open: allow overriding default program

Instead of xdg-open (or open on MacOS), allow forcing a program to open
a message part. The program is determined in that order of priority:

1) If :open has arguments, they will be used as command to open the
   attachment. If the arguments contain the {} placeholder, the
   temporary file will be substituted, otherwise the file path is added
   at the end of the arguments.

2) If a command is specified in the [openers] section of aerc.conf for
   the part MIME type, then it is used with the same rules of {}
   substitution.

3) Finally, fallback to xdg-open/open with the file path as argument.

Update the docs and default config accordingly with examples.

Fixes: https://todo.sr.ht/~rjarry/aerc/64
Co-authored-by: Jason Stewart <support@eggplantsd.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Moritz Poldrack <moritz@poldrack.dev>

1 files changed, 36 insertions, 4 deletions

diff --git a/lib/open.go b/lib/open.go
index a189980a..e091d913 100644
--- a/lib/open.go
+++ b/lib/open.go
@@ -4,16 +4,48 @@ import (
 	"fmt"
 	"os/exec"
 	"runtime"
+	"strings"
 
 	"git.sr.ht/~rjarry/aerc/logging"
 )
 
 func XDGOpen(uri string) error {
-	openBin := "xdg-open"
-	if runtime.GOOS == "darwin" {
-		openBin = "open"
+	return XDGOpenMime(uri, "", nil, nil)
+}
+
+func XDGOpenMime(
+	uri string, mimeType string,
+	openers map[string][]string, args []string,
+) error {
+	if len(args) == 0 {
+		// no explicit command provided, lookup opener from mime type
+		opener, ok := openers[mimeType]
+		if ok {
+			args = opener
+		} else {
+			// no opener defined in config, fallback to default
+			if runtime.GOOS == "darwin" {
+				args = append(args, "open")
+			} else {
+				args = append(args, "xdg-open")
+			}
+		}
+	}
+
+	i := 0
+	for ; i < len(args); i++ {
+		if strings.Contains(args[i], "{}") {
+			break
+		}
+	}
+	if i < len(args) {
+		// found {} placeholder in args, replace with uri
+		args[i] = strings.Replace(args[i], "{}", uri, 1)
+	} else {
+		// no {} placeholder in args, add uri at the end
+		args = append(args, uri)
 	}
-	args := []string{openBin, uri}
+
 	logging.Infof("running command: %v", args)
 	cmd := exec.Command(args[0], args[1:]...)
 	out, err := cmd.CombinedOutput()