// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System;
using System.Globalization;
using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
using SixLabors.Fonts.Tables.General.Name;
using SixLabors.Fonts.WellKnownIds;

namespace SixLabors.Fonts.Tables.Cff {
  /// <summary>
  /// Represents the Compact Font Format (CFF) version 2 table.
  /// <see href="https://learn.microsoft.com/en-us/typography/opentype/spec/cff2"/>
  /// </summary>
  internal sealed class Cff2Table : Table, ICffTable
  {
      internal const string TableName = "CFF2";

      private readonly CffGlyphData[] glyphs;

      /// <summary>
      /// Initializes a new instance of the <see cref="Cff2Table"/> class.
      /// </summary>
      /// <param name="cffFont">The parsed CFF font.</param>
      /// <param name="itemVariationStore">The item variation store for font variations.</param>
      public Cff2Table(CffFont cffFont, ItemVariationStore itemVariationStore)
      {
          this.glyphs = cffFont.Glyphs;
          this.ItemVariationStore = itemVariationStore;
      }

      /// <inheritdoc/>
      public int GlyphCount => this.glyphs.Length;

      /// <inheritdoc/>
      public ItemVariationStore ItemVariationStore { get; }

      /// <inheritdoc/>
      public CffGlyphData GetGlyph(int index)
          => this.glyphs[index];

      /// <summary>
      /// Loads the CFF2 table from the specified font reader.
      /// </summary>
      /// <param name="fontReader">The font reader.</param>
      /// <returns>The <see cref="Cff2Table"/>, or <see langword="null"/> if the table is not present.</returns>
      public static Cff2Table? Load(FontReader fontReader)
      {
          if (!fontReader.TryGetReaderAtTablePosition(TableName, out BigEndianBinaryReader? binaryReader))
          {
              return null;
          }

          NameTable nameTable = fontReader.GetTable<NameTable>();
          string fontName = nameTable.GetNameById(CultureInfo.InvariantCulture, KnownNameIds.PostscriptName);

          using (binaryReader)
          {
              return Load(binaryReader, fontName);
          }
      }

      /// <summary>
      /// Loads the CFF2 table from the specified binary reader.
      /// </summary>
      /// <param name="reader">The big-endian binary reader positioned at the CFF2 table header.</param>
      /// <param name="fontName">The PostScript font name.</param>
      /// <returns>The <see cref="Cff2Table"/>.</returns>
      public static Cff2Table Load(BigEndianBinaryReader reader, string fontName)
      {
          long position = reader.BaseStream.Position;
          byte major = reader.ReadUInt8();
          byte minor = reader.ReadUInt8();
          byte hdrSize = reader.ReadUInt8();
          ushort topDictLength = reader.ReadUInt16();

          switch (major)
          {
              case 2:
                  Cff2Parser parser = new();
                  Cff2Font cffFont = parser.Load(reader, hdrSize, topDictLength, fontName, position);
                  return new(cffFont, cffFont.ItemVariationStore);

              default:
                  throw new NotSupportedException("CFF version 2 is expected");
          }
      }
  }
}