using System.Text.RegularExpressions;
using StellaOps.BinaryIndex.Core.Models;
using StellaOps.BinaryIndex.FixIndex.Models;

namespace StellaOps.BinaryIndex.FixIndex.Parsers;

/// <summary>
/// Parses Alpine APKBUILD secfixes section for CVE fix evidence.
/// </summary>
/// <remarks>
/// APKBUILD secfixes format:
/// # secfixes:
/// #   1.2.3-r0:
/// #     - CVE-2024-1234
/// #     - CVE-2024-1235
/// </remarks>
public sealed partial class AlpineSecfixesParser : ISecfixesParser
{
    [GeneratedRegex(@"^#\s*secfixes:\s*$", RegexOptions.Compiled | RegexOptions.Multiline)]
    private static partial Regex SecfixesPatternRegex();

    [GeneratedRegex(@"^#\s+(\d+\.\d+[^:]*):$", RegexOptions.Compiled)]
    private static partial Regex VersionPatternRegex();

    [GeneratedRegex(@"^#\s+-\s+(CVE-\d{4}-\d{4,7})$", RegexOptions.Compiled)]
    private static partial Regex CvePatternRegex();

    /// <summary>
    /// Parses APKBUILD secfixes section for version-to-CVE mappings.
    /// </summary>
    public IEnumerable<FixEvidence> Parse(
        string apkbuild,
        string distro,
        string release,
        string sourcePkg)
    {
        if (string.IsNullOrWhiteSpace(apkbuild))
            yield break;

        var lines = apkbuild.Split('\n');
        var inSecfixes = false;
        string? currentVersion = null;

        foreach (var line in lines)
        {
            if (SecfixesPatternRegex().IsMatch(line))
            {
                inSecfixes = true;
                continue;
            }

            if (!inSecfixes)
                continue;

            // Exit secfixes block on non-comment line
            if (!line.TrimStart().StartsWith('#'))
            {
                inSecfixes = false;
                continue;
            }

            var versionMatch = VersionPatternRegex().Match(line);
            if (versionMatch.Success)
            {
                currentVersion = versionMatch.Groups[1].Value;
                continue;
            }

            var cveMatch = CvePatternRegex().Match(line);
            if (cveMatch.Success && currentVersion != null)
            {
                yield return new FixEvidence
                {
                    Distro = distro,
                    Release = release,
                    SourcePkg = sourcePkg,
                    CveId = cveMatch.Groups[1].Value,
                    State = FixState.Fixed,
                    FixedVersion = currentVersion,
                    Method = FixMethod.SecurityFeed, // APKBUILD is authoritative
                    Confidence = 0.95m,
                    Evidence = new SecurityFeedEvidence
                    {
                        FeedId = "alpine-secfixes",
                        EntryId = $"{sourcePkg}/{currentVersion}",
                        PublishedAt = DateTimeOffset.UtcNow
                    },
                    CreatedAt = DateTimeOffset.UtcNow
                };
            }
        }
    }
}