namespace ErsatzTV.Core.Domain;

/// <summary>
///     Bounds for a multi-collection member's per-source <c>Weight</c> (#70).
///     <para>
///         The floor is <b>1, not 0</b>. A weight is a <i>share of airtime</i>, and 0 has no meaning on that scale —
///         "don't play this source" is expressed by removing it from the multi collection, not by weighting it to
///         nothing. Rejecting it here keeps that intent from being expressed in a way the rotation would have to
///         interpret. <c>WeightedShuffleCollectionEnumerator</c> independently clamps to this range rather than
///         trusting it, so a row that predates this gate rotates at the floor instead of vanishing; the two are
///         belt-and-braces, not duplicates — <b>neither is redundant</b>.
///     </para>
///     <para>
///         The ceiling is the same argument as the floor, not an arithmetic guard. A weight of a billion is not a
///         share of airtime any more than 0 is, so it is refused at the boundary rather than silently reinterpreted.
///         The rotation arithmetic is made safe by <c>EffectiveWeight</c>'s clamp (and by <c>CycleLength</c> summing
///         to <c>long</c>) — <b>not</b> by this constant: with the clamp in place a sum cannot overflow whatever the
///         stored value is, which is exactly why a row that predates this gate is still safe.
///         <c>An_Enormous_Weight_Does_Not_Overflow_The_Rotation</c> pins that.
///     </para>
/// </summary>
public static class MultiCollectionItemWeight
{
    public const int Minimum = 1;
    public const int Maximum = 1000;
    public const int Default = 1;

    public static bool IsValid(int weight) => weight is >= Minimum and <= Maximum;

    public static string ValidationMessage =>
        $"Weight must be between {Minimum} and {Maximum}";
}