namespace DeathSocket

    open System.IO
    open ColourServices

    /// Provides functions which help draw gridded overlays onto images.
    /// Death Socket, uses System.Drawing's brushes and colours.
    /// If you are using System.Media brushes and colour, you will need to
    /// convert them. Death Socket, also, uses SkiaSharp for cross platform
    /// functionality. If you are using Death Socket on Windows Desktop, use
    /// functions which do not include "Skia" in their name. If you are using
    /// Death Socket in a Xamarin/UWP project you should use the SkiaSharp
    /// functions.
    module GridPainter =

        open Validation
        open ImageServices

        /// <summary>
        /// Uses the information included in spec to create a gridded image.
        /// It then asynchronously saves it. Uses .jpg or .png formats only.
        /// </summary>
        /// <param name="spec">
        /// The specification used to generate the new gridded image. The
        /// ImageSpec is a discriminated union, consisting of a Brush, RGBA,
        /// Skia or SkiaRGB spec.
        /// </param>
        /// <exeption cref="System.IO.FileNotFoundException">
        /// If the file the grid is being applied to cannot be found,
        /// a FileNotFoundException will be thrown.
        /// </exception>
        /// <remarks>
        /// Make sure the image, which is having the overlay added to it,
        /// is not in use or needed by another program/process.
        /// This is because it is locked whilst in this function.
        /// </remarks>
        let applyGridToImageAsync (spec: ImageSpec) =
            async {
                try
                    match spec with
                    | Brush b ->
                        validateIO b.originalPath b.savePath |> ignore
                        drawBrushSpecGrid b
                    | RGBA r ->
                        validateIO r.originalPath r.savePath |> ignore
                        drawRGBAGrid r
                    | Skia s ->
                        validateIO s.originalPath s.savePath |> ignore
                        drawSkiaGrid s
                    | SkiaRGB sR ->
                        validateIO sR.originalPath sR.savePath |> ignore
                        drawSkiaRGBGrid sR
                with
                | :? FileNotFoundException as ex ->
                    printfn "File could not be found at %s" ex.Message
            }

        // NOT TESTED

        /// <summary>
        /// Takes an image and determines the current scale it is viewed at
        /// (E.G. scaled preview in image viewer). The (pen) line thickness is
        /// then updated to match this preview scale and can be used when
        /// drawing a grid line on the scaled preview of the image.
        /// </summary>
        /// <param name="previewWidth">
        /// The width of the image when previewed (I.E. in a GUI).
        /// </param>
        /// <param name="actualWidth">
        /// The width of the actual image.
        /// </param>
        /// <param name="lineThickness">
        /// The thickness of the pen used to draw the grid line.
        /// </param>
        /// <remarks>
        /// You should find you only need this function when dealing with
        /// previewing an image in a GUI. Another thing to note is the
        /// SkiaSharp based functions already scale the grid lines for you. So,
        /// you should not need to use this function when using them.
        /// </remarks>
        let scaleLineThickness (previewWidth: double) (actualWidth: double) (lineThickness: double) =
            lineThickness / (previewWidth / actualWidth)

        // System.Drawing Functions
        // ========================================================================

        /// <summary>
        /// Determines the (Pen) points needed to draw the appropriate number
        /// of horizontal lines (I.E. rows). Each item in the array includes a
        /// start and end co-ordinate (point) for each line.
        /// Use this function when targeting .Net/Mono).
        /// </summary>
        /// <param name="width">The width of the image.</param>
        /// <param name="height">The height of the image.</param>
        /// <param name="rows">The number of rows the grid should have.</param>
        /// <remarks>You will probably only need these when dealing with GUI's.</remarks>
        let determineHorizontalLines (width: int) (height: int) (rows: int) =
            createHorizontalLines width height rows

        /// <summary>
        /// Determines the (Pen) points needed to draw the appropriate number
        /// of vertical lines (I.E. columns). Each item in the array includes a
        /// start and end co-ordinate (point) for each line.
        /// Use this function when targeting Windows Desktop (or Mono).
        /// </summary>
        /// <param name="width">The width of the image.</param>
        /// <param name="height">The height of the image.</param>
        /// <param name="columns">The number of columns the grid should have.</param>
        /// <remarks>You will probably only need these when dealing with GUI's.</remarks>
        let determineVerticalLines (width: int) (height: int) (columns: int) =
            createVerticalLines width height columns

        /// <summary>
        /// Creates a Sytsem.Drawing SolidBrush from the individual RGBA values.
        /// Use this function when targeting .Net/Mono).
        /// </summary>
        /// <param name="r">The red value.</param>
        /// <param name="g">The green value.</param>
        /// <param name="b">The blue value.</param>
        /// <param name="a">The alpha value.</param>
        /// <remarks>
        /// Death Socket uses System.Drawing and not System.Media for colours
        /// and brushes.
        /// </remarks>
        let makeSolidBrushFromRGBA (r: int) (g: int) (b:int) (a: int) =
            makeBrushFromRGBA r g b a

        /// <summary>
        /// Creates a System.Drawing SolidBrush from a RGBASpec.
        /// Use this function when targeting .Net/Mono).
        /// </summary>
        /// <param name="spec">
        ///The specification which the brush is made from.
        ///</param>
        /// <remarks>
        /// Death Socket uses System.Drawing and not System.Media for colours
        /// and brushes.
        /// </remarks>
        let makeSolidBrushFromRGBASpec (spec: RGBASpec) =
            makeBrushFromRGBASpec spec

        // SkiaSharp Functions
        // ========================================================================

        /// <summary>
        /// Determines the (SKPoints) points needed to draw the appropriate
        /// number of horizontal lines (I.E. rows). Each item in the array
        /// included a start and end co-ordinate (SKPoint) for each line.
        /// Use this function when targeting Xamarin/UWP/.Net Core (SkiaSharp).
        /// </summary>
        /// <param name="width">The width of the image.</param>
        /// <param name="height">The height of the image.</param>
        /// <param name="rows">The number of rows the grid should have.</param>
        /// <remarks>This function is part of the SkiaSharp functions provided
        /// by Death Socket.</remarks>
        let determineSKHorizontalLines (width: int) (height: int) (rows: int) =
            createSKHorizontalLines width height rows

        /// <summary>
        /// Determines the (SKPoints) points needed to draw the appropriate
        /// number of vertical lines (I.E. columns). Each item in the array
        /// included a start and end co-ordinate (SKPoint) for each line.
        /// Use this function when targeting Xamarin/UWP/.Net Core (SkiaSharp).
        /// </summary>
        /// <param name="width">The width of the image.</param>
        /// <param name="height">The height of the image.</param>
        /// <param name="columns">The number of columns the grid should have.
        /// </param>
        /// <remarks>This function is part of the SkiaSharp functions provided
        /// by Death Socket.</remarks>
        let determineSKVerticalLines (width: int) (height: int) (columns: int) =
            createSKVerticalLines width height columns