SKColorTransform_FSharp.fs

type TransformToSKColorAttribute() =
    inherit ArgumentTransformationAttribute()

    let matchColor name =
        seq {
            match name with
            | knownColor when ColorNames.Contains(knownColor) -> yield ColorLibrary.[knownColor]
            | clear when String.Equals(clear, "transparent", StringComparison.OrdinalIgnoreCase) -> yield SKColor.Empty
            | patternString when WildcardPattern.ContainsWildcardCharacters(patternString) ->
                let pattern = WildcardPattern(patternString, WildcardOptions.IgnoreCase)
                for color in ColorNames do
                    if pattern.IsMatch(color) then yield ColorLibrary.[color]
            | x ->
                let (success, color) = SKColor.TryParse(x)
                if success then yield color
        }

    let transform (input : obj) =
        let values =
            match input with
            | :? Array as arr -> arr
            | x -> Seq.toArray [ x ] :> Array
        seq {
            for item in values do
                match item with
                | :? string as s -> for color in matchColor s do yield color
                | x ->
                    let properties =
                        match x with
                        | :? IDictionary as d -> d :> IEnumerable
                        | p -> PSObject.AsPSObject(p).Properties :> IEnumerable
                    let red = if isNull (ValueFrom properties "Red") then 0uy else ValueFrom properties "Red" |> As<byte>
                    let green = if isNull (ValueFrom properties "Green") then 0uy else ValueFrom properties "Green" |> As<byte>
                    let blue = if isNull (ValueFrom properties "Blue") then 0uy else ValueFrom properties "Blue" |> As<byte>
                    let alpha = if isNull (ValueFrom properties "Alpha") then 255uy else ValueFrom properties "Alpha" |> As<byte>

                    yield SKColor(red, green, blue, alpha)

        }

    override self.Transform(intrinsics, data) =
        let results =
            match data with
            | :? SKColor as c -> seq { yield c }
            | :? string as s -> matchColor s
            | x -> transform x
            |> Seq.toList

        match results with
        | unit when unit.Length = 1 -> unit.[0] :> obj
        | x -> x :> obj