From 0897413a3e7b7707e6e597077d1621e586180f3b Mon Sep 17 00:00:00 2001
From: Drew DeVault <sir@cmpwn.com>
Date: Mon, 20 May 2019 16:49:39 -0400
Subject: [PATCH] Implement :next-part, :prev-part

---
 commands/msgview/next-part.go | 43 +++++++++++++++++++++++++++++++++++
 config/binds.conf             |  2 ++
 widgets/msgviewer.go          | 33 +++++++++++++++++++++++++--
 3 files changed, 76 insertions(+), 2 deletions(-)
 create mode 100644 commands/msgview/next-part.go

diff --git a/commands/msgview/next-part.go b/commands/msgview/next-part.go
new file mode 100644
index 0000000..fcf8f19
--- /dev/null
+++ b/commands/msgview/next-part.go
@@ -0,0 +1,43 @@
+package msgview
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+
+	"git.sr.ht/~sircmpwn/aerc/widgets"
+)
+
+func init() {
+	register("next-part", NextPrevPart)
+	register("prev-part", NextPrevPart)
+}
+
+func nextPrevPartUsage(cmd string) error {
+	return errors.New(fmt.Sprintf("Usage: %s [n]", cmd))
+}
+
+func NextPrevPart(aerc *widgets.Aerc, args []string) error {
+	if len(args) > 2 {
+		return nextPrevPartUsage(args[0])
+	}
+	var (
+		n   int = 1
+		err error
+	)
+	if len(args) > 1 {
+		n, err = strconv.Atoi(args[1])
+		if err != nil {
+			return nextPrevPartUsage(args[0])
+		}
+	}
+	mv, _ := aerc.SelectedTab().(*widgets.MessageViewer)
+	for ; n > 0; n-- {
+		if args[0] == "prev-part" {
+			mv.PreviousPart()
+		} else {
+			mv.NextPart()
+		}
+	}
+	return nil
+}
diff --git a/config/binds.conf b/config/binds.conf
index 058b2d0..1f049a4 100644
--- a/config/binds.conf
+++ b/config/binds.conf
@@ -47,6 +47,8 @@ rr = :reply<Enter>
 rq = :reply -q<Enter>
 Rr = :reply -a<Enter>
 Rq = :reply -aq<Enter>
+<C-k> = :prev-part<Enter>
+<C-j> = :next-part<Enter>
 
 [compose]
 # Keybindings used when the embedded terminal is not selected in the compose
diff --git a/widgets/msgviewer.go b/widgets/msgviewer.go
index ab79b5e..64762f7 100644
--- a/widgets/msgviewer.go
+++ b/widgets/msgviewer.go
@@ -119,12 +119,13 @@ func NewMessageViewer(conf *config.AercConfig,
 		if err != nil {
 			goto handle_error
 		}
+		switcher.selected = -1
 		for i, pv := range switcher.parts {
 			pv.OnInvalidate(func(_ ui.Drawable) {
 				switcher.Invalidate()
 			})
 			// TODO: switch to user's preferred mimetype, if configured
-			if switcher.selected == 0 && pv.part.MIMEType != "multipart" {
+			if switcher.selected == -1 && pv.part.MIMEType != "multipart" {
 				switcher.selected = i
 			}
 		}
@@ -198,6 +199,34 @@ func (mv *MessageViewer) OnInvalidate(fn func(d ui.Drawable)) {
 	})
 }
 
+func (mv *MessageViewer) PreviousPart() {
+	switcher := mv.switcher
+	for {
+		switcher.selected--
+		if switcher.selected < 0 {
+			switcher.selected = len(switcher.parts) - 1
+		}
+		if switcher.parts[switcher.selected].part.MIMEType != "multipart" {
+			break
+		}
+	}
+	mv.Invalidate()
+}
+
+func (mv *MessageViewer) NextPart() {
+	switcher := mv.switcher
+	for {
+		switcher.selected++
+		if switcher.selected >= len(switcher.parts) {
+			switcher.selected = 0
+		}
+		if switcher.parts[switcher.selected].part.MIMEType != "multipart" {
+			break
+		}
+	}
+	mv.Invalidate()
+}
+
 func (ps *PartSwitcher) Invalidate() {
 	ps.DoInvalidate(ps)
 }
@@ -318,7 +347,7 @@ func NewPartViewer(conf *config.AercConfig,
 
 	pv := &PartViewer{
 		filter:  filter,
-		index:   index, // TODO: Nested multipart does indicies differently
+		index:   index,
 		msg:     msg,
 		pager:   pager,
 		pagerin: pagerin,