Add subscript to XREADMessage for fields (#113)

* Add subscript to XREADMessage for fields

* Comment with suggestion for alternative

Author: adam-fowler

Sources/Valkey/Commands/Custom/StreamCustomCommands.swift

@@ -28,6 +28,41 @@ public struct XREADMessage: RESPTokenDecodable, Sendable {
             throw RESPParsingError(code: .unexpectedType, buffer: token.base)
         }
     }
+
+    /// Accesses the value associated with the specified field key in the stream.
+    ///
+    /// The field collection is an array so subscript access is a O(n) where n is
+    /// the number of fields.
+    ///
+    /// Alternatively the user can create a Dictionary if there are a large number of
+    /// fields and many are accessed
+    /// ```
+    /// let fields = Dictionary(uniqueKeysWithValues: message.fields)
+    /// let field = field["fieldName"]
+    /// ```
+    ///
+    /// - Parameter key: The field key to look up.
+    /// - Returns: The `RESPToken` value associated with the given key, or `nil` if the key does not exist.
+    public subscript(field key: String) -> RESPToken? {
+        fields.first(where: { $0.key == key })?.value
+    }
+
+    /// Accesses the values associated with the specified field key as an array of `RESPToken`.
+    ///
+    /// The field collection is an array so subscript access is a O(n) where n is
+    /// the number of fields.
+    ///
+    /// - Parameter key: The field key to retrieve values for.
+    /// - Returns: An array of `RESPToken` values associated with the given field key.
+    public subscript(fields key: String) -> [RESPToken] {
+        fields.compactMap {
+            if $0.key == key {
+                $0.value
+            } else {
+                nil
+            }
+        }
+    }
 }
 
 @_documentation(visibility: internal)

Tests/ValkeyTests/CommandTests.swift

@@ -381,18 +381,13 @@ struct CommandTests {
             let stream2 = try #require(result.streams.first { $0.key == "key2" })
             #expect(stream1.key == "key1")
             #expect(stream1.messages[0].id == "event1")
-            #expect(stream1.messages[0].fields[0].key == "field1")
-            #expect(try stream1.messages[0].fields[0].value.decode(as: String.self) == "value1")
+            #expect(try stream1.messages[0][field: "field1"]?.decode(as: String.self) == "value1")
             #expect(stream2.key == "key2")
             #expect(stream2.messages[0].id == "event2")
-            #expect(stream2.messages[0].fields[0].key == "field2")
-            #expect(try stream2.messages[0].fields[0].value.decode(as: String.self) == "value2")
+            #expect(try stream2.messages[0][field: "field2"]?.decode(as: String.self) == "value2")
             #expect(stream2.messages[1].id == "event3")
-            #expect(stream2.messages[1].fields[0].key == "field3")
-            #expect(try stream2.messages[1].fields[0].value.decode(as: String.self) == "value3")
-            #expect(stream2.messages[1].fields[1].key == "field4")
-            #expect(try stream2.messages[1].fields[1].value.decode(as: String.self) == "value4")
-
+            #expect(try stream2.messages[1][field: "field3"]?.decode(as: String.self) == "value3")
+            #expect(try stream2.messages[1][field: "field4"]?.decode(as: String.self) == "value4")
         }
 
         @Test