/*
 * 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 java.util.LinkedHashMap;
import java.util.Map;

import javax.annotation.concurrent.Immutable;

import com.google.common.annotations.GwtCompatible;

/**
 * A {@code RegularImmutableTable} optimized for sparse data.
 */
@GwtCompatible
@Immutable
final class SparseImmutableTable<R, C, V> extends RegularImmutableTable<R, C, V> {

	private final ImmutableMap<R, Map<C, V>> rowMap;
	private final ImmutableMap<C, Map<R, V>> columnMap;
	private final int[] iterationOrderRow;
	private final int[] iterationOrderColumn;

	SparseImmutableTable(ImmutableList<Cell<R, C, V>> cellList, ImmutableSet<R> rowSpace, ImmutableSet<C> columnSpace) {
		Map<R, Integer> rowIndex = Maps.newHashMap();
		Map<R, Map<C, V>> rows = Maps.newLinkedHashMap();
		for (R row : rowSpace) {
			rowIndex.put(row, rows.size());
			rows.put(row, new LinkedHashMap<C, V>());
		}
		Map<C, Map<R, V>> columns = Maps.newLinkedHashMap();
		for (C col : columnSpace) {
			columns.put(col, new LinkedHashMap<R, V>());
		}
		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();
			V value = cell.getValue();

			iterationOrderRow[i] = rowIndex.get(rowKey);
			Map<C, V> thisRow = rows.get(rowKey);
			iterationOrderColumn[i] = thisRow.size();
			V oldValue = thisRow.put(columnKey, value);
			if (oldValue != null) {
				throw new IllegalArgumentException(
						"Duplicate value for row=" + rowKey + ", column=" + columnKey + ": " + value + ", " + oldValue);
			}
			columns.get(columnKey).put(rowKey, value);
		}
		this.iterationOrderRow = iterationOrderRow;
		this.iterationOrderColumn = iterationOrderColumn;
		ImmutableMap.Builder<R, Map<C, V>> rowBuilder = ImmutableMap.builder();
		for (Map.Entry<R, Map<C, V>> row : rows.entrySet()) {
			rowBuilder.put(row.getKey(), ImmutableMap.copyOf(row.getValue()));
		}
		this.rowMap = rowBuilder.build();

		ImmutableMap.Builder<C, Map<R, V>> columnBuilder = ImmutableMap.builder();
		for (Map.Entry<C, Map<R, V>> col : columns.entrySet()) {
			columnBuilder.put(col.getKey(), ImmutableMap.copyOf(col.getValue()));
		}
		this.columnMap = columnBuilder.build();
	}

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

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

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

	@Override
	Cell<R, C, V> getCell(int index) {
		int rowIndex = iterationOrderRow[index];
		Map.Entry<R, Map<C, V>> rowEntry = rowMap.entrySet().asList().get(rowIndex);
		ImmutableMap<C, V> row = (ImmutableMap<C, V>) rowEntry.getValue();
		int columnIndex = iterationOrderColumn[index];
		Map.Entry<C, V> colEntry = row.entrySet().asList().get(columnIndex);
		return cellOf(rowEntry.getKey(), colEntry.getKey(), colEntry.getValue());
	}

	@Override
	V getValue(int index) {
		int rowIndex = iterationOrderRow[index];
		ImmutableMap<C, V> row = (ImmutableMap<C, V>) rowMap.values().asList().get(rowIndex);
		int columnIndex = iterationOrderColumn[index];
		return row.values().asList().get(columnIndex);
	}
}