#!/bin/sh /etc/rc.common
# Keeps the scheduled-measurement cron entry in step with UCI. There is no
# daemon here: measurements are one-shot runs of librespeed-run, and the rpcd
# interface needs no service of its own.

START=95
USE_PROCD=1

CRONTAB=/etc/crontabs/root
RUN=/usr/libexec/librespeed-run
AGG=/usr/libexec/librespeed-aggregate

# Builds the cron time fields from UCI. For sub-daily intervals `hours`
# restricts when measurements may run; for a daily one it is the window a
# random time is drawn from, drawn here at sync time. That keeps the herd
# apart -- every router lands on its own minute -- without any process
# sleeping through the night, at the cost of re-drawing on every reload.
# Every comma-separated part must be a number or an ascending range within
# [0, max]; the caller already reduced the alphabet to digits, commas and
# dashes.
valid_field() {
	local val="$1" max="$2" part a b oifs="$IFS"
	IFS=','
	for part in $val; do
		IFS="$oifs"
		a=${part%-*}; b=${part#*-}
		# Each half on its own: concatenated, '5-' and '-5' hide their empty
		# side and the arithmetic below would print a shell error where the
		# caller promises a silent fallback.
		case "$a" in ''|*[!0-9]*) return 1 ;; esac
		case "$b" in ''|*[!0-9]*) return 1 ;; esac
		[ "$a" -le "$max" ] && [ "$b" -le "$max" ] && [ "$a" -le "$b" ] || return 1
	done
	IFS="$oifs"
	return 0
}

cron_expr() {
	local interval="$1" days="$2" hours="$3"
	local start end m h v

	case "$interval" in
	*m)
		v=${interval%m}
		case "$v" in ''|0|*[!0-9]*) return 1 ;; esac
		[ "$v" -le 59 ] || return 1
		echo "*/$v ${hours:-*} * * $days"
		;;
	*h)
		v=${interval%h}
		case "$v" in ''|0|*[!0-9]*) return 1 ;; esac
		[ "$v" -le 23 ] || return 1
		if [ -n "$hours" ]; then
			echo "0 $hours/$v * * $days"
		else
			echo "0 */$v * * $days"
		fi
		;;
	1d|24h)
		start=${hours%-*}; end=${hours#*-}
		[ -n "$hours" ] || { start=0; end=23; }
		# A window wrapping midnight (22-4) is not supported; treat it as the
		# single starting hour rather than guessing.
		[ "$end" -ge "$start" ] 2>/dev/null || end=$start
		# Time xor pid as the seed: seconds-granular srand() alone would give
		# two syncs in the same second the same draw.
		set -- $(awk -v a="$start" -v b="$end" -v s="$(( $(date +%s) ^ $$ ))" 'BEGIN {
			srand(s)
			printf "%d %d", int(rand() * 60), a + int(rand() * (b - a + 1))
		}')
		echo "$1 $2 * * $days"
		;;
	*)
		return 1
		;;
	esac
}

restart_cron() {
	# Unconditional: on a stock system the crontab dir starts empty, so crond
	# is not running at all -- restart starts a stopped procd service, and a
	# guard on "running" would mean the schedule never fires until reboot.
	/etc/init.d/cron restart >/dev/null 2>&1
	return 0
}

sync_cron() {
	local enabled interval days hours expr hist_enabled archive_path

	config_load librespeed
	config_get_bool enabled schedule enabled 0
	config_get interval schedule interval 1d
	config_get days schedule days '*'
	config_get hours schedule hours ''
	config_get_bool hist_enabled history enabled 1
	config_get archive_path history archive_path ''

	# These end up verbatim in root's crontab, so anything unexpected becomes
	# the harmless default rather than a cron field it was not meant to be.
	# Values are checked as well as characters: '99' is made of digits, but
	# as an hour it would turn a daily schedule into an hourly one.
	case "$days" in *[!0-9,-]*|'') days='*' ;; esac
	if [ "$days" != '*' ] && ! valid_field "$days" 6; then
		days='*'
	fi
	case "$hours" in *[!0-9-]*) hours='' ;; esac
	if [ -n "$hours" ] && ! valid_field "$hours" 23; then
		hours=''
	fi

	mkdir -p "${CRONTAB%/*}"
	touch "$CRONTAB"
	sed -i "\\#$RUN#d;\\#$AGG#d" "$CRONTAB"

	# The day completes at midnight; five past, it is reduced to one archive
	# line. A missed run costs nothing to catch up: raw lives in RAM, so after
	# a power cut there is nothing left to aggregate anyway.
	if [ "$hist_enabled" = 1 ] && [ -n "$archive_path" ]; then
		echo "5 0 * * * $AGG" >> "$CRONTAB"
	fi

	if [ "$enabled" = 1 ]; then
		if expr=$(cron_expr "$interval" "$days" "$hours"); then
			echo "$expr $RUN" >> "$CRONTAB"
		else
			logger -t librespeed "unsupported schedule interval '$interval'"
		fi
	fi

	restart_cron
}

start_service() {
	sync_cron
}

stop_service() {
	sed -i "\\#$RUN#d;\\#$AGG#d" "$CRONTAB"
	restart_cron
}

service_triggers() {
	procd_add_reload_trigger "librespeed"
}

reload_service() {
	sync_cron
}