/** Name: tdparse
    Description: Top-down parser
    Arguments: Fully distinguished path to a source file to be parsed
    Programmer: Spencer R. Shimko
    Date: 03-25-2003
**/

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

/** Class: tdparse
    Main logical driver for parser
**/

public class tdparse {


    // Begin: main
    public static void main(String arg[]){
		LinkedList i_lines=new LinkedList(); // linked list of input lines
    	LinkedList o_lines; // linked list of output lines

		// if not passed 1 argument quit giving correct usage
        if (arg.length!=1) {
            System.out.println("Usage: java tdparse /path/to/sourcefile");
            System.exit(1);
        } // endif not 1 args

        // setup link list w/ lines from source file
        // the resulting linkedlist in c_lines
        // will be the lines read in from the sourcefile w/ no whitespace
        i_lines=readFile(arg[0]);
		o_lines=parser.parse(i_lines); // start parse stack and syntax checking
		display(o_lines); // display results
	} //end method main

	/* readFile: opens file and reads input
	   Receives: filename, linklist to put source in
	   Returns: link list containing source code
	*/
	private static LinkedList readFile(String file)
	{
    	File s_file = new File(file); // file (sourcefile to be parsed)
        BufferedReader br; // bufferedreader for the file to  be parsed
		LinkedList ll= new LinkedList();
        // make sure file is a legitimate file...
	    if (! s_file.isFile()){
	 	    System.out.println("Error: Source file must exist and be a valid file!");
	        System.exit(1);
	    } // endif not file

        // create input filestream for reading
        try{
        	br = new BufferedReader(new FileReader(s_file));
        	// read from file and assign to ll
		        // eof is reached when readline returns null
		        try { // this catches .getLast excpetion when file is empty
		    	    do{
						//read line into ll
						try { //
							// get the line and trim and replace whitespace
							// and convert to char array for ease of use
							ll.add(br.readLine());
						}
						catch(IOException e)
						{
							System.out.println("Error: Reading from sourcefile!.");
						}
					} while( ll.getLast() != null ); //end until reading from sourcefile
				    Object temp=ll.removeLast(); /// remove null pointer
				}
				catch (NoSuchElementException e){
					System.out.println("Error: Sourcefile appears to be empty!");
					System.exit(1);
		}
        }
        catch(IOException e){
           System.out.println("Error: opening source file!");
           System.exit(1);
        } //end try/catch file open
		return ll;
	} //end method readFile

	/** display: displays link list of results
		receives: ll of results
		returns: nada
	**/

	private static  void display(LinkedList results){
		System.out.println("==========RESULTS==========");
		for (int x=0; x<results.size();x++)
			System.out.println(results.get(x));
	}
} //end class tdparse