#!/usr/bin/perl

open(INPUT, "aoc_7_A_input.txt");
@input = <INPUT>;
close(INPUT);

#The real deal

@allsteps = ('A'..'Z');
$finishline = 26;
$numberofworkers = 5;
$initialworktime = 60;

#Description Example

#@allsteps = ('A'..'F');
#$finishline = 6;
#$numberofworkers = 2;
#$initialworktime = 0;

## PART 1

$usteps = "";
%stepcompleted = ();

do {

%lockedsteps = ();
foreach $step (@input) {
#Lock all steps whose previous step has not been completed.
if ($step =~ m/^Step ([A-Z]) must be finished before step ([A-Z]) can begin.$/) {
if ($stepcompleted{$1} != 1) {
$lockedsteps{$2} = 1;
}
}
}

$nomore = 0;
for ($z = 0; $z < $#allsteps + 1; $z++) {

#Find first step whose is neither locked or completed.
if (($lockedsteps{$allsteps[$z]} != 1)&&($stepcompleted{$allsteps[$z]} != 1)&&($nomore == 0)) {
$stepcompleted{$allsteps[$z]} = 1;
$usteps = $usteps . $allsteps[$z];
$nomore = 1; #We only add one step at a time, then we must parse the locks again if any previous step become available.
}
}

} until (length($usteps) == $finishline);

# PART 2

%stepcompleted = ();
$steps = 0;
$totaltime = 0;
@workers = ();
@workduration = ();

do {
%lockedsteps = ();
foreach $step (@input) {
#Lock all steps whose previous step has not been completed.
if ($step =~ m/^Step ([A-Z]) must be finished before step ([A-Z]) can begin.$/) {
if ($stepcompleted{$1} != 1) {
$lockedsteps{$2} = 1;
}
}
}

for ($z = 0; $z < $#allsteps + 1; $z++) { #Scan for new work

#Find a nonlocked noncompleted step
if (($lockedsteps{$allsteps[$z]} != 1)&&($stepcompleted{$allsteps[$z]} != 1)) {
#If we have free workers, start assign process
if ($#workers < ($numberofworkers - 1)) {

$alreadyinprogress = 0;

foreach $wrk (@workers) {
if ($wrk eq $allsteps[$z]) {
$alreadyinprogress = 1; #Ensure we don't assign a work whose is already in progress by another elf.
}
}

if ($alreadyinprogress == 0) {
#Add work to a elf.
push(@workers, $allsteps[$z]);
push(@workduration, $initialworktime + int($z + 1));
#print "$totaltime .. Started work on $allsteps[$z], ". ($initialworktime + int($z + 1)) . " left\n";
}
}
}

} #For loop - done scanning for new work


for ($i = 0; $i < $numberofworkers; $i++) {
if (($workduration[$i] > 0)&&(length($workers[$i]) > 0)) {
$workduration[$i] = $workduration[$i] - 1; #decrease work in progress timer for all elfes that are currently working.
}
}

#increase total time worked.
$totaltime++;
#print "$totaltime .. W1(".$workers[0].",".$workduration[0].") W2(".$workers[1].",".$workduration[1].") W3(".$workers[2].",".$workduration[2].") W4(".$workers[3].",".$workduration[3].") W5(".$workers[4].",".$workduration[4].")\n";

for ($i = 0; $i < $numberofworkers; $i++) {

#If there is an assigned work ($workers[$i] with a length larger than 0) with a time left of 0, then that work is now complete.
if (($workduration[$i] == 0)&&(length($workers[$i]) > 0)) {
#Add step to completed work, so we know which steps that should not be locked during next iteration.
$stepcompleted{$workers[$i]} = 1;
#Increase count of completed steps so we know when we are completely done.
$steps++;
#print "$totaltime .. Finished work on $workers[$i]\n";
splice(@workers, $i, 1); #Delete work from the elf
splice(@workduration, $i, 1);
}
}

} until ($steps == $finishline);

print "PART 1: ".$usteps."\n";
print "PART 2: ".$totaltime."\n";