/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.jpa.internal.util;

An old-style query might pass positional numbers of Query parameters as strings. This implies we always need to
attempt parsing string parameters to see if this deprecated feature is being used, but parsing leads to catching (and
ignoring) NumberFormatException at runtime which is a performance problem, especially as the parse would fail
each time a non-deprecated form is processed.
This class is meant to avoid the need to allocate these exceptions at runtime.
Use this class to convert String to Integer when it's unlikely to be successful: if you expect it to be a normal number,
for example when a non successful parsing would be an error, using this utility is just an overhead.
Author:
Sanne Grinovero/**
 * An old-style query might pass positional numbers of Query parameters as strings. This implies we always need to
 * attempt parsing string parameters to see if this deprecated feature is being used, but parsing leads to catching (and
 * ignoring) NumberFormatException at runtime which is a performance problem, especially as the parse would fail
 * each time a non-deprecated form is processed.
 * This class is meant to avoid the need to allocate these exceptions at runtime.
 *
 * Use this class to convert String to Integer when it's unlikely to be successful: if you expect it to be a normal number,
 * for example when a non successful parsing would be an error, using this utility is just an overhead.
 *
 * @author Sanne Grinovero
 */
public final class PessimisticNumberParser {

	private PessimisticNumberParser() {
		//not to be constructed
	}

	public static Integer toNumberOrNull(final String parameterName) {
		if ( isValidNumber( parameterName ) ) {
			try {
				return Integer.valueOf( parameterName );
			}
			catch (NumberFormatException e) {
				//It wasn't valid after all, so return null
			}
		}
		return null;
	}

	private static boolean isValidNumber(final String parameterName) {
		if ( parameterName.length() == 0 ) {
			return false;
		}
		final char firstDigit = parameterName.charAt( 0 );
		if ( Character.isDigit( firstDigit ) || '-' == firstDigit || '+' == firstDigit ) {
			//check the remaining characters
			for ( int i = 1; i < parameterName.length(); i++ ) {
				if ( !Character.isDigit( parameterName.charAt( i ) ) ) {
					return false;
				}
			}
			//Some edge cases are left open: just a sign would return true.
			//For those cases you'd have a NumberFormatException swallowed.
			return true;
		}
		return false;
	}

}