/*
    * 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 com.google.common.annotations.GwtCompatible;
  import com.google.common.base.Supplier;
  
  import java.io.Serializable;
  import java.util.HashMap;
  import java.util.Map;
  
  import javax.annotation.Nullable;
  
  /**
   * 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;
 }