Try new operation table

script/sql/api/1.title.sql

@@ -0,0 +1,37 @@
+drop function if exists get_title;
+
+create function get_title() returns text as
+$$
+select value from title as result;
+$$
+language sql;
+
+
+drop function if exists set_title;
+
+create function set_title(new_value text) returns json as
+$$
+declare
+    old_value text;
+
+    redo_sql text;
+    undo_sql text;
+    redo_cs json;
+    undo_cs json;
+
+begin
+    select value into old_value from title;
+
+    redo_sql = format('update title set value = ''%s''', new_value);
+    undo_sql = format('update title set value = ''%s''', old_value);
+    redo_cs = format('{"operation": "update", "type": "title", "value": "%s" }', new_value)::json;
+    undo_cs = format('{"operation": "update", "type": "title", "value": "%s" }', old_value)::json;
+    execute add_operation(redo_sql, undo_sql, redo_cs, undo_cs);
+
+    execute redo_sql;
+
+    return redo_cs;
+    
+end;
+$$
+language plpgsql;

script/sql/api/operation.sql

@@ -0,0 +1,85 @@
+drop function if exists get_current_operation;
+
+create function get_current_operation() returns integer as
+$$
+select id from current_operation as result;
+$$
+language sql;
+
+
+drop function if exists add_operation;
+
+create function add_operation(redo_sql text, undo_sql text, redo_cs json, undo_cs json) returns void as
+$$
+declare
+    parent_id integer;
+    op_id integer;
+
+begin
+    parent_id := get_current_operation();
+
+    insert into operation (id, redo, undo, parent, redo_change_set, undo_change_set)
+        values (default, redo_sql, undo_sql, parent_id, redo_cs, undo_cs);
+
+    select max(id) into op_id from operation;
+
+    update current_operation set id = op_id where id = parent_id;
+
+end;
+$$
+language plpgsql;
+
+
+drop function if exists execute_undo;
+
+create function execute_undo(discard boolean) returns json as
+$$
+#print_strict_params on
+
+declare
+    op_row operation%ROWTYPE;
+
+begin
+    select * into strict op_row from operation where id = get_current_operation();
+    if op_row.undo = '' then
+        return '{}'::json;
+    end if;
+
+    execute op_row.undo;
+
+    -- update foreign key
+    update current_operation set id = op_row.parent where id = op_row.id;
+
+    if discard then
+        -- update foreign key
+        update operation set redo_child = null where id = op_row.parent;
+        -- on delete cascade => child & snapshot
+        delete from operation where id = op_row.id;
+    else
+        update operation set redo_child = op_row.id where id = op_row.parent;
+    end if;
+
+    return op_row.undo_change_set;
+
+end;
+$$
+language plpgsql;
+
+
+-- create function execute_redo() returns json as
+-- $$
+-- #print_strict_params on
+-- 
+-- declare
+--     op_id integer;
+--     redo_c integer;
+--     redo_row operation%ROWTYPE;
+-- 
+-- begin
+--     op_id := get_current_operation();
+-- 
+--     select redo_child into redo_c from operation where id = op_id;
+-- 
+-- end;
+-- $$
+-- language plpgsql;

script/sql/create/operation.sql

@@ -1,36 +1,25 @@
-create type api_operation as enum ('init', 'add', 'delete', 'update');
-
 create table operation
 (
   id serial primary key
 , redo text not null
 , undo text not null
-, parent integer references operation(id)
-, redo_child integer references operation(id)
-, api_id text not null
-, api_op api_operation not null
-, api_object_type text not null
-, api_object_id text not null
-, api_object_properties text[]
+, parent integer references operation(id) on delete cascade
+, redo_child integer references operation(id) -- must update before delete
+, redo_change_set json
+, undo_change_set json
 );
 
-insert into operation (id, redo, undo, api_id, api_op, api_object_type, api_object_id) values (0, '', '', '', 'init', '', '');
+insert into operation (id, redo, undo) values (0, '', '');
 
 create table current_operation
 (
-  id integer primary key references operation(id)
+  id integer primary key references operation(id) -- must update before delete
 );
 
 insert into current_operation (id) values (0);
 
 create table snapshot_operation
 (
-  id integer primary key references operation(id)
+  id integer primary key references operation(id) on delete cascade
 , tag text not null unique
 );
-
-create table transaction_operation
-(
-  id integer primary key references operation(id)
-, strict boolean not null default false
-);

script/sql/drop/operation.sql

@@ -5,5 +5,3 @@ drop table if exists snapshot_operation;
 drop table if exists current_operation;
 
 drop table if exists operation;
-
-drop type if exists api_operation;

script/template.py

@@ -30,7 +30,12 @@ sql_create = [
     "sql/create/26.labels.sql",
     "sql/create/27.backdrop.sql",
     "sql/create/28.end.sql",
-    "sql/create/operation.sql"
+    "sql/create/operation.sql",
+]
+
+sql_api = [
+    "sql/api/operation.sql",
+    "sql/api/1.title.sql"
 ]
 
 sql_drop = [
@@ -76,6 +81,10 @@ def create_template():
                 with open(sql, "r") as f:
                     cur.execute(f.read())
                 print(f'executed {sql}')
+            for sql in sql_api:
+                with open(sql, "r") as f:
+                    cur.execute(f.read())
+                print(f'executed {sql}')
         conn.commit()
 
 def have_template():