/*
 * 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 java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;

import javax.annotation.Nullable;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Objects;
import com.google.common.base.Supplier;
import com.google.common.collect.Table.Cell;

/**
 * Provides static methods that involve a {@code Table}.
 * 
 * <p>
 * See the Guava User Guide article on <a href=
 * "http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained#Tables">
 * {@code Tables}</a>.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 7.0
 */
@GwtCompatible
public final class Tables {
	private Tables() {
	}

	/**
	 * Returns an immutable cell with the specified row key, column key, and value.
	 *
	 * <p>
	 * The returned cell is serializable.
	 *
	 * @param rowKey    the row key to be associated with the returned cell
	 * @param columnKey the column key to be associated with the returned cell
	 * @param value     the value to be associated with the returned cell
	 */
	public static <R, C, V> Cell<R, C, V> immutableCell(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
		return new ImmutableCell<R, C, V>(rowKey, columnKey, value);
	}

	static final class ImmutableCell<R, C, V> extends AbstractCell<R, C, V> implements Serializable {
		private final R rowKey;
		private final C columnKey;
		private final V value;

		ImmutableCell(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
			this.rowKey = rowKey;
			this.columnKey = columnKey;
			this.value = value;
		}

		@Override
		public R getRowKey() {
			return rowKey;
		}

		@Override
		public C getColumnKey() {
			return columnKey;
		}

		@Override
		public V getValue() {
			return value;
		}

		private static final long serialVersionUID = 0;
	}

	abstract static class AbstractCell<R, C, V> implements Cell<R, C, V> {
		// needed for serialization
		AbstractCell() {
		}

		@Override
		public boolean equals(Object obj) {
			if (obj == this) {
				return true;
			}
			if (obj instanceof Cell) {
				Cell<?, ?, ?> other = (Cell<?, ?, ?>) obj;
				return Objects.equal(getRowKey(), other.getRowKey())
						&& Objects.equal(getColumnKey(), other.getColumnKey())
						&& Objects.equal(getValue(), other.getValue());
			}
			return false;
		}

		@Override
		public int hashCode() {
			return Objects.hashCode(getRowKey(), getColumnKey(), getValue());
		}

		@Override
		public String toString() {
			return "(" + getRowKey() + "," + getColumnKey() + ")=" + getValue();
		}
	}

	/**
	 * Creates a transposed view of a given table that flips its row and column
	 * keys. In other words, calling {@code get(columnKey, rowKey)} on the generated
	 * table always returns the same value as calling {@code
	 * get(rowKey, columnKey)} on the original table. Updating the original table
	 * changes the contents of the transposed table and vice versa.
	 *
	 * <p>
	 * The returned table supports update operations as long as the input table
	 * supports the analogous operation with swapped rows and columns. For example,
	 * in a {@link HashBasedTable} instance, {@code
	 * rowKeySet().iterator()} supports {@code remove()} but {@code
	 * columnKeySet().iterator()} doesn't. With a transposed {@link HashBasedTable},
	 * it's the other way around.
	 */
	public static <R, C, V> Table<C, R, V> transpose(Table<R, C, V> table) {
		return (table instanceof TransposeTable) ? ((TransposeTable<R, C, V>) table).original
				: new TransposeTable<C, R, V>(table);
	}

	private static class TransposeTable<C, R, V> extends AbstractTable<C, R, V> {
		final Table<R, C, V> original;

		TransposeTable(Table<R, C, V> original) {
			this.original = checkNotNull(original);
		}

		@Override
		public void clear() {
			original.clear();
		}

		@Override
		public Map<C, V> column(R columnKey) {
			return original.row(columnKey);
		}

		@Override
		public Set<R> columnKeySet() {
			return original.rowKeySet();
		}

		@Override
		public Map<R, Map<C, V>> columnMap() {
			return original.rowMap();
		}

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

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

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

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

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

		@Override
		public V put(C rowKey, R columnKey, V value) {
			return original.put(columnKey, rowKey, value);
		}

		@Override
		public void putAll(Table<? extends C, ? extends R, ? extends V> table) {
			original.putAll(transpose(table));
		}

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

		@Override
		public Map<R, V> row(C rowKey) {
			return original.column(rowKey);
		}

		@Override
		public Set<C> rowKeySet() {
			return original.columnKeySet();
		}

		@Override
		public Map<C, Map<R, V>> rowMap() {
			return original.columnMap();
		}

		@Override
		public int size() {
			return original.size();
		}

		@Override
		public Collection<V> values() {
			return original.values();
		}

		// Will cast TRANSPOSE_CELL to a type that always succeeds
		private static final Function<Cell<?, ?, ?>, Cell<?, ?, ?>> TRANSPOSE_CELL = new Function<Cell<?, ?, ?>, Cell<?, ?, ?>>() {
			@Override
			public Cell<?, ?, ?> apply(Cell<?, ?, ?> cell) {
				return immutableCell(cell.getColumnKey(), cell.getRowKey(), cell.getValue());
			}
		};

		@SuppressWarnings("unchecked")
		@Override
		Iterator<Cell<C, R, V>> cellIterator() {
			return Iterators.transform(original.cellSet().iterator(), (Function) TRANSPOSE_CELL);
		}
	}

	/**
	 * Creates a table that uses the specified backing map and factory. It can
	 * generate a table based on arbitrary {@link Map} classes.
	 *
	 * <p>
	 * The {@code factory}-generated and {@code backingMap} classes determine the
	 * table iteration order. However, the table's {@code row()} method returns
	 * instances of a different class than {@code factory.get()} does.
	 *
	 * <p>
	 * Call this method only when the simpler factory methods in classes like
	 * {@link HashBasedTable} and {@link TreeBasedTable} won't suffice.
	 *
	 * <p>
	 * The views returned by the {@code Table} methods {@link Table#column},
	 * {@link Table#columnKeySet}, and {@link Table#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>
	 * The table is serializable if {@code backingMap}, {@code factory}, the maps
	 * generated by {@code factory}, and the table contents are all serializable.
	 *
	 * <p>
	 * Note: the table assumes complete ownership over of {@code backingMap} and the
	 * maps returned by {@code factory}. Those objects should not be manually
	 * updated and they should not use soft, weak, or phantom references.
	 *
	 * @param backingMap place to store the mapping from each row key to its
	 *                   corresponding column key / value map
	 * @param factory    supplier of new, empty maps that will each hold all column
	 *                   key / value mappings for a given row key
	 * @throws IllegalArgumentException if {@code backingMap} is not empty
	 * @since 10.0
	 */
	@Beta
	public static <R, C, V> Table<R, C, V> newCustomTable(Map<R, Map<C, V>> backingMap,
			Supplier<? extends Map<C, V>> factory) {
		checkArgument(backingMap.isEmpty());
		checkNotNull(factory);
		// TODO(jlevy): Wrap factory to validate that the supplied maps are empty?
		return new StandardTable<R, C, V>(backingMap, factory);
	}

	/**
	 * Returns a view of a table where each value is transformed by a function. All
	 * other properties of the table, such as iteration order, are left intact.
	 *
	 * <p>
	 * Changes in the underlying table are reflected in this view. Conversely, this
	 * view supports removal operations, and these are reflected in the underlying
	 * table.
	 *
	 * <p>
	 * It's acceptable for the underlying table to contain null keys, and even null
	 * values provided that the function is capable of accepting null input. The
	 * transformed table might contain null values, if the function sometimes gives
	 * a null result.
	 *
	 * <p>
	 * The returned table is not thread-safe or serializable, even if the underlying
	 * table is.
	 *
	 * <p>
	 * The function is applied lazily, invoked when needed. This is necessary for
	 * the returned table to be a view, but it means that the function will be
	 * applied many times for bulk operations like {@link Table#containsValue} and
	 * {@code Table.toString()}. For this to perform well, {@code function} should
	 * be fast. To avoid lazy evaluation when the returned table doesn't need to be
	 * a view, copy the returned table into a new table of your choosing.
	 *
	 * @since 10.0
	 */
	@Beta
	public static <R, C, V1, V2> Table<R, C, V2> transformValues(Table<R, C, V1> fromTable,
			Function<? super V1, V2> function) {
		return new TransformedTable<R, C, V1, V2>(fromTable, function);
	}

	private static class TransformedTable<R, C, V1, V2> extends AbstractTable<R, C, V2> {
		final Table<R, C, V1> fromTable;
		final Function<? super V1, V2> function;

		TransformedTable(Table<R, C, V1> fromTable, Function<? super V1, V2> function) {
			this.fromTable = checkNotNull(fromTable);
			this.function = checkNotNull(function);
		}

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

		@Override
		public V2 get(Object rowKey, Object columnKey) {
			// The function is passed a null input only when the table contains a null
			// value.
			return contains(rowKey, columnKey) ? function.apply(fromTable.get(rowKey, columnKey)) : null;
		}

		@Override
		public int size() {
			return fromTable.size();
		}

		@Override
		public void clear() {
			fromTable.clear();
		}

		@Override
		public V2 put(R rowKey, C columnKey, V2 value) {
			throw new UnsupportedOperationException();
		}

		@Override
		public void putAll(Table<? extends R, ? extends C, ? extends V2> table) {
			throw new UnsupportedOperationException();
		}

		@Override
		public V2 remove(Object rowKey, Object columnKey) {
			return contains(rowKey, columnKey) ? function.apply(fromTable.remove(rowKey, columnKey)) : null;
		}

		@Override
		public Map<C, V2> row(R rowKey) {
			return Maps.transformValues(fromTable.row(rowKey), function);
		}

		@Override
		public Map<R, V2> column(C columnKey) {
			return Maps.transformValues(fromTable.column(columnKey), function);
		}

		Function<Cell<R, C, V1>, Cell<R, C, V2>> cellFunction() {
			return new Function<Cell<R, C, V1>, Cell<R, C, V2>>() {
				@Override
				public Cell<R, C, V2> apply(Cell<R, C, V1> cell) {
					return immutableCell(cell.getRowKey(), cell.getColumnKey(), function.apply(cell.getValue()));
				}
			};
		}

		@Override
		Iterator<Cell<R, C, V2>> cellIterator() {
			return Iterators.transform(fromTable.cellSet().iterator(), cellFunction());
		}

		@Override
		public Set<R> rowKeySet() {
			return fromTable.rowKeySet();
		}

		@Override
		public Set<C> columnKeySet() {
			return fromTable.columnKeySet();
		}

		@Override
		Collection<V2> createValues() {
			return Collections2.transform(fromTable.values(), function);
		}

		@Override
		public Map<R, Map<C, V2>> rowMap() {
			Function<Map<C, V1>, Map<C, V2>> rowFunction = new Function<Map<C, V1>, Map<C, V2>>() {
				@Override
				public Map<C, V2> apply(Map<C, V1> row) {
					return Maps.transformValues(row, function);
				}
			};
			return Maps.transformValues(fromTable.rowMap(), rowFunction);
		}

		@Override
		public Map<C, Map<R, V2>> columnMap() {
			Function<Map<R, V1>, Map<R, V2>> columnFunction = new Function<Map<R, V1>, Map<R, V2>>() {
				@Override
				public Map<R, V2> apply(Map<R, V1> column) {
					return Maps.transformValues(column, function);
				}
			};
			return Maps.transformValues(fromTable.columnMap(), columnFunction);
		}
	}

	/**
	 * Returns an unmodifiable view of the specified table. This method allows
	 * modules to provide users with "read-only" access to internal tables. Query
	 * operations on the returned table "read through" to the specified table, and
	 * attempts to modify the returned table, whether direct or via its collection
	 * views, result in an {@code UnsupportedOperationException}.
	 * 
	 * <p>
	 * The returned table will be serializable if the specified table is
	 * serializable.
	 *
	 * <p>
	 * Consider using an {@link ImmutableTable}, which is guaranteed never to
	 * change.
	 * 
	 * @param table the table for which an unmodifiable view is to be returned
	 * @return an unmodifiable view of the specified table
	 * @since 11.0
	 */
	public static <R, C, V> Table<R, C, V> unmodifiableTable(Table<? extends R, ? extends C, ? extends V> table) {
		return new UnmodifiableTable<R, C, V>(table);
	}

	private static class UnmodifiableTable<R, C, V> extends ForwardingTable<R, C, V> implements Serializable {
		final Table<? extends R, ? extends C, ? extends V> delegate;

		UnmodifiableTable(Table<? extends R, ? extends C, ? extends V> delegate) {
			this.delegate = checkNotNull(delegate);
		}

		@SuppressWarnings("unchecked") // safe, covariant cast
		@Override
		protected Table<R, C, V> delegate() {
			return (Table<R, C, V>) delegate;
		}

		@Override
		public Set<Cell<R, C, V>> cellSet() {
			return Collections.unmodifiableSet(super.cellSet());
		}

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

		@Override
		public Map<R, V> column(@Nullable C columnKey) {
			return Collections.unmodifiableMap(super.column(columnKey));
		}

		@Override
		public Set<C> columnKeySet() {
			return Collections.unmodifiableSet(super.columnKeySet());
		}

		@Override
		public Map<C, Map<R, V>> columnMap() {
			Function<Map<R, V>, Map<R, V>> wrapper = unmodifiableWrapper();
			return Collections.unmodifiableMap(Maps.transformValues(super.columnMap(), wrapper));
		}

		@Override
		public V put(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
			throw new UnsupportedOperationException();
		}

		@Override
		public void putAll(Table<? extends R, ? extends C, ? extends V> table) {
			throw new UnsupportedOperationException();
		}

		@Override
		public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
			throw new UnsupportedOperationException();
		}

		@Override
		public Map<C, V> row(@Nullable R rowKey) {
			return Collections.unmodifiableMap(super.row(rowKey));
		}

		@Override
		public Set<R> rowKeySet() {
			return Collections.unmodifiableSet(super.rowKeySet());
		}

		@Override
		public Map<R, Map<C, V>> rowMap() {
			Function<Map<C, V>, Map<C, V>> wrapper = unmodifiableWrapper();
			return Collections.unmodifiableMap(Maps.transformValues(super.rowMap(), wrapper));
		}

		@Override
		public Collection<V> values() {
			return Collections.unmodifiableCollection(super.values());
		}

		private static final long serialVersionUID = 0;
	}

	/**
	 * Returns an unmodifiable view of the specified row-sorted table. This method
	 * allows modules to provide users with "read-only" access to internal tables.
	 * Query operations on the returned table "read through" to the specified table,
	 * and attemps to modify the returned table, whether direct or via its
	 * collection views, result in an {@code UnsupportedOperationException}.
	 * 
	 * <p>
	 * The returned table will be serializable if the specified table is
	 * serializable.
	 * 
	 * @param table the row-sorted table for which an unmodifiable view is to be
	 *              returned
	 * @return an unmodifiable view of the specified table
	 * @since 11.0
	 */
	@Beta
	public static <R, C, V> RowSortedTable<R, C, V> unmodifiableRowSortedTable(
			RowSortedTable<R, ? extends C, ? extends V> table) {
		/*
		 * It's not ? extends R, because it's technically not covariant in R.
		 * Specifically, table.rowMap().comparator() could return a comparator that only
		 * works for the ? extends R. Collections.unmodifiableSortedMap makes the same
		 * distinction.
		 */
		return new UnmodifiableRowSortedMap<R, C, V>(table);
	}

	static final class UnmodifiableRowSortedMap<R, C, V> extends UnmodifiableTable<R, C, V>
			implements RowSortedTable<R, C, V> {

		public UnmodifiableRowSortedMap(RowSortedTable<R, ? extends C, ? extends V> delegate) {
			super(delegate);
		}

		@Override
		protected RowSortedTable<R, C, V> delegate() {
			return (RowSortedTable<R, C, V>) super.delegate();
		}

		@Override
		public SortedMap<R, Map<C, V>> rowMap() {
			Function<Map<C, V>, Map<C, V>> wrapper = unmodifiableWrapper();
			return Collections.unmodifiableSortedMap(Maps.transformValues(delegate().rowMap(), wrapper));
		}

		@Override
		public SortedSet<R> rowKeySet() {
			return Collections.unmodifiableSortedSet(delegate().rowKeySet());
		}

		private static final long serialVersionUID = 0;
	}

	@SuppressWarnings("unchecked")
	private static <K, V> Function<Map<K, V>, Map<K, V>> unmodifiableWrapper() {
		return (Function) UNMODIFIABLE_WRAPPER;
	}

	private static final Function<? extends Map<?, ?>, ? extends Map<?, ?>> UNMODIFIABLE_WRAPPER = new Function<Map<Object, Object>, Map<Object, Object>>() {
		@Override
		public Map<Object, Object> apply(Map<Object, Object> input) {
			return Collections.unmodifiableMap(input);
		}
	};

	static boolean equalsImpl(Table<?, ?, ?> table, @Nullable Object obj) {
		if (obj == table) {
			return true;
		} else if (obj instanceof Table) {
			Table<?, ?, ?> that = (Table<?, ?, ?>) obj;
			return table.cellSet().equals(that.cellSet());
		} else {
			return false;
		}
	}
}
