/*
 * 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.checkArgument;

import java.util.Map;

import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

import com.google.common.annotations.GwtCompatible;

/**
 * A {@code RegularImmutableTable} optimized for dense data.
 */
@GwtCompatible
@Immutable
final class DenseImmutableTable<R, C, V> extends RegularImmutableTable<R, C, V> {
	private final class Column extends ImmutableArrayMap<R, V> {
		private final int columnIndex;

		Column(int columnIndex) {
			super(columnCounts[columnIndex]);
			this.columnIndex = columnIndex;
		}

		@Override
		V getValue(int keyIndex) {
			return values[keyIndex][columnIndex];
		}

		@Override
		boolean isPartialView() {
			return true;
		}

		@Override
		ImmutableMap<R, Integer> keyToIndex() {
			return rowKeyToIndex;
		}
	}

	private final class ColumnMap extends ImmutableArrayMap<C, Map<R, V>> {
		private ColumnMap() {
			super(columnCounts.length);
		}

		@Override
		Map<R, V> getValue(int keyIndex) {
			return new Column(keyIndex);
		}

		@Override
		boolean isPartialView() {
			return false;
		}

		@Override
		ImmutableMap<C, Integer> keyToIndex() {
			return columnKeyToIndex;
		}
	}

	/**
	 * An immutable map implementation backed by an indexed nullable array.
	 */
	private abstract static class ImmutableArrayMap<K, V> extends ImmutableMap<K, V> {
		private final int size;

		ImmutableArrayMap(int size) {
			this.size = size;
		}

		@Override
		ImmutableSet<Entry<K, V>> createEntrySet() {
			return new ImmutableMapEntrySet<K, V>() {
				@Override
				public UnmodifiableIterator<Entry<K, V>> iterator() {
					return new AbstractIterator<Entry<K, V>>() {
						private int index = -1;
						private final int maxIndex = keyToIndex().size();

						@Override
						protected Entry<K, V> computeNext() {
							for (index++; index < maxIndex; index++) {
								V value = getValue(index);
								if (value != null) {
									return Maps.immutableEntry(getKey(index), value);
								}
							}
							return endOfData();
						}
					};
				}

				@Override
				ImmutableMap<K, V> map() {
					return ImmutableArrayMap.this;
				}
			};
		}

		@Override
		ImmutableSet<K> createKeySet() {
			return isFull() ? keyToIndex().keySet() : super.createKeySet();
		}

		@Override
		public V get(@Nullable Object key) {
			Integer keyIndex = keyToIndex().get(key);
			return (keyIndex == null) ? null : getValue(keyIndex);
		}

		K getKey(int index) {
			return keyToIndex().keySet().asList().get(index);
		}

		@Nullable
		abstract V getValue(int keyIndex);

		// True if getValue never returns null.
		private boolean isFull() {
			return size == keyToIndex().size();
		}

		abstract ImmutableMap<K, Integer> keyToIndex();

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

	private final class Row extends ImmutableArrayMap<C, V> {
		private final int rowIndex;

		Row(int rowIndex) {
			super(rowCounts[rowIndex]);
			this.rowIndex = rowIndex;
		}

		@Override
		V getValue(int keyIndex) {
			return values[rowIndex][keyIndex];
		}

		@Override
		boolean isPartialView() {
			return true;
		}

		@Override
		ImmutableMap<C, Integer> keyToIndex() {
			return columnKeyToIndex;
		}
	}

	private final class RowMap extends ImmutableArrayMap<R, Map<C, V>> {
		private RowMap() {
			super(rowCounts.length);
		}

		@Override
		Map<C, V> getValue(int keyIndex) {
			return new Row(keyIndex);
		}

		@Override
		boolean isPartialView() {
			return false;
		}

		@Override
		ImmutableMap<R, Integer> keyToIndex() {
			return rowKeyToIndex;
		}
	}

	private static <E> ImmutableMap<E, Integer> makeIndex(ImmutableSet<E> set) {
		ImmutableMap.Builder<E, Integer> indexBuilder = ImmutableMap.builder();
		int i = 0;
		for (E key : set) {
			indexBuilder.put(key, i);
			i++;
		}
		return indexBuilder.build();
	}

	private final ImmutableMap<R, Integer> rowKeyToIndex;
	private final ImmutableMap<C, Integer> columnKeyToIndex;
	private final ImmutableMap<R, Map<C, V>> rowMap;

	private final ImmutableMap<C, Map<R, V>> columnMap;

	private final int[] rowCounts;

	private final int[] columnCounts;

	private final V[][] values;

	private final int[] iterationOrderRow;

	private final int[] iterationOrderColumn;

	DenseImmutableTable(ImmutableList<Cell<R, C, V>> cellList, ImmutableSet<R> rowSpace, ImmutableSet<C> columnSpace) {
		@SuppressWarnings("unchecked")
		V[][] array = (V[][]) new Object[rowSpace.size()][columnSpace.size()];
		this.values = array;
		this.rowKeyToIndex = makeIndex(rowSpace);
		this.columnKeyToIndex = makeIndex(columnSpace);
		rowCounts = new int[rowKeyToIndex.size()];
		columnCounts = new int[columnKeyToIndex.size()];
		int[] iterationOrderRow = new int[cellList.size()];
		int[] iterationOrderColumn = new int[cellList.size()];
		for (int i = 0; i < cellList.size(); i++) {
			Cell<R, C, V> cell = cellList.get(i);
			R rowKey = cell.getRowKey();
			C columnKey = cell.getColumnKey();
			int rowIndex = rowKeyToIndex.get(rowKey);
			int columnIndex = columnKeyToIndex.get(columnKey);
			V existingValue = values[rowIndex][columnIndex];
			checkArgument(existingValue == null, "duplicate key: (%s, %s)", rowKey, columnKey);
			values[rowIndex][columnIndex] = cell.getValue();
			rowCounts[rowIndex]++;
			columnCounts[columnIndex]++;
			iterationOrderRow[i] = rowIndex;
			iterationOrderColumn[i] = columnIndex;
		}
		this.iterationOrderRow = iterationOrderRow;
		this.iterationOrderColumn = iterationOrderColumn;
		this.rowMap = new RowMap();
		this.columnMap = new ColumnMap();
	}

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

	@Override
	public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
		Integer rowIndex = rowKeyToIndex.get(rowKey);
		Integer columnIndex = columnKeyToIndex.get(columnKey);
		return ((rowIndex == null) || (columnIndex == null)) ? null : values[rowIndex][columnIndex];
	}

	@Override
	Cell<R, C, V> getCell(int index) {
		int rowIndex = iterationOrderRow[index];
		int columnIndex = iterationOrderColumn[index];
		R rowKey = rowKeySet().asList().get(rowIndex);
		C columnKey = columnKeySet().asList().get(columnIndex);
		V value = values[rowIndex][columnIndex];
		return cellOf(rowKey, columnKey, value);
	}

	@Override
	V getValue(int index) {
		return values[iterationOrderRow[index]][iterationOrderColumn[index]];
	}

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

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