/*
 * 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.rest.handler.job.checkpoints;

import org.apache.flink.api.common.JobID;
import org.apache.flink.runtime.checkpoint.AbstractCheckpointStats;
import org.apache.flink.runtime.checkpoint.CheckpointStatsSnapshot;
import org.apache.flink.runtime.rest.handler.HandlerRequest;
import org.apache.flink.runtime.rest.handler.RestHandlerException;
import org.apache.flink.runtime.rest.messages.EmptyRequestBody;
import org.apache.flink.runtime.rest.messages.JobIDPathParameter;
import org.apache.flink.runtime.rest.messages.MessageHeaders;
import org.apache.flink.runtime.rest.messages.ResponseBody;
import org.apache.flink.runtime.rest.messages.checkpoints.CheckpointIdPathParameter;
import org.apache.flink.runtime.rest.messages.checkpoints.CheckpointMessageParameters;
import org.apache.flink.runtime.webmonitor.RestfulGateway;
import org.apache.flink.runtime.webmonitor.retriever.GatewayRetriever;
import org.apache.flink.util.Preconditions;

import org.apache.flink.shaded.guava32.com.google.common.cache.Cache;
import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;

import java.time.Duration;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;

/**
 * Base class for checkpoint related REST handler.
 *
 * @param <R> type of the response
 */
public abstract class AbstractCheckpointHandler<
                R extends ResponseBody, M extends CheckpointMessageParameters>
        extends AbstractCheckpointStatsHandler<R, M> {

    private final CheckpointStatsCache checkpointStatsCache;

    protected AbstractCheckpointHandler(
            GatewayRetriever<? extends RestfulGateway> leaderRetriever,
            Duration timeout,
            Map<String, String> responseHeaders,
            MessageHeaders<EmptyRequestBody, R, M> messageHeaders,
            Executor executor,
            Cache<JobID, CompletableFuture<CheckpointStatsSnapshot>> checkpointStatsSnapshotCache,
            CheckpointStatsCache checkpointStatsCache) {
        super(
                leaderRetriever,
                timeout,
                responseHeaders,
                messageHeaders,
                checkpointStatsSnapshotCache,
                executor);

        this.checkpointStatsCache = Preconditions.checkNotNull(checkpointStatsCache);
    }

    @Override
    protected R handleCheckpointStatsRequest(
            HandlerRequest<EmptyRequestBody> request,
            CheckpointStatsSnapshot checkpointStatsSnapshot)
            throws RestHandlerException {
        JobID jobId = request.getPathParameter(JobIDPathParameter.class);
        final long checkpointId = request.getPathParameter(CheckpointIdPathParameter.class);

        if (checkpointStatsSnapshot != null) {
            AbstractCheckpointStats checkpointStats =
                    checkpointStatsSnapshot.getHistory().getCheckpointById(checkpointId);

            if (checkpointStats != null) {
                checkpointStatsCache.tryAdd(checkpointStats);
            } else {
                checkpointStats = checkpointStatsCache.tryGet(checkpointId);
            }

            if (checkpointStats != null) {
                return handleCheckpointRequest(request, checkpointStats);
            } else {
                throw new RestHandlerException(
                        "Could not find checkpointing statistics for checkpoint "
                                + checkpointId
                                + '.',
                        HttpResponseStatus.NOT_FOUND);
            }
        } else {
            throw new RestHandlerException(
                    "Checkpointing was not enabled for job " + jobId + '.',
                    HttpResponseStatus.NOT_FOUND);
        }
    }

    /**
     * Called for each request with the corresponding {@link AbstractCheckpointStats} instance.
     *
     * @param request for further information
     * @param checkpointStats for which the handler is called
     * @return Response
     * @throws RestHandlerException if the handler could not handle the request
     */
    protected abstract R handleCheckpointRequest(
            HandlerRequest<EmptyRequestBody> request, AbstractCheckpointStats checkpointStats)
            throws RestHandlerException;
}
