module Go.Decoders exposing (..)
import Go.Types exposing (..)
import Json.Decode as Decode
import Json.Decode.Pipeline exposing (decode, required)

pair : a -> b -> (a, b)
pair a1 a2 = (a1, a2)

decodeIndex : Decode.Decoder Index
decodeIndex = decode pair
    |> required "x" Decode.int
    |> required "y" Decode.int

decodeColor : Decode.Decoder Color
decodeColor = 
    let
        tryDecode : String -> Decode.Decoder Color
        tryDecode s = case s of
            "White" -> Decode.succeed White
            "Black" -> Decode.succeed Black
            _ -> Decode.fail "Invalid color"
    in
        Decode.andThen tryDecode Decode.string 

decodeCell : Decode.Decoder Cell
decodeCell = decode pair
    |> required "index" decodeIndex
    |> required "color" decodeColor

decodeUpdate : Decode.Decoder Update
decodeUpdate = decode pair
    |> required "turn" decodeColor
    |> required "board" (Decode.list decodeCell)

decodeUpdatestring : String -> Result String Update
decodeUpdatestring = Decode.decodeString decodeUpdate