defmodule Odinsea.Game.ReactorStats do
  @moduledoc """
  Represents reactor template stats (state machine data).
  
  Contains the state definitions for a reactor type.
  Each state defines: type, next state, required item, timeout, touch mode.
  
  Ported from Java: src/server/maps/MapleReactorStats.java
  """

  defmodule Point do
    @moduledoc "Simple 2D point for area bounds"
    @type t :: %__MODULE__{x: integer(), y: integer()}
    defstruct [:x, :y]
  end

  defmodule StateData do
    @moduledoc "State definition for a reactor"
    @type t :: %__MODULE__{
      type: integer(),              # State type (determines behavior)
      next_state: integer(),        # Next state index (-1 = end)
      react_item: {integer(), integer()} | nil,  # {item_id, quantity} required
      timeout: integer(),           # Timeout in ms before auto-advance (-1 = none)
      can_touch: integer()          # 0 = hit only, 1 = click/touch, 2 = touch only
    }
    defstruct [
      :type,
      :next_state,
      :react_item,
      timeout: -1,
      can_touch: 0
    ]
  end

  @typedoc "Reactor stats struct"
  @type t :: %__MODULE__{
    tl: Point.t() | nil,           # Top-left corner of area (for item-triggered)
    br: Point.t() | nil,           # Bottom-right corner of area
    states: %{integer() => StateData.t()},  # State definitions by state number
    activate_by_touch: boolean()   # Whether reactor activates by touch
  }

  defstruct [
    :tl,
    :br,
    states: %{},
    activate_by_touch: false
  ]

  @doc """
  Creates a new empty reactor stats.
  """
  @spec new() :: t()
  def new do
    %__MODULE__{}
  end

  @doc """
  Sets the top-left point of the area.
  """
  @spec set_tl(t(), integer(), integer()) :: t()
  def set_tl(stats, x, y) do
    %{stats | tl: %Point{x: x, y: y}}
  end

  @doc """
  Sets the bottom-right point of the area.
  """
  @spec set_br(t(), integer(), integer()) :: t()
  def set_br(stats, x, y) do
    %{stats | br: %Point{x: x, y: y}}
  end

  @doc """
  Sets whether reactor activates by touch.
  """
  @spec set_activate_by_touch(t(), boolean()) :: t()
  def set_activate_by_touch(stats, activate) do
    %{stats | activate_by_touch: activate}
  end

  @doc """
  Adds a state definition.
  
  ## Parameters
  - stats: the reactor stats struct
  - state_num: the state number (byte value)
  - type: the state type (determines behavior)
  - react_item: {item_id, quantity} or nil
  - next_state: the next state number (-1 for end)
  - timeout: timeout in ms (-1 for none)
  - can_touch: 0 = hit only, 1 = click, 2 = touch only
  """
  @spec add_state(
    t(),
    integer(),
    integer(),
    {integer(), integer()} | nil,
    integer(),
    integer(),
    integer()
  ) :: t()
  def add_state(stats, state_num, type, react_item, next_state, timeout, can_touch) do
    state_data = %StateData{
      type: type,
      react_item: react_item,
      next_state: next_state,
      timeout: timeout,
      can_touch: can_touch
    }
    
    %{stats | states: Map.put(stats.states, state_num, state_data)}
  end

  @doc """
  Gets the next state for a given current state.
  Returns -1 if not found.
  """
  @spec get_next_state(t(), integer()) :: integer()
  def get_next_state(stats, state) do
    case Map.get(stats.states, state) do
      nil -> -1
      state_data -> state_data.next_state
    end
  end

  @doc """
  Gets the type for a given state.
  Returns -1 if not found.
  """
  @spec get_type(t(), integer()) :: integer()
  def get_type(stats, state) do
    case Map.get(stats.states, state) do
      nil -> -1
      state_data -> state_data.type
    end
  end

  @doc """
  Gets the react item for a given state.
  Returns nil if not found.
  """
  @spec get_react_item(t(), integer()) :: {integer(), integer()} | nil
  def get_react_item(stats, state) do
    case Map.get(stats.states, state) do
      nil -> nil
      state_data -> state_data.react_item
    end
  end

  @doc """
  Gets the timeout for a given state.
  Returns -1 if not found.
  """
  @spec get_timeout(t(), integer()) :: integer()
  def get_timeout(stats, state) do
    case Map.get(stats.states, state) do
      nil -> -1
      state_data -> state_data.timeout
    end
  end

  @doc """
  Gets the touch mode for a given state.
  Returns 0 if not found.
  
  Modes:
  - 0: Hit only (weapon attack)
  - 1: Click/touch (interact button)
  - 2: Touch only (walk into)
  """
  @spec can_touch(t(), integer()) :: integer()
  def can_touch(stats, state) do
    case Map.get(stats.states, state) do
      nil -> 0
      state_data -> state_data.can_touch
    end
  end

  @doc """
  Gets all state numbers defined for this reactor.
  """
  @spec get_state_numbers(t()) :: [integer()]
  def get_state_numbers(stats) do
    Map.keys(stats.states) |> Enum.sort()
  end

  @doc """
  Checks if a state exists.
  """
  @spec has_state?(t(), integer()) :: boolean()
  def has_state?(stats, state) do
    Map.has_key?(stats.states, state)
  end

  @doc """
  Gets the state data for a given state number.
  """
  @spec get_state_data(t(), integer()) :: StateData.t() | nil
  def get_state_data(stats, state) do
    Map.get(stats.states, state)
  end

  @doc """
  Builds reactor stats from JSON data.
  """
  @spec from_json(map()) :: t()
  def from_json(data) do
    stats = new()
    
    # Set activate by touch
    stats = set_activate_by_touch(stats, data["activate_by_touch"] == true)
    
    # Set area bounds if present
    stats = 
      if data["tl"] do
        set_tl(stats, data["tl"]["x"] || 0, data["tl"]["y"] || 0)
      else
        stats
      end
    
    stats = 
      if data["br"] do
        set_br(stats, data["br"]["x"] || 0, data["br"]["y"] || 0)
      else
        stats
      end
    
    # Add states
    states = data["states"] || %{}
    
    Enum.reduce(states, stats, fn {state_num_str, state_data}, acc_stats ->
      state_num = String.to_integer(state_num_str)
      
      type = state_data["type"] || 999
      next_state = state_data["next_state"] || -1
      timeout = state_data["timeout"] || -1
      can_touch = state_data["can_touch"] || 0
      
      react_item = 
        if state_data["react_item"] do
          item_id = state_data["react_item"]["item_id"]
          quantity = state_data["react_item"]["quantity"] || 1
          if item_id, do: {item_id, quantity}, else: nil
        else
          nil
        end
      
      add_state(acc_stats, state_num, type, react_item, next_state, timeout, can_touch)
    end)
  end
end