#!/usr/bin/perl -w
#Kyle Willett 
#ITMO 517 Perl HW 3 add user to system

#check if user is root, if not exit
$isRoot =`whoami`;
chomp $isRoot;

if ($isRoot ne "root")
{
    print "Program requires root privileges, please run as root.\n";
    print "Exiting\n";
    exit 1;
}

#User name checks--------------------------------------------------------------------------------------------
print "Please enter a username for the new user: ";
$newUserName = <STDIN>;
chomp $newUserName;

print "Checking if user name already exists: \n";
`cat /etc/passwd | grep $newUserName > /dev/null`;

if (  $? == 0  )
{
    print "Username exists, impossible to add duplicate \n";
    print "Exiting \n";
    exit 1;
}

print "User name is unique \n";

print "Checking if username meets minimum requirments: \n";

$userNameLength = length($newUserName); 
$minNameSize = 3;

#print "$userNameLength \n";
#print "$minNameSize \n";


if ( $userNameLength < $minNameSize )
{
    print "Username must be at least 3 characters long \n";
    print "Exiting \n";
    exit 1;
}

print "Username meets minimum requirements \n";

print "Enter the full name for the user, it can not be blank.";
$fullName = <STDIN>;
chomp $fullName;

if ( $fullName eq '' )
{
    print "Full name can not be an empty string \n";
    print "Exiting \n";
    exit 1;
}
#End username checks-------------------------------------------------------------------------------------------

#Set Shell for user
print "Enter a default shell for the new user choices are csh, ksh, sh, or bash, press enter for default: \n";
$userShell = <STDIN>;
chomp $userShell;

if ( $userShell eq "csh" )
{
    $shellToSet="/bin/csh";
}
elsif ( $userShell eq "ksh" )
{
    $shellToSet="/bin/ksh";
}
elsif ( $userShell eq "sh" )
{
    $shellToSet="/bin/sh";
}
elsif ( $userShell eq "bash" )
{
    $shellToSet="/bin/bash";
}
elsif ($userShell eq '')
{
    $shellToSet = "/bin/bash";
}
else
{
    print "Invalid shell selected.\n";
    print "Exiting\n";
    exit 1;
}

print "Default shell will be set to: $shellToSet \n";

#End Shell check-----------------------------------------------------------------------------------------------

#Set UID for user
print "Enter UID for new user (greater than 1000) enter for default: \n";
$UIDtoSet = <STDIN>;
chomp $UIDtoSet;

if ( $UIDtoSet ne '')  #case user did select UID, check to see if valid if so set it
{
    #Check to see if UID is a number or not.
    if ( $UIDtoSet =~ /^[0-9]+$/ )
    {
        ;#Couldn't find way to negate the regular expression so this if statment is just blank.
    }
    else
    {
        print "UID must be a number\n" ;
        exit 1;
    }
    
    #Check to see if UID is in use already
    `getent passwd $UIDtoSet > /dev/null`;
    if (  $? == 0  )
    {
        print "UID exists, impossible to add duplicate \n";
        print "Exiting \n";
        exit 1;
    }

    #Check to see if UID is in the reserved range.
    if ( $UIDtoSet < 1000 )
    {
        print "UID too low, must be over 1000 \n";
        print "Exiting \n";
        exit 1;
    }
    
    #Check to see if UID is out of range.
    if ( $UIDtoSet > 4294967295 )
    {
        print "UID too high, must be under 4,294,967,296 \n";
        print "Exiting \n";
        exit 1;
    }
    
    print "$UIDtoSet is a valid UID \n";
}
else  #case user didn't select UID
{
    print "Checking highest UID in system and setting UID to first unused ID \n";
    $UIDcurrent = 1000;
    #Check to see highest userid in system
    while ( 1 )
    {
        `getent passwd $UIDcurrent > /dev/null`;
        #print "Value of ? is: $? \n";
        #print "Value of UIDcurrent is: $UIDcurrent \n \n";
        if (  $? == 512  ) #The value to check for from getent is 512 here and not 2 like in bash version.
        {
            print "$UIDcurrent is valid ID to use \n";
            $UIDtoSet = $UIDcurrent;
            last;  #Apparently you use last to break out of while loop with if statement in perl.
        }
        $UIDcurrent= $UIDcurrent + 1;  #If UID 1000 is taken go to 1001, 1002, ...
    }
    print "$UIDtoSet is a valid UID and will be used \n";
}
#End UID setup-------------------------------------------------------------------------------------------------

#GID setup-----------------------------------------------------------------------------------------------------
#We don't need quite as many checks as UID because GID can be duplicate
print "Enter GID for new user (greater than 1000) enter for default: \n";
$GIDtoSet = <STDIN>;
chomp $GIDtoSet;

if ($GIDtoSet ne '' ) #case user did select GID, check to see if valid if so set it
{
    #Check to see if GID is a number or not.
    if ( $GIDtoSet =~ /^[0-9]+$/ )
    {
        ;
    }
    else
    {
        print "GID must be a number\n" ;
        exit 1;
    }
    
    #Check to see if GID is in the reserved range.
    if ( $GIDtoSet < 1000 )
    {
        print "GID too low, must be over 1000 \n";
        print "Exiting \n";
        exit 1;
    }
    
    #Check to see if GID is out of range.
    if ( $GIDtoSet > 4294967295 )
    {
        print "GID too high, must be under 4,294,967,296 \n";
        print "Exiting \n";
        exit 1;
    }
    
    print "$GIDtoSet is a valid GID \n";
}
else  #Case user didn't select a GID, much simpler than UID case
{
    $GIDtoSet = $UIDtoSet;
    #Just make new GID equal to UID.
    print "$GIDtoSet will be used for GID \n";
}

#We need to real quick determine if the group already exists or not and add if it does not exist.
`getent group $GIDtoSet > /dev/null`;
if (  $? != 0  )
{
    `groupadd $GIDtoSet`;
}

#End GID setup-------------------------------------------------------------------------------------------------
#Create User stage---------------------------------------------------------------------------------------------

print "\nAbout to create new user account with following settings: \n";
print "User name is: $newUserName \n";
print "Full user name is: $fullName\n";
print "UID: $UIDtoSet\n";
print "GID: $GIDtoSet\n";
print "Default login shell: $shellToSet\n";
print "Does this look correct?\n";
print "Enter y to confirm\n";
$confirmUserAdd = <STDIN>;
chomp $confirmUserAdd;

if ( uc($confirmUserAdd) eq "Y" )
{
    `useradd $newUserName -m -c "$fullName" -u $UIDtoSet -g $GIDtoSet -s $shellToSet`;
}
else
{
    print "User add aborted by user\n";
    print "Exiting\n";
    exit 1;
}
#End create user stage-----------------------------------------------------------------------------------------

`echo "$newUserName:password123" | chpasswd`;

print "User account $newUserName has been created with password password123 successfully!\n";
print "Exiting \n";

exit 0;