/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.johnzon.core;

public final class JsonPointerUtil {
    private JsonPointerUtil() {
        // no-op
    }

    /**
     * Transforms "~" to "~0" and then "/" to "~1"
     */
    public static String encode(String s) {
        if (s == null || s.isEmpty()) {
            return s;
        }
        return replace(replace(s, "~", "~0"), "/", "~1");
    }

    /**
     * Transforms "~1" to "/" and then "~0" to "~",
     */
    public static String decode(String s) {
        if (s == null || s.length() == 0) {
            return s;
        }
        return replace(replace(s, "~1", "/"), "~0", "~");
    }

    // regex have too much overhead (Matcher + Pattern) at runtime even when precompiled
    private static String replace(final String src, final String from, final String to) {
        if (src.isEmpty()) {
            return src;
        }
        final int start = src.indexOf(from);
        if (start >= 0) {
            return src.substring(0, start) + to + replace(src.substring(start + from.length()), from, to);
        }
        return src;
    }
}
