#!/usr/bin/perl

use strict;
use warnings;

use File::Basename;
use File::Spec;
use File::Temp;
use POSIX;

sub makeJob(\@$);
sub forkAndCompileFiles(\@$);
sub Exec($);
sub waitForChild(\@);
sub cleanup(\@);

my $debug = 0;

chomp(my $clexe = `cygpath -u '$ENV{'VS80COMNTOOLS'}/../../VC/bin/cl.exe'`);

if ($debug) {
    print STDERR "Received " . @ARGV . " arguments:\n";
    foreach my $arg (@ARGV) {
        print STDERR "$arg\n";
    }
}

my $commandFile;
foreach my $arg (@ARGV) {
    if ($arg =~ /^[\/-](E|EP|P)$/) {
        print STDERR "The invoking process wants preprocessed source, so let's hand off this whole command to the real cl.exe\n" if $debug;
        Exec("\"$clexe\" \"" . join('" "', @ARGV) . "\"");
    } elsif ($arg =~ /^@(.*)$/) {
        chomp($commandFile = `cygpath -u '$1'`);
    }
}

die "No command file specified!" unless $commandFile;
die "Couldn't find $commandFile!" unless -f $commandFile;

my @sources;

open(COMMAND, '<:raw:encoding(UTF16-LE):crlf:utf8', $commandFile) or die "Couldn't open $commandFile!";

# The first line of the command file contains all the options to cl.exe plus the first (possibly quoted) filename
my $firstLine = <COMMAND>;
$firstLine =~ s/\r?\n$//;

# To find the start of the first filename, look for either the last space on the line.
# If the filename is quoted, the last character on the line will be a quote, so look for the quote before that.
my $firstFileIndex;
print STDERR "Last character of first line = '" . substr($firstLine, -1, 1) . "'\n" if $debug;
if (substr($firstLine, -1, 1) eq '"') {
    print STDERR "First file is quoted\n" if $debug;
    $firstFileIndex = rindex($firstLine, '"', length($firstLine) - 2);
} else {
    print STDERR "First file is NOT quoted\n" if $debug;
    $firstFileIndex = rindex($firstLine, ' ') + 1;
}

my $options = substr($firstLine, 0, $firstFileIndex) . join(' ', @ARGV[1 .. $#ARGV]);
my $possibleFirstFile = substr($firstLine, $firstFileIndex);
if ($possibleFirstFile =~ /\.(cpp|c)/) {
    push(@sources, $possibleFirstFile);
} else {
    $options .= " $possibleFirstFile";
}

print STDERR "######## Found options $options ##########\n" if $debug;
print STDERR "####### Found first source file $sources[0] ########\n" if @sources && $debug;

# The rest of the lines of the command file just contain source files, one per line
while (my $source = <COMMAND>) {
    chomp($source);
    $source =~ s/^\s+//;
    $source =~ s/\s+$//;
    push(@sources, $source) if length($source);
}
close(COMMAND);

my $numSources = @sources;
exit unless $numSources > 0;

my $numJobs;
if ($options =~ s/-j\s*([0-9]+)//) {
    $numJobs = $1;
} else {
    chomp($numJobs = `num-cpus`);
}

print STDERR "\n\n####### RUNNING AT MOST $numJobs PARALLEL INSTANCES OF cl.exe ###########\n\n";# if $debug;

# Magic determination of job size
# The hope is that by splitting the source files up into 2*$numJobs pieces, we
# won't suffer too much if one job finishes much more quickly than another.
# However, we don't want to split it up too much due to cl.exe overhead, so set
# the minimum job size to 5.
my $jobSize = POSIX::ceil($numSources / (2 * $numJobs));
$jobSize = $jobSize < 5 ? 5 : $jobSize;

print STDERR "######## jobSize = $jobSize ##########\n" if $debug;

# Sort the source files randomly so that we don't end up with big clumps of large files (aka SVG)
sub fisher_yates_shuffle(\@)
{
    my ($array) = @_;
    for (my $i = @{$array}; --$i; ) {
        my $j = int(rand($i+1));
        next if $i == $j;
        @{$array}[$i,$j] = @{$array}[$j,$i];
    }
}

fisher_yates_shuffle(@sources);    # permutes @array in place

my @children;
my @tmpFiles;
my $status = 0;
while (@sources) {
    while (@sources && @children < $numJobs) {
        my $pid;
        my $tmpFile;
        my $job = makeJob(@sources, $jobSize);
        ($pid, $tmpFile) = forkAndCompileFiles(@{$job}, $options);

        print STDERR "####### Spawned child with PID $pid and tmpFile $tmpFile ##########\n" if $debug;
        push(@children, $pid);
        push(@tmpFiles, $tmpFile);
    }

    $status |= waitForChild(@children);
}

while (@children) {
    $status |= waitForChild(@children);
}
cleanup(@tmpFiles);

exit WEXITSTATUS($status);


sub makeJob(\@$)
{
    my ($files, $jobSize) = @_;

    my @job;
    if (@{$files} > ($jobSize * 1.5)) {
        @job = splice(@{$files}, -$jobSize);
    } else {
        # Compile all the remaining files in this job to avoid having a small job later
        @job = splice(@{$files});
    }

    return \@job;
}

sub forkAndCompileFiles(\@$)
{
    print STDERR "######## forkAndCompileFiles()\n" if $debug;
    my ($files, $options) = @_;

    if ($debug) {
        foreach my $file (@{$files}) {
            print STDERR "######## $file\n";
        }
    }

    my (undef, $tmpFile) = File::Temp::tempfile('clcommandXXXXX', DIR => File::Spec->tmpdir, OPEN => 0);

    my $pid = fork();
    die "Fork failed" unless defined($pid);

    unless ($pid) {
        # Child process
        open(TMP, '>:raw:encoding(UTF16-LE):crlf:utf8', $tmpFile) or die "Couldn't open $tmpFile";
        print TMP "$options\n";
        foreach my $file (@{$files}) {
            print TMP "$file\n";
        }
        close(TMP);
        
        chomp(my $winTmpFile = `cygpath -m $tmpFile`);
        Exec "\"$clexe\" \@\"$winTmpFile\"";
    } else {
        return ($pid, $tmpFile);
    }
}

sub Exec($)
{
    my ($command) = @_;

    print STDERR "Exec($command)\n" if $debug;

    exec($command);
}

sub waitForChild(\@)
{
    my ($children) = @_;

    return unless @{$children};

    my $deceased = wait();
    my $status = $?;
    print STDERR "######## Child with PID $deceased finished ###########\n" if $debug;
    for (my $i = 0; $i < @{$children}; $i++) {
        if ($children->[$i] == $deceased) {
            splice(@{$children}, $i, 1);
            last;
        }
    }

    return $status;
}

sub cleanup(\@)
{
    my ($tmpFiles) = @_;

    foreach my $file (@{$tmpFiles}) {
        unlink $file;
    }
}