#region --- License ---
/* Copyright (c) 2006, 2007 Stefanos Apostolopoulos
 * See license.txt for license info
 */
#endregion

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing.Text;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Diagnostics;

using OpenTK.Math;
using OpenTK.Graphics;
using OpenTK.Platform;

namespace OpenTK.Graphics
{
    using Graphics = System.Drawing.Graphics;
    using PixelFormat = OpenTK.Graphics.PixelFormat;
using System.Text.RegularExpressions;

    public class TextureFont : IFont
    {
        Font font;
        Dictionary<char, RectangleF> loaded_glyphs = new Dictionary<char, RectangleF>(64);

        Bitmap bmp;
        Graphics gfx;
        // TODO: We need to be able to use multiple font sheets.
        static int texture;
        static TexturePacker<Glyph> pack;
        static int texture_width, texture_height;
        static readonly StringFormat default_string_format = StringFormat.GenericTypographic; // Check the constructor, too, for additional flags.
        static readonly StringFormat load_glyph_string_format = StringFormat.GenericDefault;
        static SizeF maximum_graphics_size;

        int[] data = new int[256];  // Used to upload the glyph buffer to the OpenGL texture.

        object upload_lock = new object();

        static readonly char[] newline_characters = new char[] { '\n', '\r' };

        #region --- Constructor ---

        /// <summary>
        /// Constructs a new TextureFont, using the specified System.Drawing.Font.
        /// </summary>
        /// <param name="font">The System.Drawing.Font to use.</param>
        public TextureFont(Font font)
        {
            if (font == null)
                throw new ArgumentNullException("font", "Argument to TextureFont constructor cannot be null.");

            this.font = font;

            bmp = new Bitmap(font.Height * 2, font.Height * 2);
            gfx = Graphics.FromImage(bmp);
            maximum_graphics_size = gfx.ClipBounds.Size;

            // Adjust font rendering mode. Small sizes look blurry without gridfitting, so turn
            // that on. Increasing contrast also seems to help.
            if (font.Size <= 18.0f)
            {
                gfx.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;
                //gfx.TextContrast = 11;
            }
            else
            {
                gfx.TextRenderingHint = TextRenderingHint.AntiAlias;
                //gfx.TextContrast = 0;
            }

            default_string_format.FormatFlags |= StringFormatFlags.MeasureTrailingSpaces;
        }

        /// <summary>
        /// Constructs a new TextureFont, using the specified parameters.
        /// </summary>
        /// <param name="font">The System.Drawing.FontFamily to use for the typeface.</param>
        /// <param name="emSize">The em size to use for the typeface.</param>
        public TextureFont(FontFamily family, float emSize)
            : this(new Font(family, emSize))
        { }

        /// <summary>
        /// Constructs a new TextureFont, using the specified parameters.
        /// </summary>
        /// <param name="font">The System.Drawing.FontFamily to use for the typeface.</param>
        /// <param name="emSize">The em size to use for the typeface.</param>
        /// <param name="family">The style to use for the typeface.</param>
        public TextureFont(FontFamily family, float emSize, FontStyle style)
            : this(new Font(family, emSize, style))
        { }

        #endregion

        #region --- Public Methods ---

        #region public void LoadGlyphs(string glyphs)

        /// <summary>
        /// Prepares the specified glyphs for rendering.
        /// </summary>
        /// <param name="glyphs">The glyphs to prepare for rendering.</param>
        public void LoadGlyphs(string glyphs)
        {
            RectangleF rect = new RectangleF();
            foreach (char c in glyphs)
            {
                if (Char.IsWhiteSpace(c))
                    continue;

                try
                {
                    if (!loaded_glyphs.ContainsKey(c))
                        LoadGlyph(c, out rect);
                }
                catch (Exception e)
                {
                    Debug.Print(e.ToString());
                    throw;
                }
            }
        }

        #endregion

        #region public void LoadGlyph(char glyph)

        /// <summary>
        /// Prepares the specified glyph for rendering.
        /// </summary>
        /// <param name="glyphs">The glyph to prepare for rendering.</param>
        public void LoadGlyph(char glyph)
        {
            RectangleF rect = new RectangleF();
            if (!loaded_glyphs.ContainsKey(glyph))
                LoadGlyph(glyph, out rect);
        }

        #endregion

        #region public bool GlyphData(char glyph, out float width, out float height, out RectangleF textureRectangle, out int texture)

        /// <summary>
        /// Returns the characteristics of a loaded glyph.
        /// </summary>
        /// <param name="glyph">The character corresponding to this glyph.</param>
        /// <param name="width">The width of this glyph.</param>
        /// <param name="height">The height of this glyph (line spacing).</param>
        /// <param name="textureRectangle">The bounding box of the texture buffer of this glyph.</param>
        /// <param name="texture">The handle to the texture that contains this glyph.</param>
        /// <returns>True if the glyph has been loaded, false otherwise.</returns>
        /// <seealso cref="LoadGlyphs"/>
        public bool GlyphData(char glyph, out float width, out float height, out RectangleF textureRectangle, out int texture)
        {
            if (loaded_glyphs.TryGetValue(glyph, out textureRectangle))
            {
                width = textureRectangle.Width * texture_width;
                height = textureRectangle.Height * texture_height;
                texture = TextureFont.texture;
                return true;
            }
            width = height = texture = 0;
            return false;
        }

        #endregion

        #region public float Height

        /// <summary>
        /// Gets a float indicating the default line spacing of this font.
        /// </summary>
        public float Height
        {
            get { return font.Height; }
        }

        #endregion

        #region public float Width

        /// <summary>
        /// Gets a float indicating the default size of this font, in points.
        /// </summary>
        public float Width
        {
            get { return font.SizeInPoints; }
        }

        #endregion

        #region public void MeasureString(string str, out float width, out float height, bool accountForOverhangs)

        /// <summary>
        /// Measures the width of the specified string.
        /// </summary>
        /// <param name="str">The string to measure.</param>
        /// <param name="width">The measured width.</param>
        /// <param name="height">The measured height.</param>
        /// <param name="accountForOverhangs">If true, adds space to account for glyph overhangs. Set to true if you wish to measure a complete string. Set to false if you wish to perform layout on adjacent strings.</param>
        [Obsolete("Returns invalid results - use MeasureText() instead")]
        public void MeasureString(string str, out float width, out float height, bool accountForOverhangs)
        {
            System.Drawing.StringFormat format = accountForOverhangs ? System.Drawing.StringFormat.GenericDefault : System.Drawing.StringFormat.GenericTypographic;

            System.Drawing.SizeF size = gfx.MeasureString(str, font, 16384, format);
            height = size.Height;
            width = size.Width;
        }

        #endregion

        #region public void MeasureString(string str, out float width, out float height)

        /// <summary>
        /// Measures the width of the specified string.
        /// </summary>
        /// <param name="str">The string to measure.</param>
        /// <param name="width">The measured width.</param>
        /// <param name="height">The measured height.</param>
        /// <seealso cref="public void MeasureString(string str, out float width, out float height, bool accountForOverhangs)"/>
        [Obsolete("Returns invalid results - use MeasureText() instead")]
        public void MeasureString(string str, out float width, out float height)
        {
            MeasureString(str, out width, out height, true);
        }

        #endregion

        #region public RectangleF MeasureText(string text)

        /// <summary>
        /// Calculates size information for the specified text.
        /// </summary>
        /// <param name="text">The string to measure.</param>
        /// <returns>A RectangleF containing the bounding box for the specified text.</returns>
        public RectangleF MeasureText(string text)
        {
            return MeasureText(text, SizeF.Empty, default_string_format, null);
        }

        #endregion

        #region public RectangleF MeasureText(string text, SizeF bounds)

        /// <summary>
        /// Calculates size information for the specified text.
        /// </summary>
        /// <param name="text">The string to measure.</param>
        /// <param name="bounds">A SizeF structure containing the maximum desired width and height of the text. Default is SizeF.Empty.</param>
        /// <returns>A RectangleF containing the bounding box for the specified text.</returns>
        public RectangleF MeasureText(string text, SizeF bounds)
        {
            return MeasureText(text, bounds, default_string_format, null);
        }

        #endregion

        #region public RectangleF MeasureText(string text, SizeF bounds, StringFormat format)

        /// <summary>
        /// Calculates size information for the specified text.
        /// </summary>
        /// <param name="text">The string to measure.</param>
        /// <param name="bounds">A SizeF structure containing the maximum desired width and height of the text. Pass SizeF.Empty to disable wrapping calculations. A width or height of 0 disables the relevant calculation.</param>
        /// <param name="format">A StringFormat object which specifies the measurement format of the string. Pass null to use the default StringFormat (StringFormat.GenericTypographic).</param>
        /// <returns>A RectangleF containing the bounding box for the specified text.</returns>
        public RectangleF MeasureText(string text, SizeF bounds, StringFormat format)
        {
            return MeasureText(text, bounds, format, null);
        }

        #endregion

        #region public RectangleF MeasureText(string text, SizeF bounds, StringFormat format, IList<RectangleF> ranges)

        IntPtr[] regions = new IntPtr[GdiPlus.MaxMeasurableCharacterRanges];
        CharacterRange[] characterRanges = new CharacterRange[GdiPlus.MaxMeasurableCharacterRanges];

        /// <summary>
        /// Calculates size information for the specified text.
        /// </summary>
        /// <param name="text">The string to measure.</param>
        /// <param name="bounds">A SizeF structure containing the maximum desired width and height of the text. Pass SizeF.Empty to disable wrapping calculations. A width or height of 0 disables the relevant calculation.</param>
        /// <param name="format">A StringFormat object which specifies the measurement format of the string. Pass null to use the default StringFormat (StringFormat.GenericDefault).</param>
        /// <param name="ranges">Fills the specified IList of RectangleF structures with position information for individual characters. If this argument is null, these calculations are skipped.</param>
        /// <returns>A RectangleF containing the bounding box for the specified text.</returns>
        public RectangleF MeasureText(string text, SizeF bounds, StringFormat format, List<RectangleF> ranges)
        {
            if (String.IsNullOrEmpty(text))
                return RectangleF.Empty;

            if (bounds == SizeF.Empty)
                bounds = maximum_graphics_size;

            if (format == null)
                format = default_string_format;

            // TODO: What should we do in this case?
            if (ranges == null)
                ranges = new List<RectangleF>();

            ranges.Clear();

            PointF origin = PointF.Empty;
            SizeF size = SizeF.Empty;

            IntPtr native_graphics = GdiPlus.GetNativeGraphics(gfx);
            IntPtr native_font = GdiPlus.GetNativeFont(font);
            IntPtr native_string_format = GdiPlus.GetNativeStringFormat(format);

            RectangleF layoutRect = new RectangleF(PointF.Empty, bounds);

            int height = 0;

            // It seems that the mere presence of \n and \r characters
            // is enough for Mono to botch the layout (even if these
            // characters are not processed.) We'll need to find a
            // different way to perform layout on Mono, probably
            // through Pango.
            // Todo: This workaround  allocates memory.
            //if (Configuration.RunningOnMono)
            {
                string[] lines = text.Replace("\r", String.Empty).Split(newline_characters);
                foreach (string s in lines)
                {
                    ranges.AddRange(GetCharExtents(
                        s, height, 0, s.Length, layoutRect,
                        native_graphics, native_font, native_string_format));
                    height += font.Height;
                }
            }

            return new RectangleF(ranges[0].X, ranges[0].Y, ranges[ranges.Count - 1].Right, ranges[ranges.Count - 1].Bottom);
        }

        #endregion

        #endregion

        #region --- Private Methods ---

        #region private void PrepareTexturePacker()

        /// <summary>
        /// Calculates the optimal size for the font texture and TexturePacker, and creates both.
        /// </summary>
        private void PrepareTexturePacker()
        {
            // Calculate the size of the texture packer. We want a power-of-two size
            // that is less than 1024 (supported in Geforce256-era cards), but large
            // enough to hold at least 256 (16*16) font glyphs.
            // TODO: Find the actual card limits, maybe?
            int size = (int)(font.Size * 16);
            size = (int)System.Math.Pow(2.0, System.Math.Ceiling(System.Math.Log((double)size, 2.0)));
            if (size > 1024)
                size = 1024;

            texture_width = size;
            texture_height = size;
            pack = new TexturePacker<Glyph>(texture_width, texture_height);

            GL.GenTextures(1, out texture);
            GL.BindTexture(TextureTarget.Texture2D, texture);
            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)All.Linear);
            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)All.Linear);
            if (GL.SupportsExtension("Version12"))
            {
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)All.ClampToEdge);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)All.ClampToEdge);
            }
            else
            {
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)All.Clamp);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)All.Clamp);
            }

            GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Alpha, texture_width, texture_height, 0,
                OpenTK.Graphics.PixelFormat.Rgba, PixelType.UnsignedByte, IntPtr.Zero);
        }

        #endregion

        #region private void LoadGlyph(char c, out RectangleF rectangle)

        // Adds the specified caharacter to the texture packer.
        private void LoadGlyph(char c, out RectangleF rectangle)
        {
            if (pack == null)
                PrepareTexturePacker();

            RectangleF glyph_rect = MeasureText(c.ToString(), SizeF.Empty, load_glyph_string_format);
            SizeF glyph_size = new SizeF(glyph_rect.Right, glyph_rect.Bottom);  // We need to do this, since the origin might not be (0, 0)
            Glyph g = new Glyph(c, font, glyph_size);
            Rectangle rect;

            try
            {
                pack.Add(g, out rect);
            }
            catch (InvalidOperationException expt)
            {
                // TODO: The TexturePacker is full, create a new font sheet.
                Trace.WriteLine(expt);
                throw;
            }

            GL.BindTexture(TextureTarget.Texture2D, texture);

            gfx.Clear(System.Drawing.Color.Transparent);
            gfx.DrawString(g.Character.ToString(), g.Font, System.Drawing.Brushes.White, 0.0f, 0.0f, default_string_format);

            BitmapData bitmap_data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly,
                System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            
            GL.PushClientAttrib(ClientAttribMask.ClientPixelStoreBit);
            try
            {
                GL.PixelStore(PixelStoreParameter.UnpackAlignment, 1.0f);
                GL.PixelStore(PixelStoreParameter.UnpackRowLength, bmp.Width);
                GL.TexSubImage2D(TextureTarget.Texture2D, 0, (int)rect.Left, (int)rect.Top,
                    rect.Width, rect.Height,
                    OpenTK.Graphics.PixelFormat.Rgba,
                    PixelType.UnsignedByte, bitmap_data.Scan0);
            }
            finally
            {
                GL.PopClientAttrib();
            }

            bmp.UnlockBits(bitmap_data);

            rectangle = RectangleF.FromLTRB(
                rect.Left / (float)texture_width,
                rect.Top / (float)texture_height,
                rect.Right / (float)texture_width,
                rect.Bottom / (float)texture_height);

            loaded_glyphs.Add(g.Character, rectangle);
        }

        #endregion

        #region GetCharExtents

        // Gets the bounds of each character in a line of text.
        // The line is processed in blocks of 32 characters (GdiPlus.MaxMeasurableCharacterRanges).
        IEnumerable<RectangleF> GetCharExtents(string text, int height, int line_start, int line_length,
            RectangleF layoutRect, IntPtr native_graphics, IntPtr native_font, IntPtr native_string_format)
        {
            RectangleF rect = new RectangleF();
            int line_end = line_start + line_length;
            while (line_start < line_end)
            {
                //if (text[line_start] == '\n' || text[line_start] == '\r')
                //{
                //    line_start++;
                //    continue;
                //}

                int num_characters = (line_end - line_start) > GdiPlus.MaxMeasurableCharacterRanges ?
                    GdiPlus.MaxMeasurableCharacterRanges :
                    line_end - line_start;
                int status = 0;

                for (int i = 0; i < num_characters; i++)
                {
                    characterRanges[i] = new CharacterRange(line_start + i, 1);

                    IntPtr region;
                    status = GdiPlus.CreateRegion(out region);
                    regions[i] = region;
                    Debug.Assert(status == 0, String.Format("GDI+ error: {0}", status));
                }

                status = GdiPlus.SetStringFormatMeasurableCharacterRanges(native_string_format, num_characters, characterRanges);
                Debug.Assert(status == 0, String.Format("GDI+ error: {0}", status));

                status = GdiPlus.MeasureCharacterRanges(native_graphics, text, text.Length,
                                                native_font, ref layoutRect, native_string_format, num_characters, regions);
                Debug.Assert(status == 0, String.Format("GDI+ error: {0}", status));

                for (int i = 0; i < num_characters; i++)
                {
                    GdiPlus.GetRegionBounds(regions[i], native_graphics, ref rect);
                    Debug.Assert(status == 0, String.Format("GDI+ error: {0}", status));
                    GdiPlus.DeleteRegion(regions[i]);
                    Debug.Assert(status == 0, String.Format("GDI+ error: {0}", status));

                    rect.Y += height;
                    yield return rect;
                }

                line_start += num_characters;
            }
        }

        #endregion

        #endregion

        #region --- Internal Methods ---

        #region internal int Texture

        /// <summary>
        /// Gets the handle to the texture were this font resides.
        /// </summary>
        internal int Texture
        {
            get { return TextureFont.texture; }
        }

        #endregion

        #endregion

        #region --- IDisposable Members ---

        bool disposed;

        /// <summary>
        /// Releases all resources used by this OpenTK.Graphics.TextureFont.
        /// </summary>
        public void Dispose()
        {
            GC.SuppressFinalize(this);
            Dispose(true);
        }

        private void Dispose(bool manual)
        {
            if (!disposed)
            {
                pack = null;
                if (manual)
                {
                    GL.DeleteTextures(1, ref texture);
                    font.Dispose();
                    gfx.Dispose();
                }

                disposed = true;
            }
        }

        ~TextureFont()
        {
            Dispose(false);
        }

        #endregion
    }
}