5dplomacy/MultiversalDiplomacy/Model/Season.cs

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namespace MultiversalDiplomacy.Model;
/// <summary>
/// Represents a state of the map produced by a set of move orders on a previous season.
/// </summary>
public class Season
{
/// <summary>
/// A shared counter for handing out new timeline numbers.
/// </summary>
private class TimelineFactory
{
private int nextTimeline = 0;
public int NextTimeline() => nextTimeline++;
}
/// <summary>
/// The first turn number.
/// </summary>
public const int FIRST_TURN = 0;
/// <summary>
/// The season immediately preceding this season.
/// If this season is an alternate timeline root, the past is from the origin timeline.
/// The initial season does not have a past.
/// </summary>
public Season? Past { get; }
/// <summary>
/// The current turn, beginning at 0. Each season (spring and fall) is one turn.
/// Phases that only occur after the fall phase occur when Turn % 2 == 1.
/// The current year is (Turn / 2) + 1901.
/// </summary>
public int Turn { get; }
/// <summary>
/// The timeline to which this season belongs.
/// </summary>
public int Timeline { get; }
/// <summary>
/// The shared timeline number generator.
/// </summary>
private TimelineFactory Timelines { get; }
private Season(Season? past, int turn, int timeline, TimelineFactory factory)
{
this.Past = past;
this.Turn = turn;
this.Timeline = timeline;
this.Timelines = factory;
}
/// <summary>
/// Create a root season at the beginning of time.
/// </summary>
public static Season MakeRoot()
{
TimelineFactory factory = new TimelineFactory();
return new Season(
past: null,
turn: FIRST_TURN,
timeline: factory.NextTimeline(),
factory: factory);
}
/// <summary>
/// Create a season immediately after this one in the same timeline.
/// </summary>
public Season MakeNext()
=> new Season(this, this.Turn + 1, this.Timeline, this.Timelines);
/// <summary>
/// Create a season immediately after this one in a new timeline.
/// </summary>
public Season MakeFork()
=> new Season(this, this.Turn + 1, this.Timelines.NextTimeline(), this.Timelines);
/// <summary>
/// Returns the first season in this season's timeline. The first season is the
/// root of the first timeline. The earliest season in each alternate timeline is
/// the root of that timeline.
/// </summary>
public Season TimelineRoot()
=> this.Past != null && this.Timeline == this.Past.Timeline
? this.Past.TimelineRoot()
: this;
/// <summary>
/// Returns whether this season is in an adjacent timeline to another season.
/// </summary>
public bool InAdjacentTimeline(Season other)
{
// Timelines are adjacent to themselves. Early out in that case.
if (this.Timeline == other.Timeline) return true;
// If the timelines aren't identical, one of them isn't the initial trunk.
// They can still be adjacent if one of them branched off of the other, or
// if they both branched off of the same point.
Season thisRoot = this.TimelineRoot();
Season otherRoot = other.TimelineRoot();
return // One branched off the other
thisRoot.Past?.Timeline == other.Timeline
|| otherRoot.Past?.Timeline == this.Timeline
// Both branched off of the same point
|| thisRoot.Past == otherRoot.Past;
}
}