Add ValkeyClusterDiscovery (#33)

Co-authored-by: Adam Fowler <[email protected]>

Author: fabianfett

Sources/Valkey/Cluster/ValkeyClusterDiscovery.swift

@@ -0,0 +1,78 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the swift-valkey project
+//
+// Copyright (c) 2025 the swift-valkey authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See swift-valkey/CONTRIBUTORS.txt for the list of swift-valkey authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+/// Allows the cluster client to initially find at least one node in the cluster or find the
+/// nodes again if connection to the has been lost.
+public protocol ValkeyClusterDiscovery {
+    /// A type that describes a single node in a valkey cluster
+    associatedtype NodeDescription: ValkeyNodeDescriptionProtocol
+
+    /// A type that describes multiple nodes in a valkey cluster
+    associatedtype NodeDescriptions: Collection<NodeDescription>
+
+    /// Lookup all the nodes within the cluster.
+    func lookupNodes() async throws -> NodeDescriptions
+}
+
+/// A description of a single node that is part of a valkey cluster
+public protocol ValkeyNodeDescriptionProtocol: Sendable, Equatable {
+    /// The node's host name.
+    var host: String? { get }
+    /// The node's ip address.
+    var ip: String? { get }
+    /// The nodes endpoint. This should normally be the ``host`` if the node has a routable hostname.
+    /// Otherwise it is the ``ip``. This property is used to create connections to the node.
+    var endpoint: String { get }
+    /// The node's redis port
+    var port: Int { get }
+    /// Defines if TLS shall be used to create a connection to the node
+    var useTLS: Bool { get }
+}
+
+public struct ValkeyStaticClusterDiscovery: ValkeyClusterDiscovery {
+
+    public struct NodeDescription: ValkeyNodeDescriptionProtocol {
+        public var host: String?
+        public var ip: String?
+        public var endpoint: String
+        public var port: Int
+        public var useTLS: Bool
+
+        public init(host: String, ip: String? = nil, port: Int = 5678, useTLS: Bool = true) {
+            self.host = host
+            self.ip = ip
+            self.endpoint = host
+            self.port = port
+            self.useTLS = useTLS
+        }
+
+        public init(ip: String, port: Int = 5678, useTLS: Bool = false) {
+            self.host = nil
+            self.ip = ip
+            self.endpoint = ip
+            self.port = port
+            self.useTLS = useTLS
+        }
+    }
+
+    private var nodes: [NodeDescription]
+
+    public init(_ nodes: [NodeDescription]) {
+        self.nodes = nodes
+    }
+
+    public func lookupNodes() -> [NodeDescription] {
+        self.nodes
+    }
+}