/*
 * 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.flink.runtime.webmonitor;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http.router.KeepAliveWrite;
import io.netty.handler.codec.http.router.Routed;

import org.apache.flink.configuration.ConfigConstants;
import org.apache.flink.runtime.instance.ActorGateway;
import org.apache.flink.runtime.webmonitor.handlers.RequestHandler;
import org.apache.flink.util.ExceptionUtils;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import scala.concurrent.Future;
import scala.concurrent.duration.FiniteDuration;

import java.net.InetSocketAddress;
import java.net.URLDecoder;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * The Netty channel handler that processes all HTTP requests.
 * This handler takes the path parameters and delegates the work to a {@link RequestHandler}.
 * This handler also deals with setting correct response MIME types and returning
 * proper codes, like OK, NOT_FOUND, or SERVER_ERROR.
 */
@ChannelHandler.Sharable
public class RuntimeMonitorHandler extends RuntimeMonitorHandlerBase {

	private static final Logger LOG = LoggerFactory.getLogger(RuntimeMonitorHandler.class);

	private static final Charset ENCODING = ConfigConstants.DEFAULT_CHARSET;

	public static final String WEB_MONITOR_ADDRESS_KEY = "web.monitor.address";

	private final RequestHandler handler;

	private final String allowOrigin;

	public RuntimeMonitorHandler(
			WebMonitorConfig cfg,
			RequestHandler handler,
			JobManagerRetriever retriever,
			Future<String> localJobManagerAddressFuture,
			FiniteDuration timeout,
			boolean httpsEnabled) {

		super(retriever, localJobManagerAddressFuture, timeout, httpsEnabled);
		this.handler = checkNotNull(handler);
		this.allowOrigin = cfg.getAllowOrigin();
	}

	@Override
	public String[] getPaths() {
		return handler.getPaths();
	}

	@Override
	protected void respondAsLeader(ChannelHandlerContext ctx, Routed routed, ActorGateway jobManager) {
		FullHttpResponse response;

		try {
			// we only pass the first element in the list to the handlers.
			Map<String, String> queryParams = new HashMap<>();
			for (String key : routed.queryParams().keySet()) {
				queryParams.put(key, routed.queryParam(key));
			}

			Map<String, String> pathParams = new HashMap<>(routed.pathParams().size());
			for (String key : routed.pathParams().keySet()) {
				pathParams.put(key, URLDecoder.decode(routed.pathParams().get(key), ENCODING.toString()));
			}

			InetSocketAddress address = (InetSocketAddress) ctx.channel().localAddress();
			queryParams.put(WEB_MONITOR_ADDRESS_KEY,
				(httpsEnabled ? "https://" : "http://") + address.getHostName() + ":" + address.getPort());

			response = handler.handleRequest(pathParams, queryParams, jobManager);
		}
		catch (NotFoundException e) {
			// this should result in a 404 error code (not found)
			ByteBuf message = e.getMessage() == null ? Unpooled.buffer(0)
					: Unpooled.wrappedBuffer(e.getMessage().getBytes(ENCODING));
			response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.NOT_FOUND, message);
			response.headers().set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
			response.headers().set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
			LOG.debug("Error while handling request", e);
		}
		catch (Exception e) {
			byte[] bytes = ExceptionUtils.stringifyException(e).getBytes(ENCODING);
			response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1,
					HttpResponseStatus.INTERNAL_SERVER_ERROR, Unpooled.wrappedBuffer(bytes));
			response.headers().set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
			response.headers().set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());

			LOG.debug("Error while handling request", e);
		}

		response.headers().set(HttpHeaders.Names.ACCESS_CONTROL_ALLOW_ORIGIN, allowOrigin);
		// Content-Encoding:utf-8
		response.headers().set(HttpHeaders.Names.CONTENT_ENCODING, ENCODING.name());

		KeepAliveWrite.flush(ctx, routed.request(), response);
	}
}