use std::time::SystemTime;

use futures::{future::BoxFuture, Future, FutureExt};

use opentelemetry::{KeyValue, metrics::*};

pub trait RecordDuration<'a>: 'a {
	type Output;

	fn record_duration(self, r: &'a ValueRecorder<f64>, attributes: &'a [KeyValue]) -> BoxFuture<'a, Self::Output>;
	fn bound_record_duration(self, r: &'a BoundValueRecorder<f64>) -> BoxFuture<'a, Self::Output>;
}

impl<'a, T, O> RecordDuration<'a> for T
where T: Future<Output=O> + Send + 'a {
	type Output = O;

	fn record_duration(self, r: &'a ValueRecorder<f64>, attributes: &'a [KeyValue]) -> BoxFuture<'a, Self::Output> {
		async move {
			let request_start = SystemTime::now();
			let res = self.await;
			r.record(request_start.elapsed().map_or(0.0, |d| d.as_secs_f64()), attributes);
			res
		}.boxed()
	}

	fn bound_record_duration(self, r: &'a BoundValueRecorder<f64>) -> BoxFuture<'a, Self::Output> {
		async move {
			let request_start = SystemTime::now();
			let res = self.await;
			r.record(request_start.elapsed().map_or(0.0, |d| d.as_secs_f64()));
			res
		}.boxed()
	}
}