using System.Net;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using SPTarkov.DI.Annotations;
using SPTarkov.Server.Core.Models.Utils;
using SPTarkov.Server.Core.Utils;

namespace SPTarkov.Server.Core.Helpers;

[Injectable]
public class CertificateHelper(ISptLogger<CertificateHelper> logger, FileUtil fileUtil)
{
    private const string CertificatePath = "./user/certs/server.crt";
    private const string CertificateKeyPath = "./user/certs/server.key";
    private const string CertificatePfxPath = "./user/certs/certificate.pfx";

    //Todo: Finish off to match TS server
    /// <summary>
    ///     Not currently in use
    /// </summary>
    /// <returns></returns>
    /// <exception cref="Exception"></exception>
    public X509Certificate2 LoadOrGenerateCertificate()
    {
        if (!Directory.Exists("./user/certs"))
        {
            Directory.CreateDirectory("./user/certs");
        }

        var certificate = LoadCertificate();

        if (certificate == null)
        {
            // Generate self-signed certificate
            certificate = GenerateSelfSignedCertificate("localhost");
            SaveCertificate(certificate); // Save cert and new key
            certificate = LoadCertificate();
            if (certificate == null)
            {
                // if we are still null here there is a serious problem creating cert
                throw new Exception("Certificate could not be loaded for the second time.");
            }

            logger.Success($"Generated and stored self-signed certificate ({CertificatePath})");
        }

        return certificate;
    }

    //Todo: When the above is finished off, remove any method with Pfx in the name
    public X509Certificate2? LoadOrGenerateCertificatePfx()
    {
        if (!Directory.Exists("./user/certs"))
        {
            Directory.CreateDirectory("./user/certs");
        }

        if (TryLoadCertificatePfx(out var cert))
        {
            logger.Success($"Loaded self-signed certificate ({CertificatePath})");
            return cert;
        }

        // shit went wrong, throw a wobbly and close app
        logger.Critical("Certificate pfx could not be loaded. Stopping server...");
        Environment.Exit(1);
        return null;
    }

    private X509Certificate2? LoadCertificate()
    {
        try
        {
            return X509Certificate2.CreateFromPemFile(CertificatePath, CertificateKeyPath);
        }
        catch (Exception)
        {
            return null;
        }
    }

    /// <summary>
    ///     if the cert exist, try load it, else create one and try load again
    /// </summary>
    /// <returns></returns>
    private bool TryLoadCertificatePfx(out X509Certificate2? certificate)
    {
        if (!File.Exists(CertificatePfxPath))
        {
            // file doesn't exist so create straight away
            var cert = GenerateSelfSignedCertificate("localhost");
            SaveCertificatePfx(cert);
            logger.Success($"Generated and stored self-signed certificate ({CertificatePath})");
        }

        try
        {
            // TODO:
            //Archangel: For some reason despite this being deprecated this is the only way to load a certificate file
            //No idea why, I want to eventually switch over to the other format so it lines up with the TS server
            //But for now this works fine
            certificate = new X509Certificate2(CertificatePfxPath);
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
            throw;
        }

        // Just return true, we're throwing an exception if creating the cert fails
        return true;
    }

    /// <summary>
    ///     Get a certificate from provided path and return
    /// </summary>
    /// <returns>X509Certificate2</returns>
    private X509Certificate2? LoadCertificatePfx()
    {
        try
        {
            //Archangel: For some reason despite this being deprecated this is the only way to load a certificate file
            //No idea why, I want to eventually switch over to the other format so it lines up with the TS server
            //But for now this works fine
            return new X509Certificate2(CertificatePfxPath);
        }
        catch (Exception)
        {
            return null;
        }
    }

    /// <summary>
    ///     Generate and return a self-signed certificate
    /// </summary>
    /// <param name="subjectName">e.g. localhost</param>
    /// <returns>X509Certificate2</returns>
    private X509Certificate2 GenerateSelfSignedCertificate(string subjectName)
    {
        var sanBuilder = new SubjectAlternativeNameBuilder();
        sanBuilder.AddIpAddress(IPAddress.Loopback);
        sanBuilder.AddDnsName("localhost");
        sanBuilder.AddDnsName(Environment.MachineName);

        var distinguishedName = new X500DistinguishedName($"CN={subjectName}");

        using var rsa = RSA.Create(2048);
        var request = new CertificateRequest(distinguishedName, rsa, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
        request.CertificateExtensions.Add(sanBuilder.Build());

        //Todo: Enable when Pfx methods can be removed
        //SavePrivateKey(rsa);

        return request.CreateSelfSigned(new DateTimeOffset(DateTime.UtcNow.AddDays(-1)), new DateTimeOffset(DateTime.UtcNow.AddDays(3650)));
    }

    /// <summary>
    ///     Save a certificate as a file to disk
    /// </summary>
    /// <param name="certificate">Certificate to save</param>
    private void SaveCertificate(X509Certificate2 certificate)
    {
        try
        {
            // Save as PEM (ensure the certificate is in PEM format)
            var certPem =
                "-----BEGIN CERTIFICATE-----\n"
                + Convert.ToBase64String(certificate.Export(X509ContentType.Cert), Base64FormattingOptions.InsertLineBreaks)
                + "\n-----END CERTIFICATE-----";
            fileUtil.WriteFile(CertificatePath, certPem);
        }
        catch (Exception ex)
        {
            logger.Error($"Error saving certificate: {ex.Message}");
        }
    }

    /// <summary>
    ///     Save a certificate as a file to disk
    /// </summary>
    /// <param name="certificate">Certificate to save</param>
    private void SaveCertificatePfx(X509Certificate2 certificate)
    {
        try
        {
            fileUtil.WriteFile(CertificatePfxPath, certificate.Export(X509ContentType.Pfx));
        }
        catch (Exception ex)
        {
            logger.Error($"Error saving certificate: {ex.Message}");
        }
    }

    private void SavePrivateKey(RSA privateKey)
    {
        try
        {
            var privateKeyBytes = privateKey.ExportPkcs8PrivateKey();

            // Convert the private key to PEM format (Base64 encoded)
            var privateKeyString =
                "-----BEGIN PRIVATE KEY-----\n"
                + Convert.ToBase64String(privateKeyBytes, Base64FormattingOptions.InsertLineBreaks)
                + "\n-----END PRIVATE KEY-----";

            fileUtil.WriteFile(CertificateKeyPath, privateKeyString);
        }
        catch (Exception ex)
        {
            logger.Error($"Error saving certificate key: {ex.Message}");
        }
    }
}