#!/usr/bin/perl
#
# Name : Matthew Reeves
#
# Displays summary information for a single username using output from last cmd
#
#use diagnostics;
use warnings;
use strict;
use feature ":5.10";

#if check to verify if exactly 1 command line argument was provided, if 0 or 
#more than 1 were provided, prints usage statement
if ($ARGV[0] ~~ undef || $ARGV[1])
{
	print "\nUsage: $0 <username>\n\n";
	exit;
}

#initializes variables to be used in program
my $input = $ARGV[0];
my $full_input = $input;
my @array = `last`;
my @target;
my $count = 1;
my $hours = 0;
my $minutes = 0;

#checks length of input username, if longer than 8 characters, 
#truncates input to match length of username in last's output
if (length $input > 8)
{
	$input = substr ($input, 0, 8);
}
	
#walks through the whole output from running last, then, if input
#is found, push that whole line into a new array, @target, and then
#print line to screen to display all unique sessions for username.
foreach my $line (@array)
{
	if ($line =~ /\b$input\b/)
	{
		#prints label for upcoming output on first trigger of 
		#if statement only
		print "\nHere is a listing of logins for $full_input:\n\n" 
		if $count ~~ 1;

		push(@target, $line);

		printf("%3d. $line", $count);
		$count++;
	}
}
	
#prints to screen statement identifying summary to be output below
print "\nHere is a summary of the time spent on the system for $full_input:\n\n";

#prints to screen full, untruncated input username
print "$full_input\n";

#prints the total number of logged in sessions
my $logons = @target;
print "$logons\n";

#this loop uses regular expressions to scrape the hours, minutes, and
#(if applicable) days the username was logged in using grouping with
#backreferencing to identify and separate the values. When the loop 
#proccesses a session that is not currently logged in, it adds the
#number of hours to the running total stored in $hours, and likewise for
#the minutes. If a days value is found, the number of days are converted
#to hours, and added to the scalar $hours as well.
foreach my $session (@target)
{
	if ($session =~ /\((\d)*\+*(\d\d):(\d\d)\)/)
	{
		$hours+=$2;
		$minutes+=$3;
		$hours += $1*24 if ($1);
	}
}

#section accounts for minute values greater than 59 minutes, and
#will convert each 60 minute interval to 1 hour, and adjust $hours and
#$minutes accordingly
$hours += int($minutes/60);
$minutes = $minutes % 60;

#print formatted number of hours and minutes logged in to the screen
printf ("%02d:%02d\n", $hours, $minutes);

say "";