Fix a bug that allowed negative Transaction amounts

Now for every amount, the absolute value is taken. As a result, also
  the classes that relied on amount being negative to compute the
  balance are changed (now the balance is computed by calculating the
  sum of all the deposit transaction amounts minus the sum of all the
  withdrawal transaction amounts).

sql_queries_and_updates.txt

@@ -154,11 +154,19 @@ AND description LIKE ?
 AND external_iban LIKE ?
 AND type LIKE ?;
 
-    getBalanceOnDate(user_id, date):
+    getDepositsOnDate(user_id, date):
 SELECT SUM(amount)
 FROM Transaction_Table
 WHERE user_id = ?
-AND date <= ?;
+AND date <= ?
+AND type = 'deposit';
+
+    getWithdrawalsOnDate(user_id, date):
+SELECT SUM(amount)
+FROM Transaction_Table
+WHERE user_id = ?
+AND date <= ?
+AND type = 'withdrawal';
 
     getTransactionsAfterDate(user_id, date):
 SELECT transaction_id, date, amount, description, external_iban, type

src/main/java/nl/utwente/ing/api/MainRestController.java

@@ -126,6 +126,7 @@ public ResponseEntity postTransaction(@RequestParam(value = "session_id", defaul
         if (!t.getType().equals("deposit") && !t.getType().equals("withdrawal")) {
             return ResponseEntity.status(405).body("Invalid input given (type should be 'deposit' or 'withdrawal')");
         }
+        t.setAmount(Math.abs(t.getAmount()));
         if (t.getDescription() == null) {
             t.setDescription("");
         }
@@ -196,6 +197,7 @@ public ResponseEntity putTransaction(@RequestParam(value = "session_id", default
                 !t.getType().equals("deposit") && !t.getType().equals("withdrawal")) {
             return ResponseEntity.status(405).body("Invalid input given (type should be 'deposit' or 'withdrawal')");
         }
+        t.setAmount(Math.abs(t.getAmount()));
         try {
             String sessionID = this.getSessionID(pSessionID, hSessionID);
             long transactionIDLong = Long.parseLong(transactionID);

src/main/java/nl/utwente/ing/model/persistentmodel/CustomORM.java

@@ -151,11 +151,18 @@ public class CustomORM {
                     "AND description LIKE ?\n" +
                     "AND external_iban LIKE ?\n" +
                     "AND type LIKE ?;";
-    public static final String GET_BALANCE_ON_DATE =
+    public static final String GET_DEPOSITS_ON_DATE =
             "SELECT SUM(amount)\n" +
                     "FROM Transaction_Table\n" +
                     "WHERE user_id = ?\n" +
-                    "AND date <= ?;";
+                    "AND date <= ?\n" +
+                    "AND type = 'deposit';";
+    public static final String GET_WITHDRAWALS_ON_DATE =
+            "SELECT SUM(amount)\n" +
+                    "FROM Transaction_Table\n" +
+                    "WHERE user_id = ?\n" +
+                    "AND date <= ?\n" +
+                    "AND type = 'withdrawal';";
     public static final String GET_TRANSACTIONS_AFTER_DATE =
             "SELECT transaction_id, date, amount, description, external_iban, type\n" +
                     "FROM Transaction_Table\n" +
@@ -800,12 +807,19 @@ public ArrayList<Long> getMatchingTransactionIDs(int userID, CategoryRule catego
     public float getBalanceOnDate(int userID, String date) {
         float balance = 0;
         try {
-            PreparedStatement statement = connection.prepareStatement(GET_BALANCE_ON_DATE);
+            PreparedStatement statement = connection.prepareStatement(GET_DEPOSITS_ON_DATE);
             statement.setInt(1, userID);
             statement.setString(2, date);
             ResultSet resultSet = statement.executeQuery();
             resultSet.next();
-            balance = resultSet.getFloat(1);
+            balance += resultSet.getFloat(1);
+
+            statement = connection.prepareStatement(GET_WITHDRAWALS_ON_DATE);
+            statement.setInt(1, userID);
+            statement.setString(2, date);
+            resultSet = statement.executeQuery();
+            resultSet.next();
+            balance -= resultSet.getFloat(1);
         } catch (SQLException e) {
             e.printStackTrace();
         }

src/main/java/nl/utwente/ing/model/persistentmodel/PersistentModel.java

@@ -470,7 +470,11 @@ public ArrayList<BalanceCandlestick> getBalanceHistory(String sessionID, Interva
             BalanceCandlestick candlestick = new BalanceCandlestick(balance);
             while (index < transactions.size() &&
                     !IntervalHelper.isSmallerThan(interval, transactions.get(index).getDate())) {
-                candlestick.mutation(transactions.get(index).getAmount());
+                if (transactions.get(index).getType().equals("deposit")) {
+                    candlestick.mutation(transactions.get(index).getAmount());
+                } else {
+                    candlestick.mutation(transactions.get(index).getAmount() * (-1));
+                }
                 balance = candlestick.getClose();
                 index++;
             }