using System.Globalization;

namespace LibNftables.Tests;

internal static class NativeTestSupport
{
    private const string PrivilegedTestsEnvironmentVariable = "LIBNFTABLES_RUN_PRIVILEGED_TESTS";

    internal static bool IsRunningAsRoot()
    {
        if (!OperatingSystem.IsLinux())
        {
            return false;
        }

        try
        {
            foreach (var line in File.ReadLines("/proc/self/status"))
            {
                if (!line.StartsWith("Uid:", StringComparison.Ordinal))
                {
                    continue;
                }

                var parts = line["Uid:".Length..]
                    .Split((char[]?)null, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);

                return parts.Length > 0 && parts[0] == "0";
            }
        }
        catch
        {
            // If uid probing fails, keep tests conservative.
        }

        return false;
    }

    internal static bool PrivilegedTestsRequested()
    {
        var value = Environment.GetEnvironmentVariable(PrivilegedTestsEnvironmentVariable);
        if (string.IsNullOrWhiteSpace(value))
        {
            return false;
        }

        return value.Equals("1", StringComparison.Ordinal)
            || value.Equals("true", StringComparison.OrdinalIgnoreCase)
            || value.Equals("yes", StringComparison.OrdinalIgnoreCase);
    }

    internal static bool ShouldRunPrivilegedTests()
    {
        return PrivilegedTestsRequested()
            && IsRunningAsRoot()
            && HasCapNetAdmin();
    }

    internal static bool HasCapNetAdmin()
    {
        const int capNetAdminBit = 12;
        const ulong mask = 1UL << capNetAdminBit;

        try
        {
            foreach (var line in File.ReadLines("/proc/self/status"))
            {
                if (!line.StartsWith("CapEff:", StringComparison.Ordinal))
                {
                    continue;
                }

                var hex = line["CapEff:".Length..].Trim();
                if (ulong.TryParse(hex, NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture, out var value))
                {
                    return (value & mask) != 0;
                }
            }
        }
        catch
        {
            // If capability probing fails, keep tests conservative.
        }

        return false;
    }

    internal static bool TryCreateContext(out NftContext context)
    {
        try
        {
            context = new NftContext();
            return true;
        }
        catch (DllNotFoundException)
        {
            context = null!;
            return false;
        }
        catch (TypeInitializationException ex) when (ex.InnerException is DllNotFoundException)
        {
            context = null!;
            return false;
        }
        catch (BadImageFormatException)
        {
            context = null!;
            return false;
        }
        catch (EntryPointNotFoundException)
        {
            context = null!;
            return false;
        }
    }
}