HOMEWORK 2 — State, Navigation & Room
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Mobile Application Development | SUZA | Semester II 2025/2026
Weight: 15% | Individual work | Due: end of Week 9

TASK — Build a "PocketBudget" app
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An app that lets a student track day-to-day expenses with monthly totals.

FEATURES (all required)
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1. Three screens linked by Navigation-Compose:
   a. DashboardScreen — total for the current month + list of recent expenses
   b. AddExpenseScreen — form to add a new expense
   c. HistoryScreen — all expenses grouped by month (LazyColumn + sticky headers)

2. Expense entity in Room:
     id (auto), amount (Double), category (String),
     note (String?), timestamp (Long = epoch ms)

3. Categories: enum { Food, Transport, Books, Bills, Other }
   Add an exhaustive "when" branch — adding a new category must force
   the compiler to remind you of every call-site.

4. MVVM architecture:
   - ExpenseDao, ExpenseRepository, ExpenseViewModel
   - ViewModel exposes StateFlow<List<Expense>> and
     StateFlow<Map<String, Double>> for monthly totals

5. UI features:
   - Add button opens AddExpenseScreen (returning to dashboard on save)
   - Tap expense → delete confirmation dialog
   - Empty state illustration when there are no records
   - Currency formatted to 2 decimals (e.g. "Tsh 12,500.00")
   - Keyboard types: Number for amount

6. Validation:
   - Amount must be > 0
   - Category required
   - Save button disabled until valid

STRETCH (optional, +10 pts bonus)
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- Add a simple bar chart (Canvas Composable) showing expense by category
- Export the current-month list to a CSV file via the system share sheet

GRADING RUBRIC (100 pts)
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  Architecture & layering (ViewModel/Repo/DAO)         20
  Room setup and correctness (entity, DAO, migrations) 20
  Navigation flow between screens                      10
  Compose UI quality and state hoisting                15
  Empty / loading / error states handled               10
  Validation & UX polish                               10
  Tests (≥ 1 unit test + ≥ 1 UI test)                  10
  Code cleanliness and documentation                    5

SUBMISSION
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- GitHub repo "mad-hw2-<studentid>"
- README.md with screenshots, architecture diagram, build instructions
- Short demo video (≤ 90 sec)
- Submit repo URL on Moodle