SpdxHelpers.cs

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using System.Text.RegularExpressions;

namespace DemaConsulting.SpdxModel;

internal static partial class SpdxHelpers
{
#if NET7_0_OR_GREATER
    /// <summary>
    ///     Regular expression for checking date/time formats (source-generated for .NET 7+)
    /// </summary>
    [GeneratedRegex(@"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$", RegexOptions.None, 100)]
    private static partial Regex DateTimeRegex();
#else
    /// <summary>
    ///     Cached regular expression instance for checking date/time formats (pre-.NET 7 fallback)
    /// </summary>
    private static readonly Regex DateTimeRegexInstance =
        new Regex(@"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$", RegexOptions.None, TimeSpan.FromMilliseconds(100));

    /// <summary>
    ///     Regular expression for checking date/time formats
    /// </summary>
    /// <returns>Compiled <see cref="Regex"/> instance</returns>
    private static Regex DateTimeRegex() => DateTimeRegexInstance;
#endif

    /// <summary>
    ///     Test if a string is a valid SPDX date/time field (which include null/empty)
    /// </summary>
    /// <param name="value">String value</param>
    /// <returns>True if valid</returns>
    internal static bool IsValidSpdxDateTime(string? value)
    {
        return string.IsNullOrEmpty(value) || DateTimeRegex().IsMatch(value);
    }

    /// <summary>
    ///     This method picks the best string.
    /// </summary>
    /// <param name="values">String values to pick from</param>
    /// <returns>Best string</returns>
    internal static string? EnhanceString(params string?[] values)
    {
        // Return the value with the highest fitness
        return values
            .Select(value => (
                Value: value,
                Fitness: value switch
                {
                    null => 0,
                    "" => 1,
                    SpdxElement.NoAssertion => 2,
                    _ => 3
                }))
            .OrderByDescending(x => x.Fitness)
            .FirstOrDefault().Value;
    }
}