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 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package jdk.nashorn.internal.runtime;

import java.lang.invoke.MethodHandle;
import java.util.AbstractList;
import java.util.Deque;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.RandomAccess;
import java.util.concurrent.Callable;
import jdk.nashorn.api.scripting.JSObject;
import jdk.nashorn.api.scripting.ScriptObjectMirror;
import jdk.nashorn.internal.objects.Global;
import jdk.nashorn.internal.runtime.linker.Bootstrap;

An adapter that can wrap any ECMAScript Array-like object (that adheres to the array rules for the property length and having conforming push, pop, shift, unshift, and splice methods) and expose it as both a Java list and double-ended queue. While script arrays aren't necessarily efficient as dequeues, it's still slightly more efficient to be able to translate dequeue operations into pushes, pops, shifts, and unshifts, than to blindly translate all list's add/remove operations into splices. Also, it is conceivable that a custom script object that implements an Array-like API can have a background data representation that is optimized for dequeue-like access. Note that with ECMAScript arrays, push and pop operate at the end of the array, while in Java Deque they operate on the front of the queue and as such the Java dequeue push(Object) and pop() operations will translate to unshift and shift script operations respectively, while addLast(Object) and removeLast() will translate to push and pop. /**
 * An adapter that can wrap any ECMAScript Array-like object (that adheres to the array rules for the property
 * {@code length} and having conforming {@code push}, {@code pop}, {@code shift}, {@code unshift}, and {@code splice}
 * methods) and expose it as both a Java list and double-ended queue. While script arrays aren't necessarily efficient
 * as dequeues, it's still slightly more efficient to be able to translate dequeue operations into pushes, pops, shifts,
 * and unshifts, than to blindly translate all list's add/remove operations into splices. Also, it is conceivable that a
 * custom script object that implements an Array-like API can have a background data representation that is optimized
 * for dequeue-like access. Note that with ECMAScript arrays, {@code push} and {@code pop} operate at the end of the
 * array, while in Java {@code Deque} they operate on the front of the queue and as such the Java dequeue
 * {@link #push(Object)} and {@link #pop()} operations will translate to {@code unshift} and {@code shift} script
 * operations respectively, while {@link #addLast(Object)} and {@link #removeLast()} will translate to {@code push} and
 * {@code pop}.
 */
public class ListAdapter extends AbstractList<Object> implements RandomAccess, Deque<Object> {
    // Invoker creator for methods that add to the start or end of the list: PUSH and UNSHIFT. Takes fn, this, and value, returns void.
    private static final Callable<MethodHandle> ADD_INVOKER_CREATOR = invokerCreator(void.class, Object.class, JSObject.class, Object.class);

    // PUSH adds to the start of the list
    private static final Object PUSH = new Object();
    // UNSHIFT adds to the end of the list
    private static final Object UNSHIFT = new Object();

    // Invoker creator for methods that remove from the tail or head of the list: POP and SHIFT. Takes fn, this, returns Object.
    private static final Callable<MethodHandle> REMOVE_INVOKER_CREATOR = invokerCreator(Object.class, Object.class, JSObject.class);

    // POP removes from the start of the list
    private static final Object POP = new Object();
    // SHIFT removes from the end of the list
    private static final Object SHIFT = new Object();

    // SPLICE can be used to add a value in the middle of the list.
    private static final Object SPLICE_ADD = new Object();
    private static final Callable<MethodHandle> SPLICE_ADD_INVOKER_CREATOR = invokerCreator(void.class, Object.class, JSObject.class, int.class, int.class, Object.class);

    // SPLICE can also be used to remove values from the middle of the list.
    private static final Object SPLICE_REMOVE = new Object();
    private static final Callable<MethodHandle> SPLICE_REMOVE_INVOKER_CREATOR = invokerCreator(void.class, Object.class, JSObject.class, int.class, int.class);

    
wrapped object /** wrapped object */
    final JSObject obj;
    private final Global global;

    // allow subclasses only in this package
    ListAdapter(final JSObject obj, final Global global) {
        if (global == null) {
            throw new IllegalStateException(ECMAErrors.getMessage("list.adapter.null.global"));
        }

        this.obj = obj;
        this.global = global;
    }

    
Factory to create a ListAdapter for a given script object.
Params:
obj – script object to wrap as a ListAdapter
Returns:
A ListAdapter wrapper object/**
     * Factory to create a ListAdapter for a given script object.
     *
     * @param obj script object to wrap as a ListAdapter
     * @return A ListAdapter wrapper object
     */
    public static ListAdapter create(final Object obj) {
        final Global global = Context.getGlobal();
        return new ListAdapter(getJSObject(obj, global), global);
    }

    private static JSObject getJSObject(final Object obj, final Global global) {
        if (obj instanceof ScriptObject) {
            return (JSObject)ScriptObjectMirror.wrap(obj, global);
        } else if (obj instanceof JSObject) {
            return (JSObject)obj;
        }
        throw new IllegalArgumentException("ScriptObject or JSObject expected");
    }

    @Override
    public final Object get(final int index) {
        checkRange(index);
        return getAt(index);
    }

    private Object getAt(final int index) {
        return obj.getSlot(index);
    }

    @Override
    public Object set(final int index, final Object element) {
        checkRange(index);
        final Object prevValue = getAt(index);
        obj.setSlot(index, element);
        return prevValue;
    }

    private void checkRange(final int index) {
        if(index < 0 || index >= size()) {
            throw invalidIndex(index);
        }
    }

    @Override
    public int size() {
        return JSType.toInt32(obj.getMember("length"));
    }

    @Override
    public final void push(final Object e) {
        addFirst(e);
    }

    @Override
    public final boolean add(final Object e) {
        addLast(e);
        return true;
    }

    @Override
    public final void addFirst(final Object e) {
        try {
            getDynamicInvoker(UNSHIFT, ADD_INVOKER_CREATOR).invokeExact(getFunction("unshift"), obj, e);
        } catch(RuntimeException | Error ex) {
            throw ex;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }

    @Override
    public final void addLast(final Object e) {
        try {
            getDynamicInvoker(PUSH, ADD_INVOKER_CREATOR).invokeExact(getFunction("push"), obj, e);
        } catch(RuntimeException | Error ex) {
            throw ex;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }

    @Override
    public final void add(final int index, final Object e) {
        try {
            if(index < 0) {
                throw invalidIndex(index);
            } else if(index == 0) {
                addFirst(e);
            } else {
                final int size = size();
                if(index < size) {
                    getDynamicInvoker(SPLICE_ADD, SPLICE_ADD_INVOKER_CREATOR).invokeExact(obj.getMember("splice"), obj, index, 0, e);
                } else if(index == size) {
                    addLast(e);
                } else {
                    throw invalidIndex(index);
                }
            }
        } catch(final RuntimeException | Error ex) {
            throw ex;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }
    private Object getFunction(final String name) {
        final Object fn = obj.getMember(name);
        if(!(Bootstrap.isCallable(fn))) {
            throw new UnsupportedOperationException("The script object doesn't have a function named " + name);
        }
        return fn;
    }

    private static IndexOutOfBoundsException invalidIndex(final int index) {
        return new IndexOutOfBoundsException(String.valueOf(index));
    }

    @Override
    public final boolean offer(final Object e) {
        return offerLast(e);
    }

    @Override
    public final boolean offerFirst(final Object e) {
        addFirst(e);
        return true;
    }

    @Override
    public final boolean offerLast(final Object e) {
        addLast(e);
        return true;
    }

    @Override
    public final Object pop() {
        return removeFirst();
    }

    @Override
    public final Object remove() {
        return removeFirst();
    }

    @Override
    public final Object removeFirst() {
        checkNonEmpty();
        return invokeShift();
    }

    @Override
    public final Object removeLast() {
        checkNonEmpty();
        return invokePop();
    }

    private void checkNonEmpty() {
        if(isEmpty()) {
            throw new NoSuchElementException();
        }
    }

    @Override
    public final Object remove(final int index) {
        if(index < 0) {
            throw invalidIndex(index);
        } else if (index == 0) {
            return invokeShift();
        } else {
            final int maxIndex = size() - 1;
            if(index < maxIndex) {
                final Object prevValue = get(index);
                invokeSpliceRemove(index, 1);
                return prevValue;
            } else if(index == maxIndex) {
                return invokePop();
            } else {
                throw invalidIndex(index);
            }
        }
    }

    private Object invokeShift() {
        try {
            return getDynamicInvoker(SHIFT, REMOVE_INVOKER_CREATOR).invokeExact(getFunction("shift"), obj);
        } catch(RuntimeException | Error ex) {
            throw ex;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }

    private Object invokePop() {
        try {
            return getDynamicInvoker(POP, REMOVE_INVOKER_CREATOR).invokeExact(getFunction("pop"), obj);
        } catch(RuntimeException | Error ex) {
            throw ex;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }

    @Override
    protected final void removeRange(final int fromIndex, final int toIndex) {
        invokeSpliceRemove(fromIndex, toIndex - fromIndex);
    }

    private void invokeSpliceRemove(final int fromIndex, final int count) {
        try {
            getDynamicInvoker(SPLICE_REMOVE, SPLICE_REMOVE_INVOKER_CREATOR).invokeExact(getFunction("splice"), obj, fromIndex, count);
        } catch(RuntimeException | Error ex) {
            throw ex;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }

    @Override
    public final Object poll() {
        return pollFirst();
    }

    @Override
    public final Object pollFirst() {
        return isEmpty() ? null : invokeShift();
    }

    @Override
    public final Object pollLast() {
        return isEmpty() ? null : invokePop();
    }

    @Override
    public final Object peek() {
        return peekFirst();
    }

    @Override
    public final Object peekFirst() {
        return isEmpty() ? null : get(0);
    }

    @Override
    public final Object peekLast() {
        return isEmpty() ? null : get(size() - 1);
    }

    @Override
    public final Object element() {
        return getFirst();
    }

    @Override
    public final Object getFirst() {
        checkNonEmpty();
        return get(0);
    }

    @Override
    public final Object getLast() {
        checkNonEmpty();
        return get(size() - 1);
    }

    @Override
    public final Iterator<Object> descendingIterator() {
        final ListIterator<Object> it = listIterator(size());
        return new Iterator<Object>() {
            @Override
            public boolean hasNext() {
                return it.hasPrevious();
            }

            @Override
            public Object next() {
                return it.previous();
            }

            @Override
            public void remove() {
                it.remove();
            }
        };
    }

    @Override
    public final boolean removeFirstOccurrence(final Object o) {
        return removeOccurrence(o, iterator());
    }

    @Override
    public final boolean removeLastOccurrence(final Object o) {
        return removeOccurrence(o, descendingIterator());
    }

    private static boolean removeOccurrence(final Object o, final Iterator<Object> it) {
        while(it.hasNext()) {
            if(Objects.equals(o, it.next())) {
                it.remove();
                return true;
            }
        }
        return false;
    }

    private static Callable<MethodHandle> invokerCreator(final Class<?> rtype, final Class<?>... ptypes) {
        return new Callable<MethodHandle>() {
            @Override
            public MethodHandle call() {
                return Bootstrap.createDynamicCallInvoker(rtype, ptypes);
            }
        };
    }

    private MethodHandle getDynamicInvoker(final Object key, final Callable<MethodHandle> creator) {
        return global.getDynamicInvoker(key, creator);
    }
}