LightsOut.elm

module Main exposing (main)

import Html exposing (Html)


-- MODEL

type alias Model =
    List Bool

x = True
o = False

state : Model
state =
    [ [ o, x, o, x, o ]
    , [ o, x, x, x, x ]
    , [ x, x, o, x, x ]
    , [ x, x, x, x, x ]
    , [ x, x, x, x, x ]
    ]
        |> List.concatMap identity


moves =
    [ ( 3, 2 )
    , ( 2, 4 )
    , ( 3, 3 )
    , ( 0, 3 )
    , ( 1, 2 )
    , ( 3, 1 )
    , ( 1, 4 )
    , ( 4, 0 )
    , ( 1, 4 )
    , ( 0, 1 )
    , ( 0, 1 )
    , ( 0, 2 )
    , ( 0, 2 )
    , ( 3, 1 )
    , ( 0, 4 )
    , ( 2, 2 )
    , ( 1, 3 )
    , ( 3, 1 )
    , ( 2, 2 )
    , ( 1, 1 )
    , ( 0, 0 )
    , ( 4, 3 )
    , ( 4, 4 )
    , ( 2, 3 )
    , ( 4, 3 )
    ]


lightsOnCount : Model -> Int
lightsOnCount =
    List.filter identity >> List.length


-- UPDATE


type alias Msg =
    ( Int, Int )


update : Msg -> Model -> Model
update msg model =
    let
        validNeighbors =
            neighbors msg |> List.map index
    in
    List.indexedMap
        (\index currentState ->
            if List.member index validNeighbors then
                not currentState
            else
                currentState
        )
        model


applyMoves : List Msg -> Model -> Model
applyMoves msgs model =
    case msgs of
        msg :: msgs ->
            applyMoves msgs (update msg model)

        [] ->
            model


index : ( Int, Int ) -> Int
index ( x, y ) =
    x * 5 + y


neighbors : ( Int, Int ) -> List ( Int, Int )
neighbors ( x, y ) =
    let
        allNeighbors =
            [ ( x, y ), ( x - 1, y ), ( x + 1, y ), ( x, y - 1 ), ( x, y + 1 ) ]

        validNeighbors =
            allNeighbors |> List.filter (\( x, y ) -> x >= 0 && x < 5 && y >= 0 && y < 5)
    in
    validNeighbors


main : Html msg
main =
    Html.text ("Lights on after update: " ++ toString (lightsOnCount (applyMoves moves state)))