Prevent removing a tag being used

2 files changed, 14 insertions, 3 deletions

diff --git a/src/db/init.py b/src/db/init.py
index 6b4cbea..77920cf 100644
--- a/src/db/init.py
+++ b/src/db/init.py
@@ -8,9 +8,9 @@ def init(path):
 
     database = sqlite3.connect(path)
 
-    if is_db_new:
+    cursor = database.cursor()
 
-        cursor = database.cursor()
+    if is_db_new:
 
         cursor.execute(
             " CREATE TABLE IF NOT EXISTS tasks("
@@ -43,6 +43,8 @@ def init(path):
             "   PRIMARY KEY (task_id, tag_id)"
             " )")
 
-        database.commit()
+    cursor.execute("PRAGMA foreign_keys = ON")
+
+    database.commit()
 
     return database
diff --git a/src/db/task_tags.py b/src/db/task_tags.py
index 34366e0..93dc627 100644
--- a/src/db/task_tags.py
+++ b/src/db/task_tags.py
@@ -4,6 +4,15 @@ from typing import List
 
 from model.task_tag import TaskTag
 
+def one_is_used(cursor: Cursor, tag_ids: List[int]) -> bool:
+    if len(tag_ids) >= 1:
+        cursor.execute(
+            "SELECT task_id FROM task_tags WHERE tag_id IN (%s) LIMIT 1" % ",".join("?"*len(tag_ids)),
+            tag_ids)
+        return len(cursor.fetchall()) == 1
+    else:
+        return False
+
 def get(cursor: Cursor) -> List[TaskTag]:
     cursor.execute("SELECT task_id, tag_id FROM task_tags")
     return [TaskTag(r[0], r[1]) for r in cursor.fetchall()]