going somewhere.

migrations/create_tables_001.sql

@@ -65,5 +65,6 @@ CREATE TABLE IF NOT EXISTS cashed_cheques
 
     FOREIGN KEY (underlying_security) REFERENCES securities (id),
     FOREIGN KEY (drawer_user_id) REFERENCES users (id),
-    FOREIGN KEY (drawer_account_id) REFERENCES accounts (id)
+    FOREIGN KEY (drawer_account_id) REFERENCES accounts (id),
+    CONSTRAINT double_spending UNIQUE (drawer_user_id, cheque_number) -- no double spending
 );

src/db/_accounts.rs

@@ -26,6 +26,10 @@ impl Account {
             security: Security::from_row(row)?,
         });
     }
+
+    pub fn raw_amount(&self) -> u32 {
+        self.amount
+    }
 }
 
 pub fn list_accounts<'a>(conn: &Connection) -> Result<Vec<Account>> {
@@ -48,7 +52,7 @@ pub fn list_accounts<'a>(conn: &Connection) -> Result<Vec<Account>> {
     return Ok(ret);
 }
 
-pub fn get_account_by_id(tx: &Transaction, id: u32) -> Result<Account> {
+pub fn get_account_by_id(tx: &Transaction, id: &AccountId) -> Result<Account> {
     let q = "SELECT acc.id AS acc_id,
                           acc.amount AS acc_amount,
                           UNIXEPOCH(acc.timestamp) AS acc_timestamp,
@@ -66,7 +70,8 @@ pub fn create_account(tx: &Transaction, sec: &SecurityId, user: &UserId) -> Resu
     let q = "INSERT INTO accounts(security, owner, amount, timestamp)
                    VALUES (?1, ?2, 0, CURRENT_TIMESTAMP)";
     tx.execute(q, (sec, user))?;
-    return get_account_by_id(tx, tx.last_insert_rowid() as u32);
+    let id = AccountId::from_id(tx.last_insert_rowid() as u32);
+    return get_account_by_id(tx, &id);
 }
 
 pub fn is_owner(tx: &Transaction, account_id: &AccountId, user_id: &UserId) -> Result<bool> {

src/db/_external_id.rs

@@ -1,4 +1,5 @@
 use std::io::Read;
+use std::fmt;
 
 use regex::{Captures, Regex};
 
@@ -17,16 +18,12 @@ pub trait Id {
     fn get_id(&self) -> u32;
 }
 
-
+impl fmt::Display for SafeId {
-impl ToString for SafeId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    fn to_string(&self) -> String {
+        write!(f, "{}-{}", hex::encode(self.encrypted_id), hex::encode(self.signature))
-        format!("{}-{}",
-                hex::encode(self.encrypted_id),
-                hex::encode(self.signature))
     }
 }
 
-
 impl Id for SafeId {
     type Output = Self;
 
@@ -64,9 +61,9 @@ impl Id for SafeId {
 macro_rules! impl_ids {
     ($T:ident, $prefix:literal) => {
 
-        impl ToString for $T {
+        impl fmt::Display for $T {
-            fn to_string(&self) -> String {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-                format!("{}-{}", $prefix, self.0.to_string())
+                write!(f, "{}-{}", $prefix, self.0)
             }
         }
 

src/services/_transactions.rs

@@ -1,4 +1,4 @@
-use rusqlite::{params, Params, Transaction};
+use rusqlite::{ffi, params, Params, Transaction};
 
 use crate::db::accounts::{Account, get_account_by_id};
 use crate::db::cheques::SecurityEmitterCheque;
@@ -29,21 +29,29 @@ fn _add_cheque_to_cashed_cheques_log(tx: &TransactionHelper,
         )
         VALUES(?1, ?2, ?3, ?4)
     ";
-    tx.execute(q, params![cheque.drawer_user_id,
+    let ret = tx.execute(q, params![cheque.drawer_user_id,
                                      cheque.cheque_number,
                                      cheque.amount,
-                                     cheque.security_id])?;
+                                     cheque.security_id]);
-    Ok(())
+    match ret {
+        Ok(_) => Ok(()),
+        Err(Error::SqlError(rusqlite::Error::SqliteFailure(ffi::Error { code: _, extended_code: 2067 }, _))) =>
+            Err(Error::DoubleSpendingError(format!("Cheque number {} from user {} has already been cached.", cheque.cheque_number, cheque.drawer_user_id))),
+        Err(a) => Err(a)
+    }
 }
 
 fn cash_cheque(tx: &Transaction,
                cheque: &SecurityEmitterCheque,
                account_id: &AccountId) -> CustomResult<()> {
-    // move money to new account
+
     if !securities::is_owner(tx, &cheque.security_id, &cheque.drawer_user_id).map_err(Error::SqlError)? {
         return Err(Error::InvalidDrawer(format!("The drawer is the security owner: {:?}", cheque)));
     }
 
+    // todo:
+    //   1. payee is owner of the account.
+
 
     let myx = TransactionHelper::new(tx);
     _add_securities_to_account(&myx, cheque, account_id)?;
@@ -54,51 +62,103 @@ fn cash_cheque(tx: &Transaction,
 
 
 #[cfg(test)]
-mod test {
+mod test_caching_cheques {
     use rusqlite::{Connection, params};
     use crate::db::accounts::create_account;
 
-    use crate::db::test_utils;
+    use crate::db::{accounts, test_utils};
+    use crate::db::external_id::{Id, SecurityId, UserId};
+    use crate::db::users::User;
     use crate::migration;
 
     use super::*;
 
-    fn setup() -> Connection {
+    fn setup_conn() -> Connection {
         let mut conn = Connection::open_in_memory().unwrap();
         migration::apply_migrations(&mut conn).unwrap();
         return conn;
     }
 
-
+    fn setup_basic() -> (Connection, UserId, SecurityId, UserId, AccountId) {
-    #[test]
+        let mut conn = setup_conn();
-    fn test_basic() -> Result<(), Error> {
-        let mut conn = setup();
         let tx = conn.transaction().unwrap();
         let (users, securities, accounts) = test_utils::setup_basic_environment(&tx).unwrap();
         let sec = securities.get(0).unwrap();
         let drawer = users.get(0).unwrap();
         let payee = users.get(1).unwrap();
-        let amount: u32 = 1000;
+        let payee_account = create_account(&tx, &sec.id(), &payee.id()).unwrap();
-        let payee_account = create_account(&tx, & sec.id(), & payee.id()).unwrap();
 
         tx.commit().unwrap();
+        (conn, drawer.id(), sec.id(), payee.id(), payee_account.id())
+    }
+
+
+    #[test]
+    fn test_basic_happy_path() -> CustomResult<()> {
+        let (mut conn, drawer, sec, payee, payee_account) = setup_basic();
         let tx = conn.transaction().unwrap();
 
-
-        // let tx = conn.transaction()?;
-        // SecurityEmitterCheque::new(securities.get())
         let cheque = SecurityEmitterCheque::new(
-            drawer.id(),
+            drawer,
-            sec.id(),
+            sec,
-            payee.id(),
+            payee,
-            amount,
+            1000,
             99,
         );
 
-
+        cash_cheque(&tx, &cheque, &payee_account)?;
-        cash_cheque(&tx, &cheque, &payee_account.id())?;
-
         tx.commit().unwrap();
+
+        let tx = conn.transaction().unwrap();
+        let acc = get_account_by_id(&tx, &payee_account).unwrap();
+        assert_eq!(acc.raw_amount(), 1000);
+
         Ok(())
     }
+
+    #[test]
+    fn test_double_spend() -> CustomResult<()> {
+        let (mut conn, drawer, sec, payee, payee_account) = setup_basic();
+        let amount: u32 = 1000;
+        let tx = conn.transaction().unwrap();
+
+        let cheque = SecurityEmitterCheque::new(
+            drawer,
+            sec,
+            payee,
+            1000,
+            99,
+        );
+
+        cash_cheque(&tx, &cheque, &payee_account)?;
+        tx.commit().unwrap();
+        let tx = conn.transaction().unwrap();
+
+        let ret = cash_cheque(&tx, &cheque, &payee_account);
+        match ret {
+            Err(Error::DoubleSpendingError(_)) => Ok(()),
+            _ => Err(Error::Testing("Expected double spending error here.".to_string()))
+        }
+    }
+
+    #[test]
+    fn test_invalid_drawer() -> CustomResult<()> {
+        let (mut conn, drawer, sec, payee, payee_account) = setup_basic();
+        let amount: u32 = 1000;
+        let tx = conn.transaction().unwrap();
+        let not_currency_owner = UserId::from_id(drawer.get_id() + 72623);
+        let cheque = SecurityEmitterCheque::new(
+            not_currency_owner,
+            sec,
+            payee,
+            1000,
+            99,
+        );
+
+        let ret = cash_cheque(&tx, &cheque, &payee_account);
+        match ret {
+            Err(Error::InvalidDrawer(_)) => Ok(()),
+            _ => Err(Error::Testing("Expected invalid drawer here.".to_string()))
+        }
+    }
 }

src/util.rs

@@ -4,6 +4,8 @@ use rusqlite::{Params, Transaction};
 pub enum Error {
     SqlError(rusqlite::Error),
     InvalidDrawer(String),
+    DoubleSpendingError(String),
+    Testing(String),
 }
 
 pub type CustomResult<T, E = Error> = Result<T, E>;