Misc. Fixes

MikeMail/IMAPClient.swift

@@ -178,24 +178,58 @@ final class IMAPClient {
         return result
     }
 
-    func inventory(folder: MailFolder, writable: Bool = false) async throws -> MailboxInventory {
-        let examined = try await command("\(writable ? "SELECT" : "EXAMINE") \(Self.quote(folder.path))")
+    static func highestModSequence(from lines: [String]) -> UInt64? {
+        for line in lines {
+            if line.uppercased().contains("[NOMODSEQ]") { return nil }
+        }
+        for line in lines {
+            guard let start = line.range(of: "[HIGHESTMODSEQ ", options: .caseInsensitive),
+                  let end = line[start.upperBound...].firstIndex(of: "]"),
+                  let value = UInt64(line[start.upperBound..<end]), value > 0 else { continue }
+            return value
+        }
+        return nil
+    }
+
+    func inventory(folder: MailFolder, writable: Bool = false,
+                   previous: MailboxInventory? = nil, supportsCONDSTORE: Bool = false) async throws -> MailboxInventory {
+        try await Self.fetchInventory(folder: folder, writable: writable, previous: previous,
+            supportsCONDSTORE: supportsCONDSTORE, command: command)
+    }
+
+    static func fetchInventory(folder: MailFolder, writable: Bool = false,
+                               previous: MailboxInventory? = nil, supportsCONDSTORE: Bool = false,
+                               command: (String) async throws -> Response) async throws -> MailboxInventory {
+        let option = supportsCONDSTORE ? " (CONDSTORE)" : ""
+        let examined = try await command("\(writable ? "SELECT" : "EXAMINE") \(Self.quote(folder.path))\(option)")
         let validity = try Self.uidValidity(from: examined.lines)
+        // Keep the watermark from BEFORE fetching changes; later changes must be replayed next time.
+        let modSequence = supportsCONDSTORE ? Self.highestModSequence(from: examined.lines) : nil
         let search = try await command("UID SEARCH ALL")
         guard let line = search.lines.first(where: { $0.uppercased().hasPrefix("* SEARCH") }) else {
             throw MailError.message("Unvollständige IMAP-Bestandsliste.")
         }
-        let ids = line.split(separator: " ").dropFirst(2).compactMap { UInt64($0) }
-        var flags: [UInt64: [String]] = [:]
-        for start in stride(from: 0, to: ids.count, by: 200) {
-            let batch = ids[start..<min(start + 200, ids.count)].map(String.init).joined(separator: ",")
-            let fetched = try await command("UID FETCH \(batch) (UID FLAGS)")
-            flags.merge(try Self.parseFlags(fetched.lines)) { _, new in new }
+        let ids = Set(line.split(separator: " ").dropFirst(2).compactMap { UInt64($0) })
+        let reusable = previous?.canReuseFlags(validity: validity, highestModSequence: modSequence) == true
+        var flags = reusable ? (previous?.flags ?? [:]).filter { ids.contains($0.key) } : [:]
+        if !ids.isEmpty {
+            if reusable, let previousSequence = previous?.highestModSequence {
+                // Even an unchanged mod-sequence needs SEARCH above: CONDSTORE alone
+                // does not provide QRESYNC's VANISHED deletion history.
+                if modSequence != previousSequence || Set(flags.keys) != ids {
+                    let fetched = try await command("UID FETCH 1:* (UID FLAGS) (CHANGEDSINCE \(previousSequence))")
+                    flags.merge(try Self.parseFlags(fetched.lines)) { _, new in new }
+                }
+            } else {
+                // A UID range needs one round trip rather than one per 200 messages.
+                let fetched = try await command("UID FETCH 1:* (UID FLAGS)")
+                flags = try Self.parseFlags(fetched.lines)
+            }
         }
-        guard Set(flags.keys) == Set(ids) else {
+        guard Set(flags.keys) == ids else {
             throw MailError.message("Der Ordner hat sich während des Abgleichs verändert. Bitte erneut abrufen.")
         }
-        return MailboxInventory(validity: validity, flags: flags)
+        return MailboxInventory(validity: validity, flags: flags, highestModSequence: modSequence)
     }
 
     func rawMessage(uid: UInt64) async throws -> Data {
@@ -275,17 +309,48 @@ final class IMAPClient {
 
     /// UID EXPUNGE must never be replaced by EXPUNGE: other clients may have marked unrelated mail.
     func remove(uids: [UInt64]) async throws {
+        try await Self.remove(uids: uids, command: command, onRemoved: { _ in })
+    }
+
+    private static func remove(uids: [UInt64], command: (String) async throws -> Response,
+                               onRemoved: ([UInt64]) throws -> Void) async throws {
         guard !uids.isEmpty else { return }
-        guard try await capabilities().contains("UIDPLUS") else {
+        let response = try await command("CAPABILITY")
+        let capabilities = Set(response.lines.filter { $0.uppercased().hasPrefix("* CAPABILITY ") }
+            .flatMap { $0.uppercased().split(separator: " ").dropFirst(2).map(String.init) })
+        guard capabilities.contains("UIDPLUS") else {
             throw MailError.message("Der Server unterstützt kein gezieltes Löschen (UIDPLUS). Es wurden keine Mails gelöscht.")
         }
         for start in stride(from: 0, to: uids.count, by: 200) {
             let batch = uids[start..<min(start + 200, uids.count)].map(String.init).joined(separator: ",")
             _ = try await command("UID STORE \(batch) +FLAGS.SILENT (\\Deleted)")
             _ = try await command("UID EXPUNGE \(batch)")
+            try onRemoved(Array(uids[start..<min(start + 200, uids.count)]))
         }
     }
 
+    func emptyTrash(folder: MailFolder,
+                    onRemoved: (String, [UInt64]) throws -> Void) async throws -> String {
+        try await Self.emptyTrash(folder: folder, command: command, onRemoved: onRemoved)
+    }
+
+    /// Only enumerate the selected trash folder; bodies and flags are unnecessary.
+    static func emptyTrash(folder: MailFolder, command: (String) async throws -> Response,
+                           onRemoved: (String, [UInt64]) throws -> Void) async throws -> String {
+        guard folder.isTrash else { throw MailError.message("Bitte einen Papierkorb auswählen.") }
+        let selected = try await command("SELECT \(Self.quote(folder.path))")
+        let validity = try Self.uidValidity(from: selected.lines)
+        let search = try await command("UID SEARCH ALL")
+        guard let line = search.lines.first(where: { $0.uppercased().hasPrefix("* SEARCH") }) else {
+            throw MailError.message("Unvollständige IMAP-Bestandsliste.")
+        }
+        let uids = line.split(separator: " ").dropFirst(2).compactMap { UInt64($0) }.sorted()
+        try await remove(uids: uids, command: command) { removed in
+            try onRemoved(validity, removed)
+        }
+        return validity
+    }
+
     @discardableResult
     func append(_ message: Data, path: String, flags: [String]) async throws -> AssignedUID? {
         let allowed = ["\\Seen", "\\Answered", "\\Flagged", "\\Draft"]
@@ -333,11 +398,64 @@ final class IMAPClient {
         return ["EXISTS", "EXPUNGE", "FETCH"].contains(String(parts[2]))
     }
 
+    enum IdleChange: Equatable {
+        case refresh
+        case removed(validity: String, uid: UInt64)
+        case flags(validity: String, uid: UInt64, flags: [String])
+    }
+
+    /// EXPUNGE uses sequence numbers, which shift after every removal.
+    struct IdleMailbox {
+        let validity: String
+        var uids: [UInt64?]
+
+        mutating func receive(_ line: String) -> IdleChange? {
+            let parts = line.uppercased().split(separator: " ")
+            guard parts.count >= 3, parts[0] == "*", let number = Int(parts[1]), number >= 0 else { return nil }
+            switch parts[2] {
+            case "EXISTS":
+                guard number != uids.count else { return nil }
+                if number > uids.count {
+                    uids.append(contentsOf: repeatElement(nil, count: number - uids.count))
+                } else {
+                    uids = Array(repeating: nil, count: number)
+                }
+                return .refresh
+            case "EXPUNGE":
+                guard number > 0, number <= uids.count else { return .refresh }
+                guard let uid = uids.remove(at: number - 1) else { return .refresh }
+                return .removed(validity: validity, uid: uid)
+            case "FETCH":
+                guard number > 0, number <= uids.count else { return .refresh }
+                // Servers may omit UID in unsolicited FETCH responses.
+                let flags = try? IMAPClient.parseFlags([line + " UID " + String(uids[number - 1] ?? 0)])
+                guard let (uid, values) = flags?.first, uid > 0 else { return .refresh }
+                uids[number - 1] = uid
+                return .flags(validity: validity, uid: uid, flags: values)
+            default:
+                return nil
+            }
+        }
+    }
+
     /// This connection is reserved for IDLE; normal commands use separate sessions.
     /// Renew before the RFC 2177 inactivity limit, with a bounded DONE response wait.
     func idleInbox(renewAfterSeconds: Int = 25 * 60,
-                   onReady: () -> Void, onChange: () -> Void) async throws {
-        _ = try await command("EXAMINE \"INBOX\"")
+                   onReady: () -> Void, onChange: (IdleChange) -> Void) async throws {
+        let examined = try await command("EXAMINE \"INBOX\"")
+        let validity = try Self.uidValidity(from: examined.lines)
+        let search = try await command("UID SEARCH ALL")
+        guard let listing = search.lines.first(where: { $0.uppercased().hasPrefix("* SEARCH") }) else {
+            throw MailError.message("Unvollständige IMAP-Bestandsliste.")
+        }
+        var mailbox = IdleMailbox(validity: validity,
+            uids: listing.split(separator: " ").dropFirst(2).compactMap { UInt64($0) }.sorted().map { Optional($0) })
+        // SEARCH is the sequence baseline; subsequent unsolicited responses shift it.
+        if let index = search.lines.firstIndex(of: listing) {
+            for line in search.lines.dropFirst(index + 1) {
+                if let change = mailbox.receive(line) { onChange(change) }
+            }
+        }
         sequence += 1
         let tag = "M\(sequence)"
         try await connection.line("\(tag) IDLE")
@@ -347,6 +465,7 @@ final class IMAPClient {
             guard line.hasPrefix("*"), !line.uppercased().hasPrefix("* BYE") else {
                 throw MailError.message("IMAP IDLE wurde nicht akzeptiert: \(line)")
             }
+            if let change = mailbox.receive(line) { onChange(change) }
         }
         onReady()
         let renewal = Task {
@@ -373,7 +492,7 @@ final class IMAPClient {
             if line.uppercased().hasPrefix("* BYE") {
                 throw MailError.message("IMAP IDLE: Verbindung beendet.")
             }
-            if Self.isMailboxChange(line) { onChange() }
+            if let change = mailbox.receive(line) { onChange(change) }
         }
     }
 }

MikeMail/MailArchive.swift

@@ -43,9 +43,16 @@ struct ArchiveConfiguration: Codable {
     var recipients: [String]
 }
 
-struct MailboxInventory {
+struct MailboxInventory: Codable, Equatable {
     let validity: String
     let flags: [UInt64: [String]]
+    var highestModSequence: UInt64? = nil
+
+    func canReuseFlags(validity: String, highestModSequence: UInt64?) -> Bool {
+        guard self.validity == validity, let previous = self.highestModSequence,
+              let current = highestModSequence else { return false }
+        return previous > 0 && current >= previous
+    }
 }
 
 struct ArchiveMailRecord: Codable {
@@ -160,15 +167,60 @@ final class MailArchive {
         return failures
     }
 
+    /// The server snapshot stays separate from local mutations and survives relaunches.
+    func syncInventory(folderID: String) throws -> MailboxInventory? {
+        let key = "inventory:" + folderID
+        let descriptor = FetchDescriptor<MailArchiveSchema.ArchiveState>(predicate: #Predicate { $0.key == key })
+        guard let state = try context.fetch(descriptor).first else { return nil }
+        // A missing/obsolete cache is recoverable through a full metadata fetch.
+        return try? JSONDecoder().decode(MailboxInventory.self, from: state.payload)
+    }
+
+    private func cacheInventory(folderID: String, inventory: MailboxInventory) throws {
+        let key = "inventory:" + folderID
+        let payload = try JSONEncoder().encode(inventory)
+        if let state = try context.fetch(FetchDescriptor<MailArchiveSchema.ArchiveState>(
+            predicate: #Predicate { $0.key == key })).first {
+            if state.payload != payload { state.payload = payload }
+        } else {
+            context.insert(MailArchiveSchema.ArchiveState(key: key, payload: payload))
+        }
+    }
+
     /// Reconcile only after a complete server inventory. Keep removed objects for future backups.
-    func reconcile(folderID: String, inventory: MailboxInventory) throws {
+    @discardableResult
+    func reconcile(folderID: String, inventory: MailboxInventory) throws -> Bool {
         do {
+            var changed = false
             for row in try rows(folderID: folderID) {
                 let flags = UInt64(row.uid).flatMap { inventory.flags[$0] }
-                row.present = row.validity == inventory.validity && flags != nil
-                if let flags, row.present { row.flags = flags }
+                let present = row.validity == inventory.validity && flags != nil
+                if row.present != present {
+                    row.present = present
+                    changed = true
+                }
+                if let flags, present, Set(row.flags) != Set(flags) {
+                    row.flags = flags
+                    changed = true
+                }
             }
-            try context.save()
+            if try syncInventory(folderID: folderID) != inventory {
+                try cacheInventory(folderID: folderID, inventory: inventory)
+            }
+            if context.hasChanges { try context.save() }
+            return changed
+        } catch { context.rollback(); throw error }
+    }
+
+    /// Commit each confirmed deletion batch, even if a later server request fails.
+    func applyRemovals(folderID: String, validity: String, uids: [UInt64]) throws {
+        let removed = Set(uids.map(String.init))
+        do {
+            for row in try rows(folderID: folderID)
+                where row.validity == validity && removed.contains(row.uid) && row.present {
+                row.present = false
+            }
+            if context.hasChanges { try context.save() }
         } catch { context.rollback(); throw error }
     }
 

MikeMail/MailIdleMonitor.swift

@@ -8,12 +8,12 @@ final class MailIdleMonitor {
     private var accounts: [UUID: MailAccount] = [:]
     private var pathMonitor: NWPathMonitor?
     private var wakeTask: Task<Void, Never>?
-    private var changed: ((UUID) -> Void)?
+    private var changed: ((UUID, IMAPClient.IdleChange) -> Void)?
     private var authenticationFailed: ((UUID) -> Void)?
     private var report: ((UUID, String) -> Void)?
 
     func configure(accounts values: [MailAccount], enabled: Bool,
-                   changed: @escaping (UUID) -> Void, report: @escaping (UUID, String) -> Void,
+                   changed: @escaping (UUID, IMAPClient.IdleChange) -> Void, report: @escaping (UUID, String) -> Void,
                    authenticationFailed: @escaping (UUID) -> Void) {
         self.authenticationFailed = authenticationFailed
         self.changed = changed
@@ -76,9 +76,9 @@ final class MailIdleMonitor {
                                 retrySeconds = 2
                                 report?(account.id, "Sofortempfang aktiv")
                                 // Reconcile the gap before the listener became ready, also after reconnects.
-                                changed?(account.id)
-                            } onChange: {
-                                changed?(account.id)
+                                changed?(account.id, .refresh)
+                            } onChange: { change in
+                                changed?(account.id, change)
                             }
                         }
                     } onCancel: {

MikeMail/MailStore.swift

@@ -24,6 +24,7 @@ final class MailStore {
     private var didStart = false
     private let idleMonitor = MailIdleMonitor()
     private var pendingIdleAccounts: Set<UUID> = []
+    private var pendingIdleChanges: [(UUID, IMAPClient.IdleChange)] = []
     private var idleRefreshGeneration = UUID()
     private var idleRefreshTask: Task<Void, Never>?
     var idleStatuses: [UUID: String] = [:]
@@ -155,6 +156,7 @@ final class MailStore {
         defer { isBusy = false }
         var failures: [String] = []
         var newInboxMessages: [NewMailNotification] = []
+        var changedFolderIDs: Set<String> = []
         do {
             let archive = try storage()
             for account in accounts where accountID == nil || account.id == accountID {
@@ -163,6 +165,7 @@ final class MailStore {
                     defer { client.close() }
                     status = "\(account.email): Verbindung wird aufgebaut …"
                     try await client.login(account: account, password: PasswordStore.password(for: account.id))
+                    let supportsCONDSTORE = try await client.capabilities().contains("CONDSTORE")
                     var discovered = inboxOnly ? (folders[account.id] ?? []) : try await client.folders(accountID: account.id)
                     let pending = inboxOnly ? [] : try archive.pendingSent(accountID: account.id)
                     if !pending.isEmpty {
@@ -192,13 +195,17 @@ final class MailStore {
                     try archive.saveConfiguration(ArchiveConfiguration(accounts: accounts, folders: updated, recipients: recipientHistory))
                     let discoveredIDs = Set(allFolders(discovered).map(\.id))
                     for removed in allFolders(folders[account.id] ?? []) where !discoveredIDs.contains(removed.id) {
-                        try archive.reconcile(folderID: removed.id, inventory: MailboxInventory(validity: "", flags: [:]))
+                        if try archive.reconcile(folderID: removed.id, inventory: MailboxInventory(validity: "", flags: [:])) {
+                            changedFolderIDs.insert(removed.id)
+                        }
                     }
                     folders = updated
                     for folder in allFolders(discovered) where folder.selectable && (!inboxOnly || folder.isInbox) {
                         do {
                             status = "\(folder.name): Änderungen prüfen …"
-                            let inventory = try await client.inventory(folder: folder)
+                            let previous = try archive.syncInventory(folderID: folder.id)
+                            let inventory = try await client.inventory(folder: folder, previous: previous,
+                                supportsCONDSTORE: supportsCONDSTORE)
                             let known = try archive.knownUIDs(folderID: folder.id, validity: inventory.validity)
                             let missing = Set(inventory.flags.keys).subtracting(known).sorted(by: >)
                             for (index, uid) in missing.enumerated() {
@@ -215,8 +222,8 @@ final class MailStore {
                                 try archive.store(raw: raw, folderID: folder.id, validity: inventory.validity,
                                     uid: String(uid), flags: inventory.flags[uid] ?? [], visible: false)
                             }
-                            try archive.reconcile(folderID: folder.id, inventory: inventory)
-                            if selectedFolderID == folder.id { try display(folderID: folder.id) }
+                            let changed = try archive.reconcile(folderID: folder.id, inventory: inventory)
+                            if changed || !missing.isEmpty { changedFolderIDs.insert(folder.id) }
                         } catch { failures.append("\(account.email) / \(folder.name): \(error.localizedDescription)") }
                     }
                 } catch {
@@ -225,9 +232,14 @@ final class MailStore {
                 }
             }
             unreadCounts = try archive.unreadCounts()
-            archiveRevision += 1
+            if !changedFolderIDs.isEmpty { archiveRevision += 1 }
+            let previousSelection = selectedFolderID
             if let resolvedFolderID = mailboxID(for: folderID) { selectedFolderID = resolvedFolderID }
-            if let selectedFolderID { try display(folderID: selectedFolderID) }
+            if let selectedFolderID,
+               previousSelection != selectedFolderID || changedFolderIDs.contains(selectedFolderID)
+                || (selectedFolderID.hasPrefix("unified:") && !changedFolderIDs.isEmpty) {
+                try display(folderID: selectedFolderID)
+            }
             await MailNotifications.postNewMail(
                 newInboxMessages,
                 badgeCount: totalUnreadCount
@@ -612,12 +624,16 @@ final class MailStore {
         let targets = folderID == "unified:trash"
             ? accounts.flatMap { allFolders(folders[$0.id] ?? []) }.filter(\.isTrash)
             : [folder(id: folderID)].compactMap { $0 }.filter(\.isTrash)
-        await mutate {
+        await mutate(refreshAfter: false) {
             for folder in targets {
                 let client = try await self.client(for: folder.accountID)
                 defer { client.close() }
-                let inventory = try await client.inventory(folder: folder, writable: true)
-                try await client.remove(uids: Array(inventory.flags.keys))
+                let validity = try await client.emptyTrash(folder: folder) { validity, removed in
+                    try self.storage().applyRemovals(folderID: folder.id, validity: validity, uids: removed)
+                }
+                // Also retire stale local entries that were already absent on the server.
+                try self.storage().reconcile(folderID: folder.id,
+                    inventory: MailboxInventory(validity: validity, flags: [:]))
             }
         }
     }
@@ -711,8 +727,8 @@ final class MailStore {
 
     func configureIdle() {
         idleStatuses = idleStatuses.filter { id, _ in accounts.contains { $0.id == id } }
-        idleMonitor.configure(accounts: accounts, enabled: true) { [weak self] id in
-            self?.scheduleIdleRefresh(accountID: id)
+        idleMonitor.configure(accounts: accounts, enabled: true) { [weak self] id, change in
+            self?.scheduleIdleRefresh(accountID: id, change: change)
         } report: { [weak self] id, status in
             self?.idleStatuses[id] = status
         } authenticationFailed: { [weak self] id in
@@ -720,9 +736,10 @@ final class MailStore {
         }
     }
 
-    private func scheduleIdleRefresh(accountID: UUID) {
+    private func scheduleIdleRefresh(accountID: UUID, change: IMAPClient.IdleChange) {
         guard accounts.contains(where: { $0.id == accountID }) else { return }
-        pendingIdleAccounts.insert(accountID)
+        if change == .refresh { pendingIdleAccounts.insert(accountID) }
+        else { pendingIdleChanges.append((accountID, change)) }
         guard idleRefreshTask == nil else { return }
         let generation = UUID()
         idleRefreshGeneration = generation
@@ -731,12 +748,18 @@ final class MailStore {
             defer { if self.idleRefreshGeneration == generation { self.idleRefreshTask = nil } }
             // Coalesce bursts and retain notifications arriving during another synchronization.
             try? await Task.sleep(for: .milliseconds(400))
-            while !Task.isCancelled, !self.pendingIdleAccounts.isEmpty {
+            while !Task.isCancelled, !self.pendingIdleAccounts.isEmpty || !self.pendingIdleChanges.isEmpty {
                 if self.isBusy {
                     do { try await Task.sleep(for: .milliseconds(200)) } catch { return }
                     continue
                 }
-                guard let id = self.pendingIdleAccounts.first else { return }
+                let changes = self.pendingIdleChanges
+                self.pendingIdleChanges.removeAll()
+                for (id, change) in changes {
+                    do { try self.applyIdleChange(accountID: id, change: change) }
+                    catch { self.pendingIdleAccounts.insert(id) }
+                }
+                guard let id = self.pendingIdleAccounts.first else { continue }
                 self.pendingIdleAccounts.remove(id)
                 guard self.accounts.contains(where: { $0.id == id }) else { continue }
                 await self.refresh(folderID: self.selectedFolderID, accountID: id, inboxOnly: true)
@@ -744,6 +767,28 @@ final class MailStore {
         }
     }
 
+    /// Apply IDLE echoes after in-flight mutations have committed their local changes.
+    func applyIdleChange(accountID: UUID, change: IMAPClient.IdleChange) throws {
+        guard let inbox = allFolders(folders[accountID] ?? []).first(where: \.isInbox) else { return }
+        let validity: String
+        let uid: UInt64
+        let flags: [String]?
+        switch change {
+        case .refresh:
+            return
+        case .removed(let value, let identifier):
+            (validity, uid, flags) = (value, identifier, nil)
+        case .flags(let value, let identifier, let values):
+            (validity, uid, flags) = (value, identifier, values)
+        }
+        let id = inbox.id + ":" + validity + ":" + String(uid)
+        // Local moves/deletions already removed the source. Do not revive it.
+        guard let record = try? storage().record(id: id) else { return }
+        if let flags, Set(record.flags) == Set(flags) { return }
+        try storage().applyMessageChange(id: id, flags: flags, removed: flags == nil)
+        try updateLocalPresentation()
+    }
+
     func requestPassword(accountID: UUID) {
         guard accounts.contains(where: { $0.id == accountID }) else { return }
         if authenticationAccountID == nil { authenticationAccountID = accountID }

MikeMailTests/MailActionTests.swift

@@ -4,6 +4,78 @@ import Testing
 
 @MainActor
 struct MailActionTests {
+    @Test func emptyTrashOnlyListsUIDsAndDeletesConfirmedBatches() async throws {
+        let trash = MailFolder(accountID: UUID(), path: "Trash", name: "Trash")
+        var commands: [String] = []
+        var removed: [UInt64] = []
+        let validity = try await IMAPClient.emptyTrash(folder: trash) { command in
+            commands.append(command)
+            switch command {
+            case "SELECT \"Trash\"": return .init(lines: ["* OK [UIDVALIDITY 7]"])
+            case "UID SEARCH ALL": return .init(lines: ["* SEARCH 10 20"])
+            case "CAPABILITY": return .init(lines: ["* CAPABILITY IMAP4rev1 UIDPLUS"])
+            case "UID STORE 10,20 +FLAGS.SILENT (\\Deleted)", "UID EXPUNGE 10,20":
+                return .init()
+            default:
+                Issue.record("Unexpected command: \(command)")
+                throw MailError.message("Unexpected command")
+            }
+        } onRemoved: { validity, uids in
+            #expect(validity == "7")
+            #expect(commands.last == "UID EXPUNGE 10,20")
+            removed += uids
+        }
+        #expect(validity == "7")
+        #expect(removed == [10, 20])
+        #expect(commands.count == 5)
+    }
+
+    @Test func partialTrashFailureKeepsConfirmedDeletionsAndOtherFolders() async throws {
+        let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: root) }
+        let archive = try MailArchive(root: root)
+        let account = UUID()
+        let trash = MailFolder(accountID: account, path: "Trash", name: "Trash")
+        let inbox = MailFolder(accountID: account, path: "INBOX", name: "Inbox")
+        let raw = Data("Subject: Fixture\r\n\r\nBody".utf8)
+        // Only a subset is cached locally; absent local records must not stop server deletion.
+        for uid in ["1", "201"] {
+            try archive.store(raw: raw, folderID: trash.id, validity: "7", uid: uid, flags: [])
+        }
+        try archive.store(raw: raw, folderID: inbox.id, validity: "7", uid: "1", flags: [])
+        try archive.store(raw: raw, folderID: trash.id, validity: "8", uid: "1", flags: [])
+        await #expect(throws: (any Error).self) {
+            _ = try await IMAPClient.emptyTrash(folder: trash) { command in
+                if command.hasPrefix("SELECT") { return .init(lines: ["* OK [UIDVALIDITY 7]"]) }
+                if command == "UID SEARCH ALL" {
+                    return .init(lines: ["* SEARCH " + (1...201).map(String.init).joined(separator: " ")])
+                }
+                if command == "CAPABILITY" { return .init(lines: ["* CAPABILITY UIDPLUS"]) }
+                if command == "UID EXPUNGE 201" { throw MailError.message("Connection lost") }
+                return .init()
+            } onRemoved: { validity, uids in
+                try archive.applyRemovals(folderID: trash.id, validity: validity, uids: uids)
+            }
+        }
+        #expect(Set(try archive.messages(folderID: trash.id).map(\.id)) ==
+            [trash.id + ":7:201", trash.id + ":8:1"])
+        #expect(try archive.messages(folderID: inbox.id).count == 1)
+    }
+
+    @Test func emptyTrashRequiresUIDPLUSBeforeDeleting() async throws {
+        let trash = MailFolder(accountID: UUID(), path: "Trash", name: "Trash")
+        var commands: [String] = []
+        await #expect(throws: (any Error).self) {
+            _ = try await IMAPClient.emptyTrash(folder: trash) { command in
+                commands.append(command)
+                if command.hasPrefix("SELECT") { return .init(lines: ["* OK [UIDVALIDITY 7]"]) }
+                if command == "UID SEARCH ALL" { return .init(lines: ["* SEARCH 1"]) }
+                return .init(lines: ["* CAPABILITY IMAP4rev1"])
+            } onRemoved: { _, _ in Issue.record("No deletion was confirmed") }
+        }
+        #expect(commands == ["SELECT \"Trash\"", "UID SEARCH ALL", "CAPABILITY"])
+    }
+
     @Test func ccAndBccStaySeparateFromEnvelope() throws {
         let raw = try MIME.compose(from: "sender@example.com", to: ["to@example.com"],
             cc: ["copy@example.com"], bcc: ["hidden@example.com"], subject: "CC BCC", body: "Hello", attachments: [])

MikeMailTests/MailArchiveTests.swift

@@ -140,6 +140,122 @@ struct MailArchiveTests {
         #expect(try reopened.messages(folderID: inboxA.id).count == 1)
     }
 
+    @Test func unchangedLargeMailboxNeedsOnlyTwoCommands() async throws {
+        let folder = MailFolder(accountID: UUID(), path: "INBOX", name: "Inbox")
+        let flags = Dictionary(uniqueKeysWithValues: (1...10_000).map { (UInt64($0), ["\\Seen"]) })
+        let previous = MailboxInventory(validity: "7", flags: flags, highestModSequence: 100)
+        var commands: [String] = []
+        let result = try await IMAPClient.fetchInventory(folder: folder, previous: previous,
+            supportsCONDSTORE: true) { command in
+            commands.append(command)
+            if command == "EXAMINE \"INBOX\" (CONDSTORE)" {
+                return .init(lines: ["* OK [UIDVALIDITY 7]", "* OK [HIGHESTMODSEQ 100]"])
+            }
+            #expect(command == "UID SEARCH ALL")
+            return .init(lines: ["* SEARCH " + (1...10_000).map(String.init).joined(separator: " ")])
+        }
+        #expect(result == previous)
+        #expect(commands.count == 2) // Previously: EXAMINE + SEARCH + 50 flag batches.
+    }
+
+    @Test func incrementalInventoryMergesFlagsArrivalsAndDeletions() async throws {
+        let folder = MailFolder(accountID: UUID(), path: "INBOX", name: "Inbox")
+        let previous = MailboxInventory(validity: "7", flags: [1: [], 2: [], 3: ["\\Flagged"]],
+            highestModSequence: 100)
+        var commands: [String] = []
+        let result = try await IMAPClient.fetchInventory(folder: folder, previous: previous,
+            supportsCONDSTORE: true) { command in
+            commands.append(command)
+            if command.hasPrefix("EXAMINE") {
+                return .init(lines: ["* OK [UIDVALIDITY 7]", "* OK [HIGHESTMODSEQ 110]"])
+            }
+            if command == "UID SEARCH ALL" { return .init(lines: ["* SEARCH 1 3 4"]) }
+            #expect(command == "UID FETCH 1:* (UID FLAGS) (CHANGEDSINCE 100)")
+            return .init(lines: ["* 1 FETCH (UID 1 FLAGS (\\Seen) MODSEQ (105))",
+                                 "* 3 FETCH (UID 4 FLAGS () MODSEQ (110))"])
+        }
+        #expect(result.flags == [1: ["\\Seen"], 3: ["\\Flagged"], 4: []])
+        #expect(result.highestModSequence == 110)
+        #expect(commands.count == 3)
+    }
+
+    @Test(arguments: ["unsupported", "nomodseq", "validity", "rollback", "firstSync"])
+    func inventoryFallsBackToFullFlags(reason: String) async throws {
+        let folder = MailFolder(accountID: UUID(), path: "INBOX", name: "Inbox")
+        let previous = MailboxInventory(validity: "7", flags: [1: ["\\Seen"]], highestModSequence: 100)
+        let validity = reason == "validity" ? "8" : "7"
+        var commands: [String] = []
+        let result = try await IMAPClient.fetchInventory(folder: folder,
+            previous: reason == "firstSync" ? nil : previous, supportsCONDSTORE: reason != "unsupported") { command in
+            commands.append(command)
+            if command.hasPrefix("EXAMINE") {
+                let sequence = reason == "nomodseq" ? "* OK [NOMODSEQ]" :
+                    "* OK [HIGHESTMODSEQ \(reason == "rollback" ? 90 : 110)]"
+                return .init(lines: ["* OK [UIDVALIDITY \(validity)]", sequence])
+            }
+            if command == "UID SEARCH ALL" { return .init(lines: ["* SEARCH 1"]) }
+            #expect(command == "UID FETCH 1:* (UID FLAGS)")
+            return .init(lines: ["* 1 FETCH (UID 1 FLAGS ())"])
+        }
+        #expect(result.validity == validity)
+        #expect(result.flags == [1: []])
+        #expect(commands.count == 3)
+        if reason == "unsupported" || reason == "nomodseq" {
+            #expect(result.highestModSequence == nil)
+        }
+    }
+
+    @Test func unchangedModSequenceStillDetectsDeletions() async throws {
+        let folder = MailFolder(accountID: UUID(), path: "INBOX", name: "Inbox")
+        let previous = MailboxInventory(validity: "7", flags: [1: [], 2: []], highestModSequence: 100)
+        let result = try await IMAPClient.fetchInventory(folder: folder, previous: previous,
+            supportsCONDSTORE: true) { command in
+            if command.hasPrefix("EXAMINE") {
+                return .init(lines: ["* OK [UIDVALIDITY 7]", "* OK [HIGHESTMODSEQ 100]"])
+            }
+            #expect(command == "UID SEARCH ALL")
+            return .init(lines: ["* SEARCH 2"])
+        }
+        #expect(result.flags == [2: []])
+    }
+
+    @Test func incompleteDeltaIsRejected() async throws {
+        let folder = MailFolder(accountID: UUID(), path: "INBOX", name: "Inbox")
+        let previous = MailboxInventory(validity: "7", flags: [1: []], highestModSequence: 100)
+        await #expect(throws: (any Error).self) {
+            _ = try await IMAPClient.fetchInventory(folder: folder, previous: previous,
+                supportsCONDSTORE: true) { command in
+                if command.hasPrefix("EXAMINE") {
+                    return .init(lines: ["* OK [UIDVALIDITY 7]", "* OK [HIGHESTMODSEQ 110]"])
+                }
+                if command == "UID SEARCH ALL" { return .init(lines: ["* SEARCH 1 2"]) }
+                return .init(lines: [])
+            }
+        }
+    }
+
+    @Test func syncSnapshotSurvivesRelaunchAndLocalResetStillDownloadsBodies() throws {
+        let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: root) }
+        let account = UUID()
+        let folder = MailFolder(accountID: account, path: "INBOX", name: "Inbox")
+        let inventory = MailboxInventory(validity: "7", flags: [1: []], highestModSequence: 100)
+        do {
+            let archive = try MailArchive(root: root)
+            try archive.store(raw: Data("Subject: Cached\r\n\r\nBody".utf8),
+                folderID: folder.id, validity: "7", uid: "1", flags: [], visible: false)
+            #expect(try archive.reconcile(folderID: folder.id, inventory: inventory))
+            #expect(try !archive.reconcile(folderID: folder.id, inventory: inventory))
+        }
+        let reopened = try MailArchive(root: root)
+        #expect(try reopened.syncInventory(folderID: folder.id) == inventory)
+        #expect(try reopened.knownUIDs(folderID: folder.id, validity: "7") == [1])
+        _ = try reopened.clearLocalMessages(accountID: account)
+        let snapshot = try #require(try reopened.syncInventory(folderID: folder.id))
+        let known = try reopened.knownUIDs(folderID: folder.id, validity: snapshot.validity)
+        #expect(Set(snapshot.flags.keys).subtracting(known) == [1])
+    }
+
     @Test func imapInventoryParsing() throws {
         #expect(try IMAPClient.uidValidity(from: ["* OK [UIDVALIDITY 123] UIDs valid"]) == "123")
         #expect(throws: (any Error).self) { try IMAPClient.uidValidity(from: ["* OK hello"]) }

MikeMailTests/MailIdleTests.swift

@@ -16,6 +16,54 @@ struct MailIdleTests {
         #expect(!IMAPClient.isAuthenticationFailure("* BYE Connection closed"))
     }
 
+    @Test func idleChangesTrackSequenceNumbersWithoutRefreshing() {
+        var mailbox = IMAPClient.IdleMailbox(validity: "7", uids: [10, 20, 30])
+        #expect(mailbox.receive("* 2 FETCH (FLAGS (\\Seen))") ==
+            .flags(validity: "7", uid: 20, flags: ["\\Seen"]))
+        #expect(mailbox.receive("* 2 EXPUNGE") == .removed(validity: "7", uid: 20))
+        #expect(mailbox.receive("* 2 EXPUNGE") == .removed(validity: "7", uid: 30))
+        #expect(mailbox.receive("* 1 EXISTS") == nil)
+        #expect(mailbox.receive("* 2 EXISTS") == .refresh)
+        #expect(mailbox.receive("* 2 FETCH (UID 40 FLAGS ())") ==
+            .flags(validity: "7", uid: 40, flags: []))
+        #expect(mailbox.receive("* 2 EXPUNGE") == .removed(validity: "7", uid: 40))
+        #expect(mailbox.receive("* 9 EXPUNGE") == .refresh)
+        #expect(mailbox.receive("* OK Still here") == nil)
+    }
+
+    @Test func idleEchoAfterMoveOrDeletionDoesNotReloadOrReviveSource() throws {
+        let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: root) }
+        let archive = try MailArchive(root: root)
+        let account = MailAccount(name: "A")
+        let inbox = MailFolder(accountID: account.id, path: "INBOX", name: "Inbox")
+        let trash = MailFolder(accountID: account.id, path: "Trash", name: "Trash")
+        try archive.saveConfiguration(ArchiveConfiguration(accounts: [account],
+            folders: [account.id: [inbox, trash]], recipients: []))
+        let raw = Data("Subject: Test\r\n\r\nBody".utf8)
+        try archive.store(raw: raw, folderID: inbox.id, validity: "7", uid: "10", flags: [])
+        let store = MailStore(archive: archive)
+        let id = inbox.id + ":7:10"
+        try archive.applyMessageChange(id: id, destination: trash.id,
+            assigned: .init(validity: "8", uid: "50"))
+        try store.applyIdleChange(accountID: account.id,
+            change: .flags(validity: "7", uid: 10, flags: ["\\Deleted"]))
+        try store.applyIdleChange(accountID: account.id, change: .removed(validity: "7", uid: 10))
+        #expect(store.archiveRevision == 0)
+        #expect(try archive.messages(folderID: inbox.id).isEmpty)
+        #expect(try archive.messages(folderID: trash.id).count == 1)
+        #expect(!store.isBusy)
+
+        // Changes from another client still update the archive without a network refresh.
+        try archive.store(raw: raw, folderID: inbox.id, validity: "7", uid: "20", flags: [])
+        try store.applyIdleChange(accountID: account.id,
+            change: .flags(validity: "7", uid: 20, flags: ["\\Seen"]))
+        #expect(try archive.messages(folderID: inbox.id).first?.isRead == true)
+        try store.applyIdleChange(accountID: account.id, change: .removed(validity: "7", uid: 20))
+        #expect(try archive.messages(folderID: inbox.id).isEmpty)
+        #expect(store.archiveRevision == 2)
+    }
+
     @Test func queuesPasswordPromptsPerAccount() throws {
         let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
         defer { try? FileManager.default.removeItem(at: root) }