using Renci.SshNet;
using OTSSignsOrchestrator.Server.Data.Entities;

namespace OTSSignsOrchestrator.Server.Health.Checks;

/// <summary>
/// Verifies NFS paths for the instance are accessible by running <c>ls</c> via SSH.
/// </summary>
public sealed class NfsAccessHealthCheck : IHealthCheck
{
    private readonly IServiceProvider _services;
    private readonly ILogger<NfsAccessHealthCheck> _logger;

    public string CheckName => "NfsAccess";
    public bool AutoRemediate => false;

    public NfsAccessHealthCheck(
        IServiceProvider services,
        ILogger<NfsAccessHealthCheck> logger)
    {
        _services = services;
        _logger = logger;
    }

    public async Task<HealthCheckResult> RunAsync(Instance instance, CancellationToken ct)
    {
        var nfsPath = instance.NfsPath;
        if (string.IsNullOrEmpty(nfsPath))
            return new HealthCheckResult(HealthStatus.Critical, "No NFS path configured");

        try
        {
            var settings = _services.GetRequiredService<Core.Services.SettingsService>();
            var sshInfo = await GetSwarmSshHostAsync(settings);
            var nfsServer = await settings.GetAsync(Core.Services.SettingsService.NfsServer);
            var nfsExport = await settings.GetAsync(Core.Services.SettingsService.NfsExport);

            if (string.IsNullOrEmpty(nfsServer) || string.IsNullOrEmpty(nfsExport))
                return new HealthCheckResult(HealthStatus.Critical, "NFS server/export not configured");

            using var sshClient = CreateSshClient(sshInfo);
            sshClient.Connect();
            try
            {
                // Mount temporarily and check the path is listable
                var mountPoint = $"/tmp/healthcheck-nfs-{Guid.NewGuid():N}";
                RunSshCommand(sshClient, $"sudo mkdir -p {mountPoint}");
                try
                {
                    RunSshCommand(sshClient, $"sudo mount -t nfs4 {nfsServer}:{nfsExport} {mountPoint}");
                    var output = RunSshCommand(sshClient, $"ls {mountPoint}/{nfsPath} 2>&1");

                    return new HealthCheckResult(HealthStatus.Healthy,
                        $"NFS path accessible: {nfsPath}");
                }
                finally
                {
                    RunSshCommandAllowFailure(sshClient, $"sudo umount {mountPoint}");
                    RunSshCommandAllowFailure(sshClient, $"sudo rmdir {mountPoint}");
                }
            }
            finally
            {
                sshClient.Disconnect();
            }
        }
        catch (Exception ex)
        {
            return new HealthCheckResult(HealthStatus.Critical,
                $"NFS access check failed for {nfsPath}: {ex.Message}");
        }
    }

    private static async Task<SshConnectionInfo> GetSwarmSshHostAsync(Core.Services.SettingsService settings)
    {
        var host = await settings.GetAsync("Ssh.SwarmHost")
            ?? throw new InvalidOperationException("SSH Swarm host not configured.");
        var portStr = await settings.GetAsync("Ssh.SwarmPort", "22");
        var user = await settings.GetAsync("Ssh.SwarmUser", "root");
        var keyPath = await settings.GetAsync("Ssh.SwarmKeyPath");
        var password = await settings.GetAsync("Ssh.SwarmPassword");
        if (!int.TryParse(portStr, out var port)) port = 22;
        return new SshConnectionInfo(host, port, user, keyPath, password);
    }

    private static SshClient CreateSshClient(SshConnectionInfo info)
    {
        var authMethods = new List<AuthenticationMethod>();
        if (!string.IsNullOrEmpty(info.KeyPath))
            authMethods.Add(new PrivateKeyAuthenticationMethod(info.Username, new PrivateKeyFile(info.KeyPath)));
        if (!string.IsNullOrEmpty(info.Password))
            authMethods.Add(new PasswordAuthenticationMethod(info.Username, info.Password));
        if (authMethods.Count == 0)
        {
            var defaultKeyPath = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".ssh", "id_rsa");
            if (File.Exists(defaultKeyPath))
                authMethods.Add(new PrivateKeyAuthenticationMethod(info.Username, new PrivateKeyFile(defaultKeyPath)));
            else
                throw new InvalidOperationException($"No SSH auth method for {info.Host}:{info.Port}.");
        }
        var connInfo = new Renci.SshNet.ConnectionInfo(info.Host, info.Port, info.Username, authMethods.ToArray());
        return new SshClient(connInfo);
    }

    private static string RunSshCommand(SshClient client, string command)
    {
        using var cmd = client.RunCommand(command);
        if (cmd.ExitStatus != 0)
            throw new InvalidOperationException($"SSH command failed (exit {cmd.ExitStatus}): {cmd.Error}");
        return cmd.Result;
    }

    private static void RunSshCommandAllowFailure(SshClient client, string command)
    {
        using var cmd = client.RunCommand(command);
        // Intentionally ignore exit code — cleanup operations
    }

    internal sealed record SshConnectionInfo(string Host, int Port, string Username, string? KeyPath, string? Password);
}