#!/bin/bash

# try to load the sleep builtin dynamically, because otherwise there's
# a *lot* of overhead (in terms of PID count)
if [[ $(</proc/cmdline) = *"nixos-system"* ]]; then
	enable -f /run/current-system/sw/lib/bash/sleep sleep
else
	enable -f /lib/bash/sleep sleep
fi

get_schedule_info () {
	if [ -z "$schedule_state" ]; then
		schedule_state="needs_init"
	fi

	case "$schedule_state" in
		"needs_init")
			readarray -t lines < <(
				khal list today 1d --format '{categories}|{title}|{start-time}|{end-time}' |
					grep '^school.*' |
					sed 's/school|//g'
			)

			# calculate the start-of-date time without shelling out to the date utility
			printf -v unix '%(%s)T'
			printf -v hours '%(%H)T'
			printf -v mins '%(%M)T'
			printf -v seconds '%(%S)T'
			hours=$((10#$hours))
			mins=$((10#$mins))
			seconds=$((10#$seconds))
			today_offset=$((hours * 60 * 60 + mins * 60 + seconds))
			today=$((unix - today_offset))

			for ((i=0; i < ${#lines[@]}; i++)); do
				readarray -t -d'|' line <<<"${lines[i]}"
				class_names+=("${line[0]}")
				starts=${line[1]}
				ends=${line[2]}

				# convert to unix time
				class_starts_hours=${starts%%:*}
				class_starts_hours=$((10#$class_starts_hours))
				class_starts_hours=$((class_starts_hours * 3600))
				class_starts_minutes=${starts##*:}
				class_starts_minutes=$((10#$class_starts_minutes))
				class_starts_minutes=$((class_starts_minutes * 60))
				class_starts_offset=$((class_starts_hours + class_starts_minutes))
				class_starts_final=$((today + class_starts_offset))

				class_ends_hours=${ends%%:*}
				class_ends_hours=$((10#$class_ends_hours))
				class_ends_hours=$((class_ends_hours * 3600))
				class_ends_minutes=${ends##*:}
				class_ends_minutes=$((10#$class_ends_minutes))
				class_ends_minutes=$((class_ends_minutes * 60))
				class_ends_offset=$((class_ends_hours + class_ends_minutes))
				class_ends_final=$((today + class_ends_offset))

				class_starts+=("$class_starts_final")
				class_ends+=("$class_ends_final")
			done

			schedule_state="needs_recalc"
			;;
		"needs_recalc")
			schedule_enabled="no"
			printf -v ctime '%(%s)T' -1
			for ((i=0; i < ${#class_names[@]}; i++)); do
				if [ $ctime -lt ${class_starts[$i]} ] && [ $ctime -gt ${class_ends[$(($i - 1))]} ]; then
					class_secs_left=$((${class_starts[$i]} - $ctime))
					current_class_until_event="$class_secs_left"
					current_class_name="${class_names[$i]}"
					current_class_status="waiting"
					schedule_enabled="yes"
				elif [ $ctime -gt ${class_starts[$i]} ] && [ $ctime -lt ${class_ends[$i]} ]; then
					class_secs_left=$((${class_ends[$i]} - $ctime))
					current_class_until_event="$class_secs_left"
					current_class_name="${class_names[$i]}"
					current_class_status="inside"
					schedule_enabled="yes"
				fi
			done

			if [ "$schedule_enabled" = "no" ]; then
				current_class_status="finished"
			fi

			schedule_state="needs_dec"
			;;
		"needs_dec")
			if [ "$current_class_status" = "inside" ]; then
				if [ "$((current_class_until_event / 60))" -le 5 ]; then
					printf -v schedule_status "%02d:%02d left in %s/" "$((current_class_until_event / 60))" "$((current_class_until_event % 60))" "$current_class_name"
				else
					printf -v schedule_status "%s minutes left in %s/" "$((current_class_until_event / 60))" "$current_class_name"
				fi
			elif [ "$current_class_status" = "outside" ]; then
				if [ "$((current_class_until_event / 60))" -le 5 ]; then
					printf -v schedule_status "%02d:%02d until %s/" "$((current_class_until_event / 60))" "$((current_class_until_event % 60))" "$current_class_name"
				else
					printf -v schedule_status "%s minutes until %s/" "$((current_class_until_event / 60))" "$current_class_name"
				fi
			elif [ "$current_class_status" = "finished" ]; then
				printf -v schedule_status ""
				return
			fi

			current_class_until_event=$((current_class_until_event - 1))
			if [ "$current_class_until_event" -eq 0 ]; then
				schedule_state="needs_recalc"
			fi
			;;
	esac
}

get_loadavg_info () {
	loadavg_status="$(</proc/loadavg)/"
}

get_cmus_info () {
	if [ /dev/shm/status/cmus -nt /dev/shm/status/modified ]; then
		cmus_status="$(</dev/shm/status/cmus)/"
		touch /dev/shm/status/modified
	fi
}

get_days_until_21 () {
	if [ -z "$birthday" ]; then
		birthday=$(cat ~/.config/birthdate)
		twenty_one=$((birthday + (21 * 365 * 24 * 60 * 60)))
	fi

	printf -v now "%(%s)T"

	days_until_21_status=$(((twenty_one - now) / 24 / 60 / 60))
	days_until_21_status="$days_until_21_status/"
}

get_battery_info () {
	battery_status=$(</sys/class/power_supply/BAT0/capacity)
}

get_time_info () {
	printf -v date_status '%(%d(%a)-%m(%b)-%y)T %(%H)T:%(%M)T:%(%S)T/' -1
}

while true; do
	# use /dev/shm to minimize the amount of i/o on disk
	if [ ! -d /dev/shm/status ]; then
		mkdir -p /dev/shm/status
		touch /dev/shm/status/modified
	fi

	get_time_info
	get_loadavg_info
	get_days_until_21
	get_battery_info
	get_cmus_info
	get_schedule_info

	printf "%s%s%s%s%s%s\n" "$schedule_status" "$cmus_status" "$loadavg_status" "$days_until_21_status" "$date_status" "$battery_status"
	sleep 1
done | dwm-setstatus