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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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.hazelcast.org.apache.calcite.util.mapping;

import com.hazelcast.org.apache.calcite.runtime.Utilities;

import com.hazelcast.com.google.common.base.Function;
import com.hazelcast.com.google.common.collect.Lists;
import com.hazelcast.com.google.common.collect.Ordering;

import java.util.AbstractList;
import java.util.Comparator;
import java.util.List;

/**
 * An immutable pair of integers.
 *
 * @see Mapping#iterator()
 */
public class IntPair {
  /** Function that swaps source and target fields of an {@link IntPair}. */
  public static final Function SWAP =
      new Function() {
        public IntPair apply(IntPair pair) {
          return of(pair.target, pair.source);
        }
      };

  /** Ordering that compares pairs lexicographically: first by their source,
   * then by their target. */
  public static final Ordering ORDERING =
      Ordering.from(
          new Comparator() {
            public int compare(IntPair o1, IntPair o2) {
              int c = Integer.compare(o1.source, o2.source);
              if (c == 0) {
                c = Integer.compare(o1.target, o2.target);
              }
              return c;
            }
          });

  /** Function that returns the left (source) side of a pair. */
  public static final Function LEFT =
      new Function() {
        public Integer apply(IntPair pair) {
          return pair.source;
        }
      };

  /** Function that returns the right (target) side of a pair. */
  public static final Function RIGHT =
      new Function() {
        public Integer apply(IntPair pair) {
          return pair.target;
        }
      };

  //~ Instance fields --------------------------------------------------------

  public final int source;
  public final int target;

  //~ Constructors -----------------------------------------------------------

  public IntPair(int source, int target) {
    this.source = source;
    this.target = target;
  }

  //~ Methods ----------------------------------------------------------------

  public static IntPair of(int left, int right) {
    return new IntPair(left, right);
  }

  public String toString() {
    return source + "-" + target;
  }

  public boolean equals(Object obj) {
    if (obj instanceof IntPair) {
      IntPair that = (IntPair) obj;
      return (this.source == that.source) && (this.target == that.target);
    }
    return false;
  }

  public int hashCode() {
    return Utilities.hash(source, target);
  }

  /**
   * Converts two lists into a list of {@link IntPair}s,
   * whose length is the lesser of the lengths of the
   * source lists.
   *
   * @param lefts Left list
   * @param rights Right list
   * @return List of pairs
   */
  public static List zip(List lefts,
      List rights) {
    return zip(lefts, rights, false);
  }

  /**
   * Converts two lists into a list of {@link IntPair}s.
   *
   * The length of the combined list is the lesser of the lengths of the
   * source lists. But typically the source lists will be the same length.
   *
   * @param lefts Left list
   * @param rights Right list
   * @param strict Whether to fail if lists have different size
   * @return List of pairs
   */
  public static List zip(
      final List lefts,
      final List rights,
      boolean strict) {
    final int size;
    if (strict) {
      if (lefts.size() != rights.size()) {
        throw new AssertionError();
      }
      size = lefts.size();
    } else {
      size = Math.min(lefts.size(), rights.size());
    }
    return new AbstractList() {
      public IntPair get(int index) {
        return IntPair.of(lefts.get(index).intValue(),
            rights.get(index).intValue());
      }

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

  /** Returns the left side of a list of pairs. */
  public static List left(final List pairs) {
    return Lists.transform(pairs, LEFT);
  }

  /** Returns the right side of a list of pairs. */
  public static List right(final List pairs) {
    return Lists.transform(pairs, RIGHT);
  }
}