build

#
# Perform builds, based on a user-provided script
#

#
# Grab a directory necessary for a build
#

allocate()
{
	local WHEN=$(date +%Y%m%d)

	while read COUNT; do
		TRY="$BUILDS/$WHEN.$COUNT"

		if mkdir "$TRY" 2> /dev/null; then
			echo "$TRY"
			return 0
		fi
	done < <(seq --equal-width 0 99)

	error "Too many builds today"
	return 1
}

#
# This is the message mailed to the user
#

message()
{
	local FINGERPRINT="$1"; shift
	local SCRATCH="$1"; shift
	local LOG="$1"; shift

	local FULL=$(readlink -f "$LOG")

	echo "Build failure, fingerprint $FINGERPRINT"
	echo "-> $SCRATCH"
	echo

	cat "$LOG"
	echo

	echo "-- "
	echo "luthier"
}

#
# Some commands always run on exit, whether success or failure
#

cleanup()
{
	# If any premature exit happens, our default action
	# is to remove trace of our action.

	if [ -n "$SCRATCH" ]; then
		rm -rf "$SCRATCH"
	fi
}

trap cleanup 0

#
# The build directory tracks some state between builds
#

if ! [ -e "$STATE" ]; then
	verbose "Bootstrapping new build directory"

	mkdir "$STATE"   # don't make the tree; the parent must exit
	touch "$STATE/current"
fi

SCRATCH=$(allocate)
METADATA="$SCRATCH/.luthier"
mkdir "$METADATA"

verbose "Fetching sources to $SCRATCH"

if ! callout fetch "$METADATA/fetch"; then
	cat "$METADATA/fetch"  # the scratch dir will be discarded
	exit 1
fi

#
# Don't take up disk space if there's nothing to do
#

NEXT=$(callout fingerprint)
PREV=$(cat "$STATE/current")

if [ "$NEXT" = "$PREV" ]; then
	verbose "No change to sources; no work to do"
	exit 0
fi

echo "$NEXT" > "$STATE/current"
echo "$NEXT" > "$METADATA/fingerprint"

#
# Work out who we would notify for failures. Always do this;
# we don't want to find out on a failure that it's broken.
#

BLAME=$(callout blame)

#
# Go ahead and action the build
#

verbose "Building"

if callout build "$METADATA/build"; then
	verbose "Build was successful"
	STATUS=complete
else
	verbose "Build failed; check $METADATA/build"
	STATUS=fail
	message "$NEXT" "$SCRATCH" "$METADATA/build" |
		mail -s "Build failure: $NEXT" $BLAME
fi

echo "$STATUS" > "$METADATA/status"
echo "$STATUS" > "$STATE/status"

# This process completed, so keep the data
SCRATCH=