feat(imap): en postkasse, der ikke er Gmail
Første del af IMAP-understøttelsen: selve klienten, som sit eget hjørne uden tråde ud i noget bestående. Den logger ind over TLS, henter de flagede beskeder nyere end et givet uid, og giver dem tilbage i samme form som Gmail-klienten — afsender, emne, uddrag — så den, der senere kalder dem, kan få at vide hvor der skal kigges og ikke hvordan. Flagede og ikke ulæste: ulæst er en tilstand, ejeren stadig bruger, og en synk, der brugte den op, ville tage noget fra ham. Det er samme begrundelse som stjerner på Gmail-siden. TLS er ikke valgfrit, og der er ingen kontakt til at slå det fra. Det her bærer et kodeord, der åbner en hel postkasse, og en kontakt til at fjerne beskyttelsen er en kontakt, der en dag bliver fundet allerede slået fra. iCloud og enhver almindelig udbyder taler det her. Office 365 gør ikke længere — Microsoft har lukket for kodeord på IMAP og vil have sit eget OAuth — så det er ikke en vært, man kan nå herfra, og at lade som om ville kun fejle senere og mindre tydeligt. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Kristian Wind
co-authored by
Claude Opus 5
Claude Opus 5
parent
c151d6c98c
commit
aabbbac583
@@ -0,0 +1,187 @@
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// Package imap reads a mailbox over IMAP and hands back the messages that should
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// become tasks.
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//
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// This exists next to internal/gmail rather than inside it because the two agree
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// on almost nothing. Gmail is an HTTP API with OAuth, labels and stars; IMAP is a
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// connection with a password, folders and flags. What they do share is the shape
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// of the answer — a handful of messages, each with a sender, a subject and enough
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// of a body to read — and that shape is Message here, deliberately identical to
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// what the Gmail client returns, so the caller can be told where to look and not
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// how to look.
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//
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// iCloud, Fastmail and any ordinary host speak this. Office 365 no longer accepts
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// a password here at all — it wants OAuth of its own — so it is not a host you can
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// reach with this package, and pretending otherwise would only fail later and
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// less clearly.
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package imap
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import (
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"crypto/tls"
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"fmt"
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"net"
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"strings"
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"time"
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"github.com/emersion/go-imap/v2"
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"github.com/emersion/go-imap/v2/imapclient"
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)
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// Message is one mail, reduced to what a task needs.
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type Message struct {
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UID uint32
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From string
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Subject string
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Snippet string
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Date time.Time
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}
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// Account is one mailbox to read.
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type Account struct {
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Host string // "imap.mail.me.com:993"
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Username string
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Password string // an app-specific password on every host worth naming
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Folder string // "INBOX" when empty
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}
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// Dial opens a TLS connection and logs in. The caller closes it.
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//
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// TLS is not optional and there is no flag to make it so: this carries a password
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// that unlocks a person's whole mailbox, and a switch for turning that protection
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// off is a switch that will one day be found already flipped.
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func Dial(a Account) (*Client, error) {
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host, _, err := net.SplitHostPort(a.Host)
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if err != nil {
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return nil, fmt.Errorf("host must include a port, like imap.mail.me.com:993: %w", err)
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}
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c, err := imapclient.DialTLS(a.Host, &imapclient.Options{
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TLSConfig: &tls.Config{ServerName: host, MinVersion: tls.VersionTLS12},
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})
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if err != nil {
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return nil, fmt.Errorf("connect to %s: %w", a.Host, err)
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}
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if err := c.Login(a.Username, a.Password).Wait(); err != nil {
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c.Close()
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// Deliberately not repeating the server's own words here. A bad password is
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// the overwhelmingly likely cause, and hosts answer it with everything from
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// "AUTHENTICATIONFAILED" to a sentence about web login being required.
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return nil, fmt.Errorf("%s refused the login for %s: %w", a.Host, a.Username, err)
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}
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folder := a.Folder
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if folder == "" {
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folder = "INBOX"
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}
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return &Client{c: c, folder: folder}, nil
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}
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// Client is a logged-in connection to one mailbox.
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type Client struct {
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c *imapclient.Client
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folder string
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}
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// Close ends the session politely, then hangs up regardless.
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func (c *Client) Close() error {
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if err := c.c.Logout().Wait(); err != nil {
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return c.c.Close()
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}
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return c.c.Close()
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}
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// Since returns the flagged messages in the folder newer than uid.
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//
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// Flagged, not unread: unread is a state the person is still using, and a sync
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// that consumed it would be taking something away. Flagging a mail is a deliberate
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// act with no other meaning, which is exactly what is wanted — the same reason the
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// Gmail side reads stars.
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func (c *Client) Since(uid uint32, limit int) ([]Message, error) {
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if _, err := c.c.Select(c.folder, &imap.SelectOptions{ReadOnly: true}).Wait(); err != nil {
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return nil, fmt.Errorf("open %s: %w", c.folder, err)
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}
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// From uid+1 to the end. A mailbox with nothing new answers with no uids
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// rather than an error, and that is not a failure worth reporting upwards.
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set := imap.UIDSetNum()
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set.AddRange(imap.UID(uid+1), 0)
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criteria := &imap.SearchCriteria{
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UID: []imap.UIDSet{set},
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Flag: []imap.Flag{imap.FlagFlagged},
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}
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found, err := c.c.UIDSearch(criteria, nil).Wait()
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if err != nil {
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return nil, fmt.Errorf("search %s: %w", c.folder, err)
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}
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uids := found.AllUIDs()
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if len(uids) == 0 {
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return nil, nil
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}
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if limit > 0 && len(uids) > limit {
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// The newest ones. A mailbox flagged over years would otherwise make the
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// first sync the largest one, which is the run most likely to be watched.
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uids = uids[len(uids)-limit:]
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}
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want := imap.UIDSetNum(uids...)
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fetch := &imap.FetchOptions{
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Envelope: true,
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UID: true,
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BodySection: []*imap.FetchItemBodySection{{Specifier: imap.PartSpecifierText, Peek: true}},
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}
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msgs, err := c.c.Fetch(want, fetch).Collect()
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if err != nil {
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return nil, fmt.Errorf("fetch from %s: %w", c.folder, err)
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}
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out := make([]Message, 0, len(msgs))
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for _, m := range msgs {
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if m.Envelope == nil {
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continue
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}
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out = append(out, Message{
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UID: uint32(m.UID),
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From: address(m.Envelope.From),
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Subject: strings.TrimSpace(m.Envelope.Subject),
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Snippet: snippet(m),
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Date: m.Envelope.Date,
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})
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}
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return out, nil
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}
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// address renders the first sender as "Name <addr>", or just the address.
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func address(list []imap.Address) string {
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if len(list) == 0 {
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return ""
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}
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a := list[0]
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addr := a.Addr()
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if a.Name == "" {
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return addr
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}
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return a.Name + " <" + addr + ">"
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}
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// snippet is the first readable line or so of the body.
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//
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// No MIME walk and no HTML stripping yet: this is what shows under a task's title,
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// and a wrong-but-short line is a smaller problem than a parser that has to be
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// right about every mail ever sent. The full mail stays where it is.
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const snippetLimit = 400
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func snippet(m *imapclient.FetchMessageBuffer) string {
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for _, body := range m.BodySection {
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text := strings.TrimSpace(string(body.Bytes))
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if text == "" {
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continue
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}
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if len(text) > snippetLimit {
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text = text[:snippetLimit] + "…"
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}
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return text
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}
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return ""
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}
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@@ -0,0 +1,77 @@
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package imap
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import (
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"strings"
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"testing"
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"github.com/emersion/go-imap/v2"
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"github.com/emersion/go-imap/v2/imapclient"
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)
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// A host without a port is the mistake everyone makes once, and the error a TLS
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// dial gives for it says nothing useful about which of the two fields is wrong.
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func TestAHostWithoutAPortSaysSo(t *testing.T) {
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_, err := Dial(Account{Host: "imap.mail.me.com", Username: "kw", Password: "x"})
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if err == nil {
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t.Fatal("a host with no port was accepted")
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}
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if !strings.Contains(err.Error(), "port") {
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t.Errorf("the error does not mention the port: %v", err)
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}
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}
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func TestASenderIsRenderedForReading(t *testing.T) {
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for _, c := range []struct {
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name string
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in []imap.Address
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want string
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}{
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{"nobody", nil, ""},
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{"bare address", []imap.Address{{Mailbox: "kw", Host: "nolimit.dk"}}, "kw@nolimit.dk"},
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{"with a name", []imap.Address{{Name: "Kristian Wind", Mailbox: "kw", Host: "nolimit.dk"}},
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"Kristian Wind <kw@nolimit.dk>"},
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// The first sender wins. A mail from two people is rare enough that naming
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// one is better than a task titled with a list.
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{"two senders", []imap.Address{
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{Mailbox: "first", Host: "example.dk"},
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{Mailbox: "second", Host: "example.dk"},
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}, "first@example.dk"},
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} {
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t.Run(c.name, func(t *testing.T) {
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if got := address(c.in); got != c.want {
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t.Errorf("got %q, want %q", got, c.want)
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}
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})
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}
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}
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// The snippet is what shows under a task's title, so its only real duty is to end.
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func TestASnippetIsTrimmedAndBounded(t *testing.T) {
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long := strings.Repeat("a", snippetLimit*2)
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m := &imapclient.FetchMessageBuffer{
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BodySection: []imapclient.FetchBodySectionBuffer{
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{Bytes: []byte(" ")},
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{Bytes: []byte(" " + long + " ")},
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},
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}
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got := snippet(m)
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if strings.HasPrefix(got, " ") || strings.HasSuffix(got, " ") {
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t.Errorf("the snippet is not trimmed: %q", got[:20])
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}
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// An empty part must not win over the one that has the text.
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if !strings.HasPrefix(got, "aaa") {
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t.Errorf("an empty body part was preferred: %q", got)
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}
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if len([]rune(got)) > snippetLimit+1 {
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t.Errorf("the snippet runs to %d characters", len([]rune(got)))
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}
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if !strings.HasSuffix(got, "…") {
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t.Error("a cut snippet does not say that it was cut")
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}
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}
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func TestAnEmptyMailboxIsNotAnError(t *testing.T) {
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if got := snippet(&imapclient.FetchMessageBuffer{}); got != "" {
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t.Errorf("a mail with no body parts gave %q", got)
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}
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}
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