_easycli

# Easy CLI v0.1.0
# https://github.com/ppo/easycli


# Define settings.
EASYCLI_TARGET="${EASYCLI_TARGET-$0}"
EASYCLI_COMPACT=${EASYCLI_COMPACT-0}
EASYCLI_USAGE_ARGS="${EASYCLI_USAGE_ARGS-COMMAND [ARGS]...}"
EASYCLI_COLOR_ARG="${EASYCLI_COLOR_ARG-\e[32m}"
EASYCLI_COLOR_CMD="${EASYCLI_COLOR_CMD-\e[36m}"
EASYCLI_COLOR_ERROR="${EASYCLI_COLOR_ERROR-\e[31m}"
EASYCLI_COLOR_HEADING="${EASYCLI_COLOR_HEADING-\e[1;37m}"
EASYCLI_COLOR_RESET="${EASYCLI_COLOR_RESET-\e[0m}"


# If no color support, disable colors.
num_colors=$(tput colors)
if [ -z "$num_colors" ] || [ $num_colors -lt 8 ]; then
  EASYCLI_COLOR_ARG=
  EASYCLI_COLOR_CMD=
  EASYCLI_COLOR_ERROR=
  EASYCLI_COLOR_HEADING=
  EASYCLI_COLOR_RESET=
fi


# Check that the required `EASYCLI_TARGET` variable is defined.
if [ -z "$EASYCLI_TARGET" ]; then
  echo -e "${EASYCLI_COLOR_ERROR}ERROR: Set 'EASYCLI_TARGET' in your script as follows:" \
    "EASYCLI_TARGET="\$\{BASH_SOURCE[0]\}"${EASYCLI_COLOR_RESET}"
  exit 1;
fi

# Check that the `EASYCLI_TARGET` exists.
if ! [ -f "$EASYCLI_TARGET" ]; then
  echo -e "${EASYCLI_COLOR_ERROR}ERROR: The script defined in 'EASYCLI_TARGET' cannot be found."
  echo -e "$EASYCLI_TARGET does not exist.${EASYCLI_COLOR_RESET}"
  exit 1
fi


# Initialize global variables.
EASYCLI_COMMANDS=
EASYCLI_COMMANDS_TABLE=


# Initialize `EASYCLI_COMMANDS_TABLE`, the table of command names with their description.
function easycli_init_commands_table() {
  [ -n "$EASYCLI_COMMANDS_TABLE" ] && return
  EASYCLI_COMMANDS_TABLE=$(
    sed -E -n \
      -e "/^## / { \
          h; \
          s/.*//; \
          :loop" \
      -e "H; \
          n; \
          s/^##( |$)//; \
          t loop" \
      -e "s/^function ([^\(]+).*$/\1/; \
          s/^command_//; \
          s/__/:/; \
          G; \
          s/\\n## /\\\t/; \
          s/\\n/ /g; \
          p; }" \
      "$EASYCLI_TARGET" \
    | LC_ALL=C sort -f
  )
}


# Initialize `EASYCLI_COMMANDS`, the list of all available command names.
# It's the first column of `EASYCLI_COMMANDS_TABLE`.
function easycli_init_commands() {
  [ -n "$EASYCLI_COMMANDS" ] && return
  easycli_init_commands_table
  EASYCLI_COMMANDS=$(echo -e "$EASYCLI_COMMANDS_TABLE" | cut -f 1)
}


# Display the list of commands with their description.
function easycli_display_commands() {
  easycli_init_commands

  declare -i cmd_max_length=0
  for cmd in $(echo -e "$EASYCLI_COMMANDS"); do
    l=${#cmd}
    [ $l -gt $cmd_max_length ] && cmd_max_length=$l
  done

  echo -e "$EASYCLI_COMMANDS_TABLE" | awk \
    -F "\t" \
    -v num_cols=$(tput cols) \
    -v cmd_max_length=$cmd_max_length \
    -v left_pad="  " \
    -v col_pad=" " \
    -v compact="$EASYCLI_COMPACT" \
    -v color_heading="$(printf "$EASYCLI_COLOR_HEADING")" \
    -v color_cmd="$(printf "$EASYCLI_COLOR_CMD")" \
    -v color_arg="$(printf "$EASYCLI_COLOR_ARG")" \
    -v color_reset="$(printf "$EASYCLI_COLOR_RESET")" \
    'function print_col1(content) {
      if (content == "") printf "\n";
      printf left_pad;
      if (indent == "") {
        printf color_cmd sprintf("%-*s", cmd_max_length, content) color_reset col_pad;
        line_length = col1_length;
      } else {
        printf indent;
        line_length = length(left_pad) + length(indent);
      }
    }
    function update_line_length() {
      line_length += 1 + length(words[i]);
    }
    function process_args(tag, word) {
      switch (tag) {
        case "@usage":
        case "@args":
          prefix = toupper(substr(tag, 2, 1)) substr(tag, 3) ": ";
          output = color_heading prefix color_reset color_arg word;
          indent2 = sprintf("%-*s", length(prefix), "");
          break;
        case "@arg":
          prefix = "";
          output = color_arg word color_reset;
          indent2 = sprintf("%-*s", length(word) + 1, "");
          break;
        default: return;
      }

      if (indent == "" && !compact) printf "\n";
      indent = "  ";
      print_col1("");
      printf " " output;
      line_length += 1 + length(prefix) + length(word);
      indent = indent indent2;
    }
    {
      if (!compact && col1_length) printf "\n";
      col1_length = length(left_pad) + cmd_max_length + length(col_pad);
      indent = ""; indent2 = "";
      num_words = split($2, words, " ");
      tag = "";
      print_col1($1);
      for (i = 1; i <= num_words; i++) {
        if (substr(words[i], 0, 1) == "@") {
          tag = words[i];
          continue;
        }
        if (tag) {
          process_args(tag, words[i]);
          tag = "";
          continue;
        }
        update_line_length();
        if (line_length > num_cols) {
          print_col1("");
          update_line_length();
        }
        printf " " words[i];
      }
      printf color_reset "\n";
    }'
}


# Display the full help screen (usage header and list of commands with their description).
function easycli_display_usage() {
  [ "$EASYCLI_COMPACT" = 0 ] && echo
  echo -e "${EASYCLI_COLOR_HEADING}USAGE:${EASYCLI_COLOR_RESET}" \
    "${EASYCLI_COLOR_CMD}$(basename $EASYCLI_TARGET) ${EASYCLI_USAGE_ARGS}${EASYCLI_COLOR_RESET}"
  echo
  echo -e "${EASYCLI_COLOR_HEADING}COMMANDS:${EASYCLI_COLOR_RESET}"
  [ "$EASYCLI_COMPACT" = 0 ] && echo
  easycli_display_commands
  [ "$EASYCLI_COMPACT" = 0 ] && echo
}


# Return the function name based on the command name.
# Converts all `:` into `__`.
# Try to locate the function with and without the `command_` prefix.
function easycli_get_command_function() {
  fct=${1//:/__}

  # Check first if the function with `command_` prefix exists. If so, return it.
  [ -n "$(LC_ALL=C type "command_$fct" 2> /dev/null)" ] && echo "command_$fct"

  # If the regular function is not found, exit with error message.
  if [ -z "$(LC_ALL=C type $fct 2> /dev/null)" ]; then
    echo -e "${EASYCLI_COLOR_ERROR}ERROR: Function for command '$1' not found.${EASYCLI_COLOR_RESET}"
    exit 1
  fi

  echo $fct
}


# Execute the script with the provided script arguments.
function easycli_exec_command() {
  easycli_init_commands  # Retrieve available commands.
  COMMAND=$1  # Get the command to execute.
  shift  # Remove the command from args.

  # If no command defined or command is "help", show usage.
  if [ -z "$COMMAND" ] || [ "$COMMAND" = "help" ]; then
    [[ "$*" =~ "--compact" ]] && EASYCLI_COMPACT=1
    easycli_display_usage

  # If the command is registered via easycli, execute it with scripts args as-is.
  elif [ -n "$(grep "^$COMMAND$" <<< "$EASYCLI_COMMANDS")" ]; then
    $(easycli_get_command_function "$COMMAND") "$@"

  # If the command is not registered via easycli, report error and show usage.
  else
    echo -e "${EASYCLI_COLOR_ERROR}ERROR: Unknown command '$COMMAND'.${EASYCLI_COLOR_RESET}"
    easycli_display_usage
  fi
}