#!/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. We'll create a default one next to the script.
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; 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
      . "${HOME}/.resticb2"
    fi
    export B2_ACCOUNT_ID
    export B2_ACCOUNT_KEY
    export B2_BUCKET_NAME
    if [[ -z "${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"
if security find-generic-password -a "$(whoami)" -s "${KEYCHAIN_ENTRY_NAME}" >/dev/null 2>&1 ; then
  export RESTIC_PASSWORD_COMMAND="security find-generic-password -a \"$(whoami)\" -s \"${KEYCHAIN_ENTRY_NAME}\" -w"
# Source file?
elif [[ -f "${HOME}/.resticpass" ]] ; then
  export RESTIC_PASSWORD_FILE="${HOME}/.resticpass"
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 "${REPO}" snapshots &> /dev/null; then
    echo "Restic repository not found or not accessible. Initializing..."
    restic init -r "${REPO}"
fi


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

BACKUP_CMD="restic backup \
    --verbose \
    --repo \"${REPO}\" \
    --exclude-file \"${EXCLUDE_FILE}\" \
    --one-file-system \
    --tag \"macbook-backup\""

if [[ -n "${UPLOAD_LIMIT}" ]]; then
    BACKUP_CMD="${BACKUP_CMD} --limit-upload ${UPLOAD_LIMIT}"
fi

BACKUP_CMD="${BACKUP_CMD} \"${SOURCE_DIR}\""

eval "${BACKUP_CMD}"

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."