#!/usr/bin/perl
use strict;
use warnings;
use File::Copy;
use File::Spec;
use File::Path qw(remove_tree make_path);
use File::Find;
use File::Basename;
use Cwd qw(getcwd abs_path);
use Time::HiRes qw(time);

my ($files, $depth, $total_commits, $file_perc, $change_perc) = @ARGV;
if (!defined $files || !defined $depth || !defined $total_commits || !defined $file_perc || !defined $change_perc) {
	die "Usage: perl bm_rebase.pl <file_count> <depth> <total_commits> <file_perc> <change_perc>\n";
}

my $base_dir = getcwd();
my $urn_bin  = abs_path(File::Spec->catfile("..", "urn")); 
my $seed_bin = abs_path("seed.pl");
my $bm_repo  = "sandbox";

my $sample_rate = int($total_commits / 5) || 1;
my %results;
my $initial_repo_size = "0 KB";
my $rebase_count = 0;
my %last_base_hashes;

my $global_tick = 0;

sub get_size {
	my $dir = shift;
	return "0 KB" unless -d $dir;
	my $size = `du -sk $dir 2>/dev/null`;
	$size =~ /^(\d+)/;
	return ($1 || 0) . " KB";
}

sub count_inodes {
	my $dir = shift;
	return 0 unless -d $dir;
	my $count = `find $dir 2>/dev/null | wc -l`;
	$count =~ s/\s+//g;
	return $count || 0;
}

sub track_rebases {
	return unless -f ".urn/index";
	open(my $fh, '<', ".urn/index") or return;
	while (<$fh>) {
		chomp;
		my @cols = split(/\t/);
		next unless @cols >= 6;
		my ($b_hash, $path) = ($cols[2], $cols[5]);
		if (exists $last_base_hashes{$path} && $last_base_hashes{$path} ne $b_hash) {
			$rebase_count++;
		}
		$last_base_hashes{$path} = $b_hash;
	}
	close($fh);
}

sub run_rebase_benchmark {
	my ($tool_name) = @_;
	print ">>> Starting REBASE BENCHMARK: $tool_name\n";

	remove_tree($bm_repo) if -d $bm_repo;
	system("perl $seed_bin $files $depth > /dev/null 2>&1");
	
	if ($initial_repo_size eq "0 KB") { $initial_repo_size = get_size($bm_repo); }
	
	chdir($bm_repo) or die $!;

	my $init_cmd = ($tool_name eq "URN") ? "perl $urn_bin init" : "git init";
	my $add_cmd  = ($tool_name eq "URN") ? "perl $urn_bin add ." : "git add .";
	
	system("$init_cmd > /dev/null 2>&1");
	system("$add_cmd > /dev/null 2>&1");
	system(($tool_name eq "URN" ? "perl $urn_bin" : "git") . " commit -m 'initial' > /dev/null 2>&1");
	
	track_rebases() if $tool_name eq "URN";

	my @file_list;
	find(sub { push @file_list, $File::Find::name if -f $_ && $File::Find::name !~ /\.(git|urn)/ }, ".");

	my $num_to_change = int(scalar(@file_list) * ($file_perc / 100)) || 1;
	my @target_files = @file_list[0 .. $num_to_change - 1];

	for my $i (2 .. $total_commits) {
		my $debug_dir = "/tmp/urn/commit_$i";
		make_path($debug_dir) unless -d $debug_dir;

		for my $target (@target_files) {
			open(my $fh, '<:raw', $target) or die "Read fail: $target - $!";
    		my $content = do { local $/; <$fh> };
    		close($fh);

    		$global_tick++;
    		my $ts = time();
    		my $header = "C$i-T$ts-N$global_tick ";
    		
    		my $total_bytes = length($content);
    		my $min_len = length($header);
    		my $to_change = int($total_bytes * ($change_perc / 100));

    		$to_change = $min_len if $to_change < $min_len;
    		$to_change = $total_bytes if $to_change > $total_bytes;

    		my $new_segment = substr($header . ("." x $to_change), 0, $to_change);
    		substr($content, 0, $to_change, $new_segment);

    		open(my $out, '>:raw', $target) or die "Write fail: $target - $!";
    		print $out $content;
    		close($out);

			my $target_name = basename($target);
			copy($target, "$debug_dir/$target_name") or warn "Backup failed: $!";
    		
    		utime(undef, undef, $target);
		}

		my $cmd = ($tool_name eq "URN") 
			? "perl $urn_bin add . && perl $urn_bin commit -m 'c$i'" 
			: "git add . && git commit -m 'c$i'";

		if ($i % $sample_rate == 0 || $i == $total_commits) {
			my $raw_output = `/usr/bin/time -l sh -c "$cmd" 2>&1`;

			if ($tool_name eq "URN") {
				track_rebases();
			}

			my ($real, $rss, $maj, $min) = (0, 0, 0, 0);
			$real = $1 if $raw_output =~ /(\d+\.\d+)\s+real/;
			$rss = sprintf("%.2f MB", $1 / 1024 / 1024) if $raw_output =~ /(\d+)\s+maximum resident set size/;
			$min = $1 if $raw_output =~ /(\d+)\s+page reclaims/;
			$maj = $1 if $raw_output =~ /(\d+)\s+page faults/;

			my $meta = ($tool_name eq "URN") ? ".urn" : ".git";
			$results{$i}{$tool_name} = {
				real   => $real . "s",
				rss    => $rss,
				faults => "Maj:$maj / Min:$min",
				inodes => count_inodes($meta),
				size   => get_size($meta),
			};
			print "   [Commit $i] $tool_name sampled.\n";
		} else {
			system("$cmd > /dev/null 2>&1");
			track_rebases() if $tool_name eq "URN";
		}
	}
	chdir($base_dir);
}

$rebase_count = 0;
%last_base_hashes = ();
run_rebase_benchmark("URN");
run_rebase_benchmark("GIT");

my $out_file = "BM_REBASE_${files}_${total_commits}.txt";
open(my $res, '>', $out_file) or die $!;
print $res "=============================================================\n";
print $res " REBASE BENCHMARK: $files files ($total_commits commits)\n";
print $res " CONDITIONS: Depth=$depth, Files Mod=$file_perc%, Change=$change_perc%\n";
print $res "=============================================================\n\n";

foreach my $i (sort { $a <=> $b } keys %results) {
	my $u = $results{$i}{"URN"};
	my $g = $results{$i}{"GIT"};
	print $res "SNAPSHOT: Commit #$i\n";
	print $res "-------------------------------------------------------------\n";
	printf $res "%-15s | %-20s | %-20s\n", "METRIC", "URN", "GIT";
	print $res "----------------+----------------------+---------------------\n";
	printf $res "%-15s | %20s | %20s\n", "Time", $u->{real}, $g->{real};
	printf $res "%-15s | %20s | %20s\n", "Max RSS", $u->{rss}, $g->{rss};
	printf $res "%-15s | %20s | %20s\n", "Page faults", $u->{faults}, $g->{faults};
	printf $res "%-15s | %20s | %20s\n", "Inodes", $u->{inodes}, $g->{inodes};
	printf $res "%-15s | %20s | %20s\n", "Repo size", $u->{size}, $g->{size};
	print $res "-------------------------------------------------------------\n\n";
}
print $res "TOTAL URN REBASES: $rebase_count\n";
close($res);

exec "less $out_file";