//File:  cat.java
//CS 471 - Operating Systems Project
//Dennis Pereira, Ely Soto, John Cavalieri

//The cat command takes files as arguments and concatenates them
//the output is printed to the STDOUT, unless otherwise specified by an
//output redirection
//if the cat command is given two filenames as arguments, it will open both files
//append them together and display them or output them to the desired file

import  java.io.*;

public class cat extends VMachine
{
    public cat()
    {
    }
    
    public void run()
    {
        String input = "";
        String line = "";
        BufferedReader inputStream = null;
        
	//if there are no args, then wait for the user to enter something
        if(args.length == 0)
        {
            try
            {
                input = sysapi.Read(IN);
            }
            catch(IOException ex)
            {
                System.out.println(ex);
            }
        }

	//for each input argument
        for(int i = 0; i < args.length || input.compareTo("") != 0; i++)
        {
            try
            {
                
                if(i<args.length)
                {
                    input = args[i];
                }
                
		//open the file
                inputStream = new BufferedReader(new FileReader(sysapi.findUser(owner).getcurrentPath() + input));
                
		//read each line
                line = inputStream.readLine();
                
		//remove white space from ends of lines
		//and write to new file, or to STDOUT
                while (line != null)
                {
                    sysapi.Write(OUT,line.trim() + "\n");
                    line = inputStream.readLine();
                }
		//close the input file
                inputStream.close();

		//proceed to the next input file
                if(i>=args.length)
                {
                    input = sysapi.Read(IN);
                }
                else
                {
                    input = "";
                }
            }
            
		//if the file is not found then proceed without that file
            catch(FileNotFoundException e)
            {
                try
                {
			//tell user, the file is not found
                    sysapi.Write(OUT,"File not found.\n");
			//reduce the size of the arg list
                    if(i == args.length-1)
                    {
                        break;
                    }
                    else if(args.length > 0)
                    {
			//use the next file in the argument list
                        i++;
                        input = args[i];
                    }
                    else
                    {
                        input = sysapi.Read(IN);
                        if(input.compareTo("")==0)
                        {
                            break;
                        }
                    }
                }
                catch(Exception ex)
                {
                    System.out.println(ex);
                    break;
                }
            }
		//if there is something wrong with the file
            catch(IOException ioex)
            {
                System.out.println(ioex);
                try
                {
			//tell the user about the problem
                    sysapi.Write(OUT,"Error reading from file.\n");
                    break;
                }
                catch(Exception ex)
                {
                    System.out.println(ex);
                }
            }
            catch(Exception e3)
            {
                System.out.println(e3);
                break;
            }
            
        }
        sysapi.Exit(vmh,owner);
    }
}