/* Copyright (C) 2013 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 * 
 * AutomataLib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 * 
 * AutomataLib 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 GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with AutomataLib; if not, see
 * http://www.gnu.de/documents/lgpl.en.html.
 */
package net.automatalib.commons.util.strings;

import java.io.IOException;
import java.util.regex.Pattern;

/**
 * Misceallanous utility functions for {@link String}s.
 * 
 * @author Malte Isberner <malte.isberner@gmail.com>
 */
public abstract class StringUtil {
        
        private static final String IDENTIFIER_REGEX = "[a-zA-Z_]\\w*";
        
        private static Pattern identifierPattern = null;
        
        private StringUtil() {}
        

        public static Pattern getIdentifierPattern() {
                if(identifierPattern == null)
                        identifierPattern = Pattern.compile(IDENTIFIER_REGEX);
                return identifierPattern;
        }
        
        public static String enquote(String s) {
                StringBuilder sb = new StringBuilder(s.length() + 2);
                try {
                        enquote(s, sb);
                }
                catch(IOException e) {}
                return sb.toString();
        }
        
        public static void enquote(String s, Appendable a) throws IOException {
                a.append('"');
                escapeQuotes(s, a);
                a.append('"');
        }
        
        public static void enquoteIfNecessary(String s, Appendable a) throws IOException {
                if(!getIdentifierPattern().matcher(s).matches())
                        enquote(s, a);
                else
                        a.append(s);
        }
        
        public static void enquoteIfNecessary(String s, Appendable a, Pattern valid)
                        throws IOException {
                if(!valid.matcher(s).matches())
                        enquote(s, a);
                else
                        a.append(s);
        }
        
        public static void enquoteIfNecessary(String s, Appendable a,
                        Pattern valid,
                        Pattern exception) throws IOException {
                if(!valid.matcher(s).matches() || exception.matcher(s).matches())
                        enquote(s, a);
                else
                        a.append(s);
        }
        
        public static String unquote(String s) {
                StringBuilder sb = new StringBuilder(s.length() - 2);
                try {
                        unquote(s, sb);
                }
                catch(IOException e) {}
                return sb.toString();
        }
        
        public static void unquote(String s, Appendable a) throws IOException {
                if(s.charAt(0) != '"' || s.charAt(s.length()-1) != '"')
                        throw new IllegalArgumentException("Argument to StringUtil.unquote() must begin and end with a double quote ('\"').");
                unescapeQuotes(s.substring(1, s.length()-1));
        }
        
        /**
         * Unescapes escaped double quotes in a string, i.e.
         * replaces <code>\"</code> by <code>"</code> and
         * <code>\\</code> by <code>\</code>.
         * 
         * @param s the string in which to unescape double quotes.
         * @return the unescaped string.
         */
        public static String unescapeQuotes(String s) {
                StringBuilder sb = new StringBuilder(s.length());
                try {
                        unescapeQuotes(s, sb);
                }
                catch(IOException e) {}
                return sb.toString();
        }
        
        public static void unescapeQuotes(String s, Appendable a) throws IOException {
                int eos = s.length() - 1;
                for(int i = 0; i < eos; i++) {
                        char c = s.charAt(i);
                        if(c == '\\') {
                                c = s.charAt(++i);
                                if(c != '"' && c != '\\')
                                        a.append('\\');
                        }
                        a.append(c);
                }
                
                a.append(s.charAt(eos));
        }

        /**
         * Escapes double quotes in a string. Effectively, <code>"</code> is
         * replaced by <code>\"</code> and <code>\</code> is replaced by
         * <code>\\</code>.
         * 
         * @param s the string to escape.
         * @return the escaped string.
         */
        public static String escapeQuotes(String s) {
                StringBuilder sb = new StringBuilder(s.length());
                try {
                        escapeQuotes(s, sb);
                }
                catch(IOException e) {}
                return sb.toString();
        }
        
        public static void escapeQuotes(String s, Appendable a) throws IOException {
                for(int i = 0; i < s.length(); i++) {
                        char c = s.charAt(i);
                        
                        if(c == '\\' || c == '"')
                                a.append('\\');
                        a.append(c);
                }
        }
        
        
        public static void appendObject(Appendable a, Object obj) throws IOException {
                if(obj instanceof Printable)
                        ((Printable)obj).print(a);
                else
                        a.append(String.valueOf(obj));
        }
        
        public static void appendArray(Appendable a, Object[] array, String sepString) throws IOException {
                boolean first = true;
                
                for(Object o : array) {
                        if(first)
                                first = false;
                        else
                                a.append(sepString);
                        appendObject(a, o);
                }
        }
        
        public static void appendArrayEnquoted(Appendable a, Object[] array, String sepString) throws IOException {
                boolean first = true;
                
                for(Object o : array) {
                        if(first)
                                first = false;
                        else
                                a.append(sepString);
                        enquote(String.valueOf(o), a);
                }
        }
        
        public static void appendIterable(Appendable a, Iterable<?> it, String sepString) throws IOException {
                boolean first = true;
                
                for(Object o : it) {
                        if(first)
                                first = false;
                        else
                                a.append(sepString);
                        appendObject(a, o);
                }
        }
        
        public static void appendIterableEnquoted(Appendable a, Iterable<?> it, String sepString) throws IOException {
                boolean first = true;
                
                for(Object o : it) {
                        if(first)
                                first = false;
                        else
                                a.append(sepString);
                        if(o == null)
                                a.append("null");
                        else
                                enquote(o.toString(), a);
                }
        }
}