/*******************************************************************************
 * Copyright (c) 2004, 2013 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Andrew Niefer (IBM Corporation) - initial API and implementation
 *     Markus Schorn (Wind River Systems)
 *     Andrew Ferguson (Symbian)
 *     Mike Kucera (IBM)
 *     Sergey Prigogin (Google)
 *     Nathan Ridge
 *******************************************************************************/
package org.eclipse.cdt.core.parser.util;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;

import org.eclipse.core.runtime.Assert;

/**
 * @noextend This class is not intended to be subclassed by clients.
 */
public abstract class ArrayUtil {
    private static final int DEFAULT_LENGTH = 2;

    /**
     * Assumes that array contains {@code null}s at the end, only. 
     * Appends element after the last non-{@code null} element. 
     * If the array is {@code null} or not large enough, a larger one is allocated, using
     * the given class object.
     */
	@SuppressWarnings("unchecked")
	public static <T> T[] append(Class<T> c, T[] array, T obj) {
    	if (obj == null)
    		return array;
    	if (array == null || array.length == 0) {
    		array = (T[]) Array.newInstance(c, DEFAULT_LENGTH);
    		array[0] = obj;
    		return array;
    	}

    	int i= findFirstNull(array);
    	if (i >= 0) {
    		array[i]= obj;
    		return array;
    	}

    	T[] temp = (T[]) Array.newInstance(c, Math.max(array.length * 2, DEFAULT_LENGTH));
    	System.arraycopy(array, 0, temp, 0, array.length);
    	temp[array.length] = obj;
    	return temp;
    }

    /**
     * Assumes that array contains {@code null}s at the end, only. 
     * Appends element after the last non-{@code null} element. 
     * If the array is not large enough, a larger one is allocated.
     * Null <code>array</code> is supported for backward compatibility only and only when T is
     * Object.
     */
    @SuppressWarnings("unchecked")
	public static <T> T[] append(T[] array, T obj) {
    	if (obj == null)
    		return array;
    	if (array == null || array.length == 0) {
    		Class<? extends Object> c = array != null ? array.getClass().getComponentType() : Object.class;
    		array = (T[]) Array.newInstance(c, DEFAULT_LENGTH);
    		array[0] = obj;
    		return array;
    	}

    	int i= findFirstNull(array);
    	if (i >= 0) {
    		array[i]= obj;
    		return array;
    	}

    	T[] temp = (T[]) Array.newInstance(array.getClass().getComponentType(),
    			Math.max(array.length * 2, DEFAULT_LENGTH));
    	System.arraycopy(array, 0, temp, 0, array.length);
    	temp[array.length] = obj;
    	return temp;
    }

    /**
     * Assumes that array contains {@code null}s at the end, only.
     *
     * @return index of first {@code null}, or -1
     */ 
    private static int findFirstNull(Object[] array) {
    	int low= 0;
    	int high= array.length;
    	while (low < high) {
    		int mid= (low + high) >>> 1;
    		if (array[mid] == null) {
    			high= mid;
    		} else {
    			low= mid + 1;
    		}
    	}
		return high < array.length ? high : -1;
	}

    /**
     * @deprecated Use {@link #appendAt(Class, Object[], int, Object)} instead.
     * @since 4.0
     */
    @Deprecated
	@SuppressWarnings("unchecked")
	public static Object[] append(Class<?> c, Object[] array, int currentLength, Object obj) {
    	return appendAt((Class<Object>) c, array, currentLength, obj);
    }

    /**
     * Assumes that array contains {@code null}s at the end, only. 
     * Appends object using the current length of the array.
     * @since 5.1
     */
    @SuppressWarnings("unchecked")
	public static <T> T[] appendAt(Class<T> c, T[] array, int currentLength, T obj) {
    	if (obj == null)
    		return array;
    	if (array == null || array.length == 0) {
    		array = (T[]) Array.newInstance(c, DEFAULT_LENGTH);
    		array[0] = obj;
    		return array;
    	}

    	if (currentLength < array.length) {
    		Assert.isTrue(array[currentLength] == null);
    		Assert.isTrue(currentLength == 0 || array[currentLength - 1] != null);
    		array[currentLength]= obj;
    		return array;
    	}

    	T[] temp = (T[]) Array.newInstance(c, array.length * 2);
    	System.arraycopy(array, 0, temp, 0, array.length);
    	temp[array.length] = obj;
    	return temp;
    }

    /**
     * Assumes that array contains {@code null}s at the end, only. 
     * Appends object using the current length of the array.
     * @param array The array to append to. Not {@code null}
     * @param currentLength The number of non-{@code null} elements in the array
     * @param obj The object to append. Not {@code null}
     * @return The modified array, which may be the same as the first parameter. 
     * @since 5.4
     */
	public static <T> T[] appendAt(T[] array, int currentLength, T obj) {
    	if (obj == null)
    		return array;
    	if (currentLength >= array.length) {
        	array = Arrays.copyOf(array, Math.max(Math.max(currentLength + 1, array.length * 2), DEFAULT_LENGTH));
    	}
   		Assert.isTrue(array[currentLength] == null);
   		Assert.isTrue(currentLength == 0 || array[currentLength - 1] != null);
   		array[currentLength]= obj;
   		return array;
    }

    /**
     * Trims the given array and returns a new array with no {@code null} entries.
     * Assumes that {@code null}s can be found at the end, only.
     * if {@code array} is {@code null}, a new array of length 0 is returned
     * if {@code forceNew} is {@code true}, a new array will always be created.
     * if {@code forceNew} is {@code false}, a new array will only be created if the original array
     * contained {@code null} entries.
     *  
     * @param c the type of the new array
     * @param array the array to be trimmed
     * @param forceNew
     */
    @SuppressWarnings("unchecked")
	public static <T> T[] trim(Class<T> c, T[] array, boolean forceNew) {
        if (array == null)
            return (T[]) Array.newInstance(c, 0);

        int i = array.length;
        if (i == 0 || array[i - 1] != null) {
        	if (!forceNew) {
        		return array;
        	}
        } else {
        	i= findFirstNull(array);
        	Assert.isTrue(i >= 0);
        }

        T[] temp = (T[]) Array.newInstance(c, i);
        System.arraycopy(array, 0, temp, 0, i);
        return temp;
    }

    public static <T> T[] trim(Class<T> c, T[] array) {
        return trim(c, array, false);
    }

    /**
     * Trims the given array and returns a new array with no {@code null} entries.
     * Assumes that {@code null}s can be found at the end, only.
     * if {@code forceNew} is {@code true}, a new array will always be created.
     * if {@code forceNew} is {@code false}, a new array will only be created if the original array
     * contained {@code null} entries.
     *  
     * @param array the array to be trimmed
     * @param forceNew
     * @since 5.2
     */
	public static <T> T[] trim(T[] array, boolean forceNew) {
        int i = array.length;
        if (i == 0 || array[i - 1] != null) {
        	if (!forceNew) {
        		return array;
        	}
        } else {
        	i= findFirstNull(array);
        	Assert.isTrue(i >= 0);
        }

        return Arrays.copyOf(array, i);
    }

    /**
     * Trims the given array and returns a new array with no {@code null} entries.
     * Assumes that {@code null}s can be found at the end, only.
     *  
     * @param array the array to be trimmed
     * @since 5.2
     */
	public static <T> T[] trim(T[] array) {
		return trim(array, false);
	}

    /**
     * Trims the given array and returns a new array with no {@code null} entries.
     * Assumes that {@code null}s can be found at the end, only.
     * Similar to {@link #trimAt(Class, Object[], int)}, but uses the new length instead of index.
     *  
     * @param array the array to be trimmed
     * @param newLength the new length of the array, has to be less or equal than
     *     the current length.
     * @return the modified array, which may be the same as the first parameter. 
     * @since 5.4
     */
	public static <T> T[] trim(T[] array, int newLength) {
		if (newLength == array.length)
			return array;
   		Assert.isTrue(array[newLength] == null);
   		Assert.isTrue(newLength == 0 || array[newLength - 1] != null);
		return Arrays.copyOf(array, newLength);
	}

    /**
     * Takes contents of the two arrays up to the first {@code null} element and concatenates
     * them.
     * @param c The type of the element of the returned array if there was not enough free space
     *     in the destination array.
     * @param dest The destination array. The elements of the source array are added to this array
     *     if there is enough free space in it. May be {@code null}. 
     * @param source The source array. May not be {@code null}. 
     * @return The concatenated array, which may be the same as the first parameter. 
     */
    @SuppressWarnings("unchecked")
	public static <T> T[] addAll(Class<T> c, T[] dest, Object[] source) {
        if (source == null || source.length == 0)
            return dest;

        int numToAdd = findFirstNull(source);
        if (numToAdd <= 0) {
        	if (numToAdd == 0) {
        		return dest;
        	}
        	numToAdd= source.length;
        }

        if (dest == null || dest.length == 0) {
            dest = (T[]) Array.newInstance(c, numToAdd);
            System.arraycopy(source, 0, dest, 0, numToAdd);
            return dest;
        }

        int firstFree = findFirstNull(dest);
        if (firstFree < 0) {
        	firstFree= dest.length;
        }

        if (firstFree + numToAdd <= dest.length) {
            System.arraycopy(source, 0, dest, firstFree, numToAdd);
            return dest;
        }
        dest = Arrays.copyOf(dest, firstFree + numToAdd);
        System.arraycopy(source, 0, dest, firstFree, numToAdd);
        return dest;
    }

    /**
     * Takes contents of the two arrays up to the first {@code null} element and concatenates them.
     *
     * @param dest The destination array. The elements of the source array are added to this array
     *     if there is enough free space in it. May be {@code null}. 
     * @param source The source array. May not be {@code null}. 
     * @return The concatenated array, which may be the same as the first parameter. 
     * @since 5.2
     */
    @SuppressWarnings("unchecked")
	public static <T> T[] addAll(T[] dest, Object[] source) {
        if (source == null || source.length == 0)
            return dest;

        int numToAdd = findFirstNull(source);
        if (numToAdd <= 0) {
        	if (numToAdd == 0) {
        		return dest;
        	}
        	numToAdd= source.length;
        }

        if (dest == null || dest.length == 0) {
    		Class<? extends Object> c =	dest != null ?
    				dest.getClass().getComponentType() : source.getClass().getComponentType();
            dest = (T[]) Array.newInstance(c, numToAdd);
            System.arraycopy(source, 0, dest, 0, numToAdd);
            return dest;
        }

        int firstFree = findFirstNull(dest);
        if (firstFree < 0) {
        	firstFree= dest.length;
        }

        if (firstFree + numToAdd <= dest.length) {
            System.arraycopy(source, 0, dest, firstFree, numToAdd);
            return dest;
        }
        dest = Arrays.copyOf(dest, firstFree + numToAdd);
        System.arraycopy(source, 0, dest, firstFree, numToAdd);
        return dest;
    }

	/**
	 * Adds all elements of an array to a collection.
	 * @since 5.4
	 */
    @SafeVarargs
	public static <T> void addAll(Collection<? super T> collection, T... elements) {
		if (collection instanceof ArrayList) {
			((ArrayList<?>) collection).ensureCapacity(collection.size() + elements.length);
		}
		for (T element : elements) {
			collection.add(element);
		}
	}

	/**
     * Returns whether the specified array contains the specified object. The comparison is by
     * object identity.
     *
     * @param array the array to search
     * @param obj the object to search for
     * @return <code>true</code> if the specified array contains the specified object, or
     *     the specified array is {@code null}
     */
    public static <T> boolean contains(T[] array, T obj) {
    	return indexOf(array, obj) >= 0;
    }

    /**
     * Returns the index into the specified array of the specified object, or -1 if the array does
     * not contain the object, or if the array is {@code null}.  Comparison is by object identity.
     *
     * @param array the array to search
     * @param obj the object to search for
     * @return the index into the specified array of the specified object, or -1 if the array does
     *     not contain the object, or if the array is {@code null}
     */
    public static <T> int indexOf(T[] array, T obj) {
    	int result = -1;
    	if (array != null) {
    		for (int i = 0; i < array.length; i++) {
    			if (array[i] == obj)
    				return i;
    		}
    	}
    	return result;
    }

    /**
     * Assumes that array contains {@code null}s at the end, only. 
     * Returns whether the specified array contains the specified object. Comparison is by
     * object identity.
     * 
     * @param array the array to search
     * @param obj the object to search for
     * @return true if the specified array contains the specified object, or the specified array is
     *     {@code null}
     */
    public static <T> boolean containsEqual(T[] array, T obj) {
    	return indexOfEqual(array, obj) != -1;
    }

    /**
     * Assumes that array contains {@code null}s at the end, only. 
     * Returns the index into the specified array of the specified object, or -1 if the array does
     * not contain the object, or if the array is {@code null}.  Comparison is by equals().
     *
     * @param array the array to search
     * @param obj the object to search for
     * @return the index into the specified array of the specified object, or -1 if the array does
     *     not contain an equal object, or if the array is {@code null}
     */    
	public static <T> int indexOfEqual(T[] array, T obj) {
    	int result = -1;
    	if (array != null) {
    		for (int i= 0; (i < array.length) && (array[i] != null); i++) {
    			if (array[i].equals(obj))
    				return i;
    		}
    	}
    	return result;
    }

	/**
	 * Moves all {@code null} elements to the end of the array. The order of non-{@code null}
	 * elements is preserved.
	 *
	 * @since 5.4
	 */
	public static void compact(Object[] array) {
		int j = 0;
        for (int i = 0; i < array.length; i++) {
            if (array[i] != null) {
            	if (j != i) {
            		array[j] = array[i];
            		array[i] = null;
            	}
            	j++;
            }
        }
	}
	
	/**
	 * Removes all of the {@code null}s from the array and returns a new array that contains all
	 * of the non-{@code null} elements.
     *
     * If there are no {@code null}s in the original array then the original array is returned.

	 * Note that this method should only be used when the placement of {@code null}s within
	 * the array is unknown (due to performance efficiency).  
	 */
	@SuppressWarnings("unchecked")
	public static <T> T[] removeNulls(Class<T> c, T[] array) {
        if (array == null)
            return (T[]) Array.newInstance(c, 0);

        int i;
		int validEntries = 0;
		for (i = 0; i < array.length; i++) {
	         if (array[i] != null)
	        	 validEntries++;
	    }

		if (array.length == validEntries) 
			return array;

		T[] newArray = (T[]) Array.newInstance(c, validEntries);
		int j = 0;
        for (i = 0; i < array.length; i++) {
            if (array[i] != null)
            	newArray[j++] = array[i];
        }

		return newArray;
	}

	/**
	 * Removes all of the {@code null}s from the array and returns a new array that contains all
	 * of the non-{@code null} elements.
     * <p>
     * If there are no {@code null}s in the original array then the original array is returned.
     * <p>
	 * Note that this method should only be used when the placement of {@code null}s within
	 * the array is unknown (due to performance efficiency).  
	 * @since 5.2
	 */
	@SuppressWarnings("unchecked")
	public static <T> T[] removeNulls(T[] array) {
		int validEntries = 0;
		for (int i = 0; i < array.length; i++) {
	         if (array[i] != null)
	        	 validEntries++;
	    }

		if (array.length == validEntries) 
			return array;

		T[] newArray = (T[]) Array.newInstance(array.getClass().getComponentType(), validEntries);
		int j = 0;
        for (int i = 0; i < array.length; i++) {
            if (array[i] != null)
            	newArray[j++] = array[i];
        }

		return newArray;
	}

	/**
	 * @deprecated Use {@link #trim(Object[], int)} or {@link #trimAt(Class, Object[], int)} instead
	 */
	@SuppressWarnings("unchecked")
	@Deprecated
	public static Object[] removeNullsAfter(Class<?> c, Object[] array, int index) {
		return trimAt((Class<Object>) c, array, index);
	}

	/**
	 * To improve performance, this method should be used instead of
	 * {@link #removeNulls(Class, Object[])} when all of the non-{@code null} elements in
	 * the array are grouped together at the beginning of the array and all of the s are at
	 * the end of the array. The position of the last non-{@code null} element in the array must
	 * also be known.
	 * <p>
	 * If you don't intend to pass {@code null} array, consider using {@link #trim(Object[], int)}
	 * instead.
	 *
	 * @since 5.1
	 */
	@SuppressWarnings("unchecked")
	public static <T> T[] trimAt(Class<T> c, T[] array, int index) {
        final int newLen= index + 1;
        if (array != null && array.length == newLen)
			return array;

        T[] newArray = (T[]) Array.newInstance(c, newLen);
        if (array != null && newLen > 0)
        	System.arraycopy(array, 0, newArray, 0, newLen);
		return newArray;
	}

	/**
	 * Inserts the {@code obj} at the beginning of the array, shifting the whole thing one index
	 * Assumes that array contains {@code null}s at the end, only. 
	 */
	@SuppressWarnings("unchecked")
	public static <T> T[] prepend(Class<T> c, T[] array, T obj) {
		if (obj == null)
    		return array;
        if (array == null || array.length == 0) {
            array = (T[]) Array.newInstance(c, DEFAULT_LENGTH);
            array[0] = obj;
            return array;
        }

        int i = findFirstNull(array);
        if (i >= 0) {
			System.arraycopy(array, 0, array, 1, i);
			array[0] = obj;
        } else {
			T[] temp = (T[]) Array.newInstance(c, array.length * 2);
	        System.arraycopy(array, 0, temp, 1, array.length);
	        temp[0] = obj;
	        array = temp;
		}

        return array;
	}

	/**
	 * Inserts the {@code obj} at the beginning of the array, shifting the whole thing one index
	 * Assumes that array contains {@code null}s at the end, only. 
	 * array must not be {@code null}.
	 * @since 5.2
	 */
	public static <T> T[] prepend(T[] array, T obj) {
		Assert.isNotNull(array);
		
		if (obj == null)
    		return array;
        if (array.length == 0) {
            array = newArray(array, DEFAULT_LENGTH);
            array[0] = obj;
            return array;
        }

        int i = findFirstNull(array);
        if (i >= 0) {
			System.arraycopy(array, 0, array, 1, i);
			array[0] = obj;
        } else {
			T[] temp = newArray(array, array.length * 2);
	        System.arraycopy(array, 0, temp, 1, array.length);
	        temp[0] = obj;
	        array = temp;
		}

        return array;
	}

	@SuppressWarnings("unchecked")
	private static <T> T[] newArray(T[] array, int newLen) {
		return (T[]) Array.newInstance(array.getClass().getComponentType(), newLen);
	}

	/**
	 * Removes first occurrence of element in array and moves objects behind up front.
	 * @since 4.0
	 */
	public static <T> void remove(T[] array, T element) {
		if (array != null) {
			for (int i = 0; i < array.length; i++) {
				if (element == array[i]) {
					System.arraycopy(array, i + 1, array, i, array.length - i - 1);
					array[array.length - 1]= null;
					return;
				}
			}
		}
	}

    /**
     * Stores the specified array contents in a new array of specified runtime type.
     * 
     * @param target the runtime type of the new array
     * @param source the source array
     * @return the current array stored in a new array with the specified runtime type,
     *     or {@code null} if source is {@code null}.
     */
    @SuppressWarnings("unchecked")
    public static <S, T> T[] convert(Class<T> target, S[] source) {
    	T[] result= null;
    	if (source != null) {
    		result= (T[]) Array.newInstance(target, source.length);
    		for (int i= 0; i < source.length; i++) {
    			result[i]= (T) source[i];
    		}
    	}
    	return result;
    }

    /**
     * Reverses order of elements in an array.
     * @param array the array
     * @since 5.4
     */
    public static void reverse(Object[] array) {
    	reverse(array, 0, array.length);
    }

    /**
     * Reverses order of elements in a subsection of an array.
     *
     * @param array the array
     * @param fromIndex the index of the first affected element (inclusive)
     * @param toIndex the index of the last affected element (exclusive)
     * @since 5.4
     */
    public static void reverse(Object[] array, int fromIndex, int toIndex) {
    	for (int i = fromIndex, j = toIndex; i < --j; i++) {
    		Object tmp = array[i];
    		array[i] = array[j];
    		array[j] = tmp;
    	}
    }

    /**
     * Returns a new array that contains all of the elements of the given array except
     * the first one.
     * 
	 * @throws NullPointerException if {@code array} is {@code null}
	 * @throws IllegalArgumentException if {@code array} is empty
	 * @since 5.1
	 */
    @SuppressWarnings("unchecked")
	public static <T> T[] removeFirst(T[] array) {
    	int n = array.length;
    	if (n <= 0)
    		throw new IllegalArgumentException();
    	
    	T[] newArgs = (T[]) Array.newInstance(array.getClass().getComponentType(), n - 1);
    	for (int i = 1; i < n; i++) {
    		newArgs[i - 1] = array[i];
    	}
    	return newArgs;
    }

    /**
     * Returns a new array that contains elements of the given array except duplicates and
     * {@code null}s. Duplicates are determined by {@link Object#equals(Object)} method.
     * 
	 * @throws NullPointerException if {@code array} is {@code null}
	 * @since 5.5
	 */
	public static <T> T[] removeDuplicates(T[] array) {
		int k = 0;
		if (array.length >= 16) {
			HashSet<T> set = new HashSet<T>(array.length);
			for (int i = 0; i < array.length; i++) {
				T obj = array[i];
				if (obj != null && set.add(obj)) {
					array[k++] = obj;
				}
			}
		} else {
			for (int i = 0; i < array.length; i++) {
				T obj = array[i];
				if (obj != null) {
					array[k++] = obj;
					for (int j = i + 1; j < array.length; j++) {
						if (obj.equals(array[j]))
							array[j] = null;
					}
				}
			}
		}
		if (k == array.length)
			return array;
		return Arrays.copyOf(array, k);
	}

    public static int[] setInt(int[] array, int idx, int val) {
        if (array == null) {
            array = new int[DEFAULT_LENGTH > idx + 1 ? DEFAULT_LENGTH : idx + 1];
            array[idx] = val;
            return array;
        }

        if (array.length <= idx) {
            int newLen = array.length * 2;
            while (newLen <= idx)
            	newLen *= 2;
            int[] temp = new int[newLen];
            System.arraycopy(array, 0, temp, 0, array.length);
            
            array = temp;
        }
        array[idx] = val;
        return array;
    }
    
    /**
     * Filter the elements of an array down to just the ones
     * that match the given predicate.
	 * @since 5.6
	 */
	public static <T> T[] filter(T[] array, IUnaryPredicate<T> predicate) {
		T[] result = array;
		int resultIndex = 0;
		for (int i = 0; i < array.length; ++i) {
			if (predicate.apply(array[i])) {
				if (result != array) {
					result[resultIndex] = array[i];
				}
				++resultIndex;
			} else {
				if (result == array) {
					// There will be at most array.length - 1 filtered elements. 
					result = Arrays.copyOf(array, array.length - 1);
					Arrays.fill(result, i, result.length, null);
				}
			}
		}
		return resultIndex == result.length ? result : Arrays.copyOf(result, resultIndex);
    }
}
