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imapserver: implement NOTIFY extension from RFC 5465
NOTIFY is like IDLE, but where IDLE watches just the selected mailbox, NOTIFY can watch all mailboxes. With NOTIFY, a client can also ask a server to immediately return configurable fetch attributes for new messages, e.g. a message preview, certain header fields, or simply the entire message. Mild testing with evolution and fairemail.
This commit is contained in:
Mechiel Lukkien
329
imapserver/notify.go
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329
imapserver/notify.go
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@ -0,0 +1,329 @@
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package imapserver
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import (
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"fmt"
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"slices"
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"strings"
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"github.com/mjl-/bstore"
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"github.com/mjl-/mox/store"
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)
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// Max number of pending changes for selected-delayed mailbox before we write a
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// NOTIFICATIONOVERFLOW message, flush changes and stop gathering more changes.
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// Changed during tests.
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var selectedDelayedChangesMax = 1000
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// notify represents a configuration as passed to the notify command.
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type notify struct {
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// "NOTIFY NONE" results in an empty list, matching no events.
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EventGroups []eventGroup
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// Changes for the selected mailbox in case of SELECTED-DELAYED, when we don't send
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// events asynchrously. These must still be processed later on for their
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// ChangeRemoveUIDs, to erase expunged message files. At the end of a command (e.g.
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// NOOP) or immediately upon IDLE we will send untagged responses for these
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// changes. If the connection breaks, we still process the ChangeRemoveUIDs.
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Delayed []store.Change
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}
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// match checks if an event for a mailbox id/name (optional depending on type)
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// should be turned into a notification to the client.
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func (n notify) match(c *conn, xtxfn func() *bstore.Tx, mailboxID int64, mailbox string, kind eventKind) (mailboxSpecifier, notifyEvent, bool) {
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// We look through the event groups, and won't stop looking until we've found a
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// confirmation the event should be notified. ../rfc/5465:756
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// Non-message-related events are only matched by non-"selected" mailbox
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// specifiers. ../rfc/5465:268
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// If you read the mailboxes matching paragraph in isolation, you would think only
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// "SELECTED" and "SELECTED-DELAYED" can match events for the selected mailbox. But
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// a few other places hint that that only applies to message events, not to mailbox
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// events, such as subscriptions and mailbox metadata changes. With a strict
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// interpretation, clients couldn't request notifications for such events for the
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// selection mailbox. ../rfc/5465:752
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for _, eg := range n.EventGroups {
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switch eg.MailboxSpecifier.Kind {
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case mbspecSelected, mbspecSelectedDelayed: // ../rfc/5465:800
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if mailboxID != c.mailboxID || !slices.Contains(messageEventKinds, kind) {
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continue
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}
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for _, ev := range eg.Events {
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if eventKind(ev.Kind) == kind {
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return eg.MailboxSpecifier, ev, true
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}
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}
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// We can only have a single selected for notify, so no point in continuing the search.
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return mailboxSpecifier{}, notifyEvent{}, false
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default:
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// The selected mailbox can only match for non-message events for specifiers other
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// than "selected"/"selected-delayed".
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if c.mailboxID == mailboxID && slices.Contains(messageEventKinds, kind) {
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continue
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}
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}
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var match bool
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Match:
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switch eg.MailboxSpecifier.Kind {
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case mbspecPersonal: // ../rfc/5465:817
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match = true
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case mbspecInboxes: // ../rfc/5465:822
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if mailbox == "Inbox" || strings.HasPrefix(mailbox, "Inbox/") {
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match = true
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break Match
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}
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if mailbox == "" {
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break Match
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}
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// Include mailboxes we may deliver to based on destinations, or based on rulesets,
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// not including deliveries for mailing lists.
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conf, _ := c.account.Conf()
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for _, dest := range conf.Destinations {
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if dest.Mailbox == mailbox {
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match = true
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break Match
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}
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for _, rs := range dest.Rulesets {
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if rs.ListAllowDomain == "" && rs.Mailbox == mailbox {
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match = true
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break Match
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}
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}
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}
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case mbspecSubscribed: // ../rfc/5465:831
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sub := store.Subscription{Name: mailbox}
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err := xtxfn().Get(&sub)
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if err != bstore.ErrAbsent {
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xcheckf(err, "lookup subscription")
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}
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match = err == nil
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case mbspecSubtree: // ../rfc/5465:847
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for _, name := range eg.MailboxSpecifier.Mailboxes {
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if mailbox == name || strings.HasPrefix(mailbox, name+"/") {
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match = true
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break
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}
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}
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case mbspecSubtreeOne: // ../rfc/7377:274
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ntoken := len(strings.Split(mailbox, "/"))
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for _, name := range eg.MailboxSpecifier.Mailboxes {
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if mailbox == name || (strings.HasPrefix(mailbox, name+"/") && len(strings.Split(name, "/"))+1 == ntoken) {
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match = true
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break
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}
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}
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case mbspecMailboxes: // ../rfc/5465:853
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match = slices.Contains(eg.MailboxSpecifier.Mailboxes, mailbox)
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default:
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panic("missing case for " + string(eg.MailboxSpecifier.Kind))
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}
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if !match {
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continue
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}
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// NONE is the signal we shouldn't return events for this mailbox. ../rfc/5465:455
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if len(eg.Events) == 0 {
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break
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}
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// If event kind matches, we will be notifying about this change. If not, we'll
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// look again at next mailbox specifiers.
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for _, ev := range eg.Events {
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if eventKind(ev.Kind) == kind {
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return eg.MailboxSpecifier, ev, true
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}
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}
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}
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return mailboxSpecifier{}, notifyEvent{}, false
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}
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// Notify enables continuous notifications from the server to the client, without
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// the client issuing an IDLE command. The mailboxes and events to notify about are
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// specified in the account. When notify is enabled, instead of being blocked
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// waiting for a command from the client, we also wait for events from the account,
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// and send events about it.
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//
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// State: Authenticated and selected.
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func (c *conn) cmdNotify(tag, cmd string, p *parser) {
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// Command: ../rfc/5465:203
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// Request syntax: ../rfc/5465:923
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p.xspace()
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// NONE indicates client doesn't want any events, also not the "normal" events
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// without notify. ../rfc/5465:234
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// ../rfc/5465:930
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if p.take("NONE") {
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p.xempty()
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// If we have delayed changes for the selected mailbox, we are no longer going to
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// notify about them. The client can't know anymore whether messages still exist,
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// and trying to read them can cause errors if the messages have been expunged and
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// erased.
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var changes []store.Change
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if c.notify != nil {
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changes = c.notify.Delayed
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}
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c.notify = ¬ify{}
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c.flushChanges(changes)
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c.ok(tag, cmd)
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return
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}
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var n notify
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var status bool
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// ../rfc/5465:926
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p.xtake("SET")
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p.xspace()
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if p.take("STATUS") {
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status = true
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p.xspace()
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}
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for {
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eg := p.xeventGroup()
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n.EventGroups = append(n.EventGroups, eg)
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if !p.space() {
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break
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}
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}
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p.xempty()
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for _, eg := range n.EventGroups {
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var hasNew, hasExpunge, hasFlag, hasAnnotation bool
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for _, ev := range eg.Events {
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switch eventKind(ev.Kind) {
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case eventMessageNew:
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hasNew = true
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case eventMessageExpunge:
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hasExpunge = true
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case eventFlagChange:
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hasFlag = true
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case eventMailboxName, eventSubscriptionChange, eventMailboxMetadataChange, eventServerMetadataChange:
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// Nothing special.
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default: // Including eventAnnotationChange.
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hasAnnotation = true // Ineffective, we don't implement message annotations yet.
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// Result must be NO instead of BAD, and we must include BADEVENT and the events we
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// support. ../rfc/5465:343
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// ../rfc/5465:1033
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xusercodeErrorf("BADEVENT (MessageNew MessageExpunge FlagChange MailboxName SubscriptionChange MailboxMetadataChange ServerMetadataChange)", "unimplemented event %s", ev.Kind)
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}
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}
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if hasNew != hasExpunge {
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// ../rfc/5465:443 ../rfc/5465:987
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xsyntaxErrorf("MessageNew and MessageExpunge must be specified together")
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}
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if (hasFlag || hasAnnotation) && !hasNew {
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// ../rfc/5465:439
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xsyntaxErrorf("FlagChange and/or AnnotationChange requires MessageNew and MessageExpunge")
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}
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}
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for _, eg := range n.EventGroups {
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for i, name := range eg.MailboxSpecifier.Mailboxes {
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eg.MailboxSpecifier.Mailboxes[i] = xcheckmailboxname(name, true)
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}
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}
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// Only one selected/selected-delay mailbox filter is allowed. ../rfc/5465:779
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// Only message events are allowed for selected/selected-delayed. ../rfc/5465:796
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var haveSelected bool
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for _, eg := range n.EventGroups {
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switch eg.MailboxSpecifier.Kind {
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case mbspecSelected, mbspecSelectedDelayed:
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if haveSelected {
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xsyntaxErrorf("cannot have multiple selected/selected-delayed mailbox filters")
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}
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haveSelected = true
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// Only events from message-event are allowed with selected mailbox specifiers.
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// ../rfc/5465:977
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for _, ev := range eg.Events {
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if !slices.Contains(messageEventKinds, eventKind(ev.Kind)) {
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xsyntaxErrorf("selected/selected-delayed is only allowed with message events, not %s", ev.Kind)
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}
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}
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}
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}
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// We must apply any changes for delayed select. ../rfc/5465:248
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if c.notify != nil {
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delayed := c.notify.Delayed
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c.notify.Delayed = nil
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c.xapplyChangesNotify(delayed, true)
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}
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if status {
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var statuses []string
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// Flush new pending changes before we read the current state from the database.
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// Don't allow any concurrent changes for a consistent snapshot.
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c.account.WithRLock(func() {
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select {
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case <-c.comm.Pending:
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overflow, changes := c.comm.Get()
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c.xapplyChanges(overflow, changes, true, true)
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default:
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}
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c.xdbread(func(tx *bstore.Tx) {
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// Send STATUS responses for all matching mailboxes. ../rfc/5465:271
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q := bstore.QueryTx[store.Mailbox](tx)
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q.FilterEqual("Expunged", false)
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q.SortAsc("Name")
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for mb, err := range q.All() {
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xcheckf(err, "list mailboxes for status")
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if mb.ID == c.mailboxID {
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continue
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}
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_, _, ok := n.match(c, func() *bstore.Tx { return tx }, mb.ID, mb.Name, eventMessageNew)
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if !ok {
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continue
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}
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list := listspace{
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bare("MESSAGES"), number(mb.MessageCountIMAP()),
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bare("UIDNEXT"), number(mb.UIDNext),
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bare("UIDVALIDITY"), number(mb.UIDValidity),
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// Unseen is not mentioned for STATUS, but clients are able to parse it due to
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// FlagChange, and it will be useful to have.
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bare("UNSEEN"), number(mb.MailboxCounts.Unseen),
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}
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if c.enabled[capCondstore] || c.enabled[capQresync] {
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list = append(list, bare("HIGHESTMODSEQ"), number(mb.ModSeq))
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}
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status := fmt.Sprintf("* STATUS %s %s", mailboxt(mb.Name).pack(c), list.pack(c))
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statuses = append(statuses, status)
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}
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})
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})
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// Write outside of db transaction and lock.
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for _, s := range statuses {
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c.xbwritelinef("%s", s)
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}
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}
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// We replace the previous notify config. ../rfc/5465:245
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c.notify = &n
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// Writing OK will flush any other pending changes for the account according to the
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// new filters.
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c.ok(tag, cmd)
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}
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