/*
 * Copyright (C) 2009 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.checkNotNull;

import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.annotation.Nullable;

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

/**
 * An immutable {@link Table} with reliable user-specified iteration order. Does
 * not permit null keys or values.
 *
 * <p>
 * <b>Note</b>: Although this class is not final, it cannot be subclassed as it
 * has no public or protected constructors. Thus, instances of this class are
 * guaranteed to be immutable.
 *
 * <p>
 * See the Guava User Guide article on <a href=
 * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
 * immutable collections</a>.
 *
 * @author Gregory Kick
 * @since 11.0
 */
@GwtCompatible
// TODO(gak): make serializable
public abstract class ImmutableTable<R, C, V> extends AbstractTable<R, C, V> {
	private static final ImmutableTable<Object, Object, Object> EMPTY = new SparseImmutableTable<Object, Object, Object>(
			ImmutableList.<Cell<Object, Object, Object>>of(), ImmutableSet.of(), ImmutableSet.of());

	/** Returns an empty immutable table. */
	@SuppressWarnings("unchecked")
	public static <R, C, V> ImmutableTable<R, C, V> of() {
		return (ImmutableTable<R, C, V>) EMPTY;
	}

	/** Returns an immutable table containing a single cell. */
	public static <R, C, V> ImmutableTable<R, C, V> of(R rowKey, C columnKey, V value) {
		return new SingletonImmutableTable<R, C, V>(rowKey, columnKey, value);
	}

	/**
	 * Returns an immutable copy of the provided table.
	 *
	 * <p>
	 * The {@link Table#cellSet()} iteration order of the provided table determines
	 * the iteration ordering of all views in the returned table. Note that some
	 * views of the original table and the copied table may have different iteration
	 * orders. For more control over the ordering, create a {@link Builder} and call
	 * {@link Builder#orderRowsBy}, {@link Builder#orderColumnsBy}, and
	 * {@link Builder#putAll}
	 *
	 * <p>
	 * Despite the method name, this method attempts to avoid actually copying the
	 * data when it is safe to do so. The exact circumstances under which a copy
	 * will or will not be performed are undocumented and subject to change.
	 */
	public static <R, C, V> ImmutableTable<R, C, V> copyOf(Table<? extends R, ? extends C, ? extends V> table) {
		if (table instanceof ImmutableTable) {
			@SuppressWarnings("unchecked")
			ImmutableTable<R, C, V> parameterizedTable = (ImmutableTable<R, C, V>) table;
			return parameterizedTable;
		} else {
			int size = table.size();
			switch (size) {
			case 0:
				return of();
			case 1:
				Cell<? extends R, ? extends C, ? extends V> onlyCell = Iterables.getOnlyElement(table.cellSet());
				return ImmutableTable.<R, C, V>of(onlyCell.getRowKey(), onlyCell.getColumnKey(), onlyCell.getValue());
			default:
				ImmutableSet.Builder<Cell<R, C, V>> cellSetBuilder = ImmutableSet.builder();
				for (Cell<? extends R, ? extends C, ? extends V> cell : table.cellSet()) {
					/*
					 * Must cast to be able to create a Cell<R, C, V> rather than a Cell<? extends
					 * R, ? extends C, ? extends V>
					 */
					cellSetBuilder.add(cellOf((R) cell.getRowKey(), (C) cell.getColumnKey(), (V) cell.getValue()));
				}
				return RegularImmutableTable.forCells(cellSetBuilder.build());
			}
		}
	}

	/**
	 * Returns a new builder. The generated builder is equivalent to the builder
	 * created by the {@link Builder#ImmutableTable.Builder()} constructor.
	 */
	public static <R, C, V> Builder<R, C, V> builder() {
		return new Builder<R, C, V>();
	}

	/**
	 * Verifies that {@code rowKey}, {@code columnKey} and {@code value} are
	 * non-null, and returns a new entry with those values.
	 */
	static <R, C, V> Cell<R, C, V> cellOf(R rowKey, C columnKey, V value) {
		return Tables.immutableCell(checkNotNull(rowKey), checkNotNull(columnKey), checkNotNull(value));
	}

	/**
	 * A builder for creating immutable table instances, especially {@code public
	 * static final} tables ("constant tables"). Example:
	 * 
	 * <pre>
	 * {
	 * 	&#64;code
	 *
	 * 	static final ImmutableTable<Integer, Character, String> SPREADSHEET = new ImmutableTable.Builder<Integer, Character, String>()
	 * 			.put(1, 'A', "foo").put(1, 'B', "bar").put(2, 'A', "baz").build();
	 * }
	 * </pre>
	 *
	 * <p>
	 * By default, the order in which cells are added to the builder determines the
	 * iteration ordering of all views in the returned table, with {@link #putAll}
	 * following the {@link Table#cellSet()} iteration order. However, if
	 * {@link #orderRowsBy} or {@link #orderColumnsBy} is called, the views are
	 * sorted by the supplied comparators.
	 *
	 * For empty or single-cell immutable tables, {@link #of()} and
	 * {@link #of(Object, Object, Object)} are even more convenient.
	 *
	 * <p>
	 * Builder instances can be reused - it is safe to call {@link #build} multiple
	 * times to build multiple tables in series. Each table is a superset of the
	 * tables created before it.
	 *
	 * @since 11.0
	 */
	public static final class Builder<R, C, V> {
		private final List<Cell<R, C, V>> cells = Lists.newArrayList();
		private Comparator<? super R> rowComparator;
		private Comparator<? super C> columnComparator;

		/**
		 * Creates a new builder. The returned builder is equivalent to the builder
		 * generated by {@link ImmutableTable#builder}.
		 */
		public Builder() {
		}

		/**
		 * Specifies the ordering of the generated table's rows.
		 */
		public Builder<R, C, V> orderRowsBy(Comparator<? super R> rowComparator) {
			this.rowComparator = checkNotNull(rowComparator);
			return this;
		}

		/**
		 * Specifies the ordering of the generated table's columns.
		 */
		public Builder<R, C, V> orderColumnsBy(Comparator<? super C> columnComparator) {
			this.columnComparator = checkNotNull(columnComparator);
			return this;
		}

		/**
		 * Associates the ({@code rowKey}, {@code columnKey}) pair with {@code
		 * value} in the built table. Duplicate key pairs are not allowed and will cause
		 * {@link #build} to fail.
		 */
		public Builder<R, C, V> put(R rowKey, C columnKey, V value) {
			cells.add(cellOf(rowKey, columnKey, value));
			return this;
		}

		/**
		 * Adds the given {@code cell} to the table, making it immutable if necessary.
		 * Duplicate key pairs are not allowed and will cause {@link #build} to fail.
		 */
		public Builder<R, C, V> put(Cell<? extends R, ? extends C, ? extends V> cell) {
			if (cell instanceof Tables.ImmutableCell) {
				checkNotNull(cell.getRowKey());
				checkNotNull(cell.getColumnKey());
				checkNotNull(cell.getValue());
				@SuppressWarnings("unchecked") // all supported methods are covariant
				Cell<R, C, V> immutableCell = (Cell<R, C, V>) cell;
				cells.add(immutableCell);
			} else {
				put(cell.getRowKey(), cell.getColumnKey(), cell.getValue());
			}
			return this;
		}

		/**
		 * Associates all of the given table's keys and values in the built table.
		 * Duplicate row key column key pairs are not allowed, and will cause
		 * {@link #build} to fail.
		 *
		 * @throws NullPointerException if any key or value in {@code table} is null
		 */
		public Builder<R, C, V> putAll(Table<? extends R, ? extends C, ? extends V> table) {
			for (Cell<? extends R, ? extends C, ? extends V> cell : table.cellSet()) {
				put(cell);
			}
			return this;
		}

		/**
		 * Returns a newly-created immutable table.
		 *
		 * @throws IllegalArgumentException if duplicate key pairs were added
		 */
		public ImmutableTable<R, C, V> build() {
			int size = cells.size();
			switch (size) {
			case 0:
				return of();
			case 1:
				return new SingletonImmutableTable<R, C, V>(Iterables.getOnlyElement(cells));
			default:
				return RegularImmutableTable.forCells(cells, rowComparator, columnComparator);
			}
		}
	}

	ImmutableTable() {
	}

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

	@Override
	abstract ImmutableSet<Cell<R, C, V>> createCellSet();

	@Override
	final UnmodifiableIterator<Cell<R, C, V>> cellIterator() {
		throw new AssertionError("should never be called");
	}

	@Override
	public ImmutableCollection<V> values() {
		return (ImmutableCollection<V>) super.values();
	}

	@Override
	abstract ImmutableCollection<V> createValues();

	@Override
	final Iterator<V> valuesIterator() {
		throw new AssertionError("should never be called");
	}

	/**
	 * {@inheritDoc}
	 *
	 * @throws NullPointerException if {@code columnKey} is {@code null}
	 */
	@Override
	public ImmutableMap<R, V> column(C columnKey) {
		checkNotNull(columnKey);
		return Objects.firstNonNull((ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.<R, V>of());
	}

	@Override
	public ImmutableSet<C> columnKeySet() {
		return columnMap().keySet();
	}

	/**
	 * {@inheritDoc}
	 *
	 * <p>
	 * The value {@code Map<R, V>} instances in the returned map are
	 * {@link ImmutableMap} instances as well.
	 */
	@Override
	public abstract ImmutableMap<C, Map<R, V>> columnMap();

	/**
	 * {@inheritDoc}
	 *
	 * @throws NullPointerException if {@code rowKey} is {@code null}
	 */
	@Override
	public ImmutableMap<C, V> row(R rowKey) {
		checkNotNull(rowKey);
		return Objects.firstNonNull((ImmutableMap<C, V>) rowMap().get(rowKey), ImmutableMap.<C, V>of());
	}

	@Override
	public ImmutableSet<R> rowKeySet() {
		return rowMap().keySet();
	}

	/**
	 * {@inheritDoc}
	 *
	 * <p>
	 * The value {@code Map<C, V>} instances in the returned map are
	 * {@link ImmutableMap} instances as well.
	 */
	@Override
	public abstract ImmutableMap<R, Map<C, V>> rowMap();

	@Override
	public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
		return get(rowKey, columnKey) != null;
	}

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

	/**
	 * Guaranteed to throw an exception and leave the table unmodified.
	 *
	 * @throws UnsupportedOperationException always
	 * @deprecated Unsupported operation.
	 */
	@Deprecated
	@Override
	public final void clear() {
		throw new UnsupportedOperationException();
	}

	/**
	 * Guaranteed to throw an exception and leave the table unmodified.
	 *
	 * @throws UnsupportedOperationException always
	 * @deprecated Unsupported operation.
	 */
	@Deprecated
	@Override
	public final V put(R rowKey, C columnKey, V value) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Guaranteed to throw an exception and leave the table unmodified.
	 *
	 * @throws UnsupportedOperationException always
	 * @deprecated Unsupported operation.
	 */
	@Deprecated
	@Override
	public final void putAll(Table<? extends R, ? extends C, ? extends V> table) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Guaranteed to throw an exception and leave the table unmodified.
	 *
	 * @throws UnsupportedOperationException always
	 * @deprecated Unsupported operation.
	 */
	@Deprecated
	@Override
	public final V remove(Object rowKey, Object columnKey) {
		throw new UnsupportedOperationException();
	}
}
