using System.Diagnostics;
using System.Text.RegularExpressions;

namespace NATS.Server.Tests;

public class JetStreamApiGapInventoryTests
{
    [Fact]
    public void Parity_map_has_no_unclassified_go_js_api_subjects()
    {
        var gap = JetStreamApiGapInventory.Load();
        gap.UnclassifiedSubjects.ShouldBeEmpty();
    }
}

internal sealed class JetStreamApiGapInventory
{
    public IReadOnlyList<string> UnclassifiedSubjects { get; }

    private JetStreamApiGapInventory(IReadOnlyList<string> unclassifiedSubjects)
    {
        UnclassifiedSubjects = unclassifiedSubjects;
    }

    public static JetStreamApiGapInventory Load()
    {
        var goSubjects = LoadGoSubjects();
        var mappedSubjects = LoadMappedSubjects();

        var unclassified = goSubjects
            .Where(s => !mappedSubjects.Contains(s))
            .OrderBy(s => s, StringComparer.Ordinal)
            .ToArray();

        return new JetStreamApiGapInventory(unclassified);
    }

    private static HashSet<string> LoadGoSubjects()
    {
        var script = Path.Combine(AppContext.BaseDirectory, "../../../../../scripts/jetstream/extract-go-js-api.sh");
        script = Path.GetFullPath(script);
        if (!File.Exists(script))
            throw new FileNotFoundException($"missing script: {script}");

        var psi = new ProcessStartInfo
        {
            FileName = "bash",
            RedirectStandardOutput = true,
            RedirectStandardError = true,
        };
        psi.ArgumentList.Add(script);

        using var process = Process.Start(psi) ?? throw new InvalidOperationException("failed to start inventory script");
        var output = process.StandardOutput.ReadToEnd();
        var errors = process.StandardError.ReadToEnd();
        process.WaitForExit();

        if (process.ExitCode != 0)
            throw new InvalidOperationException($"inventory script failed: {errors}");

        return output
            .Split('\n', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
            .Where(x => x.StartsWith("$JS.API.", StringComparison.Ordinal))
            .ToHashSet(StringComparer.Ordinal);
    }

    private static HashSet<string> LoadMappedSubjects()
    {
        var mapPath = Path.Combine(AppContext.BaseDirectory, "../../../../../docs/plans/2026-02-23-jetstream-remaining-parity-map.md");
        mapPath = Path.GetFullPath(mapPath);
        if (!File.Exists(mapPath))
            throw new FileNotFoundException($"missing parity map: {mapPath}");

        var subjectRegex = new Regex(@"^\|\s*(\$JS\.API[^\|]+?)\s*\|", RegexOptions.Compiled);
        var subjects = new HashSet<string>(StringComparer.Ordinal);

        foreach (var line in File.ReadLines(mapPath))
        {
            var match = subjectRegex.Match(line);
            if (!match.Success)
                continue;

            subjects.Add(match.Groups[1].Value.Trim());
        }

        return subjects;
    }
}