fix: Add payload merger to merge context and message

Sources/Confidence/EventSenderEngine.swift

@@ -22,6 +22,7 @@ final class EventSenderEngineImpl: EventSenderEngine {
     private let flushPolicies: [FlushPolicy]
     private let uploader: ConfidenceClient
     private let clientSecret: String
+    private let payloadMerger: PayloadMerger = PayloadMergerImpl()
 
     init(
         clientSecret: String,
@@ -79,11 +80,9 @@ final class EventSenderEngineImpl: EventSenderEngine {
     }
 
     func emit(eventName: String, message: ConfidenceStruct, context: ConfidenceStruct) {
-        var mutablePayload = context
-        mutablePayload["message"] = ConfidenceValue(structure: message)
         writeReqChannel.send(ConfidenceEvent(
             name: eventName,
-            payload: mutablePayload,
+            payload: payloadMerger.merge(context: context, message: message),
             eventTime: Date.backport.now)
         )
     }

Sources/Confidence/PayloadMerger.swift

@@ -0,0 +1,19 @@
+import Foundation
+
+internal protocol PayloadMerger {
+    func merge(context: ConfidenceStruct, message: ConfidenceStruct) -> ConfidenceStruct
+}
+
+internal struct PayloadMergerImpl: PayloadMerger {
+    func merge(context: ConfidenceStruct, message: ConfidenceStruct) -> ConfidenceStruct {
+        var map: ConfidenceStruct = context
+        map += message
+        return map
+    }
+}
+
+extension Dictionary {
+    static func += (lhs: inout Self, rhs: Self) {
+        lhs.merge(rhs) { _, new in new }
+    }
+}

Tests/ConfidenceTests/EventSenderEngineTest.swift

@@ -70,11 +70,8 @@ final class EventSenderEngineTest: XCTestCase {
         wait(for: [expectation], timeout: 5)
         XCTAssertEqual(try XCTUnwrap(uploader.calledRequest)[0].eventDefinition, "my_event")
         XCTAssertEqual(try XCTUnwrap(uploader.calledRequest)[0].payload, NetworkStruct(fields: [
-            "message": .structure(.init(fields: [
-                "a": .number(0.0),
-                "message": .number(1.0)
-            ])),
-            "a": .number(2.0)
+            "a": .number(0.0),
+            "message": .number(1.0)
         ]))
         cancellable.cancel()
     }

Tests/ConfidenceTests/PayloadMergerTests.swift

@@ -0,0 +1,16 @@
+import XCTest
+@testable import Confidence
+
+class PayloadMergerTests: XCTestCase {
+    func testMerge() {
+        let context = ["a": ConfidenceValue(string: "hello"), "b": ConfidenceValue(string: "world")]
+        let message = ["b": ConfidenceValue(string: "west"), "c": ConfidenceValue(string: "world")]
+        let expected = [
+            "a": ConfidenceValue(string: "hello"),
+            "b": ConfidenceValue(string: "west"),
+            "c": ConfidenceValue(string: "world")
+        ]
+        let merged = PayloadMergerImpl().merge(context: context, message: message)
+        XCTAssertEqual(merged, expected)
+    }
+}