/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.calcite.avatica.server;

import org.apache.calcite.avatica.AvaticaUtils;
import org.apache.calcite.avatica.metrics.MetricsSystem;
import org.apache.calcite.avatica.metrics.Timer;
import org.apache.calcite.avatica.metrics.Timer.Context;
import org.apache.calcite.avatica.metrics.noop.NoopMetricsSystem;
import org.apache.calcite.avatica.remote.Handler.HandlerResponse;
import org.apache.calcite.avatica.remote.MetricsHelper;
import org.apache.calcite.avatica.remote.ProtobufHandler;
import org.apache.calcite.avatica.remote.ProtobufTranslation;
import org.apache.calcite.avatica.remote.ProtobufTranslationImpl;
import org.apache.calcite.avatica.remote.Service;
import org.apache.calcite.avatica.remote.Service.RpcMetadataResponse;
import org.apache.calcite.avatica.util.UnsynchronizedBuffer;

import org.eclipse.jetty.server.Request;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Objects;
import java.util.concurrent.Callable;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Jetty handler that executes Avatica JSON request-responses.
 */
public class AvaticaProtobufHandler extends AbstractAvaticaHandler {
  private static final Logger LOG = LoggerFactory.getLogger(AvaticaProtobufHandler.class);

  private final Service service;
  private final ProtobufHandler pbHandler;
  private final ProtobufTranslation protobufTranslation;
  private final MetricsSystem metrics;
  private final Timer requestTimer;
  private final AvaticaServerConfiguration serverConfig;

  final ThreadLocal<UnsynchronizedBuffer> threadLocalBuffer;

  public AvaticaProtobufHandler(Service service) {
    this(service, NoopMetricsSystem.getInstance());
  }

  public AvaticaProtobufHandler(Service service, MetricsSystem metrics) {
    this(service, metrics, null);
  }

  public AvaticaProtobufHandler(Service service, MetricsSystem metrics,
      AvaticaServerConfiguration serverConfig) {
    this.service = Objects.requireNonNull(service);
    this.metrics = Objects.requireNonNull(metrics);

    this.requestTimer = this.metrics.getTimer(
        MetricsHelper.concat(AvaticaProtobufHandler.class,
            MetricsAwareAvaticaHandler.REQUEST_TIMER_NAME));

    this.protobufTranslation = new ProtobufTranslationImpl();
    this.pbHandler = new ProtobufHandler(service, protobufTranslation, metrics);

    this.threadLocalBuffer = new ThreadLocal<UnsynchronizedBuffer>() {
      @Override public UnsynchronizedBuffer initialValue() {
        return new UnsynchronizedBuffer();
      }
    };

    this.serverConfig = serverConfig;
  }

  public void handle(String target, Request baseRequest,
      HttpServletRequest request, HttpServletResponse response)
      throws IOException, ServletException {
    try (final Context ctx = this.requestTimer.start()) {
      if (!request.getMethod().equals("POST")) {
        response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
        response.getOutputStream().write(
            "This server expects only POST calls.".getBytes(StandardCharsets.UTF_8));
        baseRequest.setHandled(true);
        return;
      }

      // Check if the user is OK to proceed.
      if (!isUserPermitted(serverConfig, baseRequest, request, response)) {
        LOG.debug("HTTP request from {} is unauthenticated and authentication is required",
            request.getRemoteAddr());
        return;
      }

      final byte[] requestBytes;
      // Avoid a new buffer creation for every HTTP request
      final UnsynchronizedBuffer buffer = threadLocalBuffer.get();
      try (ServletInputStream inputStream = request.getInputStream()) {
        requestBytes = AvaticaUtils.readFullyToBytes(inputStream, buffer);
      } finally {
        buffer.reset();
      }

      response.setContentType("application/octet-stream;charset=utf-8");
      response.setStatus(HttpServletResponse.SC_OK);
      HandlerResponse<byte[]> handlerResponse;
      try {
        if (null != serverConfig && serverConfig.supportsImpersonation()) {
          // If we can't extract a user, need to throw 401 in that case.
          String remoteUser = serverConfig.getRemoteUserExtractor().extract(request);
          // Invoke the ProtobufHandler inside as doAs for the remote user.
          // The doAsRemoteUser call may disallow a user, need to throw 403 in that case.
          handlerResponse = serverConfig.doAsRemoteUser(remoteUser,
            request.getRemoteAddr(), new Callable<HandlerResponse<byte[]>>() {
              @Override public HandlerResponse<byte[]> call() {
                return pbHandler.apply(requestBytes);
              }
            });
        } else {
          handlerResponse = pbHandler.apply(requestBytes);
        }
      } catch (RemoteUserExtractionException e) {
        LOG.debug("Failed to extract remote user from request", e);
        handlerResponse = pbHandler.unauthenticatedErrorResponse(e);
      } catch (RemoteUserDisallowedException e) {
        LOG.debug("Remote user is not authorized", e);
        handlerResponse = pbHandler.unauthorizedErrorResponse(e);
      } catch (Exception e) {
        LOG.debug("Error invoking request from {}", baseRequest.getRemoteAddr(), e);
        // Catch at the highest level of exceptions
        handlerResponse = pbHandler.convertToErrorResponse(e);
      }

      baseRequest.setHandled(true);
      response.setStatus(handlerResponse.getStatusCode());
      response.getOutputStream().write(handlerResponse.getResponse());
    }
  }

  @Override public void setServerRpcMetadata(RpcMetadataResponse metadata) {
    // Set the metadata for the normal service calls
    service.setRpcMetadata(metadata);
    // Also add it to the handler to include with exceptions
    pbHandler.setRpcMetadata(metadata);
  }

  @Override public MetricsSystem getMetrics() {
    return this.metrics;
  }

}

// End AvaticaProtobufHandler.java