enum MyState: StateType {
    case state0, state1, state2
}

// setup state machine
let machine = StateMachine<MyState, NoEvent>(state: .state0) { machine in
    
    machine.addRoute(.state0 => .state1)
    machine.addRoute(.any => .state2) { context in print("Any => 2, msg=\(context.userInfo)") }
    machine.addRoute(.state2 => .any) { context in print("2 => Any, msg=\(context.userInfo)") }
    
    // add handler (`context = (event, fromState, toState, userInfo)`)
    machine.addHandler(.state0 => .state1) { context in
        print("0 => 1")
    }
    
    // add errorHandler
    machine.addErrorHandler { event, fromState, toState, userInfo in
        print("[ERROR] \(fromState) => \(toState)")
    }
}

// initial
XCTAssertEqual(machine.state, MyState.state0)

// tryState 0 => 1 => 2 => 1 => 0

machine <- .state1
XCTAssertEqual(machine.state, MyState.state1)

machine <- (.state2, "Hello")
XCTAssertEqual(machine.state, MyState.state2)

machine <- (.state1, "Bye")
XCTAssertEqual(machine.state, MyState.state1)

machine <- .state0  // fail: no 1 => 0
XCTAssertEqual(machine.state, MyState.state1)

0 => 1
Any => 2, msg=Optional("Hello")
2 => Any, msg=Optional("Bye")
[ERROR] state1 => state0

enum MyEvent: EventType {
    case event0, event1
}

let machine = StateMachine<MyState, MyEvent>(state: .state0) { machine in
    
    // add 0 => 1 => 2
    machine.addRoutes(event: .event0, transitions: [
        .state0 => .state1,
        .state1 => .state2,
    ])
    
    // add event handler
    machine.addHandler(event: .event0) { context in
        print(".event0 triggered!")
    }
}

// initial
XCTAssertEqual(machine.state, MyState.state0)

// tryEvent
machine <-! .event0
XCTAssertEqual(machine.state, MyState.state1)

// tryEvent
machine <-! .event0
XCTAssertEqual(machine.state, MyState.state2)

// tryEvent (fails)
machine <-! .event0
XCTAssertEqual(machine.state, MyState.state2, "event0 doesn't have 2 => Any")

enum StrState: StateType {
    case str(String) ...
}
enum StrEvent: EventType {
    case str(String) ...
}

let machine = Machine<StrState, StrEvent>(state: .str("initial")) { machine in
    
    machine.addRouteMapping { event, fromState, userInfo -> StrState? in
        // no route for no-event
        guard let event = event else { return nil }
        
        switch (event, fromState) {
            case (.str("gogogo"), .str("initial")):
                return .str("Phase 1")
            case (.str("gogogo"), .str("Phase 1")):
                return .str("Phase 2")
            case (.str("finish"), .str("Phase 2")):
                return .str("end")
            default:
                return nil
        }
    }
    
}

// initial
XCTAssertEqual(machine.state, StrState.str("initial"))

// tryEvent (fails)
machine <-! .str("go?")
XCTAssertEqual(machine.state, StrState.str("initial"), "No change.")

// tryEvent
machine <-! .str("gogogo")
XCTAssertEqual(machine.state, StrState.str("Phase 1"))

// tryEvent (fails)
machine <-! .str("finish")
XCTAssertEqual(machine.state, StrState.str("Phase 1"), "No change.")

// tryEvent
machine <-! .str("gogogo")
XCTAssertEqual(machine.state, StrState.str("Phase 2"))

// tryEvent (fails)
machine <-! .str("gogogo")
XCTAssertEqual(machine.state, StrState.str("Phase 2"), "No change.")

// tryEvent
machine <-! .str("finish")
XCTAssertEqual(machine.state, StrState.str("end"))