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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [https://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.impl.newapi;

import org.neo4j.internal.kernel.api.NodeCursor;
import org.neo4j.internal.kernel.api.PropertyCursor;
import org.neo4j.internal.kernel.api.Read;
import org.neo4j.internal.kernel.api.RelationshipDataAccessor;
import org.neo4j.kernel.api.AccessModeProvider;
import org.neo4j.kernel.api.txstate.TxStateHolder;
import org.neo4j.storageengine.api.LongReference;
import org.neo4j.storageengine.api.PropertySelection;
import org.neo4j.storageengine.api.Reference;
import org.neo4j.storageengine.api.RelationshipVisitor;
import org.neo4j.storageengine.api.StorageRelationshipCursor;

abstract class DefaultRelationshipCursor extends TraceableCursorImpl
        implements RelationshipDataAccessor {
    protected boolean hasChanges;
    boolean checkHasChanges;
    Read read;
    TxStateHolder txStateHolder;
    AccessModeProvider accessModeProvider;

    final StorageRelationshipCursor storeCursor;
    RelationshipVisitor relationshipTxStateDataVisitor = new TxStateDataVisitor();
    // The visitor above will update the fields below
    long currentAddedInTx = LongReference.NULL;
    private int txStateTypeId;
    long txStateSourceNodeReference;
    long txStateTargetNodeReference;

    DefaultRelationshipCursor(StorageRelationshipCursor storeCursor, CursorPool pool) {
        super(pool);
        this.storeCursor = storeCursor;
    }

    protected void init(Read read, TxStateHolder txStateHolder, AccessModeProvider accessModeProvider) {
        this.currentAddedInTx = LongReference.NULL;
        this.read = read;
        this.txStateHolder = txStateHolder;
        this.accessModeProvider = accessModeProvider;
        this.checkHasChanges = true;
    }

    @Override
    public long relationshipReference() {
        return currentAddedInTx != LongReference.NULL ? currentAddedInTx : storeCursor.entityReference();
    }

    @Override
    public int type() {
        return currentAddedInTx != LongReference.NULL ? txStateTypeId : storeCursor.type();
    }

    @Override
    public void source(NodeCursor cursor) {
        read.singleNode(sourceNodeReference(), cursor);
    }

    @Override
    public void target(NodeCursor cursor) {
        read.singleNode(targetNodeReference(), cursor);
    }

    @Override
    public void properties(PropertyCursor cursor, PropertySelection selection) {
        ((DefaultPropertyCursor) cursor).initRelationship(this, selection, read, txStateHolder, accessModeProvider);
    }

    @Override
    public long sourceNodeReference() {
        return currentAddedInTx != LongReference.NULL ? txStateSourceNodeReference : storeCursor.sourceNodeReference();
    }

    @Override
    public long targetNodeReference() {
        return currentAddedInTx != LongReference.NULL ? txStateTargetNodeReference : storeCursor.targetNodeReference();
    }

    @Override
    public Reference propertiesReference() {
        return currentAddedInTx != LongReference.NULL
                ? LongReference.NULL_REFERENCE
                : storeCursor.propertiesReference();
    }

    protected abstract void collectAddedTxStateSnapshot();

    protected boolean currentRelationshipIsAddedInTx() {
        return currentAddedInTx != LongReference.NULL;
    }

    /**
     * RelationshipCursor should only see changes that are there from the beginning
     * otherwise it will not be stable.
     */
    protected boolean hasChanges() {
        if (checkHasChanges) {
            hasChanges = txStateHolder.hasTxStateWithChanges();
            if (hasChanges) {
                collectAddedTxStateSnapshot();
            }
            checkHasChanges = false;
        }

        return hasChanges;
    }

    private class TxStateDataVisitor implements RelationshipVisitor {
        @Override
        public void visit(long relationshipId, int typeId, long sourceNodeReference, long targetNodeReference) {
            currentAddedInTx = relationshipId;
            txStateTypeId = typeId;
            txStateSourceNodeReference = sourceNodeReference;
            txStateTargetNodeReference = targetNodeReference;
        }
    }
}