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/*
 * Copyright (C) 2008 The Guava 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 com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Supplier;
import java.io.Serializable;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@code Table} whose row keys and column keys are ordered by their natural
 * ordering or by supplied comparators. When constructing a {@code TreeBasedTable}, you may provide
 * comparators for the row keys and the column keys, or you may use natural ordering for both.
 *
 * 

The {@link #rowKeySet} method returns a {@link SortedSet} and the {@link #rowMap} method * returns a {@link SortedMap}, instead of the {@link Set} and {@link Map} specified by the {@link * Table} interface. * *

The views returned by {@link #column}, {@link #columnKeySet()}, and {@link #columnMap()} have * iterators that don't support {@code remove()}. Otherwise, all optional operations are supported. * Null row keys, columns keys, and values are not supported. * *

Lookups by row key are often faster than lookups by column key, because the data is stored in * a {@code Map>}. A method call like {@code column(columnKey).get(rowKey)} still runs * quickly, since the row key is provided. However, {@code column(columnKey).size()} takes longer, * since an iteration across all row keys occurs. * *

Because a {@code TreeBasedTable} has unique sorted values for a given row, both {@code * row(rowKey)} and {@code rowMap().get(rowKey)} are {@link SortedMap} instances, instead of the * {@link Map} specified in the {@link Table} interface. * *

Note that this implementation is not synchronized. If multiple threads access this table * concurrently and one of the threads modifies the table, it must be synchronized externally. * *

See the Guava User Guide article on {@code Table}. * * @author Jared Levy * @author Louis Wasserman * @since 7.0 */ @GwtCompatible(serializable = true) public class TreeBasedTable extends StandardRowSortedTable { private final Comparator columnComparator; private static class Factory implements Supplier>, Serializable { final Comparator comparator; Factory(Comparator comparator) { this.comparator = comparator; } @Override public TreeMap get() { return new TreeMap<>(comparator); } private static final long serialVersionUID = 0; } /** * Creates an empty {@code TreeBasedTable} that uses the natural orderings of both row and column * keys. * *

The method signature specifies {@code R extends Comparable} with a raw {@link Comparable}, * instead of {@code R extends Comparable}, and the same for {@code C}. That's * necessary to support classes defined without generics. */ public static TreeBasedTable create() { return new TreeBasedTable<>(Ordering.natural(), Ordering.natural()); } /** * Creates an empty {@code TreeBasedTable} that is ordered by the specified comparators. * * @param rowComparator the comparator that orders the row keys * @param columnComparator the comparator that orders the column keys */ public static TreeBasedTable create( Comparator rowComparator, Comparator columnComparator) { checkNotNull(rowComparator); checkNotNull(columnComparator); return new TreeBasedTable<>(rowComparator, columnComparator); } /** * Creates a {@code TreeBasedTable} with the same mappings and sort order as the specified {@code * TreeBasedTable}. */ public static TreeBasedTable create(TreeBasedTable table) { TreeBasedTable result = new TreeBasedTable<>(table.rowComparator(), table.columnComparator()); result.putAll(table); return result; } TreeBasedTable(Comparator rowComparator, Comparator columnComparator) { super(new TreeMap>(rowComparator), new Factory(columnComparator)); this.columnComparator = columnComparator; } // TODO(jlevy): Move to StandardRowSortedTable? /** * Returns the comparator that orders the rows. With natural ordering, {@link Ordering#natural()} * is returned. * * @deprecated Use {@code table.rowKeySet().comparator()} instead. */ @Deprecated public Comparator rowComparator() { return rowKeySet().comparator(); } /** * Returns the comparator that orders the columns. With natural ordering, {@link * Ordering#natural()} is returned. * * @deprecated Store the {@link Comparator} alongside the {@link Table}. Or, if you know that the * {@link Table} contains at least one value, you can retrieve the {@link Comparator} with: * {@code ((SortedMap) table.rowMap().values().iterator().next()).comparator();}. */ @Deprecated public Comparator columnComparator() { return columnComparator; } // TODO(lowasser): make column return a SortedMap /** * {@inheritDoc} * *

Because a {@code TreeBasedTable} has unique sorted values for a given row, this method * returns a {@link SortedMap}, instead of the {@link Map} specified in the {@link Table} * interface. * * @since 10.0 (mostly * source-compatible since 7.0) */ @Override public SortedMap row(R rowKey) { return new TreeRow(rowKey); } private class TreeRow extends Row implements SortedMap { final @Nullable C lowerBound; final @Nullable C upperBound; TreeRow(R rowKey) { this(rowKey, null, null); } TreeRow(R rowKey, @Nullable C lowerBound, @Nullable C upperBound) { super(rowKey); this.lowerBound = lowerBound; this.upperBound = upperBound; checkArgument( lowerBound == null || upperBound == null || compare(lowerBound, upperBound) <= 0); } @Override public SortedSet keySet() { return new Maps.SortedKeySet<>(this); } @Override public Comparator comparator() { return columnComparator(); } int compare(Object a, Object b) { // pretend we can compare anything @SuppressWarnings("unchecked") Comparator cmp = (Comparator) comparator(); return cmp.compare(a, b); } boolean rangeContains(@Nullable Object o) { return o != null && (lowerBound == null || compare(lowerBound, o) <= 0) && (upperBound == null || compare(upperBound, o) > 0); } @Override public SortedMap subMap(C fromKey, C toKey) { checkArgument(rangeContains(checkNotNull(fromKey)) && rangeContains(checkNotNull(toKey))); return new TreeRow(rowKey, fromKey, toKey); } @Override public SortedMap headMap(C toKey) { checkArgument(rangeContains(checkNotNull(toKey))); return new TreeRow(rowKey, lowerBound, toKey); } @Override public SortedMap tailMap(C fromKey) { checkArgument(rangeContains(checkNotNull(fromKey))); return new TreeRow(rowKey, fromKey, upperBound); } @Override public C firstKey() { SortedMap backing = backingRowMap(); if (backing == null) { throw new NoSuchElementException(); } return backingRowMap().firstKey(); } @Override public C lastKey() { SortedMap backing = backingRowMap(); if (backing == null) { throw new NoSuchElementException(); } return backingRowMap().lastKey(); } transient @Nullable SortedMap wholeRow; /* * If the row was previously empty, we check if there's a new row here every * time we're queried. */ SortedMap wholeRow() { if (wholeRow == null || (wholeRow.isEmpty() && backingMap.containsKey(rowKey))) { wholeRow = (SortedMap) backingMap.get(rowKey); } return wholeRow; } @Override SortedMap backingRowMap() { return (SortedMap) super.backingRowMap(); } @Override SortedMap computeBackingRowMap() { SortedMap map = wholeRow(); if (map != null) { if (lowerBound != null) { map = map.tailMap(lowerBound); } if (upperBound != null) { map = map.headMap(upperBound); } return map; } return null; } @Override void maintainEmptyInvariant() { if (wholeRow() != null && wholeRow.isEmpty()) { backingMap.remove(rowKey); wholeRow = null; backingRowMap = null; } } @Override public boolean containsKey(Object key) { return rangeContains(key) && super.containsKey(key); } @Override public V put(C key, V value) { checkArgument(rangeContains(checkNotNull(key))); return super.put(key, value); } } // rowKeySet() and rowMap() are defined here so they appear in the Javadoc. @Override public SortedSet rowKeySet() { return super.rowKeySet(); } @Override public SortedMap> rowMap() { return super.rowMap(); } /** Overridden column iterator to return columns values in globally sorted order. */ @Override Iterator createColumnKeyIterator() { final Comparator comparator = columnComparator(); final Iterator merged = Iterators.mergeSorted( Iterables.transform( backingMap.values(), new Function, Iterator>() { @Override public Iterator apply(Map input) { return input.keySet().iterator(); } }), comparator); return new AbstractIterator() { @Nullable C lastValue; @Override protected C computeNext() { while (merged.hasNext()) { C next = merged.next(); boolean duplicate = lastValue != null && comparator.compare(next, lastValue) == 0; // Keep looping till we find a non-duplicate value. if (!duplicate) { lastValue = next; return lastValue; } } lastValue = null; // clear reference to unused data return endOfData(); } }; } private static final long serialVersionUID = 0; }