Fix event stream line parsing to handle CRLF and empty lines correctly (#89)

* Optimized code in `connectToEventStream` to use `.lines` computed value of `AsyncSequence` to produce a `AsyncLineSequence` instead of building a lines manually.

* - Reverter use of `lines` (it swallows newlines)
- Fiexed original issue I experienced with line 229 `while let newlineIndex = buffer.firstIndex(of: "\n") {` not handling "\r\n" properly
- Added unit test to test for "\r\n" scenario
- Simplified `end of event` test - `line` creation trims newline, added code trims carriage return. Only thing that should be left is an empty line

Tests/MCPTests/HTTPClientTransportTests.swift

@@ -411,6 +411,40 @@ import Testing
                 let expectedData = #"{"key":"value"}"#.data(using: .utf8)!
                 let receivedData = try await iterator.next()
 
+                #expect(receivedData == expectedData)
+            }
+            @Test("Receive Server-Sent Event (SSE) (CR-NL)", .httpClientTransportSetup)
+            func testReceiveSSE_CRNL() async throws {
+                let configuration = URLSessionConfiguration.ephemeral
+                configuration.protocolClasses = [MockURLProtocol.self]
+
+                let transport = HTTPClientTransport(
+                    endpoint: testEndpoint, configuration: configuration, streaming: true,
+                    logger: nil)
+
+                let eventString = "id: event1\r\ndata: {\"key\":\"value\"}\r\n\n"
+                let sseEventData = eventString.data(using: .utf8)!
+
+                await MockURLProtocol.requestHandlerStorage.setHandler {
+                    [testEndpoint] (request: URLRequest) in
+                    #expect(request.url == testEndpoint)
+                    #expect(request.httpMethod == "GET")
+                    #expect(request.value(forHTTPHeaderField: "Accept") == "text/event-stream")
+                    let response = HTTPURLResponse(
+                        url: testEndpoint, statusCode: 200, httpVersion: "HTTP/1.1",
+                        headerFields: ["Content-Type": "text/event-stream"])!
+                    return (response, sseEventData)
+                }
+
+                try await transport.connect()
+                try await Task.sleep(for: .milliseconds(100))
+
+                let stream = await transport.receive()
+                var iterator = stream.makeAsyncIterator()
+
+                let expectedData = #"{"key":"value"}"#.data(using: .utf8)!
+                let receivedData = try await iterator.next()
+
                 #expect(receivedData == expectedData)
             }
         #endif  // !canImport(FoundationNetworking)