#!/usr/bin/env bash
set -o errexit #abort if any command fails
me=$(basename "$0")

help_message="\
Usage: $me [-c FILE] [<options>]
Deploy generated files to a git branch.

Options:

  -h, --help               Show this help information.
  -v, --verbose            Increase verbosity. Useful for debugging.
  -e, --allow-empty        Allow deployment of an empty directory.
  -m, --message MESSAGE    Specify the message used when committing on the
                           deploy branch.
  -n, --no-hash            Don't append the source commit's hash to the deploy
                           commit's message.
  -c, --config-file PATH   Override default & environment variables' values
                           with those in set in the file at 'PATH'. Must be the
                           first option specified.

Variables:

  GIT_DEPLOY_DIR      Folder path containing the files to deploy.
  GIT_DEPLOY_BRANCH   Commit deployable files to this branch.
  GIT_DEPLOY_REPO     Push the deploy branch to this repository.

These variables have default values defined in the script. The defaults can be
overridden by environment variables. Any environment variables are overridden
by values set in a '.env' file (if it exists), and in turn by those set in a
file specified by the '--config-file' option."

bundle exec middleman build --clean

parse_args() {
  # Set args from a local environment file.
  if [ -e ".env" ]; then
    source .env
  fi

  # Set args from file specified on the command-line.
  if [[ $1 = "-c" || $1 = "--config-file" ]]; then
    source "$2"
    shift 2
  fi

  # Parse arg flags
  # If something is exposed as an environment variable, set/overwrite it
  # here. Otherwise, set/overwrite the internal variable instead.
  while : ; do
    if [[ $1 = "-h" || $1 = "--help" ]]; then
      echo "$help_message"
      return 0
    elif [[ $1 = "-v" || $1 = "--verbose" ]]; then
      verbose=true
      shift
    elif [[ $1 = "-e" || $1 = "--allow-empty" ]]; then
      allow_empty=true
      shift
    elif [[ ( $1 = "-m" || $1 = "--message" ) && -n $2 ]]; then
      commit_message=$2
      shift 2
    elif [[ $1 = "-n" || $1 = "--no-hash" ]]; then
      GIT_DEPLOY_APPEND_HASH=false
      shift
    else
      break
    fi
  done

  # Set internal option vars from the environment and arg flags. All internal
  # vars should be declared here, with sane defaults if applicable.

  # Source directory & target branch.
  deploy_directory=build
  deploy_branch=gh-pages

  #if no user identity is already set in the current git environment, use this:
  default_username=${GIT_DEPLOY_USERNAME:-deploy.sh}
  default_email=${GIT_DEPLOY_EMAIL:-}

  #repository to deploy to. must be readable and writable.
  repo=origin

  #append commit hash to the end of message by default
  append_hash=${GIT_DEPLOY_APPEND_HASH:-true}
}

main() {
  parse_args "$@"

  enable_expanded_output

  if ! git diff --exit-code --quiet --cached; then
    echo Aborting due to uncommitted changes in the index >&2
    return 1
  fi

  commit_title=`git log -n 1 --format="%s" HEAD`
  commit_hash=` git log -n 1 --format="%H" HEAD`
  
  #default commit message uses last title if a custom one is not supplied
  if [[ -z $commit_message ]]; then
    commit_message="publish: $commit_title"
  fi
  
  #append hash to commit message unless no hash flag was found
  if [ $append_hash = true ]; then
    commit_message="$commit_message"$'\n\n'"generated from commit $commit_hash"
  fi
    
  previous_branch=`git rev-parse --abbrev-ref HEAD`

  if [ ! -d "$deploy_directory" ]; then
    echo "Deploy directory '$deploy_directory' does not exist. Aborting." >&2
    return 1
  fi
  
  # must use short form of flag in ls for compatibility with OS X and BSD
  if [[ -z `ls -A "$deploy_directory" 2> /dev/null` && -z $allow_empty ]]; then
    echo "Deploy directory '$deploy_directory' is empty. Aborting. If you're sure you want to deploy an empty tree, use the --allow-empty / -e flag." >&2
    return 1
  fi

  if git ls-remote --exit-code $repo "refs/heads/$deploy_branch" ; then
    # deploy_branch exists in $repo; make sure we have the latest version
    
    disable_expanded_output
    git fetch --force $repo $deploy_branch:$deploy_branch
    enable_expanded_output
  fi

  # check if deploy_branch exists locally
  if git show-ref --verify --quiet "refs/heads/$deploy_branch"
  then incremental_deploy
  else initial_deploy
  fi

  restore_head
}

initial_deploy() {
  git --work-tree "$deploy_directory" checkout --orphan $deploy_branch
  git --work-tree "$deploy_directory" add --all
  commit+push
}

incremental_deploy() {
  #make deploy_branch the current branch
  git symbolic-ref HEAD refs/heads/$deploy_branch
  #put the previously committed contents of deploy_branch into the index
  git --work-tree "$deploy_directory" reset --mixed --quiet
  git --work-tree "$deploy_directory" add --all

  set +o errexit
  diff=$(git --work-tree "$deploy_directory" diff --exit-code --quiet HEAD --)$?
  set -o errexit
  case $diff in
    0) echo No changes to files in $deploy_directory. Skipping commit.;;
    1) commit+push;;
    *)
      echo git diff exited with code $diff. Aborting. Staying on branch $deploy_branch so you can debug. To switch back to master, use: git symbolic-ref HEAD refs/heads/master && git reset --mixed >&2
      return $diff
      ;;
  esac
}

commit+push() {
  set_user_id
  git --work-tree "$deploy_directory" commit -m "$commit_message"

  disable_expanded_output
  #--quiet is important here to avoid outputting the repo URL, which may contain a secret token
  git push --quiet $repo $deploy_branch
  enable_expanded_output
}

#echo expanded commands as they are executed (for debugging)
enable_expanded_output() {
  if [ $verbose ]; then
    set -o xtrace
    set +o verbose
  fi
}

#this is used to avoid outputting the repo URL, which may contain a secret token
disable_expanded_output() {
  if [ $verbose ]; then
    set +o xtrace
    set -o verbose
  fi
}

set_user_id() {
  if [[ -z `git config user.name` ]]; then
    git config user.name "$default_username"
  fi
  if [[ -z `git config user.email` ]]; then
    git config user.email "$default_email"
  fi
}

restore_head() {
  if [[ $previous_branch = "HEAD" ]]; then
    #we weren't on any branch before, so just set HEAD back to the commit it was on
    git update-ref --no-deref HEAD $commit_hash $deploy_branch
  else
    git symbolic-ref HEAD refs/heads/$previous_branch
  fi
  
  git reset --mixed
}

filter() {
  sed -e "s|$repo|\$repo|g"
}

sanitize() {
  "$@" 2> >(filter 1>&2) | filter
}

[[ $1 = --source-only ]] || main "$@"