#!/bin/bash
# Restores this host's named volumes from the latest S3 backup, but only into
# volumes that are currently empty - never overwrites data that's already
# there. Run by spinup.sh via `docker compose -f backup-docker-compose.yml
# run --rm restore` before any service that owns one of the mounted volumes
# starts. Safe to run on a bucket/prefix that doesn't exist yet (fresh
# estate): it just leaves the empty volumes alone.
set -euo pipefail

S3_URI="s3://${AWS_S3_BUCKET_NAME}/${AWS_S3_PATH}"
ENDPOINT_ARGS=()
if [ -n "${AWS_ENDPOINT:-}" ]; then
  ENDPOINT_ARGS=(--endpoint-url "https://${AWS_ENDPOINT}")
fi

empty_volumes=()
for dir in /restore/*/; do
  name="$(basename "$dir")"
  if [ -z "$(ls -A "$dir" 2>/dev/null)" ]; then
    empty_volumes+=("$name")
  fi
done

if [ "${#empty_volumes[@]}" -eq 0 ]; then
  echo "All volumes already contain data - skipping restore."
  exit 0
fi

echo "Empty volumes: ${empty_volumes[*]}"

latest="$(aws "${ENDPOINT_ARGS[@]}" s3 ls "${S3_URI}/" 2>/dev/null | awk '{print $4}' | sort | tail -n1 || true)"
if [ -z "$latest" ]; then
  echo "No existing backup found at ${S3_URI} - starting with empty volumes."
  exit 0
fi

echo "Restoring ${S3_URI}/${latest} into empty volumes only..."
tmp="$(mktemp -d)"
trap 'rm -rf "$tmp"' EXIT

aws "${ENDPOINT_ARGS[@]}" s3 cp "${S3_URI}/${latest}" "$tmp/backup.tar.gz"
mkdir "$tmp/extracted"
tar -xzf "$tmp/backup.tar.gz" -C "$tmp/extracted"

for name in "${empty_volumes[@]}"; do
  if [ -d "$tmp/extracted/$name" ]; then
    echo "Restoring $name..."
    cp -a "$tmp/extracted/$name/." "/restore/$name/"
  else
    echo "No $name/ in backup - leaving volume empty."
  fi
done

echo "Restore complete."