/*
 *  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
 *
 *    https://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.grails.web.json.parser;

/**
 * @author Siegfried Puchbauer
 *
 * Adapted from the Google GSON Parser http://google-gson.googlecode.com/
 */
final class StringUnmarshaller {

    private StringUnmarshaller() {
    }

    static String unmarshall(String str) {
        str = str.substring(1, str.length() - 1);

        int len = str.length();
        StringBuilder sb = new StringBuilder(len);
        int i = 0;
        while (i < len) {
            char c = str.charAt(i);
            ++i;
            if (c == '\\') {
                char c1 = str.charAt(i);
                ++i;
                if (c1 == 'u') { // This is a unicode escape
                    int codePoint = getCodePoint(str, i);
                    sb.appendCodePoint(codePoint);
                    i += 4;
                }
                else {
                    char escapedChar = getEscapedChar(str, c1);
                    sb.append(escapedChar);
                }
            }
            else {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    private static int getCodePoint(String str, int i) {
        String s = str.substring(i, i + 4);
        return Integer.parseInt(s, 16);
    }

    private static char getEscapedChar(String str, char c) {
        switch (c) {
            case 'n': return '\n';
            case 'b': return '\b';
            case 'f': return '\f';
            case 't': return '\t';
            case 'r': return '\r';
            case '\"': return '\"';
            case '\'': return '\'';
            case '\\': return '\\';
            case '/': return '/';
            default: throw new IllegalStateException("Unexpected character: " + c + " in " + str);
        }
    }
}
