namespace Mr.BrickAdventures.Progression;

/// <summary>
/// A non-negative quantity of coins. Amounts only — there is no signed coin value; a shortfall is
/// a failed subtraction the caller must handle, never a negative total.
/// </summary>
public readonly struct Coins : IEquatable<Coins>
{
    public int Value { get; }

    private Coins(int value) => Value = value;

    public static Coins Of(int value) => value < 0
        ? throw new ArgumentOutOfRangeException(nameof(value), value, "Coins cannot be negative.")
        : new Coins(value);

    /// <summary>
    /// Subtracts <paramref name="amount"/>. Returns false when the amount exceeds what is held,
    /// leaving <paramref name="remaining"/> untouched rather than clamping to zero.
    /// </summary>
    public bool TrySubtract(Coins amount, out Coins remaining)
    {
        if (amount.Value > Value)
        {
            remaining = this;
            return false;
        }

        remaining = new Coins(Value - amount.Value);
        return true;
    }

    public bool Equals(Coins other) => Value == other.Value;
    public override bool Equals(object? obj) => obj is Coins other && Equals(other);
    public override int GetHashCode() => Value;
    public override string ToString() => Value.ToString();
}