using System;
using System.IO;
using System.Text;

namespace Robust.Client.Graphics
{
    public interface IFontManager
    {
        public void ClearFontCache();
    }
    internal interface IFontManagerInternal : IFontManager
    {
        IFontFaceHandle Load(Stream stream, int index = 0);
        IFontFaceHandle Load(IFontMemoryHandle memory, int index = 0);

        /// <summary>
        /// Load a specified font in a font collection.
        /// </summary>
        /// <param name="memory">Memory for the entire font collection.</param>
        /// <param name="postscriptName">The postscript name of the font to load.</param>
        IFontFaceHandle LoadWithPostscriptName(IFontMemoryHandle memory, string postscriptName);
        IFontInstanceHandle MakeInstance(IFontFaceHandle handle, int size);
        void SetFontDpi(uint fontDpi);
    }

    internal interface IFontFaceHandle
    {

    }

    internal interface IFontInstanceHandle
    {
        Texture? GetCharTexture(Rune codePoint, float scale);
        Texture? GetCharTexture(char chr, float scale) => GetCharTexture((Rune) chr, scale);
        CharMetrics? GetCharMetrics(Rune codePoint, float scale);
        CharMetrics? GetCharMetrics(char chr, float scale) => GetCharMetrics((Rune) chr, scale);

        int GetAscent(float scale);
        int GetDescent(float scale);
        int GetHeight(float scale);
        int GetLineHeight(float scale);
    }

    internal unsafe interface IFontMemoryHandle : IDisposable
    {
        byte* GetData();
        nint GetDataSize();
    }

    /// <summary>
    ///     Metrics for a single glyph in a font.
    ///     Refer to https://www.freetype.org/freetype2/docs/glyphs/glyphs-3.html for more information.
    /// </summary>
    public readonly struct CharMetrics
    {
        /// <summary>
        ///     The horizontal distance between the origin and the left of the drawn glyph.
        /// </summary>
        public readonly int BearingX;

        /// <summary>
        ///     The vertical distance between the origin and the top of the drawn glyph.
        /// </summary>
        public readonly int BearingY;

        /// <summary>
        ///     How much to advance the origin after drawing the glyph.
        /// </summary>
        public readonly int Advance;

        /// <summary>
        ///     The width of the drawn glyph.
        /// </summary>
        public readonly int Width;

        /// <summary>
        ///     The height of the drawn glyph.
        /// </summary>
        public readonly int Height;

        public CharMetrics(int bearingX, int bearingY, int advance, int width, int height)
        {
            BearingX = bearingX;
            BearingY = bearingY;
            Advance = advance;
            Width = width;
            Height = height;
        }
    }
}