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use super::stateless_op::StatelessOp;
use crate::channels::operator_io::Output;
use crate::stream::StreamBuilder;
use crate::types::{Data, DataMessage, MaybeKey, Message, Timestamp};
/// Apply a function to every message in a stream
pub trait Map<K, V, T, VO>: super::sealed::Sealed {
/// Map transforms every value in a datastream into a different value
/// by applying a given function or closure.
///
/// # Example
/// ```rust
/// use malstrom::operators::*;
/// use malstrom::runtime::SingleThreadRuntime;
/// use malstrom::snapshot::NoPersistence;
/// use malstrom::sources::{SingleIteratorSource, StatelessSource};
/// use malstrom::worker::StreamProvider;
/// use malstrom::sinks::{VecSink, StatelessSink};
///
/// let sink = VecSink::new();
/// let sink_clone = sink.clone();
///
/// SingleThreadRuntime::builder()
/// .persistence(NoPersistence)
/// .build(move |provider: &mut dyn StreamProvider| {
/// provider.new_stream()
/// .source("numbers", StatelessSource::new(SingleIteratorSource::new(0..100)))
/// .map("map", |x| x * 2)
/// .sink("sink", StatelessSink::new(sink_clone));
/// })
/// .execute()
/// .unwrap();
///
/// let expected: Vec<i32> = (0..100).map(|x| x * 2).collect();
/// let out: Vec<i32> = sink.into_iter().map(|x| x.value).collect();
/// assert_eq!(out, expected);
/// ```
fn map(self, name: &str, mapper: impl (FnMut(V) -> VO) + 'static) -> StreamBuilder<K, VO, T>;
}
impl<K, V, T, VO> Map<K, V, T, VO> for StreamBuilder<K, V, T>
where
K: MaybeKey,
V: Data,
VO: Data,
T: Timestamp,
{
fn map(
self,
name: &str,
mut mapper: impl (FnMut(V) -> VO) + 'static,
) -> StreamBuilder<K, VO, T> {
self.stateless_op(
name,
move |item: DataMessage<K, V, T>, out: &mut Output<K, VO, T>| {
out.send(Message::Data(DataMessage::new(
item.key,
mapper(item.value),
item.timestamp,
)));
},
)
}
}
#[cfg(test)]
mod tests {
use itertools::Itertools;
use crate::{
operators::{map::Map, source::Source, Sink},
sinks::StatelessSink,
sources::{SingleIteratorSource, StatelessSource},
testing::{get_test_rt, VecSink},
};
#[test]
fn test_map() {
let input = ["hello", "world", "foo", "bar"];
let expected = input.iter().map(|x| x.len()).collect_vec();
let collector = VecSink::new();
let rt = get_test_rt(|provider| {
provider
.new_stream()
.source(
"source",
StatelessSource::new(SingleIteratorSource::new(input)),
)
.map("get-len", |x| x.len())
.sink("sink", StatelessSink::new(collector.clone()));
});
rt.execute().unwrap();
assert_eq!(
collector.into_iter().map(|x| x.value).collect_vec(),
expected
);
}
}