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CDS QL Execution Engine

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/*******************************************************************
 * © 2023 SAP SE or an SAP affiliate company. All rights reserved. *
 *******************************************************************/
package com.sap.cds.jdbc.sqlite.functions;

import java.sql.SQLException;
import java.util.regex.Pattern;

import org.sqlite.Function;

/**
 * Emulate SQL standard implementation as LIKE_REGEX(field, pattern, flags).
 */
public class LikeRegexpFunction extends Function {

	@Override
	protected void xFunc() throws SQLException {
		try {
			String text = value_text(0);
			String pattern = value_text(1);
			String flags = value_text(2);

			// Emulate the way H2 does that. The 'c' is not supported.
			int arguments = Pattern.UNICODE_CASE;
			for (int i = 0; i < flags.length(); i++) {
				switch (flags.charAt(i)) {
					case 'i' -> arguments |= Pattern.CASE_INSENSITIVE;
					case 'm' -> arguments |= Pattern.MULTILINE;
					case 'n' -> arguments |= Pattern.DOTALL;
					default -> throw new IllegalArgumentException("Unsupported flag: " + flags.charAt(i));
				}
			}

			boolean found = Pattern.compile(pattern, arguments).matcher(text).find();
			result(found ? 1 : 0);
		} catch (Exception e) {
			error(e.getMessage());
		}
	}
}