composer: add message preview

Add message preview to the composer. Add preview option to the review
window. Open the message in a message viewer before sending to check the
headers and attachments.

Implements: https://todo.sr.ht/~rjarry/aerc/86
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

5 files changed, 25 insertions, 8 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 43aa30c4..f0ad50d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Display threads from bottom to top with `reverse-thread-order=true` in
   `aerc.conf`.
 - Style search results in the message list with `msglist_result.*`
+- Preview messages with their attachments before sending with `:preview`
 
 ### Fixed
 
diff --git a/commands/eml.go b/commands/eml.go
index 45dd4f25..864145ce 100644
--- a/commands/eml.go
+++ b/commands/eml.go
@@ -1,6 +1,7 @@
 package commands
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -17,7 +18,7 @@ func init() {
 }
 
 func (Eml) Aliases() []string {
-	return []string{"eml"}
+	return []string{"eml", "preview"}
 }
 
 func (Eml) Complete(aerc *widgets.Aerc, args []string) []string {
@@ -54,6 +55,16 @@ func (Eml) Execute(aerc *widgets.Aerc, args []string) error {
 		case *widgets.MessageViewer:
 			part := tab.SelectedMessagePart()
 			tab.MessageView().FetchBodyPart(part.Index, showEml)
+		case *widgets.Composer:
+			var buf bytes.Buffer
+			h, err := tab.PrepareHeader()
+			if err != nil {
+				return err
+			}
+			if err := tab.WriteMessage(h, &buf); err != nil {
+				return err
+			}
+			showEml(&buf)
 		default:
 			return fmt.Errorf("unsupported operation")
 		}
diff --git a/config/binds.conf b/config/binds.conf
index 9e23ab91..ff067e56 100644
--- a/config/binds.conf
+++ b/config/binds.conf
@@ -113,6 +113,7 @@ $ex = <C-x>
 # Keybindings used when reviewing a message to be sent
 y = :send<Enter>
 n = :abort<Enter>
+v = :preview<Enter>
 p = :postpone<Enter>
 q = :choose -o d discard abort -o p postpone postpone<Enter>
 e = :edit<Enter>
diff --git a/doc/aerc.1.scd b/doc/aerc.1.scd
index 2c062816..9fe1dd59 100644
--- a/doc/aerc.1.scd
+++ b/doc/aerc.1.scd
@@ -83,9 +83,11 @@ These commands work in any context.
 	*Note*: commands executed in this way are not executed with the shell.
 
 *eml* [<path>]
+*preview*
 	Opens an eml file and displays the message in the message viewer.
 
-	Can also be used in the message viewer to open an rfc822 attachment.
+	Can also be used in the message viewer to open an rfc822 attachment or
+	in the composer to preview the message.
 
 *pwd*
 	Displays aerc's current working directory in the status bar.
diff --git a/widgets/compose.go b/widgets/compose.go
index c3f396bd..ca7c8b8f 100644
--- a/widgets/compose.go
+++ b/widgets/compose.go
@@ -681,13 +681,14 @@ func (c *Composer) PrepareHeader() (*mail.Header, error) {
 			return nil, err
 		}
 	}
-	if !c.header.Has("Date") {
-		if c.acctConfig.SendAsUTC {
-			c.header.SetDate(time.Now().UTC())
-		} else {
-			c.header.SetDate(time.Now())
-		}
+
+	// update the "Date" header every time PrepareHeader is called
+	if c.acctConfig.SendAsUTC {
+		c.header.SetDate(time.Now().UTC())
+	} else {
+		c.header.SetDate(time.Now())
 	}
+
 	return c.header, nil
 }
 
@@ -1244,6 +1245,7 @@ var reviewCommands = [][]string{
 	{":attach<space>", "Add attachment"},
 	{":detach<space>", "Remove attachment"},
 	{":postpone<enter>", "Postpone"},
+	{":preview<enter>", "Preview message"},
 	{":abort<enter>", "Abort (discard message, no confirmation)"},
 	{":choose -o d discard abort -o p postpone postpone<enter>", "Abort or postpone"},
 }