#!/bin/bash
# Check spell http://www.shellcheck.net/# online, or download, to test!

############################################################ Function declaration
### OPTIONS
# This function, display usage info
f_display_usage()
{
  echo -e "\n--------------------------------------------------"
	echo "|  This function teach you how this script works"
	echo -e "|  Usage:\n|  $0"  # -e option allow use \n
  echo "|  ${optionHelp} = Print usage"
  echo "|  ${optionSay} = Print echo with message"
  echo "|  ${optionPrintOptions} = Print all options"
  echo "|  ${optionAuthor} = Print author's name"
  echo -e "--------------------------------------------------"
}
f_say()
{
  echo -e "\n--------------------------------------------------"
  echo "  I want to say: ${1}"
  echo -e "--------------------------------------------------"
}
f_author()
{
  echo -e "\n--------------------------------------------------"
  echo "  The author is: vgoni"
  echo -e "--------------------------------------------------"
}
f_options()
{
  echo -e "\n--------------------------------------------------"
  echo "  Printing arguments..."
  echo "  The number of arguments provided is: ${Nargs}"
  for ((i=0; i < ${Nargs}; i++))
  {
     echo "  The argument $((i+1)): ${args[$i]}"
  }
  echo "  No more arguments!"
  echo -e "--------------------------------------------------"
}
### Other functions
# Check if are provided correct arguments
f_evaluate_options()
{
  echo "  Evaluation options, number of arguments: ${Nargs}"
  eval set -- ${options}
  echo "  Options: ${options}"
}
############################################################ End Function declaration

# Main program
clear   # clear terminal

# First of all, store arguments in a variable.
# Bash have variable when call an executable, $0 = CommandName, $1..$N = Arguments
# We store arguments in an array. If a function is called, you cannot access to them if not are global variables
# because they are overwrited by function arguments.
args=(${@}) # Arguments
Nargs=(${#})  # Number of arguments

# We define options, using getopt
# -o Each single character stands for an option
# -l Long name for each option
# : after an option (short or long) tells that option is required argument
# :: tells is a optional argument
# For extension take a look here: http://www.bahmanm.com/blogs/command-line-options-how-to-parse-in-bash-using-getopt
options=$(getopt -o hs:ao -l help,say:,author,options -- "${@}")
if [[ $? -ne 0 ]]
then
  echo "  Error: Detected invalid option"
fi
# -o hs:ao = h & a option, no arguments; s option with a required option;
# -l help,say:,author = same.
# Declarate variables with options to clarify
optionHelp="-h|--help"
optionSay="-s|--say"
optionAuthor="-a|--author"
optionPrintOptions="-o|--options"

# We define some global variables
commandName=$(basename "$0")        # Extract name from first variable
commandPath=$(pwd)                  # Get the path with command pwd

echo "------- My second script begins execution..."
echo "--------------------------------------------"
echo "   Executing command: ${commandName}"
echo "   At path: ${commandPath}"

# Call a function to evaluate arguments as options
f_evaluate_options

# Check all arguments
# We are going to check the all the options shifting them.
# Using shift, the positional parameters are shifted to the left by this number, N.
# Using case syntaxis, more info: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_03.html
while [ "$1" != "" ]
do
  echo "Processing option: ${1}"
  case "$1" in
      -h|--help) f_display_usage ;; # Call function
      -s|--say) f_say $2 ; shift ;; # Call function with argument, and discard argument
      -a|--author) f_author ;;      # Call a function to print author
      -o|--options) f_options ;;     # Call a function to print options
      *)         echo "Unknown option: $1" ; f_display_usage ; break ;;
  esac
  shift;  # Advance
done;

echo "------- My second script end now!"
echo "---------------------------------"