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contracts...corrections...Student.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.18;

import "@openzeppelin/contracts/access/Ownable.sol";

contract Notes is Ownable {
    struct Student {
        string name;
        uint256 noteBiology;
        uint256 noteMaths;
        uint256 noteFr;
    }

    Student[] private students;
    // mapping(string => Student) studentsmap;
    // string[] names;

    // class => course => addre
    // cours =>
    mapping(string => address) teachers;

    event studentAdded(string _name, address _addr);
    event teacherAdded(string _course, address _addr);

    function addStudent(string memory _name, address _addr) public onlyOwner {
        students.push(Student(_name, 0, 0, 0));
        emit studentAdded(_name, _addr);
    }

    function setTeacher(string memory _course, address _addr) public onlyOwner {
        teachers[_course] = _addr;
        emit teacherAdded(_course, _addr);
    }

    function getStudentFromName(string memory _name)
        private
        view
        returns (uint256)
    {
        for (uint256 i = 0; i < students.length; i++) {
            if (
                keccak256(abi.encodePacked(students[i].name)) ==
                keccak256(abi.encodePacked(_name))
            ) {
                return i;
            }
        }
        return 0;
    }

    function stringsEquals(string memory _string1, string memory _string2)
        private
        pure
        returns (bool)
    {
        bool test;
        if (
            keccak256(abi.encodePacked(_string1)) ==
            keccak256(abi.encodePacked(_string2))
        ) {
            test = true;
        }
        return test;
    }

    function setNote(
        string memory _course,
        string memory _nameStudent,
        uint256 _note
    ) public {
        uint256 idStudent = getStudentFromName(_nameStudent);
        require(
            msg.sender == teachers[_course],
            "you re not the teacher of this student course"
        );
        if (stringsEquals(_course, "biology")) {
            students[idStudent].noteBiology = _note;
        } else if (stringsEquals(_course, "maths")) {
            students[idStudent].noteMaths = _note;
        } else if (stringsEquals(_course, "french")) {
            students[idStudent].noteFr = _note;
        } else {
            revert("type a real course");
        }
    }

    function calculateMoyennePerCourse(string memory _course)
        public
        view
        returns (uint256)
    {
        require(
            msg.sender == teachers[_course],
            "you're not the teacher of this class course"
        );
        uint256 totalNote;
        uint256 totalStudent;

        switch () 

        for (uint256 i = 0; i < students.length; i++) {
            if (stringsEquals(_course, "biology")) {
                totalNote += students[i].noteBiology;
                totalStudent += 1;
            }
            if (stringsEquals(_course, "maths")) {
                totalNote += students[i].noteMaths;
                totalStudent += 1;
            }
            if (stringsEquals(_course, "french")) {
                totalNote += students[i].noteFr;
                totalStudent += 1;
            }
        }
        uint256 moyenne = (totalNote * 100) / totalStudent;
        return moyenne;
    }

    function calculateMoyenneStudent(string memory _name)
        public
        view
        onlyOwner
        returns (uint256)
    {
        uint256 idStudent = getStudentFromName(_name);
        return
            ((students[idStudent].noteBiology +
                students[idStudent].noteMaths +
                students[idStudent].noteFr) * 100) / 3;
    }

    function isPassing(string memory _name)
        public
        view
        onlyOwner
        returns (bool)
    {
        return calculateMoyenneStudent(_name) >= 10;
    }

    function calculateMoyenneGenerale()
        public
        view
        onlyOwner
        returns (uint256)
    {
        uint256 totalNote;
        uint256 totalStudent;
        for (uint256 i = 0; i < students.length; i++) {
            totalNote +=
                students[i].noteBiology +
                students[i].noteMaths +
                students[i].noteFr;
            totalStudent += 3;
        }
        return totalNote / totalStudent;
    }
}