Requirements

Let's design a navigation and alerts system akin to Google Maps, but focusing on the core LLD aspects. Forget the massive scale and distributed nature; we're building an in-memory simulation to showcase excellent design. Imagine you're building a system for a car's navigation unit. The system needs to: 1. Calculate routes between two points. 2. Provide turn-by-turn directions. 3. Alert the driver about upcoming events (traffic jams, accidents, speed cameras, etc.) along the route. 4. Dynamically re-route based on real-time events. This problem requires a strong understanding of OOD principles and design patterns to create a flexible, maintainable, and testable system. The heart of the challenge lies in the efficient and scalable (within memory constraints) route management and alert triggering mechanisms. # Requirements ## Functional Requirements 1. **Route Calculation:** * Given a start and end location (latitude and longitude), calculate a route. * Support different routing modes: Fastest, Shortest. * Return a route represented as a list of `NavigationPoints`. * Consider road restrictions (one-way streets, blocked roads - simulated). 2. **Turn-by-Turn Directions:** * Provide human-readable directions for each `NavigationPoint` along the route. * Directions should include distance to the next turn, type of turn (left, right, straight), and street name. 3. **Alerting:** * Register various types of alerts (TrafficJam, Accident, SpeedCamera) along specific road segments. * As the user progresses along the route, trigger alerts relevant to their current location. * Alerts should provide relevant information (severity of traffic jam, type of accident, speed limit). * Alerts should have a priority (e.g., Accident > Speed Camera). 4. **Re-routing:** * When an alert (e.g., traffic jam) significantly impacts the route, automatically calculate a new route. * The re-routing algorithm should consider the severity and duration of the alert. * Allow the user to accept or reject the re-route. 5. **Data Input:** * Provide a way to input map data (roads, intersections, points of interest). This can be simplified by loading from a file at startup. * Provide a way to add/remove alerts dynamically (e.g., through an API). ## Non-Functional Requirements 1. **Modularity:** The system should be composed of loosely coupled modules with well-defined interfaces. This allows for easy modification and extension of individual components without affecting the entire system. 2. **Extensibility:** The system should be designed to easily accommodate new types of alerts, routing modes, and map data sources. 3. **Testability:** Each module should be easily testable in isolation. Unit tests should cover all critical functionalities. 4. **Thread Safety:** The system may need to handle concurrent requests (e.g., multiple users requesting routes). Ensure that shared data structures are accessed and modified in a thread-safe manner. Pay close attention to potential race conditions and deadlocks. Focus on the data structures that store the routes, alerts, and map data. Consider thread-safe collections, locks, or atomic operations as appropriate. The route calculation itself may be multi-threaded to improve performance. 5. **Maintainability:** The code should be well-documented, and easy to understand and maintain. Use meaningful variable names, comments, and consistent coding style. 6. **Performance:** Route calculation should be reasonably fast (within a few seconds for typical routes). Alert triggering should be instantaneous. ## Core Entities 1. **`NavigationPoint`:** Represents a point on the route (latitude, longitude). 2. **`Route`:** Represents a sequence of `NavigationPoints`. Includes methods for calculating distance, getting directions, and checking for alerts. 3. **`Router`:** Interface responsible for calculating routes. Implementations include `FastestRoute` and `ShortestRoute`. 4. **`Alert`:** Base class for different types of alerts (TrafficJam, Accident, SpeedCamera). Includes properties like location, severity, and message. 5. **`AlertManager`:** Responsible for managing alerts and triggering them when the user is near an alert location. 6. **`MapData`:** Represents the underlying map data (roads, intersections). Could be loaded from a file or a database. This class must be thread-safe. 7. **`DirectionService`:** Responsible for converting `NavigationPoint`s into human-readable directions. 8. **`RoadSegment`**: Represents a road segment between two NavigationPoints. Contains information like speed limit, one-way restrictions, etc. This is the smallest unit of the map that can have an Alert.

Design Navigation Alerts System. (Similar like Google Map Functionality.)

Requirements

Think like an Architect

Premium Content