#! /bin/sh
set -e

OLDIFS="$IFS"
NL="
"

SOURCES_LIST=$1
SUITE=$2
OTHER_SUITES=$3
UDEB_COMPONENTS=$4
USE_PROPOSED_UPDATES=$5 # optional

# Set to 1 or 2 to see increasing debug info about mirror tests
# Use 0 for quiet (normal) operation
VERBOSE=0

test_url() {
	local url=$1
	if [ $VERBOSE -ge 1 ]; then
		echo "DEBUG: testing 'wget --spider $url'" >&2
	fi
	if [ $VERBOSE -ge 2 ]; then
		# Redirect output from wget to stderr, with prefix
		if wget --spider $url 2>&1 | sed "s/^/  OUT: /" >&2; then
			return 0
		fi
	elif wget -q --spider $url >/dev/null 2>&1; then
		return 0
	fi
	return 1
}

get_mirrors() {
	local file
	for file in $@; do
		[ -s $file ] || continue
		grep '^deb[[:space:]]' $file | \
		   grep -v '^deb[[:space:]]\+cdrom:' | \
		   sed 's,^deb \[[^]]*\] ,deb ,' | \
		   grep -v '\(security.debian.org\|volatile.debian.\(net\|org\)\)' | \
		   grep '[[:space:]]main' | \
		   awk '{print $1 " " $2}' | \
		   sed 's,^deb file,deb copy,' | \
		   sed 's,/* *$,,'
	done
}

# Also use mirrors defined in files in $SOURCES_LIST.d/
MIRRORS="$(get_mirrors $SOURCES_LIST $SOURCES_LIST.d/*)"

if ! which 'wget' >/dev/null; then
	echo "ERROR: the command wget is not available; please install it" >&2
	exit 1
fi

# Remove any duplicates at the end of the loop (the perl statement)
IFS="$NL"
for mirror in $MIRRORS; do
	IFS="$OLDIFS"

	tmirror="$(echo $mirror | sed -r "s/^deb //")"
	# We should also check that d-i is available, but that's more complex.
	# Settle for just checking the suite/codename for now.
	if echo "$mirror" | grep -Eq "^deb (f|ht)tp"; then
		if test_url $tmirror/dists/$SUITE/Release; then
			echo "$mirror $SUITE $UDEB_COMPONENTS"
		else
			echo "WARNING: mirror '$tmirror' appears to be invalid; skipping" >&2
		fi
		if [ "$USE_PROPOSED_UPDATES" = 1 ] &&
		   test_url $tmirror/dists/$SUITE-proposed-updates/Release; then
			echo "$mirror $SUITE-proposed-updates $UDEB_COMPONENTS"
			echo "INFO: using '$tmirror' for $SUITE-proposed-updates" >&2
		fi
		for other_suite in $OTHER_SUITES; do
			if test_url $tmirror/dists/$other_suite/Release; then
				echo "$mirror $other_suite $UDEB_COMPONENTS"
				echo "INFO: using '$tmirror' for $other_suite" >&2
			fi
		done
	else
		echo "$mirror $SUITE $UDEB_COMPONENTS"
	fi

done | perl -ne 'print unless $seen{$_}; $seen{$_}=1'