Bash_Scripts/Misc/Templater.bash

#!/usr/bin/env bash

# "Import" our needed functions from our library
LIBRARY_PATH="/usr/local/lib/Custom-Scripts"
# shellcheck source=/usr/local/lib/
source "${LIBRARY_PATH}/Logging-RGB.bash" || echo "Unable to source Logging-RGB.bash at ${LIBRARY_PATH}"
# shellcheck source=/usr/local/lib/
source "${LIBRARY_PATH}/Trim.bash" || log "error" "Unable to source Trim.bash at ${LIBRARY_PATH}"

# Tmp file used because most distros have this dir exist in RAM, use PID of our process to write to
TEMP_FILE="/tmp/$$"

# Set the Contents directory to the env variable, script set, or to their .contents file in the user home
CONTENTS_DIRECTORY="${CONTENTS_DIRECTORY:=\
      $(mkdir -p "${HOME}/.contents" && echo "${HOME}/.contents")}"

EXIT_ON_ERROR=0

REPEAT=1
WRITE_TEMPLATE_MANUALLY_SET=1
WRITE_TEMPLATE_TO=""

declare -A template_handlers

template_handlers=(
  ["FILE"]="file_handler"
  ["WRITE-TO"]="write_to_handler"
  ["TEMPLATE"]="template_handler"
)

write_content() {
  local content
  local leading_spaces
  content="${1}"
  leading_spaces="${2}"

  local string_builder
  string_builder=""

  for ((i=1; i<=leading_spaces; i++)); do
    string_builder="${string_builder} "
  done
  string_builder="${string_builder}${content}"
  _write_to_buffer "${string_builder}"
}

_write_to_buffer() {
  log "debug" "Received content to write to buffer:
${1}"
  printf "%s\n" "${1}" >> "${TEMP_FILE}"
  log "debug" "Finished writing content to buffer"
}

template_handler() {
  local template_file
  template_file="${1}"

  local leading_spaces
  leading_spaces="${2}"
  # Check that the given file is not an absolute path
  if [[ ! "${template_file:0:1}" == "/" ]]; then
    template_file="${CONTENTS_DIRECTORY}/${template_file}"
  fi
  if [[ ! -f "${template_file}" ]]; then
    log "error" "The given template file \"${template_file}\" does not exist"
    return 1
  fi

  file_handler "${template_file}" "${leading_spaces}"
  REPEAT=0
}

file_handler() {
  local file
  file="${1}"

  local leading_spaces
  leading_spaces="${2}"

  # Check that the given file is not an absolute path
  if [[ ! "${file:0:1}" == "/" ]] && [[ ! -f "${file}" ]]; then
    file="${CONTENTS_DIRECTORY}/${file}"
  fi


  if [[ ! -f "${file}" ]]; then
    log "error" "The given file \"${file}\" does not exist"
    return 1
  fi

  while IFS="\n" read -r line; do
    write_content "${line}" "${leading_spaces}"
  done < "${file}"
}


write_to_handler() {
  local write_path
  write_path=${1}

  log "debug" "Received write path \"${write_path}\""
  if [[ ! "${write_path:0:1}" == "/" ]]; then
    log "error" "Given write path was invalid, received \"${write_path}\", the path must be an absolute path"
    return 1
  fi

  if [[ -d "${write_path}" ]]; then
    log "error" "Given write path was invalid, received \"${write_path}\", the path must be a path to an output file (doesn't have to exist), not a directory"
    return 1
  fi
  # This means that it was NOT manually set, 0 is true in shell
  if (("${WRITE_TEMPLATE_MANUALLY_SET}" == 1)); then
    WRITE_TEMPLATE_TO=${write_path}
  fi
}

parse_template_extracted() {
  local tmpl_extracted
  tmpl_extracted="${1}"

  local full_line
  full_line="${2}"

  local num_leading_spaces
  num_leading_spaces=$(awk -F"[ ]" '{for(i=1;i<=NF && ($i=="");i++);print ""i-1""}' <<< "${full_line}")

  # Basic checks to ensure template is correct, first not empty, second that an '=' was passed to give type specifier
  # third is to ensure only one equals sign is passed
  if [[ -z "${tmpl_extracted}" ]]; then
    log "error" "Template passed was empty... ignoring"
    return 1
  elif [[ ! "${tmpl_extracted}" = *"="* ]]; then
    log "error" "Template line passed was of an invalid format, missing = specifier, assumed type is missing as well"
    return 1
  elif [ "$(echo "${tmpl_extracted}" | grep -o "=" | wc -l)" -gt 1 ]; then
    log "error" "Template line passed had too many \"=\", there should only be 1"
    return 1
  fi

  local var_type
  var_type="$(trim "$(echo "${tmpl_extracted}" | cut -d "=" -f1)")"

  # Shellcheck incorrectly reads the below line
  # shellcheck disable=SC2116
  var_type="$(echo "${var_type^^}")"

  local var_arg
  var_arg="$(trim "$(echo "${tmpl_extracted}" | cut -d "=" -f2)")"

  local handler_to_use
  handler_to_use="${template_handlers[${var_type}]}"

  if [[ -z "${handler_to_use}" ]]; then
    log "error" "Invalid handler found, no such handler \"${var_type}\" exists as a handler"
    return 1
  else
    log "debug" "Using handler \"${handler_to_use}\""
    if ! eval "${handler_to_use}" "${var_arg}" "${num_leading_spaces}"; then
      log "error" "Arguments passed for \"${var_type}\" were invalid, check the argument"
      return 1
    fi
    log "debug" "Finished using handler \"${handler_to_use}\""
  fi
}

output_finished_template() {
  log "debug" "Outputting finished template"
  mkdir -p "$(dirname "${WRITE_TEMPLATE_TO}")"
  # We want globbing here
  # shellcheck disable=SC2086
  if [[ -z "${WRITE_TEMPLATE_TO}" ]]; then
    log "error" "Was never given a path to write the template to, check your template file or explicitly specify an output location"
    exit 1
  else
    mv "${TEMP_FILE}" ${WRITE_TEMPLATE_TO}
  fi
}

parse_template_line() {
  local line
  line="${1}"

  if [[ "${line}" = *\{#%*%#\}* ]]; then
    tmpl_extracted="${line#*{#%}"
    tmpl_extracted="${tmpl_extracted%\%#\}*}"
    tmpl_extracted="$(trim "${tmpl_extracted}")"

    log "debug" "Extracted a template: ${tmpl_extracted}"
    # Check for non zero status codes and parse the extracted template
    if ! parse_template_extracted "${tmpl_extracted}" "${line}"; then
      return 1
    fi
    log "debug" "Finished extracting template: ${tmpl_extracted}"
  else
    write_content "${line}" "0"
  fi
}

read_template() {
  local read_file
  local line
  local line_num
  line_num=1
  read_file="${1}"
  log "info" "Parsing template file \"${read_file}\""
  while IFS="\n" read -r line; do
    # Check for non zero status code
    if ! parse_template_line "${line}"; then
      log "error" "Invalid template passed from \"${read_file}\", check line ${line_num}"
      if (( "${EXIT_ON_ERROR}" == 0 )); then
        exit 1
      fi
    fi
    line_num=$((line_num + 1))
  done <"${read_file}"
}

templater() {
  local read_file
  read_file="${1}"
  [[ ! -f "${read_file}" ]] &&
    log "error" "$(important "${read_file}") does not exist!" &&
    return 1

  read_template "${read_file}"

  if (( "${REPEAT}" == 0 )); then
    REPEAT=1
    log "debug" "Repeat set to 0, repeating on the finished file located at ${TEMP_FILE}"
    mv "${TEMP_FILE}" "${TEMP_FILE}-repeat"
    main "-t" "${TEMP_FILE}-repeat"
  else
    log "info" "Finished parsing template file \"${read_file}\""
    log "info" "Writing finished template..."
    output_finished_template
    log "info" "Finished writing template for \"${read_file}\" to \"${WRITE_TEMPLATE_TO}\""
  fi
}

usage() {
  # Print out usage instructions for the local script
  #
  # Arguments:
  #   None
  #
  # Usage:
  #   usage
  #
  # POSIX Compliant:
  #   Yes
  #
  printf "Usage: %s\n" \
    "$(basename ${0}) -i \"this is some input\" -t \"this is some more example input\"
  --input <string> | -i <string>
    Example:
      --input \"this is an example input\"
  --test <string> | -t <string>
    Example:
      --test \"this is more example input\""
}

main() {
  # Parse input arguments
  #
  # Arguments:
  #   Consult the `usage` function
  #
  # Usage:
  #   parse_args "$@"
  #     - All arguments should be ingested by parse_args first for variable setting
  #
  # POSIX Compliant:
  #   Yes
  #
  local template_file

  while :; do
    case ${1} in
    -h | -\? | --help)
      usage # Display a usage synopsis.
      exit
      ;;
    --) # End of all options.
      break
      ;;
    -t | --template-file)
      shift
      template_file="${1}"
      [[ ! -f "${template_file}" ]] &&
        log "error" "The given template file \"${template_file}\" does not exist" &&
        exit 1
      log "info" "Set template file to \"${template_file}\""
      ;;
    -c | --contents-dir)
      shift
      CONTENTS_DIRECTORY="${1}"
      [[ ! -d "${CONTENTS_DIRECTORY}" ]] &&
        log "error" "\"${CONTENTS_DIRECTORY}\" is an invalid path, contents directory must be an absolute path" &&
        exit 1
      log "info" "Set contents directory to \"${CONTENTS_DIRECTORY}\""
      ;;
    -o | --output-to)
      shift
      WRITE_TEMPLATE_MANUALLY_SET=0
      WRITE_TEMPLATE_TO="${1}"
      ;;
    -n | --no-exit)
      EXIT_ON_ERROR=1
      log "info" "No longer exiting on errors."
      ;;
    -?*)
      printf 'Unknown option: %s\n' "$1" >&2
      usage
      exit 1
      ;;
    *) # Default case: No more options, so break out of the loop.
      break ;;
    esac
    shift
  done
  [[ -z "${template_file}" ]] &&
    log "error" "No template file provided, exiting" &&
    exit 1
  templater "${template_file}"
}

main "$@"