/* Program to reverse a .dat sound file.
 */

import java.io.*;
import java.util.StringTokenizer;

public class Reverse {
    public static void main(String[]args) {
        if (args.length != 2) {
            System.err.println(" Incorrect number of arguments");
            System.err.println(" Usage: ");
            System.err.
                println("\tjava Reverse <input file> <output file>");

            System.exit(1);
        }

        try {
            //
            // Set up the input file to be read, and the output file to be written
            //
            BufferedReader fileIn =
                new BufferedReader(new FileReader(args[0]));
            PrintWriter fileOut =
                new PrintWriter(new
                                BufferedWriter(new FileWriter(args[1])));

            //
            // Read the first line of the .dat file. We want to store the
            // "sample rate" in a variable, but we can ignore the rest 
            // of the line. We step through the first line one token (word)
            // at a time using the StringTokenizer.  The fourth token
            // is the one we want (the sample rate).
            //
            StringTokenizer str;
            String oneLine;
            int sampleRate;
            String strJunk;

            oneLine = fileIn.readLine();
            str = new StringTokenizer(oneLine);
            strJunk = str.nextToken();  // Read in semicolon
            strJunk = str.nextToken();  // Read in "Sample"
            strJunk = str.nextToken();  // Read in "Rate"
            sampleRate = Integer.parseInt(str.nextToken());     // Read in sample rate


            //
            // Read in the file and place values from the second column 
            // in the stack. The first column values are thrown away. 
            // We stop reading if we reach the end of the file.
            //

            DoubleStack s = new DoubleStack();
            String timestep;
            double data;

            while ((oneLine = fileIn.readLine()) != null) {
                str = new StringTokenizer(oneLine);
                timestep = str.nextToken();     // Read in time step value from first column
                data = Double.parseDouble(str.nextToken());     // Read in data value from second column
                s.push(data);
            }


            //
            // Now we are ready to output the data values to output file.
            // But first, we need to output the header line
            // "; Sample Rate <sample rate>"
            //
            fileOut.println("; Sample Rate " + sampleRate);

            // Since the first column consists of numbers which start
            // at 0 and increase by 1/sampleRate every time slice, we'll
            // just use numSteps to recalculate these numbers.
            int numSteps = 0;

            // Finally, we print the values in reverse order (by popping
            // them off the stack). The first column consists of numbers
            // which start at 0 and increase by 1/sampleRate per row, so
            // we'll use numSteps/sampleRate to recalculate the appropriate
            // values. Uniform spacing will be accomplished by printing a tab.

            while (!s.isEmpty()) {
                fileOut.println((double) numSteps / sampleRate + "\t" +
                                s.top());
                s.pop();
                numSteps++;
            }

            //
            // Close the files
            //
            fileIn.close();
            fileOut.close();

        } catch(IOException ioe) {
            System.err.
                println
                ("Error opening/reading/writing input or output file.");
            System.exit(1);
        } catch(NumberFormatException nfe) {
            System.err.println("Error in file format");
            System.exit(1);
        }
    }
}