using System.Collections.Concurrent;
using System.Text;
using System.Text.RegularExpressions;

namespace MxGateway.Server.Galaxy;

public static class GalaxyGlobMatcher
{
    /// <summary>
    ///     Compiled-regex cache keyed by glob pattern. <c>IsMatch</c> is called once per
    ///     object per <c>DiscoverHierarchy</c>/<c>WatchDeployEvents</c> evaluation, so the
    ///     same handful of glob patterns are translated repeatedly; caching avoids
    ///     rebuilding and recompiling the regex on every call.
    /// </summary>
    private static readonly ConcurrentDictionary<string, Regex> RegexCache = new(StringComparer.Ordinal);

    public static bool IsMatch(string value, string glob)
    {
        if (string.IsNullOrWhiteSpace(glob))
        {
            return true;
        }

        return GetOrCreateRegex(glob).IsMatch(value ?? string.Empty);
    }

    private static Regex GetOrCreateRegex(string glob)
    {
        return RegexCache.GetOrAdd(glob, static pattern => new Regex(
            BuildRegex(pattern),
            RegexOptions.CultureInvariant | RegexOptions.IgnoreCase | RegexOptions.Compiled,
            TimeSpan.FromMilliseconds(100)));
    }

    private static string BuildRegex(string glob)
    {
        StringBuilder builder = new("^", glob.Length + 2);
        foreach (char character in glob)
        {
            switch (character)
            {
                case '*':
                    builder.Append(".*");
                    break;
                case '?':
                    builder.Append('.');
                    break;
                default:
                    builder.Append(Regex.Escape(character.ToString()));
                    break;
            }
        }

        builder.Append('$');
        return builder.ToString();
    }
}