From b76decc9329baaee0eb874572a1129d049958f28 Mon Sep 17 00:00:00 2001
From: QianChangru <changru_qian@u.nus.edu>
Date: Fri, 15 Sep 2023 15:34:48 +0800
Subject: [PATCH] Implement A-Assertions

The functional code is not capable of checking assumptions.

Assumptions may not be true in some cases and checking is required.

Let's add assert feature to document important assumptions.
---
 build.gradle                     | 2 ++
 src/main/java/duke/Storage.java  | 1 +
 src/main/java/duke/Task.java     | 4 ++++
 src/main/java/duke/TaskList.java | 6 ++++++
 4 files changed, 13 insertions(+)

diff --git a/build.gradle b/build.gradle
index 1ff9cdfbd3..44734913da 100644
--- a/build.gradle
+++ b/build.gradle
@@ -55,6 +55,8 @@ shadowJar {
 
 run{
     standardInput = System.in
+
+    enableAssertions = true
 }
 
 mainClassName = "duke.Launcher"
diff --git a/src/main/java/duke/Storage.java b/src/main/java/duke/Storage.java
index 91f72bb4d0..aa80c724ad 100644
--- a/src/main/java/duke/Storage.java
+++ b/src/main/java/duke/Storage.java
@@ -35,6 +35,7 @@ public ArrayList<Task> load() throws IOException {
         }
         File f = new File(filePath);
         f.createNewFile();
+        assert f.exists();
         Scanner s = new Scanner(f);
         ArrayList<Task> tasks = new ArrayList<>();
         while (s.hasNext()) {
diff --git a/src/main/java/duke/Task.java b/src/main/java/duke/Task.java
index d01083c8b5..708cde93d7 100644
--- a/src/main/java/duke/Task.java
+++ b/src/main/java/duke/Task.java
@@ -13,11 +13,15 @@ public class Task {
      * @param description Description of the task.
      */
     public Task(String description) {
+        assert !description.isEmpty();
+
         this.description = description;
         this.isDone = false;
     }
 
     public Task(String description, boolean isDone) {
+        assert !description.isEmpty();
+
         this.description = description;
         this.isDone = isDone;
     }
diff --git a/src/main/java/duke/TaskList.java b/src/main/java/duke/TaskList.java
index 5657d1bc8d..72757c089d 100644
--- a/src/main/java/duke/TaskList.java
+++ b/src/main/java/duke/TaskList.java
@@ -47,6 +47,8 @@ public String addTask(Task t) {
      * @return The message for deleting.
      */
     public String deleteTask(int num) {
+        assert num >= 0;
+
         Task re = tasks.remove(num);
         this.storage.rewriteFile(tasks);
         return Ui.deleteTask(re, tasks);
@@ -59,6 +61,8 @@ public String deleteTask(int num) {
      * @return The message for marking.
      */
     public String markTask(int num) {
+        assert num >= 0;
+
         Task t = tasks.get(num);
         t.markAsDone();
         this.storage.rewriteFile(tasks);
@@ -72,6 +76,8 @@ public String markTask(int num) {
      * @return The message for searching results.
      */
     public String findTask(String keyword) {
+        assert keyword != null;
+
         ArrayList<Task> result = new ArrayList<>();
         for (int i = 0; i < this.tasks.size(); i++) {
             if (tasks.get(i).toString().contains(keyword)) {