Remove redundant code

src/main/java/tuteez/model/person/lesson/Day.java

@@ -1,33 +1,62 @@
 package tuteez.model.person.lesson;
 
+import java.util.HashMap;
+import java.util.Map;
+
 /**
  * Enum to represent the days of the week.
  */
 public enum Day {
-    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
+    MONDAY("mon"),
+    TUESDAY("tue"),
+    WEDNESDAY("wed"),
+    THURSDAY("thu"),
+    FRIDAY("fri"),
+    SATURDAY("sat"),
+    SUNDAY("sun");
+
+    private final String shortName;
+    private static final Map<String, Day> DAY_NAME_MAP = new HashMap<>();
+
+    static {
+        for (Day day : values()) {
+            DAY_NAME_MAP.put(day.name().toLowerCase(), day);
+            DAY_NAME_MAP.put(day.shortName, day);
+        }
+    }
+
+    /**
+     * Constructs a Day enum value with its corresponding short name.
+     *
+     * @param shortName The abbreviated name of the day (e.g., "mon" for Monday)
+     */
+    private Day(String shortName) {
+        this.shortName = shortName;
+    }
 
     /**
      * Converts a string representation of a day into the corresponding {@code Day} enum value.
      *
-     * <p>The string must be in lowercase (e.g., "monday", "tuesday"). If the string does not
+     * <p>The string must be in lowercase (e.g., "monday", "mon"). If the string does not
      * match any of the valid days of the week, an exception is thrown.</p>
      *
      * @param dayInStr The string representing the day of the week (e.g., "monday", "mon").
      * @return The {@code Day} enum corresponding to the input string.
      * @throws IllegalArgumentException If the provided string does not match a valid day.
      */
     public static Day convertDayToEnum(String dayInStr) {
-        return switch (dayInStr) {
-        case "monday", "mon" -> MONDAY;
-        case "tuesday", "tue" -> TUESDAY;
-        case "wednesday", "wed" -> WEDNESDAY;
-        case "thursday", "thu" -> THURSDAY;
-        case "friday", "fri" -> FRIDAY;
-        case "saturday", "sat" -> SATURDAY;
-        case "sunday", "sun" -> SUNDAY;
-        // Default case should not occur because input is validated before calling the method.
-        default -> throw new IllegalArgumentException("Invalid day string: " + dayInStr);
-        };
+        assert dayInStr!= null;
+        return DAY_NAME_MAP.get(dayInStr.toLowerCase());
+    }
+
+    /**
+     * Checks if the day provided is valid (i.e., part of the defined Days enum).
+     *
+     * @param day The day to check.
+     * @return true if the day is valid.
+     */
+    public static boolean isValidDay(String day) {
+        return day != null && DAY_NAME_MAP.containsKey(day.toLowerCase());
     }
 
     @Override

src/main/java/tuteez/model/person/lesson/Lesson.java

@@ -6,8 +6,6 @@
 import java.time.LocalTime;
 import java.time.format.DateTimeFormatter;
 import java.util.Comparator;
-import java.util.HashMap;
-import java.util.Map;
 import java.util.Objects;
 
 
@@ -27,27 +25,6 @@ public class Lesson {
     private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("HHmm");
     private static final String VALID_TIME_RANGE_REGEX = "([01]?[0-9]|2[0-3])[0-5][0-9]-([01]?[0-9]|2[0-3])[0-5][0-9]";
     private static final DateTimeFormatter timeFormatter = DateTimeFormatter.ofPattern("HHmm");
-    /**
-     * Maps various string representations of days (e.g., "monday", "mon") to their corresponding Day enum values.
-     * All keys are stored in lowercase.
-     */
-    private static final Map<String, Day> DAY_NAME_MAP = new HashMap<>();
-    static {
-        DAY_NAME_MAP.put("monday", Day.MONDAY);
-        DAY_NAME_MAP.put("mon", Day.MONDAY);
-        DAY_NAME_MAP.put("tuesday", Day.TUESDAY);
-        DAY_NAME_MAP.put("tue", Day.TUESDAY);
-        DAY_NAME_MAP.put("wednesday", Day.WEDNESDAY);
-        DAY_NAME_MAP.put("wed", Day.WEDNESDAY);
-        DAY_NAME_MAP.put("thursday", Day.THURSDAY);
-        DAY_NAME_MAP.put("thu", Day.THURSDAY);
-        DAY_NAME_MAP.put("friday", Day.FRIDAY);
-        DAY_NAME_MAP.put("fri", Day.FRIDAY);
-        DAY_NAME_MAP.put("saturday", Day.SATURDAY);
-        DAY_NAME_MAP.put("sat", Day.SATURDAY);
-        DAY_NAME_MAP.put("sunday", Day.SUNDAY);
-        DAY_NAME_MAP.put("sun", Day.SUNDAY);
-    }
     private final Day lessonDay;
     private final LocalTime startTime;
     private final LocalTime endTime;
@@ -67,16 +44,6 @@ public Lesson(String lesson) {
         this.endTime = LocalTime.parse(timeArr[1], timeFormatter);
     }
 
-    /**
-     * Validates if the day provided is valid (i.e., part of the defined Days enum).
-     *
-     * @param day The day to check.
-     * @return true if the day is valid.
-     */
-    private static boolean isValidDay(String day) {
-        return DAY_NAME_MAP.containsKey(day.toLowerCase());
-    }
-
     /**
      * Validates the time range format (should be HHMM-HHMM 24-hour format).
      *
@@ -122,7 +89,7 @@ public static boolean isValidLesson(String lesson) {
         }
         String day = parts[0];
         String timeRange = parts[1];
-        return isValidDay(day) && isValidTimeRange(timeRange) && isValidTimeOrder(timeRange);
+        return Day.isValidDay(day) && isValidTimeRange(timeRange) && isValidTimeOrder(timeRange);
     }
 
     /**

src/test/java/tuteez/model/person/lesson/DayTest.java

@@ -0,0 +1,84 @@
+package tuteez.model.person.lesson;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+public class DayTest {
+
+    @Test
+    public void isValidDay_validInputs_returnsTrue() {
+        assertTrue(Day.isValidDay("monday"));
+        assertTrue(Day.isValidDay("tuesday"));
+        assertTrue(Day.isValidDay("wednesday"));
+        assertTrue(Day.isValidDay("thursday"));
+        assertTrue(Day.isValidDay("friday"));
+        assertTrue(Day.isValidDay("saturday"));
+        assertTrue(Day.isValidDay("sunday"));
+
+        assertTrue(Day.isValidDay("mon"));
+        assertTrue(Day.isValidDay("tue"));
+        assertTrue(Day.isValidDay("wed"));
+        assertTrue(Day.isValidDay("thu"));
+        assertTrue(Day.isValidDay("fri"));
+        assertTrue(Day.isValidDay("sat"));
+        assertTrue(Day.isValidDay("sun"));
+
+        assertTrue(Day.isValidDay("Monday"));
+        assertTrue(Day.isValidDay("TUESDAY"));
+        assertTrue(Day.isValidDay("wEdNeSdAy"));
+        assertTrue(Day.isValidDay("Thu"));
+        assertTrue(Day.isValidDay("FRI"));
+    }
+
+    @Test
+    public void isValidDay_invalidInputs_returnsFalse() {
+        assertFalse(Day.isValidDay("not a day"));
+        assertFalse(Day.isValidDay("mon day"));
+        assertFalse(Day.isValidDay("mondays"));
+        assertFalse(Day.isValidDay("tues"));
+        assertFalse(Day.isValidDay("thur"));
+
+        assertFalse(Day.isValidDay(""));
+        assertFalse(Day.isValidDay(" "));
+        assertFalse(Day.isValidDay("\t"));
+
+        assertFalse(Day.isValidDay(null));
+    }
+
+    @Test
+    public void convertDayToEnum_validInputs_returnsCorrectEnum() {
+        assertEquals(Day.MONDAY, Day.convertDayToEnum("monday"));
+        assertEquals(Day.TUESDAY, Day.convertDayToEnum("tuesday"));
+        assertEquals(Day.WEDNESDAY, Day.convertDayToEnum("wednesday"));
+        assertEquals(Day.THURSDAY, Day.convertDayToEnum("thursday"));
+        assertEquals(Day.FRIDAY, Day.convertDayToEnum("friday"));
+        assertEquals(Day.SATURDAY, Day.convertDayToEnum("saturday"));
+        assertEquals(Day.SUNDAY, Day.convertDayToEnum("sunday"));
+
+        assertEquals(Day.MONDAY, Day.convertDayToEnum("mon"));
+        assertEquals(Day.TUESDAY, Day.convertDayToEnum("tue"));
+        assertEquals(Day.WEDNESDAY, Day.convertDayToEnum("wed"));
+        assertEquals(Day.THURSDAY, Day.convertDayToEnum("thu"));
+        assertEquals(Day.FRIDAY, Day.convertDayToEnum("fri"));
+        assertEquals(Day.SATURDAY, Day.convertDayToEnum("sat"));
+        assertEquals(Day.SUNDAY, Day.convertDayToEnum("sun"));
+
+        assertEquals(Day.MONDAY, Day.convertDayToEnum("Monday"));
+        assertEquals(Day.TUESDAY, Day.convertDayToEnum("TUESDAY"));
+        assertEquals(Day.WEDNESDAY, Day.convertDayToEnum("wEdNeSdAy"));
+    }
+
+    @Test
+    public void toString_returnsUpperCase() {
+        assertEquals("MONDAY", Day.MONDAY.toString());
+        assertEquals("TUESDAY", Day.TUESDAY.toString());
+        assertEquals("WEDNESDAY", Day.WEDNESDAY.toString());
+        assertEquals("THURSDAY", Day.THURSDAY.toString());
+        assertEquals("FRIDAY", Day.FRIDAY.toString());
+        assertEquals("SATURDAY", Day.SATURDAY.toString());
+        assertEquals("SUNDAY", Day.SUNDAY.toString());
+    }
+}

src/test/java/tuteez/model/person/lesson/LessonTest.java

@@ -98,11 +98,15 @@ public void equals() {
         Lesson l1 = new Lesson("Friday 1300-1400");
         Lesson l2 = new Lesson("Friday 1300-1400");
         Lesson l3 = new Lesson("friday 1300-1400");
+        Lesson l4 = new Lesson("Saturday 1300-1400");
+        Lesson l5 = new Lesson("Friday 1300-1430");
 
         Assertions.assertNotEquals(l1, new Object());
         assertEquals(l1, l1);
         assertEquals(l1, l2);
         assertEquals(l2, l3);
+        assertFalse(l1.equals(l4));
+        assertFalse(l1.equals(l5));
     }
 
     @Test