Add scan convenience method and refactor sscan to use new generic internal implementation for scan

Author: Mordil

Sources/NIORedis/Commands/BasicCommands.swift

@@ -189,3 +189,57 @@ extension RedisCommandExecutor {
             .mapFromRESP()
     }
 }
+
+extension RedisCommandExecutor {
+    /// Incrementally iterates over all keys in the currently selected database.
+    ///
+    /// [https://redis.io/commands/scan](https://redis.io/commands/scan)
+    /// - Parameters:
+    ///     - count: The number of elements to advance by. Redis default is 10.
+    ///     - matching: A glob-style pattern to filter values to be selected from the result set.
+    /// - Returns: A cursor position for additional invocations with a limited collection of keys stored in the database.
+    @inlinable
+    public func scan(
+        _ key: String,
+        atPosition pos: Int = 0,
+        count: Int? = nil,
+        matching match: String? = nil) -> EventLoopFuture<(Int, [String])>
+    {
+        return _scan(command: "SCAN", resultType: [String].self, key, pos, count, match)
+    }
+
+    @inline(__always)
+    @usableFromInline func _scan<T: RESPValueConvertible>(
+        command: String,
+        resultType: T.Type,
+        _ key: String,
+        _ pos: Int,
+        _ count: Int?,
+        _ match: String?) -> EventLoopFuture<(Int, T)>
+    {
+        var args: [RESPValueConvertible] = [key, pos]
+
+        if let m = match {
+            args.append("match")
+            args.append(m)
+        }
+        if let c = count {
+            args.append("count")
+            args.append(c)
+        }
+
+        let response = send(command: command, with: args).mapFromRESP(to: [RESPValue].self)
+        let position = response.flatMapThrowing { result -> Int in
+            guard
+                let value = result[0].string,
+                let position = Int(value)
+                else { throw RedisError(identifier: #function, reason: "Unexpected value in response: \(result[0])") }
+            return position
+        }
+        let elements = response
+            .map { return $0[1] }
+            .mapFromRESP(to: resultType)
+
+        return position.and(elements)
+    }
+}

Sources/NIORedis/Commands/SetCommands.swift

@@ -138,42 +138,19 @@ extension RedisCommandExecutor {
             .mapFromRESP()
     }
 
-    /// Incrementally iterates over a set, returning a cursor position for additional calls with a limited collection
-    /// of the entire set.
+    /// Incrementally iterates over all values in a set.
     ///
     /// [https://redis.io/commands/sscan](https://redis.io/commands/sscan)
     /// - Parameters:
     ///     - count: The number of elements to advance by. Redis default is 10.
     ///     - matching: A glob-style pattern to filter values to be selected from the result set.
+    /// - Returns: A cursor position for additional invocations with a limited collection of values stored at the keys.
     public func sscan(
         _ key: String,
         atPosition pos: Int = 0,
         count: Int? = nil,
-        matching match: String? = nil
-    ) -> EventLoopFuture<(Int, [RESPValue])> {
-        var args: [RESPValueConvertible] = [key, pos]
-
-        if let m = match {
-            args.append("match")
-            args.append(m)
-        }
-        if let c = count {
-            args.append("count")
-            args.append(c)
-        }
-
-        let response = send(command: "SSCAN", with: args).mapFromRESP(to: [RESPValue].self)
-        let position = response.flatMapThrowing { result -> Int in
-            guard
-                let value = result[0].string,
-                let position = Int(value)
-            else { throw RedisError(identifier: #function, reason: "Unexpected value in response: \(result[0])") }
-            return position
-        }
-        let elements = response
-            .map { return $0[1] }
-            .mapFromRESP(to: [RESPValue].self)
-
-        return position.and(elements)
+        matching match: String? = nil) -> EventLoopFuture<(Int, [RESPValue])>
+    {
+        return _scan(command: "SSCAN", resultType: [RESPValue].self, key, pos, count, match)
     }
 }