feat(imap): integrate MIME into IMAP-SMTP

Feature/Sources/IMAP/IMAPError.swift

@@ -0,0 +1,17 @@
+/// ``IMAPClient`` throws `IMAPError`.
+public enum IMAPError: Error, CustomStringConvertible, Equatable {
+    case underlying(String)
+    case example
+
+    init(_ error: Error) {
+        self = error as? Self ?? .underlying(error.localizedDescription)
+    }
+
+    // MARK: CustomStringConvertible
+    public var description: String {
+        switch self {
+        case .underlying(let string): "Underlying: \(string)"
+        case .example: "Example"
+        }
+    }
+}

Feature/Sources/IMAP/LoggingHandler.swift

@@ -14,25 +14,20 @@ final class LoggingHandler: ChannelDuplexHandler, @unchecked Sendable {
     typealias OutboundIn = ByteBuffer
 
     func write(context: ChannelHandlerContext, data: NIOAny, promise: EventLoopPromise<Void>?) {
-        logger?.debug("\(self.unwrapOutboundIn(data).readableLogView(redactBase64Encoded: true))")
-        context.write(data, promise: promise)
+        logger?.debug("\(self.unwrapOutboundIn(data).stringValue)")
+        context.write(data, promise: promise)  // Handler only observes; pass unmodified data to next handler
     }
 
     func channelRead(context: ChannelHandlerContext, data: NIOAny) {
-        logger?.debug("\(self.unwrapInboundIn(data).readableLogView())")
-        context.fireChannelRead(data)
+        logger?.debug("\(self.unwrapInboundIn(data).stringValue)")
+        context.fireChannelRead(data)  // Pass unmodified data to next handler
     }
 }
 
-extension ByteBuffer {
-    // Format bytes as debug description; optionally redact user names and passwords
-    func readableLogView(redactBase64Encoded: Bool = false) -> String {
+private extension ByteBuffer {
+    var stringValue: String {
         let string: String = String(decoding: readableBytesView, as: UTF8.self).trimmingCharacters(in: .whitespacesAndNewlines)
-        guard let data: Data = Data(base64Encoded: string),
-            let string: String = String(data: data, encoding: .utf8)
-        else {
-            return string  // String not base64-encoded; return as is
-        }
-        return redactBase64Encoded ? "[redacted]" : string
+        // TODO: Redact IMAP credential
+        return string
     }
 }

Feature/Sources/IMAP/Message.swift

@@ -1,48 +1,45 @@
+import EmailAddress
 import Foundation
 import MIME
+import NIOIMAP
 
 /// [IMAP message attributes](https://www.ietf.org/rfc/rfc9051.html#section-2.3)
 public struct Message {
-    public enum Flag: String, CaseIterable, CustomStringConvertible, Sendable {
-        case seen = "\\Seen"
-        case answered = "\\Answered"
-        case flagged = "\\Flagged"
-        case deleted = "\\Deleted"
-        case draft = "\\Draft"
-        case forwarded = "$Forwarded"
-        case mdnSent = "$MDNSent"
-        case junk = "$Junk"
-        case notJunk = "$NotJunk"
-        case phishing = "$Phishing"
+    public typealias Flag = NIOIMAPCore.Flag
 
-        // MARK: CustomStringConvertible
-        public var description: String { rawValue }
-    }
-
-    public let isDeleted: Bool
-    public let folderID: Int
-    public let uid: String
-    public let subject: String
-    public let date: Date
+    public let body: Body
+    public let contentType: ContentType
     public let flags: [Flag]
-    public let senderList: String
-    public let toList: String
-    public let ccList: String
-    public let bccList: String
-    public let replyToList: String
-    public let attachmentCount: Int
-    public let internalDate: Date
+    public let folderID: Int
+    public let inReplyTo: String?
     public let messageID: String
-    public let previewType: String
-    public let preview: String
-    public let mimeType: String
-    public let normalizedSubjectHash: Int
-    public let isEmpty: Bool
-    public let isRead: Bool
-    public let isFlagged: Bool
-    public let isAnswered: Bool
-    public let isForwarded: Bool
-    public let messagePartID: Int
-    public let encryptionType: String
-    public let isNewMessage: Bool
+    public let replyTo: String?
+    public let size: Int
+    public let subject: String
+    public let uid: UID
+
+    public var isAnswered: Bool { flags.isAnswered }
+    public var isDeleted: Bool { flags.isDeleted }
+    public var isDraft: Bool { flags.isDraft }
+    public var isEmpty: Bool { body.isEmpty }
+    public var isFlagged: Bool { flags.isFlagged }
+    public var isForwarded: Bool { flags.isForwarded }
+    public var isSeen: Bool { flags.isSeen }
+}
+
+extension Message.Flag: @retroactive CustomStringConvertible {
+
+    // MARK: CustomStringConvertible
+    public var description: String { debugDescription }
+}
+
+public typealias UID = NIOIMAP.UID
+
+private extension [Message.Flag] {
+    var isAnswered: Bool { contains(.answered) }
+    var isDeleted: Bool { contains(.deleted) }
+    var isDraft: Bool { contains(.draft) }
+    var isFlagged: Bool { contains(.flagged) }
+    var isForwarded: Bool { contains(.keyword(.forwarded)) }
+    var isSeen: Bool { contains(.seen) }
 }

Feature/Sources/IMAP/Server.swift

@@ -7,11 +7,11 @@ public struct Server: Equatable, Sendable {
     public let port: Int
 
     public init(
-        _ connectionSecurity: ConnectionSecurity = .startTLS,
+        _ connectionSecurity: ConnectionSecurity = .tls,
         hostname: String,
         username: String,
         password: String,
-        port: Int = 143  // 993
+        port: Int = 993
     ) {
         self.connectionSecurity = connectionSecurity
         self.hostname = hostname

Feature/Sources/MIME/Body.swift

@@ -1,7 +1,7 @@
 import Foundation
 
 /// Multipart body element described in [RFC 2045](https://www.rfc-editor.org/rfc/rfc2045#section-2.6)
-public struct Body: CustomStringConvertible, RawRepresentable {
+public struct Body: CustomStringConvertible, RawRepresentable, Sendable {
     public let contentTransferEncoding: ContentTransferEncoding?
     public let contentType: ContentType  // Body encoding is always ASCII
     public let parts: [Part]
@@ -85,3 +85,16 @@ public struct Body: CustomStringConvertible, RawRepresentable {
         try? self.init(rawValue)
     }
 }
+
+extension Body {
+    public static var empty: Self {
+        try! Self(
+            parts: [
+                try! Part(data: "".data(using: .ascii)!, contentType: .text(.plain, .ascii))
+            ], contentType: .text(.plain, .ascii))
+    }
+
+    public var isEmpty: Bool {
+        parts.count == 1 && (String(data: parts[0].data, encoding: .ascii) ?? "").isEmpty
+    }
+}

Feature/Sources/MIME/CharacterSet.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 /// Character encoding described in [RFC 2045](https://www.rfc-editor.org/rfc/rfc2045#section-2.2)
 public struct CharacterSet: CustomStringConvertible, Equatable, RawRepresentable, Sendable {
     public static var ascii: Self { try! Self("US-ASCII") }  // Default character encoding

Feature/Sources/MIME/ContentTransferEncoding.swift

@@ -1,5 +1,5 @@
 /// Multipart email body must be ASCII in transfer. Parts encoded by this library use `base64` transfer encoding exclusively, but we expect to decode parts in any of the enumerated encodings, especially `quotedPrintable`.
-public enum ContentTransferEncoding: String, CaseIterable, CustomStringConvertible, RawRepresentable {
+public enum ContentTransferEncoding: String, CaseIterable, CustomStringConvertible, RawRepresentable, Sendable {
     case ascii = "7bit"
     case base64
     case binary

Feature/Sources/MIME/Part.swift

@@ -1,7 +1,7 @@
 import Foundation
 
 /// MIME part described in [RFC 2045](https://www.rfc-editor.org/rfc/rfc2045#section-2.5)
-public struct Part: CustomStringConvertible, RawRepresentable {
+public struct Part: CustomStringConvertible, RawRepresentable, Sendable {
 
     /// Instruct mail client to display decoded body part inline, in message, or link as an attachment. Optionally include file name and other metadata for source file.
     public let contentDisposition: ContentDisposition?

Feature/Sources/MIME/String.swift

@@ -83,8 +83,8 @@ extension String {
     }
 }
 
+public var crlf: String { .crlf }
+
 extension [Character] {
     static var quotes: Self { ["\"", "'"] }
 }
-
-var crlf: String { .crlf }

Feature/Sources/MIME/UUID.swift

@@ -6,7 +6,7 @@ extension UUID {
         try! Boundary("\(prefix?.ascii ?? "")\(uuidString(segments, separator: separator))\(suffix?.ascii ?? "")")
     }
 
-    func uuidString(_ segments: Int, separator: String = .separator) -> String {
+    public func uuidString(_ segments: Int, separator: String = .separator) -> String {
         uuidString
             .components(separatedBy: String.separator)
             .prefix(max(segments, 1))

Feature/Sources/SMTP/Email.swift

@@ -1,34 +1,18 @@
 import EmailAddress
 import Foundation
 import MIME
-import UniformTypeIdentifiers
 
 /// ``SMTPClient`` sends `Email`.
 public struct Email: Identifiable, Sendable {
-    public struct Part {
-        public let data: Data
-        public let contentType: String
-    }
-
     public let sender: EmailAddress
     public let recipients: [EmailAddress]
     public let copied: [EmailAddress]
     public let blindCopied: [EmailAddress]
     public let subject: String
     public let date: Date
-    public let parts: [Data]
-
-    public var body: Data {
-        var data: Data = Data()
-        for part in parts {
-            data.append(line.data(using: .utf8)!)
-            data.append(part)
-        }
-        data.append(line.data(using: .utf8)!)
-        return data
-    }
+    public let body: Body
 
-    public var contentType: String { "text/plain; charset=\"UTF-8\"" }
+    public var contentType: MIME.ContentType { body.contentType }
 
     public var messageID: String {
         // Format: https://www.jwz.org/doc/mid.html
@@ -46,7 +30,7 @@ public struct Email: Identifiable, Sendable {
         blindCopied: [EmailAddress] = [],
         subject: String = "",
         date: Date = Date(),
-        body parts: [Data] = [],
+        body: Body = .empty,
         id: UUID = UUID()
     ) {
         self.sender = sender
@@ -55,26 +39,12 @@ public struct Email: Identifiable, Sendable {
         self.blindCopied = blindCopied
         self.subject = subject
         self.date = date
-        self.parts = parts
+        self.body = body
         self.id = id
     }
 
-    var iso8601Date: String { ISO8601DateFormatter().string(from: date) }
     var allRecipients: [EmailAddress] { recipients + copied + blindCopied }
-    var dataBoundary: String { "\(id.uuidString(4))_part" }
 
     // MARK: Identifiable
     public let id: UUID
 }
-
-extension UUID {
-    func uuidString(_ segments: Int) -> String {
-        uuidString.components(separatedBy: "-").prefix(max(segments, 0)).joined(separator: "-")
-    }
-}
-
-extension String {
-    static var line: Self { "\r\n" }
-}
-
-var line: String { .line }

Feature/Sources/SMTP/LoggingHandler.swift

@@ -14,25 +14,29 @@ final class LoggingHandler: ChannelDuplexHandler, @unchecked Sendable {
     typealias OutboundIn = ByteBuffer
 
     func write(context: ChannelHandlerContext, data: NIOAny, promise: EventLoopPromise<Void>?) {
-        logger?.debug("\(self.unwrapOutboundIn(data).readableLogView(redactBase64Encoded: true))")
-        context.write(data, promise: promise)
+        logger?.debug("\(self.unwrapOutboundIn(data).stringValue)")
+        context.write(data, promise: promise)  // Handler only observes; pass unmodified data to next handler
     }
 
     func channelRead(context: ChannelHandlerContext, data: NIOAny) {
-        logger?.debug("\(self.unwrapInboundIn(data).readableLogView())")
-        context.fireChannelRead(data)
+        logger?.debug("\(self.unwrapInboundIn(data).stringValue)")
+        context.fireChannelRead(data)  // Pass unmodified data to next handler
     }
 }
 
 extension ByteBuffer {
-    // Format bytes as debug description; optionally redact user names and passwords
-    func readableLogView(redactBase64Encoded: Bool = false) -> String {
+    var stringValue: String {
         let string: String = String(decoding: readableBytesView, as: UTF8.self).trimmingCharacters(in: .whitespacesAndNewlines)
+        // Deocde base64-encoded credentials
         guard let data: Data = Data(base64Encoded: string),
             let string: String = String(data: data, encoding: .utf8)
         else {
-            return string  // String not base64-encoded; return as is
+            return string
         }
-        return redactBase64Encoded ? "[redacted]" : string
+        #if DEBUG
+        return string
+        #else
+        return String(repeating: "•", count: string.count)  // Redact decoded SMTP credential
+        #endif
     }
 }

Feature/Sources/SMTP/RequestEncoder.swift

@@ -1,5 +1,6 @@
 import EmailAddress
 import Foundation
+import MIME
 import NIOCore
 
 enum Request {
@@ -37,18 +38,16 @@ struct RequestEncoder: MessageToByteEncoder {
         case .data:
             out.writeString("DATA")
         case .transferData(let email):
-            out.writeString("From: \(email.sender)\(line)")
-            out.writeString("To: \(email.recipients.map { $0.description }.joined(separator: " "))\(line)")
-            out.writeString("Date: \(email.iso8601Date)\(line)")  // "EEE, dd MMM yyyy HH:mm:ss Z"
-            out.writeString("Message-ID: \(email.messageID)\(line)")
-            out.writeString("Subject: \(email.subject)\(line)")
-            // out.writeString("MIME-Version: 1.0\(line)")
-            out.writeString("Content-Type: \(email.contentType)\(line)")
-            out.writeBytes(email.body)
-            out.writeString("\(line).")
+            out.writeString("From: \(email.sender)\(crlf)")
+            out.writeString("To: \(email.recipients.map { $0.description }.joined(separator: " "))\(crlf)")
+            out.writeString("Date: \(email.date.rfc822Format())\(crlf)")
+            out.writeString("Message-ID: \(email.messageID)\(crlf)")
+            out.writeString("Subject: \(email.subject)\(crlf)")
+            out.writeBytes(email.body.rawValue)
+            out.writeString("\(crlf).")
         case .quit:
             out.writeString("QUIT")
         }
-        out.writeString(line)
+        out.writeString(crlf)
     }
 }

Feature/Sources/SMTP/ResponseHandler.swift

@@ -1,4 +1,3 @@
-import Foundation
 import NIOCore
 
 enum Response {

Feature/Sources/SMTP/SMTPClient.swift

@@ -12,7 +12,7 @@ public struct SMTPClient {
 
     public init(
         _ server: Server,
-        logger: Logger? = Logger(subsystem: "net.thunderbird.ios", category: "SMTP")
+        logger: Logger? = Logger(subsystem: "net.thunderbird", category: "SMTP")
     ) {
         group = NIOTSEventLoopGroup(loopCount: 1, defaultQoS: .utility)
         self.server = server