feat: add subscriptions

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/crunch-traits/src/lib.rs

@@ -0,0 +1,46 @@
+use std::{fmt::Display, sync::Arc};
+
+use async_trait::async_trait;
+use errors::{DeserializeError, PersistenceError, SerializeError, TransportError};
+
+#[async_trait]
+pub trait Persistence {
+    async fn insert(&self, event_info: &EventInfo, content: Vec<u8>) -> anyhow::Result<()>;
+    async fn next(&self) -> Option<String>;
+    async fn get(&self, event_id: &str) -> Result<Option<(EventInfo, Vec<u8>)>, PersistenceError>;
+    async fn update_published(&self, event_id: &str) -> Result<(), PersistenceError>;
+}
+
+pub trait Serializer {
+    fn serialize(&self) -> Result<Vec<u8>, SerializeError>;
+}
+
+pub trait Deserializer {
+    fn deserialize(raw: Vec<u8>) -> Result<Self, DeserializeError>
+    where
+        Self: Sized;
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct EventInfo {
+    pub domain: &'static str,
+    pub entity_type: &'static str,
+    pub event_name: &'static str,
+}
+
+impl Display for EventInfo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&format!(
+            "domain: {}, entity_type: {}",
+            self.domain, self.entity_type
+        ))
+    }
+}
+
+pub trait Event: Serializer + Deserializer {
+    fn event_info(&self) -> EventInfo;
+}
+
+pub mod errors;
+mod transport;
+pub use transport::*;