fix(firo): tighten spark cache reader snapshots

Author: reubenyap

lib/db/sqlite/firo_cache_coordinator.dart

@@ -411,18 +411,37 @@ abstract class FiroCacheCoordinator {
     int groupId,
     CryptoCurrencyNetwork network,
   ) async {
-    return await _setLocks[network]!.protect(() async {
-      final info = await getLatestSetInfoForGroupId(groupId, network);
-      if (info == null) {
-        return null;
-      }
+    final resultSet = await _Reader._getSetCoinsAndLatestSetInfoForGroupId(
+      groupId,
+      db: _FiroCache.setCacheDB(network),
+    );
+    if (resultSet.isEmpty) {
+      return null;
+    }
 
-      final coins = await getSetCoinsForGroupId(
-        groupId,
-        network: network,
-      );
-      return (meta: info, coins: coins);
-    });
+    final first = resultSet.first;
+    final coins = resultSet
+        .map(
+          (row) => RawSparkCoin(
+            serialized: row["serialized"] as String,
+            txHash: row["txHash"] as String,
+            context: row["context"] as String,
+            groupId: groupId,
+          ),
+        )
+        .toList()
+        .reversed
+        .toList();
+
+    return (
+      meta: SparkAnonymitySetMeta(
+        coinGroupId: groupId,
+        blockHash: first["blockHash"] as String,
+        setHash: first["setHash"] as String,
+        size: first["size"] as int,
+      ),
+      coins: coins,
+    );
   }
 
   static Future<SparkAnonymitySetMeta?> getLatestSetInfoForGroupId(

lib/db/sqlite/firo_cache_reader.dart

@@ -49,6 +49,36 @@ abstract class _Reader {
     return db.select("$query;");
   }
 
+  static Future<ResultSet> _getSetCoinsAndLatestSetInfoForGroupId(
+    int groupId, {
+    required Database db,
+  }) async {
+    const query = """
+      WITH LatestSet AS (
+        SELECT blockHash, setHash, size
+        FROM SparkSet
+        WHERE groupId = ? AND complete = 1
+        ORDER BY size DESC, id DESC
+        LIMIT 1
+      )
+      SELECT
+        LatestSet.blockHash,
+        LatestSet.setHash,
+        LatestSet.size,
+        sc.serialized,
+        sc.txHash,
+        sc.context,
+        sc.groupId
+      FROM LatestSet
+      JOIN SparkSet AS ss ON ss.groupId = ? AND ss.complete = 1
+      JOIN SparkSetCoins AS ssc ON ss.id = ssc.setId
+      JOIN SparkCoin AS sc ON ssc.coinId = sc.id
+      ORDER BY ss.id ASC, ssc.orderKey DESC, ssc.id ASC;
+    """;
+
+    return db.select("$query;", [groupId, groupId]);
+  }
+
   static Future<ResultSet> _getSetCoinsForGroupIdAndBlockHash(
     int groupId,
     String blockHash, {
@@ -58,7 +88,9 @@ abstract class _Reader {
         WITH TargetBlock AS (
           SELECT id
           FROM SparkSet
-          WHERE blockHash = ? AND complete = 1
+          WHERE blockHash = ? AND groupId = ? AND complete = 1
+          ORDER BY id DESC
+          LIMIT 1
         ),
         TargetSets AS (
           SELECT id AS setId
@@ -80,7 +112,7 @@ abstract class _Reader {
                  SparkSetCoins.id ASC;
     """;
 
-    return db.select("$query;", [blockHash, groupId]);
+    return db.select("$query;", [blockHash, groupId, groupId]);
   }
 
   static Future<bool> _checkSetInfoForGroupIdExists(