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package org.sentrysoftware.metricshub.engine.common.helpers;

/*-
 * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
 * MetricsHub Engine
 * ჻჻჻჻჻჻
 * Copyright 2023 - 2024 Sentry Software
 * ჻჻჻჻჻჻
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
 */

import java.util.Arrays;
import java.util.Objects;
import java.util.function.Predicate;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Utility class for handling arrays and common array-related operations.
 */
public class ArrayHelper {

	private ArrayHelper() {}

	/**
	 * Returns the element at the specified position in the array.
	 *
	 * @param           The type of elements in the array.
	 * @param array        The array from which to retrieve the element.
	 * @param index        Index of the element to return.
	 * @param defaultValue The default value to return if the element cannot be extracted.
	 * @return The element at the specified position, or the default value if not present.
	 */
	public static  T getValueAtIndex(T[] array, int index, T defaultValue) {
		if (array == null || array.length <= index) {
			return defaultValue;
		}
		return array[index];
	}

	/**
	 * Check if the given data matches using the predicate function.

	 * Each data element is converted to lower case before applying the predicate.
	 *
	 * @param predicate boolean-valued function to check the passed data
	 * @param data      the input to the predicate
	 * @return true if one of the data matched otherwise false
	 */
	public static boolean anyMatchLowerCase(final Predicate predicate, final String... data) {
		return Arrays.stream(data).filter(Objects::nonNull).map(String::toLowerCase).anyMatch(predicate);
	}

	/**
	 * Regular expression that extracts in group(1) the hexadecimal data (trimming white spaces and 0x or # prefix)
	 */
	private static final Pattern HEX_PATTERN = Pattern.compile(
		"^\\s*(?:0x|#)?([0-9a-f]*)\\s*$",
		Pattern.CASE_INSENSITIVE
	);

	/**
	 * Convert the specified hexadecimal string into a byte array.
	 * 

	 * Example:
	 * 

	 * "0x010203" => new byte[] { 0x01, 0x02, 0x03 }
	 * 

	 * @param hexString Hexadecimal string (may be prefixed with "0x" or "#")
	 * @return the corresponding byte array
	 */
	public static byte[] hexToByteArray(String hexString) {
		// Null => null
		if (hexString == null) {
			return new byte[] {};
		}

		// Extract the hexadecimal data (remove 0x or # prefix)
		Matcher hexMatcher = ArrayHelper.HEX_PATTERN.matcher(hexString);
		if (!hexMatcher.find()) {
			throw new IllegalArgumentException("Invalid hexadecimal data: " + hexString);
		}
		final String hexData = hexMatcher.group(1);

		final int len = hexData.length();
		if (len % 2 != 0) {
			throw new IllegalArgumentException("Missing or extraneous digit in " + hexData);
		}

		byte[] data = new byte[len / 2];
		for (int i = 0; i < len; i += 2) {
			data[i / 2] = (byte) ((Character.digit(hexData.charAt(i), 16) << 4) + Character.digit(hexData.charAt(i + 1), 16));
		}

		return data;
	}
}