//NAME: Stella K.
//DATE: Nov 15, 2007
//PURPOSE: Lab on objects, and file i/o, cs111
//WHAT: Reads student data from a file into an array.
//Filters and processes that data, and writes the results 
//back to memory (an output file)
//MODIFICATION HISTORY: 

import java.io.*;

public class WellesleyStudents {
  //Reads the data from file "data.txt" into an array.
  
  //prints out the list of students in a certain section or lab
  //writes the results to a file
  
  //instance vars
  Student[] students;
  int numRecords = 32;
  
  //constructor
  //creates an array and populates it with Student objects, 
  //which are read from the input file
  public WellesleyStudents(String fileIn) throws IOException {
    students = new Student[numRecords]; //create the array
    students = fromFileToArray(fileIn); //populate the array
    //printArray(students); //for testing purposes only
  }
  
  public Student[] getyearGroup(String year){
    //set up an array to hold the results
    Student[] res = new Student[numRecords]; //some of the locations of this array will
    //possibly be left empty at the end of this method
    
    int j = 0; //index into the res array
    for (int i=0; i<students.length; i++) {
      if (year.equals(students[i].getYear())) {
        res[j] = students[i];
        j = j+1;
      }
    }
    return res;
  }
  
  //selects the student instances that match the input lab section.
  //The results are saved in an array, which is returned at the end.
  //input to the method should be in the form "lab03", as an example
  public Student[] getlabGroup(String labSection){
    //set up an array to hold the results
    Student[] res = new Student[numRecords]; //some of the locations of this array will
    int j = 0; //index to the res array
    //possibly be left empty at the end of this method
    for (int i=0; i<students.length; i++) {
      if (labSection.equals(students[i].getLab()) 
            || (students[i].getLab().equals("lab00")) ) {
        res[j] = students[i];
        j = j+1;
      }
    }
    return res;
  }
   
  //Reads the data from the input file into an array.
  //The array is returned at the end.
  public Student[] fromFileToArray(String fileName) throws IOException {
    int i = 0;
    Student[] res = new Student[numRecords];
    BufferedReader reader = new BufferedReader(new FileReader(fileName));
    String line = reader.readLine(); //read the first line of the file
    while (line  != null) {  //line becomes null at end of file
      Student s = new Student(line);
      res[i] = s;
      i++;
      line = reader.readLine(); //read the next line of the file
    }
    reader.close();
    return res;
  }
    
  
  //Writes the input array "input" into a file "output".
  //Each object will be written in one line
  //Only non-null object will be written in the output file.
  //If the "output" file does not exist, it will be created.
  //It overwrites the file
  public void fromArrayToFile(Student[] input, String output) throws IOException {
    int i = 0;
      BufferedWriter writer = new BufferedWriter(new FileWriter(output));
      while (input[i] != null) {  //write only the non-null objects
        String line = input[i].toString();
        writer.write(line + "\n");
        i++;
      }
      writer.close();
  }
  
  //Writes the input array "input" into a file "output".
  //Each object will be written in one line.
  //Each line will be marked with its number line in that file
  //Only non-null object will be written in the output file.
  //If the "output" file does not exist, it will be created.
  //It overwrites the output file
  public void fromArrayToFileLineNum(Student[] input, String output) throws IOException {
    int i = 0;
      BufferedWriter writer = new BufferedWriter(new FileWriter(output));
      while (input[i] != null) {  //write only the non-null objects
        String line = input[i].toString();
        writer.write("/* line " + i + "*/ ");
        writer.write(line + "\n");
        i++;
      }
      writer.close();
  }
  
  //Reads the input file, and outputs it in the console.
  //Just for testing purposes and practice with reading files in Java
  public void fromFileToScreen(String inFile) throws IOException {
      BufferedReader reader = new BufferedReader(new FileReader(inFile));
      String line = reader.readLine(); //read the first line of the file
      while (line != null) {  //line becomes null at end of file
        System.out.println(line);
        line = reader.readLine(); //read the next line of the file
      }
      reader.close();
  }
  
  //Prints the input array, to the console, one object per line.
  //Uses the toString() on the Student objects.
  //Only the non-null objects are printed.
  private void printArray(Student[] a) {
    //System.out.println("**** printing array ****");
    for (int i=0; i<a.length; i++) {
      if (a[i] != null)
        System.out.println(a[i]);  //will be using the toString() on Student
    }
    //System.out.println("********");
  }

  public static void main(String[] args) throws IOException {
    WellesleyStudents ws = new WellesleyStudents(PicOps.getFolder() + "data.txt");
    //ws.fromFileToScreen(PicOps.getFolder() + "data.txt");
    
    Student[] results;

    //System.out.println("Group of students in lab01 *****");
   // results = ws.getlabGroup("lab01");
   
    //System.out.println("Group of students in lab02 *****");
    //results = ws.getlabGroup("lab02");
    
    //System.out.println("Group of students in lab03 *****");
    //results = ws.getlabGroup("lab03");
    
    System.out.println("Group of seniors");
    results = ws.getyearGroup("2008");
    //System.out.println("Group of juniors");
    //results = ws.getyearGroup("2009");
    //System.out.println("Group of sophomors");
    //results = ws.getyearGroup("2010");
    //System.out.println("Group of first years");
    //results = ws.getyearGroup("2011");
    
    ws.printArray(results);
    
    ws.fromArrayToFile(results, PicOps.getFolder() + "out.txt");
    ws.fromArrayToFileLineNum(results, PicOps.getFolder() + "outLines.txt");
  }
}