/*
 * 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.jackrabbit.oak.jcr.query;

import java.util.Arrays;
import java.util.Iterator;
import java.util.NoSuchElementException;

import javax.jcr.NodeIterator;
import javax.jcr.RepositoryException;
import javax.jcr.Value;
import javax.jcr.query.QueryResult;
import javax.jcr.query.RowIterator;

import org.apache.jackrabbit.commons.iterator.NodeIteratorAdapter;
import org.apache.jackrabbit.commons.iterator.RowIteratorAdapter;
import org.apache.jackrabbit.oak.api.PropertyState;
import org.apache.jackrabbit.oak.api.PropertyValue;
import org.apache.jackrabbit.oak.api.Result;
import org.apache.jackrabbit.oak.api.ResultRow;
import org.apache.jackrabbit.oak.api.Tree;
import org.apache.jackrabbit.oak.jcr.query.PrefetchIterator.PrefetchOptions;
import org.apache.jackrabbit.oak.jcr.session.NodeImpl;
import org.apache.jackrabbit.oak.jcr.session.SessionContext;
import org.apache.jackrabbit.oak.jcr.delegate.NodeDelegate;
import org.apache.jackrabbit.oak.jcr.delegate.SessionDelegate;
import org.apache.jackrabbit.oak.plugins.memory.PropertyValues;
import org.apache.jackrabbit.oak.plugins.value.jcr.PartialValueFactory;
import org.jetbrains.annotations.Nullable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * The implementation of the corresponding JCR interface.
 */
public class QueryResultImpl implements QueryResult {
    private static final Logger queryOpsLogger = LoggerFactory.getLogger("org.apache.jackrabbit.oak.jcr.operations.query");
    static final Logger LOG = LoggerFactory.getLogger(QueryResultImpl.class);

    protected final SessionContext sessionContext;
    
    final Result result;

    private final SessionDelegate sessionDelegate;

    private final PartialValueFactory valueFactory;

    public QueryResultImpl(SessionContext sessionContext, Result result) {
        this.sessionContext = sessionContext;
        this.sessionDelegate = sessionContext.getSessionDelegate();
        this.result = result;
        this.valueFactory = new PartialValueFactory(sessionContext, sessionContext.getBlobAccessProvider());
    }

    @Override
    public String[] getColumnNames() {
        return result.getColumnNames();
    }

    @Override
    public String[] getSelectorNames() {
        return result.getSelectorNames();
    }

    @Override
    public RowIterator getRows() throws RepositoryException {
        Iterator<RowImpl> rowIterator = new Iterator<>() {

            private final Iterator<? extends ResultRow> it = result.getRows().iterator();
            private final String pathSelector;
            private RowImpl current;
            private int rowCount;
            //Avoid log check for every row access
            private final boolean debugEnabled = queryOpsLogger.isDebugEnabled();

            {
                String[] columnSelectorNames = result.getColumnSelectorNames();
                if (columnSelectorNames.length == 1) {
                    pathSelector = columnSelectorNames[0];
                } else {
                    pathSelector = null;
                }
                fetch();
            }

            private void fetch() {
                if (it.hasNext()) {
                    current = new RowImpl(
                            QueryResultImpl.this, it.next(), pathSelector);
                    if (debugEnabled) {
                        rowCount++;
                        if (rowCount % 100 == 0) {
                            queryOpsLogger.debug("Iterated over [{}] results so far", rowCount);
                        }
                    }
                } else {
                    current = null;
                }
            }

            @Override
            public boolean hasNext() {
                return current != null;
            }

            @Override
            public RowImpl next() {
                if (current == null) {
                    throw new NoSuchElementException();
                }
                RowImpl r = current;
                fetch();
                return r;
            }

            @Override
            public void remove() {
                throw new UnsupportedOperationException();
            }

        };
        final PrefetchIterator<RowImpl> prefIt = new PrefetchIterator<>(
                sessionDelegate.sync(rowIterator),
                new PrefetchOptions() {
                    {
                        size = result.getSize();
                        fastSize = sessionContext.getFastQueryResultSize();
                        fastSizeCallback = result;
                    }
                });
        return new RowIteratorAdapter(prefIt) {
            @Override
            public long getSize() {
                return prefIt.size();
            }
        };
    }

    @Nullable
    NodeImpl<? extends NodeDelegate> getNode(Tree tree) throws RepositoryException {
        if (tree != null && tree.exists()) {
            NodeDelegate node = new NodeDelegate(sessionDelegate, tree);
            return NodeImpl.createNode(node, sessionContext);
        }
        return null;
    }

    @Override
    public NodeIterator getNodes() throws RepositoryException {
        String[] columnSelectorNames = result.getColumnSelectorNames();
        if (columnSelectorNames.length != 1) {
            throw new RepositoryException("Query contains more than one selector: " +
                    Arrays.toString(columnSelectorNames));
        }
        final String selectorName = columnSelectorNames[0];
        if (selectorName == null) {
            throw new RepositoryException("Query does not contain a selector: " +
                    Arrays.toString(columnSelectorNames));
        }
        Iterator<NodeImpl<? extends NodeDelegate>> nodeIterator =
                new Iterator<>() {

                    private final Iterator<? extends ResultRow> it = result.getRows().iterator();
                    private NodeImpl<? extends NodeDelegate> current;

                    {
                        fetch();
                    }

                    private void fetch() {
                        current = null;
                        while (it.hasNext()) {
                            ResultRow r = it.next();
                            Tree tree = r.getTree(selectorName);
                            if (tree != null && tree.exists()) {
                                try {
                                    current = getNode(tree);
                                    break;
                                } catch (RepositoryException e) {
                                    LOG.warn("Unable to fetch result node for path "
                                            + tree.getPath(), e);
                                }
                            }
                        }
                    }

                    @Override
                    public boolean hasNext() {
                        return current != null;
                    }

                    @Override
                    public NodeImpl<? extends NodeDelegate> next() {
                        if (current == null) {
                            throw new NoSuchElementException();
                        }
                        NodeImpl<? extends NodeDelegate> n = current;
                        fetch();
                        return n;
                    }

                    @Override
                    public void remove() {
                        throw new UnsupportedOperationException();
                    }

                };
        final PrefetchIterator<NodeImpl<? extends NodeDelegate>> prefIt =
                new PrefetchIterator<>(
                        sessionDelegate.sync(nodeIterator),
                        new PrefetchOptions() {
                            {
                                size = result.getSize();
                                fastSize = sessionContext.getFastQueryResultSize();
                                fastSizeCallback = result;
                            }
                        });
        return new NodeIteratorAdapter(prefIt) {
            @Override
            public long getSize() {
                return prefIt.size();
            }
        };
    }

    Value createValue(PropertyValue value) {
        if (value == null) {
            return null;
        }
        PropertyState state = PropertyValues.create(value);
        if (state == null) {
            throw new IllegalArgumentException("Failed to convert the specified property value to a property state.");
        }
        return valueFactory.createValue(state);
    }

}
