Support transaction to commit or rollback, this will modify operation tree

api/__init__.py

@@ -5,6 +5,7 @@ from .project import copy_project
 from .operation import execute_undo as undo
 from .operation import execute_redo as redo
 from .operation import take_snapshot, pick_snapshot
+from .operation import have_transaction, start_transaction, commit_transaction, rollback_transaction
 
 from .s0_base import is_node, is_junction, is_reservoir, is_tank
 from .s0_base import is_link, is_pipe, is_pump, is_valve

api/operation.py

@@ -1,6 +1,24 @@
-from psycopg.rows import dict_row
+from psycopg.rows import dict_row, Row
 from .connection import g_conn_dict as conn
 
+def _get_current_transaction(name: str) -> Row | None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select id from transaction_operation")
+        return cur.fetchone()
+
+def _get_current_transaction_id(name: str) -> int:
+    row = _get_current_transaction(name)
+    return int(row['id'])
+
+def _remove_transaction(name: str) -> None:
+    with conn[name].cursor() as cur:
+        cur.execute(f"delete from transaction_operation")
+
+def _remove_operation(name: str, id: int) -> None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"delete from operation where id = {id}")
+        return int(cur.fetchone()['id'])
+
 def _get_parents(name: str, id: int) -> list[int]:
     ids = [id]
     with conn[name].cursor(row_factory=dict_row) as cur:
@@ -42,7 +60,7 @@ def _query_redo(name: str, id: str) -> dict[str, str]:
         cur.execute(f"select redo from operation where id = {id}")
         return cur.fetchone()['redo']
 
-def _set_redo_child(name: str, id: str, child: str) -> None:
+def _set_redo_child(name: str, id: int, child: int | str) -> None:
     with conn[name].cursor() as cur:
         cur.execute(f"update operation set redo_child = {child} where id = {id}")
 
@@ -56,8 +74,19 @@ def add_operation(name: str, redo: str, undo: str) -> None:
     old = _get_current_operation(name)
     _update_current_operation(name, old, curr)
 
-def execute_undo(name: str) -> None:
+def execute_undo(name: str, discard: bool = False) -> None:
     curr = _get_current_operation(name)
+
+    # transaction control
+    tran = _get_current_transaction(name)
+    if int(tran['id']) >= 0:
+        if bool(tran['strict']): # strict mode disallow undo
+            print("Do not allow to undo in strict transaction mode!")
+            return
+        elif tran <= curr: # normal mode disallow undo start point
+            print("Do not allow to undo transaction start point!")
+            return
+
     row = _query_undo(name, curr)
     undo = row['undo']
     if undo == '':
@@ -65,11 +94,14 @@ def execute_undo(name: str) -> None:
         return
 
     parent = int(row['parent'])
-    _set_redo_child(name, parent, curr)
+    _set_redo_child(name, parent, 'NULL' if discard else curr)
 
     _execute(name, undo)
     _update_current_operation(name, curr, parent)
 
+    if discard:
+        _remove_operation(name, curr)
+
 def execute_redo(name: str) -> None:
     curr = _get_current_operation(name)
     redoChild = _query_redo_child(name, curr)
@@ -141,11 +173,36 @@ def pick_snapshot(name: str, tag: str) -> None:
 # can not undo a committed transaction or redo a rollback transaction.
 # it may remove snapshot tag if snapshot in a rollback transaction
 
-def start_transaction(name: str) -> None:
+def have_transaction(name: str) -> bool:
-    pass
+    return _get_current_transaction_id(name) >= 0
+
+def start_transaction(name: str, strict: bool = False) -> None:
+    if have_transaction(name):
+        print("Only support single transaction now, please commit/rollback current transaction!")
+        return
+
+    curr = _get_current_operation(name)
+
+    with conn[name].cursor() as cur:
+        cur.execute(f"insert into transaction_operation (id, strict) values ({curr}, {strict});")
 
 def commit_transaction(name: str) -> None:
-    pass
+    if not have_transaction(name):
+        print("No active transaction!")
+        return
+
+    _remove_transaction(name)
 
 def rollback_transaction(name: str) -> None:
-    pass
+    tran = _get_current_transaction_id(name)
+    if tran >= 0:
+        print("No active transaction!")
+        return
+
+    curr = _get_current_operation(name)
+    curr_parents = _get_parents(name, curr)
+
+    for i in range(curr_parents.index(tran)):
+        execute_undo(name, True)
+    
+    _remove_transaction(name)