/*
    * 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 static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.collect.Lists;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.RandomAccess;
  
  import javax.annotation.Nullable;
  
  /**
   * GWT emulated version of {@link ImmutableList}.
   * TODO(cpovirk): more doc
   *
   * @author Hayward Chan
   */
  @SuppressWarnings("serial") // we're overriding default serialization
  public abstract class ImmutableList<E> extends ImmutableCollection<E>
      implements List<E>, RandomAccess {
    static final ImmutableList<Object> EMPTY = 
        new RegularImmutableList<Object>(Collections.emptyList());
    
    ImmutableList() {}
  
    // Casting to any type is safe because the list will never hold any elements.
    @SuppressWarnings("unchecked")
    public static <E> ImmutableList<E> of() {
      return (ImmutableList<E>) EMPTY;
    }
  
    public static <E> ImmutableList<E> of(E element) {
      return new SingletonImmutableList<E>(element);
    }
  
    public static <E> ImmutableList<E> of(E e1, E e2) {
      return new RegularImmutableList<E>(
          ImmutableList.<E>nullCheckedList(e1, e2));
    }
  
    public static <E> ImmutableList<E> of(E e1, E e2, E e3) {
      return new RegularImmutableList<E>(
          ImmutableList.<E>nullCheckedList(e1, e2, e3));
    }
  
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4) {
      return new RegularImmutableList<E>(
          ImmutableList.<E>nullCheckedList(e1, e2, e3, e4));
    }
  
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5) {
      return new RegularImmutableList<E>(
          ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5));
    }
  
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
      return new RegularImmutableList<E>(
          ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6));
    }
  
    public static <E> ImmutableList<E> of(
        E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
      return new RegularImmutableList<E>(
           ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7));
    }
  
    public static <E> ImmutableList<E> of(
        E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
      return new RegularImmutableList<E>(
           ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8));
    }
  
    public static <E> ImmutableList<E> of(
        E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
      return new RegularImmutableList<E>(
           ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8, e9));
    }
  
   public static <E> ImmutableList<E> of(
       E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
     return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(
         e1, e2, e3, e4, e5, e6, e7, e8, e9, e10));
   }
 
   public static <E> ImmutableList<E> of(
       E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11) {
     return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(
         e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11));
   }
 
   public static <E> ImmutableList<E> of(
       E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11,
       E e12, E... others) {
     final int paramCount = 12;
     Object[] array = new Object[paramCount + others.length];
     arrayCopy(array, 0, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11, e12);
     arrayCopy(array, paramCount, others);
     return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(array));
   }
 
   private static void arrayCopy(Object[] dest, int pos, Object... source) {
     System.arraycopy(source, 0, dest, pos, source.length);
   }
 
   public static <E> ImmutableList<E> copyOf(Iterable<? extends E> elements) {
     checkNotNull(elements); // for GWT
     return (elements instanceof Collection)
         ? copyOf((Collection<? extends E>) elements)
         : copyOf(elements.iterator());
   }
 
   public static <E> ImmutableList<E> copyOf(Iterator<? extends E> elements) {
     return copyFromCollection(Lists.newArrayList(elements));
   }
 
   public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) {
     if (elements instanceof ImmutableCollection) {
       /*
        * TODO: When given an ImmutableList that's a sublist, copy the referenced
        * portion of the array into a new array to save space?
        */
       @SuppressWarnings("unchecked") // all supported methods are covariant
       ImmutableCollection<E> list = (ImmutableCollection<E>) elements;
       return list.asList();
     }
     return copyFromCollection(elements);
   }
 
   public static <E> ImmutableList<E> copyOf(E[] elements) {
     checkNotNull(elements); // eager for GWT
     return copyOf(Arrays.asList(elements));
   }
 
   private static <E> ImmutableList<E> copyFromCollection(
       Collection<? extends E> collection) {
     Object[] elements = collection.toArray();
     switch (elements.length) {
       case 0:
         return of();
       case 1:
         @SuppressWarnings("unchecked") // collection had only Es in it
         ImmutableList<E> list = new SingletonImmutableList<E>((E) elements[0]);
         return list;
       default:
         return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(elements));
     }
   }
 
   // Factory method that skips the null checks.  Used only when the elements
   // are guaranteed to be non-null.
   static <E> ImmutableList<E> unsafeDelegateList(List<? extends E> list) {
     switch (list.size()) {
       case 0:
         return of();
       case 1:
         return new SingletonImmutableList<E>(list.iterator().next());
       default:
         @SuppressWarnings("unchecked")
         List<E> castedList = (List<E>) list;
         return new RegularImmutableList<E>(castedList);
     }
   }
 
   /**
    * Views the array as an immutable list.  The array must have only {@code E} elements.
    *
    * <p>The array must be internally created.
    */
   @SuppressWarnings("unchecked") // caller is reponsible for getting this right
   static <E> ImmutableList<E> asImmutableList(Object[] elements) {
     return unsafeDelegateList((List) Arrays.asList(elements));
   }
 
   private static <E> List<E> nullCheckedList(Object... array) {
     for (int i = 0, len = array.length; i < len; i++) {
       if (array[i] == null) {
         throw new NullPointerException("at index " + i);
       }
     }
     @SuppressWarnings("unchecked")
     E[] castedArray = (E[]) array;
     return Arrays.asList(castedArray);
   }
 
   @Override
   public int indexOf(@Nullable Object object) {
     return (object == null) ? -1 : Lists.indexOfImpl(this, object);
   }
 
   @Override
   public int lastIndexOf(@Nullable Object object) {
     return (object == null) ? -1 : Lists.lastIndexOfImpl(this, object);
   }
 
   public final boolean addAll(int index, Collection<? extends E> newElements) {
     throw new UnsupportedOperationException();
   }
 
   public final E set(int index, E element) {
     throw new UnsupportedOperationException();
   }
 
   public final void add(int index, E element) {
     throw new UnsupportedOperationException();
   }
 
   public final E remove(int index) {
     throw new UnsupportedOperationException();
   }
 
   @Override public UnmodifiableIterator<E> iterator() {
     return listIterator();
   }
 
   @Override public ImmutableList<E> subList(int fromIndex, int toIndex) {
     return unsafeDelegateList(Lists.subListImpl(this, fromIndex, toIndex));
   }
 
   @Override public UnmodifiableListIterator<E> listIterator() {
     return listIterator(0);
   }
 
   @Override public UnmodifiableListIterator<E> listIterator(int index) {
     return new AbstractIndexedListIterator<E>(size(), index) {
       @Override
       protected E get(int index) {
         return ImmutableList.this.get(index);
       }
     };
   }
 
   @Override public ImmutableList<E> asList() {
     return this;
   }
 
   @Override
   public boolean equals(@Nullable Object obj) {
     return Lists.equalsImpl(this, obj);
   }
 
   @Override
   public int hashCode() {
     return Lists.hashCodeImpl(this);
   }
 
   public ImmutableList<E> reverse() {
     List<E> list = Lists.newArrayList(this);
     Collections.reverse(list);
     return unsafeDelegateList(list);
   }
 
   public static <E> Builder<E> builder() {
     return new Builder<E>();
   }
 
   public static final class Builder<E> extends ImmutableCollection.Builder<E> {
     private final ArrayList<E> contents;
 
     public Builder() {
       contents = Lists.newArrayList();
     }
 
     Builder(int capacity) {
       contents = Lists.newArrayListWithCapacity(capacity);
     }
 
     @Override public Builder<E> add(E element) {
       contents.add(checkNotNull(element));
       return this;
     }
 
     @Override public Builder<E> addAll(Iterable<? extends E> elements) {
       super.addAll(elements);
       return this;
     }
 
     @Override public Builder<E> add(E... elements) {
       checkNotNull(elements);  // for GWT
       super.add(elements);
       return this;
     }
 
     @Override public Builder<E> addAll(Iterator<? extends E> elements) {
       super.addAll(elements);
       return this;
     }
 
     @Override public ImmutableList<E> build() {
       return copyOf(contents);
     }
   }
 }