Trail.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Terraria.DataStructures;

namespace OriMod;

/// <summary>
/// Class for containing and updating all <see cref="TrailSegment"/>s on an <see cref="OriPlayer"/>.
/// </summary>
public class Trail {
  /// <summary>
  /// Create an instance of <see cref="Trail"/> that will belong to <paramref name="oPlayer"/>.
  /// </summary>
  /// <param name="oPlayer">The <see cref="OriPlayer"/> this <see cref="Trail"/> will belong to.</param>
  /// <exception cref="ArgumentNullException"><paramref name="oPlayer"/> is <see langword="null"/>.</exception>
  internal Trail(OriPlayer oPlayer) {
    ArgumentNullException.ThrowIfNull(oPlayer);

    _segments = new TrailSegment[Count];
    int i = 0;
    while (i < Count) {
      _segments[i++] = new TrailSegment(oPlayer);
    }
  }

  /// <summary>
  /// Sets <see cref="_index"/> to the next index in <see cref="_segments"/>, and returns the value.
  /// </summary>
  /// <returns>The updated value of <see cref="_index"/>.</returns>
  private int NextIndex() {
    _index = (_index + 1) % _segments.Length;
    return _index;
  }

  /// <summary>
  /// All <see cref="TrailSegment"/>s in this <see cref="Trail"/>.
  /// </summary>
  private readonly TrailSegment[] _segments;

  /// <summary>
  /// Current <see cref="_segments"/> index. Used for <see cref="TrailSegment.Reset"/>.
  /// </summary>
  private int _index;

  internal bool hasDrawnThisFrame;

  /// <summary>
  /// Number of segments in a trail.
  /// </summary>
  public static int Count => 26;

  /// <summary>
  /// Call <see cref="TrailSegment.Tick"/> on each <see cref="TrailSegment"/>.
  /// <para>This keeps the opacity of the trail appearing consistent.</para>
  /// </summary>
  public void UpdateSegments() {
    foreach (TrailSegment segment in _segments) {
      segment.Tick();
    }
  }

  /// <summary>
  /// <see cref="IEnumerable{T}"/> of all <see cref="DrawData"/>s from this trail.
  /// </summary>
  public IEnumerable<DrawData> TrailDrawDatas => _segments.Select(segment => segment.GetDrawData());

  /// <summary>
  /// Calls <see cref="TrailSegment.Reset"/> on the next segment.
  /// </summary>
  internal void ResetNextSegment() {
    _segments[NextIndex()].Reset();
  }

  /// <summary>
  /// Call to wipe player's trail completely
  /// </summary>
  public void DecayAllSegments() {
    foreach (TrailSegment segment in _segments) {
      segment.Decay();
    }
  }
}