introduce dedicated return type for PollRange

src/k2v-client/bin/k2v-cli.rs

@@ -311,23 +311,19 @@ impl BatchOutputKind {
 			.collect::<Vec<_>>()
 	}
 
-	fn display_poll_range_output(
-		&self,
-		seen_marker: String,
-		values: BTreeMap<String, CausalValue>,
-	) -> ! {
+	fn display_poll_range_output(&self, poll_range: PollRangeResult) -> ! {
 		if self.json {
 			let json = serde_json::json!({
-				"values": self.values_json(values),
-				"seen_marker": seen_marker,
+				"values": self.values_json(poll_range.items),
+				"seen_marker": poll_range.seen_marker,
 			});
 
 			let stdout = std::io::stdout();
 			serde_json::to_writer_pretty(stdout, &json).unwrap();
 			exit(0)
 		} else {
-			println!("seen marker: {}", seen_marker);
-			self.display_human_output(values)
+			println!("seen marker: {}", poll_range.seen_marker);
+			self.display_human_output(poll_range.items)
 		}
 	}
 
@@ -501,8 +497,8 @@ async fn main() -> Result<(), Error> {
 				)
 				.await?;
 			match res {
-				Some((items, seen_marker)) => {
-					output_kind.display_poll_range_output(seen_marker, items);
+				Some(poll_range_output) => {
+					output_kind.display_poll_range_output(poll_range_output);
 				}
 				None => {
 					if output_kind.json {

src/k2v-client/lib.rs

@@ -182,7 +182,7 @@ impl K2vClient {
 		filter: Option<PollRangeFilter<'_>>,
 		seen_marker: Option<&str>,
 		timeout: Option<Duration>,
-	) -> Result<Option<(BTreeMap<String, CausalValue>, String)>, Error> {
+	) -> Result<Option<PollRangeResult>, Error> {
 		let timeout = timeout.unwrap_or(DEFAULT_POLL_TIMEOUT);
 
 		let request = PollRangeRequest {
@@ -217,7 +217,10 @@ impl K2vClient {
 			})
 			.collect::<BTreeMap<_, _>>();
 
-		Ok(Some((items, resp.seen_marker)))
+		Ok(Some(PollRangeResult {
+			items,
+			seen_marker: resp.seen_marker,
+		}))
 	}
 
 	/// Perform an InsertItem request, inserting a value for a single pk+sk.
@@ -570,6 +573,7 @@ pub struct Filter<'a> {
 	pub reverse: bool,
 }
 
+/// Filter for a poll range operations.
 #[derive(Debug, Default, Clone, Serialize)]
 pub struct PollRangeFilter<'a> {
 	pub start: Option<&'a str>,
@@ -577,6 +581,15 @@ pub struct PollRangeFilter<'a> {
 	pub prefix: Option<&'a str>,
 }
 
+/// Response to a poll_range query
+#[derive(Debug, Default, Clone, Serialize)]
+pub struct PollRangeResult {
+	/// List of items that have changed since last PollRange call.
+	pub items: BTreeMap<String, CausalValue>,
+	/// opaque string representing items already seen for future PollRange calls.
+	pub seen_marker: String,
+}
+
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
 struct PollRangeRequest<'a> {