#!/bin/bash

# This is a simple mirroring script. To save bandwidth it first checks a
# timestamp via HTTP and only runs rsync when the timestamp differs from the
# local copy. As of 2016, a single rsync run without changes transfers roughly
# 6MiB of data which adds up to roughly 250GiB of traffic per month when rsync
# is run every minute. Performing a simple check via HTTP first can thus save a
# lot of traffic.

target="/srv/repo"
tmp="/srv/tmp"
lock="/var/lock/syncrepo.lck"

# NOTE: You'll probably want to change this or set it to 0 to disable the limit
# The default unit is KiB (see man rsync /--bwlimit for more)
bwlimit=4096

# NOTE: Most people reading this very likely need to change this since
# rsync.archlinux.org requires you to be a tier 1 mirror
source='rsync://rsync.archlinux.org/ftp_tier1'
lastupdate_url='http://rsync.archlinux.org/lastupdate'

#### END CONFIG

[ ! -d "${target}" ] && mkdir -p "${target}"
[ ! -d "${tmp}" ] && mkdir -p "${tmp}"

exec 9>"${lock}"
flock -n 9 || exit

rsync_cmd() {
	local -a cmd=(rsync -rtlH --safe-links --delete-after ${VERBOSE} "--timeout=600" "--contimeout=60" -p \
		--delay-updates --no-motd "--temp-dir=${tmp}")

	if stty &>/dev/null; then
		cmd+=(-h -v --progress)
	fi

	if ((bwlimit>0)); then
		cmd+=("--bwlimit=$bwlimit")
	fi

	"${cmd[@]}" "$@"
}


# if we are called without a tty (cronjob) only run when there are changes
if ! tty -s && [[ -f "$target/lastupdate" ]] && diff -b <(curl -s "$lastupdate_url") "$target/lastupdate" >/dev/null; then
	# keep lastsync file in sync for statistics generated by the Arch Linux website
	rsync_cmd "$source/lastsync" "$target/lastsync"
	exit 0
fi

rsync_cmd \
	--exclude='*.links.tar.gz*' \
	--exclude='/other' \
	--exclude='/sources' \
	--exclude='/iso' \
	"${source}" \
	"${target}"

#echo "Last sync was $(date -d @$(cat ${target}/lastsync))"