#!/bin/bash
#
# A script to backup a single-user MacBook using restic to either a local
# filesystem or Backblaze B2.

set -o errexit
set -o nounset
set -o pipefail

# --- Configuration ---
# Directory to be backed up.
# For this script, we assume the user's home directory.
SOURCE_DIR="${HOME}"

# Exclude file location.
EXCLUDE_FILE="${HOME}/.restic_exclude.darwin"

# --- Functions ---
usage() {
  cat << EOF
Usage: $(basename "$0") [-l /path/to/repo | -b [bucket]] [-u UPLOAD_LIMIT]

A script to backup a single-user MacBook using restic.

Options:
  -l <path>   Backup to a local filesystem repository at the given path.
  -b [bucket] Backup to a Backblaze B2 bucket. The bucket name is optional.
              If not provided, it will be read from the B2_BUCKET_NAME
              environment variable.
  -u <limit>  Limit the upload speed to the given value in KB/s.
  -h          Show this help message.
EOF
}

# --- Main Script ---
# Check if restic is installed
if ! command -v restic >/dev/null 2>&1; then
  echo "Error: restic command not found." >&2
  echo "Please install restic first: https://restic.net/" >&2
  exit 1
fi

if [[ $# -eq 0 ]]; then
  usage
  exit 1
fi

BACKUP_MODE=""
REPO=""
UPLOAD_LIMIT=""

while getopts ":l:bu:h" opt; do
  case ${opt} in
    l)
      BACKUP_MODE="local"
      REPO="${OPTARG}"
      ;;
    b)
      BACKUP_MODE="b2"
      if [[ ${OPTIND} -le $# && "${!OPTIND:-}" != -* ]]; then
        REPO="b2:${!OPTIND}:"
        OPTIND=$((OPTIND + 1))
      fi
      ;;
    u)
      UPLOAD_LIMIT="${OPTARG}"
      ;;
    h)
      usage
      exit 0
      ;;
    \?)
      echo "Invalid option: -${OPTARG}" >&2
      usage
      exit 1
      ;;
    :)
      echo "Option -${OPTARG} requires an argument." >&2
      usage
      exit 1
      ;;
  esac
done

# --- Pre-run checks ---
if [[ -z "${BACKUP_MODE}" ]]; then
  echo "Error: You must specify a backup mode (-l or -b)." >&2
  usage
  exit 1
fi

if [[ "${BACKUP_MODE}" == "b2" ]]; then
  if [[ -f "${HOME}/.resticb2" ]] ; then
    # shellcheck disable=SC1090
    . "${HOME}/.resticb2"
  fi
  export B2_ACCOUNT_ID="${B2_ACCOUNT_ID:-}"
  export B2_ACCOUNT_KEY="${B2_ACCOUNT_KEY:-}"
  export B2_BUCKET_NAME="${B2_BUCKET_NAME:-}"
  if [[ -z "${B2_ACCOUNT_ID}" || -z "${B2_ACCOUNT_KEY}" ]]; then
    echo "Error: For Backblaze B2 backups, you must set the B2_ACCOUNT_ID and B2_ACCOUNT_KEY environment variables." >&2
    exit 1
  fi

  if [[ -z "${REPO}" ]]; then
    if [[ -n "${B2_BUCKET_NAME}" ]]; then
      REPO="b2:${B2_BUCKET_NAME}:"
    else
      echo "Error: Backup mode is B2 but no bucket name was provided and the B2_BUCKET_NAME environment variable is not set." >&2
      usage
      exit 1
    fi
  fi
fi

KEYCHAIN_ENTRY_NAME="restic_repo_password"
local_user="$(id -un 2>/dev/null || whoami)"
if security find-generic-password -a "${local_user}" -s "${KEYCHAIN_ENTRY_NAME}" >/dev/null 2>&1 ; then
  printf -v RESTIC_PASSWORD_COMMAND 'security find-generic-password -a %q -s %q -w' "${local_user}" "${KEYCHAIN_ENTRY_NAME}"
  export RESTIC_PASSWORD_COMMAND
# Source file?
elif [[ -f "${HOME}/.resticpass" ]] ; then
  export RESTIC_PASSWORD_FILE="${HOME}/.resticpass"
fi

# Ensure exclude file exists so restic does not fail when checking exclusions.
if [[ ! -f "${EXCLUDE_FILE}" ]]; then
  echo "Exclude file '${EXCLUDE_FILE}' not found. Creating a default macOS exclude file..."
  cat << 'EOF' > "${EXCLUDE_FILE}"
# Default restic exclusions for macOS
.Trash
Library/Caches
Library/Logs
.CFUserTextEncoding
EOF
fi

# If the repository does not exist, initialize it.
# The user will be prompted for a password, which will be required for all
# future interactions with the repository.
if ! restic -r "${REPO}" snapshots >/dev/null 2>&1; then
  echo "Restic repository not found or not accessible. Initializing..."
  restic init -r "${REPO}"
fi

# --- Run Backup ---
echo "Starting restic backup..."
echo "Source: ${SOURCE_DIR}"
echo "Repository: ${REPO}"

BACKUP_ARGS=(
  "restic" "backup"
  "--verbose"
  "--repo" "${REPO}"
  "--exclude-file" "${EXCLUDE_FILE}"
  "--one-file-system"
  "--tag" "macbook-backup"
)

if [[ -n "${UPLOAD_LIMIT}" ]]; then
  BACKUP_ARGS+=("--limit-upload" "${UPLOAD_LIMIT}")
fi

BACKUP_ARGS+=("${SOURCE_DIR}")

"${BACKUP_ARGS[@]}"

echo "Backup complete."

# --- Prune old snapshots (optional, but recommended) ---
# Keeps the last 7 daily, 4 weekly, and 6 monthly snapshots.
echo "Pruning old snapshots..."
restic forget \
  --repo "${REPO}" \
  --keep-daily 7 \
  --keep-weekly 4 \
  --keep-monthly 6 \
  --prune

echo "Pruning complete."
echo "Restic backup script finished."