package studentDB;
import java.io.*;
import java.util.*;
/**
 *	Helper class used to read files containing student
 *	data bases.  This class assumes that student data bases
 *	are text files containing lines of the following form:
 *
 *	<pre>line ::= {ugStudent} {gradStudent} {course}
 *	ugStudent ::= "undergrad" "+" name "+" studentNumber
 *	gradStudent ::= "grad" "+" name "+" studentNumber "+" thesisTitle
 *	course ::= "course" "+" title { "+" studentNumber }</pre>
 */
public class StudentDBFile {
    //  The file we're reading from is represented as
    //  a buffered reader.
    BufferedReader db;

    /**
     *	Opens a student data base located in the given file.
     */
    public StudentDBFile (String fileName) {
	try {
	    db = new BufferedReader (new FileReader (fileName));
	} catch (FileNotFoundException e) {
	    System.out.println ("File " + fileName + " does not exist");
	    System.exit (1);
	}
    }

    /**
     *	Retrieves the next line of the student data base, split into
     *	tokens.  For example, the line:
     *
     *		undergrad+Keith Richards+123
     *
     *	would be returned as an array of three strings:
     *
     *		["undergrad", "Keith Richards", "123"]
     *
     *	If the file has been completely read, then null is returned.
     */
    public String[] getNextLine () {
	String line = null;
	try {
	    line = db.readLine();
	} catch (IOException e) {
	    System.out.println ("Error reading from data base");
	}

	//  If we have reached end of file, return null
	if (line == null) return null;
	
	//  Break the line into tokens
	//  We create a string tokenizer to deliver the tokens,
	//  and extract the tokens into an array.
	StringTokenizer s = new StringTokenizer (line, "+");
	String[] tokens = new String [s.countTokens()];

	for (int i=0; i<tokens.length; i++) {
	    tokens [i] = s.nextToken();
	}

	return tokens;
    }
}