Fluxion

A reactive stream processing library for Rust with temporal ordering guarantees, efficient async execution and friendly fluent API.

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Table of Contents

• Features
• Quick Start
• Operator Documentation
• Core Concepts
• Documentation
• Development

Features

• 🔄 Rx-Style Operators: Familiar reactive programming patterns (combine_latest, with_latest_from, ordered_merge, etc.)

• ⏱️ Temporal Ordering: Guaranteed ordering semantics with Sequenced<T> wrapper

• ⚡ Async Execution: Efficient async processing with subscribe_async and subscribe_latest_async

• 🛡️ Type-Safe Error Handling: Comprehensive error propagation with Result types

• 📚 Excellent Documentation: Detailed guides, examples, and API docs

• ✅ Well Tested: 1,500+ tests with comprehensive coverage

Quick Start

Add Fluxion to your Cargo.toml:

[dependencies]
fluxion-rx = "0.1.0"
fluxion-test-utils = "0.1.0"
tokio = { version = "1.48", features = ["full"] }
futures = "0.3"

Basic Usage

use fluxion_rx::prelude::*;
use fluxion_test_utils::Sequenced;
use futures::StreamExt;

#[tokio::main]
async fn main() {
    // Define enum to hold int and bool types
    #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
    enum Value {
        Int(i32),
        Bool(bool),
    }

    // Create int stream and bool trigger stream
    let (tx_int, rx_int) = tokio::sync::mpsc::unbounded_channel::<Sequenced<Value>>();
    let (tx_trigger, rx_trigger) = tokio::sync::mpsc::unbounded_channel::<Sequenced<Value>>();

    let int_stream = FluxionStream::from_unbounded_receiver(rx_int);
    let trigger_stream = FluxionStream::from_unbounded_receiver(rx_trigger);

    let mut pipeline = int_stream.take_latest_when(trigger_stream, |_| true);

    // Send int values - they will be buffered
    tx_int.send(Sequenced::with_sequence(Value::Int(10), 1)).unwrap();
    tx_int.send(Sequenced::with_sequence(Value::Int(20), 2)).unwrap();
    tx_int.send(Sequenced::with_sequence(Value::Int(30), 3)).unwrap();

    // Trigger with bool - should emit latest int value (30)
    tx_trigger.send(Sequenced::with_sequence(Value::Bool(true), 4)).unwrap();

    let result1 = pipeline.next().await.unwrap();
    assert!(matches!(result1.get(), Value::Int(30)));
    assert_eq!(result1.sequence(), 4);

    // Send more int values - these will trigger emissions
    tx_int.send(Sequenced::with_sequence(Value::Int(40), 5)).unwrap();

    let result2 = pipeline.next().await.unwrap();
    assert!(matches!(result2.get(), Value::Int(40)));
    assert_eq!(result2.sequence(), 5);

    tx_int.send(Sequenced::with_sequence(Value::Int(50), 6)).unwrap();

    let result3 = pipeline.next().await.unwrap();
    assert!(matches!(result3.get(), Value::Int(50)));
    assert_eq!(result3.sequence(), 6);
}

Chaining Multiple Operators

Fluxion operators can be chained to create complex processing pipelines. Here a complete example:

Example: combine_latest -> filter_ordered - Sampling on Trigger Events

use fluxion_rx::prelude::*;
use fluxion_test_utils::Sequenced;
use futures::StreamExt;

#[tokio::test]
async fn test_take_latest_when_int_bool() {
    // Define enum to hold both int and string types
    #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
    enum Value {
        Int(i32),
        Str(String),
    }

    // Create two input streams
    let (tx_int, rx_int) = tokio::sync::mpsc::unbounded_channel::<Sequenced<Value>>();
    let (tx_str, rx_str) = tokio::sync::mpsc::unbounded_channel::<Sequenced<Value>>();

    let int_stream = FluxionStream::from_unbounded_receiver(rx_int);
    let str_stream = FluxionStream::from_unbounded_receiver(rx_str);

    // Chain: combine_latest -> filter
    let mut pipeline = int_stream
        .combine_latest(vec![str_stream], |_| true)
        .filter_ordered(|combined| {
            // Keep only if first value (int) is > 50
            matches!(combined.get_state()[0], Value::Int(x) if x > 50)
        });

    // Send initial values
    tx_str.send(Sequenced::with_sequence(Value::Str("initial".into()), 1)).unwrap();
    tx_int.send(Sequenced::with_sequence(Value::Int(30), 2)).unwrap(); // Filtered out (30 <= 50)
    tx_int.send(Sequenced::with_sequence(Value::Int(60), 3)).unwrap(); // Passes filter (60 > 50)
    tx_str.send(Sequenced::with_sequence(Value::Str("updated".into()), 4)).unwrap(); // Passes filter (int still 60)
    tx_int.send(Sequenced::with_sequence(Value::Int(75), 5)).unwrap(); // Passes filter (75 > 50)

    // Results: seq 3 (Int 60), seq 4 (Int 60 + Str updated), seq 5 (Int 75)
    let result1 = pipeline.next().await.unwrap();
    let combined1 = result1.get().get_state();
    assert!(matches!(combined1[0], Value::Int(60)));
    assert!(matches!(combined1[1], Value::Str(ref s) if s == "initial"));

    let result2 = pipeline.next().await.unwrap();
    let combined2 = result2.get().get_state();
    assert!(matches!(combined2[0], Value::Int(60)));
    assert!(matches!(combined2[1], Value::Str(ref s) if s == "updated"));

    let result3 = pipeline.next().await.unwrap();
    let combined3 = result3.get().get_state();
    assert!(matches!(combined3[0], Value::Int(75)));
    assert!(matches!(combined3[1], Value::Str(ref s) if s == "updated"));
}

📚 Operator Documentation

• All Operators - Complete operator reference
• Operators Roadmap - Planned future operators

Core Concepts

Stream Operators

Combining Streams:

• combine_latest - Emit when any stream emits, with latest from all
• with_latest_from - Sample secondary streams on primary emission
• ordered_merge - Merge multiple streams preserving temporal order

Filtering & Gating:

• emit_when - Gate emissions based on a filter condition
• take_latest_when - Sample stream on trigger events
• take_while_with - Emit while condition holds

Transformation:

• combine_with_previous - Pair consecutive values
• map_ordered - Transform while preserving order
• filter_ordered - Filter while preserving order

Async Execution

Sequential Processing:

use fluxion_exec::SubscribeAsyncExt;

stream
    .subscribe_async(
        |item, _token| async move {
            process(item).await?;
            Ok::<(), MyError>(())
        },
        None,
        Some(|err| eprintln!("Error: {}", err))
    )
    .await?;

Latest-Value Processing (with auto-cancellation):

use fluxion_exec::SubscribeLatestAsyncExt;

stream
    .subscribe_latest_async(
        |item, token| async move {
            expensive_operation(item, token).await?;
            Ok::<(), MyError>(())
        },
        Some(|err| eprintln!("Error: {}", err)),
        None
    )
    .await?;

Documentation

📚 Guides

• Integration Guide - Learn the three patterns for integrating events (intrinsic, extrinsic, wrapper ordering)
• fluxion-stream - Stream operators and composition patterns
• fluxion-exec - Async execution and subscription utilities

💡 Complete Example

The stream-aggregation example demonstrates production-ready patterns:

• Real-world architecture: 3 producers, 1 aggregator, 1 consumer
• Ordered stream combining: Merges sensor readings, metrics, and system events
• Type-safe transformations: Uses UnboundedReceiverExt for elegant type erasure
• Graceful shutdown: Proper cleanup with CancellationToken
• Error handling: Demonstrates best practices throughout

Why this example matters:

• Shows how all the pieces fit together in a realistic application
• Demonstrates the into_fluxion_stream() pattern for combining heterogeneous streams
• Illustrates proper resource management and cancellation
• Serves as a template for building your own event processing systems

Run it with: cargo run --example stream-aggregation

🔧 API Documentation

Generate and browse full API documentation:

cargo doc --no-deps --open

Or for specific crates:

cargo doc --package fluxion-stream --open
cargo doc --package fluxion-exec --open

Development

Prerequisites

• Rust toolchain (version pinned in rust-toolchain.toml)
• Cargo

Building

# Run CI checks locally (PowerShell)
.\.ci\ci.ps1

Workspace Structure

• fluxion-rx - Main crate (re-exports from other crates)
• fluxion-stream - Stream operators and combinators
• fluxion-exec - Execution utilities and subscriptions
• fluxion-core - Core utilities and traits
• fluxion-error - Error types and handling
• fluxion-test-utils - Test helpers and fixtures
• fluxion-merge - Stream merging utilities
• fluxion-ordered-merge - Ordered merging implementation

Development Notes

• All clippy, formatting, and documentation warnings are treated as errors in CI
• Use .ci/coverage.ps1 to collect code coverage locally (requires cargo-llvm-cov)
• See ROADMAP.md for planned features and release schedule

Project Status

Current Version: 0.1.1

• ✅ Published to crates.io
• ✅ Core functionality complete
• ✅ Comprehensive test coverage
• ✅ Phase 1 error handling implemented
• 🚧 Phase 2 error propagation (planned for 1.0.0)
• 📝 Documentation complete for current features

See ROADMAP.md for details on the path to 1.0.0.

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

Before submitting a PR:

1. Run tests: cargo test --workspace
2. Run clippy: cargo clippy --workspace -- -D warnings
3. Format code: cargo fmt --all
4. Update documentation if needed

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

Acknowledgments

Inspired by ReactiveX and other reactive programming libraries, with a focus on Rust's safety and performance characteristics.

Security

All commits and releases are GPG signed.

Key ID: 5729DA194B0929542BF79074C2A11DED229A1E51 Fingerprint: 5729 DA19 4B09 2954 2BF7 9074 C2A1 1DED 229A 1E51

Author

Name: Umberto Gotti Email: umberto.gotti@umbertogotti.dev Twitter: https://x.com/GottiUmberto