/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.com/javaexamples2.
 */
package com.davidflanagan.examples.i18n;
import java.io.*;

/** A program to convert from one character encoding to another */
public class ConvertEncoding {
    public static void main(String[] args) {
        String from = null, to = null;
        String infile = null, outfile = null;
        for(int i = 0; i < args.length; i++) { // Parse command-line arguments.
            if (i == args.length-1) usage();   // All args require another.
            if (args[i].equals("-from")) from = args[++i];
            else if (args[i].equals("-to")) to = args[++i];
            else if (args[i].equals("-in")) infile = args[++i];
            else if (args[i].equals("-out")) outfile = args[++i];
            else usage();
        }

        try { convert(infile, outfile, from, to); }  // Attempt conversion.
        catch (Exception e) {                        // Handle exceptions.
            LocalizedError.display(e);  // Defined at the end of this chapter.
            System.exit(1);
        }
    }

    public static void usage() {
        System.err.println("Usage: java ConvertEncoding <options>\n" +
			   "Options:\n\t-from <encoding>\n\t" + 
			   "-to <encoding>\n\t" +
			   "-in <file>\n\t-out <file>");
        System.exit(1);
    }

    public static void convert(String infile, String outfile,
			       String from, String to)
              throws IOException, UnsupportedEncodingException
    {
        // Set up byte streams.
        InputStream in;
        if (infile != null) in = new FileInputStream(infile);
        else in = System.in;
        OutputStream out;
        if (outfile != null) out = new FileOutputStream(outfile);
        else out = System.out;
	
        // Use default encoding if no encoding is specified.
        if (from == null) from = System.getProperty("file.encoding");
        if (to == null) to = System.getProperty("file.encoding");
	
        // Set up character streams.
        Reader r = new BufferedReader(new InputStreamReader(in, from));
        Writer w = new BufferedWriter(new OutputStreamWriter(out, to));
	
        // Copy characters from input to output.  The InputStreamReader
        // converts from the input encoding to Unicode, and the
        // OutputStreamWriter converts from Unicode to the output encoding.
        // Characters that cannot be represented in the output encoding are
        // output as '?'
        char[] buffer = new char[4096];
        int len;
        while((len = r.read(buffer)) != -1)  // Read a block of input.
            w.write(buffer, 0, len);         // And write it out.
        r.close();                           // Close the input.
        w.close();                           // Flush and close output.
    }
}