module LngLat exposing (LngLat, encodeAsPair, encodeAsObject, decodeFromPair, decodeFromObject, map) {-| @docs LngLat, encodeAsPair, encodeAsObject, decodeFromPair, decodeFromObject, map -} import Json.Encode as Encode exposing (Value) import Json.Decode as Decode exposing (Decoder) {-| A LngLat represents a geographic position. -} type alias LngLat = { lng : Float , lat : Float } {-| Most implementations seem to encode these as a 2 member array. -} encodeAsPair : LngLat -> Value encodeAsPair { lng, lat } = Encode.list [ Encode.float lng, Encode.float lat ] {-| Most implementations seem to encode these as a 2 member array. -} decodeFromPair : Decoder LngLat decodeFromPair = Decode.list Decode.float |> Decode.andThen (\l -> case l of [ lng, lat ] -> Decode.succeed (LngLat lng lat) _ -> Decode.fail "Doesn't apear to be a valid lng lat pair" ) {-| We can also encode as an `{lng: 32, lat: 435}` object. -} encodeAsObject : LngLat -> Value encodeAsObject { lng, lat } = Encode.object [ ( "lng", Encode.float lng ), ( "lat", Encode.float lat ) ] {-| We can also encode from an `{lng: 32, lat: 435}` object. -} decodeFromObject : Decoder LngLat decodeFromObject = Decode.map2 LngLat (Decode.field "lng" Decode.float) (Decode.field "lat" Decode.float) {-| -} map : (Float -> Float) -> LngLat -> LngLat map f { lng, lat } = { lng = f lng, lat = f lat }