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package jscl.util;

import javax.annotation.Nonnull;
import java.util.*;

public class ArrayUtils {

	private ArrayUtils() {
	}

	public static Object[] concat(Object o1[], Object o2[], Object res[]) {
		System.arraycopy(o1, 0, res, 0, o1.length);
		System.arraycopy(o2, 0, res, o1.length, o2.length);
		return res;
	}

	public static  T[] toArray(@Nonnull List list, T res[]) {
		int n = list.size();

		for (int i = 0; i < n; i++) {
			res[i] = list.get(i);
		}

		return res;
	}

	public static int[] toArray(@Nonnull List list, @Nonnull int result[]) {
		int n = list.size();

		for (int i = 0; i < n; i++) {
			result[i] = list.get(i);
		}

		return result;
	}

	public static  List toList(@Nonnull Collection collection) {
		return new ArrayList(collection);
	}

	public static String toString(@Nonnull Object array[]) {
		final StringBuilder result = new StringBuilder();
		result.append("{");
		for (int i = 0; i < array.length; i++) {
			result.append(array[i]).append(i < array.length - 1 ? ", " : "");
		}
		result.append("}");
		return result.toString();
	}

	private static final int BINARY_SEARCH_THRESHOLD = 5000;

	public static > int binarySearch(@Nonnull List list, @Nonnull T key) {
		if (list instanceof RandomAccess || list.size() < BINARY_SEARCH_THRESHOLD)
			return indexedBinarySearch(list, key);
		else
			return iteratorBinarySearch(list, key);
	}

	private static > int indexedBinarySearch(@Nonnull List list, @Nonnull T key) {
		int low = 0;
		int high = list.size() - 1;

		while (low <= high) {
			int mid = (low + high) >> 1;
			T midVal = list.get(mid);
			int cmp = midVal.compareTo(key);

			if (cmp < 0)
				low = mid + 1;
			else if (cmp > 0)
				high = mid - 1;
			else
				return mid; // key found
		}
		return -(low + 1);  // key not found
	}

	private static > int iteratorBinarySearch(@Nonnull List list, @Nonnull T key) {
		int low = 0;
		int high = list.size() - 1;
		final ListIterator it = list.listIterator();

		while (low <= high) {
			int mid = (low + high) >> 1;
			T midVal = get(it, mid);
			int cmp = midVal.compareTo(key);

			if (cmp < 0)
				low = mid + 1;
			else if (cmp > 0)
				high = mid - 1;
			else
				return mid; // key found
		}
		return -(low + 1);  // key not found
	}

	@Nonnull
	private static  T get(@Nonnull ListIterator it, int index) {
		T result;

		int pos = it.nextIndex();
		if (pos <= index) {
			do {
				result = it.next();
			} while (pos++ < index);
		} else {
			do {
				result = it.previous();
			} while (--pos > index);
		}

		return result;
	}
}