim` - Event instance
    - `player` - Character struct or ID
  """
  @spec register_player(t(), Character.t() | integer()) :: t()
  def register_player(%{disposed: true} = eim, _), do: eim
  def register_player(eim, player) do
    char_id = case player do
      %{id: id} -> id
      id when is_integer(id) -> id
    end
    
    # Add to player list
    players = [char_id | eim.players] |> Enum.uniq()
    
    %{eim | players: players}
    |> call_callback(:player_entry, [player])
  end

  @doc """
  Unregisters a player from this event instance.
  """
  @spec unregister_player(t(), Character.t() | integer()) :: t()
  def unregister_player(%{disposed: true} = eim, _), do: eim
  def unregister_player(eim, player) do
    char_id = case player do
      %{id: id} -> id
      id when is_integer(id) -> id
    end
    
    players = List.delete(eim.players, char_id)
    
    %{eim | players: players}
  end

  @doc """
  Handles player changing maps.
  """
  @spec changed_map(t(), Character.t() | integer(), integer()) :: t()
  def changed_map(%{disposed: true} = eim, _, _), do: eim
  def changed_map(eim, player, map_id) do
    call_callback(eim, :changed_map, [player, map_id])
  end

  @doc """
  Handles player death.
  """
  @spec player_killed(t(), Character.t() | integer()) :: t()
  def player_killed(%{disposed: true} = eim, _), do: eim
  def player_killed(eim, player) do
    call_callback(eim, :player_dead, [player])
  end

  @doc """
  Handles player revive request.
  
  ## Returns
    - `{allow_revive :: boolean(), updated_eim}`
  """
  @spec revive_player(t(), Character.t() | integer()) :: {boolean(), t()}
  def revive_player(%{disposed: true} = eim, _), do: {true, eim}
  def revive_player(eim, player) do
    result = call_callback_result(eim, :player_revive, [player])
    allow = if is_boolean(result), do: result, else: true
    {allow, eim}
  end

  @doc """
  Handles player disconnection.
  
  ## Returns
    - `{:dispose, eim}` - Dispose instance
    - `{:continue, eim}` - Continue running
  """
  @spec player_disconnected(t(), Character.t() | integer()) :: {:dispose | :continue, t()}
  def player_disconnected(%{disposed: true} = eim, _), do: {:dispose, eim}
  def player_disconnected(eim, player) do
    char_id = case player do
      %{id: id} -> id
      id when is_integer(id) -> id
    end
    
    # Add to disconnected list
    disconnected = [char_id | eim.disconnected]
    eim = %{eim | disconnected: disconnected}
    
    # Remove from players
    eim = unregister_player(eim, player)
    
    # Call callback to determine behavior
    result = call_callback_result(eim, :player_disconnected, [player])
    
    action = case result do
      0 ->
        # Dispose if no players
        if length(eim.players) == 0, do: :dispose, else: :continue
      
      x when x > 0 ->
        # Dispose if less than x players
        if length(eim.players) < x, do: :dispose, else: :continue
      
      x when x < 0 ->
        # Dispose if less than |x| players, or if leader disconnected
        threshold = abs(x)
        if length(eim.players) < threshold do
          :dispose
        else
          # TODO: Check if leader disconnected
          :continue
        end
      
      _ ->
        :continue
    end
    
    {action, eim}
  end

  @doc """
  Removes disconnected player ID from tracking.
  """
  @spec remove_disconnected(t(), integer()) :: t()
  def remove_disconnected(eim, char_id) do
    disconnected = List.delete(eim.disconnected, char_id)
    %{eim | disconnected: disconnected}
  end

  @doc """
  Checks if a player is disconnected.
  """
  @spec is_disconnected?(t(), integer()) :: boolean()
  def is_disconnected?(eim, char_id) do
    char_id in eim.disconnected
  end

  # ============================================================================
  # Party Management
  # ============================================================================

  @doc """
  Registers an entire party to the event.
  """
  @spec register_party(t(), term(), integer()) :: t()
  def register_party(%{disposed: true} = eim, _, _), do: eim
  def register_party(eim, party, map_id) do
    # TODO: Get party members and register each
    eim
  end

  @doc """
  Registers a squad (expedition) to the event.
  """
  @spec register_squad(t(), term(), integer(), integer()) :: t()
  def register_squad(%{disposed: true} = eim, _, _, _), do: eim
  def register_squad(eim, squad, map_id, quest_id) do
    # TODO: Register squad members
    eim
  end

  @doc """
  Handles player leaving party.
  """
  @spec left_party(t(), Character.t() | integer()) :: t()
  def left_party(%{disposed: true} = eim, _), do: eim
  def left_party(eim, player) do
    call_callback(eim, :left_party, [player])
  end

  @doc """
  Handles party disbanding.
  """
  @spec disband_party(t()) :: t()
  def disband_party(%{disposed: true} = eim), do: eim
  def disband_party(eim) do
    call_callback(eim, :disband_party, [])
  end

  # ============================================================================
  # Monster Management
  # ============================================================================

  @doc """
  Registers a monster to this event.
  """
  @spec register_monster(t(), integer()) :: t()
  def register_monster(%{disposed: true} = eim, _), do: eim
  def register_monster(eim, mob_id) do
    monsters = [mob_id | eim.monsters]
    %{eim | monsters: monsters}
  end

  @doc """
  Unregisters a monster when killed.
  """
  @spec unregister_monster(t(), integer()) :: t()
  def unregister_monster(%{disposed: true} = eim, _), do: eim
  def unregister_monster(eim, mob_id) do
    monsters = List.delete(eim.monsters, mob_id)
    eim = %{eim | monsters: monsters}
    
    # If no monsters left, call allMonstersDead
    if length(monsters) == 0 do
      call_callback(eim, :all_monsters_dead, [])
    else
      eim
    end
  end

  @doc """
  Records monster kill and distributes points.
  """
  @spec monster_killed(t(), Character.t() | integer(), integer()) :: t()
  def monster_killed(%{disposed: true} = eim, _, _), do: eim
  def monster_killed(eim, player, mob_id) do
    # Get monster value from script
    inc = call_callback_result(eim, :monster_value, [mob_id])
    inc = if is_integer(inc), do: inc, else: 0
    
    # Update kill count
    char_id = case player do
      %{id: id} -> id
      id when is_integer(id) -> id
    end
    
    current = Map.get(eim.kill_count, char_id, 0)
    kill_count = Map.put(eim.kill_count, char_id, current + inc)
    
    %{eim | kill_count: kill_count}
  end

  @doc """
  Gets kill count for a player.
  """
  @spec get_kill_count(t(), integer()) :: integer()
  def get_kill_count(eim, char_id) do
    Map.get(eim.kill_count, char_id, 0)
  end

  # ============================================================================
  # Timer Management
  # ============================================================================

  @doc """
  Starts/restarts the event timer.
  
  ## Parameters
    - `eim` - Event instance
    - `time_ms` - Time in milliseconds
  """
  @spec start_event_timer(t(), integer()) :: t()
  def start_event_timer(eim, time_ms) do
    restart_event_timer(eim, time_ms)
  end

  @doc """
  Restarts the event timer.
  """
  @spec restart_event_timer(t(), integer()) :: t()
  def restart_event_timer(%{disposed: true} = eim, _), do: eim
  def restart_event_timer(eim, time_ms) do
    # Send clock packet to all players
    time_seconds = div(time_ms, 1000)
    broadcast_packet(eim, {:clock, time_seconds})
    
    # Schedule timeout
    if eim.event_manager do
      Odinsea.Scripting.EventManager.schedule(
        eim,
        "scheduledTimeout",
        time_ms
      )
    end
    
    %{eim |
      timer_started: true,
      time_started: System.system_time(:millisecond),
      event_time: time_ms
    }
  end

  @doc """
  Stops the event timer.
  """
  @spec stop_event_timer(t()) :: t()
  def stop_event_timer(eim) do
    %{eim |
      timer_started: false,
      time_started: nil,
      event_time: nil
    }
  end

  @doc """
  Checks if timer is started.
  """
  @spec is_timer_started?(t()) :: boolean()
  def is_timer_started?(eim) do
    eim.timer_started && eim.time_started != nil
  end

  @doc """
  Gets time remaining in milliseconds.
  """
  @spec get_time_left(t()) :: integer()
  def get_time_left(eim) do
    if is_timer_started?(eim) do
      elapsed = System.system_time(:millisecond) - eim.time_started
      max(0, eim.event_time - elapsed)
    else
      0
    end
  end

  @doc """
  Schedules a custom method callback.
  """
  @spec schedule(t(), String.t(), integer()) :: reference()
  def schedule(eim, method_name, delay_ms) do
    if eim.event_manager do
      Odinsea.Scripting.EventManager.schedule(eim, method_name, delay_ms)
    else
      nil
    end
  end

  # ============================================================================
  # Map Instance Management
  # ============================================================================

  @doc """
  Creates an instanced map (clone for PQ).
  
  ## Returns
    - `{map_instance_id, updated_eim}`
  """
  @spec create_instance_map(t(), integer()) :: {integer(), t()}
  def create_instance_map(%{disposed: true} = eim, _), do: {0, eim}
  def create_instance_map(eim, map_id) do
    assigned_id = get_new_instance_map_id()
    
    # TODO: Create actual map instance
    # For now, just track the ID
    eim = %{eim |
      map_ids: [assigned_id | eim.map_ids],
      is_instanced: [true | eim.is_instanced]
    }
    
    {assigned_id, eim}
  end

  @doc """
  Creates an instanced map with simplified settings.
  """
  @spec create_instance_map_s(t(), integer()) :: {integer(), t()}
  def create_instance_map_s(eim, map_id) do
    create_instance_map(eim, map_id)
  end

  @doc """
  Sets an existing map as part of this event.
  """
  @spec set_instance_map(t(), integer()) :: t()
  def set_instance_map(%{disposed: true} = eim, _), do: eim
  def set_instance_map(eim, map_id) do
    %{eim |
      map_ids: [map_id | eim.map_ids],
      is_instanced: [false | eim.is_instanced]
    }
  end

  @doc """
  Gets a map instance by index.
  """
  @spec get_map_instance(t(), integer()) :: term()
  def get_map_instance(eim, index) when index < length(eim.map_ids) do
    map_id = Enum.at(eim.map_ids, index)
    is_instanced = Enum.at(eim.is_instanced, index)
    
    # TODO: Return actual map
    %{id: map_id, instanced: is_instanced}
  end
  def get_map_instance(eim, map_id) when is_integer(map_id) do
    # Assume it's a real map ID
    %{id: map_id, instanced: false}
  end

  # ============================================================================
  # Properties
  # ============================================================================

  @doc """
  Sets a property on this instance.
  """
  @spec set_property(t(), String.t(), String.t()) :: t()
  def set_property(%{disposed: true} = eim, _, _), do: eim
  def set_property(eim, key, value) do
    properties = Map.put(eim.properties, key, value)
    %{eim | properties: properties}
  end

  @doc """
  Gets a property value.
  """
  @spec get_property(t(), String.t()) :: String.t() | nil
  def get_property(eim, key) do
    Map.get(eim.properties, key)
  end

  # ============================================================================
  # Player Actions
  # ============================================================================

  @doc """
  Removes a player from the event (warp out).
  """
  @spec remove_player(t(), Character.t() | integer()) :: t()
  def remove_player(%{disposed: true} = eim, _), do: eim
  def remove_player(eim, player) do
    call_callback(eim, :player_exit, [player])
  end

  @doc """
  Finishes the party quest.
  """
  @spec finish_pq(t()) :: t()
  def finish_pq(%{disposed: true} = eim), do: eim
  def finish_pq(eim) do
    call_callback(eim, :clear_pq, [])
  end

  @doc """
  Awards achievement to all players.
  """
  @spec give_achievement(t(), integer()) :: :ok
  def give_achievement(eim, type) do
    broadcast_to_players(eim, {:achievement, type})
    :ok
  end

  @doc """
  Broadcasts a message to all players in the event.
  """
  @spec broadcast_player_msg(t(), integer(), String.t()) :: :ok
  def broadcast_player_msg(eim, type, message) do
    broadcast_to_players(eim, {:message, type, message})
    :ok
  end

  @doc """
  Broadcasts a raw packet to all players.
  """
  @spec broadcast_packet(t(), term()) :: :ok
  def broadcast_packet(eim, packet) do
    Enum.each(eim.players, fn char_id ->
      # TODO: Send packet to player
      :ok
    end)
  end

  @doc """
  Broadcasts packet to team members.
  """
  @spec broadcast_team_packet(t(), term(), integer()) :: :ok
  def broadcast_team_packet(eim, packet, team) do
    # TODO: Filter by team and send
    :ok
  end

  @doc """
  Applies buff to a player.
  """
  @spec apply_buff(t(), Character.t() | integer(), integer()) :: :ok
  def apply_buff(eim, player, buff_id) do
    # TODO: Apply item effect
    :ok
  end

  @doc """
  Applies skill to a player.
  """
  @spec apply_skill(t(), Character.t() | integer(), integer()) :: :ok
  def apply_skill(eim, player, skill_id) do
    # TODO: Apply skill effect
    :ok
  end

  # ============================================================================
  # Carnival Party (CPQ)
  # ============================================================================

  @doc """
  Registers a carnival party.
  """
  @spec register_carnival_party(t(), term()) :: t()
  def register_carnival_party(%{disposed: true} = eim, _), do: eim
  def register_carnival_party(eim, carnival_party) do
    call_callback(eim, :register_carnival_party, [carnival_party])
  end

  # ============================================================================
  # Disposal
  # ============================================================================

  @doc """
  Disposes the event instance if player count is at or below threshold.
  
  ## Returns
    - `{true, eim}` - Instance was disposed
    - `{false, eim}` - Instance not disposed
  """
  @spec dispose_if_player_below(t(), integer(), integer()) :: {boolean(), t()}
  def dispose_if_player_below(%{disposed: true} = eim, _, _), do: {true, eim}
  def dispose_if_player_below(eim, size, warp_map_id) do
    if length(eim.players) <= size do
      # Warp players if map specified
      if warp_map_id > 0 do
        # TODO: Warp all players
      end
      
      {true, dispose(eim)}
    else
      {false, eim}
    end
  end

  @doc """
  Disposes the event instance.
  """
  @spec dispose(t()) :: t()
  def dispose(%{disposed: true} = eim), do: eim
  def dispose(eim) do
    # Clear player event instances
    Enum.each(eim.players, fn char_id ->
      # TODO: Clear player's event instance reference
      :ok
    end)
    
    # Remove instanced maps
    Enum.zip(eim.map_ids, eim.is_instanced)
    |> Enum.each(fn {map_id, instanced} ->
      if instanced do
        # TODO: Remove instance map
        :ok
      end
    end)
    
    # Notify event manager
    if eim.event_manager do
      Odinsea.Scripting.EventManager.dispose_instance(eim.name)
    end
    
    %{eim |
      disposed: true,
      players: [],
      monsters: [],
      kill_count: %{},
      map_ids: [],
      is_instanced: []
    }
  end

  # ============================================================================
  # Utility
  # ============================================================================

  @doc """
  Checks if player is the leader.
  """
  @spec is_leader?(t(), Character.t() | integer()) :: boolean()
  def is_leader?(_eim, _player) do
    # TODO: Check party leadership
    false
  end

  @doc """
  Gets player count.
  """
  @spec get_player_count(t()) :: integer()
  def get_player_count(%{disposed: true}), do: 0
  def get_player_count(eim), do: length(eim.players)

  @doc """
  Gets the list of players.
  """
  @spec get_players(t()) :: [integer()]
  def get_players(%{disposed: true}), do: []
  def get_players(eim), do: eim.players

  @doc """
  Gets the list of monsters.
  """
  @spec get_mobs(t()) :: [integer()]
  def get_mobs(eim), do: eim.monsters

  @doc """
  Handles map load event.
  """
  @spec on_map_load(t(), Character.t() | integer()) :: t()
  def on_map_load(%{disposed: true} = eim, _), do: eim
  def on_map_load(eim, player) do
    call_callback(eim, :on_map_load, [player])
  end

  @doc """
  Creates a new pair list (utility for scripts).
  """
  @spec new_pair() :: list()
  def new_pair(), do: []

  @doc """
  Adds to a pair list.
  """
  @spec add_to_pair(list(), term(), term()) :: list()
  def add_to_pair(list, key, value) do
    [{key, value} | list]
  end

  @doc """
  Creates a new character pair list.
  """
  @spec new_pair_chr() :: list()
  def new_pair_chr(), do: []

  @doc """
  Adds to a character pair list.
  """
  @spec add_to_pair_chr(list(), term(), term()) :: list()
  def add_to_pair_chr(list, key, value) do
    [{key, value} | list]
  end

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

  defp call_callback(%{disposed: true} = eim, _method, _args), do: eim
  defp call_callback(eim, method, args) do
    if eim.event_manager && eim.event_manager.script_module do
      mod = eim.event_manager.script_module
      
      if function_exported?(mod, method, length(args) + 1) do
        try do
          apply(mod, method, [eim | args])
        rescue
          e -> 
            Logger.error("Event callback #{method} error: #{inspect(e)}")
            eim
        end
      else
        eim
      end
    else
      eim
    end
  end

  defp call_callback_result(eim, method, args) do
    if eim.event_manager && eim.event_manager.script_module do
      mod = eim.event_manager.script_module
      
      if function_exported?(mod, method, length(args) + 1) do
        try do
          apply(mod, method, [eim | args])
        rescue
          e -> 
            Logger.error("Event callback #{method} error: #{inspect(e)}")
            nil
        end
      else
        nil
      end
    else
      nil
    end
  end

  defp broadcast_to_players(_eim, _message) do
    # TODO: Implement broadcasting
    :ok
  end

  # Global counter for instance map IDs
  defp get_new_instance_map_id() do
    # Use persistent_term or similar for atomic increment
    :counters.add(:instance_counter, 1, 1)
  rescue
    _ -> 
      # Fallback if counter doesn't exist
      System.unique_integer([:positive])
  end
end