-- | Normal move evaluator
-- 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 Evaluator
    (
     -- * Access
     value_for_black
    ) where

import Game_state
import Board

{-# contract value_for_black :: Ok -> {r | r <= (maxBound :: Int) - 3 && r >= (minBound :: Int) + 4} #-}
-- | Standard evaluation function
value_for_black :: Non_interactive_state -> Int
value_for_black ni_state@(_, board', (w_kings, b_kings, _)) =
    let v = case w_kings == 0 of
              True -> (maxBound :: Int) - 3
              False -> case b_kings == 0 of
                         True -> (minBound :: Int) + 4
                         False ->case is_bare_king ni_state of
                                   True -> case is_white_bare_gold ni_state of
                                             True -> (minBound :: Int) + 4
                                             False -> (maxBound :: Int) - 3
                                   False -> position_value board'
    in case is_black_to_play ni_state of
         True -> v
         False -> -v