/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package project;

import java.sql.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.ResultSetMetaData;
import java.util.Scanner;
//import java.util.Collections;
import java.util.LinkedList;
import java.util.ListIterator;
//import java.util.List;

/**
 *represents a general blueprint defining state of a person - student, is composed of two other objects  
 * @author ivan
 */

class Student {
    int ID;
    String lastName;
    String firstName;
    String birthday;
    Major major;
    int earnedCredits;
  /**
   * initializes a Student based on user input
   * @param id int corresponding to position in student linkedlist
   * @param lname string last name
   * @param fname string first name
   * @param bday string birthday
   * @param majorKey pointer to Major object
   * @param credits int credits earned
   */  
    Student(int id, String lname, String fname, String bday, Major majorKey, int credits) {
        ID = id;
        lastName = lname;
        firstName = fname;
        birthday = bday;
        major = majorKey; 
        earnedCredits = credits;
        
    }
    /**
     * method on Student instance that forms readable string containing all its member 
     * values; uses chained calls to respective display()on its member objects 
     * @return string containing fields on Student object in readable format 
     */
    public String displayStudent() {
        return "Student ID: "+ID+
                "\nName: "+lastName+", "+firstName+
                "\nBirthdate: "+birthday+
                "\nTotal Credits earned: "+earnedCredits+"\n"+
                major.displayMajor();
                
        
    }
    /**
     * static method on Student class that takes arbitrary Student and returns credit-hours needed to graduate based on their major
     * @param student takes in a Student object
     * @return returns int representing deficit in credits
     */
    public static int creditsNeeded(Student student) {
        
       return student.major.creditHoursReq - student.earnedCredits;
        
       
    }
    
    
}
/**
 * represents a general blueprint defining state of an educational major
 * @author ivan
 */
class Major {
    int ID;
    String name;
    int creditHoursReq;
    DepartmentHead deptHead;
    boolean transfers;
    /**
     * initializes a Major object based on user input
     * @param id int corresponding to index in containing linkedList
     * @param majorName string
     * @param creditHours int hours req to graduate
     * @param headKey pointer to DeptHead object 
     * @param transferrable boolean; are transfers typical 
     */
    Major(int id, String majorName, int creditHours, DepartmentHead headKey, boolean transferrable) {
        ID = id;
        name = majorName;
        creditHoursReq = creditHours;
        deptHead = headKey;
        transfers = transferrable;
        
    }
    /**
     * method on Major instance that forms readable string containing all its member 
     * values; is called in chain when displatStudent() is called
     * @return string containing fields on Major object in readable format 
     */
    public String displayMajor() {
        return "Major ID: "+ID+" "+
                "Major title: "+name+" "+
                "Credits required to graduate: "+creditHoursReq+" "+
                "Transferrable: "+transfers+"\n"+
                deptHead.displayDepartmentHead();
                
                
                
        
    }
}
/**
 * represents a general blueprint defining state of a person heading a department
 * @author ivan
 */
class DepartmentHead {
     
    int ID;
    String lastName;
    String firstName;
    String office;
    String phone;
    String email;
    /**
     * initializes a department head object based on user input
     * @param id int matching index of position n linkedlist
     * @param lname string last name
     * @param fname string first name
     * @param officeLocation string location of office
     * @param phoneNumber string 
     * @param emailAdd string
     */
    DepartmentHead(int id, String lname, String fname, String officeLocation, String phoneNumber, String emailAdd) {
        ID = id;
        lastName = lname;
        firstName = fname;
        office = officeLocation;
        phone = phoneNumber;
        email = emailAdd;
        
    }
    /**
     * method on DepartmentHead instance that forms readable string containing all its member 
     * values; is called last in chain when displatStudent() is called
     * @return string containing fields on DeptHead object in readable format
     */
    public String displayDepartmentHead() {
        return "Faculty ID: "+ID+" "+
               "Name: "+lastName+", "+firstName+" "+
                "Office: "+office+" "+
                "Phone: "+phone+" "+
                "email: "+email;
                
    }
}

/**
 * utility class containing main()
 * @author ivan
 */
public class StudentTracking {
    
    private static String dbURL = "jdbc:derby://localhost:1527/contact;create=true;user=nbuser;password=nbuser";
    private static String tableName = "students";
    // jdbc Connection
    private static Connection conn = null;
    private static Statement stmt = null;

    
    
    
    /**
     * comprises logic of studenttracking program; construction of objects and respective lists happens here, as well as calls to
     * utility and object methods based on user input collected
     * @param args 
     */
    public static void main(String[] args) {
        
        //createConnection();
        
        Scanner scan = new Scanner(System.in);
 
        //creates Student, Major, and DepartmentHead lists    
        LinkedList<Student> studentList = new LinkedList<Student>();
        LinkedList<Major> majorList = new LinkedList<Major>();
        LinkedList<DepartmentHead> deptHeadList = new LinkedList<DepartmentHead>();
        
        //populates 2 lists with references to object components of Student super object and creates 3rd main list of composite Student objects
        deptHeadList.add(new DepartmentHead(deptHeadList.size(), "Knuth", "Donald", "123 Sennot sq", "412-555-9087", "foo@example.com"));
        deptHeadList.add(new DepartmentHead(deptHeadList.size(), "Chalmers", "David", "456 5th Ave", "412-555-5676", "foo@example.com"));
        deptHeadList.add(new DepartmentHead(deptHeadList.size(), "Feynman", "Richard", "789 Poplar Rd", "412-555-7867", "foo@example.com"));
        deptHeadList.add(new DepartmentHead(deptHeadList.size(), "Weinberg", "Steven", "012 Caltech Rd", "412-555-6756", "foo@example.com"));
        
        majorList.add(new Major(majorList.size(), "Physics", 65, deptHeadList.get(2), true));
        majorList.add(new Major(majorList.size(), "Computer Science", 60, deptHeadList.get(0), true));
        majorList.add(new Major(majorList.size(), "Philosophy", 70, deptHeadList.get(1), true));
        majorList.add(new Major(majorList.size(), "Mathematics", 70, deptHeadList.get(3), true));
        
        studentList.add(new Student(studentList.size(), "Smith", "Mary", "01/03/1992", majorList.get(0), 21));
        studentList.add(new Student(studentList.size(), "Adams", "Sara", "06/03/1994", majorList.get(1), 34));
        studentList.add(new Student(studentList.size(), "Jenkins", "Jennifer", "01/28/1991", majorList.get(2), 18));
        studentList.add(new Student(studentList.size(), "Smith", "Emily", "06/29/1991", majorList.get(3), 18));
        
        
        
        //initializes loop variable to give true
        String userResponse = "y";
        
    while(userResponse.equals("y") || userResponse.equals("Y")) {
        
        System.out.println("Press enter to print all students.");
        
        scan.nextLine();
        
        //uses method on studentList to construct its iterator and creates pointer to it 
        ListIterator<Student> iterator = studentList.listIterator();
        
        //while loop using iterator to call displayStudent() on each student object in list
        while (iterator.hasNext()) {
            System.out.println(iterator.next().displayStudent());
            System.out.println();
        }
        
        
        
        System.out.println("Press enter to compute all student credits and average credits earned.");
        
        scan.nextLine();
        
        //pass list of students to compute total and average credits
        System.out.println(getAverageCreditsEarned(studentList));
        
        System.out.println();
        
        System.out.println("Press enter to get highest and lowest credits earned");
        
        scan.nextLine();
        
        //pass list of students to get highest and lowest credits earned
        System.out.println(highLow(studentList));
        
        System.out.println();
        
        //recreate listIterator for studentList so cursor is back at beginning
        iterator = studentList.listIterator();
        
        //while loop using iterator to access all student fields and pass each student to static creditsNeeded()
        //experimented here with alternating calls to next() and previous() on iterator to repeatedly acces same student 
        //instead of using pointer
        while (iterator.hasNext()) {
            System.out.println(iterator.next().firstName+" "+iterator.previous().lastName+" has "+iterator.next().major.name+
                    " declared as a major and has "+Student.creditsNeeded(iterator.previous())+" more credit-hours left to graduate.");
            iterator.next();
        }
        
        //gather user input on whether to create and add new student to list
        System.out.println();
        System.out.println("Would you like to add a student? Y/N");
        userResponse = scan.next();
        
        //gathers userinput for new student fields and constructs a new student and adds to list
        //creates majorList iterator to print index values to inform user input
        if (userResponse.equals("y") || userResponse.equals("Y")) {
            ListIterator<Major> listIterator = majorList.listIterator();
            
            int credits;
            String fname;
            String lname;
            String bday;
            int major;
            System.out.println("Student's first name?");
            fname = scan.next();
            System.out.println("Student's last name?");
            lname = scan.next();
            System.out.println("Birthdate? 00/00/0000");
            bday = scan.next();
            System.out.println("How many credits has this student earned?");
            credits = scan.nextInt();
            System.out.println("What is the student's declard major? Enter corresponding integer");
            while (listIterator.hasNext()) {
                System.out.println(listIterator.next().ID+"...."+listIterator.previous().name);   
                listIterator.next();
            }
            major = scan.nextInt();
            studentList.add(new Student(studentList.size(), lname, fname, bday, majorList.get(major), credits));
            System.out.println("New entry completed. New student has ID "+studentList.getLast().ID);
            
        }
        
        //end of while loop. loop terminates if user inuts anything other than y or Y
        System.out.println("Run again? Y/N");
        userResponse = scan.next();
        
        shutdown();
    }    


        
        
     } 
    
    

    /**
     * iterates through the studentList and computes total and average credits earned of all student objects
     * @param studentList takes in a Student LinkedList as an argument
     * @return returns a String containing the results of the computation
     */
    
    
    public static String getAverageCreditsEarned(LinkedList<Student> studentList){ 
        ListIterator<Student> listIterator = studentList.listIterator();
        
        int totalCredits = 0;
        
		while (listIterator.hasNext()) {
                    totalCredits += listIterator.next().earnedCredits;
		}
                
        return "There are "+studentList.size()+" students with a credit total of "+totalCredits+" and the avg. credits earned is "
                +totalCredits/studentList.size()+".";
        
    
    }
    
    /**
     * iterates through the studentList and computes highest and lowest credits earned of all student objects
     * @param studentList takes in a Student LinkedList as an argument
     * @return returns a String containing the results of the computation 
     */
    public static String highLow(LinkedList<Student> studentList) {
        int highest = 0;
        int lowest = Integer.MAX_VALUE;
        Student currentStudent;
        ListIterator<Student> listIterator;
        
        listIterator = studentList.listIterator();
        
        while (listIterator.hasNext()) {
            currentStudent = listIterator.next();
            if (currentStudent.earnedCredits > highest)
                highest = currentStudent.earnedCredits;
            if (currentStudent.earnedCredits < lowest)
                lowest = currentStudent.earnedCredits;
                
        }
        
        return "most credits earned is: "+highest+" and least credits earned is: "+lowest;
    }
    
    private static void createConnection()
    {
        try
        {
            Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance();
            //Get a connection
            conn = DriverManager.getConnection(dbURL); 
        }
        catch (Exception except)
        {
            except.printStackTrace();
        }
    }
    
    private static void shutdown()
    {
        try
        {
            if (stmt != null)
            {
                stmt.close();
            }
            if (conn != null)
            {
                DriverManager.getConnection(dbURL + ";shutdown=true");
                conn.close();
            }           
        }
        catch (SQLException sqlExcept)
        {
            
        }

    }
    
     
}