ADOFAIRenderer/Data/DoubleLimit.cs

namespace ADOFAIRenderer.Data;

/// <summary>
/// Base class for double input validation limits.
/// Multiple limits can be composed on a single input field — all are checked in order.
/// </summary>
internal abstract class DoubleLimit
{
    /// <summary>
    /// Validates the given double value against this limit.
    /// </summary>
    /// <param name="value">The parsed double value to validate.</param>
    /// <param name="errorMessage">
    /// When validation fails, set to a human-readable error message.
    /// When validation succeeds, set to null.
    /// </param>
    /// <returns>true if the value satisfies this limit; false otherwise.</returns>
    public abstract bool Validate(double value, out string errorMessage);
}

/// <summary>
/// Requires the double value to be strictly positive (> 0).
/// </summary>
internal class PositiveOnlyDoubleLimit : DoubleLimit
{
    public override bool Validate(double value, out string errorMessage)
    {
        if (value > 0)
        {
            errorMessage = null!;
            return true;
        }

        errorMessage = "Value must be a positive number greater than 0.";
        return false;
    }
}

/// <summary>
/// Requires the double value to be within an inclusive [Min, Max] range.
/// Either bound can be null to represent an unbounded side.
/// </summary>
internal class RangeDoubleLimit : DoubleLimit
{
    // ReSharper disable MemberCanBePrivate.Global
    public double? Min { get; }
    public double? Max { get; }
    // ReSharper restore MemberCanBePrivate.Global

    /// <param name="min">Inclusive lower bound, or null for no lower bound.</param>
    /// <param name="max">Inclusive upper bound, or null for no upper bound.</param>
    public RangeDoubleLimit(double? min, double? max)
    {
        Min = min;
        Max = max;
    }

    public override bool Validate(double value, out string errorMessage)
    {
        if (value < Min)
        {
            errorMessage = Max.HasValue
                ? $"Value must be a number between {Min.Value} and {Max.Value}."
                : $"Value must be a number greater than or equal to {Min.Value}.";
            return false;
        }

        if (value > Max)
        {
            errorMessage = Min.HasValue
                ? $"Value must be a number between {Min.Value} and {Max.Value}."
                : $"Value must be a number less than or equal to {Max.Value}.";
            return false;
        }

        errorMessage = null!;
        return true;
    }
}