#!/usr/bin/env bash
#
# Backup GitLab snippets to combined repo using git subtrees
#
# Required:
#
#  - GitLab personal API token with read_api privilege
#  - Automated git project for storing snippets
#  - curl, git, jq, find, mktemp
#
# tl;dr
#
#  1. Create GitLab API token with 'read_api' access (private snippets)
#  2. Create a new private gitlab project, then clone and configure
#
#    git clone git@gitlab.com:username/snippets.git
#    cd snippets
#    git config user.name "username"
#    git config user.email "username@email.com"
#
#  3. If using multiple GitLab accounts/SSH keys:
#
#    git config core.sshCommand "ssh -i ~/.ssh/username -F /dev/null"
#
#  4. Specify the token and project directory with '-t ... -d ...'
#
#    ./gitsnips.sh -t ABCDEF1234 -d ../snippets/ -p
#
#  5. Review the above changes and `git push` the results when ready
#
# SPDX-License-Identifier: MIT

_VERSION="0.0.3"
_NAME=$(basename "${0}")

# usage
function usage() {
  echo "${_NAME} version ${_VERSION}"
  echo
  echo "Usage: ${_NAME} [OPTIONS...]"
  echo
  echo " Options:"
  echo "  -d <dir>     Git project directory   (default: ./)"
  echo "  -t <string>  GitLab token            (read_api)"
  echo "  -i <file>    Markdown index file     (default: INDEX.md)"
  echo "  -s <file>    Snippets JSON file      (default: snippets.json)"
  echo "  -p           Prune removed snippets  (git rm -r)"
  echo "  -q           Suppress output         (quiet)"
  echo "  -V           Version of program"
  echo "  -h           This help text"
  echo
}

# defaults
declare _GITDIR="./"
declare _TOKEN=""
declare _MDIDX="INDEX.md"
declare _SNJSON="snippets.json"
declare _PRUNE=0
declare _VERBOSE=1

# user input
while getopts "d:t:i:s:pqVh" opt; do
  case "$opt" in
    d)
      _GITDIR="${OPTARG}" ;;
    t)
      _TOKEN="${OPTARG}" ;;
    i)
      _MDIDX="${OPTARG}" ;;
    s)
      _SNJSON="${OPTARG}" ;;
    p)
      _PRUNE=1 ;;
    q)
      _VERBOSE=0 ;;
    V)
      echo "${_NAME} version ${_VERSION}"
      exit 0 ;;
    h)
      usage
      exit 0 ;;
    *)
      echo "Unrecognized option: $OPTARG (Run '$_NAME -h' for help)"
      exit 1 ;;
  esac
done
shift $((OPTIND-1))

# handy for verbose/quiet
function noise {
  local _MSG="$*"
  if [[ ${_VERBOSE} -eq 1 ]]; then
    echo "${_MSG}"
  fi
}

# loop for checking apps
function checkapp() {
  local _XAPPX="$1"
  if [[ -z "$(command -v ${_XAPPX} 2>/dev/null)" ]]; then
    noise "Application ${_XAPPX} not found, exiting."
    exit 99
  fi
}

# loop for checking directories
function checkdir() {
  local _XDIRX="$1"
  if [[ ! -d "${_XDIRX}" ]]; then
    noise "Directory ${_XDIRX} not found, exiting."
    exit 98
  fi
  if [[ ! -w "${_XDIRX}" ]]; then
    noise "Directory ${_XDIRX} not writable, exiting."
    exit 97
  fi
  _GDIRG="${_XDIRX%/}/.git"
  if [[ ! -d "${_GDIRG}" ]]; then
    noise "Directory ${_XDIRX} is not a git project, exiting."
    exit 96
  fi
}

# ensure we can run properly
function preflight() {
  # apps
  checkapp curl
  checkapp jq
  # dirs
  checkdir "${_GITDIR}"
  # token
  if [[ -z "${_TOKEN}" ]]; then
    noise "Token length zero; valid token required, exiting."
    exit 9
  fi
}

# this could exit
preflight

# prep for work
noise "Using ${_GITDIR} as git repository"
pushd "${_GITDIR}" >/dev/null

# fetch latest index
noise "Fetching latest snippet index"
curl --silent --header "PRIVATE-TOKEN: ${_TOKEN}" \
  "https://gitlab.com/api/v4/snippets?per_page=65534" \
  | jq > "${_SNJSON}"

git add "${_SNJSON}"
git commit -q -m "snippet list update" "${_SNJSON}"

# generate list of IDs
noise "Extracting list of snippets with jq"
# create an array string [1234]="title" for each item...
IDLIST=$(jq -r '.[] | "[\(.id)]=\"\(.title)\""' "${_SNJSON}")
# ...adding () around it creates a natural array input string
declare -A IDARRAY=$(echo "(${IDLIST})")

# human friendly index
# - 'git subtree' needs a clean working directory
_TMPIDX=$(mktemp)
echo -e "# Snippet Index\n" > "${_TMPIDX}"

# loop the IDs and either update or add
IDSORTED=$(echo "${!IDARRAY[@]}" | tr ' ' '\n' | sort -n | tr '\n' ' ')
# do not quote IDSORTED below
for id in ${IDSORTED}; do
  if [[ -d "./${id}" ]]; then
    noise "Updating snippet ${id}"
    git subtree pull -q -P "${id}" -m "Updating ${id}" \
      "git@gitlab.com:snippets/${id}.git" HEAD
  else
    noise "Adding snippet ${id}"
    git subtree add -q -P "${id}" -m "Adding ${id}" \
      "git@gitlab.com:snippets/${id}.git" HEAD
  fi
  echo " * [${id}](${id}) ${IDARRAY[$id]}" >> "${_TMPIDX}"
  # be nice to gitlab
  sleep 1
done

# commit the updated Markdown index
noise "Building ${_MDIDX}"
mv -f "${_TMPIDX}" "${_MDIDX}"
git add "${_MDIDX}"
git commit -q -m "markdown index update" "${_MDIDX}"

# prune stale items
if [[ ${_PRUNE} -eq 1 ]]; then
  noise "Pruning stale snippets"
  _RGX='^[0-9]+$'
  # this gives a list of top level dirs without "./" or any hidden subdirs
  _LDIRS=$(find ./ -mindepth 1 -maxdepth 1 -type d -not -path '*/\.*' -printf '%P\n')
  for dir in ${_LDIRS}; do
    if [[ ! ${dir} =~ ${_RGX} ]]; then
      # directory is not a number
      noise "Directory ${dir} is NaN, skipping"
      continue
    fi
    if [[ ! ${IDARRAY[$dir]+_} ]]; then
      # if dir is not an array key, remove it
      noise "Pruning ${dir} not in snippet index"
      git rm -r ${dir}
      git commit -q -m "Removing ${dir}" ${dir}
    fi
  done
fi

# back to where we started
popd >/dev/null
noise "Done - review results and push updates to origin as appropriate"