// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace System.Windows.Media
{
    /// <summary>
    /// The FontEmbeddingManager class handles physical and composite font embedding.
    /// </summary>
    public class FontEmbeddingManager
    {
        //------------------------------------------------------
        //
        //  Constructors
        //
        //------------------------------------------------------
 
        #region Constructors
 
        /// <summary>
        /// Creates a new instance of font usage manager.
        /// </summary>
        public FontEmbeddingManager()
        {
            _collectedGlyphTypefaces = new Dictionary<Uri, Dictionary<ushort, bool>>(_uriComparer);
        }
 
        #endregion Constructors
 
        //------------------------------------------------------
        //
        //  Public Methods
        //
        //------------------------------------------------------
 
        #region Public Methods
 
        /// <summary>
        /// Collects information about glyph typeface and index used by a glyph run.
        /// </summary>
        /// <param name="glyphRun">Glyph run to obtain typeface and index information from.</param>
        public void RecordUsage(GlyphRun glyphRun)
        {
            ArgumentNullException.ThrowIfNull(glyphRun);
 
            Uri glyphTypeface = glyphRun.GlyphTypeface.FontUri;
 
            Dictionary<ushort, bool> glyphSet;
            
            if (_collectedGlyphTypefaces.ContainsKey(glyphTypeface))
                glyphSet = _collectedGlyphTypefaces[glyphTypeface];
            else
                glyphSet = _collectedGlyphTypefaces[glyphTypeface] = new Dictionary<ushort, bool>();
 
            foreach(ushort glyphIndex in glyphRun.GlyphIndices)
            {             
                glyphSet[glyphIndex] = true;
            }
        }
 
        /// <summary>
        /// Returns the collection of glyph typefaces used by the previously added glyph runs.
        /// </summary>
        /// <returns>The collection of glyph typefaces used by the previously added glyph runs.</returns>
        [CLSCompliant(false)]
        public ICollection<Uri> GlyphTypefaceUris
        {
            get
            {
                return _collectedGlyphTypefaces.Keys;
            }
        }
 
        /// <summary>
        /// Obtain the list of glyphs used by the glyph typeface specified by a Uri.
        /// </summary>
        /// <param name="glyphTypeface">Specifies the Uri of a glyph typeface to obtain usage data for.</param>
        /// <returns>A collection of glyph indices recorded previously.</returns>
        /// <exception cref="System.ArgumentException">
        ///     Glyph typeface Uri does not point to a previously recorded glyph typeface.
        /// </exception>
        [CLSCompliant(false)]
        public ICollection<ushort> GetUsedGlyphs(Uri glyphTypeface)
        {
            Dictionary<ushort, bool> glyphsUsed = _collectedGlyphTypefaces[glyphTypeface];
            if (glyphsUsed == null)
            {
                throw new ArgumentException(SR.GlyphTypefaceNotRecorded, nameof(glyphTypeface));
            }
            return glyphsUsed.Keys;
        }
 
        #endregion Public Methods
 
        private class UriComparer : IEqualityComparer<Uri>
        {
            #region IEqualityComparer<Uri> Members
 
            public bool Equals(Uri x, Uri y)
            {
                // We don't use Uri.Equals because it doesn't compare Fragment parts,
                // and we use Fragment part to store font face index.
                return String.Equals(x.ToString(), y.ToString(), StringComparison.OrdinalIgnoreCase);
            }
 
            public int GetHashCode(Uri obj)
            {
                return obj.GetHashCode();
            }
 
            #endregion
        }
 
        //------------------------------------------------------
        //
        //  Private Fields
        //
        //------------------------------------------------------
 
        #region Private Fields
 
        /// <summary>
        /// bool values in the dictionary don't matter,
        /// we'll switch to Set class when it becomes available.
        /// </summary>
        private Dictionary<Uri, Dictionary<ushort, bool>>   _collectedGlyphTypefaces;
 
        private static UriComparer _uriComparer = new UriComparer();
 
        #endregion Private Fields
    }
}