/*
 * Copyright (c) 2017, 2019 Oracle and/or its affiliates. All rights reserved.
 *
 * Licensed 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 io.helidon.webserver.jersey;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.logging.Logger;

import javax.ws.rs.core.MediaType;

import io.helidon.common.http.DataChunk;
import io.helidon.common.http.Http;
import io.helidon.common.reactive.Multi;
import io.helidon.common.reactive.OutputStreamPublisher;
import io.helidon.webserver.ConnectionClosedException;
import io.helidon.webserver.ServerRequest;
import io.helidon.webserver.ServerResponse;

import org.glassfish.jersey.server.ContainerException;
import org.glassfish.jersey.server.ContainerResponse;
import org.glassfish.jersey.server.spi.ContainerResponseWriter;

/**
 * The ResponseWriter.
 */
class ResponseWriter implements ContainerResponseWriter {

    private static final Logger LOGGER = Logger.getLogger(ResponseWriter.class.getName());

    private final OutputStreamPublisher publisher = new OutputStreamPublisher() {
        @Override
        public void write(byte[] b) throws IOException {
            try {
                super.write(b);
            } catch (ConnectionClosedException e) {
                throw new IOException("Cannot publish more bytes due to a connection close.", e);
            }
        }

        @Override
        public void write(byte[] b, int off, int len) throws IOException {
            try {
                super.write(b, off, len);
            } catch (ConnectionClosedException e) {
                throw new IOException("Cannot publish more bytes due to a connection close.", e);
            }
        }

        @Override
        public void write(int b) throws IOException {
            try {
                super.write(b);
            } catch (ConnectionClosedException e) {
                throw new IOException("Cannot publish more bytes due to a connection close.", e);
            }
        }

        @Override
        public void close() throws IOException {
            try {
                super.signalCloseComplete(null);
                super.close();
            } catch (ConnectionClosedException e) {
                throw new IOException("Cannot close the connection because it's already closed.", e);
            }
        }

        @Override
        public void flush() throws IOException {
            try {
                super.flush();
            } catch (ConnectionClosedException e) {
                throw new IOException("Cannot flush on the connection because it's closed.", e);
            }
        }
    };

    private final ServerResponse res;
    private final ServerRequest req;
    private final CompletableFuture<Void> whenHandleFinishes;

    ResponseWriter(ServerResponse res, ServerRequest req, CompletableFuture<Void> whenHandleFinishes) {
        this.res = res;
        this.req = req;
        this.whenHandleFinishes = whenHandleFinishes;
    }

    @Override
    public OutputStream writeResponseStatusAndHeaders(long contentLength, ContainerResponse context)
            throws ContainerException {

        //
        // TODO also check that nothing was written an nothing was read
        //
        if (context.getStatus() == 404 && contentLength == 0) {
            whenHandleFinishes.thenRun(() -> {
                LOGGER.finer("Skipping the handling and forwarding to downstream WebServer filters.");

                req.next();
            });
            return new OutputStream() {
                @Override
                public void write(int b) throws IOException {
                    // noop
                }
            };
        }

        res.status(Http.ResponseStatus.create(context.getStatus(), context.getStatusInfo().getReasonPhrase()));

        if (contentLength >= 0) {
            res.headers().put(Http.Header.CONTENT_LENGTH, String.valueOf(contentLength));
        }

        for (Map.Entry<String, List<String>> entry : context.getStringHeaders().entrySet()) {
            res.headers().put(entry.getKey(), entry.getValue());
        }

        res.send(Multi.from(publisher)
                .map(byteBuffer -> DataChunk.create(doFlush(context, byteBuffer), byteBuffer, true)));

        return publisher;
    }

    @Override
    public boolean suspend(long timeOut, TimeUnit timeUnit, TimeoutHandler timeoutHandler) {
        if (timeOut != 0) {
            throw new UnsupportedOperationException("Currently, time limited suspension is not supported!");
        }
        return true;
    }

    @Override
    public void setSuspendTimeout(long timeOut, TimeUnit timeUnit) throws IllegalStateException {
        throw new UnsupportedOperationException("Currently, extending the suspension time is not supported!");
    }

    @Override
    public void commit() {
        try {
            // Jersey doesn't close the OutputStream when there is no entity
            // as such the publisher needs to be closed from here ...
            // it is assumed it's possible to close the publisher, the OutputStream, multiple times
            publisher.close();
        } catch (IOException e) {
            // based on implementation of 'close', this never happens
            throw new IllegalStateException("Unexpected IO Exception received!", e);
        }
    }

    @Override
    public void failure(Throwable error) {
        LOGGER.finer(() -> "Jersey handling finished with an exception; message: " + error.getMessage());

        req.next(error);
    }

    @Override
    public boolean enableResponseBuffering() {
        // Jersey should not try to do the buffering
        return false;
    }

    /**
     * Flush buffer if using SSE or if an empty buffer is received for writing. See
     * {@link OutputStreamPublisher#flush()}. Manual flushing is required to support
     * {@link javax.ws.rs.core.StreamingOutput} in MP.
     *
     * @param context The container response.
     * @param byteBuffer The byte buffer to write.
     * @return Outcome of test.
     */
    private static boolean doFlush(ContainerResponse context, ByteBuffer byteBuffer) {
        return MediaType.SERVER_SENT_EVENTS_TYPE.isCompatible(context.getMediaType())
                || byteBuffer.hasArray() && byteBuffer.array().length == 0;
    }
}
