demo-magic.sh

#!/usr/bin/env bash

###############################################################################
#
# demo-magic.sh
#
# Copyright (c) 2015-2022 Paxton Hare
#
# This script lets you script demos in bash. It runs through your demo script
# when you press ENTER. It simulates typing and runs commands.
#
###############################################################################

# the speed to simulate typing the text
TYPE_SPEED=20

# no wait after "p" or "pe"
NO_WAIT=false

# if > 0, will pause for this amount of seconds before automatically proceeding with any p or pe
PROMPT_TIMEOUT=0

# don't show command number unless user specifies it
SHOW_CMD_NUMS=false


# handy color vars for pretty prompts
BLACK="\033[0;30m"
BLUE="\033[0;34m"
GREEN="\033[0;32m"
GREY="\033[0;90m"
CYAN="\033[0;36m"
RED="\033[0;31m"
PURPLE="\033[0;35m"
BROWN="\033[0;33m"
WHITE="\033[0;37m"
BOLD="\033[1m"
COLOR_RESET="\033[0m"

C_NUM=0

# prompt and command color which can be overriden
DEMO_PROMPT="$ "
DEMO_CMD_COLOR=$BOLD
DEMO_COMMENT_COLOR=$GREY

##
# prints the script usage
##
function usage() {
  echo -e ""
  echo -e "Usage: $0 [options]"
  echo -e ""
  echo -e "  Where options is one or more of:"
  echo -e "  -h  Prints Help text"
  echo -e "  -d  Debug mode. Disables simulated typing"
  echo -e "  -n  No wait"
  echo -e "  -w  Waits max the given amount of seconds before "
  echo -e "      proceeding with demo (e.g. '-w5')"
  echo -e ""
}

##
# wait for user to press ENTER
# if $PROMPT_TIMEOUT > 0 this will be used as the max time for proceeding automatically
##
function wait() {
  if [[ "$PROMPT_TIMEOUT" == "0" ]]; then
    read -rs
  else
    read -rst "$PROMPT_TIMEOUT"
  fi
}

##
# print command only. Useful for when you want to pretend to run a command
#
# takes 1 param - the string command to print
#
# usage: p "ls -l"
#
##
function p() {
  if [[ ${1:0:1} == "#" ]]; then
    cmd=$DEMO_COMMENT_COLOR$1$COLOR_RESET
  else
    cmd=$DEMO_CMD_COLOR$1$COLOR_RESET
  fi

  # render the prompt
  x=$(PS1="$DEMO_PROMPT" "$BASH" --norc -i </dev/null 2>&1 | sed -n '${s/^\(.*\)exit$/\1/p;}')

  # show command number is selected
  if $SHOW_CMD_NUMS; then
   printf "[$((++C_NUM))] $x"
  else
   printf "$x"
  fi

  # wait for the user to press a key before typing the command
  if [ $NO_WAIT = false ]; then
    wait
  fi

  if [[ -z $TYPE_SPEED ]]; then
    echo -en "$cmd"
  else
    echo -en "$cmd" | pv -qL $[$TYPE_SPEED+(-2 + RANDOM%5)];
  fi

  # wait for the user to press a key before moving on
  if [ $NO_WAIT = false ]; then
    wait
  fi
  echo ""
}

##
# Prints and executes a command
#
# takes 1 parameter - the string command to run
#
# usage: pe "ls -l"
#
##
function pe() {
  # print the command
  p "$@"
  run_cmd "$@"
}

##
# print and executes a command immediately
#
# takes 1 parameter - the string command to run
#
# usage: pei "ls -l"
#
##
function pei {
  NO_WAIT=true pe "$@"
}

##
# Enters script into interactive mode
#
# and allows newly typed commands to be executed within the script
#
# usage : cmd
#
##
function cmd() {
  # render the prompt
  x=$(PS1="$DEMO_PROMPT" "$BASH" --norc -i </dev/null 2>&1 | sed -n '${s/^\(.*\)exit$/\1/p;}')
  printf "$x\033[0m"
  read command
  run_cmd "${command}"
}

function run_cmd() {
  function handle_cancel() {
    printf ""
  }

  trap handle_cancel SIGINT
  stty -echoctl
  eval $@
  stty echoctl
  trap - SIGINT
}


function check_pv() {
  command -v pv >/dev/null 2>&1 || {

    echo ""
    echo -e "${RED}##############################################################"
    echo "# HOLD IT!! I require pv for simulated typing but it's " >&2
    echo "# not installed. Aborting." >&2;
    echo -e "${RED}##############################################################"
    echo ""
    echo -e "${COLOR_RESET}Disable simulated typing: "
    echo ""
    echo -e "   unset TYPE_SPEED"
    echo ""
    echo "Installing pv:"
    echo ""
    echo  "   Mac: $ brew install pv"
    echo ""
    echo  "   Other: https://www.ivarch.com/programs/pv.shtml"
    echo  ""
    exit 1;
  }
}

#
# handle some default params
# -h for help
# -d for disabling simulated typing
#
while getopts ":dhncw:" opt; do
  case $opt in
    h)
      usage
      exit 1
      ;;
    d)
      unset TYPE_SPEED
      ;;
    n)
      NO_WAIT=true
      ;;
    c)
      SHOW_CMD_NUMS=true
      ;;
    w)
      PROMPT_TIMEOUT=$OPTARG
      ;;
  esac
done

##
# Do not check for pv. This trusts the user to not set TYPE_SPEED later in the
# demo in which case an error will occur if pv is not installed.
##
if [[ -n "$TYPE_SPEED" ]]; then
  check_pv
fi