project-init

crud.py

@@ -0,0 +1,205 @@
+"""
+CRUD operations for GUARDIAN, STUDENT and ATTENDANCE.
+
+Every function takes an open pymysql connection as its first argument and
+manages its own commit/rollback. All functions return plain data
+(dicts/lists/bool) so this module has no dependency on the UI layer.
+"""
+
+import pymysql
+
+
+class CrudError(Exception):
+	"""Raised for expected, user-facing data errors (bad FK, duplicate key, etc)."""
+	pass
+
+
+def _run(conn, sql, params=None, fetch=None):
+	"""
+	Helper: execute a statement, commit, and optionally fetch results.
+	fetch: None (no fetch), 'one', or 'all'
+	Translates common MySQL errors into CrudError with a friendly message.
+	"""
+	try:
+		with conn.cursor() as cur:
+			cur.execute(sql, params or ())
+			result = None
+			if fetch == "one":
+				result = cur.fetchone()
+			elif fetch == "all":
+				result = cur.fetchall()
+			conn.commit()
+			return result if fetch else cur.rowcount
+	except pymysql.err.IntegrityError as e:
+		conn.rollback()
+		code = e.args[0] if e.args else None
+		if code == 1062:
+			raise CrudError("A record with that primary/unique key already exists.")
+		if code in (1451, 1452):
+			raise CrudError(
+				"That operation violates a foreign key constraint "
+				"(referenced record missing, or still referenced by other rows)."
+			)
+		raise CrudError(f"Database integrity error: {e}")
+	except pymysql.err.DataError as e:
+		conn.rollback()
+		raise CrudError(f"Invalid data for one or more fields: {e}")
+	except pymysql.err.MySQLError as e:
+		conn.rollback()
+		raise CrudError(f"Database error: {e}")
+
+
+# ---------------------------------------------------------------- GUARDIAN --
+
+def create_guardian(conn, guid, gname, gphone, gaddress):
+	_run(
+		conn,
+		"INSERT INTO GUARDIAN (GUID, GName, GPhone, GAddress) VALUES (%s, %s, %s, %s)",
+		(guid, gname, gphone, gaddress),
+	)
+
+
+def get_guardian(conn, guid):
+	return _run(conn, "SELECT * FROM GUARDIAN WHERE GUID = %s", (guid,), fetch="one")
+
+
+def list_guardians(conn):
+	return _run(conn, "SELECT * FROM GUARDIAN ORDER BY GUID", fetch="all")
+
+
+def update_guardian(conn, guid, gname=None, gphone=None, gaddress=None):
+	fields, params = [], []
+	if gname is not None:
+		fields.append("GName = %s")
+		params.append(gname)
+	if gphone is not None:
+		fields.append("GPhone = %s")
+		params.append(gphone)
+	if gaddress is not None:
+		fields.append("GAddress = %s")
+		params.append(gaddress)
+	if not fields:
+		return 0
+	params.append(guid)
+	return _run(conn, f"UPDATE GUARDIAN SET {', '.join(fields)} WHERE GUID = %s", params)
+
+
+def delete_guardian(conn, guid):
+	return _run(conn, "DELETE FROM GUARDIAN WHERE GUID = %s", (guid,))
+
+
+# ----------------------------------------------------------------- STUDENT --
+
+def create_student(conn, roll_number, sname, sdateofbirth, guid):
+	_run(
+		conn,
+		"INSERT INTO STUDENT (RollNumber, SName, SDateofBirth, GUID) VALUES (%s, %s, %s, %s)",
+		(roll_number, sname, sdateofbirth, guid),
+	)
+
+
+def get_student(conn, roll_number):
+	return _run(conn, "SELECT * FROM STUDENT WHERE RollNumber = %s", (roll_number,), fetch="one")
+
+
+def list_students(conn):
+	return _run(
+		conn,
+		"""
+		SELECT s.RollNumber, s.SName, s.SDateofBirth, s.GUID, g.GName AS GuardianName
+		FROM STUDENT s
+		LEFT JOIN GUARDIAN g ON s.GUID = g.GUID
+		ORDER BY s.RollNumber
+		""",
+		fetch="all",
+	)
+
+
+def update_student(conn, roll_number, sname=None, sdateofbirth=None, guid=None):
+	fields, params = [], []
+	if sname is not None:
+		fields.append("SName = %s")
+		params.append(sname)
+	if sdateofbirth is not None:
+		fields.append("SDateofBirth = %s")
+		params.append(sdateofbirth)
+	if guid is not None:
+		fields.append("GUID = %s")
+		params.append(guid)
+	if not fields:
+		return 0
+	params.append(roll_number)
+	return _run(conn, f"UPDATE STUDENT SET {', '.join(fields)} WHERE RollNumber = %s", params)
+
+
+def delete_student(conn, roll_number):
+	return _run(conn, "DELETE FROM STUDENT WHERE RollNumber = %s", (roll_number,))
+
+
+# --------------------------------------------------------------- ATTENDANCE --
+
+def mark_attendance(conn, attendance_date, roll_number, status):
+	"""Insert attendance; if a record for that date+student exists, update it instead."""
+	existing = _run(
+		conn,
+		"SELECT 1 FROM ATTENDANCE WHERE AttendanceDate = %s AND RollNumber = %s",
+		(attendance_date, roll_number),
+		fetch="one",
+	)
+	if existing:
+		_run(
+			conn,
+			"UPDATE ATTENDANCE SET AttendanceStatus = %s "
+			"WHERE AttendanceDate = %s AND RollNumber = %s",
+			(status, attendance_date, roll_number),
+		)
+		return "updated"
+	else:
+		_run(
+			conn,
+			"INSERT INTO ATTENDANCE (AttendanceDate, RollNumber, AttendanceStatus) "
+			"VALUES (%s, %s, %s)",
+			(attendance_date, roll_number, status),
+		)
+		return "created"
+
+
+def get_attendance(conn, attendance_date, roll_number):
+	return _run(
+		conn,
+		"SELECT * FROM ATTENDANCE WHERE AttendanceDate = %s AND RollNumber = %s",
+		(attendance_date, roll_number),
+		fetch="one",
+	)
+
+
+def list_attendance_by_date(conn, attendance_date):
+	return _run(
+		conn,
+		"""
+		SELECT a.AttendanceDate, a.RollNumber, s.SName, a.AttendanceStatus
+		FROM ATTENDANCE a
+		JOIN STUDENT s ON a.RollNumber = s.RollNumber
+		WHERE a.AttendanceDate = %s
+		ORDER BY a.RollNumber
+		""",
+		(attendance_date,),
+		fetch="all",
+	)
+
+
+def list_attendance_by_student(conn, roll_number):
+	return _run(
+		conn,
+		"SELECT * FROM ATTENDANCE WHERE RollNumber = %s ORDER BY AttendanceDate",
+		(roll_number,),
+		fetch="all",
+	)
+
+
+def delete_attendance(conn, attendance_date, roll_number):
+	return _run(
+		conn,
+		"DELETE FROM ATTENDANCE WHERE AttendanceDate = %s AND RollNumber = %s",
+		(attendance_date, roll_number),
+	)