module Go.Game exposing (verify)
import Go.Types exposing (..)
import Go.Util exposing (lookup)
import List exposing (foldl)
import Maybe exposing (andThen)

-- Make sure it's our turn to play.
verifyTurn : Model -> Cell -> Maybe Cell
verifyTurn model c = if 
    (Just model.sessionColor) == model.currentColor then 
        Just c 
    else
        Nothing

-- Make sure there's not already a piece where we're going.
verifyClear : Model -> Cell -> Maybe Cell
verifyClear model (indx, c) = case lookup indx model.board of
    Just _ -> Nothing
    Nothing -> Just (indx, c)

-- Make sure cell is in range of the board.
verifyBounds : Model -> Cell -> Maybe Cell
verifyBounds model ((x, y), c) = if x >= 0 && x < model.sessionSize && y >= 0 && y < model.sessionSize
    then Just ((x, y), c)
    else Nothing

-- Verify a cell placemenet using a list of verification functions.
verifyAll : Cell -> List (Model -> Cell -> Maybe Cell) -> Model -> Maybe Cell
verifyAll cell funcs model = List.foldl (\a b -> andThen (a model) b) (Just cell) funcs

-- Make sure that a move to the given cell can be made.
verify : Cell -> Model -> Maybe Cell
verify cell model = verifyAll cell [verifyBounds, verifyTurn, verifyClear] model