#! /usr/bin/perl -w

use strict;

if (@ARGV < 1 or $ARGV[0] eq 'default')
{
    print "usage: p4rollback <changelist>\n";
    exit;
}

foreach my $to (sort @ARGV)
{
    my ($from, $age);




    print "Looking up current changelist...\n";
    if (`p4 changes -m 1` =~ /Change ([0-9]+) on/)
    {
        $age = $1 - $to + 2;
    }
    else
    {
        print "Unable to lookup current changelist\n";
        exit;
    }




    print "Looking for previous changelist...\n";
    open CHANGELIST, "p4 changes -m $age |";

    while (<CHANGELIST>)
    {
        if (/Change ([0-9]+) on/ and $1 < $to)
        {
            $from = $1;
            last;
        }
    }

    close CHANGELIST;

    if ($from)
    {
        print "\nUndoing changes between changelist $from and changelist $to...\n";
    }
    else
    {
        print "Unable to lookup previous changelist\n";
        exit;
    }




    my (@edited, @deleted, @added, @branched, @integrated);
	my $message = '';

    print "\nReading changelist description...\n";
    open CHANGELIST, "p4 describe -s $to |";

    while (<CHANGELIST>)
	{
		last if (/Affected files/);

		$message .= " $_";
	}

    while (<CHANGELIST>)
    {
        my $line = Strip($_);

        if ($line =~ /^\.\.\. (.*)#[0-9]+ (edit|add|delete|branch|integrat)/)
        {
            print "$1 was $2ed\n";

            if ($2 eq "edit")
            {
                push @edited, $1;
            }
            elsif ($2 eq "integrat")
            {
                push @integrated, $1;
            }
            elsif ($2 eq "add")
            {
                push @added, $1;
            }
            elsif ($2 eq "delete")
            {
                push @deleted, $1;
            }
            elsif ($2 eq "branch")
            {
                push @branched, $1;
            }
        }
    }

    close CHANGELIST;




	open CHANGELIST, '>changelist.tmp';
    print CHANGELIST "Change: new\nDescription:\n Reverting change $to\n\n Original change description:\n\n";
    print CHANGELIST $message;
	close CHANGELIST;

    my $changelist = `p4 change -i < changelist.tmp`;

	unlink 'changelist.tmp';

    if ($changelist =~ /Change ([0-9]+) created./)
    {
        $changelist = $1;
        print "\nCreated new changelist: $changelist\n";
    }
    else
    {
        print "Unable to create new changelist: $changelist\n";
        exit;
    }





    if (@edited or @deleted or @integrated)
    {
        print "\nSyncing edited, integrated, and deleted files to old revision \@$from...\n";
        system("p4", "sync", map { "$_\@$from" } (@edited, @deleted, @integrated));

        print "\nAuto resolving edited, integrated, and deleted files...\n";
        system("p4", "resolve", "-am", @edited, @deleted, @integrated);

        if (@edited or @integrated)
        {
            print "\nOpening edited and integrated files for edit...\n";
            system("p4", "edit", "-c", $changelist, @edited, @integrated);
        }

        if (@deleted)
        {
            print "\nOpening deleted files for add...\n";
            system("p4", "add", "-c", $changelist, @deleted);
        }

        print "\nSyncing edited, integrated, and deleted files to new revision \@$to...\n";
        system("p4", "sync", map { "$_\@$to" } (@edited, @deleted, @integrated));

        print "\nResolving edited, integrated, and deleted files ignoring changes on server...\n";
        system("p4", "resolve", "-ay", @edited, @deleted, @integrated);
    }

    if (@added or @branched)
    {
        print "\nDeleting added and branched files...\n";
        system("p4", "delete", "-c", $changelist, @added, @branched);
    }


	system("p4", "changelist", "-d", $changelist);
}


sub Strip
{
    my $in = shift;
    $in =~ s/[^ -~]//go;
    return $in;
}