using System.Runtime.InteropServices;
using System.Security.Cryptography.X509Certificates;
using Microsoft.Extensions.Configuration;
using StellaOps.Doctor.Models;
using StellaOps.Doctor.Plugins;

namespace StellaOps.Doctor.Plugins.Cryptography.Checks;

/// <summary>
/// Validates eIDAS (EU qualified signatures) provider configuration.
/// </summary>
public sealed class EidasProviderCheck : IDoctorCheck
{
    /// <inheritdoc />
    public string CheckId => "check.crypto.eidas";

    /// <inheritdoc />
    public string Name => "eIDAS Provider";

    /// <inheritdoc />
    public string Description => "Validates eIDAS qualified signature provider configuration";

    /// <inheritdoc />
    public DoctorSeverity DefaultSeverity => DoctorSeverity.Info;

    /// <inheritdoc />
    public IReadOnlyList<string> Tags => ["cryptography", "eidas", "qualified", "eu", "regional"];

    /// <inheritdoc />
    public TimeSpan EstimatedDuration => TimeSpan.FromMilliseconds(100);

    /// <inheritdoc />
    public bool CanRun(DoctorPluginContext context)
    {
        // Only run if eIDAS is configured or enabled
        var eidasEnabled = context.Configuration.GetValue<bool?>("Cryptography:Eidas:Enabled")
            ?? context.Configuration.GetValue<bool?>("Cryptography:EnableEidas");

        return eidasEnabled == true;
    }

    /// <inheritdoc />
    public Task<DoctorCheckResult> RunAsync(DoctorPluginContext context, CancellationToken ct)
    {
        var result = context.CreateResult(CheckId, "stellaops.doctor.cryptography", DoctorCategory.Cryptography.ToString());

        var eidasProvider = context.Configuration.GetValue<string>("Cryptography:Eidas:Provider")
            ?? "pkcs11";

        var trustListUrl = context.Configuration.GetValue<string>("Cryptography:Eidas:TrustListUrl")
            ?? "https://ec.europa.eu/tools/lotl/eu-lotl.xml";

        var issues = new List<string>();
        var providerInfo = new Dictionary<string, string>
        {
            ["ConfiguredProvider"] = eidasProvider,
            ["TrustListUrl"] = trustListUrl
        };

        switch (eidasProvider.ToLowerInvariant())
        {
            case "pkcs11":
                CheckPkcs11Eidas(issues, providerInfo, context.Configuration);
                break;

            case "certificate":
                CheckCertificateEidas(issues, providerInfo, context.Configuration);
                break;

            case "remote":
                CheckRemoteEidas(issues, providerInfo, context.Configuration);
                break;

            default:
                issues.Add($"Unknown eIDAS provider: {eidasProvider}");
                break;
        }

        if (issues.Count > 0)
        {
            return Task.FromResult(result
                .Warn($"{issues.Count} eIDAS provider issue(s)")
                .WithEvidence("eIDAS configuration", e =>
                {
                    foreach (var kvp in providerInfo)
                    {
                        e.Add(kvp.Key, kvp.Value);
                    }
                })
                .WithCauses(issues.ToArray())
                .WithRemediation(r => r
                    .AddManualStep(1, "Configure provider", "Configure PKCS#11 library or certificate store for eIDAS")
                    .AddManualStep(2, "Verify trust list", "Ensure EU Trust List is accessible"))
                .WithVerification("stella doctor --check check.crypto.eidas")
                .Build());
        }

        return Task.FromResult(result
            .Pass("eIDAS provider is configured")
            .WithEvidence("eIDAS configuration", e =>
            {
                foreach (var kvp in providerInfo)
                {
                    e.Add(kvp.Key, kvp.Value);
                }
            })
            .Build());
    }

    private static void CheckPkcs11Eidas(List<string> issues, Dictionary<string, string> providerInfo, IConfiguration config)
    {
        providerInfo["Provider"] = "PKCS#11 (Smart Card/HSM)";

        var pkcs11Library = config.GetValue<string>("Cryptography:Eidas:Pkcs11Library");
        if (string.IsNullOrWhiteSpace(pkcs11Library))
        {
            issues.Add("PKCS#11 library path not configured for eIDAS");
            providerInfo["Library"] = "(not set)";
        }
        else if (!File.Exists(pkcs11Library))
        {
            issues.Add($"PKCS#11 library not found: {pkcs11Library}");
            providerInfo["Library"] = pkcs11Library;
        }
        else
        {
            providerInfo["Library"] = pkcs11Library;
        }

        var slotId = config.GetValue<int?>("Cryptography:Eidas:SlotId");
        providerInfo["SlotId"] = slotId?.ToString() ?? "(auto-detect)";
    }

    private static void CheckCertificateEidas(List<string> issues, Dictionary<string, string> providerInfo, IConfiguration config)
    {
        providerInfo["Provider"] = "Certificate Store";

        var certThumbprint = config.GetValue<string>("Cryptography:Eidas:CertificateThumbprint");
        var certPath = config.GetValue<string>("Cryptography:Eidas:CertificatePath");

        if (!string.IsNullOrWhiteSpace(certThumbprint))
        {
            providerInfo["CertificateThumbprint"] = certThumbprint;

            // Try to find certificate in store
            try
            {
                using var store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
                store.Open(OpenFlags.ReadOnly);
                var certs = store.Certificates.Find(
                    X509FindType.FindByThumbprint,
                    certThumbprint,
                    validOnly: false);

                if (certs.Count == 0)
                {
                    issues.Add($"Certificate with thumbprint {certThumbprint[..8]}... not found in store");
                }
                else
                {
                    var cert = certs[0];
                    providerInfo["CertificateSubject"] = cert.Subject;
                    providerInfo["CertificateExpiry"] = cert.NotAfter.ToString("yyyy-MM-dd");
                }
            }
            catch (Exception ex)
            {
                issues.Add($"Cannot access certificate store: {ex.Message}");
            }
        }
        else if (!string.IsNullOrWhiteSpace(certPath))
        {
            providerInfo["CertificatePath"] = certPath;
            if (!File.Exists(certPath))
            {
                issues.Add($"Certificate file not found: {certPath}");
            }
        }
        else
        {
            issues.Add("No certificate thumbprint or path configured for eIDAS");
        }
    }

    private static void CheckRemoteEidas(List<string> issues, Dictionary<string, string> providerInfo, IConfiguration config)
    {
        providerInfo["Provider"] = "Remote Signing Service";

        var remoteEndpoint = config.GetValue<string>("Cryptography:Eidas:RemoteEndpoint");
        if (string.IsNullOrWhiteSpace(remoteEndpoint))
        {
            issues.Add("Remote eIDAS signing endpoint not configured");
            providerInfo["Endpoint"] = "(not set)";
        }
        else
        {
            providerInfo["Endpoint"] = remoteEndpoint;
        }
    }
}