_polybar_config_file() {
	local config_path=${XDG_CONFIG_HOME:-$HOME/.config}/polybar/config

	for ((i = 0; i < COMP_CWORD; i++)); do
		case ${COMP_WORDS[i]} in
		--config)
			config_path=${COMP_WORDS[i + 2]}
			break
			;;
		-c)
			config_path=${COMP_WORDS[i + 1]}
			break
			;;
		esac
	done

	# Use eval + cd for to get bash's parameter/tilde expansion etc
	(eval cd $(dirname "$config_path"); echo $PWD/$(basename "$config_path"))
}

_polybar_bars() {
	local config_file=$(_polybar_config_file)

	if [ -r "$config_file" ]; then
		grep -Po '\[bar/\K(.*)(?=\])' "$config_file"
	fi
}

_polybar() {
	local options='-h --help
	               -v --version
	               -l --log=
	               -q --quiet
	               -c --config=
	               -r --reload
	               -d --dump=
	               -m --list-monitors
	               -w --print-wmname
	               -s --stdout
	               -p --png='

	local log_levels='error
	                  warning
	                  info
	                  trace'

	COMPREPLY=()

	local cur=${COMP_WORDS[COMP_CWORD]}
	case "$cur" in
	-*)
		COMPREPLY=( $(compgen -W "$options" -- "$cur") )
		;;
	*)
		local prev=${COMP_WORDS[COMP_CWORD - 1]}
		if [ "$prev" = "=" ]; then
			prev=${COMP_WORDS[COMP_CWORD - 2]}
		fi

		case "$prev" in
		-l|--log)
			COMPREPLY=( $(compgen -W "$log_levels" -- "$cur") )
			return 0
			;;
		-c|--config)
			COMPREPLY=( $(compgen -f "$cur") )
			return 0
			;;
		-p|--png)
			COMPREPLY=( $(compgen -f -X "!*.png" "$cur") )
			return 0
			;;
		# TODO: read properties of the selected bar from config
		-d|--dump)
			return 0
			;;
		*)
			COMPREPLY=( $(compgen -W "$options $(_polybar_bars)" -- "$cur") )
			;;
		esac
	esac

	for ((i = 0; i < ${#COMPREPLY[@]}; i++)); do
		case ${COMPREPLY[i]} in
		--*=) ;;
		-*) COMPREPLY[i]+=" "
		esac
	done

	return 0
}

complete -o filenames -o noquote -o nospace -F _polybar polybar