wingfoil 3.0.1

graph based stream processing framework
Documentation 
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use derive_new::new;

use crate::types::*;
use std::rc::Rc;

/// Emit's its source, if and only if, it's trigger ticks.
/// Used by [sample](crate::nodes::StreamOperators::sample).
#[derive(new)]
pub struct SampleStream<T: Element> {
    upstream: Rc<dyn Stream<T>>,
    trigger: Rc<dyn Node>,
    #[new(default)]
    value: T,
}

impl<T: Element> MutableNode for SampleStream<T> {
    fn cycle(&mut self, _state: &mut GraphState) -> anyhow::Result<bool> {
        self.value = self.upstream.peek_value();
        Ok(true)
    }

    fn upstreams(&self) -> UpStreams {
        // only ticks on trigger
        let active = vec![self.trigger.clone()];
        let passive = vec![self.upstream.clone().as_node()];
        UpStreams::new(active, passive)
    }
}

impl<T: Element> StreamPeekRef<T> for SampleStream<T> {
    fn peek_ref(&self) -> &T {
        &self.value
    }
}

#[cfg(test)]
mod tests {

    use super::*;
    use crate::graph::*;
    use crate::nodes::*;

    #[test]
    fn sample_works() {
        //env_logger::init();
        let c = ConstantStream::new(7).into_stream();
        let ticker1 = ticker(Duration::from_millis(100));
        let ticker2 = ticker(Duration::from_millis(200));
        let node = c
            .sample(ticker1)
            .logged("a", log::Level::Info)
            .sample(ticker2)
            .logged("b", log::Level::Info);
        Graph::new(
            vec![node.as_node()],
            RunMode::HistoricalFrom(NanoTime::ZERO),
            RunFor::Duration(Duration::from_millis(1000)),
        )
        .print()
        .run()
        .unwrap();
    }
}