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/*
 * Copyright 2017-2020 original authors
 *
 * 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.micronaut.http.server.codec;

import io.micronaut.context.annotation.BootstrapContextCompatible;
import io.micronaut.core.annotation.Internal;
import io.micronaut.http.codec.CodecConfiguration;
import io.micronaut.core.io.buffer.ByteBuffer;
import io.micronaut.core.io.buffer.ByteBufferFactory;
import io.micronaut.core.type.Argument;
import io.micronaut.http.MediaType;
import io.micronaut.http.codec.CodecException;
import io.micronaut.http.codec.MediaTypeCodec;
import io.micronaut.http.codec.MediaTypeCodecRegistry;
import io.micronaut.http.sse.Event;
import io.micronaut.runtime.ApplicationConfiguration;

import edu.umd.cs.findbugs.annotations.Nullable;
import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Provider;
import javax.inject.Singleton;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * A {@link MediaTypeCodec} that will encode {@link Event} objects in order to support Server Sent Events.
 *
 * @author Graeme Rocher
 * @since 1.0
 */
@Singleton
@Internal
@BootstrapContextCompatible
public class TextStreamCodec implements MediaTypeCodec {

    public static final String CONFIGURATION_QUALIFIER = "text-stream";

    private static final byte[] DATA_PREFIX = "data: ".getBytes(StandardCharsets.UTF_8);
    private static final byte[] EVENT_PREFIX = "event: ".getBytes(StandardCharsets.UTF_8);
    private static final byte[] ID_PREFIX = "id: ".getBytes(StandardCharsets.UTF_8);
    private static final byte[] RETRY_PREFIX = "retry: ".getBytes(StandardCharsets.UTF_8);
    private static final byte[] COMMENT_PREFIX = ": ".getBytes(StandardCharsets.UTF_8);
    private static final byte[] NEWLINE = "\n".getBytes(StandardCharsets.UTF_8);

    private final Provider codecRegistryProvider;
    private final ByteBufferFactory byteBufferFactory;
    private final List additionalTypes;
    private final Charset defaultCharset;
    private MediaTypeCodecRegistry codecRegistry;

    /**
     * @param applicationConfiguration The application configuration
     * @param byteBufferFactory     A byte buffer factory
     * @param codecRegistryProvider A media type codec registry
     * @param codecConfiguration    The configuration for the codec
     */
    @Inject
    public TextStreamCodec(
            ApplicationConfiguration applicationConfiguration,
            ByteBufferFactory byteBufferFactory,
            Provider codecRegistryProvider,
            @Named(CONFIGURATION_QUALIFIER) @Nullable CodecConfiguration codecConfiguration) {
        this(applicationConfiguration.getDefaultCharset(), byteBufferFactory, codecRegistryProvider, codecConfiguration);
    }

    /**
     * @param defaultCharset The default charset
     * @param byteBufferFactory     A byte buffer factory
     * @param codecRegistryProvider A media type codec registry
     * @param codecConfiguration    The configuration for the codec
     */
    protected TextStreamCodec(
            Charset defaultCharset,
            ByteBufferFactory byteBufferFactory,
            Provider codecRegistryProvider,
            @Named(CONFIGURATION_QUALIFIER) @Nullable CodecConfiguration codecConfiguration) {
        this.defaultCharset = defaultCharset;
        this.byteBufferFactory = byteBufferFactory;
        this.codecRegistryProvider = codecRegistryProvider;
        if (codecConfiguration != null) {
            this.additionalTypes = codecConfiguration.getAdditionalTypes();
        } else {
            this.additionalTypes = Collections.emptyList();
        }
    }

    @Override
    public Collection getMediaTypes() {
        List mediaTypes = new ArrayList<>();
        mediaTypes.add(MediaType.TEXT_EVENT_STREAM_TYPE);
        mediaTypes.addAll(additionalTypes);
        return mediaTypes;
    }

    @Override
    public  T decode(Argument type, InputStream inputStream) throws CodecException {
        throw new UnsupportedOperationException("This codec currently only supports encoding");
    }

    @Override
    public  T decode(Class type, InputStream inputStream) throws CodecException {
        throw new UnsupportedOperationException("This codec currently only supports encoding");
    }

    @Override
    public  void encode(T object, OutputStream outputStream) throws CodecException {
        try {
            outputStream.write(encode(object));
        } catch (IOException e) {
            throw new CodecException("I/O error occurred encoding object to output stream: " + e.getMessage(), e);
        }
    }

    @Override
    public  byte[] encode(T object) throws CodecException {
        ByteBuffer buffer = encode(object, byteBufferFactory);
        return buffer.toByteArray();
    }

    @SuppressWarnings("MagicNumber")
    @Override
    public  ByteBuffer encode(T object, ByteBufferFactory allocator) throws CodecException {
        Event