//Dennis Version of parser
import  java.io.*;
import java.util.*;

//class to store the elements of a command line
class Command {
    public String command="";
    public String args="";
    public int in_flag =0;
    public int out_flag=0;
    public String input="";
    public String output="";
}


//array of commands to hold in case of piping
class CommandArray {
	public Vector Commands = new Vector(3,1);
	public int count = 0;
	//adds a new command to the list	
	public void Append(Command nCommand){
		Commands.addElement(nCommand);
		count++;
	}
}


//the guts of the parser
public class Parser extends WorkerThread {
//-------------------------------
//checker functions - look for identifiers, input, output, and pipes

	//check to see if p is a command
	public boolean isIdentifier(String p) {
		int len = p.length();
		for (int i=0; i<len; i++ ) {
			char c = p.charAt(i);
			if ( ! Character.isLetterOrDigit( c ) && c != '.' && c!='/'){
				return false;
			}
		}
		return true;
    	}

	//check to see if p is input redirection
    	public boolean isInputRedirect(String p) {
		if (p.charAt(0)=='<') {
	    		return true;
		}
		return false;
    	}

	//check to see if p is output redirection
	public boolean isOutputRedirect(String p) {
		if(p.charAt(0)=='>') {
			return true;
		}
		return false;
	}

	//check to see if p is a pipe
	public boolean isPipe(String p){
		if(p.charAt(0)=='|') {
			return true;
		}
		return false;
    	}

//-------------------------------------------------
//below is the parse function

	public CommandArray Parse( String lineToParse ) throws Exception {
		//declarations
 		int state = 0;
		int xstate = 0;
		int vmcount = 0;
		int pipecount = 0;
		boolean gotToken = false;
		String t ="";
		boolean expecting = true;
		boolean done = false;
		boolean input_func = false;
		Command currentCommand =new Command();
		CommandArray cmd_list = new CommandArray();


		System.out.println("\nThis is the line to be Parsed: " + lineToParse + "\n");
		StringTokenizer tokens = new StringTokenizer(lineToParse);
		//check the line and continue while there is text on the line
		NEXT:while (gotToken || tokens.hasMoreTokens()) {
		    if (!gotToken){
			t = tokens.nextToken();
		    }
		    gotToken = false;
		    if (done){
			throw(new Exception("Unexpected Continuation of Line"));
		    }

	//switch on states
	switch (state){

	    case 0:
		//state for command
		//this must be an identifier to a command
 		if (isIdentifier(t)) {
		    //we have a command
		    currentCommand.command=t;
		    vmcount ++;
		    System.out.println("create virtual machine vm" + vmcount + ":  " + t);
		    state = 1;
    		}
		else {
		    //if not an Identifier (a letter followed by letters or digits)	
		    //error
 		    throw(new Exception("Command Expected. Found:" + t));
		}
		expecting = false;
		continue NEXT;

	    case 1:
 		//could be: inputredir, outputredir, pipe, arguement, or nothing
		//check for input redirect
		if (isInputRedirect(t)){
		    xstate = state;
		    state=2;
		    expecting = true;
		    if (t.length()>1) {
			t = t.substring(1);
			gotToken = true;
			continue NEXT;
		    }
		    else {
			gotToken = false;
 			continue NEXT;
		    }
		//check for output redirect
		} else if(isOutputRedirect(t)) {
 		    xstate = state;
		    state=4;
		    expecting = true;
		    if (t.length()>1){
			t = t.substring(1);
			gotToken = true;
			continue NEXT;
		    }
		    else {
			gotToken = false;
 			continue NEXT;
		    }
		//check for a pipe
		} else if(isPipe(t)){
		    pipecount++;
		    System.out.println("create pipe p" + pipecount);
		    xstate = state;
		    state=6;
		    expecting = true;
		    cmd_list.Append(currentCommand);
		    currentCommand = new Command();
		    if (t.length()>1){
			t = t.substring(1);
			gotToken = true;
			continue NEXT;
		    } else {
			gotToken = false;
 			continue NEXT;
		    }
		} else {
		    //return an argument in command.args
		    expecting = false;
		    currentCommand.args = currentCommand.args +" "+ t;
		}
		System.out.println("In State 1:" + t);
		continue NEXT;

	    case 2: 
		//state for input redirect
		state = xstate;
		//check to make sure you only accept one input redirect
		if (isIdentifier(t) && !(input_func)){
		    currentCommand.input = t;
		    currentCommand.in_flag = 1;
		    expecting = false;
		    input_func = true;
	     	    System.out.println("set vm" + vmcount + ".IN = open file: " + t);
		} else if (input_func) {
		      //error
			throw(new Exception("Unexpected Continuation of Line"));
		}
		else {
		    //error
		    throw (new Exception( "File Name Expected. Found:"+t ));
		}		continue NEXT;

	    case 3: 
		//state for after input redirect - can be either pipe or output redirect
	  	xstate = state;
		if(isOutputRedirect(t)) {
 		    state=4;
		    expecting = true;
		    if (t.length()>1){
			t = t.substring(1);
			gotToken = true;
			continue NEXT;
		    } 
		    else {
			gotToken = false;
 			continue NEXT;
		    }
		} 
		else if(isPipe(t)){
		    System.out.println("create pipe p" + pipecount++ );
		    state=6;
		    expecting = true;
		    cmd_list.Append(currentCommand);
		    currentCommand = new Command();
		    if (t.length()>1){
			t = t.substring(1);
			gotToken = true;
			continue NEXT;
		    } 
                else {
			gotToken = false;
 			continue NEXT;
		    }
		} 
		//dumb way to catch the error, but using an else does not work
		//gives error that System.out line below is unreachable
		if (!isPipe(t) && !isOutputRedirect(t)) {
		    //error
		    throw(new Exception("File Name Expected. Found:"+t));
		}
		continue NEXT;

	    case 4: 
		//state for output redirection
		state = xstate;
		if (isIdentifier(t)){
		    currentCommand.output = t;
		    currentCommand.out_flag = 1;
		    expecting = false;
		    done = true;
		    System.out.println("set vm" + vmcount + ".OUT = creator's OUT");
		} else {
		    //error
		    throw(new Exception("File Name Expected. Found:"+t));
		}
		continue NEXT;

	    case 5:
 		//empty state - hopefully will remove in future
		System.out.println("In State 5:" + t);
		continue NEXT;

	    case 6:
		System.out.println("set vm" + vmcount + ".OUT = p" + pipecount + ".IN");
		if (isIdentifier(t)){
		    //a command has been recognized
		    currentCommand.command=t;
		    state = 3;
		    expecting = false;
		    vmcount++;
		    System.out.println("create virtual machine vm" + vmcount + ":  " + t);
		    System.out.println("set p" + pipecount + ".OUT = vm" + vmcount + ".IN");
		} else {
		    //error
		    throw(new Exception("Command Expected. Found:"+t));
		}
		continue NEXT;
	    default:
 		System.out.println("In State x:" + t);
		break;
	    }
	    if ( expecting ){
	    	throw(new Exception("Unexpected end of line"));
	    }
	} //end NEXTswitch
	return cmd_list;
   } //end parse
} //end class