#!/bin/sh
# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2022 Sxmo Contributors

# A pretty generic status content generator
# It aggregates all file content present in a folder
# It sorts file elements numerically by zero-padded priority prefix
# It watches file events to stdout new content

ROOT="${XDG_RUNTIME_DIR:-/run/user/10000}/sxmo_status/${SXMO_STATUS_NAME:-default}"
mkdir -p "$ROOT"

lock_ex() {
	:
}

lock_sh() {
	:
}

free() {
	:
}

usage() {
	printf "Usage: %s [ACTIONS]\n" "${0##*/}" >&2
	printf "ACTIONS:\n" >&2
	printf "	-s: the status content (default action)\n" >&2
	printf "	-w: file events and stdout status content\n" >&2
	printf "	-a <id> <priority> <content>: add a bar component\n" >&2
	printf "	-d <id>: remove a bar component\n" >&2
	printf "	-r: remove all bar components\n" >&2
	printf "	-D: the status content explained\n" >&2
	printf "	-h: this message\n" >&2
}

add() {
	id=
	priority=
	value=

	while [ "$#" -gt 0 ]; do
		arg="$1"
		shift

		case "$arg" in
			"-f"|"-b"|"-t"|"-e"|"-o")
				[ "$#" -gt 0 ] && shift
				;;
			*)
				if [ -z "$id" ]; then
					id="$arg"
				elif [ -z "$priority" ]; then
					priority="$arg"
				elif [ -z "$value" ]; then
					value="$arg"
				fi
				;;
		esac
	done

	if [ -z "$id" ] || [ -z "$priority" ]; then
		printf "usage: %s -a <id> <priority> <value>\n" "${0##*/}" >&2
		exit 1
	fi

	mkdir -p "$ROOT"
	padded_prio="$(printf '%03d' "$priority" 2>/dev/null || printf '%s' "$priority")"
	target="$ROOT/$padded_prio-$id"

	lock_ex

	# Remove any old file for this id with a different priority prefix
	for f in "$ROOT"/*-"$id"; do
		[ -e "$f" ] || continue
		if [ "$f" != "$target" ]; then
			rm -f "$f"
		fi
	done

	if [ -z "$value" ]; then
		rm -f "$target"
		free
		return
	fi

	if [ -r "$target" ]; then
		old_val=""
		read -r old_val < "$target" 2>/dev/null || true
		if [ "$old_val" = "$value" ]; then
			free
			return
		fi
	fi

	printf "%s\n" "$value" > "${XDG_RUNTIME_DIR:-/run/user/10000}/sxmo_status/.tmp.$$"
	mv -f "${XDG_RUNTIME_DIR:-/run/user/10000}/sxmo_status/.tmp.$$" "$target"

	free
}

del() {
	id="$1"
	if [ -z "$id" ]; then
		printf "usage: %s -d <id>\n" "${0##*/}" >&2
		exit 1
	fi

	lock_ex
	for f in "$ROOT"/*-"$id"; do
		[ -e "$f" ] || continue
		rm -f "$f"
	done
	free
}

show() {
	lock_sh
	out=""
	for f in "$ROOT"/*; do
		[ -f "$f" ] || continue
		val=""
		read -r val < "$f" 2>/dev/null || true
		[ -n "$val" ] || continue
		if [ -z "$out" ]; then
			out="$val"
		else
			out="$out $val"
		fi
	done
	printf "%s\n" "$out"
	free
}

debug() {
	lock_sh
	for f in "$ROOT"/*; do
		[ -f "$f" ] || continue
		val=""
		read -r val < "$f" 2>/dev/null || true
		printf "%s\n>%s<\n" "${f##*/}" "$val"
	done
	free
}

watch() {
	FIFO="$(mktemp -u)"
	mkfifo "$FIFO"
	NOTIFYPID=

	# shellcheck disable=SC2317
	finish() {
		[ -n "$NOTIFYPID" ] && kill "$NOTIFYPID" 2>/dev/null || true
		rm -f "$FIFO"
		exit 0
	}
	trap 'finish' TERM INT

	while true; do
		mkdir -p "$ROOT"
		inotifywait -mq -e "close_write,move,delete,delete_self,move_self" "$ROOT" >> "$FIFO" &
		NOTIFYPID=$!

		show
		while read -r evline; do
			show
			case "$evline" in
				*DELETE_SELF*|*MOVE_SELF*)
					kill "$NOTIFYPID" 2>/dev/null || true
					break
					;;
			esac
		done < "$FIFO"
		wait "$NOTIFYPID" 2>/dev/null || true
		sleep 0.1
	done
}

reset() {
	lock_ex
	mkdir -p "$ROOT"
	rm -f "$ROOT"/*
	free
}

action=""
while [ "$#" -gt 0 ]; do
	case "$1" in
		"-o")
			shift 2 2>/dev/null || shift
			;;
		"-s"|"-w"|"-r"|"-a"|"-d"|"-D"|"-h")
			action="$1"
			shift
			break
			;;
		*)
			action="$1"
			shift
			break
			;;
	esac
done

case "$action" in
	""|"-s") show ;;
	"-w") watch "$@" ;;
	"-r") reset "$@" ;;
	"-a") add "$@" ;;
	"-d") del "$@" ;;
	"-D") debug "$@" ;;
	"-h") usage ;;
esac