using System.Diagnostics.CodeAnalysis;

namespace MultiversalDiplomacy.Model;

/// <summary>
/// A turn of a game. Essentially a wrapper around <see cref="int"/> for tracking the temporal dimension.
/// </summary>
public struct Turn
{
    /// <summary>
    /// The first turn number.
    /// </summary>
    public const int FIRST_TURN = 0;

    /// <summary>
    /// The first turn.
    /// </summary>
    public static readonly Turn First = new(FIRST_TURN);

    /// <summary>
    /// This turn's number.
    /// </summary>
    private readonly int number;

    public Turn(int number)
    {
        if (number < FIRST_TURN)
        {
            throw new ArgumentException($"Invalid turn number: {number}", nameof(number));
        }
        this.number = number;
    }

    /// <summary>
    /// Returns the turn's string representation as a Diplomacy season.
    /// </summary>
    /// <returns>The season and year as a string, e.g. "Spring 1901".</returns>
    public override string ToString()
        => $"{(number % 2 == 0 ? "Spring" : "Fall")} {1901 + (number / 2)}";

    /// <summary>
    /// Returns a shorter string representation of the turn.
    /// </summary>
    /// <returns>The season and year as a string, e.g. "S'01".</returns>
    public string ToShort()
        => $"{(number % 2 == 0 ? "S" : "F")}'{number / 2:D2}";

    /// <summary>
    /// Returns a value indicating whether this instance is equal to a specified <see cref="Turn"/> value.
    /// </summary>
    /// <returns>true if obj has the same value as this instance; otherwise, false.</returns>
    public override bool Equals([NotNullWhen(true)] object? obj)
        => obj is Turn other
        ? number.Equals(other.number)
        : false;

    /// <summary>
    /// Returns the hash code for this instance.
    /// </summary>
    /// <returns>A 32-bit signed integer hash code.</returns>
    public override int GetHashCode()
        => number.GetHashCode();

    public static int operator -(Turn first, Turn second)
        => Math.Abs(first.number - second.number);

    public static bool operator ==(Turn first, Turn second)
        => first.number == second.number;

    public static bool operator !=(Turn first, Turn second)
        => first.number != second.number;

    public Turn Next => new Turn(number + 1);
}