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

using System;
using System.Runtime.CompilerServices;

namespace SixLabors.PolygonClipper {
  /// <summary>
  /// Represents a line segment on a plane.
  /// </summary>
  internal readonly struct Segment : IEquatable<Segment>
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="Segment"/> struct.
      /// </summary>
      /// <param name="source">The segment source.</param>
      /// <param name="target">The segment target.</param>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public Segment(in Vertex source, in Vertex target)
      {
          this.Source = source;
          this.Target = target;
          this.Min = Vertex.Min(source, target);
          this.Max = Vertex.Max(source, target);
      }

      /// <summary>
      /// Gets the segment source vector.
      /// </summary>
      public Vertex Source { get; }

      /// <summary>
      /// Gets the segment target vector.
      /// </summary>
      public Vertex Target { get; }

      /// <summary>
      /// Gets the point of the segment with lexicographically smallest coordinate.
      /// </summary>
      public Vertex Min { get; }

      /// <summary>
      /// Gets the point of the segment with lexicographically largest coordinate.
      /// </summary>
      public Vertex Max { get; }

      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public static bool operator ==(in Segment left, in Segment right)
          => left.Equals(right);

      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public static bool operator !=(in Segment left, in Segment right)
          => !(left == right);

      /// <summary>
      /// Gets a value indicating whether the segment is degenerate.
      /// </summary>
      /// <returns>
      /// <see langword="true"/> if the segment is degenerate; otherwise <see langword="false"/>.
      /// </returns>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public bool IsDegenerate() => this.Source.Equals(this.Target);

      /// <summary>
      /// Gets a value indicating whether the segment is vertical.
      /// </summary>
      /// <returns>
      /// <see langword="true"/> if the segment is vertical; otherwise <see langword="false"/>.
      /// </returns>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public bool IsVertical() => this.Source.X == this.Target.X;

      /// <summary>
      /// Changes the segment orientation.
      /// </summary>
      /// <returns>The <see cref="Segment"/>.</returns>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public Segment Reverse()
          => new(this.Target, this.Source);

      /// <inheritdoc/>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public override bool Equals(object? obj)
          => obj is Segment segment && this.Equals(segment);

      /// <inheritdoc/>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public bool Equals(Segment other)
          => this.Source.Equals(other.Source) && this.Target.Equals(other.Target);

      /// <inheritdoc/>
      public override int GetHashCode()
          => HashCode.Combine(this.Source, this.Target);
  }
}