pragma solidity 0.5.1;

contract Course {

    address admin;
    address ManagerContract;
    address instructor;
    int courseNo;
    mapping (int => Marks) student;
    mapping (int => bool) isEnrolled;

    struct Marks{
        int midsem;
        int endsem;
        int attendance;
    }

    constructor(int c, address inst, address adm) public {
        ManagerContract=msg.sender;
        admin=adm;
        instructor=inst;
        courseNo=c;
    }

    function kill() public{
        //The admin has the right to kill the contract at any time.
        //Take care that no one else is able to kill the contract
        assert(msg.sender == admin);
        selfdestruct(msg.sender);
    }

    function enroll(int rollNo) public {
        //This function can only be called by the ManagerContract
        //Enroll a student in the course if not already registered
        require(msg.sender==ManagerContract,"This function can only be called by the ManagerContract");
        student[rollNo].midsem=0;
        student[rollNo].endsem=0;
        student[rollNo].attendance=0;
        isEnrolled[rollNo]=true;
    }

    function markAttendance(int rollNo) public{
        //Only the instructor can mark the attendance
        //Increment the attendance variable by one
        //Make sure the student is enrolled in the course
        require(instructor==msg.sender,"Not the instructor");
        require(isEnrolled[rollNo],"Student not enrolled");
        student[rollNo].attendance++;
    }

    function addMidSemMarks(int rollNo, int marks) public{
        //Only the instructor can add midsem marks
        //Make sure that the student is enrolled in the course
        require(instructor==msg.sender,"Not the instructor");
        require(isEnrolled[rollNo],"Student not enrolled");
        require(marks>=0 && marks<=100,"Marks should be between 0-100");
        student[rollNo].midsem=marks;

    }

    function addEndSemMarks(int rollNo, int marks) public{
        //Only the instructor can add endsem marks
        //Make sure that the student is enrolled in the course
        require(instructor==msg.sender,"Not the instructor");
        require(isEnrolled[rollNo],"Student not enrolled");
        require(marks>=0 && marks<=100,"Marks should be between 0-100");
        student[rollNo].endsem=marks;

    }

    function getMidsemMarks(int rollNo) public view returns(int) {
        //Can only be called by the ManagerContract
        //return the midSem, endSem and attendance of the student
        //Make sure to check the student is enrolled
        require(ManagerContract==msg.sender,"Not sufficient rights");
        require(isEnrolled[rollNo],"Student not enrolled");
        int p=student[rollNo].midsem;
        return(p);
    }

    function getEndsemMarks(int rollNo) public view returns(int) {
        //Can only be called by the ManagerContract
        //return the midSem, endSem and attendance of the student
        //Make sure to check the student is enrolled
        require(ManagerContract==msg.sender,"Not sufficient rights");
        require(isEnrolled[rollNo],"Student not enrolled");
        int p=student[rollNo].endsem;
        return(p);
    }

    function getAttendance(int rollNo) public view returns(int) {
        //Can only be called by the ManagerContract
        //return the midSem, endSem and attendance of the student
        //Make sure to check the student is enrolled
        require(ManagerContract==msg.sender,"Not sufficient rights");
        require(isEnrolled[rollNo],"Student not enrolled");
        int p=student[rollNo].attendance;
        return(p);
    }

    function isEnroll(int rollNo) public view returns(bool){
        //Returns if a roll no. is enrolled in a particular course or not
        //Can be accessed by anyone
        return(isEnrolled[rollNo]);
    }

    function getinstructor() public view returns(address) {
        require(ManagerContract==msg.sender,"Not sufficient rights");
        address p=instructor;
        return(p);
    }
}