From 25c63d05302fef11f79c30270a6e911da9010a38 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Mon, 2 Dec 2019 19:53:09 +0100
Subject: [PATCH] Add basic message view

---
 go.mod              |   1 +
 go.sum              |   2 +
 imap.go             | 155 +++++++++++++++++++++++++++++++++++++++++---
 public/mailbox.html |   6 +-
 server.go           |  56 ++++++++++++++++
 5 files changed, 211 insertions(+), 9 deletions(-)

diff --git a/go.mod b/go.mod
index 07d3dac..669cb67 100644
--- a/go.mod
+++ b/go.mod
@@ -4,5 +4,6 @@ go 1.13
 
 require (
 	github.com/emersion/go-imap v1.0.1
+	github.com/emersion/go-message v0.10.4-0.20190609165112-592ace5bc1ca
 	github.com/labstack/echo/v4 v4.1.11
 )
diff --git a/go.sum b/go.sum
index bd3e888..0e963f9 100644
--- a/go.sum
+++ b/go.sum
@@ -3,9 +3,11 @@ github.com/dgrijalva/jwt-go v3.2.0+incompatible h1:7qlOGliEKZXTDg6OTjfoBKDXWrumC
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/emersion/go-imap v1.0.1 h1:J3duplefIrglQtE63hCGYdGLgMjYWqHvkUUEbimbXY8=
 github.com/emersion/go-imap v1.0.1/go.mod h1:MEiDDwwQFcZ+L45Pa68jNGv0qU9kbW+SJzwDpvSfX1s=
+github.com/emersion/go-message v0.10.4-0.20190609165112-592ace5bc1ca h1:OYhqtJI4eOLvGtRIsUfP87VMJ1J/o6ks1tah9DlYkn4=
 github.com/emersion/go-message v0.10.4-0.20190609165112-592ace5bc1ca/go.mod h1:3h+HsGTCFHmk4ngJ2IV/YPhdlaOcR6hcgqM3yca9v7c=
 github.com/emersion/go-sasl v0.0.0-20190520160400-47d427600317 h1:tYZxAY8nu3JJQKios9f27Sbvbkfm4XHXT476gVtszu0=
 github.com/emersion/go-sasl v0.0.0-20190520160400-47d427600317/go.mod h1:G/dpzLu16WtQpBfQ/z3LYiYJn3ZhKSGWn83fyoyQe/k=
+github.com/emersion/go-textwrapper v0.0.0-20160606182133-d0e65e56babe h1:40SWqY0zE3qCi6ZrtTf5OUdNm5lDnGnjRSq9GgmeTrg=
 github.com/emersion/go-textwrapper v0.0.0-20160606182133-d0e65e56babe/go.mod h1:aqO8z8wPrjkscevZJFVE1wXJrLpC5LtJG7fqLOsPb2U=
 github.com/labstack/echo v3.3.10+incompatible h1:pGRcYk231ExFAyoAjAfD85kQzRJCRI8bbnE7CX5OEgg=
 github.com/labstack/echo/v4 v4.1.11 h1:z0BZoArY4FqdpUEl+wlHp4hnr/oSR6MTmQmv8OHSoww=
diff --git a/imap.go b/imap.go
index 869d457..3da0447 100644
--- a/imap.go
+++ b/imap.go
@@ -1,9 +1,16 @@
 package koushin
 
 import (
+	"bufio"
+	"fmt"
+	"io/ioutil"
 	"sort"
+	"strconv"
+	"strings"
 
 	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message"
+	"github.com/emersion/go-message/textproto"
 	imapclient "github.com/emersion/go-imap/client"
 )
 
@@ -53,17 +60,91 @@ func listMailboxes(conn *imapclient.Client) ([]*imap.MailboxInfo, error) {
 	return mailboxes, nil
 }
 
-func listMessages(conn *imapclient.Client, mboxName string) ([]*imap.Message, error) {
+func ensureMailboxSelected(conn *imapclient.Client, mboxName string) error {
 	mbox := conn.Mailbox()
 	if mbox == nil || mbox.Name != mboxName {
-		var err error
-		mbox, err = conn.Select(mboxName, false)
-		if err != nil {
-			return nil, err
+		if _, err := conn.Select(mboxName, false); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+type imapMessage struct {
+	*imap.Message
+}
+
+func textPartPath(bs *imap.BodyStructure) ([]int, bool) {
+	if bs.Disposition != "" && !strings.EqualFold(bs.Disposition, "inline") {
+		return nil, false
+	}
+
+	if strings.EqualFold(bs.MIMEType, "text") {
+		return []int{1}, true
+	}
+
+	if !strings.EqualFold(bs.MIMEType, "multipart") {
+		return nil, false
+	}
+
+	textPartNum := -1
+	for i, part := range bs.Parts {
+		num := i + 1
+
+		if strings.EqualFold(part.MIMEType, "multipart") {
+			if subpath, ok := textPartPath(part); ok {
+				return append([]int{num}, subpath...), true
+			}
+		}
+		if !strings.EqualFold(part.MIMEType, "text") {
+			continue
+		}
+
+		var pick bool
+		switch strings.ToLower(part.MIMESubType) {
+		case "plain":
+			pick = true
+		case "html":
+			pick = textPartNum < 0
+		}
+
+		if pick {
+			textPartNum = num
 		}
 	}
 
+	if textPartNum > 0 {
+		return []int{textPartNum}, true
+	}
+	return nil, false
+}
+
+func (msg *imapMessage) TextPartName() string {
+	if msg.BodyStructure == nil {
+		return ""
+	}
+
+	path, ok := textPartPath(msg.BodyStructure)
+	if !ok {
+		return ""
+	}
+
+	l := make([]string, len(path))
+	for i, partNum := range path {
+		l[i] = strconv.Itoa(partNum)
+	}
+
+	return strings.Join(l, ".")
+}
+
+func listMessages(conn *imapclient.Client, mboxName string) ([]imapMessage, error) {
+	if err := ensureMailboxSelected(conn, mboxName); err != nil {
+		return nil, err
+	}
+
 	n := uint32(10)
+
+	mbox := conn.Mailbox()
 	from := uint32(1)
 	to := mbox.Messages
 	if mbox.Messages > n {
@@ -72,15 +153,17 @@ func listMessages(conn *imapclient.Client, mboxName string) ([]*imap.Message, er
 	seqSet := new(imap.SeqSet)
 	seqSet.AddRange(from, to)
 
+	fetch := []imap.FetchItem{imap.FetchEnvelope, imap.FetchUid, imap.FetchBodyStructure}
+
 	ch := make(chan *imap.Message, 10)
 	done := make(chan error, 1)
 	go func() {
-		done <- conn.Fetch(seqSet, []imap.FetchItem{imap.FetchEnvelope}, ch)
+		done <- conn.Fetch(seqSet, fetch, ch)
 	}()
 
-	msgs := make([]*imap.Message, 0, n)
+	msgs := make([]imapMessage, 0, n)
 	for msg := range ch {
-		msgs = append(msgs, msg)
+		msgs = append(msgs, imapMessage{msg})
 	}
 
 	if err := <-done; err != nil {
@@ -95,3 +178,59 @@ func listMessages(conn *imapclient.Client, mboxName string) ([]*imap.Message, er
 
 	return msgs, nil
 }
+
+var _ = message.Read
+
+func getMessage(conn *imapclient.Client, mboxName string, uid uint32, partPath []int) (*imap.Message, string, error) {
+	if err := ensureMailboxSelected(conn, mboxName); err != nil {
+		return nil, "", err
+	}
+
+	seqSet := new(imap.SeqSet)
+	seqSet.AddNum(uid)
+
+	var textHeaderSection imap.BodySectionName
+	textHeaderSection.Peek = true
+	textHeaderSection.Specifier = imap.HeaderSpecifier
+	textHeaderSection.Path = partPath
+
+	var textBodySection imap.BodySectionName
+	textBodySection.Peek = true
+	textBodySection.Path = partPath
+
+	fetch := []imap.FetchItem{
+		imap.FetchEnvelope,
+		imap.FetchUid,
+		imap.FetchBodyStructure,
+		textHeaderSection.FetchItem(),
+		textBodySection.FetchItem(),
+	}
+
+	ch := make(chan *imap.Message, 1)
+	if err := conn.UidFetch(seqSet, fetch, ch); err != nil {
+		return nil, "", err
+	}
+
+	msg := <-ch
+	if msg == nil {
+		return nil, "", fmt.Errorf("server didn't return message")
+	}
+
+	headerReader := bufio.NewReader(msg.GetBody(&textHeaderSection))
+	h, err := textproto.ReadHeader(headerReader)
+	if err != nil {
+		return nil, "", err
+	}
+
+	text, err := message.New(message.Header{h}, msg.GetBody(&textBodySection))
+	if err != nil {
+		return nil, "", err
+	}
+
+	b, err := ioutil.ReadAll(text.Body)
+	if err != nil {
+		return nil, "", err
+	}
+
+	return msg, string(b), nil
+}
diff --git a/public/mailbox.html b/public/mailbox.html
index efae0d9..282f462 100644
--- a/public/mailbox.html
+++ b/public/mailbox.html
@@ -2,6 +2,8 @@
 
 <h1>koushin</h1>
 
+<h2>{{.Mailbox.Name}}</h2>
+
 <p>Mailboxes:</p>
 <ul>
 	{{range .Mailboxes}}
@@ -12,7 +14,9 @@
 <p>Messages:</p>
 <ul>
 	{{range .Messages}}
-		<li>{{.Envelope.Subject}}</li>
+		<li><a href="/message/{{$.Mailbox.Name}}/{{.Uid}}?part={{.TextPartName}}">
+			{{.Envelope.Subject}}
+		</a></li>
 	{{end}}
 </ul>
 
diff --git a/server.go b/server.go
index 8245e08..86a1963 100644
--- a/server.go
+++ b/server.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"strconv"
+	"strings"
 	"time"
 
 	"github.com/labstack/echo/v4"
@@ -94,6 +96,34 @@ func handleLogin(ectx echo.Context) error {
 	return ctx.Render(http.StatusOK, "login.html", nil)
 }
 
+func parseUid(s string) (uint32, error) {
+	uid, err := strconv.ParseUint(s, 10, 32)
+	if err != nil {
+		return 0, err
+	}
+	if uid == 0 {
+		return 0, fmt.Errorf("UID must be non-zero")
+	}
+	return uint32(uid), nil
+}
+
+func parsePartPath(s string) ([]int, error) {
+	l := strings.Split(s, ".")
+	path := make([]int, len(l))
+	for i, s := range l {
+		var err error
+		path[i], err = strconv.Atoi(s)
+		if err != nil {
+			return nil, err
+		}
+
+		if path[i] <= 0 {
+			return nil, fmt.Errorf("part num must be strictly positive")
+		}
+	}
+	return path, nil
+}
+
 func New(imapURL string) *echo.Echo {
 	e := echo.New()
 
@@ -149,11 +179,37 @@ func New(imapURL string) *echo.Echo {
 		}
 
 		return ctx.Render(http.StatusOK, "mailbox.html", map[string]interface{}{
+			"Mailbox": ctx.conn.Mailbox(),
 			"Mailboxes": mailboxes,
 			"Messages": msgs,
 		})
 	})
 
+	e.GET("/message/:mbox/:uid", func(ectx echo.Context) error {
+		ctx := ectx.(*context)
+
+		uid, err := parseUid(ctx.Param("uid"))
+		if err != nil {
+			return echo.NewHTTPError(http.StatusBadRequest, err)
+		}
+		// TODO: handle messages without a text part
+		part, err := parsePartPath(ctx.QueryParam("part"))
+		if err != nil {
+			return echo.NewHTTPError(http.StatusBadRequest, err)
+		}
+
+		msg, body, err := getMessage(ctx.conn, ctx.Param("mbox"), uid, part)
+		if err != nil {
+			return err
+		}
+
+		return ctx.Render(http.StatusOK, "message.html", map[string]interface{}{
+			"Mailbox": ctx.conn.Mailbox(),
+			"Message": msg,
+			"Body": body,
+		})
+	})
+
 	e.GET("/login", handleLogin)
 	e.POST("/login", handleLogin)