"""
Migration script to add the task_blockers association table.
Run this once if you have an existing database.

Usage (from inside the backend container or with the venv active):
    python migrate_add_blockers.py
"""
import sqlite3
import os

db_path = os.path.join(os.path.dirname(__file__), 'bit.db')

if not os.path.exists(db_path):
    print(f"Database not found at {db_path}")
    print("No migration needed — new database will be created with the correct schema.")
    exit(0)

conn = sqlite3.connect(db_path)
cursor = conn.cursor()

try:
    # Check if the table already exists
    cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='task_blockers'")
    if cursor.fetchone():
        print("Table 'task_blockers' already exists. Migration not needed.")
    else:
        cursor.execute("""
            CREATE TABLE task_blockers (
                task_id       INTEGER NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
                blocked_by_id INTEGER NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
                PRIMARY KEY (task_id, blocked_by_id)
            )
        """)
        conn.commit()
        print("Successfully created 'task_blockers' table.")
except Exception as e:
    print(f"Error during migration: {e}")
    conn.rollback()
finally:
    conn.close()