!/bin/bash
clear
main () {
while [ 1 ]
do

    echo "Welcome $LOGNAME, to my Menu Program"
    echo "1. Show the calendar for an specific year"
    echo "2. Show current users logged in"
    echo "3. Display the current directory path"
    echo "4. Change directory"
    echo "5. Long list of files in current directory"
    echo "6. Display current time, date and calendar"
    echo "7. Start VI editor"
    echo "8. Email a file to an user"
    echo "9. Exit this program"

    read -r -p 'Please input an option: ' option

        case $option in
    1) show_calendar;;
    2) show_user;;
    3) current_directory;;
    4) change_directory;;
    5) list_files;;
    6) display_time;;
    7) start_vi;;
    8) get_user;;
    9) echo "Bye $LOGNAME"; exit 0;;
         esac
done
}


show_calendar () {


    read -r -p 'Please enter a month [1-12]: ' month
    read -r -p 'Please enter a year [1-9999]:' year
# also testing if the result is a valid number,
# for more, see:  /msg greybot faq valid
#    if [[ $year != "" && $year != *[![:digit:]]* ]] && ((100 < year && year < 9999))
if ((year >= 0 && year <= 9999)) && ((month >= 0 && month <= 12))
	then
        cal "$month" "$year"
	else
		echo "Entry not valid (Make sure you input [mm-yyyy]"

	fi

	read -r -p "Please [enter] to continue..."
    	clear

}

show_user () {
	finger | more
	read -r -p 'Please [ENTER] to continue...'
	clear
}

current_directory () {
	pwd
	read -r -p 'Please [ENTER] to continue...'
	clear
}

change_directory () {
	read -r -p 'please enter your directory ' dir
	if [ -d "/$dir" ]
	then
		cd "/$dir"; echo "You're in `pwd` and these are your files"
  	        sleep 1.5; ls | more -d
		elif [ -d "/home/$dir" ]
       	then
		cd "/home/$dir"; echo "You're in `pwd` and these are your files"
	       	sleep 1.5; ls | more -d
	elif [ -d "$HOME/$dir" ]
	then
		cd "$HOME/$dir"; echo "You're in `pwd` and these are your files"
		sleep 1.5; ls | more -d
	else
		echo "$dir name does not exist"
	fi
	read -r -p 'Please [ENTER] to continue...'
	clear
}

list_files () {
	ls -l | more;
	read -r -p 'Please [ENTER] to continue...'
	clear
}

display_time () {
	date; cal
	read -r -p 'Please [ENTER] to continue...'
	clear
}

start_vi () {
	read -r -p 'Please input name of your file ' file
	if [ -d $file ]
		then
		echo " $file is a directory "
	elif [ -e $file ] && [ -r $file ]
		then
		vi $file

	elif [ ! -f $file ]
		then
		vi $file
	else
		echo "No a regular file or unreadable"
	fi
	read -r -p 'Please [ENTER] to continue...'
	clear

}

get_user () {
	echo 'Please input a user '
        read user
	grep $user /etc/passwd > /tmp/user
       	sleep .8
if [ -s /tmp/user ]
	then
	sleep 0.3;
else "$user not in the system"
#	read -r -p 'Enter a file name'
#	read file
#	read -r -p 'Enter a subject'
#	read subject
#	else "$user not in the system"
fi
	read -r -p 'Enter a subject: ' subject

	read -r -p 'Enter a file: ' file
if [ $file = *.txt ]
	then
	mail -s "$subject" "$user" < "$file"
	else
	echo "Attach .txt files only"
fi

	rm /tmp/user

	read -r -p 'Please [ENTER] to continue...'
	clear
}

main