05. Building Block View

Level 1 — System

The entire system is a single CLI application (one Python process). No external services or databases.

---

Level 2 — Components

Component Overview

Component	Layer	Responsibility
__main__	Adapter	Entry point — wires dependencies, reads stdin, writes stdout
InputParser	Adapter	Parses raw text into Plateau and (Rover, [Command]) pairs
OutputFormatter	Adapter	Serialises Rover state to x y HEADING text
MissionController	Application	Orchestrates the mission — iterates rovers and their command sequences
Plateau	Domain	Value object holding grid dimensions; exposes is_within(x, y)
Rover	Domain	Entity holding (x, y, heading); applies commands one at a time
Heading	Domain	Enum N | E | S | W; owns rotation and movement-delta logic
Command	Domain	Protocol / callable — TurnLeft, TurnRight, MoveForward

---

Domain Model

Plateau
  - width: int
  - height: int
  + is_within(x: int, y: int) → bool

Rover
  - x: int
  - y: int
  - heading: Heading
  + execute(command: Command) → None

Heading (Enum)
  N | E | S | W
  + turn_left()  → Heading
  + turn_right() → Heading
  + delta()      → tuple[int, int]   # (dx, dy) for a forward move

Command (Protocol / callable)
  TurnLeft    → rover.heading = rover.heading.turn_left()
  TurnRight   → rover.heading = rover.heading.turn_right()
  MoveForward → new = rover.pos + rover.heading.delta()
                if plateau.is_within(new): rover.pos = new

---

Package Structure

mars_rover/
├── __main__.py                  # CLI entry point
├── adapters/
│   ├── input_parser.py          # InputParser
│   └── output_formatter.py      # OutputFormatter
├── application/
│   └── mission_controller.py    # MissionController
└── domain/
    ├── plateau.py               # Plateau
    ├── rover.py                 # Rover
    ├── heading.py               # Heading enum
    └── commands.py              # TurnLeft, TurnRight, MoveForward