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

namespace SixLabors.Fonts.Tables {
  /// <summary>
  /// Represents a single entry in the WOFF2 triplet encoding table, which defines how
  /// glyph coordinate triplets (flag, x, y) are packed into a compact binary representation.
  /// <see href="https://www.w3.org/TR/WOFF2/#triplet_encoding"/>
  /// </summary>
  internal readonly struct TripleEncodingRecord
  {
      /// <summary>The total number of bytes for this triplet (flag + x + y).</summary>
      public readonly byte ByteCount;

      /// <summary>The number of bits used to encode the X coordinate value.</summary>
      public readonly byte XBits;

      /// <summary>The number of bits used to encode the Y coordinate value.</summary>
      public readonly byte YBits;

      /// <summary>The delta offset added to the raw X coordinate value before applying the sign.</summary>
      public readonly ushort DeltaX;

      /// <summary>The delta offset added to the raw Y coordinate value before applying the sign.</summary>
      public readonly ushort DeltaY;

      /// <summary>The sign multiplier for the X coordinate (-1, 0, or 1).</summary>
      public readonly sbyte Xsign;

      /// <summary>The sign multiplier for the Y coordinate (-1, 0, or 1).</summary>
      public readonly sbyte Ysign;

      /// <summary>
      /// Initializes a new instance of the <see cref="TripleEncodingRecord"/> struct.
      /// </summary>
      /// <param name="byteCount">The total byte count for this triplet.</param>
      /// <param name="xbits">The number of bits for the X coordinate.</param>
      /// <param name="ybits">The number of bits for the Y coordinate.</param>
      /// <param name="deltaX">The delta offset for X.</param>
      /// <param name="deltaY">The delta offset for Y.</param>
      /// <param name="xsign">The sign multiplier for X.</param>
      /// <param name="ysign">The sign multiplier for Y.</param>
      public TripleEncodingRecord(
          byte byteCount,
          byte xbits,
          byte ybits,
          ushort deltaX,
          ushort deltaY,
          sbyte xsign,
          sbyte ysign)
      {
          this.ByteCount = byteCount;
          this.XBits = xbits;
          this.YBits = ybits;
          this.DeltaX = deltaX;
          this.DeltaY = deltaY;
          this.Xsign = xsign;
          this.Ysign = ysign;
      }

      /// <summary>
      /// Transforms a raw X coordinate value using the delta and sign from this record.
      /// </summary>
      /// <param name="orgX">The raw X coordinate value read from the stream.</param>
      /// <returns>The signed, delta-adjusted X coordinate.</returns>
      public int Tx(int orgX) => (orgX + this.DeltaX) * this.Xsign;

      /// <summary>
      /// Transforms a raw Y coordinate value using the delta and sign from this record.
      /// </summary>
      /// <param name="orgY">The raw Y coordinate value read from the stream.</param>
      /// <returns>The signed, delta-adjusted Y coordinate.</returns>
      public int Ty(int orgY) => (orgY + this.DeltaY) * this.Ysign;
  }
}