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

using System.Diagnostics.CodeAnalysis;
using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;

namespace SixLabors.Fonts.Tables.AdvancedTypographic {
  /// <summary>
  /// The GDEF table contains three kinds of information in subtables:
  /// 1. glyph class definitions that classify different types of glyphs in a font;
  /// 2. attachment point lists that identify glyph positioning attachments for each glyph;
  /// and 3. ligature caret lists that provide information for caret positioning and text selection involving ligatures.
  /// <see href="https://docs.microsoft.com/en-us/typography/opentype/spec/gdef"/>
  /// </summary>
  internal sealed class GlyphDefinitionTable : Table
  {
      /// <summary>
      /// The OpenType table tag for the GDEF table.
      /// </summary>
      internal const string TableName = "GDEF";

      /// <summary>
      /// Gets the class definition table for glyph types (base, ligature, mark, component).
      /// </summary>
      public ClassDefinitionTable? GlyphClassDefinition { get; private set; }

      /// <summary>
      /// Gets the attachment point list table for identifying glyph attachment points.
      /// </summary>
      public AttachmentListTable? AttachmentListTable { get; private set; }

      /// <summary>
      /// Gets the ligature caret list table for positioning carets within ligatures.
      /// </summary>
      public LigatureCaretList? LigatureCaretList { get; private set; }

      /// <summary>
      /// Gets the class definition table for mark attachment types.
      /// </summary>
      public ClassDefinitionTable? MarkAttachmentClassDef { get; private set; }

      /// <summary>
      /// Gets the mark glyph sets table for filtering marks during lookup processing.
      /// </summary>
      public MarkGlyphSetsTable? MarkGlyphSetsTable { get; private set; }

      /// <summary>
      /// Gets the item variation store table for variable font GDEF variations.
      /// </summary>
      public ItemVariationStore? ItemVariationStore { get; private set; }

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

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

      /// <summary>
      /// Tries to get the glyph class for the specified glyph.
      /// </summary>
      /// <param name="glyphId">The glyph identifier.</param>
      /// <param name="glyphClass">When this method returns, contains the glyph class if found.</param>
      /// <returns><see langword="true"/> if the glyph class was found; otherwise, <see langword="false"/>.</returns>
      public bool TryGetGlyphClass(ushort glyphId, [NotNullWhen(true)] out GlyphClassDef? glyphClass)
      {
          glyphClass = null;

          if (this.GlyphClassDefinition is null)
          {
              return false;
          }

          glyphClass = (GlyphClassDef)this.GlyphClassDefinition.ClassIndexOf(glyphId);
          return true;
      }

      /// <summary>
      /// Tries to get the mark attachment class for the specified glyph.
      /// </summary>
      /// <param name="glyphId">The glyph identifier.</param>
      /// <param name="markAttachmentClass">When this method returns, contains the mark attachment class if found.</param>
      /// <returns><see langword="true"/> if the mark attachment class was found; otherwise, <see langword="false"/>.</returns>
      public bool TryGetMarkAttachmentClass(ushort glyphId, [NotNullWhen(true)] out GlyphClassDef? markAttachmentClass)
      {
          markAttachmentClass = null;

          if (this.MarkAttachmentClassDef is null)
          {
              return false;
          }

          markAttachmentClass = (GlyphClassDef)this.MarkAttachmentClassDef.ClassIndexOf(glyphId);
          return true;
      }

      /// <summary>
      /// Determines whether the specified glyph belongs to the given mark glyph set.
      /// </summary>
      /// <param name="markGlyphSetIndex">The index of the mark glyph set.</param>
      /// <param name="glyphId">The glyph identifier.</param>
      /// <returns><see langword="true"/> if the glyph is in the set; otherwise, <see langword="false"/>.</returns>
      public bool IsInMarkGlyphSet(ushort markGlyphSetIndex, ushort glyphId)
          => this.MarkGlyphSetsTable?.Contains(markGlyphSetIndex, glyphId) == true;

      /// <summary>
      /// Loads the <see cref="GlyphDefinitionTable"/> from a big endian binary reader.
      /// </summary>
      /// <param name="reader">The big endian binary reader.</param>
      /// <returns>The <see cref="GlyphDefinitionTable"/>.</returns>
      public static GlyphDefinitionTable Load(BigEndianBinaryReader reader)
      {
          // Header version 1.0
          // Type      | Name                     | Description
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // uint16    | majorVersion             | Major version of the GDEF table, = 1
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // uint16    | minorVersion             | Minor version of the GDEF table, = 0
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | glyphClassDefOffset      | Offset to class definition table for glyph type, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | attachListOffset         | Offset to attachment point list table, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | ligCaretListOffset       | Offset to ligature caret list table, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | markAttachClassDefOffset | Offset to class definition table for mark attachment type, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------

          // Header version 1.2
          // Type      | Name                     | Description
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // uint16    | majorVersion             | Major version of the GDEF table, = 1
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // uint16    | minorVersion             | Minor version of the GDEF table, = 0
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | glyphClassDefOffset      | Offset to class definition table for glyph type, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | attachListOffset         | Offset to attachment point list table, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | ligCaretListOffset       | Offset to ligature caret list table, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | markAttachClassDefOffset | Offset to class definition table for mark attachment type, from beginning of GDEF header (may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | markGlyphSetsDefOffset   | Offset to the table of mark glyph set definitions, from beginning of GDEF header (may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------

          // Header version 1.3
          // Type      | Name                     | Description
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // uint16    | majorVersion             | Major version of the GDEF table, = 1
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // uint16    | minorVersion             | Minor version of the GDEF table, = 0
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | glyphClassDefOffset      | Offset to class definition table for glyph type, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | attachListOffset         | Offset to attachment point list table, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | ligCaretListOffset       | Offset to ligature caret list table, from beginning of GDEF header(may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | markAttachClassDefOffset | Offset to class definition table for mark attachment type, from beginning of GDEF header (may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset16  | markGlyphSetsDefOffset   | Offset to the table of mark glyph set definitions, from beginning of GDEF header (may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          // Offset32  | itemVarStoreOffset       | Offset to the Item Variation Store table, from beginning of GDEF header (may be NULL).
          // ----------|--------------------------|--------------------------------------------------------------------------------------------------------
          ushort majorVersion = reader.ReadUInt16();
          ushort minorVersion = reader.ReadUInt16();

          ushort glyphClassDefOffset = reader.ReadUInt16();
          ushort attachListOffset = reader.ReadUInt16();
          ushort ligatureCaretListOffset = reader.ReadOffset16();
          ushort markAttachClassDefOffset = reader.ReadOffset16();
          ushort markGlyphSetsDefOffset = 0;
          uint itemVarStoreOffset = 0;

          switch (minorVersion)
          {
              case 0:
                  break;
              case 2:
                  markGlyphSetsDefOffset = reader.ReadUInt16();
                  break;
              case 3:
                  markGlyphSetsDefOffset = reader.ReadUInt16();
                  itemVarStoreOffset = reader.ReadUInt32();
                  break;
              default:
                  throw new InvalidFontFileException($"Invalid value for 'minor version' {minorVersion} of GDEF table. Should be '0', '2' or '3'.");
          }

          ClassDefinitionTable.TryLoad(reader, glyphClassDefOffset, out ClassDefinitionTable? classDefinitionTable);
          AttachmentListTable? attachmentListTable = attachListOffset is 0 ? null : AttachmentListTable.Load(reader, attachListOffset);
          LigatureCaretList? ligatureCaretList = ligatureCaretListOffset is 0 ? null : LigatureCaretList.Load(reader, ligatureCaretListOffset);
          ClassDefinitionTable.TryLoad(reader, markAttachClassDefOffset, out ClassDefinitionTable? markAttachmentClassDef);
          MarkGlyphSetsTable? markGlyphSetsTable = markGlyphSetsDefOffset is 0 ? null : MarkGlyphSetsTable.Load(reader, markGlyphSetsDefOffset);

          ItemVariationStore? itemVariationStore = null;
          if (itemVarStoreOffset != 0)
          {
              itemVariationStore = ItemVariationStore.Load(reader, itemVarStoreOffset);
          }

          return new GlyphDefinitionTable()
          {
              GlyphClassDefinition = classDefinitionTable,
              AttachmentListTable = attachmentListTable,
              LigatureCaretList = ligatureCaretList,
              MarkAttachmentClassDef = markAttachmentClassDef,
              MarkGlyphSetsTable = markGlyphSetsTable,
              ItemVariationStore = itemVariationStore
          };
      }
  }
}