Pipeline Core

中文文档

Pipeline Core is a lightweight, type-safe library for building linear and concurrent processing pipelines in Rust. It draws inspiration from the API style of the Bevy framework, using Res and ResMut to access shared resources, but with a simpler implementation.

Key Features

Linear Composition: Chain async functions seamlessly to build processing workflows.
Dependency Injection: Access shared resources (Res, ResMut) or inputs (Input) directly in your function signatures.
Type Safety: Compile-time checks ensure pipeline stages connect correctly.
State Management: Built-in Shared container for managing global or scoped application state.

Getting Started

Cargo dependency

pipe-it = "0.2"

1. Basic Linear Pipeline

You can chain handlers (functions) together using .pipe() and .connect().

use pipe_it::{Context, Input, ext::HandlerExt};

// Step 1: Takes an integer, returns an integer
async fn double(num: Input<i32>) -> i32 {
    *num * 2
}

// Step 2: Takes an integer, returns a string
async fn to_string(num: Input<i32>) -> String {
    format!("Value is: {}", *num)
}

#[tokio::main]
async fn main() {
    // Define the pipeline: double -> to_string
    // The output of 'double' (i32) becomes the input context for 'to_string'
    let pipeline = double.pipe().connect(to_string);

    // execute
    let ctx = Context::empty(10); // Initial input: 10
    let result = pipeline.apply(ctx).await;

    println!("{}", result); // Output: "Value is: 20"
}

2. Using Shared Resources & Mutation

You can inject shared state into any handler using Res (read-only) and ResMut (mutable).

use pipe_it::{Context, Shared, Input, ResMut, ext::HandlerExt};

#[derive(Default)]
struct AccessLog {
    count: usize,
}

// This handler updates the shared log AND processes the input
async fn log_and_square(input: Input<i32>, mut log: ResMut<AccessLog>) -> i32 {
    log.count += 1;
    println!("Log count: {}", log.count);
    *input * *input
}

#[tokio::main]
async fn main() {
    // 1. Setup shared state
    let shared = Shared::new()
        .insert(AccessLog::default());

    // 2. Create context with input and shared state
    let ctx = Context::new(5, shared);

    // 3. Run the pipeline
    let result = log_and_square.pipe().apply(ctx).await;

    assert_eq!(result, 25);
}

3. Using Tags for Composition

You can decouple handler definition from usage by assigning string tags to functions using the #[node] macro, and referencing them with the tag!() macro.

use pipe_it::{Context, Input, ext::HandlerExt, node, tag};

// 1. Define a handler with a unique tag
#[node("greet")]
async fn greet(name: Input<String>) -> String {
    format!("Hello, {}!", *name)
}

#[tokio::main]
async fn main() {
    // 2. Create a pipeline using the tag instead of the function name
    let pipeline = tag!("greet").pipe();

    let ctx = Context::empty("World".to_string());
    let result = pipeline.apply(ctx).await;

    println!("{}", result); // Output: "Hello, World!"
}

4. Branching & Fallback (Tuple Pipeline)

You can use tuples (A, B, ...) to compose multiple pipelines that return PResult. The framework attempts execution sequentially until one succeeds (returns Ok).

use pipe_it::{Context, Input, PResult, PipelineError, ext::HandlerExt};

// Try to parse string to int
async fn parse_int(s: Input<String>) -> PResult<i32> {
    // Hint: Use try_unwrap() to attempt acquiring ownership of String to avoid cloning
    s.parse().map_err(|_| PipelineError::Fatal { msg: "Not an int".into() })
}

// Fallback: return default value 0
async fn default_zero(_: Input<String>) -> PResult<i32> {
    Ok(0)
}

#[tokio::main]
async fn main() {
    // Create branching pipeline: Try parse_int first, if it fails, run default_zero
    let pipeline = (parse_int.pipe(), default_zero.pipe());

    let ctx = Context::empty("not number".to_string());
    let result = pipeline.apply(ctx).await;
    
    assert_eq!(result.unwrap(), 0);
}

5. Reusable Pipelines (Middle Pipeline)

You can define functions that return a constructed Pipeline. This is useful for encapsulating complex logic or creating reusable middleware.

use pipe_it::{Context, Input, Pipeline, ext::HandlerExt};

async fn step_a(n: Input<i32>) -> i32 { *n + 1 }
async fn step_b(n: Input<i32>) -> String { n.to_string() }

// Encapsulate a chain of handlers into a single function
fn common_logic() -> impl Pipeline<i32, String> {
    step_a.pipe().connect(step_b)
}

#[tokio::main]
async fn main() {
    let pipe = common_logic();
    let result = pipe.apply(Context::empty(10)).await;
    println!("{}", result); // "11"
}

API Overview

Core Concepts

Handler: Any async function that takes arguments implementing FromContext.
Context<I>: Holds the current input I and Shared resources.
Input<I>: A wrapper to extract the current input from the context.
Res<T> / ResMut<T>: Wrappers to extract shared resources from the context.

Extension Methods (`HandlerExt`)

.pipe(): Converts a handler into a Pipeline.
.connect(next_handler): Chains two pipelines linearly.
.map(inner_pipeline): (If available) Processes Vec<I> inputs concurrently.

pipe-it 0.2.2