CaseFold.java

import org.apache.commons.cli.*;
import java.io.*;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

public class CaseFold
{
    private static final String[] lowerWords = {"a", "an", "the", "as", "at", "by", "for", "in", "of", "off", "on",
            "per", "to", "up", "via", "and", "but", "if", "nor", "or", "so", "yet"};
    
    public static void main(String[] args)
    {
        Locale locale = Locale.getDefault();

        // load resources from disk for current locale
        ResourceBundle resources = null;
        try {
            resources = ResourceBundle.getBundle("casefold", locale);
        }
        // error for incomplete language
        catch (MissingResourceException err)
        {
            String error404 = "This content is not available in your region.\n هذا المحتوى غير متوفر في منطقتك.\n " +
                    "Deze inhoud is niet beschikbaar in uw regio.\n Ce contenu n'est pas disponible dans votre région." +
                    "\n Dieser Inhalt ist in Ihrer Region nicht verfügbar.\n Questo contenuto non è disponibile nella " +
                    "tua regione.\n Este contenido no está disponible en su región.\n " +
                    "Этот контент недоступен в вашем регионе.\n このコンテンツはお住まいの地域ではご利用いただけません。";

            System.err.println(error404);
            System.exit(404);
        }

        // get resource strings
        String upperString = resources.getString("upper");
        String lowerString = resources.getString("lower");
        String sentenceString = resources.getString("sentence");
        String titleString = resources.getString("title");
        String helpString = resources.getString("help");
        String desc = resources.getString("description");
        String error1 = resources.getString("err1");
        String error2 = resources.getString("err2");
        String error3 = resources.getString("err3");
        String error4 = resources.getString("err4");

        // configure command-line options
        Options options = new Options();
        options.addOption("u", "upper", false, upperString);
        options.addOption("l", "lower", false,
                lowerString);
        options.addOption("s", "sentence", false,
                sentenceString);
        options.addOption("t", "title", false,
                titleString);
        options.addOption("h", "help", false, helpString);

        // parse args using the above options parser
        CommandLine input = null;
        try
        {
            CommandLineParser parser = new DefaultParser();
            input = parser.parse(options, args);
        }
        catch (ParseException err)
        {
            System.err.println(error2 + err.getMessage());
            System.exit(2);
        }

        // check command option
        String option = null;
        if (input.hasOption("h"))
        {
            // automatically generate the help statement
            HelpFormatter formatter = new HelpFormatter();
            formatter.printHelp("CaseFold", desc, options, "", true);
            System.exit(0);
        }
        else if (input.hasOption("u"))
        {
            // uppercase option
            option = "u";
        }
        else if (input.hasOption("l"))
        {
            // lowercase option
            option = "l";
        }
        else if (input.hasOption("s"))
        {
            // sentence case option
            option = "s";
        }
        else if (input.hasOption("t"))
        {
            // title case option
            option = "t";
        }
        else
        {
            System.err.println(error1);
            System.exit(1);
        }

        // get remaining arguments
        String[] inputArray = input.getArgs();

        // Read text from the input file or user input.
        StringBuilder text = new StringBuilder();

        // input #1
        if (inputArray.length == 1)
        {

            // get file name
            String fileName = inputArray[0];
            try
            {
                BufferedReader reader = new BufferedReader(new FileReader(fileName));
                String line = reader.readLine();
                text.append(line);
                while ((line = reader.readLine()) != null)
                {
                    text.append("\n").append(line);
                }
                reader.close();
            }
            catch(FileNotFoundException err)
            {
                System.err.println(error4);
                System.exit(4);
            }
            catch (IOException err)
            {
                System.err.println("Error reading file. Cause: " + err.getMessage());
                err.printStackTrace();
                System.exit(3);
            }
        }
        // input #2
        else
        {
            // create reader over input
            BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));

            // get file name
            try
            {
                if (System.in.available() != 0)
                {
                    BufferedReader reader = new BufferedReader(inputReader);
                    String line = reader.readLine();
                    text.append(line);
                    while ((line = reader.readLine()) != null)
                    {
                        text.append("\n").append(line);
                    }
                    reader.close();
                }
                else
                {
                    // no file
                    System.err.println(error4);
                    System.exit(4);
                }
            }
            catch (IOException err)
            {
                System.err.println(error3 + err.getMessage());
                err.printStackTrace();
                System.exit(3);
            }
        }

        // Perform the selected case conversion
        StringBuilder convertedString = new StringBuilder();

        // check for empty file
        if (text.toString().equals("null"))
        {
            System.exit(0);
        }

        switch (option)
        {
            // Upper case
            case "u" -> convertedString.append(text.toString().toUpperCase());

            // Lower case
            case "l" -> convertedString.append(text.toString().toLowerCase());

            // Title case
            case "t" ->
            {
                boolean convertNextToUpper = true;
                char[] charArray = text.toString().toCharArray();
                
                // loop across all characters
                for (int i = 0; i < charArray.length; i++)
                {
                    char ch = charArray[i];
                    if (ch == ' ')
                    {
                        boolean lowerWord = false;
                        // check if non-capitalize word
                        for (String word : lowerWords)
                        {
                            // check if lower word already found
                            if (lowerWord)
                            {
                                // end check
                                break;
                            }

                            // continue checking
                            lowerWord = true;
                            for (int x = 0; x < word.length(); x++)
                            {
                                char letter = Character.toLowerCase(charArray[(i + 1) + x]);
                                char wordLetter = word.charAt(x);
                                if (letter != wordLetter)
                                {
                                    lowerWord = false;
                                    break;
                                }
                            }
                        }

                        if (!lowerWord)
                        {
                            convertNextToUpper = true;
                        }
                    }
                    else if (ch == '\n')
                    {
                        convertNextToUpper = true;
                    }
                    else if (convertNextToUpper)
                    {
                        ch = Character.toUpperCase(ch);
                        convertNextToUpper = false;
                    }
                    else
                    {
                        ch = Character.toLowerCase(ch);
                    }
                    convertedString.append(ch);
                };
            }

            // Sentence case
            case "s" ->
            {
                boolean isNewSentence = true;
                for (char ch : text.toString().toCharArray())
                {
                    if (isNewSentence && Character.isLetter(ch))
                    {
                        ch = Character.toUpperCase(ch);
                        isNewSentence = false;
                    }
                    else
                    {
                        ch = Character.toLowerCase(ch);
                    }

                    if (ch == '.' || ch == '?' || ch == '!')
                    {
                        isNewSentence = true;
                    }

                    convertedString.append(ch);
                }
            }
        }

        // return converted text
        System.out.print(convertedString);
        System.exit(0);
    }
}