Use imap.BodyStructure.Filename and imap.Address.Address

The former fixes encoding issues in filenames. The latter is just for
brevity.

go.mod

@@ -3,7 +3,7 @@ module git.sr.ht/~emersion/koushin
 go 1.13
 
 require (
-	github.com/emersion/go-imap v1.0.1
+	github.com/emersion/go-imap v1.0.3-0.20191208103636-6388a8c8bfdb
 	github.com/emersion/go-message v0.10.8
 	github.com/emersion/go-sasl v0.0.0-20190817083125-240c8404624e
 	github.com/emersion/go-smtp v0.12.0

go.sum

@@ -5,6 +5,8 @@ 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-imap v1.0.3-0.20191208103636-6388a8c8bfdb h1:WSeLbrNhAgjH21BVHUqtfhwX4Rnr31rvMi0Us6m5iWg=
+github.com/emersion/go-imap v1.0.3-0.20191208103636-6388a8c8bfdb/go.mod h1:TjT+1ncDso8j/VXeUHcZeQknho5hjyQLqEIybJJjjDI=
 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-message v0.10.8 h1:1l1Vb+0By9U1ITTH3FgKfJQWQ9sTI3N1smPe6SS3QXY=

handlers.go

@@ -229,7 +229,7 @@ func handleCompose(ectx echo.Context) error {
 		if len(replyTo) > 0 {
 			msg.To = make([]string, len(replyTo))
 			for i, to := range replyTo {
-				msg.To[i] = to.MailboxName + "@" + to.HostName
+				msg.To[i] = to.Address()
 			}
 		}
 		msg.Subject = inReplyTo.Envelope.Subject

imap.go

@@ -174,10 +174,7 @@ func imapPartTree(bs *imap.BodyStructure, path []int) *IMAPPartNode {
 		path = []int{1}
 	}
 
-	var filename string
-	if strings.EqualFold(bs.Disposition, "attachment") {
-		filename = bs.DispositionParams["filename"]
-	}
+	filename, _ := bs.Filename()
 
 	node := &IMAPPartNode{
 		Path:     path,