/*
 * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.controller.cluster.datastore.persisted;

import static com.google.common.math.IntMath.ceilingPowerOfTwo;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.MoreObjects;
import com.google.common.io.ByteStreams;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.ObjectOutput;
import java.io.Serializable;
import org.apache.commons.lang3.SerializationUtils;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.NonNullByDefault;
import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
import org.opendaylight.controller.cluster.io.ChunkedByteArray;
import org.opendaylight.controller.cluster.io.ChunkedOutputStream;
import org.opendaylight.controller.cluster.raft.messages.IdentifiablePayload;
import org.opendaylight.yangtools.yang.data.api.schema.stream.ReusableStreamReceiver;
import org.opendaylight.yangtools.yang.data.codec.binfmt.NormalizedNodeStreamVersion;
import org.opendaylight.yangtools.yang.data.impl.schema.ReusableImmutableNormalizedNodeStreamWriter;
import org.opendaylight.yangtools.yang.data.tree.api.DataTreeCandidate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Payload persisted when a transaction commits. It contains the transaction identifier and the
 * {@link DataTreeCandidate}
 *
 * @author Robert Varga
 */
@Beta
public abstract sealed class CommitTransactionPayload extends IdentifiablePayload<TransactionIdentifier>
        implements Serializable {
    @NonNullByDefault
    public record CandidateTransaction(
            TransactionIdentifier transactionId,
            DataTreeCandidate candidate,
            NormalizedNodeStreamVersion streamVersion) {
        public CandidateTransaction {
            requireNonNull(transactionId);
            requireNonNull(candidate);
            requireNonNull(streamVersion);
        }
    }

    private static final Logger LOG = LoggerFactory.getLogger(CommitTransactionPayload.class);
    private static final long serialVersionUID = 1L;

    static final int MAX_ARRAY_SIZE = ceilingPowerOfTwo(Integer.getInteger(
        "org.opendaylight.controller.cluster.datastore.persisted.max-array-size", 256 * 1024));

    private volatile CandidateTransaction candidate = null;

    private CommitTransactionPayload() {
        // hidden on purpose
    }

    public static @NonNull CommitTransactionPayload create(final TransactionIdentifier transactionId,
            final DataTreeCandidate candidate, final PayloadVersion version, final int initialSerializedBufferCapacity)
                    throws IOException {
        final var cos = new ChunkedOutputStream(initialSerializedBufferCapacity, MAX_ARRAY_SIZE);
        try (var dos = new DataOutputStream(cos)) {
            transactionId.writeTo(dos);
            DataTreeCandidateInputOutput.writeDataTreeCandidate(dos, version, candidate);
        }

        final var source = cos.toVariant();
        LOG.debug("Initial buffer capacity {}, actual serialized size {}", initialSerializedBufferCapacity, cos.size());
        return source.isFirst() ? new Simple(source.getFirst()) : new Chunked(source.getSecond());
    }

    @VisibleForTesting
    public static @NonNull CommitTransactionPayload create(final TransactionIdentifier transactionId,
            final DataTreeCandidate candidate, final PayloadVersion version) throws IOException {
        return create(transactionId, candidate, version, 512);
    }

    @VisibleForTesting
    public static @NonNull CommitTransactionPayload create(final TransactionIdentifier transactionId,
            final DataTreeCandidate candidate) throws IOException {
        return create(transactionId, candidate, PayloadVersion.current());
    }

    public @NonNull CandidateTransaction getCandidate() throws IOException {
        var localCandidate = candidate;
        if (localCandidate == null) {
            synchronized (this) {
                localCandidate = candidate;
                if (localCandidate == null) {
                    candidate = localCandidate = getCandidate(ReusableImmutableNormalizedNodeStreamWriter.create());
                }
            }
        }
        return localCandidate;
    }

    public final @NonNull CandidateTransaction getCandidate(final ReusableStreamReceiver receiver) throws IOException {
        final var in = newDataInput();
        final var transactionId = TransactionIdentifier.readFrom(in);
        final var readCandidate = DataTreeCandidateInputOutput.readDataTreeCandidate(in, receiver);

        return new CandidateTransaction(transactionId, readCandidate.candidate(), readCandidate.version());
    }

    @Override
    public TransactionIdentifier getIdentifier() {
        try  {
            return getCandidate().transactionId();
        } catch (IOException e) {
            throw new IllegalStateException("Candidate deserialization failed.", e);
        }
    }

    @Override
    public final int serializedSize() {
        // TODO: this is not entirely accurate as the the byte[] can be chunked by the serialization stream
        return ProxySizeHolder.PROXY_SIZE + size();
    }

    /**
     * The cached candidate needs to be cleared after it is done applying to the DataTree, otherwise it would be keeping
     * deserialized in memory which are not needed anymore leading to wasted memory. This lets the payload know that
     * this was the last time the candidate was needed ant it is safe to be cleared.
     */
    public @NonNull CandidateTransaction acquireCandidate() throws IOException {
        final var localCandidate = getCandidate();
        candidate = null;
        return localCandidate;
    }

    @Override
    public final String toString() {
        final var helper = MoreObjects.toStringHelper(this);
        final var localCandidate = candidate;
        if (localCandidate != null) {
            helper.add("identifier", candidate.transactionId());
        }
        return helper.add("size", size()).toString();
    }

    abstract void writeBytes(ObjectOutput out) throws IOException;

    abstract DataInput newDataInput();

    @Override
    public final Object writeReplace() {
        return new CT(this);
    }

    static final class Simple extends CommitTransactionPayload {
        @java.io.Serial
        private static final long serialVersionUID = 1L;

        private final byte[] serialized;

        Simple(final byte[] serialized) {
            this.serialized = requireNonNull(serialized);
        }

        @Override
        public int size() {
            return serialized.length;
        }

        @Override
        DataInput newDataInput() {
            return ByteStreams.newDataInput(serialized);
        }

        @Override
        void writeBytes(final ObjectOutput out) throws IOException {
            out.write(serialized);
        }
    }

    static final class Chunked extends CommitTransactionPayload {
        @java.io.Serial
        private static final long serialVersionUID = 1L;

        @SuppressFBWarnings(value = "SE_BAD_FIELD", justification = "Handled via serialization proxy")
        private final ChunkedByteArray source;

        Chunked(final ChunkedByteArray source) {
            this.source = requireNonNull(source);
        }

        @Override
        void writeBytes(final ObjectOutput out) throws IOException {
            source.copyTo(out);
        }

        @Override
        public int size() {
            return source.size();
        }

        @Override
        DataInput newDataInput() {
            return new DataInputStream(source.openStream());
        }
    }

    // Exists to break initialization dependency between CommitTransactionPayload/Simple/Proxy
    private static final class ProxySizeHolder {
        static final int PROXY_SIZE = SerializationUtils.serialize(new CT(new Simple(new byte[0]))).length;

        private ProxySizeHolder() {
            // Hidden on purpose
        }
    }
}