/*
    * 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.commons.jexl3.internal;
  
  import java.lang.reflect.Array;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  /**
   * An ascending iterator on an integer range.
   */
  final class AscIntegerIterator implements Iterator<Integer> {
      /** The lower boundary. */
      private final int min;
      /** The upper boundary. */
      private final int max;
      /** The current value. */
      private int cursor;
      /**
       * Creates a iterator on the range.
       * @param l low boundary
       * @param h high boundary
       */
      public AscIntegerIterator(final int l, final int h) {
          min = l;
          max = h;
          cursor = min;
      }
  
      @Override
      public boolean hasNext() {
          return cursor <= max;
      }
  
      @Override
      public Integer next() {
          if (cursor <= max) {
              return cursor++;
          }
          throw new NoSuchElementException();
      }
  }
  
  /**
   * A descending iterator on an integer range.
   */
  final class DescIntegerIterator implements Iterator<Integer> {
      /** The lower boundary. */
      private final int min;
      /** The upper boundary. */
      private final int max;
      /** The current value. */
      private int cursor;
      /**
       * Creates a iterator on the range.
       * @param l low boundary
       * @param h high boundary
       */
      public DescIntegerIterator(final int l, final int h) {
          min = l;
          max = h;
          cursor = max;
      }
  
      @Override
      public boolean hasNext() {
          return cursor >= min;
      }
  
      @Override
      public Integer next() {
          if (cursor >= min) {
              return cursor--;
          }
          throw new NoSuchElementException();
      }
  }
  
  /**
   * A range of integers.
   */
  public abstract class IntegerRange implements Collection<Integer> {
      /**
       * Ascending integer range.
      */
     public static class Ascending extends IntegerRange {
         /**
          * Constructs a new instance.
          * @param from lower boundary
          * @param to upper boundary
          */
         protected Ascending(final int from, final int to) {
             super(from, to);
         }
 
         @Override
         public Iterator<Integer> iterator() {
             return new AscIntegerIterator(min, max);
         }
     }
     /**
      * Descending integer range.
      */
     public static class Descending extends IntegerRange {
         /**
          * Constructs a new instance.
          * @param from upper boundary
          * @param to lower boundary
          */
         protected Descending(final int from, final int to) {
             super(from, to);
         }
 
         @Override
         public Iterator<Integer> iterator() {
             return new DescIntegerIterator(min, max);
         }
     }
 
     /**
      * Creates a range, ascending or descending depending on boundaries order.
      * @param from the lower inclusive boundary
      * @param to   the higher inclusive boundary
      * @return a range
      */
     public static IntegerRange create(final int from, final int to) {
         if (from <= to) {
             return new IntegerRange.Ascending(from, to);
         }
         return new IntegerRange.Descending(to, from);
     }
     /** The lower boundary. */
     protected final int min;
 
     /** The upper boundary. */
     protected final int max;
 
     /**
      * Creates a new range.
      * @param from the lower inclusive boundary
      * @param to  the higher inclusive boundary
      */
     public IntegerRange(final int from, final int to) {
         min = from;
         max = to;
     }
 
     @Override
     public boolean add(final Integer e) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean addAll(final Collection<? extends Integer> c) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void clear() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean contains(final Object o) {
         if (o instanceof Number) {
             final long v = ((Number) o).intValue();
             return min <= v && v <= max;
         }
         return false;
     }
 
     @Override
     public boolean containsAll(final Collection<?> c) {
         for(final Object cc : c) {
             if (!contains(cc)) {
                 return false;
             }
         }
         return true;
     }
 
     @Override
     public boolean equals(final Object obj) {
         if (obj == null) {
             return false;
         }
         if (getClass() != obj.getClass()) {
             return false;
         }
         final IntegerRange other = (IntegerRange) obj;
         if (this.min != other.min) {
             return false;
         }
         if (this.max != other.max) {
             return false;
         }
         return true;
     }
 
     /**
      * Gets the interval maximum value.
      * @return the high boundary
      */
     public int getMax() {
         return max;
     }
 
     /**
      * Gets the interval minimum value.
      * @return the low boundary
      */
     public int getMin() {
         return min;
     }
 
     @Override
     public int hashCode() {
         int hash = getClass().hashCode();
         //CSOFF: MagicNumber
         hash = 13 * hash + this.min;
         hash = 13 * hash + this.max;
         //CSON: MagicNumber
         return hash;
     }
 
     @Override
     public boolean isEmpty() {
         return false;
     }
 
     @Override
     public abstract Iterator<Integer> iterator();
 
     @Override
     public boolean remove(final Object o) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean removeAll(final Collection<?> c) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean retainAll(final Collection<?> c) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public int size() {
         return max - min + 1;
     }
 
     @Override
     public Object[] toArray() {
         final int size = size();
         final Object[] array = new Object[size];
         for(int a = 0; a < size; ++a) {
             array[a] = min + a;
         }
         return array;
     }
 
     @Override
     @SuppressWarnings("unchecked")
     public <T> T[] toArray(final T[] array) {
         final Class<?> ct = array.getClass().getComponentType();
         final int length = size();
         T[] copy = array;
         if (ct.isAssignableFrom(Integer.class)) {
             if (array.length < length) {
                 copy = (T[]) Array.newInstance(ct, length);
             }
             for (int a = 0; a < length; ++a) {
                 Array.set(copy, a, min + a);
             }
             if (length < copy.length) {
                 copy[length] = null;
             }
             return copy;
         }
         throw new UnsupportedOperationException();
     }
 }