/*
 * 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.collect.CollectPreconditions.checkNonnegative;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Supplier;

/**
 * Implementation of {@link Table} using hash tables.
 *
 * <p>
 * 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.
 *
 * <p>
 * Lookups by row key are often faster than lookups by column key, because the
 * data is stored in a {@code Map<R, Map<C, V>>}. 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.
 *
 * <p>
 * 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.
 * 
 * <p>
 * See the Guava User Guide article on <a href=
 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Table">
 * {@code Table}</a>.
 *
 * @author Jared Levy
 * @since 7.0
 */
@GwtCompatible(serializable = true)
public class HashBasedTable<R, C, V> extends StandardTable<R, C, V> {
	private static class Factory<C, V> implements Supplier<Map<C, V>>, Serializable {
		final int expectedSize;

		Factory(int expectedSize) {
			this.expectedSize = expectedSize;
		}

		@Override
		public Map<C, V> get() {
			return Maps.newHashMapWithExpectedSize(expectedSize);
		}

		private static final long serialVersionUID = 0;
	}

	/**
	 * Creates an empty {@code HashBasedTable}.
	 */
	public static <R, C, V> HashBasedTable<R, C, V> create() {
		return new HashBasedTable<R, C, V>(new HashMap<R, Map<C, V>>(), new Factory<C, V>(0));
	}

	/**
	 * Creates an empty {@code HashBasedTable} with the specified map sizes.
	 *
	 * @param expectedRows        the expected number of distinct row keys
	 * @param expectedCellsPerRow the expected number of column key / value mappings
	 *                            in each row
	 * @throws IllegalArgumentException if {@code expectedRows} or {@code
	 *     expectedCellsPerRow}      is negative
	 */
	public static <R, C, V> HashBasedTable<R, C, V> create(int expectedRows, int expectedCellsPerRow) {
		checkNonnegative(expectedCellsPerRow, "expectedCellsPerRow");
		Map<R, Map<C, V>> backingMap = Maps.newHashMapWithExpectedSize(expectedRows);
		return new HashBasedTable<R, C, V>(backingMap, new Factory<C, V>(expectedCellsPerRow));
	}

	/**
	 * Creates a {@code HashBasedTable} with the same mappings as the specified
	 * table.
	 *
	 * @param table the table to copy
	 * @throws NullPointerException if any of the row keys, column keys, or values
	 *                              in {@code table} is null
	 */
	public static <R, C, V> HashBasedTable<R, C, V> create(Table<? extends R, ? extends C, ? extends V> table) {
		HashBasedTable<R, C, V> result = create();
		result.putAll(table);
		return result;
	}

	HashBasedTable(Map<R, Map<C, V>> backingMap, Factory<C, V> factory) {
		super(backingMap, factory);
	}

	// Overriding so NullPointerTester test passes.

	@Override
	public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
		return super.contains(rowKey, columnKey);
	}

	@Override
	public boolean containsColumn(@Nullable Object columnKey) {
		return super.containsColumn(columnKey);
	}

	@Override
	public boolean containsRow(@Nullable Object rowKey) {
		return super.containsRow(rowKey);
	}

	@Override
	public boolean containsValue(@Nullable Object value) {
		return super.containsValue(value);
	}

	@Override
	public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
		return super.get(rowKey, columnKey);
	}

	@Override
	public boolean equals(@Nullable Object obj) {
		return super.equals(obj);
	}

	@Override
	public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
		return super.remove(rowKey, columnKey);
	}

	private static final long serialVersionUID = 0;
}
