Rollback dataset to previous snapshot pointer in Python

from datetime import datetime, timedelta


class SnapshotManager:
    def __init__(self):
        self.snapshots = {}  # timestamp -> data
        self.current_pointer = None

    def create_snapshot(self, data):
        timestamp = datetime.now()
        self.snapshots[timestamp] = data
        self.current_pointer = timestamp
        return timestamp

    def rollback(self, target_time):
        previous_times = [t for t in self.snapshots if t <= target_time]
        if not previous_times:
            raise ValueError("No snapshot found at or before target time")
        self.current_pointer = max(previous_times)
        return self.current_pointer

    def get_current_data(self):
        return self.snapshots[self.current_pointer]


if __name__ == "__main__":
    manager = SnapshotManager()

    manager.create_snapshot({"version": 1, "items": ["a", "b"]})
    manager.create_snapshot({"version": 2, "items": ["a", "b", "c"]})
    manager.create_snapshot({"version": 3, "items": ["a", "b", "c", "d"]})

    target = datetime.now() - timedelta(seconds=1)
    rolled_back_to = manager.rollback(target)
    print(f"Rolled back to: {rolled_back_to}")
    print(f"Data: {manager.get_current_data()}")