/*
 * Copyright (C) 2020 by Savoir-faire Linux
 * Authors: William Enright <william.enright@savoirfairelinux.com>
 *          Ndeye Anna Ndiaye <anna.ndiaye@savoirfairelinux.com>
 *          Johnny Flores <johnny.flores@savoirfairelinux.com>
 *          Mohammed Raza <mohammed.raza@savoirfairelinux.com>
 *          Felix Sidokhine <felix.sidokhine@savoirfairelinux.com>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package net.jami.jams.authmodule;

import com.nimbusds.jwt.SignedJWT;

import lombok.extern.slf4j.Slf4j;

import net.jami.datastore.main.DataStore;
import net.jami.jams.common.authentication.AuthenticationSource;
import net.jami.jams.common.authentication.AuthenticationSourceType;
import net.jami.jams.common.authmodule.AuthModuleKey;
import net.jami.jams.common.authmodule.AuthTokenResponse;
import net.jami.jams.common.authmodule.AuthenticationModule;
import net.jami.jams.common.cryptoengineapi.CertificateAuthority;
import net.jami.jams.common.jami.NameServer;
import net.jami.jams.common.objects.user.AccessLevel;
import net.jami.jams.common.objects.user.User;
import net.jami.jams.common.utils.LibraryLoader;
import net.jami.jams.common.utils.X509Utils;

import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.cert.X509CRLHolder;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.cert.X509Certificate;
import java.security.interfaces.RSAPublicKey;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;

@Slf4j
public class UserAuthenticationModule implements AuthenticationModule {
    // This contains the DOMAIN-SOURCE.
    // In general there is at most 2 here.
    private static final String LDAP_CONNECTOR_CLASS = "net.jami.jams.ldap.connector.LDAPConnector";
    private static final String AD_CONNECTOR_CLASS = "net.jami.jams.ad.connector.ADConnector";
    public static DataStore datastore;
    public static CertificateAuthority certificateAuthority;
    private final TokenController tokenController;
    private PrivateKey privateKey = null;
    private PublicKey publicKey = null;
    // The data storage layer for tokens.

    private final ConcurrentHashMap<AuthModuleKey, AuthenticationSource> authenticationSources =
            new ConcurrentHashMap<>();

    public UserAuthenticationModule(DataStore dataStore, CertificateAuthority certificateAuthority)
            throws Exception {
        UserAuthenticationModule.datastore = dataStore;
        UserAuthenticationModule.certificateAuthority = certificateAuthority;
        authenticationSources.put(
                new AuthModuleKey("LOCAL", AuthenticationSourceType.LOCAL), datastore);
        log.info("Started authentication module - default local source is already enabled!");

        File pubkeyFile = new File(System.getProperty("user.dir") + File.separator + "oauth.pub");
        File privateKeyFile =
                new File(System.getProperty("user.dir") + File.separator + "oauth.key");

        if (!privateKeyFile.exists() || !pubkeyFile.exists()) {
            log.info("Generating first time private/public keys for OAuth!");
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            keyPairGenerator.initialize(4096);
            KeyPair kp = keyPairGenerator.generateKeyPair();
            privateKey = kp.getPrivate();
            publicKey = kp.getPublic();
            // Store these to file.
            OutputStream os;
            os =
                    new FileOutputStream(
                            System.getProperty("user.dir") + File.separator + "oauth.key");
            os.write(X509Utils.getPEMStringFromPrivateKey(privateKey).getBytes());
            os.flush();
            os.close();
            log.info("Succesfully stored OAuth private key for future use...");
            os =
                    new FileOutputStream(
                            System.getProperty("user.dir") + File.separator + "oauth.pub");
            os.write(X509Utils.getPEMStringFromPubKey(publicKey).getBytes());
            os.flush();
            os.close();
            log.info("Succesfully stored OAuth public key for future use...");
        } else {
            InputStream privateInput = new FileInputStream(privateKeyFile);
            privateKey = X509Utils.getKeyFromPEMString(new String(privateInput.readAllBytes()));
            privateInput.close();
            log.info("Succesfully loaded OAuth private key!");

            InputStream publicInput = new FileInputStream(pubkeyFile);
            publicKey = X509Utils.getPubKeyFromPEMString(new String(publicInput.readAllBytes()));
            publicInput.close();
            log.info("Succesfully loaded OAuth public key!");
        }
        // TODO: Read signing key, if file does not exist create it (also create the corresponding
        // public key)
        tokenController = new TokenController(privateKey);
        // Also expose the public key programatically.
        log.info("OAuth2 Token System instantiated succesfully!");
    }

    @Override
    public void attachAuthSource(AuthenticationSourceType type, String settings) {
        switch (type) {
            case AD:
                loadAuthConnector(AD_CONNECTOR_CLASS, settings);
                break;
            case LDAP:
                loadAuthConnector(LDAP_CONNECTOR_CLASS, settings);
                break;
            default:
                break;
        }
    }

    private void loadAuthConnector(String className, String settings) {
        try {
            Class<?> cls = LibraryLoader.classLoader.loadClass(className);
            AuthenticationSource source =
                    (AuthenticationSource) cls.getConstructor(String.class).newInstance(settings);
            authenticationSources.put(
                    new AuthModuleKey(
                            source.getInfo().getRealm(),
                            source.getInfo().getAuthenticationSourceType()),
                    source);
        } catch (Exception e) {
            log.error("Could not load connector " + className + " with reason: " + e);
        }
    }

    @Override
    public AuthTokenResponse authenticateUser(String username, String password) {
        AuthTokenResponse res = null;
        String hashPass = "";
        if (datastore.getUserDao().getByUsername(username).isPresent()) {
            User user = datastore.getUserDao().getByUsername(username).orElseThrow();
            if ((user.getUserType() == AuthenticationSourceType.LOCAL))
                hashPass = PasswordUtil.hashPassword(password, Base64.decodeBase64(user.getSalt()));
            else hashPass = password;

            if (hashPass != null
                    && authenticationSources
                            .get(new AuthModuleKey(user.getRealm(), user.getUserType()))
                            .authenticate(username, hashPass))
                return tokenController.getToken(user, null);
        }
        // The second case is much more violent, because we don't know in
        // advance "where" this user comes from, so we have to infer
        // (this is only really true for "users", all others are usually pre-marked)
        // This is also the case when we store the user into the DAO
        // - because he never existed before.
        for (AuthModuleKey key : authenticationSources.keySet()) {
            if (authenticationSources.get(key).authenticate(username, password)) {
                User user = new User();
                user.setUsername(username);
                user.setAccessLevel(AccessLevel.USER);
                user.setRealm(key.getRealm());
                user.setUserType(key.getType());
                // This is legal with a null ONLY because in this case there is no relation with a
                // external server.
                RegisterUserFlow.createUser(user, null);
                return tokenController.getToken(user, null);
            }
        }
        return res;
    }

    @Override
    public AuthTokenResponse authenticateUser(
            X509Certificate[] certificates, X509CRLHolder crl, X509Certificate ca) {
        // Extract the username for the certificate and verify that it is not revoked.
        X509Certificate clientCert = certificates[1];
        X509Certificate deviceCert = certificates[0];
        try {
            // Check if the certificate is even valid.
            clientCert.checkValidity();
            // Check if the certificate was provided by a valid authority.
            clientCert.verify(ca.getPublicKey());
            // Here we need to make a request to the CRL to find out if it has been revoked.
            if (crl.getRevokedCertificate(clientCert.getSerialNumber()) != null) return null;
            String username = X509Utils.extractDNFromCertificate(clientCert).get("CN");
            // We need to extract the deviceId from the certificate
            User user = datastore.getUserDao().getByUsername(username).orElseThrow();
            return tokenController.getToken(
                    user, X509Utils.extractDNFromCertificate(deviceCert).get("UID"));
        } catch (Exception e) {
            return null;
        }
    }

    @Override
    public ConcurrentHashMap<AuthModuleKey, AuthenticationSource> getAuthSources() {
        return authenticationSources;
    }

    @Override
    public boolean testModuleConfiguration(AuthenticationSourceType type, String settings) {
        try {
            String className = "";
            if (type.equals(AuthenticationSourceType.AD)) className = AD_CONNECTOR_CLASS;
            if (type.equals(AuthenticationSourceType.LDAP)) className = LDAP_CONNECTOR_CLASS;
            Class<?> cls = LibraryLoader.classLoader.loadClass(className);
            AuthenticationSource source =
                    (AuthenticationSource) cls.getConstructor(String.class).newInstance(settings);
            return source.test();
        } catch (Exception e) {
            log.error("The testing of the source was unsuccessful: " + e);
            return false;
        }
    }

    @Override
    public boolean createUser(
            AuthenticationSourceType type, String realm, NameServer nameServer, User user) {
        // This concept doesn't exist for LDAP or AD or any other hosted directory, in this case we
        // simply run
        // very theoretically, we should allow LDAP to publish to the public registry, but this is a
        // lot
        // more complex.
        return RegisterUserFlow.createUser(user, nameServer);
    }

    @Override
    public RSAPublicKey getAuthModulePubKey() {
        return (RSAPublicKey) publicKey;
    }

    @Override
    public char[] getOTP(String username) {
        Optional<User> user = datastore.getUserDao().getByUsername(username);
        return user.map(u -> u.getPassword().toCharArray()).orElse(new char[0]);
    }

    @Override
    public boolean verifyToken(SignedJWT token) {
        return false;
    }

    @Override
    public void deleteToken(SignedJWT token) {}
}