package co.codewizards.cloudstore.ls.rest.client;

import static co.codewizards.cloudstore.core.util.Util.*;
import static java.util.Objects.*;

import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import javax.ws.rs.WebApplicationException;
import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Invocation;
import javax.ws.rs.client.ResponseProcessingException;
import javax.ws.rs.core.Response;

import org.glassfish.jersey.client.ClientConfig;
import org.glassfish.jersey.client.ClientProperties;
import org.glassfish.jersey.client.authentication.HttpAuthenticationFeature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import co.codewizards.cloudstore.core.Uid;
import co.codewizards.cloudstore.core.concurrent.DeferredCompletionException;
import co.codewizards.cloudstore.core.config.Config;
import co.codewizards.cloudstore.core.config.ConfigImpl;
import co.codewizards.cloudstore.core.dto.Error;
import co.codewizards.cloudstore.core.dto.RemoteException;
import co.codewizards.cloudstore.core.dto.RemoteExceptionUtil;
import co.codewizards.cloudstore.ls.core.LocalServerPropertiesManager;
import co.codewizards.cloudstore.ls.core.provider.JavaNativeMessageBodyReader;
import co.codewizards.cloudstore.ls.core.provider.JavaNativeMessageBodyWriter;
import co.codewizards.cloudstore.ls.rest.client.request.Request;

/**
 * Client for executing REST requests.
 * <p>
 * An instance of this class is used to send data to, query data from or execute logic on the server.
 * <p>
 * If a series of multiple requests is to be sent to the server, it is recommended to keep an instance of
 * this class (because it caches resources) and invoke multiple requests with it.
 * <p>
 * This class is thread-safe.
 * @author Marco หงุ่ยตระกูล-Schulze - marco at codewizards dot co
 */
public class LocalServerRestClient {

        private static final Logger logger = LoggerFactory.getLogger(LocalServerRestClient.class);

        private static final int DEFAULT_SOCKET_CONNECT_TIMEOUT = 30 * 1000; // 30 seconds should really be sufficient to connect to localhost
        private static final int DEFAULT_SOCKET_READ_TIMEOUT = 3 * 60 * 1000; // 3 minutes is more than enough, because we have DelayedMethodInvocationResponse

        /**
         * The {@code key} for the connection timeout used with {@link Config#getPropertyAsInt(String, int)}.
         * <p>
         * The configuration can be overridden by a system property - see {@link Config#SYSTEM_PROPERTY_PREFIX}.
         */
        public static final String CONFIG_KEY_SOCKET_CONNECT_TIMEOUT = "localServer.socket.connectTimeout"; //$NON-NLS-1$

        /**
         * The {@code key} for the read timeout used with {@link Config#getPropertyAsInt(String, int)}.
         * <p>
         * The configuration can be overridden by a system property - see {@link Config#SYSTEM_PROPERTY_PREFIX}.
         */
        public static final String CONFIG_KEY_SOCKET_READ_TIMEOUT = "localServer.socket.readTimeout"; //$NON-NLS-1$

        private Integer socketConnectTimeout;

        private Integer socketReadTimeout;

        private String baseUrl;

        private final LinkedList<Client> clientCache = new LinkedList<Client>();

        private CredentialsProvider credentialsProvider;

        private static final class Holder {
                public static final LocalServerRestClient instance = new LocalServerRestClient();
        }

        public static LocalServerRestClient getInstance() {
                return Holder.instance;
        }

        public synchronized Integer getSocketConnectTimeout() {
                if (socketConnectTimeout == null)
                        socketConnectTimeout = ConfigImpl.getInstance().getPropertyAsPositiveOrZeroInt(
                                        CONFIG_KEY_SOCKET_CONNECT_TIMEOUT,
                                        DEFAULT_SOCKET_CONNECT_TIMEOUT);

                return socketConnectTimeout;
        }
        public synchronized void setSocketConnectTimeout(Integer socketConnectTimeout) {
                if (socketConnectTimeout != null && socketConnectTimeout < 0)
                        socketConnectTimeout = null;

                this.socketConnectTimeout = socketConnectTimeout;
        }

        public synchronized Integer getSocketReadTimeout() {
                if (socketReadTimeout == null)
                        socketReadTimeout = ConfigImpl.getInstance().getPropertyAsPositiveOrZeroInt(
                                        CONFIG_KEY_SOCKET_READ_TIMEOUT,
                                        DEFAULT_SOCKET_READ_TIMEOUT);

                return socketReadTimeout;
        }
        public synchronized void setSocketReadTimeout(Integer socketReadTimeout) {
                if (socketReadTimeout != null && socketReadTimeout < 0)
                        socketReadTimeout = null;

                this.socketReadTimeout = socketReadTimeout;
        }

        /**
         * Get the server's base-URL.
         * <p>
         * This base-URL is the base of the <code>LocalServerRest</code> application. Hence all URLs
         * beneath this base-URL are processed by the <code>LocalServerRest</code> application.
         * @return the base-URL. This URL always ends with "/".
         */
        public synchronized String getBaseUrl() {
                if (baseUrl == null)
                        baseUrl = LocalServerPropertiesManager.getInstance().getBaseUrl();

                return baseUrl;
        }

        /**
         * Create a new client.
         */
        protected LocalServerRestClient() {
                // The clientId is used for memory management in the server: if a client is closed or disappears, i.e. doesn't
                // send keep-alives regularly, anymore, the server removes all objectRef-references kept for this client in its ObjectManager.
                final String clientId = new Uid().toString();

                setCredentialsProvider(new CredentialsProvider() {
                        @Override
                        public String getUserName() {
                                return clientId;
                        }
                        @Override
                        public String getPassword() {
                                return LocalServerPropertiesManager.getInstance().getPassword();
                        }
                });
        }

//      private static String appendFinalSlashIfNeeded(final String url) {
//              return url.endsWith("/") ? url : url + "/";
//      }

        public <R> R execute(final Request<R> request) {
                requireNonNull(request, "request");
                RuntimeException firstException = null;
                int retryCounter = 0; // *re*-try: first (normal) invocation is 0, first re-try is 1
                final int retryMax = 1; // *re*-try: 1 retries means 2 invocations in total
                while (true) {
                        acquireClient();
                        try {
                                final long start = System.currentTimeMillis();

                                if (logger.isDebugEnabled())
                                        logger.debug("execute: starting try {} of {}", retryCounter + 1, retryMax + 1);

                                try {
                                        request.setLocalServerRestClient(this);
                                        final R result = request.execute();

                                        if (logger.isDebugEnabled())
                                                logger.debug("execute: invocation took {} ms", System.currentTimeMillis() - start);

                                        if (result == null && !request.isResultNullable())
                                                throw new IllegalStateException("result == null, but request.resultNullable == false!");

                                        return result;
                                } catch (final RuntimeException x) {
                                        if (firstException == null)
                                                firstException = x;

                                        final String oldBaseUrl = getBaseUrl();
                                        baseUrl = null;
                                        if (!oldBaseUrl.equals(getBaseUrl())) {
                                                retryCounter = 0; // reset to make sure we really try again with the new URL
                                                clearClientCache();
                                        }

                                        markClientBroken(); // make sure we do not reuse this client
                                        if (++retryCounter > retryMax || !retryExecuteAfterException(x)) {
                                                logger.warn("execute: invocation failed (will NOT retry): " + x, x);
                                                handleAndRethrowException(firstException); // TODO maybe we should make a MultiCauseException?!
                                                throw firstException;
                                        }
                                        logger.warn("execute: invocation failed (will retry): " + x, x);

                                        // Wait a bit before retrying (increasingly longer).
                                        try { Thread.sleep(retryCounter * 1000L); } catch (Exception y) { doNothing(); }
                                }
                        } finally {
                                releaseClient();
                                request.setLocalServerRestClient(null);
                        }
                }
        }

        private synchronized void clearClientCache() {
                clientCache.clear();
        }

        private boolean retryExecuteAfterException(final Exception x) {
//              final Class<?>[] exceptionClassesCausingRetry = new Class<?>[] {
//                              SSLException.class,
//                              SocketException.class
//              };
//              for (final Class<?> exceptionClass : exceptionClassesCausingRetry) {
//                      @SuppressWarnings("unchecked")
//                      final Class<? extends Throwable> xc = (Class<? extends Throwable>) exceptionClass;
//                      if (ExceptionUtil.getCause(x, xc) != null) {
//                              logger.warn(
//                                              String.format("retryExecuteAfterException: Encountered %s and will retry.", xc.getSimpleName()),
//                                              x);
//                              return true;
//                      }
//              }
//              return false;
                return true;
        }

        public Invocation.Builder assignCredentials(final Invocation.Builder builder) {
                final CredentialsProvider credentialsProvider = getCredentialsProviderOrFail();
                builder.property(HttpAuthenticationFeature.HTTP_AUTHENTICATION_BASIC_USERNAME, credentialsProvider.getUserName());
                builder.property(HttpAuthenticationFeature.HTTP_AUTHENTICATION_BASIC_PASSWORD, credentialsProvider.getPassword());
                return builder;
        }

        private final ThreadLocal<ClientRef> clientThreadLocal = new ThreadLocal<ClientRef>();

        private static class ClientRef {
                public final Client client;
                public int refCount = 1;
                public boolean broken;

                public ClientRef(final Client client) {
                        this.client = requireNonNull(client, "client");
                }
        }

        /**
         * Acquire a {@link Client} and bind it to the current thread.
         * <p>
         * <b>Important: You must {@linkplain #releaseClient() release} the client!</b> Use a try/finally block!
         * @see #releaseClient()
         * @see #getClientOrFail()
         */
        private synchronized void acquireClient()
        {
                final ClientRef clientRef = clientThreadLocal.get();
                if (clientRef != null) {
                        ++clientRef.refCount;
                        return;
                }

                Client client = clientCache.poll();
                if (client == null) {
                        final ClientConfig clientConfig = new ClientConfig(CloudStoreJaxbContextResolver.class);
                        clientConfig.property(ClientProperties.CONNECT_TIMEOUT, getSocketConnectTimeout()); // must be a java.lang.Integer
                        clientConfig.property(ClientProperties.READ_TIMEOUT, getSocketReadTimeout()); // must be a java.lang.Integer

                        final ClientBuilder clientBuilder = ClientBuilder.newBuilder().withConfig(clientConfig);

                        clientBuilder.register(JavaNativeMessageBodyReader.class);
                        clientBuilder.register(JavaNativeMessageBodyWriter.class);

                        for (final Object restComponent : restComponents) {
                                if (restComponent instanceof Class<?>)
                                        clientBuilder.register((Class<?>) restComponent);
                                else
                                        clientBuilder.register(restComponent);
                        }

                        client = clientBuilder.build();

                        // An authentication is always required. Otherwise Jersey throws an exception.
                        // Hence, we set it to "anonymous" here and set it to the real values for those
                        // requests really requiring it.
                        final HttpAuthenticationFeature feature = HttpAuthenticationFeature.basic("anonymous", "");
                        client.register(feature);

//                      configFrozen = true;
                }
                clientThreadLocal.set(new ClientRef(client));
        }

        private final List<Object> restComponents = new CopyOnWriteArrayList<Object>();

        public void registerRestComponent(Object restComponent) {
                restComponents.add(restComponent);
        }

        /**
         * Get the {@link Client} which was previously {@linkplain #acquireClient() acquired} (and not yet
         * {@linkplain #releaseClient() released}) on the same thread.
         * @return the {@link Client}. Never <code>null</code>.
         * @throws IllegalStateException if there is no {@link Client} bound to the current thread.
         * @see #acquireClient()
         */
        public Client getClientOrFail() {
                final ClientRef clientRef = clientThreadLocal.get();
                if (clientRef == null)
                        throw new IllegalStateException("acquireClient() not called on the same thread (or releaseClient() already called)!");

                return clientRef.client;
        }

        /**
         * Release a {@link Client} which was previously {@linkplain #acquireClient() acquired}.
         * @see #acquireClient()
         */
        private synchronized void releaseClient() {
                final ClientRef clientRef = clientThreadLocal.get();
                if (clientRef == null)
                        throw new IllegalStateException("acquireClient() not called on the same thread (or releaseClient() called more often than acquireClient())!");

                if (--clientRef.refCount == 0) {
                        clientThreadLocal.remove();

                        if (!clientRef.broken)
                                clientCache.add(clientRef.client);
                }
        }

        private void markClientBroken() {
                final ClientRef clientRef = clientThreadLocal.get();
                if (clientRef == null)
                        throw new IllegalStateException("acquireClient() not called on the same thread (or releaseClient() called more often than acquireClient())!");

                clientRef.broken = true;
        }

        public void handleAndRethrowException(final RuntimeException x)
        {
                Response response = null;
                if (x instanceof WebApplicationException)
                        response = ((WebApplicationException)x).getResponse();
                else if (x instanceof ResponseProcessingException)
                        response = ((ResponseProcessingException)x).getResponse();

                if (response == null)
                        throw x;

                Error error = null;
                try {
                        response.bufferEntity();
                        if (response.hasEntity())
                                error = response.readEntity(Error.class);

                        if (error != null && DeferredCompletionException.class.getName().equals(error.getClassName()))
                                logger.debug("handleException: " + x, x);
                        else
                                logger.error("handleException: " + x, x);

                } catch (final Exception y) {
                        logger.error("handleException: " + x, x);
                        logger.error("handleException: " + y, y);
                }

                if (error != null) {
                        RemoteExceptionUtil.throwOriginalExceptionIfPossible(error);
                        throw new RemoteException(error);
                }

                throw x;
        }

        public CredentialsProvider getCredentialsProvider() {
                return credentialsProvider;
        }
        private CredentialsProvider getCredentialsProviderOrFail() {
                final CredentialsProvider credentialsProvider = getCredentialsProvider();
                if (credentialsProvider == null)
                        throw new IllegalStateException("credentialsProvider == null");
                return credentialsProvider;
        }
        public void setCredentialsProvider(final CredentialsProvider credentialsProvider) {
                this.credentialsProvider = credentialsProvider;
        }
}