db_instance = None

def __init__(self):

try:

# make the connection and create a cursor for checking if tables exists.

self.db_instance = sqlite3.connect("mynotes.db")

cursor = self.db_instance.cursor()

print("Database connection established!")

print("Checking existing tables...")

# check if table exists, fetch results and run migrations if table doesn't exist.

cursor.execute("SELECT name FROM sqlite_master WHERE name IN ('notes')")

records = cursor.fetchall()

if (len(records) == 1):

print("Table exists.")

else:

print("Table doesn't exists. Running migrations.")

self.run_migrations()

# close the cursor

print("Done.")

cursor.close()

except sqlite3.Error as error:

print("Error connecting to database: ", error)

# This method returns the current instance of the connection to the database.

def get_instance(self):

return self.db_instance

# This method destroy the instance of the current connection to the database.

def destroy_instance(self):

print("Destroying connection instance.")

if not (self.db_instance is None):

print("Destroyed.")

self.db_instance.close()

return True

return False

# This method runs the migrations for the database.

def run_migrations(self):

try:

print("Creating notes table.")

cursor = self.db_instance.cursor()

cursor.execute("CREATE TABLE IF NOT EXISTS notes (ID INTEGER PRIMARY KEY AUTOINCREMENT, text VARCHAR(2000), created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP)")

self.db_instance.commit()

cursor.close()

except sqlite3.Error as error:

print("Error running migration: ", error)

return False

return True