feat: handle txn ids

src/database/transaction_ids.rs

@@ -0,0 +1,43 @@
+use crate::Result;
+use ruma::{DeviceId, UserId};
+use sled::IVec;
+
+pub struct TransactionIds {
+    pub(super) userdevicetxnid_response: sled::Tree, // Response can be empty (/sendToDevice) or the event id (/send)
+}
+
+impl TransactionIds {
+    pub fn add_txnid(
+        &self,
+        user_id: &UserId,
+        device_id: &DeviceId,
+        txn_id: &str,
+        data: &[u8],
+    ) -> Result<()> {
+        let mut key = user_id.as_bytes().to_vec();
+        key.push(0xff);
+        key.extend_from_slice(device_id.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(txn_id.as_bytes());
+
+        self.userdevicetxnid_response.insert(key, data)?;
+
+        Ok(())
+    }
+
+    pub fn existing_txnid(
+        &self,
+        user_id: &UserId,
+        device_id: &DeviceId,
+        txn_id: &str,
+    ) -> Result<Option<IVec>> {
+        let mut key = user_id.as_bytes().to_vec();
+        key.push(0xff);
+        key.extend_from_slice(device_id.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(txn_id.as_bytes());
+
+        // If there's no entry, this is a new transaction
+        Ok(self.userdevicetxnid_response.get(key)?)
+    }
+}