# Elevator Project - TTK4145: Real time programming

## General description
This project is an implementation of an elevator system running `n` elevators across `m` floors, using Elixir. The implementation uses message passing, through use of the following OTP behaviours and modules:
- [GenServer](https://hexdocs.pm/elixir/GenServer.html)
- [GenStateMachine](https://hexdocs.pm/gen_state_machine/GenStateMachine.html)
- [Task](https://hexdocs.pm/elixir/Task.html)
- [Agent](https://hexdocs.pm/elixir/Agent.html)
- [Supervisor](https://hexdocs.pm/elixir/Supervisor.html)
- [Process](https://hexdocs.pm/elixir/Process.html)
- [Node](https://hexdocs.pm/elixir/Node.html)

## Modules
The system is divided into the following modules:
- `ElevatorOperator` for running the elevator finite state machine.
    - `ElevatorOperator.DoorTimer` for timing closing of the elevator door.
- `Network` for establishing and maintaining connection to the node cluster.
    - `Network.Listen` for receiving broadcasts with names of other nodes.
    - `Network.Broadcast` for broadcasting own node name.
    - `Network.ConnectionCheck` for checking if the node is connected to the cluster, and requesting backup whenever it becomes connected.
- `Orders` for keeping track of all orders in the cluster.
- `OrderAssigner` for deciding which elevator is best fit to handle an incoming order.
- `OrderDistributor` for distributing new assignments and comleted handling of orders to the rest of the cluster.
- `Watchdog` for reinjecting orders if they are not handled within a set amount of time.
- `Driver` for communicating with the elevator hardware.
- `InputPoller` for polling the various hardware sensors.
    - `ObstructionPoller` for polling the obstruction switch sensor.
    - `FloorPoller` for polling the floor sensor.
    - `OrderButtonPoller` for polling an order button.

Additionally, different modules are supervised by different Supervisors. These Supervisors are responsible for restarting modules if the terminate due to some error. The modules are documented at https://hexdocs.pm/elevator_project/0.1.0. 

## Running the system
The system can be ran through the command `mix run --no-halt`. The application requires the installation of the delivered ElevatorServer.