Menu

#!/bin/bash
# Kevin Fan (26/4/17)
# Description: This Menu script present the user with a command line
# menu and allow the user to select the functionaly based on
# their selection which in turns executes the relevent script

# Clear the console
clear

# Function that displays available options to user, reads in user option and calls validation
# function to check is user input valid
function mainMenu 
{
	printf "\nWelcome. Please choose one of the following:\n"
	printf "\n\t1. Add a new Customer\n"
	printf "\n\t2. Remove an existing Customer\n"
	printf "\n\t3. Search for a Customer\n"
	printf "\n\t4. E-mail a customer\n"
	printf "\n\t==================================\n"
	printf "\n\t0. Exit\n"

	printf  "\nEnter a number: "
	read userChoice
	validInput
}

# This function performs validation on userChoice from mainMenu function.
# If validation fails, a relevent error is displayed and returns to mainMenu to re-enter user Choice
# If validation passes, runMenu function is called, which in turn executes the relevant script call
function validInput 
{
	# If the userChoice is not an integar but a string, error message is displayed for 1 second and returns to main menu
	if ! [[ $userChoice =~ ^-?[0-9]+$ ]]; then
		printf "\nInvalid (String) entry, only integers shown are allowed. Please re-renter option\n"
		printf "\nReturning to Main menu ...."
		sleep 1
		clear
		mainMenu
	# Checks if userChoice inputs an integar outside the available options, error message is displayed for 1 second and returns to main menu
	elif [ $userChoice -le -1 ] || [ $userChoice -ge 5 ]; then
		printf "\nInvalid number entered\n"
		printf "\nReturning to Main menu ...."
		sleep 1
		clear
		mainMenu

	else
		runMenu
	fi
}


# From user choice, execute relevant script for function. Function is a while loop until 0 in 
# the main menu

function runMenu
{
	# While loop to stay in script until user enters 0 from the main menu function to exit script
	while [ $userChoice -ne 0 ]
	do
		# Case statement that executes relevant scripts depending on userChoice from main menu
		case $userChoice in
	        	1) ./AddCust ;;
	        	2) ./RemCust ;;
	        	3) ./FindCust ;;
	        	4) ./EmailCust ;;
		esac
		# After returning from the relevant script, display message for 1 second, clear the console and return to main menu
		printf "\n\tReturning to main menu..."
		sleep 1
		clear
		mainMenu
	done
	printf "\nExiting... bye\n"
	exit 1
}

#Run main Menu function, which begins the loop 
mainMenu