#!/usr/bin/perl -w

# This tool is copyright (c) 2005, Matthias Urlichs.
# It is released under the Gnu Public License, version 2.
#
# The basic idea is to pull and analyze SVN changes.
#
# Checking out the files is done by a single long-running SVN connection.
#
# The head revision is on branch "origin" by default.
# You can change that with the '-o' option.

require v5.8.0; # for shell-safe open("-|",LIST)
use strict;
use warnings;
use Getopt::Std;
use File::Spec;
use File::Temp qw(tempfile);
use File::Path qw(mkpath);
use File::Basename qw(basename dirname);
use Time::Local;
use IO::Pipe;
use POSIX qw(strftime dup2);
use IPC::Open2;
use SVN::Core;
use SVN::Ra;

die "Need CVN:Core 1.2.1 or better" if $SVN::Core::VERSION lt "1.2.1";

$SIG{'PIPE'}="IGNORE";
$ENV{'TZ'}="UTC";

our($opt_h,$opt_o,$opt_v,$opt_u,$opt_C,$opt_i,$opt_m,$opt_M,$opt_t,$opt_T,$opt_b,$opt_s,$opt_l,$opt_d,$opt_D);

sub usage() {
        print STDERR <<END;
Usage: ${\basename $0}     # fetch/update GIT from CVS
       [-o branch-for-HEAD] [-h] [-v] [-l max_num_changes]
       [-C GIT_repository] [-t tagname] [-T trunkname] [-b branchname]
       [-d|-D] [-i] [-u] [-s start_chg] [-m] [-M regex] [SVN_URL]
END
        exit(1);
}

getopts("b:C:dDhil:mM:o:s:t:T:uv") or usage();
usage if $opt_h;

my $tag_name = $opt_t || "tags";
my $trunk_name = $opt_T || "trunk";
my $branch_name = $opt_b || "branches";

@ARGV == 1 or @ARGV == 2 or usage();

$opt_o ||= "origin";
$opt_s ||= 1;
$opt_l = 100 unless defined $opt_l;
my $git_tree = $opt_C;
$git_tree ||= ".";

my $svn_url = $ARGV[0];
my $svn_dir = $ARGV[1];

our @mergerx = ();
if ($opt_m) {
        @mergerx = ( qr/\W(?:from|of|merge|merging|merged) (\w+)/i );
}
if ($opt_M) {
        push (@mergerx, qr/$opt_M/);
}

select(STDERR); $|=1; select(STDOUT);


package SVNconn;
# Basic SVN connection.
# We're only interested in connecting and downloading, so ...

use File::Spec;
use File::Temp qw(tempfile);
use POSIX qw(strftime dup2);

sub new {
        my($what,$repo) = @_;
        $what=ref($what) if ref($what);

        my $self = {};
        $self->{'buffer'} = "";
        bless($self,$what);

        $repo =~ s#/+$##;
        $self->{'fullrep'} = $repo;
        $self->conn();

        return $self;
}

sub conn {
        my $self = shift;
        my $repo = $self->{'fullrep'};
        my $s = SVN::Ra->new($repo);

        die "SVN connection to $repo: $!\n" unless defined $s;
        $self->{'svn'} = $s;
        $self->{'repo'} = $repo;
        $self->{'maxrev'} = $s->get_latest_revnum();
}

sub file {
        my($self,$path,$rev) = @_;

        my ($fh, $name) = tempfile('gitsvn.XXXXXX', 
                    DIR => File::Spec->tmpdir(), UNLINK => 1);

        print "... $rev $path ...\n" if $opt_v;
        eval { $self->{'svn'}->get_file($path,$rev,$fh); };
        if($@) {
                return undef if $@ =~ /Attempted to get checksum/;
                die $@;
        }
        close ($fh);

        return $name;
}

package main;
use URI;

my $svn = $svn_url;
$svn .= "/$svn_dir" if defined $svn_dir;
$svn = SVNconn->new($svn);

my $lwp_ua;
if($opt_d or $opt_D) {
        $svn_url = URI->new($svn_url)->canonical;
        if($opt_D) {
                $svn_dir =~ s#/*$#/#;
        } else {
                $svn_dir = "";
        }
        if ($svn_url->scheme eq "http") {
                use LWP::UserAgent;
                $lwp_ua = LWP::UserAgent->new(keep_alive => 1, requests_redirectable => []);
        } else {
                print STDERR "Warning: not HTTP; turning off direct file access\n";
                $opt_d=0;
        }
}

sub pdate($) {
        my($d) = @_;
        $d =~ m#(\d\d\d\d)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)#
                or die "Unparseable date: $d\n";
        my $y=$1; $y-=1900 if $y>1900;
        return timegm($6||0,$5,$4,$3,$2-1,$y);
}

sub getwd() {
        my $pwd = `pwd`;
        chomp $pwd;
        return $pwd;
}


sub get_headref($$) {
    my $name    = shift;
    my $git_dir = shift; 
    my $sha;
    
    if (open(C,"$git_dir/refs/heads/$name")) {
        chomp($sha = <C>);
        close(C);
        length($sha) == 40
            or die "Cannot get head id for $name ($sha): $!\n";
    }
    return $sha;
}


-d $git_tree
        or mkdir($git_tree,0777)
        or die "Could not create $git_tree: $!";
chdir($git_tree);

my $orig_branch = "";
my $forward_master = 0;
my %branches;

my $git_dir = $ENV{"GIT_DIR"} || ".git";
$git_dir = getwd()."/".$git_dir unless $git_dir =~ m#^/#;
$ENV{"GIT_DIR"} = $git_dir;
my $orig_git_index;
$orig_git_index = $ENV{GIT_INDEX_FILE} if exists $ENV{GIT_INDEX_FILE};
my ($git_ih, $git_index) = tempfile('gitXXXXXX', SUFFIX => '.idx',
                                    DIR => File::Spec->tmpdir());
close ($git_ih);
$ENV{GIT_INDEX_FILE} = $git_index;
my $maxnum = 0;
my $last_rev = "";
my $last_branch;
my $current_rev = $opt_s-1;
unless(-d $git_dir) {
        system("git-init-db");
        die "Cannot init the GIT db at $git_tree: $?\n" if $?;
        system("git-read-tree");
        die "Cannot init an empty tree: $?\n" if $?;

        $last_branch = $opt_o;
        $orig_branch = "";
} else {
        -f "$git_dir/refs/heads/$opt_o"
                or die "Branch '$opt_o' does not exist.\n".
                       "Either use the correct '-o branch' option,\n".
                       "or import to a new repository.\n";

        -f "$git_dir/svn2git"
                or die "'$git_dir/svn2git' does not exist.\n".
                       "You need that file for incremental imports.\n";
        $last_branch = basename(readlink("$git_dir/HEAD"));
        unless($last_branch) {
                warn "Cannot read the last branch name: $! -- assuming 'master'\n";
                $last_branch = "master";
        }
        $orig_branch = $last_branch;
        $last_rev = get_headref($orig_branch, $git_dir);
        if (-f "$git_dir/SVN2GIT_HEAD") {
                die <<EOM;
SVN2GIT_HEAD exists.
Make sure your working directory corresponds to HEAD and remove SVN2GIT_HEAD.
You may need to run

    git-read-tree -m -u SVN2GIT_HEAD HEAD
EOM
        }
        system('cp', "$git_dir/HEAD", "$git_dir/SVN2GIT_HEAD");

        $forward_master =
            $opt_o ne 'master' && -f "$git_dir/refs/heads/master" &&
            system('cmp', '-s', "$git_dir/refs/heads/master", 
                                "$git_dir/refs/heads/$opt_o") == 0;

        # populate index
        system('git-read-tree', $last_rev);
        die "read-tree failed: $?\n" if $?;

        # Get the last import timestamps
        open my $B,"<", "$git_dir/svn2git";
        while(<$B>) {
                chomp;
                my($num,$branch,$ref) = split;
                $branches{$branch}{$num} = $ref;
                $branches{$branch}{"LAST"} = $ref;
                $current_rev = $num if $current_rev < $num;
        }
        close($B);
}
-d $git_dir
        or die "Could not create git subdir ($git_dir).\n";

open BRANCHES,">>", "$git_dir/svn2git";

sub get_file($$$) {
        my($rev,$branch,$path) = @_;

        # revert split_path(), below
        my $svnpath;
        $path = "" if $path eq "/"; # this should not happen, but ...
        if($branch eq "/") {
                $svnpath = "/$trunk_name/$path";
        } elsif($branch =~ m#^/#) {
                $svnpath = "/$tag_name$branch/$path";
        } else {
                $svnpath = "/$branch_name/$branch/$path";
        }

        # now get it
        my $name;
        if($opt_d) {
                my($req,$res);

                # /svn/!svn/bc/2/django/trunk/django-docs/build.py
                my $url=$svn_url->clone();
                $url->path($url->path."/!svn/bc/$rev/$svn_dir$svnpath");
                print "Fetching $url...\n" if $opt_v;
                $req = HTTP::Request->new(GET => $url);
                $res = $lwp_ua->request($req);
                if ($res->is_success) {
                        my $fh;
                        ($fh, $name) = tempfile('gitsvn.XXXXXX', 
                        DIR => File::Spec->tmpdir(), UNLINK => 1);
                        print $fh $res->content;
                        close($fh) or die "Could not write $name: $!\n";
                } else {
                        return undef if $res->code == 301; # directory?
                        die $res->status_line." at $url\n";
                }
        } else {
                $name = $svn->file($svnpath,$rev);
                return undef unless defined $name;
        }

        open my $F, '-|', "git-hash-object", "-w", $name
                or die "Cannot create object: $!\n";
        my $sha = <$F>;
        chomp $sha;
        close $F;
        unlink $name;
        my $mode = "0644"; # SV does not seem to store any file modes
        return [$mode, $sha, $path];
}

sub split_path($$) {
        my($rev,$path) = @_;
        my $branch;

        if($path =~ s#^/\Q$tag_name\E/([^/]+)/?##) {
                $branch = "/$1";
        } elsif($path =~ s#^/\Q$trunk_name\E/?##) {
                $branch = "/";
        } elsif($path =~ s#^/\Q$branch_name\E/([^/]+)/?##) {
                $branch = $1;
        } else {
                print STDERR "$rev: Unrecognized path: $path\n";
                return ()
        }
        $path = "/" if $path eq "";
        return ($branch,$path);
}

sub commit {
        my($branch, $changed_paths, $revision, $author, $date, $message) = @_;
        my($author_name,$author_email,$dest);
        my(@old,@new);

        if (not defined $author) {
                $author_name = $author_email = "unknown";
        } elsif ($author =~ /^(.*?)\s+<(.*)>$/) {
                ($author_name, $author_email) = ($1, $2);
        } else {
                $author =~ s/^<(.*)>$/$1/;
                $author_name = $author_email = $author;
        }
        $date = pdate($date);

        my $tag;
        my $parent;
        if($branch eq "/") { # trunk
                $parent = $opt_o;
        } elsif($branch =~ m#^/(.+)#) { # tag
                $tag = 1;
                $parent = $1;
        } else { # "normal" branch
                # nothing to do
                $parent = $branch;
        }
        $dest = $parent;

        my $prev = $changed_paths->{"/"};
        if($prev and $prev->[0] eq "A") {
                delete $changed_paths->{"/"};
                my $oldpath = $prev->[1];
                my $rev;
                if(defined $oldpath) {
                        my $p;
                        ($parent,$p) = split_path($revision,$oldpath);
                        if($parent eq "/") {
                                $parent = $opt_o;
                        } else {
                                $parent =~ s#^/##; # if it's a tag
                        }
                } else {
                        $parent = undef;
                }
        }

        my $rev;
        if($revision > $opt_s and defined $parent) {
                open(H,"git-rev-parse --verify $parent |");
                $rev = <H>;
                close(H) or do {
                        print STDERR "$revision: cannot find commit '$parent'!\n";
                        return;
                };
                chop $rev;
                if(length($rev) != 40) {
                        print STDERR "$revision: cannot find commit '$parent'!\n";
                        return;
                }
                $rev = $branches{($parent eq $opt_o) ? "/" : $parent}{"LAST"};
                if($revision != $opt_s and not $rev) {
                        print STDERR "$revision: do not know ancestor for '$parent'!\n";
                        return;
                }
        } else {
                $rev = undef;
        }

#       if($prev and $prev->[0] eq "A") {
#               if(not $tag) {
#                       unless(open(H,"> $git_dir/refs/heads/$branch")) {
#                               print STDERR "$revision: Could not create branch $branch: $!\n";
#                               $state=11;
#                               next;
#                       }
#                       print H "$rev\n"
#                               or die "Could not write branch $branch: $!";
#                       close(H)
#                               or die "Could not write branch $branch: $!";
#               }
#       }
        if(not defined $rev) {
                unlink($git_index);
        } elsif ($rev ne $last_rev) {
                print "Switching from $last_rev to $rev ($branch)\n" if $opt_v;
                system("git-read-tree", $rev);
                die "read-tree failed for $rev: $?\n" if $?;
                $last_rev = $rev;
        }

        my $cid;
        if($tag and not %$changed_paths) {
                $cid = $rev;
        } else {
                while(my($path,$action) = each %$changed_paths) {
                        if ($action->[0] eq "A") {
                                my $f = get_file($revision,$branch,$path);
                                push(@new,$f) if $f;
                        } elsif ($action->[0] eq "D") {
                                push(@old,$path);
                        } elsif ($action->[0] eq "M") {
                                my $f = get_file($revision,$branch,$path);
                                push(@new,$f) if $f;
                        } elsif ($action->[0] eq "R") {
                                # refer to a file/tree in an earlier commit
                                push(@old,$path); # remove any old stuff

                                # ... and add any new stuff
                                my($b,$p) = split_path($revision,$action->[1]);
                                open my $F,"-|","git-ls-tree","-r","-z", $branches{$b}{$action->[2]}, $p;
                                local $/ = '\0';
                                while(<$F>) {
                                        chomp;
                                        my($m,$p) = split(/\t/,$_,2);
                                        my($mode,$type,$sha1) = split(/ /,$m);
                                        next if $type ne "blob";
                                        push(@new,[$mode,$sha1,$p]);
                                }
                        } else {
                                die "$revision: unknown action '".$action->[0]."' for $path\n";
                        }
                }

                if(@old) {
                        open my $F, "-|", "git-ls-files", "-z", @old or die $!;
                        @old = ();
                        local $/ = '\0';
                        while(<$F>) {
                                chomp;
                                push(@old,$_);
                        }
                        close($F);

                        while(@old) {
                                my @o2;
                                if(@old > 55) {
                                        @o2 = splice(@old,0,50);
                                } else {
                                        @o2 = @old;
                                        @old = ();
                                }
                                system("git-update-index","--force-remove","--",@o2);
                                die "Cannot remove files: $?\n" if $?;
                        }
                }
                while(@new) {
                        my @n2;
                        if(@new > 12) {
                                @n2 = splice(@new,0,10);
                        } else {
                                @n2 = @new;
                                @new = ();
                        }
                        system("git-update-index","--add",
                                (map { ('--cacheinfo', @$_) } @n2));
                        die "Cannot add files: $?\n" if $?;
                }

                my $pid = open(C,"-|");
                die "Cannot fork: $!" unless defined $pid;
                unless($pid) {
                        exec("git-write-tree");
                        die "Cannot exec git-write-tree: $!\n";
                }
                chomp(my $tree = <C>);
                length($tree) == 40
                        or die "Cannot get tree id ($tree): $!\n";
                close(C)
                        or die "Error running git-write-tree: $?\n";
                print "Tree ID $tree\n" if $opt_v;

                my $pr = IO::Pipe->new() or die "Cannot open pipe: $!\n";
                my $pw = IO::Pipe->new() or die "Cannot open pipe: $!\n";
                $pid = fork();
                die "Fork: $!\n" unless defined $pid;
                unless($pid) {
                        $pr->writer();
                        $pw->reader();
                        open(OUT,">&STDOUT");
                        dup2($pw->fileno(),0);
                        dup2($pr->fileno(),1);
                        $pr->close();
                        $pw->close();

                        my @par = ();
                        @par = ("-p",$rev) if defined $rev;

                        # loose detection of merges
                        # based on the commit msg
                        foreach my $rx (@mergerx) {
                                if ($message =~ $rx) {
                                        my $mparent = $1;
                                        if ($mparent eq 'HEAD') { $mparent = $opt_o };
                                        if ( -e "$git_dir/refs/heads/$mparent") {
                                                $mparent = get_headref($mparent, $git_dir);
                                                push @par, '-p', $mparent;
                                                print OUT "Merge parent branch: $mparent\n" if $opt_v;
                                        }
                                } 
                        }

                        exec("env",
                                "GIT_AUTHOR_NAME=$author_name",
                                "GIT_AUTHOR_EMAIL=$author_email",
                                "GIT_AUTHOR_DATE=".strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date)),
                                "GIT_COMMITTER_NAME=$author_name",
                                "GIT_COMMITTER_EMAIL=$author_email",
                                "GIT_COMMITTER_DATE=".strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date)),
                                "git-commit-tree", $tree,@par);
                        die "Cannot exec git-commit-tree: $!\n";
                }
                $pw->writer();
                $pr->reader();

                $message =~ s/[\s\n]+\z//;

                print $pw "$message\n"
                        or die "Error writing to git-commit-tree: $!\n";
                $pw->close();

                print "Committed change $revision:$branch ".strftime("%Y-%m-%d %H:%M:%S",gmtime($date)).")\n" if $opt_v;
                chomp($cid = <$pr>);
                length($cid) == 40
                        or die "Cannot get commit id ($cid): $!\n";
                print "Commit ID $cid\n" if $opt_v;
                $pr->close();

                waitpid($pid,0);
                die "Error running git-commit-tree: $?\n" if $?;
        }

        if(not defined $dest) {
                print "... no known parent\n" if $opt_v;
        } elsif(not $tag) {
                print "Writing to refs/heads/$dest\n" if $opt_v;
                open(C,">$git_dir/refs/heads/$dest") and 
                print C ("$cid\n") and
                close(C)
                        or die "Cannot write branch $dest for update: $!\n";
        }

        if($tag) {
                my($in, $out) = ('','');
                $last_rev = "-" if %$changed_paths;
                # the tag was 'complex', i.e. did not refer to a "real" revision
                
                $dest =~ tr/_/\./ if $opt_u;

                my $pid = open2($in, $out, 'git-mktag');
                print $out ("object $cid\n".
                    "type commit\n".
                    "tag $dest\n".
                    "tagger $author_name <$author_email>\n") and
                close($out)
                    or die "Cannot create tag object $dest: $!\n";

                my $tagobj = <$in>;
                chomp $tagobj;

                if ( !close($in) or waitpid($pid, 0) != $pid or
                                $? != 0 or $tagobj !~ /^[0123456789abcdef]{40}$/ ) {
                        die "Cannot create tag object $dest: $!\n";
                }

                open(C,">$git_dir/refs/tags/$dest") and
                print C ("$tagobj\n") and
                close(C)
                        or die "Cannot create tag $branch: $!\n";

                print "Created tag '$dest' on '$branch'\n" if $opt_v;
        }
        $branches{$branch}{"LAST"} = $cid;
        $branches{$branch}{$revision} = $cid;
        $last_rev = $cid;
        print BRANCHES "$revision $branch $cid\n";
        print "DONE: $revision $dest $cid\n" if $opt_v;
}

my ($changed_paths, $revision, $author, $date, $message, $pool) = @_;
sub _commit_all {
        ($changed_paths, $revision, $author, $date, $message, $pool) = @_;
        my %p;
        while(my($path,$action) = each %$changed_paths) {
                $p{$path} = [ $action->action,$action->copyfrom_path, $action->copyfrom_rev ];
        }
        $changed_paths = \%p;
}

sub commit_all {
        my %done;
        my @col;
        my $pref;
        my $branch;

        while(my($path,$action) = each %$changed_paths) {
                ($branch,$path) = split_path($revision,$path);
                next if not defined $branch;
                $done{$branch}{$path} = $action;
        }
        while(($branch,$changed_paths) = each %done) {
                commit($branch, $changed_paths, $revision, $author, $date, $message);
        }
}

while(++$current_rev <= $svn->{'maxrev'}) {
        $svn->{'svn'}->get_log("/",$current_rev,$current_rev,$current_rev,1,1,\&_commit_all,"");
        commit_all();
        if($opt_l and not --$opt_l) {
                print STDERR "Exiting due to a memory leak. Repeat, please.\n";
                last;
        }
}


unlink($git_index);

if (defined $orig_git_index) {
        $ENV{GIT_INDEX_FILE} = $orig_git_index;
} else {
        delete $ENV{GIT_INDEX_FILE};
}

# Now switch back to the branch we were in before all of this happened
if($orig_branch) {
        print "DONE\n" if $opt_v and (not defined $opt_l or $opt_l > 0);
        system("cp","$git_dir/refs/heads/$opt_o","$git_dir/refs/heads/master")
                if $forward_master;
        unless ($opt_i) {
                system('git-read-tree', '-m', '-u', 'SVN2GIT_HEAD', 'HEAD');
                die "read-tree failed: $?\n" if $?;
        }
} else {
        $orig_branch = "master";
        print "DONE; creating $orig_branch branch\n" if $opt_v and (not defined $opt_l or $opt_l > 0);
        system("cp","$git_dir/refs/heads/$opt_o","$git_dir/refs/heads/master")
                unless -f "$git_dir/refs/heads/master";
        unlink("$git_dir/HEAD");
        symlink("refs/heads/$orig_branch","$git_dir/HEAD");
        unless ($opt_i) {
                system('git checkout');
                die "checkout failed: $?\n" if $?;
        }
}
unlink("$git_dir/SVN2GIT_HEAD");
close(BRANCHES);