gardal 0.0.1-alpha.3

A WIP performance-focused token-bucket rate limiting and throttling library
Documentation 
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//! Async utilities for rate limiting with futures and streams.
//!
//! This module provides async-friendly wrappers and utilities for rate limiting
//! in async contexts. It requires the "async" feature to be enabled.
//!
//! # Features
//!
//! - [`RateLimitedStream`] - Rate limit any stream
//! - [`RateLimitedStreamExt`] - Extension trait for easy stream rate limiting
//!
//! # Examples
//!
//! ```rust
//! # #[cfg(feature = "async")]
//! # {
//! use gardal::{TokenBucket, RateLimit};
//! use gardal::futures::RateLimitedStreamExt;
//! use futures::stream;
//! use std::num::NonZeroU32;
//!
//! # async fn example() {
//! let limit = RateLimit::per_second(NonZeroU32::new(10).unwrap());
//! let bucket = TokenBucket::new(limit);
//!
//! let stream = stream::iter(0..100)
//!     .rate_limit(bucket);
//! # }
//! # }
//! ```

mod stream;
mod timer;

pub use stream::{RateLimitedStream, WeightedStream};

use futures::Stream;
use std::num::NonZeroU32;

use crate::storage::TimeStorage;
use crate::{Clock, TokenBucket};

/// Extension trait for adding rate limiting to any stream.
///
/// This trait provides a convenient way to apply rate limiting to existing streams
/// without having to manually wrap them.
///
/// # Examples
///
/// ```rust
/// # #[cfg(feature = "async")]
/// # {
/// use gardal::{TokenBucket, RateLimit};
/// use gardal::futures::RateLimitedStreamExt;
/// use futures::stream;
/// use std::num::NonZeroU32;
///
/// # async fn example() {
/// let limit = RateLimit::per_second(NonZeroU32::new(5).unwrap());
/// let bucket = TokenBucket::new(limit);
///
/// let rate_limited = stream::iter(1..=10)
///     .rate_limit(bucket);
/// # }
/// # }
/// ```
pub trait RateLimitedStreamExt<S, ST, C>
where
    S: Stream,
    ST: TimeStorage,
    C: Clock,
{
    /// Applies rate limiting to this stream using the provided token bucket.
    ///
    /// # Arguments
    ///
    /// * `bucket` - The token bucket to use for rate limiting
    ///
    /// # Returns
    ///
    /// A [`RateLimitedStream`] that wraps this stream with rate limiting
    fn rate_limit(self, bucket: TokenBucket<ST, C>) -> RateLimitedStream<S, ST, C>;

    /// Applies weighted rate limiting to this stream using the provided token bucket.
    ///
    /// Each item in the stream can consume a different number of tokens based on the
    /// weight function. This allows for more sophisticated rate limiting where different
    /// items have different costs.
    ///
    /// # Arguments
    ///
    /// * `bucket` - The token bucket to use for rate limiting
    /// * `weight_fn` - A function that determines how many tokens each item consumes
    ///
    /// # Returns
    ///
    /// A [`WeightedStream`] that wraps this stream with weighted rate limiting
    ///
    /// # Examples
    ///
    /// ```rust
    /// # #[cfg(feature = "async")]
    /// # {
    /// use gardal::{TokenBucket, RateLimit};
    /// use gardal::futures::RateLimitedStreamExt;
    /// use futures::stream;
    /// use std::num::NonZeroU32;
    ///
    /// # async fn example() {
    /// let limit = RateLimit::per_second(NonZeroU32::new(10).unwrap());
    /// let bucket = TokenBucket::new(limit);
    ///
    /// let rate_limited = stream::iter(vec!["small", "large", "medium"])
    ///     .rate_limit_weighted(bucket, |item: &&str| {
    ///         NonZeroU32::new(item.len() as u32).unwrap_or(NonZeroU32::new(1).unwrap())
    ///     });
    /// # }
    /// # }
    /// ```
    fn rate_limit_weighted<F>(
        self,
        bucket: TokenBucket<ST, C>,
        weight_fn: F,
    ) -> WeightedStream<S, ST, C, F>
    where
        F: Fn(&S::Item) -> NonZeroU32;
}

impl<S, ST, C> RateLimitedStreamExt<S, ST, C> for S
where
    S: Stream,
    ST: TimeStorage,
    C: Clock,
{
    fn rate_limit(self, bucket: TokenBucket<ST, C>) -> RateLimitedStream<S, ST, C> {
        RateLimitedStream::new(self, bucket)
    }

    fn rate_limit_weighted<F>(
        self,
        bucket: TokenBucket<ST, C>,
        weight_fn: F,
    ) -> WeightedStream<S, ST, C, F>
    where
        F: Fn(&S::Item) -> NonZeroU32,
    {
        WeightedStream::new(self, bucket, weight_fn)
    }
}