Implement pagination for QueryMsg::List

CosmWasm · Aug 29, 2020 · 963bf0c · 963bf0c
1 parent 6168761
commit 963bf0c
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Showing 4 changed files with 56 additions and 10 deletions.
diff --git a/contracts/cw20-atomic-swap/schema/query_msg.json b/contracts/cw20-atomic-swap/schema/query_msg.json
@@ -10,7 +10,23 @@
       ],
       "properties": {
         "list": {
-          "type": "object"
+          "type": "object",
+          "properties": {
+            "limit": {
+              "type": [
+                "integer",
+                "null"
+              ],
+              "format": "uint32",
+              "minimum": 0.0
+            },
+            "start_after": {
+              "type": [
+                "string",
+                "null"
+              ]
+            }
+          }
         }
       }
     },

diff --git a/contracts/cw20-atomic-swap/src/contract.rs b/contracts/cw20-atomic-swap/src/contract.rs
@@ -178,7 +178,7 @@ pub fn query<S: Storage, A: Api, Q: Querier>(
     msg: QueryMsg,
 ) -> StdResult<Binary> {
     match msg {
-        QueryMsg::List {} => to_binary(&query_list(deps)?),
+        QueryMsg::List { start_after, limit } => to_binary(&query_list(deps, start_after, limit)?),
         QueryMsg::Details { id } => to_binary(&query_details(deps, id)?),
     }
 }
@@ -200,9 +200,28 @@ fn query_details<S: Storage, A: Api, Q: Querier>(
     Ok(details)
 }
 
-fn query_list<S: Storage, A: Api, Q: Querier>(deps: &Extern<S, A, Q>) -> StdResult<ListResponse> {
+// Settings for pagination
+const MAX_LIMIT: u32 = 30;
+const DEFAULT_LIMIT: u32 = 10;
+
+fn query_list<S: Storage, A: Api, Q: Querier>(
+    deps: &Extern<S, A, Q>,
+    start_after: Option<String>,
+    limit: Option<u32>,
+) -> StdResult<ListResponse> {
+    let start = calc_range_start(start_after);
+    let limit = limit.unwrap_or(DEFAULT_LIMIT).min(MAX_LIMIT) as usize;
     Ok(ListResponse {
-        swaps: all_swap_ids(&deps.storage)?,
+        swaps: all_swap_ids(&deps.storage, start, limit)?,
+    })
+}
+
+// This will set the first key after the provided key, by appending a 1 byte
+fn calc_range_start(start_after: Option<String>) -> Option<Vec<u8>> {
+    start_after.map(|id| {
+        let mut v = Vec::from(id);
+        v.push(1);
+        v
     })
 }
 
@@ -565,7 +584,10 @@ mod tests {
         handle(&mut deps, env.clone(), HandleMsg::Create(create2.clone())).unwrap();
 
         // Get the list of ids
-        let query_msg = QueryMsg::List {};
+        let query_msg = QueryMsg::List {
+            start_after: None,
+            limit: None,
+        };
         let ids: ListResponse = from_binary(&query(&mut deps, query_msg).unwrap()).unwrap();
         assert_eq!(2, ids.swaps.len());
         assert_eq!(vec!["swap0001", "swap0002"], ids.swaps);

diff --git a/contracts/cw20-atomic-swap/src/msg.rs b/contracts/cw20-atomic-swap/src/msg.rs
@@ -49,7 +49,10 @@ pub fn is_valid_name(name: &str) -> bool {
 #[serde(rename_all = "snake_case")]
 pub enum QueryMsg {
     /// Show all open swaps. Return type is ListResponse.
-    List {},
+    List {
+        start_after: Option<String>,
+        limit: Option<u32>,
+    },
     /// Returns the details of the named swap, error if not created.
     /// Return type: DetailsResponse.
     Details { id: String },

diff --git a/contracts/cw20-atomic-swap/src/state.rs b/contracts/cw20-atomic-swap/src/state.rs
@@ -38,9 +38,14 @@ pub fn atomic_swaps_read<S: ReadonlyStorage>(storage: &S) -> ReadonlyBucket<S, A
 }
 
 /// This returns the list of ids for all active swaps
-pub fn all_swap_ids<S: ReadonlyStorage>(storage: &S) -> StdResult<Vec<String>> {
+pub fn all_swap_ids<S: ReadonlyStorage>(
+    storage: &S,
+    start: Option<Vec<u8>>,
+    limit: usize,
+) -> StdResult<Vec<String>> {
     prefixed_read(PREFIX_SWAP, storage)
-        .range(None, None, Order::Ascending)
+        .range(start.as_deref(), None, Order::Ascending)
+        .take(limit)
         .map(|(k, _)| String::from_utf8(k).map_err(|_| StdError::invalid_utf8("Parsing swap id")))
         .collect()
 }
@@ -55,7 +60,7 @@ mod tests {
     #[test]
     fn test_no_swap_ids() {
         let storage = MockStorage::new();
-        let ids = all_swap_ids(&storage).unwrap();
+        let ids = all_swap_ids(&storage, None, 10).unwrap();
         assert_eq!(0, ids.len());
     }
 
@@ -81,7 +86,7 @@ mod tests {
             .save("zen".as_bytes(), &dummy_swap())
             .unwrap();
 
-        let ids = all_swap_ids(&storage).unwrap();
+        let ids = all_swap_ids(&storage, None, 10).unwrap();
         assert_eq!(3, ids.len());
         assert_eq!(
             vec!["assign".to_string(), "lazy".to_string(), "zen".to_string()],