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

using SixLabors.Fonts.Unicode;
using SixLabors.Fonts.WellKnownIds;
using System.Collections.Generic;

namespace SixLabors.Fonts.Tables.General.CMap {
  /// <summary>
  /// Base class for all 'cmap' subtables that map character codes to glyph indices.
  /// <see href="https://learn.microsoft.com/en-us/typography/opentype/spec/cmap"/>
  /// </summary>
  internal abstract class CMapSubTable
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="CMapSubTable"/> class.
      /// </summary>
      public CMapSubTable()
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="CMapSubTable"/> class.
      /// </summary>
      /// <param name="platform">The platform identifier.</param>
      /// <param name="encoding">The platform-specific encoding identifier.</param>
      /// <param name="format">The subtable format number.</param>
      public CMapSubTable(PlatformIDs platform, ushort encoding, ushort format)
      {
          this.Platform = platform;
          this.Encoding = encoding;
          this.Format = format;
      }

      /// <summary>
      /// Gets the subtable format number.
      /// </summary>
      public ushort Format { get; }

      /// <summary>
      /// Gets the platform identifier.
      /// </summary>
      public PlatformIDs Platform { get; }

      /// <summary>
      /// Gets the platform-specific encoding identifier.
      /// </summary>
      public ushort Encoding { get; }

      /// <summary>
      /// Tries to get the glyph identifier for the given code point.
      /// </summary>
      /// <param name="codePoint">The Unicode code point.</param>
      /// <param name="glyphId">When this method returns, contains the glyph identifier if found; otherwise, 0.</param>
      /// <returns><see langword="true"/> if the glyph identifier was found; otherwise, <see langword="false"/>.</returns>
      public abstract bool TryGetGlyphId(CodePoint codePoint, out ushort glyphId);

      /// <summary>
      /// Tries to get the code point for the given glyph identifier.
      /// </summary>
      /// <param name="glyphId">The glyph identifier.</param>
      /// <param name="codePoint">When this method returns, contains the code point if found; otherwise, the default value.</param>
      /// <returns><see langword="true"/> if the code point was found; otherwise, <see langword="false"/>.</returns>
      public abstract bool TryGetCodePoint(ushort glyphId, out CodePoint codePoint);

      /// <summary>
      /// Gets the collection of all available code points in this subtable.
      /// </summary>
      /// <returns>An enumerable of available code point values.</returns>
      public abstract IEnumerable<int> GetAvailableCodePoints();
  }
}