add fetchFullMessage, fetchSection to IMAPClient for MIME attachment retrieval

Packages/MagnumOpusCore/Sources/IMAPClient/IMAPClient.swift

@@ -93,6 +93,65 @@ public actor IMAPClient: IMAPClientProtocol {
 		return parseFlagResponses(responses)
 	}
 
+	public func fetchFullMessage(uid: Int) async throws -> String {
+		guard var runner else { throw IMAPError.notConnected }
+		let uidValue = UID(rawValue: UInt32(uid))
+		let range = MessageIdentifierRange<UID>(uidValue...uidValue)
+		let set = MessageIdentifierSetNonEmpty<UID>(range: range)
+		let responses = try await runner.run(.uidFetch(
+			.set(set),
+			[.bodySection(peek: true, SectionSpecifier(kind: .complete), nil)],
+			[]
+		))
+		self.runner = runner
+		return parseFullMessageResponse(responses)
+	}
+
+	public func fetchSection(uid: Int, mailbox: String, section: String) async throws -> Data {
+		guard var runner else { throw IMAPError.notConnected }
+
+		// Select the mailbox first
+		let selectResponses = try await runner.run(.select(MailboxName(ByteBuffer(string: mailbox))))
+		self.runner = runner
+		guard selectResponses.contains(where: { isOKTagged($0) }) else {
+			throw IMAPError.unexpectedResponse("SELECT \(mailbox) failed")
+		}
+
+		let uidValue = UID(rawValue: UInt32(uid))
+		let range = MessageIdentifierRange<UID>(uidValue...uidValue)
+		let set = MessageIdentifierSetNonEmpty<UID>(range: range)
+
+		// Parse section path into SectionSpecifier.Part
+		let sectionParts = section.split(separator: ".").compactMap { Int($0) }
+		let part = SectionSpecifier.Part(sectionParts)
+		let spec = SectionSpecifier(part: part)
+
+		let responses = try await runner.run(.uidFetch(
+			.set(set),
+			[.bodySection(peek: true, spec, nil)],
+			[]
+		))
+		self.runner = runner
+
+		var bodyBuffer = ByteBuffer()
+		for response in responses {
+			if case .fetch(let fetchResponse) = response {
+				if case .streamingBytes(let bytes) = fetchResponse {
+					var mutableBytes = bytes
+					bodyBuffer.writeBuffer(&mutableBytes)
+				}
+			}
+		}
+
+		// The section content may be base64 encoded — decode it
+		let raw = String(buffer: bodyBuffer)
+		let cleaned = raw.filter { !$0.isWhitespace }
+		if let decoded = Data(base64Encoded: cleaned) {
+			return decoded
+		}
+		return Data(bodyBuffer.readableBytesView)
+	}
+
 	public func fetchBody(uid: Int) async throws -> (text: String?, html: String?) {
 		guard var runner else { throw IMAPError.notConnected }
 		let uidValue = UID(rawValue: UInt32(uid))
@@ -456,6 +515,22 @@ public actor IMAPClient: IMAPClientProtocol {
 		return results
 	}
 
+	private func parseFullMessageResponse(_ responses: [Response]) -> String {
+		var bodyBuffer = ByteBuffer()
+		for response in responses {
+			if case .fetch(let fetchResponse) = response {
+				switch fetchResponse {
+				case .streamingBytes(let bytes):
+					var mutableBytes = bytes
+					bodyBuffer.writeBuffer(&mutableBytes)
+				default:
+					break
+				}
+			}
+		}
+		return String(buffer: bodyBuffer)
+	}
+
 	private func parseBodyResponse(_ responses: [Response]) -> (text: String?, html: String?) {
 		var bodyBuffer = ByteBuffer()
 

Packages/MagnumOpusCore/Sources/IMAPClient/IMAPClientProtocol.swift

@@ -9,6 +9,10 @@ public protocol IMAPClientProtocol: Sendable {
 	func fetchFlags(uids: ClosedRange<Int>) async throws -> [UIDFlagsPair]
 	func fetchBody(uid: Int) async throws -> (text: String?, html: String?)
 
+	// v0.5 attachment/MIME operations
+	func fetchFullMessage(uid: Int) async throws -> String
+	func fetchSection(uid: Int, mailbox: String, section: String) async throws -> Data
+
 	// v0.3 write operations
 	func storeFlags(uid: Int, mailbox: String, add: [String], remove: [String]) async throws
 	func moveMessage(uid: Int, from: String, to: String) async throws