Completed edit functionality for examinations in the calendar view.

src/main/java/org/example/se302/controller/ExamEditDialog.java

@@ -0,0 +1,372 @@
+package org.example.se302.controller;
+
+import javafx.geometry.Insets;
+import javafx.scene.control.*;
+import javafx.scene.layout.*;
+import javafx.scene.paint.Color;
+import javafx.scene.text.Font;
+import javafx.scene.text.FontWeight;
+import javafx.util.StringConverter;
+import org.example.se302.model.*;
+import org.example.se302.service.ConstraintValidationService;
+import org.example.se302.service.ConstraintValidationService.ValidationResult;
+import org.example.se302.service.DataManager;
+
+import java.util.Optional;
+
+/**
+ * Dialog for editing an exam assignment.
+ * Provides real-time constraint validation with detailed violation info.
+ */
+public class ExamEditDialog extends Dialog<ExamEditDialog.EditResult> {
+
+    private final String courseCode;
+    private final ScheduleState scheduleState;
+    private final ScheduleConfiguration config;
+    private final DataManager dataManager;
+    private final ConstraintValidationService validationService;
+
+    // UI Components
+    private ComboBox<Integer> dayComboBox;
+    private ComboBox<Integer> slotComboBox;
+    private ComboBox<Classroom> classroomComboBox;
+    private VBox validationPanel;
+    private Label validationStatusLabel;
+    private TextArea violationDetails;
+    private Button applyButton;
+    private Button applyAnywayButton;
+
+    // Current state
+    private ValidationResult currentValidation;
+
+    public ExamEditDialog(ExamAssignment assignment, ScheduleState scheduleState, ScheduleConfiguration config) {
+        this.courseCode = assignment.getCourseCode();
+        this.scheduleState = scheduleState;
+        this.config = config;
+        this.dataManager = DataManager.getInstance();
+        this.validationService = new ConstraintValidationService();
+
+        setTitle("Exam Details");
+        setHeaderText(courseCode);
+
+        buildUI(assignment);
+        setupValidation();
+        setupButtons();
+
+        // Initial validation
+        validateCurrentSelection();
+    }
+
+    private void buildUI(ExamAssignment assignment) {
+        GridPane grid = new GridPane();
+        grid.setHgap(15);
+        grid.setVgap(15);
+        grid.setPadding(new Insets(20));
+
+        // Course info header
+        Course course = dataManager.getCourse(courseCode);
+        Classroom currentRoom = dataManager.getClassroom(assignment.getClassroomId());
+        int studentCount = course != null ? course.getEnrolledStudentsCount() : 0;
+
+        Label courseLabel = new Label("Course: " + courseCode);
+        courseLabel.setFont(Font.font("System", FontWeight.BOLD, 14));
+
+        Label studentLabel = new Label("Students enrolled: " + studentCount);
+        studentLabel.setStyle("-fx-text-fill: #666;");
+
+        // Current assignment info
+        String currentInfo = String.format("Current: Day %d, Slot %d, Room %s",
+                assignment.getDay() + 1, assignment.getTimeSlotIndex() + 1, assignment.getClassroomId());
+        Label currentLabel = new Label(currentInfo);
+        currentLabel.setStyle("-fx-text-fill: #666;");
+
+        // Capacity info
+        String capacityInfo = "";
+        if (currentRoom != null) {
+            double utilization = (double) studentCount / currentRoom.getCapacity() * 100;
+            capacityInfo = String.format("Capacity: %d/%d (%.0f%% utilization)",
+                    studentCount, currentRoom.getCapacity(), utilization);
+        }
+        Label capacityLabel = new Label(capacityInfo);
+        capacityLabel.setStyle("-fx-text-fill: #666;");
+
+        VBox headerBox = new VBox(5, courseLabel, studentLabel, currentLabel, capacityLabel);
+        headerBox.setStyle("-fx-padding: 5; -fx-background-color: #f8f9fa; -fx-background-radius: 5;");
+        grid.add(headerBox, 0, 0, 2, 1);
+
+        // Separator
+        Separator sep = new Separator();
+        grid.add(sep, 0, 1, 2, 1);
+
+        // Day selector
+        grid.add(new Label("Day:"), 0, 2);
+        dayComboBox = new ComboBox<>();
+        for (int i = 0; i < config.getNumDays(); i++) {
+            dayComboBox.getItems().add(i);
+        }
+        dayComboBox.setConverter(new StringConverter<>() {
+            @Override
+            public String toString(Integer day) {
+                if (day == null)
+                    return "";
+                TimeSlot slot = config.getTimeSlot(day, 0);
+                String dateStr = slot != null ? " (" + slot.getDate().toString() + ")" : "";
+                return "Day " + (day + 1) + dateStr;
+            }
+
+            @Override
+            public Integer fromString(String string) {
+                return null;
+            }
+        });
+        dayComboBox.setValue(assignment.getDay());
+        dayComboBox.setMaxWidth(Double.MAX_VALUE);
+        grid.add(dayComboBox, 1, 2);
+
+        // Time slot selector
+        grid.add(new Label("Time Slot:"), 0, 3);
+        slotComboBox = new ComboBox<>();
+        for (int i = 0; i < config.getSlotsPerDay(); i++) {
+            slotComboBox.getItems().add(i);
+        }
+        slotComboBox.setConverter(new StringConverter<>() {
+            @Override
+            public String toString(Integer slot) {
+                if (slot == null)
+                    return "";
+                TimeSlot ts = config.getTimeSlot(0, slot);
+                String timeStr = ts != null ? " (" + ts.getStartTime() + " - " + ts.getEndTime() + ")" : "";
+                return "Slot " + (slot + 1) + timeStr;
+            }
+
+            @Override
+            public Integer fromString(String string) {
+                return null;
+            }
+        });
+        slotComboBox.setValue(assignment.getTimeSlotIndex());
+        slotComboBox.setMaxWidth(Double.MAX_VALUE);
+        grid.add(slotComboBox, 1, 3);
+
+        // Classroom selector
+        grid.add(new Label("Classroom:"), 0, 4);
+        classroomComboBox = new ComboBox<>();
+        classroomComboBox.getItems().addAll(dataManager.getClassrooms());
+        classroomComboBox.setConverter(new StringConverter<>() {
+            @Override
+            public String toString(Classroom classroom) {
+                if (classroom == null)
+                    return "";
+                return classroom.getClassroomId() + " (Capacity: " + classroom.getCapacity() + ")";
+            }
+
+            @Override
+            public Classroom fromString(String string) {
+                return null;
+            }
+        });
+        // Set current classroom
+        Classroom currentClassroom = dataManager.getClassroom(assignment.getClassroomId());
+        classroomComboBox.setValue(currentClassroom);
+        classroomComboBox.setMaxWidth(Double.MAX_VALUE);
+        grid.add(classroomComboBox, 1, 4);
+
+        // Column constraints
+        ColumnConstraints col1 = new ColumnConstraints();
+        col1.setMinWidth(80);
+        ColumnConstraints col2 = new ColumnConstraints();
+        col2.setMinWidth(250);
+        col2.setHgrow(Priority.ALWAYS);
+        grid.getColumnConstraints().addAll(col1, col2);
+
+        // Separator before validation
+        Separator sep2 = new Separator();
+        grid.add(sep2, 0, 5, 2, 1);
+
+        // Validation panel
+        validationPanel = new VBox(10);
+        validationPanel.setPadding(new Insets(10));
+        validationPanel.setStyle("-fx-background-color: #f5f5f5; -fx-background-radius: 5;");
+
+        validationStatusLabel = new Label("Checking constraints...");
+        validationStatusLabel.setFont(Font.font("System", FontWeight.BOLD, 12));
+
+        violationDetails = new TextArea();
+        violationDetails.setEditable(false);
+        violationDetails.setWrapText(true);
+        violationDetails.setPrefRowCount(4);
+        violationDetails.setMaxHeight(120);
+        violationDetails.setStyle("-fx-control-inner-background: #f5f5f5;");
+
+        validationPanel.getChildren().addAll(validationStatusLabel, violationDetails);
+        grid.add(validationPanel, 0, 6, 2, 1);
+
+        getDialogPane().setContent(grid);
+        getDialogPane().setPrefWidth(450);
+    }
+
+    private void setupValidation() {
+        // Add listeners to all inputs
+        dayComboBox.valueProperty().addListener((obs, old, newVal) -> validateCurrentSelection());
+        slotComboBox.valueProperty().addListener((obs, old, newVal) -> validateCurrentSelection());
+        classroomComboBox.valueProperty().addListener((obs, old, newVal) -> validateCurrentSelection());
+    }
+
+    private void validateCurrentSelection() {
+        Integer day = dayComboBox.getValue();
+        Integer slot = slotComboBox.getValue();
+        Classroom classroom = classroomComboBox.getValue();
+
+        if (day == null || slot == null || classroom == null) {
+            validationStatusLabel.setText("⚠️ Please select all fields");
+            validationStatusLabel.setTextFill(Color.ORANGE);
+            violationDetails.setText("");
+            updateButtonStates(false, false);
+            return;
+        }
+
+        // Perform validation
+        currentValidation = validationService.validateAssignment(
+                courseCode, day, slot, classroom.getClassroomId(), scheduleState);
+
+        if (currentValidation.isValid()) {
+            validationStatusLabel.setText("✓ No constraint violations");
+            validationStatusLabel.setTextFill(Color.web("#27ae60"));
+            violationDetails.setText("");
+            validationPanel.setStyle("-fx-background-color: #e8f5e9; -fx-background-radius: 5;");
+            updateButtonStates(true, false);
+        } else if (currentValidation.hasHardViolations()) {
+            validationStatusLabel.setText("❌ Constraint violations found");
+            validationStatusLabel.setTextFill(Color.web("#e74c3c"));
+            violationDetails.setText(currentValidation.getFormattedMessage());
+            validationPanel.setStyle("-fx-background-color: #ffebee; -fx-background-radius: 5;");
+            updateButtonStates(false, true);
+        } else {
+            validationStatusLabel.setText("⚠️ Warnings found");
+            validationStatusLabel.setTextFill(Color.web("#f39c12"));
+            violationDetails.setText(currentValidation.getFormattedMessage());
+            validationPanel.setStyle("-fx-background-color: #fff3e0; -fx-background-radius: 5;");
+            updateButtonStates(true, true);
+        }
+    }
+
+    private void updateButtonStates(boolean applyEnabled, boolean showApplyAnyway) {
+        if (applyButton != null) {
+            applyButton.setDisable(!applyEnabled);
+        }
+        if (applyAnywayButton != null) {
+            applyAnywayButton.setVisible(showApplyAnyway);
+            applyAnywayButton.setManaged(showApplyAnyway);
+        }
+    }
+
+    private void setupButtons() {
+        // Create custom button types
+        ButtonType cancelButtonType = new ButtonType("Cancel", ButtonBar.ButtonData.CANCEL_CLOSE);
+        ButtonType applyButtonType = new ButtonType("Apply", ButtonBar.ButtonData.OK_DONE);
+        getDialogPane().getButtonTypes().addAll(cancelButtonType, applyButtonType);
+
+        applyButton = (Button) getDialogPane().lookupButton(applyButtonType);
+        applyButton.setDefaultButton(true);
+
+        // Add "Apply Anyway" button for when there are violations
+        applyAnywayButton = new Button("Apply Anyway");
+        applyAnywayButton.setStyle("-fx-background-color: #e74c3c; -fx-text-fill: white;");
+        applyAnywayButton.setVisible(false);
+        applyAnywayButton.setManaged(false);
+
+        // Find the button bar and add our custom button
+        ButtonBar buttonBar = (ButtonBar) getDialogPane().lookup(".button-bar");
+        if (buttonBar != null) {
+            ButtonBar.setButtonData(applyAnywayButton, ButtonBar.ButtonData.LEFT);
+            buttonBar.getButtons().add(0, applyAnywayButton);
+        }
+
+        // Handle apply anyway
+        applyAnywayButton.setOnAction(e -> {
+            if (currentValidation != null && currentValidation.hasHardViolations()) {
+                // Show confirmation for hard violations
+                Alert confirm = new Alert(Alert.AlertType.WARNING);
+                confirm.setTitle("Confirm Override");
+                confirm.setHeaderText("Override Constraint Violations?");
+                confirm.setContentText(
+                        "You are about to apply changes that violate hard constraints:\n\n" +
+                                currentValidation.getFormattedMessage() + "\n\n" +
+                                "This may cause scheduling conflicts for students. Are you sure?");
+                confirm.getButtonTypes().setAll(ButtonType.YES, ButtonType.NO);
+
+                Optional<ButtonType> result = confirm.showAndWait();
+                if (result.isPresent() && result.get() == ButtonType.YES) {
+                    setResultAndClose(true);
+                }
+            } else {
+                setResultAndClose(true);
+            }
+        });
+
+        // Set result converter
+        setResultConverter(dialogButton -> {
+            if (dialogButton == applyButtonType) {
+                return createResult(false);
+            }
+            return null;
+        });
+    }
+
+    private void setResultAndClose(boolean forced) {
+        EditResult result = createResult(forced);
+        setResult(result);
+        close();
+    }
+
+    private EditResult createResult(boolean forced) {
+        Integer day = dayComboBox.getValue();
+        Integer slot = slotComboBox.getValue();
+        Classroom classroom = classroomComboBox.getValue();
+
+        if (day == null || slot == null || classroom == null) {
+            return null;
+        }
+
+        return new EditResult(courseCode, day, slot, classroom.getClassroomId(), forced);
+    }
+
+    /**
+     * Result of the edit dialog.
+     */
+    public static class EditResult {
+        private final String courseCode;
+        private final int day;
+        private final int timeSlot;
+        private final String classroomId;
+        private final boolean forcedOverride;
+
+        public EditResult(String courseCode, int day, int timeSlot, String classroomId, boolean forcedOverride) {
+            this.courseCode = courseCode;
+            this.day = day;
+            this.timeSlot = timeSlot;
+            this.classroomId = classroomId;
+            this.forcedOverride = forcedOverride;
+        }
+
+        public String getCourseCode() {
+            return courseCode;
+        }
+
+        public int getDay() {
+            return day;
+        }
+
+        public int getTimeSlot() {
+            return timeSlot;
+        }
+
+        public String getClassroomId() {
+            return classroomId;
+        }
+
+        public boolean isForcedOverride() {
+            return forcedOverride;
+        }
+    }
+}

src/main/java/org/example/se302/controller/ScheduleCalendarController.java

@@ -80,6 +80,7 @@ public class ScheduleCalendarController {
     private final DataManager dataManager = DataManager.getInstance();
     private ScheduleGeneratorService generatorService;
     private ScheduleState currentSchedule;
+    private ScheduleConfiguration currentConfig;
     private Thread generationThread;
 
     @FXML
@@ -300,6 +301,7 @@ public class ScheduleCalendarController {
 
         if (result.isSuccess()) {
             currentSchedule = result.getScheduleState();
+            currentConfig = config;
 
             // Save schedule to DataManager (so other views can see it)
             saveScheduleToDataManager(currentSchedule, config);
@@ -474,9 +476,6 @@ public class ScheduleCalendarController {
                 examBox.setStyle("-fx-background-color: #3498db; -fx-background-radius: 3; -fx-padding: 3 6;");
                 examBox.setCursor(Cursor.HAND);
 
-                // Add click handler
-                examBox.setOnMouseClicked(e -> showAssignmentDetails(exam));
-
                 Label courseLabel = new Label(exam.getCourseCode());
                 courseLabel.setStyle("-fx-text-fill: white; -fx-font-weight: bold; -fx-font-size: 11;");
 
@@ -485,8 +484,18 @@ public class ScheduleCalendarController {
 
                 examBox.getChildren().addAll(courseLabel, roomLabel);
 
-                // Add tooltip
-                Tooltip tooltip = new Tooltip(exam.getCourseCode() + "\n" + exam.getClassroomId());
+                // Hover highlight
+                examBox.setOnMouseEntered(e -> examBox
+                        .setStyle("-fx-background-color: #2980b9; -fx-background-radius: 3; -fx-padding: 3 6;"));
+                examBox.setOnMouseExited(e -> examBox
+                        .setStyle("-fx-background-color: #3498db; -fx-background-radius: 3; -fx-padding: 3 6;"));
+
+                // Click opens the edit dialog (which also shows details)
+                examBox.setOnMouseClicked(e -> openEditDialog(exam));
+
+                // Tooltip with hint
+                Tooltip tooltip = new Tooltip(
+                        exam.getCourseCode() + "\n" + exam.getClassroomId() + "\nClick to view/edit");
                 Tooltip.install(examBox, tooltip);
 
                 cell.getChildren().add(examBox);
@@ -503,35 +512,6 @@ public class ScheduleCalendarController {
         return cell;
     }
 
-    private void showAssignmentDetails(ExamAssignment exam) {
-        Course course = dataManager.getCourse(exam.getCourseCode());
-        Classroom room = dataManager.getClassroom(exam.getClassroomId());
-
-        Alert alert = new Alert(Alert.AlertType.INFORMATION);
-        alert.setTitle("Exam Details");
-        alert.setHeaderText(exam.getCourseCode());
-
-        StringBuilder content = new StringBuilder();
-        content.append("Course: ").append(exam.getCourseCode()).append("\n");
-        if (course != null) {
-            content.append("Students: ").append(course.getEnrolledStudentsCount()).append("\n");
-        }
-        content.append("\n");
-        content.append("Assigned Classroom: ").append(exam.getClassroomId()).append("\n");
-        if (room != null) {
-            content.append("Capacity: ").append(room.getCapacity()).append("\n");
-            double fillRatio = course != null ? (double) course.getEnrolledStudentsCount() / room.getCapacity() * 100
-                    : 0;
-            content.append(String.format("Utilization: %.1f%%\n", fillRatio));
-        }
-        content.append("\n");
-        content.append("Day: ").append(exam.getDay() + 1).append("\n");
-        content.append("Slot: ").append(exam.getTimeSlotIndex() + 1).append("\n");
-
-        alert.setContentText(content.toString());
-        alert.showAndWait();
-    }
-
     @FXML
     private void onCancelGeneration() {
         if (generatorService != null) {
@@ -549,4 +529,60 @@ public class ScheduleCalendarController {
         alert.setContentText(message);
         alert.showAndWait();
     }
+
+    /**
+     * Opens the edit dialog for an exam assignment.
+     */
+    private void openEditDialog(ExamAssignment exam) {
+        if (currentSchedule == null || currentConfig == null) {
+            showAlert(Alert.AlertType.WARNING, "Cannot Edit",
+                    "No schedule is currently loaded. Please generate a schedule first.");
+            return;
+        }
+
+        ExamEditDialog dialog = new ExamEditDialog(exam, currentSchedule, currentConfig);
+        dialog.showAndWait().ifPresent(result -> {
+            applyExamEdit(result);
+        });
+    }
+
+    /**
+     * Applies an edit result to the schedule.
+     */
+    private void applyExamEdit(ExamEditDialog.EditResult result) {
+        if (result == null)
+            return;
+
+        String courseCode = result.getCourseCode();
+        int newDay = result.getDay();
+        int newSlot = result.getTimeSlot();
+        String newClassroom = result.getClassroomId();
+
+        // Update the ScheduleState
+        boolean updated = currentSchedule.updateAssignment(courseCode, newDay, newSlot, newClassroom);
+
+        if (updated) {
+            // Also update the Course in DataManager
+            Course course = dataManager.getCourse(courseCode);
+            if (course != null) {
+                course.setExamSchedule(newDay, newSlot, newClassroom);
+            }
+
+            // Refresh the grid display
+            displayScheduleGrid(currentSchedule, currentConfig);
+
+            // Update status
+            String message = result.isForcedOverride() ? "⚠️ Exam moved (with override)" : "✓ Exam moved successfully";
+            statusLabel.setText(message);
+            statusLabel.setStyle(result.isForcedOverride() ? "-fx-text-fill: #f39c12;" : "-fx-text-fill: #27ae60;");
+
+            // Log the change
+            System.out.println("Exam edited: " + courseCode + " -> Day " + (newDay + 1) +
+                    ", Slot " + (newSlot + 1) + ", Room " + newClassroom +
+                    (result.isForcedOverride() ? " (forced)" : ""));
+        } else {
+            showAlert(Alert.AlertType.ERROR, "Edit Failed",
+                    "Could not update the exam assignment. The exam may be locked.");
+        }
+    }
 }

src/main/java/org/example/se302/service/ConstraintValidationService.java

@@ -0,0 +1,274 @@
+package org.example.se302.service;
+
+import org.example.se302.model.*;
+
+import java.util.*;
+
+/**
+ * Service for validating exam assignment changes against constraints.
+ * Provides detailed violation information including affected student names.
+ */
+public class ConstraintValidationService {
+
+    private final DataManager dataManager;
+
+    public ConstraintValidationService() {
+        this.dataManager = DataManager.getInstance();
+    }
+
+    /**
+     * Validates a proposed exam assignment change.
+     *
+     * @param courseCode   The course being moved
+     * @param newDay       Proposed day (0-based)
+     * @param newSlot      Proposed time slot (0-based)
+     * @param newClassroom Proposed classroom ID
+     * @param currentState Current schedule state (to check against other exams)
+     * @return ValidationResult with all violations found
+     */
+    public ValidationResult validateAssignment(String courseCode, int newDay, int newSlot,
+            String newClassroom, ScheduleState currentState) {
+        ValidationResult result = new ValidationResult();
+
+        // Get course info
+        Course course = dataManager.getCourse(courseCode);
+        if (course == null) {
+            result.addViolation(new ConstraintViolation(
+                    "Unknown Course",
+                    true,
+                    "Course " + courseCode + " not found",
+                    Collections.emptyList(),
+                    null));
+            return result;
+        }
+
+        // Check classroom capacity
+        Classroom classroom = dataManager.getClassroom(newClassroom);
+        if (classroom == null) {
+            result.addViolation(new ConstraintViolation(
+                    "Unknown Classroom",
+                    true,
+                    "Classroom " + newClassroom + " not found",
+                    Collections.emptyList(),
+                    null));
+        } else if (classroom.getCapacity() < course.getEnrolledStudentsCount()) {
+            result.addViolation(new ConstraintViolation(
+                    "Capacity Exceeded",
+                    true,
+                    String.format("Classroom %s has capacity %d, but course has %d students",
+                            newClassroom, classroom.getCapacity(), course.getEnrolledStudentsCount()),
+                    Collections.emptyList(),
+                    null));
+        }
+
+        // Check classroom conflict (another exam in same classroom at same time)
+        String classroomConflictCourse = getClassroomConflict(courseCode, newClassroom, newDay, newSlot, currentState);
+        if (classroomConflictCourse != null) {
+            result.addViolation(new ConstraintViolation(
+                    "Classroom Conflict",
+                    true,
+                    String.format("Classroom %s is already used by %s at this time",
+                            newClassroom, classroomConflictCourse),
+                    Collections.emptyList(),
+                    classroomConflictCourse));
+        }
+
+        // Check student conflicts (students with exams at the same time)
+        List<StudentConflictInfo> studentConflicts = getStudentConflicts(courseCode, newDay, newSlot, currentState);
+        if (!studentConflicts.isEmpty()) {
+            // Group by conflicting course
+            Map<String, List<String>> conflictsByCourse = new LinkedHashMap<>();
+            for (StudentConflictInfo conflict : studentConflicts) {
+                conflictsByCourse
+                        .computeIfAbsent(conflict.conflictingCourse, k -> new ArrayList<>())
+                        .add(conflict.studentId);
+            }
+
+            for (Map.Entry<String, List<String>> entry : conflictsByCourse.entrySet()) {
+                String conflictCourse = entry.getKey();
+                List<String> students = entry.getValue();
+
+                String studentList = formatStudentList(students);
+
+                result.addViolation(new ConstraintViolation(
+                        "Student Conflict",
+                        true,
+                        String.format("%d student(s) have exams for both %s and %s at this time: %s",
+                                students.size(), courseCode, conflictCourse, studentList),
+                        new ArrayList<>(students),
+                        conflictCourse));
+            }
+        }
+
+        return result;
+    }
+
+    /**
+     * Gets the course that conflicts with the given classroom at the specified
+     * time.
+     */
+    private String getClassroomConflict(String excludeCourse, String classroomId,
+            int day, int slot, ScheduleState state) {
+        for (ExamAssignment assignment : state.getAssignments().values()) {
+            if (assignment.getCourseCode().equals(excludeCourse)) {
+                continue; // Skip the course being moved
+            }
+            if (assignment.isAssigned() &&
+                    assignment.getDay() == day &&
+                    assignment.getTimeSlotIndex() == slot &&
+                    classroomId.equals(assignment.getClassroomId())) {
+                return assignment.getCourseCode();
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Gets all student conflicts for a proposed assignment.
+     */
+    private List<StudentConflictInfo> getStudentConflicts(String courseCode, int day, int slot,
+            ScheduleState state) {
+        List<StudentConflictInfo> conflicts = new ArrayList<>();
+
+        Course course = dataManager.getCourse(courseCode);
+        if (course == null) {
+            return conflicts;
+        }
+
+        Set<String> enrolledStudents = new HashSet<>(course.getEnrolledStudents());
+
+        // Find all other courses at the same time
+        for (ExamAssignment assignment : state.getAssignments().values()) {
+            if (assignment.getCourseCode().equals(courseCode)) {
+                continue; // Skip self
+            }
+            if (!assignment.isAssigned() ||
+                    assignment.getDay() != day ||
+                    assignment.getTimeSlotIndex() != slot) {
+                continue; // Not at the same time
+            }
+
+            Course otherCourse = dataManager.getCourse(assignment.getCourseCode());
+            if (otherCourse == null) {
+                continue;
+            }
+
+            // Check for shared students
+            for (String studentId : otherCourse.getEnrolledStudents()) {
+                if (enrolledStudents.contains(studentId)) {
+                    conflicts.add(new StudentConflictInfo(studentId, assignment.getCourseCode()));
+                }
+            }
+        }
+
+        return conflicts;
+    }
+
+    /**
+     * Formats a list of student IDs for display.
+     */
+    private String formatStudentList(List<String> students) {
+        if (students.size() <= 5) {
+            return String.join(", ", students);
+        } else {
+            List<String> first5 = students.subList(0, 5);
+            return String.join(", ", first5) + " and " + (students.size() - 5) + " more";
+        }
+    }
+
+    // ============= Inner Classes =============
+
+    /**
+     * Holds information about a student conflict.
+     */
+    private static class StudentConflictInfo {
+        final String studentId;
+        final String conflictingCourse;
+
+        StudentConflictInfo(String studentId, String conflictingCourse) {
+            this.studentId = studentId;
+            this.conflictingCourse = conflictingCourse;
+        }
+    }
+
+    /**
+     * Represents the result of a constraint validation.
+     */
+    public static class ValidationResult {
+        private final List<ConstraintViolation> violations = new ArrayList<>();
+
+        public void addViolation(ConstraintViolation violation) {
+            violations.add(violation);
+        }
+
+        public List<ConstraintViolation> getViolations() {
+            return Collections.unmodifiableList(violations);
+        }
+
+        public boolean isValid() {
+            return violations.isEmpty();
+        }
+
+        public boolean hasHardViolations() {
+            return violations.stream().anyMatch(ConstraintViolation::isHard);
+        }
+
+        public boolean hasSoftViolations() {
+            return violations.stream().anyMatch(v -> !v.isHard());
+        }
+
+        public String getFormattedMessage() {
+            if (violations.isEmpty()) {
+                return "✓ No constraint violations";
+            }
+
+            StringBuilder sb = new StringBuilder();
+            for (ConstraintViolation v : violations) {
+                sb.append(v.isHard() ? "❌ " : "⚠️ ");
+                sb.append(v.getConstraintName()).append(": ");
+                sb.append(v.getMessage()).append("\n");
+            }
+            return sb.toString().trim();
+        }
+    }
+
+    /**
+     * Represents a single constraint violation.
+     */
+    public static class ConstraintViolation {
+        private final String constraintName;
+        private final boolean isHard;
+        private final String message;
+        private final List<String> affectedStudents;
+        private final String conflictingCourse;
+
+        public ConstraintViolation(String constraintName, boolean isHard, String message,
+                List<String> affectedStudents, String conflictingCourse) {
+            this.constraintName = constraintName;
+            this.isHard = isHard;
+            this.message = message;
+            this.affectedStudents = affectedStudents != null ? affectedStudents : Collections.emptyList();
+            this.conflictingCourse = conflictingCourse;
+        }
+
+        public String getConstraintName() {
+            return constraintName;
+        }
+
+        public boolean isHard() {
+            return isHard;
+        }
+
+        public String getMessage() {
+            return message;
+        }
+
+        public List<String> getAffectedStudents() {
+            return affectedStudents;
+        }
+
+        public String getConflictingCourse() {
+            return conflictingCourse;
+        }
+    }
+}