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use crate::batchable::Batchable;
use std::collections::HashMap;
use std::iter::once;
use time::OffsetDateTime;
#[must_use]
#[derive(Debug)]
pub enum BatchAdd<B: Batchable> {
Added,
Duplicate,
Split(Batch<B>),
}
#[derive(Debug)]
pub struct Batch<B: Batchable> {
batch_start: OffsetDateTime,
batch_end: OffsetDateTime,
events: HashMap<B::Key, B>,
}
impl<B: Batchable> Batch<B> {
pub fn new(batch_start: OffsetDateTime, batch_end: OffsetDateTime, event: B) -> Batch<B> {
let mut events = HashMap::new();
events.insert(event.key(), event);
Batch {
batch_start,
batch_end,
events,
}
}
pub fn batch_start(&self) -> OffsetDateTime {
self.batch_start
}
pub fn batch_end(&self) -> OffsetDateTime {
self.batch_end
}
pub fn add(&mut self, event: B) -> BatchAdd<B> {
let key = event.key();
if let Some(existing_event) = self.events.get(&key) {
let existing_event_time = existing_event.event_time();
if event.event_time() == existing_event_time {
return BatchAdd::Duplicate;
}
return BatchAdd::Split(self.split(existing_event_time, event));
}
self.events.insert(key, event);
BatchAdd::Added
}
fn split(&mut self, existing_event_time: OffsetDateTime, event: B) -> Batch<B> {
let split_point = midpoint(existing_event_time, event.event_time());
let mut new_batch_events = HashMap::new();
let new_batch_end = self.batch_end;
let all_events = std::mem::take(&mut self.events);
self.batch_end = split_point;
// Go over all the events in this batch plus the new event and allocate them,
// either the existing batch or the new batch.
for event in all_events
.into_iter()
.map(|(_key, event)| event)
.chain(once(event))
{
let event_time = event.event_time();
if event_time < split_point {
self.events.insert(event.key(), event);
} else {
new_batch_events.insert(event.key(), event);
}
}
Batch {
batch_start: split_point,
batch_end: new_batch_end,
events: new_batch_events,
}
}
pub fn into_vec(self) -> Vec<B> {
self.events.into_iter().map(|(_k, v)| v).collect()
}
}
fn midpoint(event_time1: OffsetDateTime, event_time2: OffsetDateTime) -> OffsetDateTime {
let gap = event_time1 - event_time2;
event_time2 + gap / 2
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn add() {
let batch_start = OffsetDateTime::from_unix_timestamp(0).unwrap();
let batch_end = OffsetDateTime::from_unix_timestamp(100).unwrap();
let event1 = TestBatchEvent::new(1, 40);
let event2 = TestBatchEvent::new(2, 60);
let mut batch = Batch::new(batch_start, batch_end, event1.clone());
assert!(matches!(batch.add(event2.clone()), BatchAdd::Added));
let result = batch.into_vec();
assert_eq!(result.len(), 2);
assert!(result.contains(&event1));
assert!(result.contains(&event2));
}
#[test]
fn split() {
let batch_start = OffsetDateTime::from_unix_timestamp(0).unwrap();
let batch_end = OffsetDateTime::from_unix_timestamp(100).unwrap();
let event1 = TestBatchEvent::new(1, 40);
let event2 = TestBatchEvent::new(1, 60);
let mut batch1 = Batch::new(batch_start, batch_end, event1.clone());
match batch1.add(event2.clone()) {
BatchAdd::Split(batch2) => {
let result1 = batch1.into_vec();
assert_eq!(result1.len(), 1);
assert!(result1.contains(&event1));
let result2 = batch2.into_vec();
assert_eq!(result2.len(), 1);
assert!(result2.contains(&event2));
}
_ => panic!("Expected split"),
}
}
#[test]
fn duplicate() {
let batch_start = OffsetDateTime::from_unix_timestamp(0).unwrap();
let batch_end = OffsetDateTime::from_unix_timestamp(100).unwrap();
let event1 = TestBatchEvent::new(1, 40);
let event2 = TestBatchEvent::new(1, 40);
let mut batch = Batch::new(batch_start, batch_end, event1.clone());
assert!(matches!(batch.add(event2), BatchAdd::Duplicate));
let result = batch.into_vec();
assert_eq!(result.len(), 1);
assert!(result.contains(&event1));
}
#[derive(Debug, Clone, Eq, PartialEq)]
struct TestBatchEvent {
key: u64,
event_time: OffsetDateTime,
}
impl TestBatchEvent {
fn new(key: u64, event_time: i64) -> TestBatchEvent {
let event_time = OffsetDateTime::from_unix_timestamp(event_time).unwrap();
TestBatchEvent { key, event_time }
}
}
impl Batchable for TestBatchEvent {
type Key = u64;
fn key(&self) -> Self::Key {
self.key
}
fn event_time(&self) -> OffsetDateTime {
self.event_time
}
}
}
|
