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

using System.IO;

namespace SixLabors.Fonts.Tables.AdvancedTypographic.GPos {
  /// <summary>
  /// The LigatureArray table contains a count (ligatureCount) and an array of offsets (ligatureAttachOffsets) to LigatureAttach tables.
  /// The ligatureAttachOffsets array lists the offsets to LigatureAttach tables, one for each ligature glyph listed in the ligatureCoverage table,
  /// in the same order as the ligatureCoverage index.
  /// </summary>
  internal class LigatureArrayTable
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="LigatureArrayTable"/> class.
      /// </summary>
      /// <param name="reader">The big endian binary reader.</param>
      /// <param name="offset">The offset to the start of the ligature array table.</param>
      /// <param name="markClassCount">Number of defined mark classes.</param>
      public LigatureArrayTable(BigEndianBinaryReader reader, long offset, ushort markClassCount)
      {
          // +--------------+--------------------------------------+--------------------------------------------------------------------------------------+
          // | Type         | Name                                 | Description                                                                          |
          // +==============+======================================+======================================================================================+
          // | uint16       | ligatureCount                        | Number of LigatureAttach table offsets.                                              |
          // +--------------+--------------------------------------+--------------------------------------------------------------------------------------+
          // | Offset16     | ligatureAttachOffsets[ligatureCount] | Array of offsets to LigatureAttach tables. Offsets are from beginning of             |
          // |              |                                      | LigatureArray table, ordered by ligatureCoverage index.                              |
          // +--------------+--------------------------------------+--------------------------------------------------------------------------------------+
          reader.Seek(offset, SeekOrigin.Begin);
          ushort ligatureCount = reader.ReadUInt16();
          this.LigatureAttachTables = new LigatureAttachTable[ligatureCount];
          ushort[] ligatureAttachOffsets = new ushort[ligatureCount];
          for (int i = 0; i < ligatureCount; i++)
          {
              ligatureAttachOffsets[i] = reader.ReadOffset16();
          }

          for (int i = 0; i < ligatureCount; i++)
          {
              this.LigatureAttachTables[i] = new LigatureAttachTable(reader, markClassCount, offset + ligatureAttachOffsets[i]);
          }
      }

      /// <summary>
      /// Gets the array of LigatureAttach tables, one per ligature glyph, in the same order as the ligature Coverage index.
      /// </summary>
      public LigatureAttachTable[] LigatureAttachTables { get; }
  }
}