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/*
 * Copyright (C) 2020 Graylog, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Server Side Public License, version 1,
 * as published by MongoDB, Inc.
 *
 * 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
 * Server Side Public License for more details.
 *
 * You should have received a copy of the Server Side Public License
 * along with this program. If not, see
 * .
 */
package org.graylog2.system.urlwhitelist;

import org.apache.commons.lang3.StringUtils;

import java.util.Arrays;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

/**
 * Utility class to help creating an appropriate regex to be used in a whitelist entry.
 */
public class RegexHelper {
    /**
     * 
     * Replaces all placeholders in a "url template" with {@code .*?}, quotes everything else and adds {@code ^} and
     * {@code $} to it.
     * 
     * 
     * An example:
     * 
     * 
     * 
https://example.com/api/lookup?key=${key}
     * will become
     * ^\Qhttps://example.com/api/lookup?key=\E.*?$
     * 
     */
    public String createRegexForUrlTemplate(String url, String placeholder) {
        String transformedUrl = Arrays.stream(StringUtils.splitByWholeSeparator(url, placeholder))
                .map(part -> StringUtils.isBlank(part) ? part : Pattern.quote(part))
                .collect(Collectors.joining(".*?"));
        return "^" + transformedUrl + "$";
    }

    /**
     * Quotes the url and adds a {@code ^} and {@code $}.
     */
    public String createRegexForUrl(String url) {
        return "^" + Pattern.quote(url) + "$";
    }
}