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.causeway.commons.internal.collections;
  
  import java.util.Arrays;
  import java.util.Iterator;
  import java.util.OptionalInt;
  import java.util.PrimitiveIterator;
  import java.util.stream.IntStream;
  
  import org.jspecify.annotations.Nullable;
  
  import org.apache.causeway.commons.internal.base._NullSafe;
  
  import lombok.NoArgsConstructor;
  import lombok.experimental.UtilityClass;
  
  /**
   * <h1>- internal use only -</h1>
   * Utility class providing some primitive collections.
   * <p>
   * <b>WARNING</b>: Do <b>NOT</b> use any of the classes provided by this package! <br/>
   * These may be changed or removed without notice!
   *
   * @since 2.0
   */
  @UtilityClass
  public class _PrimitiveCollections {
  
      /**
       * Primitive int list implementation. Can also operate as a set,
       * if {@link IntList#addUnique(int)} (and variants) are used instead of {@link IntList#add(int)}.
       * @implNote not thread-safe
       */
      @NoArgsConstructor
      public static class IntList implements Iterable<Integer> {
          private static final int DEFAULT_INITIAL_CAPACITY = 8;
  
          // -- CONSTRUCTION
  
          private int[] buf;
          private int size = 0;
  
          public IntList(final int initialCapacity) {
              if(initialCapacity<0) {
                  throw new IndexOutOfBoundsException(initialCapacity);
              }
              this.buf = initialCapacity == 0
                      ? null // otherwise cannot use buffer doubling algorithm below, when adding
                      : new int[initialCapacity];
          }
  
          public IntList(final @Nullable int[] array) {
              this.size = _NullSafe.size(array);
              if(size == 0) {
                  // don't init buf to 0 size, otherwise cannot use buffer doubling algorithm below, when adding
                  return;
              }
              this.buf = new int[size];
              System.arraycopy(array, 0, buf, 0, size);
          }
  
          // -- SIZE
  
          public int size() {
              return size;
          }
  
          public boolean isEmpty() {
              return size==0;
          }
          public boolean isNotEmpty() {
              return size!=0;
          }
  
          // -- ADDING
  
          public IntList add(final int v) {
              if(buf==null) {
                  this.buf = new int[DEFAULT_INITIAL_CAPACITY];
              } else if(size==buf.length) {
                  var old = buf;
                  this.buf = new int[buf.length * 2];
                  System.arraycopy(old, 0, buf, 0, size);
              }
              buf[size++] = v;
              return this;
          }
  
          //TODO should perhaps return some feedback, as to whether v was added or not
          public IntList addUnique(final int v) {
              if(!contains(v)) return add(v);
              return this;
          }
  
          public IntList addAll(final @Nullable int[] array) {
              final int n = _NullSafe.size(array);
              if(n!=0) {
                  var old = buf;
                  this.buf = new int[size + n];
                  System.arraycopy(old, 0, buf, 0, size);
                  System.arraycopy(array, 0, buf, size, n);
                  this.size += n;
              }
              return this;
          }
  
          public IntList addAllUnique(final @Nullable int[] array) {
              final int n = _NullSafe.size(array);
              if(n!=0) {
                  for (int v : array) {
                      addUnique(v);
                  }
              }
              return this;
          }
  
          // -- QUERIES
  
          public int get(final int index) {
              if(index<0
                      || index>=size) {
                  throw new IndexOutOfBoundsException(index);
              }
              return buf[index];
          }
  
          public OptionalInt indexOf(final int v) {
              if(isEmpty()) return OptionalInt.empty();
              for (int i = 0; i < size; i++) {
                  if(buf[i]==v) return OptionalInt.of(i);
              }
              return OptionalInt.empty();
          }
  
          public boolean contains(final int v) {
              if(isEmpty()) return false;
              for (int i = 0; i < size; i++) {
                  if(buf[i]==v) return true;
              }
              return false;
          }
  
          // -- PICKING
  
          /**
           * Ignores out of bounds picks.
           */
          public int[] toArrayPickByIndex(final @Nullable int... indexes) {
              final int n = _NullSafe.size(indexes);
              if(n==0) return new int[0];
  
              var newElements = new int[n];
              final int maxIndex = size()-1;
              int elementCount = 0;
              for(int index : indexes) {
                  if(index>=0
                          && index<=maxIndex) {
                      newElements[elementCount++] = buf[index];
                  }
              }
              return elementCount == n
                      ? newElements
                      : Arrays.copyOf(newElements, elementCount); // trim to actual size
          }
  
          // -- CONVERSION
  
          /**
           * Returns a new array containing all the int(s) of this list.
           * @return non-null
           */
          public int[] toArray() {
              var result = new int[size];
              if(!isEmpty()) {
                  System.arraycopy(buf, 0, result, 0, size);
              }
              return result;
          }
  
          // -- TRAVERSAL
  
          public IntStream stream() {
              return IntStream.of(toArray());
          }
  
          @Override
          public Iterator<Integer> iterator() {
              var defensiveCopy = toArray();
              return new PrimitiveIterator.OfInt() {
                  int index = 0;
                  @Override public boolean hasNext() {
                      return index<defensiveCopy.length;
                  }
                  @Override public int nextInt() {
                      return defensiveCopy[index++];
                  }
              };
          }
  
      }
  
  }
  