Begin add watch mechanism to Bayou

1 files changed, 29 insertions, 0 deletions

diff --git a/src/k2v_util.rs b/src/k2v_util.rs
new file mode 100644
index 0000000..9dadab4
--- /dev/null
+++ b/src/k2v_util.rs
@@ -0,0 +1,29 @@
+use anyhow::Result;
+
+use k2v_client::{CausalValue, CausalityToken, K2vClient};
+
+// ---- UTIL: function to wait for a value to have changed in K2V ----
+
+pub async fn k2v_wait_value_changed(
+    k2v: &K2vClient,
+    pk: &str,
+    sk: &str,
+    prev_ct: &Option<CausalityToken>,
+) -> Result<CausalValue> {
+    loop {
+        if let Some(ct) = prev_ct {
+            match k2v.poll_item(pk, sk, ct.clone(), None).await? {
+                None => continue,
+                Some(cv) => return Ok(cv),
+            }
+        } else {
+            match k2v.read_item(pk, sk).await {
+                Err(k2v_client::Error::NotFound) => {
+                    k2v.insert_item(pk, sk, vec![0u8], None).await?;
+                }
+                Err(e) => return Err(e.into()),
+                Ok(cv) => return Ok(cv),
+            }
+        }
+    }
+}