Build a time machine

db_setup/create_triggers.py

@@ -242,11 +242,6 @@ def create_triggers(cursor: sqlite3.Cursor):
                 WHEN NEW.seller_id IS NULL
                 BEGIN SELECT RAISE(ROLLBACK, 'seller_id must not be null for new transactions.'); END
                 ''')
-    cursor.execute('''
-                CREATE TRIGGER IF NOT EXISTS order_history_no_update
-                BEFORE UPDATE ON order_history
-                BEGIN SELECT RAISE(ROLLBACK, 'Can not change order history.'); END
-                ''')
 
 
 def create_combination_cluster_triggers(cursor: sqlite3.Cursor,

model.py

@@ -1504,6 +1504,45 @@ def loan_id_exists(loan_id):
     return current_cursor.fetchone()[0]
 
 
+def time_travel(delta_t):
+    """
+    Modify all timestamps in the database by -delta_t.
+    A positive delta_t travels into the future, a negative delta_t to the past.
+    Be careful with time travel into the past though.
+    :param delta_t: time in seconds to travel
+    """
+    tables = execute('''
+    SELECT name
+    FROM sqlite_master
+    WHERE type = 'table'
+    ''').fetchall()
+
+    for (table,) in tables:
+        columns = execute(f'''
+        SELECT * FROM {table}
+        LIMIT 1
+        ''').description
+        timestamp_columns = []
+        for column in columns:
+            name = column[0]
+            if re.search(r'(?:^|_)dt(?:$|_)', name):
+                timestamp_columns.append(name)
+        if len(timestamp_columns) != 0:
+            updates = ',\n'.join(f'"{column}" = "{column}" + ?' for column in timestamp_columns)
+            execute(f'''
+            UPDATE {table}
+            SET {updates}
+            ''', tuple(delta_t for _ in timestamp_columns))
+
+
+def user_has_loan_with_id(user_id, loan_id):
+    execute('''
+        SELECT EXISTS (SELECT * FROM loans WHERE rowid = ? AND user_id = ?)
+        ''', (loan_id, user_id))
+
+    return current_cursor.fetchone()[0]
+
+
 def tender_calendar():
     return execute('''
     SELECT dt, mro_interest, maturity_dt
@@ -1522,7 +1561,7 @@ def required_minimum_reserve(user_id):
     WHERE b.issuer_id = ?
     AND ownership.user_id = ?
     ''', (user_id, bank_id())).fetchone()[0]
-    return min(0, global_control_value('cash_reserve_ratio') * borrowed_money - global_control_value('cash_reserve_free_amount'))
+    return max(0, global_control_value('cash_reserve_ratio') * borrowed_money - global_control_value('cash_reserve_free_amount'))
 
 
 def issue_bond(user_id, ownable_name, coupon, maturity_dt):