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

namespace SixLabors.PolygonClipper {
  /// <summary>
  /// Represents a vertex in the input contour linked list used by the sweep.
  /// </summary>
  /// <remarks>
  /// Vertices are linked in a circular doubly linked list (see <see cref="Prev" /> and
  /// <see cref="Next" />) so the sweep can traverse ascending/descending bounds and
  /// detect local minima/maxima efficiently.
  /// </remarks>
  internal sealed class SweepVertex
  {
#pragma warning disable SA1401 // Hot sweep vertex state uses fields to avoid accessor overhead.
      /// <summary>
      /// The vertex position.
      /// </summary>
      public Vertex Point;

      /// <summary>
      /// The next vertex in the contour.
      /// </summary>
      public SweepVertex? Next;

      /// <summary>
      /// The previous vertex in the contour.
      /// </summary>
      public SweepVertex? Prev;

      /// <summary>
      /// Flags describing sweep-related classification.
      /// </summary>
      public VertexFlags Flags;
#pragma warning restore SA1401

      /// <summary>
      /// Initializes a new instance of the <see cref="SweepVertex"/> class.
      /// </summary>
      public SweepVertex(Vertex point, VertexFlags flags, SweepVertex? prev)
      {
          this.Point = point;
          this.Flags = flags;
          this.Next = null;
          this.Prev = prev;
      }

      /// <summary>
      /// Gets a value indicating whether this vertex is marked as a local maxima.
      /// </summary>
      public bool IsMaxima => (this.Flags & VertexFlags.LocalMax) != 0;
  }
}