/*
 * 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 freemarker.core;

import freemarker.template.Configuration;
import freemarker.template.utility.StringUtil;

For internal use only; don't depend on this, there's no backward compatibility guarantee at all!
This class is to work around the lack of module system in Java, i.e., so that other FreeMarker packages can
access things inside this package that users shouldn't. 
/**
 * For internal use only; don't depend on this, there's no backward compatibility guarantee at all!
 * This class is to work around the lack of module system in Java, i.e., so that other FreeMarker packages can
 * access things inside this package that users shouldn't. 
 */ 
public final class _CoreStringUtils {

    private _CoreStringUtils() {
        // No meant to be instantiated
    }

    public static String toFTLIdentifierReferenceAfterDot(String name) {
        return backslashEscapeIdentifier(name);
    }

    public static String toFTLTopLevelIdentifierReference(String name) {
        return backslashEscapeIdentifier(name);
    }

    public static String toFTLTopLevelTragetIdentifier(final String name) {
        char quotationType = 0;
        scanForQuotationType: for (int i = 0; i < name.length(); i++) {
            final char c = name.charAt(i);
            if (!(i == 0 ? StringUtil.isFTLIdentifierStart(c) : StringUtil.isFTLIdentifierPart(c)) && c != '@') {
                if ((quotationType == 0 || quotationType == '\\') && (c == '-' || c == '.' || c == ':')) {
                    quotationType = '\\';
                } else {
                    quotationType = '"';
                    break scanForQuotationType;
                }
            }
        }
        switch (quotationType) {
        case 0:
            return name;
        case '"':
            return StringUtil.ftlQuote(name);
        case '\\':
            return backslashEscapeIdentifier(name);
        default:
            throw new BugException();
        }
    }

    private static String backslashEscapeIdentifier(String name) {
        return StringUtil.replace(StringUtil.replace(StringUtil.replace(name, "-", "\\-"), ".", "\\."), ":", "\\:");
    }

    
Returns:
Configuration.CAMEL_CASE_NAMING_CONVENTION, or Configuration.LEGACY_NAMING_CONVENTION or, Configuration.AUTO_DETECT_NAMING_CONVENTION when undecidable./**
     * @return {@link Configuration#CAMEL_CASE_NAMING_CONVENTION}, or {@link Configuration#LEGACY_NAMING_CONVENTION}
     *         or, {@link Configuration#AUTO_DETECT_NAMING_CONVENTION} when undecidable.
     */
    public static int getIdentifierNamingConvention(String name) {
        final int ln = name.length();
        for (int i = 0; i < ln; i++) {
            final char c = name.charAt(i);
            if (c == '_') {
                return Configuration.LEGACY_NAMING_CONVENTION;
            }
            if (isUpperUSASCII(c)) {
                return Configuration.CAMEL_CASE_NAMING_CONVENTION;
            }
        }
        return Configuration.AUTO_DETECT_NAMING_CONVENTION;
    }
    
    // [2.4] Won't be needed anymore
    
A deliberately very inflexible camel case to underscored converter; it must not convert improper camel case
names to a proper underscored name.
/**
     * A deliberately very inflexible camel case to underscored converter; it must not convert improper camel case
     * names to a proper underscored name.
     */
    public static String camelCaseToUnderscored(String camelCaseName) {
        int i = 0;
        while (i < camelCaseName.length() && Character.isLowerCase(camelCaseName.charAt(i))) {
            i++;
        }
        if (i == camelCaseName.length()) {
            // No conversion needed
            return camelCaseName;
        }
        
        StringBuilder sb = new StringBuilder();
        sb.append(camelCaseName.substring(0, i));
        while (i < camelCaseName.length()) {
            final char c = camelCaseName.charAt(i);
            if (isUpperUSASCII(c)) {
                sb.append('_');
                sb.append(Character.toLowerCase(c));
            } else {
                sb.append(c);
            }
            i++;
        }
        return sb.toString();
    }
    
    public static boolean isUpperUSASCII(char c) {
        return c >= 'A' && c <= 'Z';
    }

}