import org.apache.tools.ant.*;
import org.apache.tools.ant.taskdefs.*;
import java.util.*;
import java.io.*;
import java.util.regex.*;


public class RegexSearchReplace extends Task {
	private File file = null;
	private String pattern = null;
	private String replacement = null;
	

	/**
	 * for testing
	 */
	public static void main( String[] args ) {
		RegexSearchReplace rsr = new RegexSearchReplace();
		rsr.setFile(new File (args[0]));
		rsr.setPattern(args[1]);
		rsr.setReplacement(args[2]);

		rsr.execute();

	}

	public void execute() {

		if ( file == null ) {
			throw new BuildException( "Error - No file specified !!" );
		}

		if ( pattern == null ) {
			throw new BuildException( "Error - No pattern specified !!" );
		}

		if (replacement == null) {
			replacement = "";
		}


		//create the output stream
		BufferedWriter out = null;
		File temp = null;
		try {
			// Create temp file.
			temp = File.createTempFile("rsr", ".tmp");

			// Delete temp file when program exits.
			temp.deleteOnExit();

			// Write to temp file
			out = new BufferedWriter(new FileWriter(temp));

		} catch (IOException e) {}


		//create the input stream
		BufferedReader in = null;
		try {
			in = new BufferedReader(new FileReader( file ));
		} catch ( Exception e ) {}

		//pass the file through, searching and replacing
		String line;
		try {
			while ( (line = in.readLine()) != null ) {
				line = line.replaceAll( pattern, replacement);
				out.write(line);
				out.newLine();
			}
			//close them both up
			in.close();
			out.close();

		} catch ( Exception e ) {
			e.printStackTrace();
		}



		//copy the new file (temp) over the original
		try {
			InputStream i = new FileInputStream(temp);
			OutputStream o = new FileOutputStream(file);

			// Transfer bytes from in to out
			byte[] buf = new byte[1024];
			int len;
			while ((len = i.read(buf)) > 0) {
			   o.write(buf, 0, len);
			}

			//close them up
			i.close();
			o.close();
		} catch ( Exception e ) {}
		
	}

   
	public void setFile(File file) {
			this.file = file;
	}

	public void setPattern(String pattern) {
			this.pattern = pattern;
	}

	public void setReplacement(String replacement) {
			this.replacement = replacement.replaceAll( "\\", "\\\\" );
	}


}