swiftide_indexing/

pipeline.rs

use anyhow::Result;
use futures_util::{StreamExt, TryFutureExt, TryStreamExt};
use swiftide_core::{
    BatchableTransformer, ChunkerTransformer, Loader, NodeCache, Persist, SimplePrompt,
    Transformer, WithBatchIndexingDefaults, WithIndexingDefaults, indexing::IndexingDefaults,
};
use tokio::{sync::mpsc, task};
use tracing::Instrument;

use std::{sync::Arc, time::Duration};

use swiftide_core::indexing::{EmbedMode, IndexingStream, Node};

macro_rules! trace_span {
    ($op:literal, $step:expr) => {
        tracing::trace_span!($op, "otel.name" = format!("{}.{}", $op, $step.name()),)
    };

    ($op:literal) => {
        tracing::trace_span!($op, "otel.name" = format!("{}", $op),)
    };
}

macro_rules! node_trace_log {
    ($step:expr, $node:expr, $msg:literal) => {
        tracing::trace!(
            node = ?$node,
            node_id = ?$node.id(),
            step = $step.name(),
            $msg
        )
    };
}

macro_rules! batch_node_trace_log {
    ($step:expr, $nodes:expr, $msg:literal) => {
        tracing::trace!(batch_size = $nodes.len(), nodes = ?$nodes, step = $step.name(), $msg)
    };
}

/// The default batch size for batch processing.
const DEFAULT_BATCH_SIZE: usize = 256;

/// A pipeline for indexing files, adding metadata, chunking, transforming, embedding, and then
/// storing them.
///
/// The `Pipeline` struct orchestrates the entire file indexing process. It is designed to be
/// flexible and performant, allowing for various stages of data transformation and storage to be
/// configured and executed asynchronously.
///
/// # Fields
///
/// * `stream` - The stream of `Node` items to be processed.
/// * `storage` - Optional storage backend where the processed nodes will be stored.
/// * `concurrency` - The level of concurrency for processing nodes.
pub struct Pipeline {
    stream: IndexingStream,
    storage: Vec<Arc<dyn Persist>>,
    concurrency: usize,
    indexing_defaults: IndexingDefaults,
    batch_size: usize,
}

impl Default for Pipeline {
    /// Creates a default `Pipeline` with an empty stream, no storage, and a concurrency level equal
    /// to the number of CPUs.
    fn default() -> Self {
        Self {
            stream: IndexingStream::empty(),
            storage: Vec::default(),
            concurrency: num_cpus::get(),
            indexing_defaults: IndexingDefaults::default(),
            batch_size: DEFAULT_BATCH_SIZE,
        }
    }
}

impl Pipeline {
    /// Creates a `Pipeline` from a given loader.
    ///
    /// # Arguments
    ///
    /// * `loader` - A loader that implements the `Loader` trait.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` initialized with the provided loader.
    pub fn from_loader(loader: impl Loader + 'static) -> Self {
        let stream = loader.into_stream();
        Self {
            stream,
            ..Default::default()
        }
    }

    /// Sets the default LLM client to be used for LLM prompts for all transformers in the
    /// pipeline.
    #[must_use]
    pub fn with_default_llm_client(mut self, client: impl SimplePrompt + 'static) -> Self {
        self.indexing_defaults = IndexingDefaults::from_simple_prompt(Box::new(client));
        self
    }

    /// Creates a `Pipeline` from a given stream.
    ///
    /// # Arguments
    ///
    /// * `stream` - An `IndexingStream` containing the nodes to be processed.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` initialized with the provided stream.
    pub fn from_stream(stream: impl Into<IndexingStream>) -> Self {
        Self {
            stream: stream.into(),
            ..Default::default()
        }
    }

    /// Sets the concurrency level for the pipeline. By default the concurrency is set to the
    /// number of cpus.
    ///
    /// # Arguments
    ///
    /// * `concurrency` - The desired level of concurrency.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the updated concurrency level.
    #[must_use]
    pub fn with_concurrency(mut self, concurrency: usize) -> Self {
        self.concurrency = concurrency;
        self
    }

    /// Sets the embed mode for the pipeline. The embed mode controls what (combination) fields of a
    /// [`Node`] be embedded with a vector when transforming with [`crate::transformers::Embed`]
    ///
    /// See also [`swiftide_core::indexing::EmbedMode`].
    ///
    /// # Arguments
    ///
    /// * `embed_mode` - The desired embed mode.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the updated embed mode.
    #[must_use]
    pub fn with_embed_mode(mut self, embed_mode: EmbedMode) -> Self {
        self.stream = self
            .stream
            .map_ok(move |mut node| {
                node.embed_mode = embed_mode;
                node
            })
            .boxed()
            .into();
        self
    }

    /// Filters out cached nodes using the provided cache.
    ///
    /// # Arguments
    ///
    /// * `cache` - A cache that implements the `NodeCache` trait.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the updated stream that filters out cached nodes.
    #[must_use]
    pub fn filter_cached(mut self, cache: impl NodeCache + 'static) -> Self {
        let cache = Arc::new(cache);
        self.stream = self
            .stream
            .try_filter_map(move |node| {
                let cache = Arc::clone(&cache);
                let span = trace_span!("filter_cached", cache);

                async move {
                    if cache.get(&node).await {
                        node_trace_log!(cache, node, "node in cache, skipping");
                        Ok(None)
                    } else {
                        node_trace_log!(cache, node, "node not in cache, processing");
                        cache.set(&node).await;
                        Ok(Some(node))
                    }
                }
                .instrument(span.or_current())
            })
            .boxed()
            .into();
        self
    }

    /// Adds a transformer to the pipeline.
    ///
    /// Closures can also be provided as transformers.
    ///
    /// # Arguments
    ///
    /// * `transformer` - A transformer that implements the `Transformer` trait.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the updated stream that applies the transformer to each node.
    #[must_use]
    pub fn then(
        mut self,
        mut transformer: impl Transformer + WithIndexingDefaults + 'static,
    ) -> Self {
        let concurrency = transformer.concurrency().unwrap_or(self.concurrency);

        transformer.with_indexing_defaults(self.indexing_defaults.clone());

        let transformer = Arc::new(transformer);
        self.stream = self
            .stream
            .map_ok(move |node| {
                let transformer = transformer.clone();
                let span = trace_span!("then", transformer);

                task::spawn(
                    async move {
                        node_trace_log!(transformer, node, "Transforming node");
                        transformer.transform_node(node).await
                    }
                    .instrument(span.or_current()),
                )
                .err_into::<anyhow::Error>()
            })
            .try_buffer_unordered(concurrency)
            .map(|x| x.and_then(|x| x))
            .boxed()
            .into();

        self
    }

    /// Adds a batch transformer to the pipeline.
    ///
    /// If the transformer has a batch size set, the batch size from the transformer is used,
    /// otherwise the pipeline default batch size ([`DEFAULT_BATCH_SIZE`]).
    ///
    /// # Arguments
    ///
    /// * `transformer` - A transformer that implements the `BatchableTransformer` trait.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the updated stream that applies the batch transformer to each
    /// batch of nodes.
    #[must_use]
    pub fn then_in_batch(
        mut self,
        mut transformer: impl BatchableTransformer + WithBatchIndexingDefaults + 'static,
    ) -> Self {
        let concurrency = transformer.concurrency().unwrap_or(self.concurrency);

        transformer.with_indexing_defaults(self.indexing_defaults.clone());

        let transformer = Arc::new(transformer);
        self.stream = self
            .stream
            .try_chunks(transformer.batch_size().unwrap_or(self.batch_size))
            .map_ok(move |nodes| {
                let transformer = Arc::clone(&transformer);
                let span = trace_span!("then_in_batch", transformer);

                tokio::spawn(
                    async move {
                        batch_node_trace_log!(transformer, nodes, "batch transforming nodes");
                        transformer.batch_transform(nodes).await
                    }
                    .instrument(span.or_current()),
                )
                .map_err(anyhow::Error::from)
            })
            .err_into::<anyhow::Error>()
            .try_buffer_unordered(concurrency) // First get the streams from each future
            .try_flatten_unordered(None) // Then flatten all the streams back into one
            .boxed()
            .into();
        self
    }

    /// Adds a chunker transformer to the pipeline.
    ///
    /// # Arguments
    ///
    /// * `chunker` - A transformer that implements the `ChunkerTransformer` trait.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the updated stream that applies the chunker transformer to
    /// each node.
    #[must_use]
    pub fn then_chunk(mut self, chunker: impl ChunkerTransformer + 'static) -> Self {
        let chunker = Arc::new(chunker);
        let concurrency = chunker.concurrency().unwrap_or(self.concurrency);
        self.stream = self
            .stream
            .map_ok(move |node| {
                let chunker = Arc::clone(&chunker);
                let span = trace_span!("then_chunk", chunker);

                tokio::spawn(
                    async move {
                        node_trace_log!(chunker, node, "Chunking node");
                        chunker.transform_node(node).await
                    }
                    .instrument(span.or_current()),
                )
                .map_err(anyhow::Error::from)
            })
            .err_into::<anyhow::Error>()
            .try_buffer_unordered(concurrency)
            .try_flatten_unordered(None)
            .boxed()
            .into();

        self
    }

    /// Persists indexing nodes using the provided storage backend.
    ///
    /// # Arguments
    ///
    /// * `storage` - A storage backend that implements the `Storage` trait.
    ///
    /// # Returns
    ///
    /// An instance of `Pipeline` with the configured storage backend.
    ///
    /// # Panics
    ///
    /// Panics if batch size turns out to be not set and batch storage is still invoked.
    /// Pipeline only invokes batch storing if the batch size is set, so should be alright.
    #[must_use]
    pub fn then_store_with(mut self, storage: impl Persist + 'static) -> Self {
        let storage = Arc::new(storage);
        self.storage.push(storage.clone());
        // add storage to the stream instead of doing it at the end
        if storage.batch_size().is_some() {
            self.stream = self
                .stream
                .try_chunks(storage.batch_size().unwrap())
                .map_ok(move |nodes| {
                    let storage = Arc::clone(&storage);
                    let span = trace_span!("then_store_with_batched", storage);

                    tokio::spawn(
                        async move {
                            batch_node_trace_log!(storage, nodes, "batch storing nodes");
                            storage.batch_store(nodes).await
                        }
                        .instrument(span.or_current()),
                    )
                    .map_err(anyhow::Error::from)
                })
                .err_into::<anyhow::Error>()
                .try_buffer_unordered(self.concurrency)
                .try_flatten_unordered(None)
                .boxed()
                .into();
        } else {
            self.stream = self
                .stream
                .map_ok(move |node| {
                    let storage = Arc::clone(&storage);
                    let span = trace_span!("then_store_with", storage);

                    tokio::spawn(
                        async move {
                            node_trace_log!(storage, node, "Storing node");

                            storage.store(node).await
                        }
                        .instrument(span.or_current()),
                    )
                    .err_into::<anyhow::Error>()
                })
                .try_buffer_unordered(self.concurrency)
                .map(|x| x.and_then(|x| x))
                .boxed()
                .into();
        }

        self
    }

    /// Splits the stream into two streams based on a predicate.
    ///
    /// Note that this is not lazy. It will start consuming the stream immediately
    /// and send each item to the left or right stream based on the predicate.
    ///
    /// The other streams have a buffer, but should be started as soon as possible.
    /// The channels of the resulting streams are bounded and the parent stream will panic
    /// if sending fails.
    ///
    /// They can either be run concurrently, alternated between or merged back together.
    ///
    /// # Panics
    ///
    /// Panics if the receiving pipelines buffers are full or unavailable.
    #[must_use]
    pub fn split_by<P>(self, predicate: P) -> (Self, Self)
    where
        P: Fn(&Result<Node>) -> bool + Send + Sync + 'static,
    {
        let predicate = Arc::new(predicate);

        let (left_tx, left_rx) = mpsc::channel(1000);
        let (right_tx, right_rx) = mpsc::channel(1000);

        let stream = self.stream;
        let span = trace_span!("split_by");
        tokio::spawn(
            async move {
                stream
                    .for_each_concurrent(self.concurrency, move |item| {
                        let predicate = Arc::clone(&predicate);
                        let left_tx = left_tx.clone();
                        let right_tx = right_tx.clone();
                        async move {
                            if predicate(&item) {
                                tracing::trace!(?item, "Sending to left stream");
                                left_tx
                                    .send(item)
                                    .await
                                    .expect("Failed to send to left stream");
                            } else {
                                tracing::trace!(?item, "Sending to right stream");
                                right_tx
                                    .send(item)
                                    .await
                                    .expect("Failed to send to right stream");
                            }
                        }
                    })
                    .await;
            }
            .instrument(span.or_current()),
        );

        let left_pipeline = Self {
            stream: left_rx.into(),
            storage: self.storage.clone(),
            concurrency: self.concurrency,
            indexing_defaults: self.indexing_defaults.clone(),
            batch_size: self.batch_size,
        };

        let right_pipeline = Self {
            stream: right_rx.into(),
            storage: self.storage.clone(),
            concurrency: self.concurrency,
            indexing_defaults: self.indexing_defaults.clone(),
            batch_size: self.batch_size,
        };

        (left_pipeline, right_pipeline)
    }

    /// Merges two streams into one
    ///
    /// This is useful for merging two streams that have been split using the `split_by` method.
    ///
    /// The full stream can then be processed using the `run` method.
    #[must_use]
    pub fn merge(self, other: Self) -> Self {
        let stream = tokio_stream::StreamExt::merge(self.stream, other.stream);

        Self {
            stream: stream.boxed().into(),
            ..self
        }
    }

    /// Throttles the stream of nodes, limiting the rate to 1 per duration.
    ///
    /// Useful for rate limiting the indexing pipeline. Uses `tokio_stream::StreamExt::throttle`
    /// internally which has a granualarity of 1ms.
    #[must_use]
    pub fn throttle(mut self, duration: impl Into<Duration>) -> Self {
        self.stream = tokio_stream::StreamExt::throttle(self.stream, duration.into())
            .boxed()
            .into();
        self
    }

    // Silently filters out errors encountered by the pipeline.
    //
    // This method filters out errors encountered by the pipeline, preventing them from bubbling up
    // and terminating the stream. Note that errors are not logged.
    #[must_use]
    pub fn filter_errors(mut self) -> Self {
        self.stream = self
            .stream
            .filter_map(|result| async {
                match result {
                    Ok(node) => Some(Ok(node)),
                    Err(_e) => None,
                }
            })
            .boxed()
            .into();
        self
    }

    /// Provide a closure to selectively filter nodes or errors
    ///
    /// This allows you to skip specific errors or nodes, or do ad hoc inspection.
    ///
    /// If the closure returns true, the result is kept, otherwise it is skipped.
    #[must_use]
    pub fn filter<F>(mut self, filter: F) -> Self
    where
        F: Fn(&Result<Node>) -> bool + Send + Sync + 'static,
    {
        self.stream = self
            .stream
            .filter(move |result| {
                let will_retain = filter(result);

                async move { will_retain }
            })
            .boxed()
            .into();
        self
    }

    /// Logs all results processed by the pipeline.
    ///
    /// This method logs all results processed by the pipeline at the `DEBUG` level.
    #[must_use]
    pub fn log_all(self) -> Self {
        self.log_errors().log_nodes()
    }

    /// Logs all errors encountered by the pipeline.
    ///
    /// This method logs all errors encountered by the pipeline at the `ERROR` level.
    #[must_use]
    pub fn log_errors(mut self) -> Self {
        self.stream = self
            .stream
            .inspect_err(|e| tracing::error!(?e, "Error processing node"))
            .boxed()
            .into();
        self
    }

    /// Logs all nodes processed by the pipeline.
    ///
    /// This method logs all nodes processed by the pipeline at the `DEBUG` level.
    #[must_use]
    pub fn log_nodes(mut self) -> Self {
        self.stream = self
            .stream
            .inspect_ok(|node| tracing::debug!(?node, "Processed node: {:?}", node))
            .boxed()
            .into();
        self
    }

    /// Runs the indexing pipeline.
    ///
    /// This method processes the stream of nodes, applying all configured transformations and
    /// storing the results.
    ///
    /// # Returns
    ///
    /// A `Result` indicating the success or failure of the pipeline execution.
    ///
    /// # Errors
    ///
    /// Returns an error if no storage backend is configured or if any stage of the pipeline fails.
    #[tracing::instrument(skip_all, fields(total_nodes), name = "indexing_pipeline.run")]
    pub async fn run(mut self) -> Result<()> {
        tracing::info!(
            "Starting indexing pipeline with {} concurrency",
            self.concurrency
        );
        let now = std::time::Instant::now();
        if self.storage.is_empty() {
            anyhow::bail!("No storage configured for indexing pipeline");
        }

        // Ensure all storage backends are set up before processing nodes
        let setup_futures = self
            .storage
            .into_iter()
            .map(|storage| async move { storage.setup().await })
            .collect::<Vec<_>>();
        futures_util::future::try_join_all(setup_futures).await?;

        let mut total_nodes = 0;
        while self.stream.try_next().await?.is_some() {
            total_nodes += 1;
        }

        let elapsed_in_seconds = now.elapsed().as_secs();
        tracing::info!(
            elapsed_in_seconds,
            "Processed {} nodes in {} seconds",
            total_nodes,
            elapsed_in_seconds
        );
        tracing::Span::current().record("total_nodes", total_nodes);

        Ok(())
    }
}

#[cfg(test)]
mod tests {

    use super::*;
    use crate::persist::MemoryStorage;
    use mockall::Sequence;
    use swiftide_core::indexing::*;

    /// Tests a simple run of the indexing pipeline.
    #[test_log::test(tokio::test)]
    async fn test_simple_run() {
        let mut loader = MockLoader::new();
        let mut transformer = MockTransformer::new();
        let mut batch_transformer = MockBatchableTransformer::new();
        let mut chunker = MockChunkerTransformer::new();
        let mut storage = MockPersist::new();

        let mut seq = Sequence::new();

        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| vec![Ok(Node::default())].into());

        transformer.expect_transform_node().returning(|mut node| {
            node.chunk = "transformed".to_string();
            Ok(node)
        });
        transformer.expect_concurrency().returning(|| None);
        transformer.expect_name().returning(|| "transformer");

        batch_transformer
            .expect_batch_transform()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|nodes| IndexingStream::iter(nodes.into_iter().map(Ok)));
        batch_transformer.expect_concurrency().returning(|| None);
        batch_transformer.expect_name().returning(|| "transformer");
        batch_transformer.expect_batch_size().returning(|| None);

        chunker
            .expect_transform_node()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|node| {
                let mut nodes = vec![];
                for i in 0..3 {
                    let mut node = node.clone();
                    node.chunk = format!("transformed_chunk_{i}");
                    nodes.push(Ok(node));
                }
                nodes.into()
            });
        chunker.expect_concurrency().returning(|| None);
        chunker.expect_name().returning(|| "chunker");

        storage.expect_setup().returning(|| Ok(()));
        storage.expect_batch_size().returning(|| None);
        storage
            .expect_store()
            .times(3)
            .in_sequence(&mut seq)
            .withf(|node| node.chunk.starts_with("transformed_chunk_"))
            .returning(Ok);
        storage.expect_name().returning(|| "storage");

        let pipeline = Pipeline::from_loader(loader)
            .then(transformer)
            .then_in_batch(batch_transformer)
            .then_chunk(chunker)
            .then_store_with(storage);

        pipeline.run().await.unwrap();
    }

    #[tokio::test]
    async fn test_skipping_errors() {
        let mut loader = MockLoader::new();
        let mut transformer = MockTransformer::new();
        let mut storage = MockPersist::new();
        let mut seq = Sequence::new();
        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| vec![Ok(Node::default())].into());
        transformer
            .expect_transform_node()
            .returning(|_node| Err(anyhow::anyhow!("Error transforming node")));
        transformer.expect_concurrency().returning(|| None);
        transformer.expect_name().returning(|| "mock");
        storage.expect_setup().returning(|| Ok(()));
        storage.expect_batch_size().returning(|| None);
        storage.expect_store().times(0).returning(Ok);
        let pipeline = Pipeline::from_loader(loader)
            .then(transformer)
            .then_store_with(storage)
            .filter_errors();
        pipeline.run().await.unwrap();
    }

    #[tokio::test]
    async fn test_concurrent_calls_with_simple_transformer() {
        let mut loader = MockLoader::new();
        let mut transformer = MockTransformer::new();
        let mut storage = MockPersist::new();
        let mut seq = Sequence::new();
        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| {
                vec![
                    Ok(Node::default()),
                    Ok(Node::default()),
                    Ok(Node::default()),
                ]
                .into()
            });
        transformer
            .expect_transform_node()
            .times(3)
            .in_sequence(&mut seq)
            .returning(|mut node| {
                node.chunk = "transformed".to_string();
                Ok(node)
            });
        transformer.expect_concurrency().returning(|| Some(3));
        transformer.expect_name().returning(|| "transformer");
        storage.expect_setup().returning(|| Ok(()));
        storage.expect_batch_size().returning(|| None);
        storage.expect_store().times(3).returning(Ok);
        storage.expect_name().returning(|| "storage");

        let pipeline = Pipeline::from_loader(loader)
            .then(transformer)
            .then_store_with(storage);
        pipeline.run().await.unwrap();
    }

    #[tokio::test]
    async fn test_arbitrary_closures_as_transformer() {
        let mut loader = MockLoader::new();
        let transformer = |node: Node| {
            let mut node = node;
            node.chunk = "transformed".to_string();
            Ok(node)
        };
        let storage = MemoryStorage::default();
        let mut seq = Sequence::new();
        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| vec![Ok(Node::default())].into());

        let pipeline = Pipeline::from_loader(loader)
            .then(transformer)
            .then_store_with(storage.clone());
        pipeline.run().await.unwrap();

        dbg!(storage.clone());
        let processed_node = storage.get("0").await.unwrap();
        assert_eq!(processed_node.chunk, "transformed");
    }

    #[tokio::test]
    async fn test_arbitrary_closures_as_batch_transformer() {
        let mut loader = MockLoader::new();
        let batch_transformer = |nodes: Vec<Node>| {
            IndexingStream::iter(nodes.into_iter().map(|mut node| {
                node.chunk = "transformed".to_string();
                Ok(node)
            }))
        };
        let storage = MemoryStorage::default();
        let mut seq = Sequence::new();
        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| vec![Ok(Node::default())].into());

        let pipeline = Pipeline::from_loader(loader)
            .then_in_batch(batch_transformer)
            .then_store_with(storage.clone());
        pipeline.run().await.unwrap();

        dbg!(storage.clone());
        let processed_node = storage.get("0").await.unwrap();
        assert_eq!(processed_node.chunk, "transformed");
    }

    #[tokio::test]
    async fn test_filter_closure() {
        let mut loader = MockLoader::new();
        let storage = MemoryStorage::default();
        let mut seq = Sequence::new();
        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| {
                vec![
                    Ok(Node::default()),
                    Ok(Node::new("skip")),
                    Ok(Node::default()),
                ]
                .into()
            });
        let pipeline = Pipeline::from_loader(loader)
            .filter(|result| {
                let node = result.as_ref().unwrap();
                node.chunk != "skip"
            })
            .then_store_with(storage.clone());
        pipeline.run().await.unwrap();
        let nodes = storage.get_all().await;
        assert_eq!(nodes.len(), 2);
    }

    #[test_log::test(tokio::test)]
    async fn test_split_and_merge() {
        let mut loader = MockLoader::new();
        let storage = MemoryStorage::default();
        let mut seq = Sequence::new();
        loader
            .expect_into_stream()
            .times(1)
            .in_sequence(&mut seq)
            .returning(|| {
                vec![
                    Ok(Node::default()),
                    Ok(Node::new("will go left")),
                    Ok(Node::default()),
                ]
                .into()
            });

        let pipeline = Pipeline::from_loader(loader);
        let (mut left, mut right) = pipeline.split_by(|node| {
            if let Ok(node) = node {
                node.chunk.starts_with("will go left")
            } else {
                false
            }
        });

        // change the chunk to 'left'
        left = left
            .then(move |mut node: Node| {
                node.chunk = "left".to_string();

                Ok(node)
            })
            .log_all();

        right = right.then(move |mut node: Node| {
            node.chunk = "right".to_string();
            Ok(node)
        });

        left.merge(right)
            .then_store_with(storage.clone())
            .run()
            .await
            .unwrap();
        dbg!(storage.clone());

        let all_nodes = storage.get_all_values().await;
        assert_eq!(
            all_nodes.iter().filter(|node| node.chunk == "left").count(),
            1
        );
        assert_eq!(
            all_nodes
                .iter()
                .filter(|node| node.chunk == "right")
                .count(),
            2
        );
    }

    #[tokio::test]
    async fn test_all_steps_should_work_as_dyn_box() {
        let mut loader = MockLoader::new();
        loader
            .expect_into_stream_boxed()
            .returning(|| vec![Ok(Node::default())].into());

        let mut transformer = MockTransformer::new();
        transformer.expect_transform_node().returning(Ok);
        transformer.expect_concurrency().returning(|| None);
        transformer.expect_name().returning(|| "mock");

        let mut batch_transformer = MockBatchableTransformer::new();
        batch_transformer
            .expect_batch_transform()
            .returning(std::convert::Into::into);
        batch_transformer.expect_concurrency().returning(|| None);
        batch_transformer.expect_name().returning(|| "mock");
        let mut chunker = MockChunkerTransformer::new();
        chunker
            .expect_transform_node()
            .returning(|node| vec![node].into());
        chunker.expect_concurrency().returning(|| None);
        chunker.expect_name().returning(|| "mock");

        let mut storage = MockPersist::new();
        storage.expect_setup().returning(|| Ok(()));
        storage.expect_store().returning(Ok);
        storage.expect_batch_size().returning(|| None);
        storage.expect_name().returning(|| "mock");

        let pipeline = Pipeline::from_loader(Box::new(loader) as Box<dyn Loader>)
            .then(Box::new(transformer) as Box<dyn Transformer>)
            .then_in_batch(Box::new(batch_transformer) as Box<dyn BatchableTransformer>)
            .then_chunk(Box::new(chunker) as Box<dyn ChunkerTransformer>)
            .then_store_with(Box::new(storage) as Box<dyn Persist>);
        pipeline.run().await.unwrap();
    }
}