streamweave 0.10.1

Composable, async, stream-first computation in pure Rust
Documentation 
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use std::any::Any;
use std::sync::Arc;
use streamweave::graph;
use streamweave::graph::Graph;
use streamweave::nodes::stream::DropNode;
use tokio::sync::mpsc;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
  // Create channels for external I/O
  let (config_tx, config_rx) = mpsc::channel(1);
  let (input_tx, input_rx) = mpsc::channel(10);
  let (output_tx, mut output_rx) = mpsc::channel::<Arc<dyn Any + Send + Sync>>(10);
  let (error_tx, mut error_rx) = mpsc::channel::<Arc<dyn Any + Send + Sync>>(10);

  // Build the graph using the graph! macro
  let mut graph: Graph = graph! {
    drop: DropNode::new("drop".to_string()),
    graph.configuration => drop.configuration,
    graph.input => drop.in,
    drop.out => graph.output,
    drop.error => graph.error
  };

  // Connect external channels at runtime
  graph.connect_input_channel("configuration", config_rx)?;
  graph.connect_input_channel("input", input_rx)?;
  graph.connect_output_channel("output", output_tx)?;
  graph.connect_output_channel("error", error_tx)?;

  println!("✓ Graph built with DropNode using graph! macro");

  // Send configuration (optional for DropNode)
  let _ = config_tx
    .send(Arc::new(()) as Arc<dyn Any + Send + Sync>)
    .await;

  // Send test data: several items that should be dropped
  println!("📥 Sending values to drop: 1, 2, 3, 4, 5");
  let test_values = vec![1i32, 2i32, 3i32, 4i32, 5i32];
  for value in test_values {
    input_tx
      .send(Arc::new(value) as Arc<dyn Any + Send + Sync>)
      .await
      .unwrap();
    tokio::time::sleep(tokio::time::Duration::from_millis(50)).await;
  }

  println!("✓ Configuration and test data sent to input channels");

  // Execute the graph
  println!("Executing graph with DropNode...");
  let start = std::time::Instant::now();
  graph
    .execute()
    .await
    .map_err(|e| format!("Graph execution failed: {:?}", e))?;
  println!("✓ Graph execution completed in {:?}", start.elapsed());

  // Drop the transmitters to close the input channels (signals EOF to streams)
  drop(config_tx);
  drop(input_tx);

  // Read results from the output channels
  println!("Reading results from output channels...");
  let mut output_count = 0;
  let mut error_count = 0;

  loop {
    let output_result =
      tokio::time::timeout(tokio::time::Duration::from_millis(100), output_rx.recv()).await;
    let error_result =
      tokio::time::timeout(tokio::time::Duration::from_millis(100), error_rx.recv()).await;

    let mut has_data = false;

    if let Ok(Some(_item)) = output_result {
      // DropNode should not output any items
      output_count += 1;
      has_data = true;
      println!("  Unexpected output item received (this should not happen)");
    }

    if let Ok(Some(item)) = error_result
      && let Ok(error_msg) = item.downcast::<String>()
    {
      let error = (**error_msg).to_string();
      println!("  Error: {}", error);
      error_count += 1;
      has_data = true;
    }

    if !has_data {
      break;
    }
  }

  println!(
    "✓ Received {} items via output channel (should be 0)",
    output_count
  );
  println!("✓ Received {} errors via error channel", error_count);
  println!("✓ Total completed in {:?}", start.elapsed());

  // Verify behavior: should receive no output items and no errors
  if output_count == 0 && error_count == 0 {
    println!("✓ DropNode correctly dropped all input items");
  } else {
    println!(
      "⚠ DropNode behavior may be unexpected (outputs: {}, errors: {}, expected outputs: 0, errors: 0)",
      output_count, error_count
    );
  }

  Ok(())
}