using System.Formats.Tar;
using System.IO.Compression;

namespace ControlPlane.Api.Services;

/// <summary>
/// Creates a gzipped tar stream from a directory, respecting .dockerignore rules.
/// Used to supply the Docker build context to the Docker SDK.
/// </summary>
internal static class TarHelper
{
    private static readonly string[] DefaultIgnore =
    [
        ".git", ".vs", ".vscode", "node_modules", "bin", "obj",
        "VaultData", "*.user", "*.suo",
    ];

    public static void Pack(string root, Stream destination)
    {
        var ignorePatterns = LoadDockerIgnore(root);

        using var gz  = new GZipStream(destination, CompressionLevel.Fastest, leaveOpen: true);
        using var tar = new TarWriter(gz, TarEntryFormat.Gnu, leaveOpen: false);

        foreach (var file in Directory.EnumerateFiles(root, "*", SearchOption.AllDirectories))
        {
            var relative = Path.GetRelativePath(root, file).Replace('\\', '/');

            if (ShouldIgnore(relative, ignorePatterns))
                continue;

            var entry = new GnuTarEntry(TarEntryType.RegularFile, relative)
            {
                DataStream = File.OpenRead(file),
            };
            tar.WriteEntry(entry);
        }
    }

    private static List<string> LoadDockerIgnore(string root)
    {
        var path = Path.Combine(root, ".dockerignore");
        var patterns = new List<string>(DefaultIgnore);
        if (!File.Exists(path)) return patterns;

        foreach (var line in File.ReadAllLines(path))
        {
            var trimmed = line.Trim();
            if (!string.IsNullOrEmpty(trimmed) && !trimmed.StartsWith('#'))
                patterns.Add(trimmed);
        }
        return patterns;
    }

    private static bool ShouldIgnore(string relativePath, List<string> patterns)
    {
        var segments = relativePath.Split('/');

        foreach (var pattern in patterns)
        {
            var p = pattern.TrimStart('/').TrimEnd('/');

            // Glob suffix match (e.g. *.user)
            if (p.StartsWith('*'))
            {
                if (relativePath.EndsWith(p[1..], StringComparison.OrdinalIgnoreCase))
                    return true;
                continue;
            }

            // Exact full-path match or root-anchored prefix (e.g. .git, .vs)
            if (relativePath.Equals(p, StringComparison.OrdinalIgnoreCase))
                return true;
            if (relativePath.StartsWith(p + "/", StringComparison.OrdinalIgnoreCase))
                return true;

            // Match any path segment so that nested bin/, obj/, node_modules/ etc. are caught
            // regardless of which project subdirectory they live in.
            if (segments.Any(seg => seg.Equals(p, StringComparison.OrdinalIgnoreCase)))
                return true;
        }
        return false;
    }
}