module Hexagons.Grid exposing (Grid, Row, Tile, get, set, delete, list, getPoint)

{-| A naive grid storage for hexagons: `Dict Int (Dict Int a)`

# Types
@docs Grid, Row, Tile

# Finders
@docs get, list, getPoint

# Modifiers
@docs set, delete
-}

import Dict exposing (Dict)
import Hexagons exposing (..)


{-| A grid is a Dict of rows
-}
type alias Grid a =
    Dict Int (Row a)


{-| A row is a Dict of values
-}
type alias Row a =
    Dict Int a


{-| A tile has coords and some content
-}
type alias Tile a =
    { content : a
    , coords : Axial
    }


{-| Find eventual content in grid on those axial coordinates
-}
get : Grid a -> Axial -> Maybe a
get grid ( i, j ) =
    (Dict.get i grid) |> Maybe.andThen (Dict.get j)


{-| Add or update content to grid on those axial coordinates
-}
set : a -> Axial -> Grid a -> Grid a
set tile ( i, j ) grid =
    let
        updateRow maybeRow =
            case maybeRow of
                Just row ->
                    Dict.insert j tile row

                Nothing ->
                    Dict.singleton j tile
    in
        Dict.insert i (updateRow (Dict.get i grid)) grid


{-| Remove content from those axial coordinates within grid
-}
delete : Axial -> Grid a -> Grid a
delete ( i, j ) grid =
    let
        deleteInRow maybeRow =
            case maybeRow of
                Just row ->
                    Dict.remove j row

                Nothing ->
                    Dict.empty
    in
        Dict.insert i (deleteInRow (Dict.get i grid)) grid


{-| Produce a list of all tiles within grid
-}
list : Grid a -> List (Tile a)
list grid =
    let
        rows =
            Dict.toList grid

        mapRow ( i, row ) =
            List.map (mapTile i) (Dict.toList row)

        mapTile i ( j, kind ) =
            Tile kind ( i, j )
    in
        List.concatMap mapRow rows


{-| Given an hexagonal grid definition (radius and grid),
what's in the hexagon holding this point?
-}
getPoint : Float -> Grid a -> Point -> Maybe a
getPoint hexRadius grid p =
    Hexagons.pointToAxial hexRadius p
        |> get grid