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//! Conditional publishing for declarative message publishing
//!
//! This module provides a fluent API for conditional and throttled publishing.
//!
//! # Examples
//!
//! ## Conditional Publishing
//!
//! ```rust
//! use mecha10_core::prelude::*;
//! use mecha10_core::publish::ContextPublishExt;
//! use mecha10_core::messages::Detection;
//! use mecha10_core::topics::perception;
//!
//! # async fn example(ctx: &Context, detections: Vec<Detection>) -> Result<()> {
//! // Only publish when detections are non-empty
//! ctx.publish_with(perception::DETECTIONS, &detections)
//! .when(|d| !d.is_empty())
//! .await?;
//! # Ok(())
//! # }
//! ```
//!
//! ## Throttled Publishing
//!
//! ```rust
//! use mecha10_core::prelude::*;
//! use mecha10_core::publish::ContextPublishExt;
//! use mecha10_core::messages::NodeStatus;
//! use mecha10_core::topics::system;
//!
//! # async fn example(ctx: &Context, status: NodeStatus) -> Result<()> {
//! // Publish at most once per second
//! ctx.publish_with(system::NODE_STATUS, &status)
//! .throttle(Duration::from_secs(1))
//! .await?;
//! # Ok(())
//! # }
//! ```
use crate::context::Context;
use crate::error::Result;
use crate::messages::Message;
use crate::topics::Topic;
use serde::Serialize;
use std::collections::HashMap;
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::Mutex;
static THROTTLE_STATE: once_cell::sync::Lazy<Arc<Mutex<HashMap<String, Instant>>>> =
once_cell::sync::Lazy::new(|| Arc::new(Mutex::new(HashMap::new())));
pub struct PublishBuilder<'a, 'b, T: Message + Serialize> {
ctx: &'a Context,
topic: Topic<T>,
message: &'b T,
#[allow(clippy::type_complexity)]
condition: Option<Box<dyn Fn(&T) -> bool + Send + Sync>>,
throttle_duration: Option<Duration>,
}
impl<'a, 'b, T: Message + Serialize> PublishBuilder<'a, 'b, T> {
/// Create a new publish builder
pub fn new(ctx: &'a Context, topic: Topic<T>, message: &'b T) -> Self {
Self {
ctx,
topic,
message,
condition: None,
throttle_duration: None,
}
}
crate::builder_setter!(
/// Only publish if condition is true
///
/// If the predicate returns `false`, the message will not be published.
///
/// # Example
///
/// ```rust
/// # use mecha10_core::prelude::*;
/// # use mecha10_core::publish::ContextPublishExt;
/// # use mecha10_core::messages::Detection;
/// # use mecha10_core::topics::perception;
/// # async fn example(ctx: &Context, detections: Vec<Detection>) -> Result<()> {
/// ctx.publish_with(perception::DETECTIONS, &detections)
/// .when(|d| !d.is_empty())
/// .await?;
/// # Ok(())
/// # }
/// ```
predicate, when, condition, Fn(&T) -> bool + Send + Sync + 'static
);
crate::builder_setter!(
/// Throttle publishing to a maximum rate
///
/// Messages will be rate-limited to at most one per `duration`.
/// If you try to publish more frequently, the message will be dropped.
///
/// # Example
///
/// ```rust
/// # use mecha10_core::prelude::*;
/// # use mecha10_core::publish::ContextPublishExt;
/// # use mecha10_core::messages::NodeStatus;
/// # use mecha10_core::topics::system;
/// # async fn example(ctx: &Context, status: NodeStatus) -> Result<()> {
/// // Max once per second
/// ctx.publish_with(system::NODE_STATUS, &status)
/// .throttle(Duration::from_secs(1))
/// .await?;
/// # Ok(())
/// # }
/// ```
into_some, throttle, throttle_duration, Duration
);
/// Execute the publish with all configured conditions
///
/// This method applies all the configured filters and throttling,
/// then publishes the message if all conditions are met.
pub async fn execute(self) -> Result<()> {
if let Some(ref condition) = self.condition {
if !condition(self.message) {
return Ok(());
}
}
if let Some(throttle_dur) = self.throttle_duration {
let topic_key = format!("{}-{}", self.ctx.node_id(), self.topic.path());
let mut throttle_state = THROTTLE_STATE.lock().await;
if let Some(last_time) = throttle_state.get(&topic_key) {
let elapsed = last_time.elapsed();
if elapsed < throttle_dur {
return Ok(());
}
}
throttle_state.insert(topic_key, Instant::now());
}
self.ctx.publish_to(self.topic, self.message).await
}
}
pub trait ContextPublishExt {
/// Start building a conditional publish operation
fn publish_with<'a, 'b, T>(&'a self, topic: Topic<T>, message: &'b T) -> PublishBuilder<'a, 'b, T>
where
T: Message + Serialize;
}
impl ContextPublishExt for Context {
fn publish_with<'a, 'b, T>(&'a self, topic: Topic<T>, message: &'b T) -> PublishBuilder<'a, 'b, T>
where
T: Message + Serialize,
{
PublishBuilder::new(self, topic, message)
}
}
impl<'a, 'b, T: Message + Serialize> std::future::IntoFuture for PublishBuilder<'a, 'b, T>
where
'b: 'a,
{
type Output = Result<()>;
type IntoFuture = std::pin::Pin<Box<dyn std::future::Future<Output = Result<()>> + Send + 'a>>;
fn into_future(self) -> Self::IntoFuture {
Box::pin(self.execute())
}
}