content: /*
   * 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 org.apache.kafka.coordinator.group.assignor;
  
  import java.lang.reflect.Array;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  import java.util.Set;
  
  /**
   * A {@code RangeSet} represents a range of integers from {@code from} (inclusive)
   * to {@code to} (exclusive).
   * This implementation provides a view over a continuous range of integers without actually storing them.
   */
  class RangeSet implements Set<Integer> {
      private final int from;
      private final int to;
  
      /**
       * Constructs a {@code RangeSet} with the specified range.
       *
       * @param from      The starting value (inclusive) of the range.
       * @param to        The ending value (exclusive) of the range.
       */
      public RangeSet(int from, int to) {
          this.from = from;
          this.to = to;
  
          if (to < from) {
              throw new IllegalArgumentException("Invalid range: to must be greater than or equal to from");
          }
  
          if ((long) to - (long) from > Integer.MAX_VALUE) {
              throw new IllegalArgumentException("Range exceeds the maximum size of Integer.MAX_VALUE");
          }
      }
  
      @Override
      public int size() {
          return to - from;
      }
  
      @Override
      public boolean isEmpty() {
          return size() == 0;
      }
  
      @Override
      public boolean contains(Object o) {
          if (o instanceof Integer) {
              int value = (Integer) o;
              return value >= from && value < to;
          }
          return false;
      }
  
      @Override
      public Iterator<Integer> iterator() {
          return new Iterator<>() {
              private int current = from;
  
              @Override
              public boolean hasNext() {
                  return current < to;
              }
  
              @Override
              public Integer next() {
                  if (!hasNext()) throw new NoSuchElementException();
                  return current++;
              }
          };
      }
  
      @Override
      public Object[] toArray() {
          Object[] array = new Object[size()];
          for (int i = 0; i < size(); i++) {
              array[i] = from + i;
          }
          return array;
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public <T> T[] toArray(T[] a) {
          int size = size();
          if (a.length < size) {
              // Create a new array of the same type as a with the correct size
              a = (T[]) Array.newInstance(a.getClass().getComponentType(), size);
          }
          for (int i = 0; i < size; i++) {
              a[i] = (T) Integer.valueOf(from + i);
          }
          if (a.length > size) {
              a[size] = null;
          }
          return a;
      }
  
      @Override
      public boolean add(Integer integer) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean remove(Object o) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean containsAll(Collection<?> c) {
          for (Object o : c) {
              if (!contains(o)) return false;
          }
          return true;
      }
  
      @Override
      public boolean addAll(Collection<? extends Integer> c) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean retainAll(Collection<?> c) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean removeAll(Collection<?> c) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public void clear() {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public String toString() {
          return "RangeSet(from=" + from + " (inclusive), to=" + to + " (exclusive))";
      }
  
      /**
       * Compares the specified object with this set for equality.
       * Returns {@code true} if the specified object is also a set,
       * the two sets have the same size, and every member of the specified
       * set is contained in this set.
       *
       * @param o object to be compared for equality with this set
       * @return {@code true} if the specified object is equal to this set
       */
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (!(o instanceof Set<?> otherSet)) return false;
  
          if (o instanceof RangeSet other) {
              if (this.size() == 0 && other.size() == 0) return true;
              return this.from == other.from && this.to == other.to;
          }
  
          if (otherSet.size() != this.size()) return false;
  
          for (int i = from; i < to; i++) {
              if (!otherSet.contains(i)) return false;
          }
          return true;
      }
  
      @Override
      public int hashCode() {
          // The hash code of a Set is defined as the sum of the hash codes of its elements.
          // The hash code of an integer is the integer itself.
  
          // The sum of the integers from 1 to n is n * (n + 1) / 2.
          // To get the sum of the integers from 1 + k to n + k, we can add n * k.
          // So our hash code comes out to n * (from + to - 1) / 2.
  
          // The arithmetic has to be done using longs, since the division by 2 is equivalent to
          // shifting the 33rd bit right.
          long sum = size() * ((long) from + (long) to - 1) / 2;
          return (int) sum;
      }
  }
  