flavours: Call bemenu selection from wrapper function

If we call the listing and applying function directly we either select a
random colorscheme on *no* selection or we have to make use of either
xargs GNU functionality or something like moreutils ifne to only select
color schemes on selection.

Can additionally set a random theme (if selection is 'random') or a
random light theme (if selection is 'light').

desktop/.config/river/init

@@ -71,7 +71,7 @@ riverctl map normal $mod+Shift T spawn "bemenu-translate"
 
 # Desktop theming
 # shellcheck disable=SC2016
-riverctl map normal $mod+Shift S spawn 'flavours list -l | bemenu | xargs flavours apply'
+riverctl map normal $mod+Shift S spawn 'flavourchoose'
 
 # Password dropdown frontend
 riverctl map normal $mod+Shift P spawn "pass-pick"

desktop/.local/bin/flavourchoose

@@ -0,0 +1,26 @@
+#!/usr/bin/env sh
+
+picker=dmenu
+if exist bemenu; then
+    picker=bemenu
+elif exist wofi; then
+    picker=wofi
+elif exist rofi; then
+    picker=rofi
+fi
+
+list=$(flavours list -l)
+flavour=$(printf "%s\nrandom\nlight" "$list" | "$picker")
+if [ -z "$flavour" ]; then
+    return
+elif [ "$flavour" = "random" ]; then
+    flavours apply '*'
+elif [ "$flavour" = "light" ]; then
+    flavours apply '*light'
+else
+    flavours apply "$flavour"
+fi
+
+if [ "$1" = '-v' ]; then
+    notify-send "Theme set" "set to: $flavour"
+fi