I should be working by now.

src/services/_transactions.rs

@@ -1,4 +1,4 @@
-use rusqlite::{ffi, params, Params, Savepoint, Transaction};
+use rusqlite::{Connection, ffi, params, Params, Savepoint, Transaction};
 
 use crate::db::{accounts, securities};
 use crate::db::accounts::{Account, get_account_by_id};
@@ -7,15 +7,19 @@ use crate::db::external_id::AccountId;
 use crate::db::securities::get_security_by_id;
 use crate::util::*;
 
-fn _move_securities(tx: &TransactionHelper,
+fn _move_securities(tx: &Savepoint,
                     cheque: &SecurityEmitterCheque,
                     account_id: &AccountId) -> CustomResult<()> {
-    accounts::add_to_account(tx, &cheque.drawer_account_id, -cheque.amount)?;
-    accounts::add_to_account(tx, account_id, cheque.amount)?;
+    let drawer_receipt = accounts::add_to_account(tx, &cheque.drawer_account_id, -cheque.amount)?;
+    let payee_receipt = accounts::add_to_account(tx, account_id, cheque.amount)?;
+    if drawer_receipt.amount < 0 {
+        let m = format!("Drawer of {:?} does not have sufficient amount in account.", cheque);
+        return Err(Error::InvalidAmount(m));
+    }
     Ok(())
 }
 
-fn _add_cheque_to_cashed_cheques_log(tx: &TransactionHelper,
+fn _add_cheque_to_cashed_cheques_log(tx: &Connection,
                                      cheque: &SecurityEmitterCheque,
                                      account_id: &AccountId) -> Result<(), Error> {
     let q = "
@@ -30,7 +34,7 @@ fn _add_cheque_to_cashed_cheques_log(tx: &TransactionHelper,
     let ret = tx.execute(q, params![cheque.drawer_user_id,
                                      cheque.cheque_number,
                                      cheque.amount,
-                                     cheque.security_id]);
+                                     cheque.security_id]).map_err(Error::SqlError);
     match ret {
         Ok(_) => Ok(()),
         Err(Error::SqlError(rusqlite::Error::SqliteFailure(ffi::Error { code: _, extended_code: 2067 }, _))) =>
@@ -39,27 +43,41 @@ fn _add_cheque_to_cashed_cheques_log(tx: &TransactionHelper,
     }
 }
 
-fn cash_cheque(tx: &Transaction,
-               cheque: &SecurityEmitterCheque,
-               account_id: &AccountId) -> CustomResult<()> {
-    if !accounts::is_owner(&tx, &cheque.drawer_account_id, &cheque.drawer_user_id).map_err(Error::SqlError)? {
+fn cash_cheque_unsafe(savepoint: &Savepoint,
+                      cheque: &SecurityEmitterCheque,
+                      account_id: &AccountId) -> CustomResult<()> {
+    if cheque.amount < 0 {
+        return Err(Error::InvalidAmount(format!("The cheque {:?} has a negative amount.", cheque)));
+    }
+    if !accounts::is_owner(&savepoint, &cheque.drawer_account_id, &cheque.drawer_user_id).map_err(Error::SqlError)? {
         return Err(Error::InvalidDrawer(format!("The drawer is the security owner: {:?}", cheque)));
     }
 
-    if !accounts::is_owner(&tx, account_id, &cheque.payee_user_id).map_err(Error::SqlError)? {
+    if !accounts::is_owner(&savepoint, account_id, &cheque.payee_user_id).map_err(Error::SqlError)? {
         return Err(Error::InvalidPayee(format!("Trying to cash the cheque {:?} in \
         an account {:?} that is not owned by the payee.", cheque, account_id)));
     }
-
-    let myx = TransactionHelper::new(tx);
-    _move_securities(&myx, cheque, account_id)?;
-    _add_cheque_to_cashed_cheques_log(&myx, cheque, account_id)?;
-
-    // savepoint.rollback().map_err(Error::SqlError)?;
-    // create transaction loggetAllPurchaseHistory
+    _move_securities(&savepoint, cheque, account_id)?;
+    _add_cheque_to_cashed_cheques_log(&savepoint, cheque, account_id)?;
     Ok(())
 }
 
+fn cash_cheque(tx: &mut Transaction,
+               cheque: &SecurityEmitterCheque,
+               account_id: &AccountId) -> CustomResult<()> {
+    let mut savepoint = tx.savepoint().map_err(Error::SqlError)?;
+    let ret = cash_cheque_unsafe(&savepoint, cheque, account_id);
+    match ret {
+        Err(_) => {
+            savepoint.rollback().map_err(Error::SqlError)?;
+            ret
+        }
+        Ok(_) => {
+            savepoint.commit().map_err(Error::SqlError)
+        }
+    }
+}
+
 
 #[cfg(test)]
 mod test_caching_cheques {
@@ -115,6 +133,21 @@ mod test_caching_cheques {
         Ok(())
     }
 
+    #[test]
+    fn test_negative_cheque() -> CustomResult<()> {
+        let (mut conn, drawer, payee, payee_account) = setup_basic();
+        let mut tx = conn.transaction().unwrap();
+
+        let cheque = SecurityEmitterCheque::new(
+            drawer, payee, -1000, 99);
+
+        let ret = cash_cheque(&mut tx, &cheque, &payee_account);
+        match ret {
+            Err(Error::InvalidAmount(_)) => Ok(()),
+            _ => Err(Error::Testing("Expected double spending error here.".to_string()))
+        }
+    }
+
     #[test]
     fn test_double_spend() -> CustomResult<()> {
         let (mut conn, drawer, payee, payee_account) = setup_basic();