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.

imapclient/client.go

@@ -185,13 +185,18 @@ func (c *Conn) xflush() {
 	}
 }
 
-func (c *Conn) xtrace(level slog.Level) func() {
-	c.xflush()
+func (c *Conn) xtraceread(level slog.Level) func() {
 	c.tr.SetTrace(level)
+	return func() {
+		c.tr.SetTrace(mlog.LevelTrace)
+	}
+}
+
+func (c *Conn) xtracewrite(level slog.Level) func() {
+	c.xflush()
 	c.xtw.SetTrace(level)
 	return func() {
 		c.xflush()
-		c.tr.SetTrace(mlog.LevelTrace)
 		c.xtw.SetTrace(mlog.LevelTrace)
 	}
 }
@@ -357,9 +362,10 @@ func (c *Conn) WriteSyncLiteral(s string) (untagged []Untagged, rerr error) {
 		_, err = c.Readline()
 		c.xcheckf(err, "read continuation line")
 
+		defer c.xtracewrite(mlog.LevelTracedata)()
 		_, err = c.xbw.Write([]byte(s))
 		c.xcheckf(err, "write literal data")
-		c.xflush()
+		c.xtracewrite(mlog.LevelTrace)
 		return nil, nil
 	}
 	untagged, result, err := c.Response()

imapclient/cmds.go

@@ -59,9 +59,9 @@ func (c *Conn) Login(username, password string) (untagged []Untagged, result Res
 
 	c.LastTag = c.nextTag()
 	fmt.Fprintf(c.xbw, "%s login %s ", c.LastTag, astring(username))
-	defer c.xtrace(mlog.LevelTraceauth)()
+	defer c.xtracewrite(mlog.LevelTraceauth)()
 	fmt.Fprintf(c.xbw, "%s\r\n", astring(password))
-	c.xtrace(mlog.LevelTrace) // Restore.
+	c.xtracewrite(mlog.LevelTrace) // Restore.
 	return c.Response()
 }
 
@@ -76,11 +76,11 @@ func (c *Conn) AuthenticatePlain(username, password string) (untagged []Untagged
 	if result.Status != "" {
 		c.xerrorf("got result status %q, expected continuation", result.Status)
 	}
-	defer c.xtrace(mlog.LevelTraceauth)()
+	defer c.xtracewrite(mlog.LevelTraceauth)()
 	xw := base64.NewEncoder(base64.StdEncoding, c.xbw)
 	fmt.Fprintf(xw, "\u0000%s\u0000%s", username, password)
 	xw.Close()
-	c.xtrace(mlog.LevelTrace) // Restore.
+	c.xtracewrite(mlog.LevelTrace) // Restore.
 	fmt.Fprintf(c.xbw, "\r\n")
 	c.xflush()
 	return c.Response()
@@ -317,10 +317,10 @@ func (c *Conn) Append(mailbox string, message Append, more ...Append) (untagged
 		// todo: for larger messages, use a synchronizing literal.
 
 		fmt.Fprintf(c.xbw, " (%s)%s {%d+}\r\n", strings.Join(m.Flags, " "), date, m.Size)
-		defer c.xtrace(mlog.LevelTracedata)()
+		defer c.xtracewrite(mlog.LevelTracedata)()
 		_, err := io.Copy(c.xbw, m.Data)
 		c.xcheckf(err, "write message data")
-		c.xtrace(mlog.LevelTrace) // Restore
+		c.xtracewrite(mlog.LevelTrace) // Restore
 	}
 
 	fmt.Fprintf(c.xbw, "\r\n")
@@ -328,7 +328,8 @@ func (c *Conn) Append(mailbox string, message Append, more ...Append) (untagged
 	return c.Response()
 }
 
-// note: No idle command. Idle is better implemented by writing the request and reading and handling the responses as they come in.
+// note: No Idle or Notify command. Idle/Notify is better implemented by
+// writing the request and reading and handling the responses as they come in.
 
 // CloseMailbox closes the currently selected/active mailbox, permanently removing
 // any messages marked with \Deleted.
@@ -444,10 +445,10 @@ func (c *Conn) replace(cmd string, num string, mailbox string, msg Append) (unta
 	err := c.Commandf("", "%s %s %s (%s)%s ~{%d+}", cmd, num, astring(mailbox), strings.Join(msg.Flags, " "), date, msg.Size)
 	c.xcheckf(err, "writing replace command")
 
-	defer c.xtrace(mlog.LevelTracedata)()
+	defer c.xtracewrite(mlog.LevelTracedata)()
 	_, err = io.Copy(c.xbw, msg.Data)
 	c.xcheckf(err, "write message data")
-	c.xtrace(mlog.LevelTrace)
+	c.xtracewrite(mlog.LevelTrace)
 
 	fmt.Fprintf(c.xbw, "\r\n")
 	c.xflush()

imapclient/parse.go

@@ -6,6 +6,8 @@ import (
 	"strconv"
 	"strings"
 	"time"
+
+	"github.com/mjl-/mox/mlog"
 )
 
 func (c *Conn) recorded() string {
@@ -131,7 +133,9 @@ var knownCodes = stringMap(
 	// With parameters.
 	"BADCHARSET", "CAPABILITY", "PERMANENTFLAGS", "UIDNEXT", "UIDVALIDITY", "UNSEEN", "APPENDUID", "COPYUID",
 	"HIGHESTMODSEQ", "MODIFIED",
-	"INPROGRESS", // ../rfc/9585:104
+	"INPROGRESS",                       // ../rfc/9585:104
+	"BADEVENT", "NOTIFICATIONOVERFLOW", // ../rfc/5465:1023
+	"SERVERBUG",
 )
 
 func stringMap(l ...string) map[string]struct{} {
@@ -247,6 +251,20 @@ func (c *Conn) xrespCode() (string, CodeArg) {
 			c.xtake(")")
 		}
 		codeArg = CodeInProgress{tag, current, goal}
+	case "BADEVENT":
+		// ../rfc/5465:1033
+		c.xspace()
+		c.xtake("(")
+		var l []string
+		for {
+			s := c.xatom()
+			l = append(l, s)
+			if !c.space() {
+				break
+			}
+		}
+		c.xtake(")")
+		codeArg = CodeBadEvent(l)
 	}
 	return W, codeArg
 }
@@ -896,8 +914,10 @@ func (c *Conn) xliteral() []byte {
 		c.xflush()
 	}
 	buf := make([]byte, int(size))
+	defer c.xtraceread(mlog.LevelTracedata)()
 	_, err := io.ReadFull(c.br, buf)
 	c.xcheckf(err, "reading data for literal")
+	c.xtraceread(mlog.LevelTrace)
 	return buf
 }
 

imapclient/protocol.go

@@ -42,6 +42,7 @@ const (
 	CapReplace          Capability = "REPLACE"            // ../rfc/8508:155
 	CapPreview          Capability = "PREVIEW"            // ../rfc/8970:114
 	CapMultiSearch      Capability = "MULTISEARCH"        // ../rfc/7377:187
+	CapNotify           Capability = "NOTIFY"             // ../rfc/5465:195
 )
 
 // Status is the tagged final result of a command.
@@ -186,6 +187,14 @@ func (c CodeInProgress) CodeString() string {
 	return fmt.Sprintf("INPROGRESS (%q %s %s)", c.Tag, current, goal)
 }
 
+// "BADEVENT" response code, with the events that are supported, for the NOTIFY
+// extension.
+type CodeBadEvent []string
+
+func (c CodeBadEvent) CodeString() string {
+	return fmt.Sprintf("BADEVENT (%s)", strings.Join([]string(c), " "))
+}
+
 // RespText represents a response line minus the leading tag.
 type RespText struct {
 	Code    string  // The first word between [] after the status.