Add basic pagination to message list

References: https://todo.sr.ht/~sircmpwn/koushin/22

conn_pool.go

@@ -21,7 +21,7 @@ func generateToken() (string, error) {
 var ErrSessionExpired = errors.New("session expired")
 
 type Session struct {
-	locker sync.Mutex
+	locker             sync.Mutex
 	imapConn           *imapclient.Client
 	username, password string
 }

imap.go

@@ -206,23 +206,23 @@ func (msg *imapMessage) PartTree() *IMAPPartNode {
 	return imapPartTree(msg.BodyStructure, nil)
 }
 
-func listMessages(conn *imapclient.Client, mboxName string) ([]imapMessage, error) {
+func listMessages(conn *imapclient.Client, mboxName string, page int) ([]imapMessage, error) {
 	if err := ensureMailboxSelected(conn, mboxName); err != nil {
 		return nil, err
 	}
 
-	n := uint32(50)
-
 	mbox := conn.Mailbox()
-	from := uint32(1)
-	to := mbox.Messages
-	if mbox.Messages == 0 {
+	to := int(mbox.Messages) - page*messagesPerPage
+	from := to - messagesPerPage
+	if from <= 0 {
+		from = 1
+	}
+	if to <= 0 {
 		return nil, nil
-	} else if mbox.Messages > n {
-		from = mbox.Messages - n
 	}
+
 	seqSet := new(imap.SeqSet)
-	seqSet.AddRange(from, to)
+	seqSet.AddRange(uint32(from), uint32(to))
 
 	fetch := []imap.FetchItem{imap.FetchEnvelope, imap.FetchUid, imap.FetchBodyStructure}
 
@@ -232,7 +232,7 @@ func listMessages(conn *imapclient.Client, mboxName string) ([]imapMessage, erro
 		done <- conn.Fetch(seqSet, fetch, ch)
 	}()
 
-	msgs := make([]imapMessage, 0, n)
+	msgs := make([]imapMessage, 0, to-from)
 	for msg := range ch {
 		msgs = append(msgs, imapMessage{msg})
 	}

public/mailbox.html

@@ -20,10 +20,23 @@
 	<ul>
 		{{range .Messages}}
 			<li><a href="/message/{{$.Mailbox.Name | pathescape}}/{{.Uid}}?part={{.TextPartName}}">
-				{{.Envelope.Subject}}
+				{{if .Envelope.Subject}}
+					{{.Envelope.Subject}}
+				{{else}}
+					(No subject)
+				{{end}}
 			</a></li>
 		{{end}}
 	</ul>
+
+	<p>
+		{{if ge .PrevPage 0}}
+			<a href="?page={{.PrevPage}}">Prev</a>
+		{{end}}
+		{{if ge .NextPage 0}}
+			<a href="?page={{.NextPage}}">Next</a>
+		{{end}}
+	</p>
 {{else}}
 	<p>Mailbox is empty.</p>
 {{end}}

public/message.html

@@ -6,7 +6,13 @@
 	<a href="/mailbox/{{.Mailbox.Name | pathescape}}">Back</a>
 </p>
 
-<h2>{{.Message.Envelope.Subject}}</h2>
+<h2>
+	{{if .Message.Envelope.Subject}}
+		{{.Message.Envelope.Subject}}
+	{{else}}
+		(No subject)
+	{{end}}
+</h2>
 
 {{define "message-part-tree"}}
 	{{/* nested templates can't access the parent's context */}}

server.go

@@ -6,6 +6,7 @@ import (
 	"mime"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -18,6 +19,8 @@ import (
 
 const cookieName = "koushin_session"
 
+const messagesPerPage = 50
+
 type Server struct {
 	imap struct {
 		host     string
@@ -366,6 +369,14 @@ func New(imapURL, smtpURL string) *echo.Echo {
 			return echo.NewHTTPError(http.StatusBadRequest, err)
 		}
 
+		page := 0
+		if pageStr := ctx.QueryParam("page"); pageStr != "" {
+			var err error
+			if page, err = strconv.Atoi(pageStr); err != nil || page < 0 {
+				return echo.NewHTTPError(http.StatusBadRequest, "invalid page index")
+			}
+		}
+
 		var mailboxes []*imap.MailboxInfo
 		var msgs []imapMessage
 		var mbox *imap.MailboxStatus
@@ -374,7 +385,7 @@ func New(imapURL, smtpURL string) *echo.Echo {
 			if mailboxes, err = listMailboxes(c); err != nil {
 				return err
 			}
-			if msgs, err = listMessages(c, mboxName); err != nil {
+			if msgs, err = listMessages(c, mboxName, page); err != nil {
 				return err
 			}
 			mbox = c.Mailbox()
@@ -384,10 +395,20 @@ func New(imapURL, smtpURL string) *echo.Echo {
 			return err
 		}
 
+		prevPage, nextPage := -1, -1
+		if page > 0 {
+			prevPage = page - 1
+		}
+		if (page+1)*messagesPerPage < int(mbox.Messages) {
+			nextPage = page + 1
+		}
+
 		return ctx.Render(http.StatusOK, "mailbox.html", map[string]interface{}{
 			"Mailbox":   mbox,
 			"Mailboxes": mailboxes,
 			"Messages":  msgs,
+			"PrevPage":  prevPage,
+			"NextPage":  nextPage,
 		})
 	})
 

smtp.go

@@ -3,9 +3,9 @@ package koushin
 import (
 	"bufio"
 	"fmt"
-	"time"
 	"io"
 	"strings"
+	"time"
 
 	"github.com/emersion/go-message/mail"
 	"github.com/emersion/go-smtp"
@@ -50,11 +50,11 @@ func (s *Server) connectSMTP() (*smtp.Client, error) {
 }
 
 type OutgoingMessage struct {
-	From string
-	To []string
-	Subject string
+	From      string
+	To        []string
+	Subject   string
 	InReplyTo string
-	Text string
+	Text      string
 }
 
 func (msg *OutgoingMessage) ToString() string {

strconv.go

@@ -2,9 +2,9 @@ package koushin
 
 import (
 	"fmt"
+	"net/url"
 	"strconv"
 	"strings"
-	"net/url"
 )
 
 func parseUid(s string) (uint32, error) {