Fix bugs

docs/UserGuide.md

@@ -188,7 +188,7 @@ Examples:
 
 ### Adding a Tutee: `addTutee`
 
-Adds a Tutee to VolunTier.
+Adds a tutee to VolunTier.
 
 Format: `addTutee \n NAME \p PHONE_NUMBER \e EMAIL \a ADDRESS [\h HOURS] [\s SUBJECT]…​`
 
@@ -216,7 +216,7 @@ Format: `addTutee \n NAME \p PHONE_NUMBER \e EMAIL \a ADDRESS [\h HOURS] [\s SUB
 
 ### Adding a Lesson: `addLesson`
 
-Add a lesson in VolunTier between a tutor and tutee. A lesson must have a tutor, a tutee and a subject.
+Adds a lesson in VolunTier between a tutor and tutee. A lesson must have a tutor, a tutee and a subject.
 
 Format: `addLesson TUTOR_INDEX TUTEE_INDEX \s SUBJECT`
 

src/main/java/seedu/address/logic/commands/ViewCommand.java

@@ -18,7 +18,7 @@
 public class ViewCommand extends Command {
     public static final String COMMAND_WORD = "view";
 
-    public static final String MESSAGE_SUCCESS = "Here is the details of the person you wanted to see: \n %1$s";
+    public static final String MESSAGE_SUCCESS = "Here are the details of the person you wanted to see: \n %1$s";
 
     public static final String MESSAGE_USAGE = COMMAND_WORD + ": Views the person identified by the index number "
             + "used in the displayed person list.\n"

src/main/java/seedu/address/model/person/Name.java

@@ -10,7 +10,7 @@
 public class Name {
 
     public static final String MESSAGE_CONSTRAINTS =
-            "Names should only contain alphanumeric characters and spaces, and it should not be blank";
+            "Names should only contain alphanumeric characters and spaces, and it should not be blank.";
 
     /*
      * The first character of the address must not be a whitespace,

src/main/java/seedu/address/model/person/Phone.java

@@ -11,7 +11,7 @@ public class Phone {
 
 
     public static final String MESSAGE_CONSTRAINTS =
-            "Phone numbers should only contain numbers, and it should be 8 digits long and start with 6, 8 or 9";
+            "Phone numbers should only contain numbers, and it should be 8 digits long and start with 6, 8 or 9.";
     public static final String VALIDATION_REGEX = "^[689]\\d{7}$";
     public final String value;
 

src/main/java/seedu/address/storage/JsonSerializableAddressBook.java

@@ -10,11 +10,13 @@
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonRootName;
 
+import javafx.collections.ObservableList;
 import seedu.address.commons.exceptions.IllegalValueException;
 import seedu.address.model.AddressBook;
 import seedu.address.model.ReadOnlyAddressBook;
 import seedu.address.model.lesson.Lesson;
 import seedu.address.model.person.Person;
+import seedu.address.model.person.Subject;
 import seedu.address.model.person.Tutee;
 import seedu.address.model.person.Tutor;
 
@@ -29,6 +31,9 @@ class JsonSerializableAddressBook {
 
     public static final String MESSAGE_DUPLICATE_LESSON = "Lessons list contains duplicate lesson(s).";
 
+    public static final String MESSAGE_PERSON_LESSON_MISMATCH = "Lessons list contains some lessons with "
+            + "invalid subjects.";
+
     private final List<JsonAdaptedPerson> persons = new ArrayList<>();
 
     private final List<JsonAdaptedLesson> lessons = new ArrayList<>();
@@ -72,6 +77,23 @@ public JsonSerializableAddressBook(ReadOnlyAddressBook source) {
         );
     }
 
+    public boolean validateLessonSubject(AddressBook addressBook) {
+        ObservableList<Lesson> lessonList = addressBook.getLessonList();
+        for (Lesson lesson : lessonList) {
+            Subject subject = lesson.getSubject();
+            Tutor tutor = lesson.getTutor();
+            Tutee tutee = lesson.getTutee();
+            if (tutor == null || tutee == null) {
+                return false;
+            }
+
+            if (!tutor.getSubjects().contains(subject) || !tutee.getSubjects().contains(subject)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
     /**
      * Converts this address book into the model's {@code AddressBook} object.
      *
@@ -96,6 +118,9 @@ public AddressBook toModelType() throws IllegalValueException {
             }
             addressBook.addLesson(lesson);
         }
+        if (!validateLessonSubject(addressBook)) {
+            throw new IllegalValueException(MESSAGE_PERSON_LESSON_MISMATCH);
+        }
         return addressBook;
     }
 

src/test/data/JsonSerializableAddressBookTest/personLessonMismatchAddressBook.json

@@ -0,0 +1,38 @@
+{
+  "persons": [
+    {
+      "id": 6,
+      "name": "Lily Seow",
+      "phone": "98476978",
+      "email": "[email protected]",
+      "address": "Blk 480 Tampines Street 72, #14-35, 876922",
+      "hours": "0",
+      "subjects": [
+        "English",
+        "Science"
+      ],
+      "role": "Tutee"
+    },
+    {
+      "id": 7,
+      "name": "Sophia Yeo",
+      "phone": "90913712",
+      "email": "[email protected]",
+      "address": "Blk 589 Ang Mo Kio Street, #18-37, 714536",
+      "hours": "0",
+      "subjects": [
+        "English",
+        "Math"
+      ],
+      "role": "Tutor"
+    }
+  ],
+  "lessons": [
+    {
+      "tutorId": 7,
+      "tuteeId": 6,
+      "subject": "Math"
+    }
+  ]
+}
+

src/test/java/seedu/address/storage/JsonSerializableAddressBookTest.java

@@ -20,6 +20,8 @@ public class JsonSerializableAddressBookTest {
     private static final Path INVALID_PERSON_FILE = TEST_DATA_FOLDER.resolve("invalidPersonAddressBook.json");
     private static final Path DUPLICATE_PERSON_FILE = TEST_DATA_FOLDER.resolve("duplicatePersonAddressBook.json");
     private static final Path DUPLICATE_LESSONS_FILE = TEST_DATA_FOLDER.resolve("duplicateLessonAddressBook.json");
+    private static final Path PERSON_LESSON_MISMATCH_FILE = TEST_DATA_FOLDER.resolve("personLessonMismatchAddres"
+            + "sBook.json");
 
     @Test
     public void toModelType_typicalPersonsFile_success() throws Exception {
@@ -53,4 +55,13 @@ public void toModelType_duplicateLessons_throwsIllegalValueException() throws Ex
         assertThrows(IllegalValueException.class, JsonSerializableAddressBook.MESSAGE_DUPLICATE_LESSON,
                 dataFromFile::toModelType);
     }
+
+    @Test
+    public void toModelType_personLessonMismatch_throwsIllegalValueException() throws Exception {
+        JsonSerializableAddressBook dataFromFile = JsonUtil.readJsonFile(PERSON_LESSON_MISMATCH_FILE,
+                JsonSerializableAddressBook.class).get();
+        assertThrows(IllegalValueException.class, JsonSerializableAddressBook.MESSAGE_PERSON_LESSON_MISMATCH,
+                dataFromFile::toModelType);
+    }
 }
+