#!/usr/bin/env bash

set -Eeuo pipefail

cd -- "$(dirname -- "${BASH_SOURCE[0]}")"

readonly SERVICE="nginx"

if ! docker compose exec -T "$SERVICE" true >/dev/null 2>&1; then
	echo "Error: nginx container is not running." >&2
	exit 1
fi

docker compose exec -T "$SERVICE" sh <<'EOF'
set -eu

TEMPLATE_DIR="/etc/nginx/templates"
OUTPUT_DIR="/etc/nginx"
ENVSUBST_SCRIPT="/docker-entrypoint.d/20-envsubst-on-templates.sh"
MANAGED_DIRS="conf.d snippets"

if [ ! -d "$TEMPLATE_DIR" ]; then
	echo "Error: template directory does not exist: $TEMPLATE_DIR" >&2
	exit 1
fi

if [ ! -x "$ENVSUBST_SCRIPT" ]; then
	echo "Error: envsubst script is not executable: $ENVSUBST_SCRIPT" >&2
	exit 1
fi

# Only allow templates in directories managed by this script.
find "$TEMPLATE_DIR" -type f -name '*.template' -print | while IFS= read -r template; do
	relative="${template#"$TEMPLATE_DIR"/}"

	case "$relative" in
	conf.d/* | snippets/*)
		;;
	*)
		echo "Error: unmanaged template path: $relative" >&2
		exit 1
		;;
	esac
done

backup_dir="$(mktemp -d /tmp/nginx-reload.XXXXXX)"
committed=0

rollback() {
	status=$?

	if [ "$committed" -eq 0 ]; then
		echo "Reload failed. Restoring previous generated configuration." >&2

		for dir in $MANAGED_DIRS; do
			rm -rf "$OUTPUT_DIR/$dir"

			if [ -d "$backup_dir/$dir" ]; then
				cp -a "$backup_dir/$dir" "$OUTPUT_DIR/$dir"
			fi
		done
	fi

	rm -rf "$backup_dir"
	exit "$status"
}

trap rollback EXIT HUP INT TERM

for dir in $MANAGED_DIRS; do
	if [ -d "$OUTPUT_DIR/$dir" ]; then
		cp -a "$OUTPUT_DIR/$dir" "$backup_dir/$dir"
	fi
done

for dir in $MANAGED_DIRS; do
	if [ -d "$OUTPUT_DIR/$dir" ]; then
		find "$OUTPUT_DIR/$dir" -type f -print | while IFS= read -r output; do
			relative="${output#"$OUTPUT_DIR"/}"

			if [ ! -f "$TEMPLATE_DIR/$relative.template" ]; then
				echo "Removing stale generated file: $relative"
			fi
		done
	fi

	rm -rf "$OUTPUT_DIR/$dir"
	mkdir -p "$OUTPUT_DIR/$dir"
done

"$ENVSUBST_SCRIPT"

nginx -t

committed=1
trap - EXIT HUP INT TERM
rm -rf "$backup_dir"
EOF

docker compose exec -T "$SERVICE" nginx -s reload

echo "Nginx configuration reloaded successfully."