module internal InternalServices

    open System.IO
    open System.Drawing
    open SmoulderingBeachBall.Domain

    module Validation =

        let validateDimension dimension =
            match dimension with
            | dimension when dimension <= 0 -> 
                invalidArg "dimension" "[ERROR] The images height and width must be greater than 0."
            | _ -> ()

        let validateDirectory filePath =
            let path = Path.GetDirectoryName filePath
            match (Directory.Exists path) with
            | false ->
                invalidArg "filePath" "[ERROR] Unable to save to the specified location because it could not be found."
            | true -> ()

    module Drawing =
        open System.Text

        let penOffset penWidth = int (penWidth / (float32 2))

        let setPenWidth imgWidth imgHeight =
            let width = float32 imgWidth
            let height = float32 imgHeight
            if (width >= height) then
                height * (float32 0.05)
            else width * (float32 0.05)

        let createBorderPath penWidth spec =
            let offset = penOffset penWidth
            [|Point (0, offset); // Essentially (0, 0)
              Point ((spec.width - offset), offset);
              Point ((spec.width - offset), (spec.height - offset));
              Point (offset, (spec.height - offset));
              Point (offset, 0)|]

        let drawBorder (graphics: Graphics) (pen: Pen) spec =
            printfn "[INFO.] Adding border to image..."
            let penPath = createBorderPath pen.Width spec
            graphics.DrawLines (pen, penPath)

        let drawFullOverlay (graphics: Graphics) (pen: Pen) spec =
            drawBorder graphics pen spec
            printfn "[INFO.] Adding full overlay to image..."
            let offset = penOffset pen.Width
            // Draws line from top-left to bottom-right of square.
            graphics.DrawLine (pen, offset, offset, (spec.width - offset), (spec.height - offset))
            // Draws line from top-right to bottom-left of square.
            graphics.DrawLine (pen, (spec.width - offset), offset, offset, (spec.height - offset))

        let addOverlayToImage graphics spec =
            let overlay = spec.overlay.Value
            let pen = 
                new Pen (overlay.colour, width = (setPenWidth spec.width spec.height))
            match overlay.overlayType with
            | Border -> drawBorder graphics pen spec
            | Full -> drawFullOverlay graphics pen spec

        let buildFileName spec =
            let sb = new StringBuilder ()
            sb.Append (spec.width.ToString ()) |> ignore
            sb.Append "x" |> ignore
            sb.Append (spec.height.ToString ()) |> ignore
            sb.Append ".png" |> ignore
            (sb.ToString ())

        let  drawImage spec =
            let bitmap = new Bitmap (spec.width, spec.height)
            let graphics = Graphics.FromImage (bitmap)
            let rectangle = Rectangle (0, 0, spec.width, spec.height)
            graphics.FillRectangle (spec.colour, rectangle)
            match spec.overlay.IsSome with
            | true -> addOverlayToImage graphics spec
            | false -> printfn "[INFO.] No overlay specified. Creating image without one."
            bitmap.Save (Path.Combine (spec.filePath, (buildFileName spec)))
            graphics.Dispose()
            bitmap.Dispose()