#!/usr/bin/env bash
set -Eeuo pipefail

usage() {
  cat <<'EOF'
Usage:
  restore-from-s3.sh latest
  restore-from-s3.sh <s3-object-key>

Examples:
  restore-from-s3.sh latest
  restore-from-s3.sh qlockify/qlockify-backup-YYYYMMDD-HHMMSS.tar.gz.enc

Environment:
  DEPLOY_ROOT                       Deployment directory. Defaults to ~/qlockify-deployment.
  S3_BACKUP_BUCKET                  S3 bucket name.
  S3_BACKUP_PREFIX                  S3 object prefix. Defaults to qlockify.
  S3_BACKUP_REGION                  S3 region. Defaults to us-east-1.
  S3_BACKUP_ENDPOINT_URL            Optional S3-compatible endpoint URL.
  S3_BACKUP_ACCESS_KEY_ID           S3 access key.
  S3_BACKUP_SECRET_ACCESS_KEY       S3 secret key.
  BACKUP_ENCRYPTION_PASSPHRASE      Passphrase used to decrypt backup archives.

Existing RESTORE_SKIP_DB, RESTORE_SKIP_MEDIA, and RESTORE_SKIP_ENV flags are
passed through to restore.sh.
EOF
}

log() {
  printf '[restore-s3] %s\n' "$*"
}

fail() {
  printf '[restore-s3] %s\n' "$*" >&2
  exit 1
}

require_var() {
  local name="$1"
  [[ -n "${!name:-}" ]] || fail "$name is required"
}

load_env() {
  local env_path="$1"
  [[ -f "$env_path" ]] || fail "Deployment env file not found: $env_path"
  set -a
  # shellcheck disable=SC1090
  . "$env_path"
  set +a
}

aws_s3() {
  if [[ -n "${S3_BACKUP_ENDPOINT_URL:-}" ]]; then
    aws --endpoint-url "$S3_BACKUP_ENDPOINT_URL" s3 "$@"
  else
    aws s3 "$@"
  fi
}

normalize_prefix() {
  local value="${1:-qlockify}"
  value="${value#/}"
  value="${value%/}"
  printf '%s' "$value"
}

latest_object_key() {
  aws_s3 ls "s3://$S3_BACKUP_BUCKET/$S3_BACKUP_PREFIX/" --recursive \
    | awk '{print $4}' \
    | grep '\.tar\.gz\.enc$' \
    | sort \
    | tail -n 1
}

if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
  usage
  exit 0
fi

REQUESTED_KEY="${1:-}"
[[ -n "$REQUESTED_KEY" ]] || {
  usage
  exit 1
}

command -v aws >/dev/null 2>&1 || fail "aws CLI is required"
command -v openssl >/dev/null 2>&1 || fail "openssl is required"

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
DEPLOY_ROOT="${DEPLOY_ROOT:-$(cd "$SCRIPT_DIR/.." && pwd)}"
DEPLOY_ENV="$DEPLOY_ROOT/.env"
RESTORE_SCRIPT="$SCRIPT_DIR/restore.sh"

[[ -x "$RESTORE_SCRIPT" ]] || fail "Restore script is not executable: $RESTORE_SCRIPT"
load_env "$DEPLOY_ENV"

S3_BACKUP_PREFIX="$(normalize_prefix "${S3_BACKUP_PREFIX:-qlockify}")"
S3_BACKUP_REGION="${S3_BACKUP_REGION:-us-east-1}"

require_var S3_BACKUP_BUCKET
require_var S3_BACKUP_ACCESS_KEY_ID
require_var S3_BACKUP_SECRET_ACCESS_KEY
require_var BACKUP_ENCRYPTION_PASSPHRASE

export AWS_ACCESS_KEY_ID="$S3_BACKUP_ACCESS_KEY_ID"
export AWS_SECRET_ACCESS_KEY="$S3_BACKUP_SECRET_ACCESS_KEY"
export AWS_DEFAULT_REGION="$S3_BACKUP_REGION"
export AWS_EC2_METADATA_DISABLED=true

if [[ "$REQUESTED_KEY" == "latest" ]]; then
  log "Resolving latest encrypted backup object"
  OBJECT_KEY="$(latest_object_key)"
  [[ -n "$OBJECT_KEY" ]] || fail "No encrypted backups found in s3://$S3_BACKUP_BUCKET/$S3_BACKUP_PREFIX/"
else
  OBJECT_KEY="${REQUESTED_KEY#s3://$S3_BACKUP_BUCKET/}"
fi

WORK_DIR="$(mktemp -d)"
trap 'rm -rf "$WORK_DIR"' EXIT

ENCRYPTED_PATH="$WORK_DIR/$(basename "$OBJECT_KEY")"
DECRYPTED_PATH="$WORK_DIR/${ENCRYPTED_PATH##*/}"
DECRYPTED_PATH="${DECRYPTED_PATH%.enc}"

log "Downloading encrypted backup from s3://$S3_BACKUP_BUCKET/$OBJECT_KEY"
aws_s3 cp "s3://$S3_BACKUP_BUCKET/$OBJECT_KEY" "$ENCRYPTED_PATH" --only-show-errors

log "Decrypting backup archive"
openssl enc -d -aes-256-cbc -pbkdf2 -iter 200000 \
  -in "$ENCRYPTED_PATH" \
  -out "$DECRYPTED_PATH" \
  -pass env:BACKUP_ENCRYPTION_PASSPHRASE

log "Restoring decrypted backup archive"
DEPLOY_ROOT="$DEPLOY_ROOT" "$RESTORE_SCRIPT" "$DECRYPTED_PATH"

log "S3 restore completed from: s3://$S3_BACKUP_BUCKET/$OBJECT_KEY"