Implement replay-safe authorized public HTTP API

crates/remora-durable/src/ledger.rs

@@ -48,6 +48,51 @@ pub struct MutationOutcome {
     pub response: Value,
 }
 
+pub async fn observe_mutation(
+    pool: &PgPool,
+    scope: MutationScope<'_>,
+    kind: &str,
+    eligibility_claim: &[u8],
+    request_fingerprint: RequestFingerprint,
+) -> Result<Option<MutationOutcome>, DurableError> {
+    let existing = sqlx::query_as::<_, (String, Vec<u8>, Vec<u8>, String, Value)>(
+        "SELECT kind, eligibility_claim, request_fingerprint, response_status, response_body
+         FROM mutation_records
+         WHERE scope_subject = $1
+           AND scope_operation = $2
+           AND operation_key = $3",
+    )
+    .bind(scope.subject.as_str())
+    .bind(scope.operation)
+    .bind(scope.key)
+    .fetch_optional(pool)
+    .await?;
+    existing
+        .map(
+            |(
+                stored_kind,
+                stored_eligibility_claim,
+                stored_request_fingerprint,
+                response_status,
+                response_body,
+            )| {
+                observe_existing(
+                    kind,
+                    eligibility_claim,
+                    request_fingerprint.as_bytes(),
+                    StoredRecord {
+                        kind: stored_kind,
+                        eligibility_claim: stored_eligibility_claim,
+                        request_fingerprint: stored_request_fingerprint,
+                        response_status,
+                        response_body,
+                    },
+                )
+            },
+        )
+        .transpose()
+}
+
 #[derive(Clone, Debug)]
 struct StoredRecord {
     kind: String,

crates/remora-durable/src/lib.rs

@@ -19,6 +19,7 @@ pub use cursor::{CursorCodec, KeysetCursor, KeysetPosition, first_page_cursor, n
 pub use error::DurableError;
 pub use ledger::{
     MutationDisposition, MutationOutcome, MutationStatus, execute_mutation, execute_mutation_in_tx,
+    observe_mutation,
 };
 pub use migrate::{migrate, migrator};
 pub use outbox::{