POSIX sh mako menu selection, without jq

LICENSE

MIT License

Copyright (c) 2019 xPMo

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of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
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SOFTWARE.

mako-menu.sh

#!/bin/sh
# arguments: program [ args ]
# example: ./mako-menu.sh fzf --prompt='Select action: '
#          ./mako-menu.sh rofi -dmenu -p 'Select action: '

# The expansion "$@" is the only POSIX expansion which
# expands to a list and doesn't mangle spaces or quotes.
# We use a one-time function to use multiple lists.

if [ $# -eq 0 ]; then
	echo >&2 \
	"$0: No program provided.

Usage:    $0 [program] [[args]]

The list of actions will be provided to the program
on stdin, separated by newlines. The program should
print to stdout exactly one action.

Examples: $0 fzf --prompt='Select action: '
          $0 rofi -dmenu -p 'Select action: '
          $0 wofi -dp 'Select action: '
"
	exit 1
fi

# Get current notification
# list is quoted, and will contain multiple actions
# the first action is the most recent that is currently shown
busctl_list="$(busctl --user call org.freedesktop.Notifications /fr/emersion/Mako \
	fr.emersion.Mako ListNotifications)"

case $busctl_list in
	*'"actions" a{ss} 0 '*)
		echo >&2 "$0: No actions found."
		exit 1 ;;
	*'"actions" a{ss}'*) :;;
	*)
		echo >&2 "$0: No notification found."
		exit 1 ;;
esac

# get notification id in case another notification appears
# while the user is selecting an action
# ... "id" u [id] ...
id="${busctl_list#*' "id" u '}"
id="${id%% *}"

# strip head of busctl_list to actions
# ... "actions" a{ss} [count] "key" "value" "key" "value" ...
busctl_list="${busctl_list#*' "actions" a{ss} '}"
action_count="${busctl_list%% *}"
# remove action_count from front, escape all '$' and '`'
busctl_list="$(printf '%s' "${busctl_list#* }" | sed 's/[\$`]/\\&/g')"

# Build newline-separated action list
join_actions(){
	eval set -- "$1"
	i=0
	while [ $((i += 1)) -le "$action_count" ]; do
		# key is $1, val is $2
		value_list="$(printf '%s\n%s' "$2" "$value_list")"
		# shift to next key-val pair
		shift 2
	done
}
join_actions "$busctl_list"

# Call user's program
selected_value="$(printf '%s' "$value_list" | "$@")"

# Test selected value against possible values
eval set -- "$busctl_list"
i=0
while [ $((i += 1)) -le "$action_count" ]; do
	# key is $1, val is $2
	if [ "$2" = "$selected_value" ]; then
		# The key may contain C escape sequences, use printf %b to evaluate them.
		# Since sh removes trailing newlines in command substitutions,
		# we append an extra character to suppress this behaviour.
		selected_key="$(printf '%b:' "$1")"
		exec busctl --user call org.freedesktop.Notifications /fr/emersion/Mako \
			fr.emersion.Mako InvokeAction us "$id" "${selected_key%?}"
	fi
	# shift to next key-val pair
	shift 2
done

echo >&2 "$0: No action selected."
exit 1
# vim: foldmethod=marker