This was actually an excuse to design a completely event-driven terminal program in Swift. It's inspired by the Elm Architecture.

How it works:

• Sets the terminal to raw mode, to enable processing input character-by-character instead of line-by-line.

• Configures a Grand Central Dispatch (GCD) DispatchReadSource to read from standard input one character at a time.

• Configures a number of GCD DispatchSignalSources to process signals as events.

• With the event handlers in place, models the application as an App struct that receives an Event, optionally updates its state, and dispatches an array of Action.

• No side effects are implemented in App, but are instead implemented in top-level functions handle() and dispatch(), which convert Actions into side effects.