Refine api style for change set

script/sql/api/1.title.sql

@@ -1,37 +1,71 @@
+drop function if exists update_title;
+drop function if exists get_title_update_template;
 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 get_title_schema;
 
 
-drop function if exists set_title;
-
-create function set_title(new_value text) returns json as
+create function get_title_schema() returns jsonb as
 $$
 declare
-    old_value text;
-
-    redo_sql text;
-    undo_sql text;
-    redo_cs json;
-    undo_cs json;
-
 begin
-    select value into old_value from title;
-
-    redo_sql = format('update title set value = ''%s''', new_value);
-    undo_sql = format('update title set value = ''%s''', old_value);
-    redo_cs = format('{"operation": "update", "type": "title", "value": "%s" }', new_value)::json;
-    undo_cs = format('{"operation": "update", "type": "title", "value": "%s" }', old_value)::json;
-    execute add_operation(redo_sql, undo_sql, redo_cs, undo_cs);
-
-    execute redo_sql;
-
-    return redo_cs;
-    
+    return '{"value": {"opetional": false, "readonly": false}}'::jsonb;
 end;
 $$
-language plpgsql;
+language plpgsql;
+
+
+create function get_title() returns jsonb as
+$$
+declare
+    v_value text;
+begin
+    select value into v_value from title;
+    return format('{"value": "%s"}', v_value)::jsonb;
+end;
+$$
+language plpgsql;
+
+
+create function get_title_update_template() returns jsonb as
+$$
+declare
+begin
+    return '{"operation": "update", "type": "title", "value": ""}'::jsonb;
+end;
+$$
+language plpgsql;
+
+
+create function update_title(new jsonb) returns jsonb as
+$$
+declare
+    old jsonb;
+    redo_sql text;
+    undo_sql text;
+    redo_cs jsonb;
+    undo_cs jsonb;
+
+begin
+    assert new->>'operation' = 'update';
+    assert new->>'type' = 'title';
+    assert new ? 'value';
+
+    old := get_title();
+    if old->>'value' = new->>'value' then
+        return '{}'::jsonb;
+    end if;
+
+    redo_sql := format('update title set value = ''%s''', new->>'value');
+    undo_sql := format('update title set value = ''%s''', old->>'value');
+
+    redo_cs := format('{"operation": "update", "type": "title", "value": "%s" }', new->>'value')::jsonb;
+    undo_cs := format('{"operation": "update", "type": "title", "value": "%s" }', old->>'value')::jsonb;
+
+    execute redo_sql;
+    execute add_operation(redo_sql, undo_sql, redo_cs, undo_cs);
+
+    return redo_cs;
+
+end;
+$$
+language plpgsql;