use derive_builder::Builder;
use std::fmt::Debug;
use std::time::Duration;
use std::time::Instant;
#[cfg_attr(test, mockall::automock(type State = State;))]
trait WaitCondition {
    type State: Copy;
    fn is_in_state(&self, state: Self::State) -> bool;
}
#[derive(Clone, Copy)]
struct Port(u16);
#[derive(Clone, Copy)]
enum State {
    Present,
    Absent,
}
impl WaitCondition for Port {
    type State = State;
    fn is_in_state(&self, state: Self::State) -> bool {
        match state {
            State::Present => !port_scanner::local_port_available(self.0),
            State::Absent => !self.is_in_state(State::Present),
        }
    }
}
#[derive(Debug, PartialEq, Eq)]
enum WaitError {
    Timeout,
}
#[cfg_attr(test, mockall::automock)]
trait Time {
    fn elapsed(&self) -> Duration;
}
impl Time for Instant {
    fn elapsed(&self) -> Duration {
        self.elapsed()
    }
}
#[cfg_attr(test, mockall::automock)]
trait Clock {
    fn sleep(&self, duration: Duration);
    fn now(&self) -> Box<dyn Time>;
}
struct SystemClock;
impl Clock for SystemClock {
    fn sleep(&self, duration: Duration) {
        std::thread::sleep(duration)
    }
    fn now(&self) -> Box<dyn Time> {
        Box::new(Instant::now())
    }
}
struct Environment {
    clock: Box<dyn Clock>,
}
trait Step {
    type Error: Debug;
    fn execute(self, environment: &Environment) -> Result<(), Self::Error>;
}
#[derive(Builder)]
#[builder(pattern = "immutable")]
struct Wait<Condition: WaitCondition> {
    condition: Condition,
    state: Condition::State,
    #[builder(default = "Duration::from_secs(60)")]
    timeout: Duration,
    #[builder(default = "None")]
    delay: Option<Duration>,
    #[builder(default = "Duration::from_millis(100)")]
    sleep: Duration,
}
impl<C: WaitCondition> Step for Wait<C> {
    type Error = WaitError;
    fn execute(self, environment: &Environment) -> Result<(), Self::Error> {
        if let Some(delay) = self.delay {
            environment.clock.sleep(delay);
        }
        let start_time = environment.clock.now();
        while start_time.elapsed() <= self.timeout {
            if self.condition.is_in_state(self.state) {
                return Ok(());
            }
            environment.clock.sleep(self.sleep);
        }
        eprintln!("Timed out");
        Err(WaitError::Timeout)
    }
}
fn main() {
    let env = Environment {
        clock: Box::new(SystemClock),
    };
    let wait_builder = WaitBuilder::default();
    let wait_builder = wait_builder
        .condition(Port(8181))
        .timeout(Duration::from_secs(3));
    let wait = wait_builder.state(State::Present).build().unwrap();
    eprintln!("Waiting for port 8181 to be listening");
    wait.execute(&env).unwrap();
    eprintln!("Port 8181 is listening");
    eprintln!("Waiting for port 8181 to not be listening");
    let wait = wait_builder.state(State::Absent).build().unwrap();
    eprintln!("Success");
    wait.execute(&env).unwrap();
}
#[cfg(test)]
mod tests {
    use super::*;
    fn waiter(condition: MockWaitCondition) -> Wait<MockWaitCondition> {
        WaitBuilder::default()
            .condition(condition)
            .state(State::Present)
            .timeout(Duration::from_secs(10))
            .build()
            .unwrap()
    }
    fn constant_condition(value: bool) -> MockWaitCondition {
        let mut condition = MockWaitCondition::default();
        condition.expect_is_in_state().return_const(value);
        condition
    }
    fn one_second_poller() -> Box<dyn Time> {
        let mut times = (1..).map(Duration::from_secs);
        let mut time = MockTime::default();
        time.expect_elapsed()
            .returning(move || times.next().unwrap());
        Box::new(time)
    }
    fn polling_clock() -> MockClock {
        let mut clock = MockClock::default();
        clock.expect_now().return_once(|| one_second_poller());
        clock
    }
    #[test]
    fn wait_does_not_sleep_if_condition_is_initially_satisfied() {
        let wait = waiter(constant_condition(true));
        let clock = polling_clock();
        let result = wait.execute(&Environment {
            clock: Box::new(clock),
        });
        assert!(result.is_ok());
    }
    #[test]
    fn wait_times_out_if_condition_is_never_satisfied() {
        let wait = waiter(constant_condition(false));
        let mut clock = polling_clock();
        clock.expect_sleep().return_const(());
        let result = wait.execute(&Environment {
            clock: Box::new(clock),
        });
        assert_eq!(result, Err(WaitError::Timeout))
    }
    #[test]
    fn wait_succeeds_after_condition_becomes_true() {
        let mut condition_values = [false, true].iter();
        let mut condition = MockWaitCondition::default();
        condition
            .expect_is_in_state()
            .returning(move |_| *condition_values.next().unwrap())
            .times(2);
        let wait = waiter(condition);
        let mut clock = polling_clock();
        clock.expect_sleep().return_const(());
        let result = wait.execute(&Environment {
            clock: Box::new(clock),
        });
        assert!(result.is_ok());
    }
}

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