Student.kt

// Define the reducer function to update the state of the application based on user intents
fun reduce(state: AppState, intent: UserIntent): AppState {
    return when (intent) {
        is UserIntent.AddStudent -> addStudent(state, intent.student)
        is UserIntent.EditStudent -> editStudent(state, intent.student)
        is UserIntent.DeleteStudent -> deleteStudent(state, intent.student)
    }
}

// Define the data model for a student
data class Student(val name: String, val age: Int, val grade: String)

// Define the state of the application
data class AppState(val students: List<Student>)

// Define the actions that the user can perform
sealed class UserIntent {
    data class AddStudent(val student: Student) : UserIntent()
    data class EditStudent(val student: Student) : UserIntent()
    data class DeleteStudent(val student: Student) : UserIntent()
}

// Define the UI component to display the list of 
// students and handle user inputs
class StudentListView {
    lateinit var presenter: StudentListPresenter
    
    fun render(state: AppState) {
        // Render the list of students on the screen
    }
    
    fun handleUserInput(intent: UserIntent) {
        // Pass the user intent to the presenter to update 
        // the state of the application
        presenter.handleUserIntent(intent)
    }
}

// Define the presenter to handle user inputs and 
// update the state of the application
class StudentListPresenter(private val reducer: (AppState, UserIntent) 
-> AppState) {
    lateinit var view: StudentListView
    var state = AppState(emptyList())
    
    fun handleUserIntent(intent: UserIntent) {
        state = reducer(state, intent)
        view.render(state)
    }
}

// Usage example
fun main() {
    val presenter = StudentListPresenter(::reduce)
    val view = StudentListView()
    presenter.view = view
    view.presenter = presenter
    
    val newStudent = Student("Ye Mon", 18, "F-")
    view.handleUserInput(UserIntent.AddStudent(newStudent))
    
    val updatedStudent = Student("Nyan", 19, "A+")
    view.handleUserInput(UserIntent.EditStudent(updatedStudent))
    
    val deletedStudent = Student("Thet", 20, "A")
    view.handleUserInput(UserIntent.DeleteStudent(deletedStudent))
}


// Define separate functions to handle each type of user intent
fun addStudent(state: AppState, student: Student): AppState {
    return state.copy(students = state.students + student)
}

fun editStudent(state: AppState, student: Student): AppState {
    val updatedStudents = state.students.map { if (it.name == student.name) student else it }
    return state.copy(students = updatedStudents)
}

fun deleteStudent(state: AppState, student: Student): AppState {
    val filteredStudents = state.students.filterNot { it.name == student.name }
    return state.copy(students = filteredStudents)
}