add SMTPClient module: connection layer, message formatter, public API, tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-14 05:25:03 +01:00
parent 427f197bb3
commit 54ce92e280
9 changed files with 695 additions and 1 deletions
@@ -0,0 +1,92 @@
+import NIO
+
+/// NIO handler that parses SMTP line-based responses.
+/// SMTP response format: `<3-digit code><separator><text>\r\n`
+/// Separator `-` means continuation, space means final line.
+final class SMTPResponseHandler: ChannelInboundHandler, @unchecked Sendable {
+	typealias InboundIn = ByteBuffer
+
+	private var stringBuffer = ""
+	private var responseLines: [String] = []
+	private var responseCode: Int?
+	private var continuation: CheckedContinuation<SMTPResponse, Error>?
+	private var greetingContinuation: CheckedContinuation<SMTPResponse, Error>?
+
+	func channelRead(context: ChannelHandlerContext, data: NIOAny) {
+		var buffer = unwrapInboundIn(data)
+		guard let received = buffer.readString(length: buffer.readableBytes) else { return }
+		stringBuffer.append(received)
+
+		while let lineEnd = stringBuffer.range(of: "\r\n") {
+			let line = String(stringBuffer[stringBuffer.startIndex..<lineEnd.lowerBound])
+			stringBuffer.removeSubrange(stringBuffer.startIndex..<lineEnd.upperBound)
+			processLine(line)
+		}
+	}
+
+	private func processLine(_ line: String) {
+		guard line.count >= 3,
+			  let code = Int(line.prefix(3))
+		else { return }
+
+		// Extract text after the code + separator character
+		let text: String
+		if line.count > 4 {
+			text = String(line.dropFirst(4))
+		} else {
+			text = ""
+		}
+
+		responseLines.append(text)
+
+		if responseCode == nil {
+			responseCode = code
+		}
+
+		// Separator is at index 3: `-` for continuation, space for final
+		let isFinal: Bool
+		if line.count > 3 {
+			isFinal = line[line.index(line.startIndex, offsetBy: 3)] == " "
+		} else {
+			isFinal = true
+		}
+
+		if isFinal {
+			let response = SMTPResponse(code: code, lines: responseLines)
+			responseLines = []
+			responseCode = nil
+
+			if let cont = greetingContinuation {
+				greetingContinuation = nil
+				cont.resume(returning: response)
+			} else if let cont = continuation {
+				continuation = nil
+				cont.resume(returning: response)
+			}
+		}
+	}
+
+	func errorCaught(context: ChannelHandlerContext, error: Error) {
+		if let cont = continuation {
+			continuation = nil
+			cont.resume(throwing: error)
+		}
+		if let cont = greetingContinuation {
+			greetingContinuation = nil
+			cont.resume(throwing: error)
+		}
+		context.close(promise: nil)
+	}
+
+	func waitForGreeting() async throws -> SMTPResponse {
+		try await withCheckedThrowingContinuation { cont in
+			greetingContinuation = cont
+		}
+	}
+
+	func waitForResponse() async throws -> SMTPResponse {
+		try await withCheckedThrowingContinuation { cont in
+			continuation = cont
+		}
+	}
+}