add a webapi and webhooks for a simple http/json-based api

for applications to compose/send messages, receive delivery feedback, and
maintain suppression lists.

this is an alternative to applications using a library to compose messages,
submitting those messages using smtp, and monitoring a mailbox with imap for
DSNs, which can be processed into the equivalent of suppression lists. but you
need to know about all these standards/protocols and find libraries. by using
the webapi & webhooks, you just need a http & json library.

unfortunately, there is no standard for these kinds of api, so mox has made up
yet another one...

matching incoming DSNs about deliveries to original outgoing messages requires
keeping history of "retired" messages (delivered from the queue, either
successfully or failed). this can be enabled per account. history is also
useful for debugging deliveries. we now also keep history of each delivery
attempt, accessible while still in the queue, and kept when a message is
retired. the queue webadmin pages now also have pagination, to show potentially
large history.

a queue of webhook calls is now managed too. failures are retried similar to
message deliveries. webhooks can also be saved to the retired list after
completing. also configurable per account.

messages can be sent with a "unique smtp mail from" address. this can only be
used if the domain is configured with a localpart catchall separator such as
"+". when enabled, a queued message gets assigned a random "fromid", which is
added after the separator when sending. when DSNs are returned, they can be
related to previously sent messages based on this fromid. in the future, we can
implement matching on the "envid" used in the smtp dsn extension, or on the
"message-id" of the message. using a fromid can be triggered by authenticating
with a login email address that is configured as enabling fromid.

suppression lists are automatically managed per account. if a delivery attempt
results in certain smtp errors, the destination address is added to the
suppression list. future messages queued for that recipient will immediately
fail without a delivery attempt. suppression lists protect your mail server
reputation.

submitted messages can carry "extra" data through the queue and webhooks for
outgoing deliveries. through webapi as a json object, through smtp submission
as message headers of the form "x-mox-extra-<key>: value".

to make it easy to test webapi/webhooks locally, the "localserve" mode actually
puts messages in the queue. when it's time to deliver, it still won't do a full
delivery attempt, but just delivers to the sender account. unless the recipient
address has a special form, simulating a failure to deliver.

admins now have more control over the queue. "hold rules" can be added to mark
newly queued messages as "on hold", pausing delivery. rules can be about
certain sender or recipient domains/addresses, or apply to all messages pausing
the entire queue. also useful for (local) testing.

new config options have been introduced. they are editable through the admin
and/or account web interfaces.

the webapi http endpoints are enabled for newly generated configs with the
quickstart, and in localserve. existing configurations must explicitly enable
the webapi in mox.conf.

gopherwatch.org was created to dogfood this code. it initially used just the
compose/smtpclient/imapclient mox packages to send messages and process
delivery feedback. it will get a config option to use the mox webapi/webhooks
instead. the gopherwatch code to use webapi/webhook is smaller and simpler, and
developing that shaped development of the mox webapi/webhooks.

for issue #31 by cuu508

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	"context"
 	"crypto"
@@ -23,9 +24,11 @@ import (
 	"log"
 	"log/slog"
 	"net"
+	"net/http"
 	"net/url"
 	"os"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"slices"
 	"strconv"
@@ -57,6 +60,7 @@ import (
 	"github.com/mjl-/mox/moxvar"
 	"github.com/mjl-/mox/mtasts"
 	"github.com/mjl-/mox/publicsuffix"
+	"github.com/mjl-/mox/queue"
 	"github.com/mjl-/mox/smtp"
 	"github.com/mjl-/mox/smtpclient"
 	"github.com/mjl-/mox/spf"
@@ -65,6 +69,7 @@ import (
 	"github.com/mjl-/mox/tlsrptdb"
 	"github.com/mjl-/mox/updates"
 	"github.com/mjl-/mox/webadmin"
+	"github.com/mjl-/mox/webapi"
 )
 
 var (
@@ -111,6 +116,18 @@ var commands = []struct {
 	{"queue fail", cmdQueueFail},
 	{"queue drop", cmdQueueDrop},
 	{"queue dump", cmdQueueDump},
+	{"queue retired list", cmdQueueRetiredList},
+	{"queue retired print", cmdQueueRetiredPrint},
+	{"queue suppress list", cmdQueueSuppressList},
+	{"queue suppress add", cmdQueueSuppressAdd},
+	{"queue suppress remove", cmdQueueSuppressRemove},
+	{"queue suppress lookup", cmdQueueSuppressLookup},
+	{"queue webhook list", cmdQueueHookList},
+	{"queue webhook schedule", cmdQueueHookSchedule},
+	{"queue webhook cancel", cmdQueueHookCancel},
+	{"queue webhook print", cmdQueueHookPrint},
+	{"queue webhook retired list", cmdQueueHookRetiredList},
+	{"queue webhook retired print", cmdQueueHookRetiredPrint},
 	{"import maildir", cmdImportMaildir},
 	{"import mbox", cmdImportMbox},
 	{"export maildir", cmdExportMaildir},
@@ -134,7 +151,7 @@ var commands = []struct {
 	{"config describe-sendmail", cmdConfigDescribeSendmail},
 	{"config printservice", cmdConfigPrintservice},
 	{"config ensureacmehostprivatekeys", cmdConfigEnsureACMEHostprivatekeys},
-	{"example", cmdExample},
+	{"config example", cmdConfigExample},
 
 	{"checkupdate", cmdCheckupdate},
 	{"cid", cmdCid},
@@ -166,7 +183,9 @@ var commands = []struct {
 	{"tlsrpt lookup", cmdTLSRPTLookup},
 	{"tlsrpt parsereportmsg", cmdTLSRPTParsereportmsg},
 	{"version", cmdVersion},
+	{"webapi", cmdWebapi},
 
+	{"example", cmdExample},
 	{"bumpuidvalidity", cmdBumpUIDValidity},
 	{"reassignuids", cmdReassignUIDs},
 	{"fixuidmeta", cmdFixUIDMeta},
@@ -196,6 +215,7 @@ var commands = []struct {
 	{"ximport mbox", cmdXImportMbox},
 	{"openaccounts", cmdOpenaccounts},
 	{"readmessages", cmdReadmessages},
+	{"queuefillretired", cmdQueueFillRetired},
 }
 
 var cmds []cmd
@@ -2384,6 +2404,7 @@ The report is printed in formatted JSON.
 		// todo future: only print the highlights?
 		enc := json.NewEncoder(os.Stdout)
 		enc.SetIndent("", "\t")
+		enc.SetEscapeHTML(false)
 		err = enc.Encode(reportJSON)
 		xcheckf(err, "write report")
 	}
@@ -2661,6 +2682,97 @@ func cmdVersion(c *cmd) {
 	fmt.Printf("%s %s/%s\n", runtime.Version(), runtime.GOOS, runtime.GOARCH)
 }
 
+func cmdWebapi(c *cmd) {
+	c.params = "[method [baseurl-with-credentials]"
+	c.help = "Lists available methods, prints request/response parameters for method, or calls a method with a request read from standard input."
+	args := c.Parse()
+	if len(args) > 2 {
+		c.Usage()
+	}
+
+	t := reflect.TypeOf((*webapi.Methods)(nil)).Elem()
+	methods := map[string]reflect.Type{}
+	var ml []string
+	for i := 0; i < t.NumMethod(); i++ {
+		mt := t.Method(i)
+		methods[mt.Name] = mt.Type
+		ml = append(ml, mt.Name)
+	}
+
+	if len(args) == 0 {
+		fmt.Println(strings.Join(ml, "\n"))
+		return
+	}
+
+	mt, ok := methods[args[0]]
+	if !ok {
+		log.Fatalf("unknown method %q", args[0])
+	}
+	resultNotJSON := mt.Out(0).Kind() == reflect.Interface
+
+	if len(args) == 1 {
+		fmt.Println("# Example request")
+		fmt.Println()
+		printJSON("\t", mox.FillExample(nil, reflect.New(mt.In(1))).Interface())
+		fmt.Println()
+		if resultNotJSON {
+			fmt.Println("Output is non-JSON data.")
+			return
+		}
+		fmt.Println("# Example response")
+		fmt.Println()
+		printJSON("\t", mox.FillExample(nil, reflect.New(mt.Out(0))).Interface())
+		return
+	}
+
+	var response any
+	if !resultNotJSON {
+		response = reflect.New(mt.Out(0))
+	}
+
+	fmt.Fprintln(os.Stderr, "reading request from stdin...")
+	request, err := io.ReadAll(os.Stdin)
+	xcheckf(err, "read message")
+
+	dec := json.NewDecoder(bytes.NewReader(request))
+	dec.DisallowUnknownFields()
+	err = dec.Decode(reflect.New(mt.In(1)).Interface())
+	xcheckf(err, "parsing request")
+
+	resp, err := http.PostForm(args[1]+args[0], url.Values{"request": []string{string(request)}})
+	xcheckf(err, "http post")
+	defer resp.Body.Close()
+	if resp.StatusCode == http.StatusBadRequest {
+		buf, err := io.ReadAll(&moxio.LimitReader{R: resp.Body, Limit: 10 * 1024})
+		xcheckf(err, "reading response for 400 bad request error")
+		err = json.Unmarshal(buf, &response)
+		if err == nil {
+			printJSON("", response)
+		} else {
+			fmt.Fprintf(os.Stderr, "(not json)\n")
+			os.Stderr.Write(buf)
+		}
+		os.Exit(1)
+	} else if resp.StatusCode != http.StatusOK {
+		fmt.Fprintf(os.Stderr, "http response %s\n", resp.Status)
+		_, err := io.Copy(os.Stderr, resp.Body)
+		xcheckf(err, "copy body")
+	} else {
+		err := json.NewDecoder(resp.Body).Decode(&resp)
+		xcheckf(err, "unmarshal response")
+		printJSON("", response)
+	}
+}
+
+func printJSON(indent string, v any) {
+	fmt.Printf("%s", indent)
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent(indent, "\t")
+	enc.SetEscapeHTML(false)
+	err := enc.Encode(v)
+	xcheckf(err, "encode json")
+}
+
 // todo: should make it possible to run this command against a running mox. it should disconnect existing clients for accounts with a bumped uidvalidity, so they will reconnect and refetch the data.
 func cmdBumpUIDValidity(c *cmd) {
 	c.params = "account [mailbox]"
@@ -3020,6 +3132,8 @@ func cmdMessageParse(c *cmd) {
 	c.params = "message.eml"
 	c.help = "Parse message, print JSON representation."
 
+	var smtputf8 bool
+	c.flag.BoolVar(&smtputf8, "smtputf8", false, "check if message needs smtputf8")
 	args := c.Parse()
 	if len(args) != 1 {
 		c.Usage()
@@ -3035,8 +3149,40 @@ func cmdMessageParse(c *cmd) {
 	xcheckf(err, "parsing nested parts")
 	enc := json.NewEncoder(os.Stdout)
 	enc.SetIndent("", "\t")
+	enc.SetEscapeHTML(false)
 	err = enc.Encode(part)
 	xcheckf(err, "write")
+
+	hasNonASCII := func(r io.Reader) bool {
+		br := bufio.NewReader(r)
+		for {
+			b, err := br.ReadByte()
+			if err == io.EOF {
+				break
+			}
+			xcheckf(err, "read header")
+			if b > 0x7f {
+				return true
+			}
+		}
+		return false
+	}
+
+	var walk func(p *message.Part) bool
+	walk = func(p *message.Part) bool {
+		if hasNonASCII(p.HeaderReader()) {
+			return true
+		}
+		for _, pp := range p.Parts {
+			if walk(&pp) {
+				return true
+			}
+		}
+		return false
+	}
+	if smtputf8 {
+		fmt.Println("message needs smtputf8:", walk(&part))
+	}
 }
 
 func cmdOpenaccounts(c *cmd) {
@@ -3240,3 +3386,134 @@ Opens database files directly, not going through a running mox instance.
 		log.Printf("account %s, total time %s", accName, time.Since(t0))
 	}
 }
+
+func cmdQueueFillRetired(c *cmd) {
+	c.unlisted = true
+	c.help = `Fill retired messag and webhooks queue with testdata.
+
+For testing the pagination. Operates directly on queue database.
+`
+	var n int
+	c.flag.IntVar(&n, "n", 10000, "retired messages and retired webhooks to insert")
+	args := c.Parse()
+	if len(args) != 0 {
+		c.Usage()
+	}
+
+	mustLoadConfig()
+	err := queue.Init()
+	xcheckf(err, "init queue")
+	err = queue.DB.Write(context.Background(), func(tx *bstore.Tx) error {
+		now := time.Now()
+
+		// Cause autoincrement ID for queue.Msg to be forwarded, and use the reserved ID
+		// space for inserting retired messages.
+		fm := queue.Msg{}
+		err = tx.Insert(&fm)
+		xcheckf(err, "temporarily insert message to get autoincrement sequence")
+		err = tx.Delete(&fm)
+		xcheckf(err, "removing temporary message for resetting autoincrement sequence")
+		fm.ID += int64(n)
+		err = tx.Insert(&fm)
+		xcheckf(err, "temporarily insert message to forward autoincrement sequence")
+		err = tx.Delete(&fm)
+		xcheckf(err, "removing temporary message after forwarding autoincrement sequence")
+		fm.ID -= int64(n)
+
+		// And likewise for webhooks.
+		fh := queue.Hook{Account: "x", URL: "x", NextAttempt: time.Now()}
+		err = tx.Insert(&fh)
+		xcheckf(err, "temporarily insert webhook to get autoincrement sequence")
+		err = tx.Delete(&fh)
+		xcheckf(err, "removing temporary webhook for resetting autoincrement sequence")
+		fh.ID += int64(n)
+		err = tx.Insert(&fh)
+		xcheckf(err, "temporarily insert webhook to forward autoincrement sequence")
+		err = tx.Delete(&fh)
+		xcheckf(err, "removing temporary webhook after forwarding autoincrement sequence")
+		fh.ID -= int64(n)
+
+		for i := 0; i < n; i++ {
+			t0 := now.Add(-time.Duration(i) * time.Second)
+			last := now.Add(-time.Duration(i/10) * time.Second)
+			mr := queue.MsgRetired{
+				ID:                 fm.ID + int64(i),
+				Queued:             t0,
+				SenderAccount:      "test",
+				SenderLocalpart:    "mox",
+				SenderDomainStr:    "localhost",
+				FromID:             fmt.Sprintf("%016d", i),
+				RecipientLocalpart: "mox",
+				RecipientDomain:    dns.IPDomain{Domain: dns.Domain{ASCII: "localhost"}},
+				RecipientDomainStr: "localhost",
+				Attempts:           i % 6,
+				LastAttempt:        &last,
+				Results: []queue.MsgResult{
+					{
+						Start:    last,
+						Duration: time.Millisecond,
+						Success:  i%10 != 0,
+						Code:     250,
+					},
+				},
+				Has8bit:          i%2 == 0,
+				SMTPUTF8:         i%8 == 0,
+				Size:             int64(i * 100),
+				MessageID:        fmt.Sprintf("<msg%d@localhost>", i),
+				Subject:          fmt.Sprintf("test message %d", i),
+				Extra:            map[string]string{"i": fmt.Sprintf("%d", i)},
+				LastActivity:     last,
+				RecipientAddress: "mox@localhost",
+				Success:          i%10 != 0,
+				KeepUntil:        now.Add(48 * time.Hour),
+			}
+			err := tx.Insert(&mr)
+			xcheckf(err, "inserting retired message")
+		}
+
+		for i := 0; i < n; i++ {
+			t0 := now.Add(-time.Duration(i) * time.Second)
+			last := now.Add(-time.Duration(i/10) * time.Second)
+			var event string
+			if i%10 != 0 {
+				event = "delivered"
+			}
+			hr := queue.HookRetired{
+				ID:            fh.ID + int64(i),
+				QueueMsgID:    fm.ID + int64(i),
+				FromID:        fmt.Sprintf("%016d", i),
+				MessageID:     fmt.Sprintf("<msg%d@localhost>", i),
+				Subject:       fmt.Sprintf("test message %d", i),
+				Extra:         map[string]string{"i": fmt.Sprintf("%d", i)},
+				Account:       "test",
+				URL:           "http://localhost/hook",
+				IsIncoming:    i%10 == 0,
+				OutgoingEvent: event,
+				Payload:       "{}",
+
+				Submitted: t0,
+				Attempts:  i % 6,
+				Results: []queue.HookResult{
+					{
+						Start:    t0,
+						Duration: time.Millisecond,
+						URL:      "http://localhost/hook",
+						Success:  i%10 != 0,
+						Code:     200,
+						Response: "ok",
+					},
+				},
+
+				Success:      i%10 != 0,
+				LastActivity: last,
+				KeepUntil:    now.Add(48 * time.Hour),
+			}
+			err := tx.Insert(&hr)
+			xcheckf(err, "inserting retired hook")
+		}
+
+		return nil
+	})
+	xcheckf(err, "add to queue")
+	log.Printf("added %d retired messages and %d retired webhooks", n, n)
+}