{-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-}
-- | Chu Shogi AI for normal games. Mating problems use 'Mating' instead.
-- Copyright 2009 Colin Adams
--
-- This file is part of chu-shogi.
--
--  Chu-shogi is free software: you can redistribute it and/or modify
--  it under the terms of the GNU General Public License as published by
--  the Free Software Foundation, either version 3 of the License, or
--  (at your option) any later version.

--  Chu-shogi is distributed in the hope that it will be useful,
--  but WITHOUT ANY WARRANTY; without even the implied warranty of
--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--  GNU General Public License for more details.

--  You should have received a copy of the GNU General Public License
--  along with chu-shogi.  If not, see <http://www.gnu.org/licenses/>.

module AI (
           -- * Access
           recommended_move
          ) where

import Data.Tree.Game_tree.Negascout
import Data.Tree.Game_tree.Game_tree
import Game_state
import Generator
import Evaluator
import Move
import Data.Maybe (fromJust)

-- | Game trees are normal positions.
--   Children are the full output from the move generator.
--   Terminal nodes represent a won game.
instance Game_tree (Non_interactive_state, Maybe Move)
    where
      is_terminal (ni_state, _) = 
          case white_kings ni_state of
            0 -> True
            _ -> case black_kings ni_state of
                  0 -> True
                  _ -> is_bare_king ni_state
                         
      node_value (ni_state, _) = value_for_black ni_state
      children = generate_moves

recommended_move :: Non_interactive_state -> Move
recommended_move initial_state =
    let (principal_variation, _score) = negascout (initial_state, Nothing) 4
    in fromJust . snd . head . tail $ principal_variation