gregExtractor/Services/RegexCoverageScanner.cs

namespace gregExtractor.Services;

public sealed class RegexCoverageScanner : ICoverageScanner
{
    private static readonly Regex PatchRegex = new(
        @"\[HarmonyPatch\(typeof\(([^)]+)\),\s*nameof\(([^)]+)\)\)\]",
        RegexOptions.Compiled | RegexOptions.CultureInvariant);

    private readonly Dictionary<string, HashSet<string>> _matches = new(StringComparer.Ordinal);

    public IReadOnlyDictionary<string, IReadOnlyCollection<string>> LastScanMatches => _matches
        .ToDictionary(static x => x.Key, static x => (IReadOnlyCollection<string>)x.Value.ToArray(), StringComparer.Ordinal);

    public HashSet<string> ScanImplementedPatches(string[] sourceDirs, IProgress<string>? progress)
    {
        _matches.Clear();

        var keys = new HashSet<string>(StringComparer.Ordinal);
        foreach (string dir in sourceDirs.Where(Directory.Exists))
        {
            foreach (string file in Directory.EnumerateFiles(dir, "*.cs", SearchOption.AllDirectories))
            {
                progress?.Report($"Regex scanning {file}");
                string code = File.ReadAllText(file);

                foreach (Match match in PatchRegex.Matches(code))
                {
                    string typeName = match.Groups[1].Value.Replace("global::", string.Empty).Trim();
                    string methodExpr = match.Groups[2].Value.Trim();
                    int dotIndex = methodExpr.LastIndexOf('.');
                    string methodName = dotIndex >= 0 ? methodExpr[(dotIndex + 1)..].Trim() : methodExpr;

                    if (string.IsNullOrWhiteSpace(typeName) || string.IsNullOrWhiteSpace(methodName))
                        continue;

                    string key = NormalizeKey($"{typeName}::{methodName}");
                    keys.Add(key);

                    if (!_matches.TryGetValue(key, out HashSet<string>? files))
                    {
                        files = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
                        _matches[key] = files;
                    }

                    files.Add(file);
                }
            }
        }

        return keys;
    }

    private static string NormalizeKey(string key)
    {
        return key.Replace(" ", string.Empty);
    }
}