#!/usr/bin/perl -w
#
# This tool is copyright (c) 2005, Martin Langhoff.
# It is released under the Gnu Public License, version 2.
#
# The basic idea is to walk the output of tla abrowse, 
# fetch the changesets and apply them. 
#
=head1 Invocation

    git-archimport -i <archive>/<branch> [<archive>/<branch>]
    [ <archive>/<branch> ]

    The script expects you to provide the key roots where it can start the
    import from an 'initial import' or 'tag' type of Arch commit. It will
    then follow all the branching and tagging within the provided roots.

    It will die if it sees branches that have different roots. 

=head2 TODO

 - keep track of merged patches, and mark a git merge when it happens
 - smarter rules to parse the archive history "up" and "down"
 - be able to continue an import where we left off
 - audit shell-escaping of filenames

=head1 Devel tricks

Add print in front of the shell commands invoked via backticks. 

=cut

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 String::ShellQuote;
use Time::Local;
use IO::Socket;
use IO::Pipe;
use POSIX qw(strftime dup2);
use Data::Dumper qw/ Dumper /;
use IPC::Open2;

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

our($opt_h,$opt_v, $opt_T,
    $opt_C,$opt_t);

sub usage() {
    print STDERR <<END;
Usage: ${\basename $0}     # fetch/update GIT from Arch
       [ -h ] [ -v ] [ -T ] 
       [ -C GIT_repository ] [ -t tempdir ] 
       repository/arch-branch [ repository/arch-branch] ...
END
    exit(1);
}

getopts("ThviC:t:") or usage();
usage if $opt_h;

@ARGV >= 1 or usage();
my @arch_roots = @ARGV;

my $tmp = $opt_t;
$tmp ||= '/tmp';
$tmp .= '/git-archimport/';

my $git_tree = $opt_C;
$git_tree ||= ".";


my @psets  = ();                # the collection
my %psets  = ();                # the collection, by name

my %rptags = ();                # my reverse private tags
                                # to map a SHA1 to a commitid

foreach my $root (@arch_roots) {
    my ($arepo, $abranch) = split(m!/!, $root);
    open ABROWSE, "tla abrowse -f -A $arepo --desc --merges $abranch |" 
        or die "Problems with tla abrowse: $!";
    
    my %ps        = ();         # the current one
    my $mode      = '';
    my $lastseen  = '';
    
    while (<ABROWSE>) {
        chomp;
        
        # first record padded w 8 spaces
        if (s/^\s{8}\b//) {
            
            # store the record we just captured
            if (%ps) {
                my %temp = %ps; # break references
                push (@psets, \%temp);
                $psets{$temp{id}} = \%temp;
                %ps = ();
            }
            
            my ($id, $type) = split(m/\s{3}/, $_);
            $ps{id}   = $id;
            $ps{repo} = $arepo;

            # deal with types
            if ($type =~ m/^\(simple changeset\)/) {
                $ps{type} = 's';
            } elsif ($type eq '(initial import)') {
                $ps{type} = 'i';
            } elsif ($type =~ m/^\(tag revision of (.+)\)/) {
                $ps{type} = 't';
                $ps{tag}  = $1;
            } else { 
                warn "Unknown type $type";
            }
            $lastseen = 'id';
        }
        
        if (s/^\s{10}//) { 
            # 10 leading spaces or more 
            # indicate commit metadata
            
            # date & author 
            if ($lastseen eq 'id' && m/^\d{4}-\d{2}-\d{2}/) {
                
                my ($date, $authoremail) = split(m/\s{2,}/, $_);
                $ps{date}   = $date;
                $ps{date}   =~ s/\bGMT$//; # strip off trailign GMT
                if ($ps{date} =~ m/\b\w+$/) {
                    warn 'Arch dates not in GMT?! - imported dates will be wrong';
                }
            
                $authoremail =~ m/^(.+)\s(\S+)$/;
                $ps{author} = $1;
                $ps{email}  = $2;
            
                $lastseen = 'date';
            
            } elsif ($lastseen eq 'date') {
                # the only hint is position
                # subject is after date
                $ps{subj} = $_;
                $lastseen = 'subj';
            
            } elsif ($lastseen eq 'subj' && $_ eq 'merges in:') {
                $ps{merges} = [];
                $lastseen = 'merges';
            
            } elsif ($lastseen eq 'merges' && s/^\s{2}//) {
                push (@{$ps{merges}}, $_);
            } else {
                warn 'more metadata after merges!?';
            }
            
        }
    }

    if (%ps) {
        my %temp = %ps;         # break references
        push (@psets, \%temp);  
        $psets{ $temp{id} } = \%temp;
        %ps = ();
    }    
    close ABROWSE;
}                               # end foreach $root

## Order patches by time
@psets = sort {$a->{date}.$b->{id} cmp $b->{date}.$b->{id}} @psets;

#print Dumper \@psets;

##
## TODO cleanup irrelevant patches
##      and put an initial import
##      or a full tag
my $import = 0;
unless (-d '.git') { # initial import
    if ($psets[0]{type} eq 'i' || $psets[0]{type} eq 't') {
        print "Starting import from $psets[0]{id}\n";
        `git-init-db`;
        die $! if $?;
        $import = 1;
    } else {
        die "Need to start from an import or a tag -- cannot use $psets[0]{id}";
    }
} else {    # progressing an import
    # load the rptags
    opendir(DIR, ".git/archimport/tags")
        || die "can't opendir: $!";
    while (my $file = readdir(DIR)) {
        # skip non-interesting-files
        next unless -f ".git/archimport/tags/$file";
        next if     $file =~ m/--base-0$/; # don't care for base-0
        my $sha = ptag($file);
        chomp $sha;
        # reconvert the 3rd '--' sequence from the end
        # into a slash
        # $file = reverse $file;
        # $file =~ s!^(.+?--.+?--.+?--.+?)--(.+)$!$1/$2!;
        # $file = reverse $file;
        $rptags{$sha} = $file;
    }
    closedir DIR;
}

# process patchsets
foreach my $ps (@psets) {

    $ps->{branch} =  branchname($ps->{id});

    #
    # ensure we have a clean state 
    # 
    if (`git diff-files`) {
        die "Unclean tree when about to process $ps->{id} " .
            " - did we fail to commit cleanly before?";
    }
    die $! if $?;

    #
    # skip commits already in repo
    #
    if (ptag($ps->{id})) {
      $opt_v && print "Skipping already imported: $ps->{id}\n";
      next;
    }

    # 
    # create the branch if needed
    #
    if ($ps->{type} eq 'i' && !$import) {
        die "Should not have more than one 'Initial import' per GIT import: $ps->{id}";
    }

    unless ($import) { # skip for import
        if ( -e ".git/refs/heads/$ps->{branch}") {
            # we know about this branch
            `git checkout    $ps->{branch}`;
        } else {
            # new branch! we need to verify a few things
            die "Branch on a non-tag!" unless $ps->{type} eq 't';
            my $branchpoint = ptag($ps->{tag});
            die "Tagging from unknown id unsupported: $ps->{tag}" 
                unless $branchpoint;
            
            # find where we are supposed to branch from
            `git checkout -b $ps->{branch} $branchpoint`;

            # If we trust Arch with the fact that this is just 
            # a tag, and it does not affect the state of the tree
            # then we just tag and move on
            tag($ps->{id}, $branchpoint);
            ptag($ps->{id}, $branchpoint);
            print " * Tagged $ps->{id} at $branchpoint\n";
            next;
        } 
        die $! if $?;
    } 

    #
    # Apply the import/changeset/merge into the working tree
    # 
    if ($ps->{type} eq 'i' || $ps->{type} eq 't') {
        apply_import($ps) or die $!;
        $import=0;
    } elsif ($ps->{type} eq 's') {
        apply_cset($ps);
    }

    #
    # prepare update git's index, based on what arch knows
    # about the pset, resolve parents, etc
    #
    my $tree;
    
    my $commitlog = `tla cat-archive-log -A $ps->{repo} $ps->{id}`; 
    die "Error in cat-archive-log: $!" if $?;
        
    # parselog will git-add/rm files
    # and generally prepare things for the commit
    # NOTE: parselog will shell-quote filenames! 
    my ($sum, $msg, $add, $del, $mod, $ren) = parselog($commitlog);
    my $logmessage = "$sum\n$msg";


    # imports don't give us good info
    # on added files. Shame on them
    if ($ps->{type} eq 'i' || $ps->{type} eq 't') { 
        `find . -type f -print0 | grep -zv '^./.git' | xargs -0 -l100 git-update-index --add`;
        `git-ls-files --deleted -z | xargs --no-run-if-empty -0 -l100 git-update-index --remove`;
    }

    if (@$add) {
        while (@$add) {
            my @slice = splice(@$add, 0, 100);
            my $slice = join(' ', @slice);          
            `git-update-index --add $slice`;
            die "Error in git-update-index --add: $!" if $?;
        }
    }
    if (@$del) {
        foreach my $file (@$del) {
            unlink $file or die "Problems deleting $file : $!";
        }
        while (@$del) {
            my @slice = splice(@$del, 0, 100);
            my $slice = join(' ', @slice);
            `git-update-index --remove $slice`;
            die "Error in git-update-index --remove: $!" if $?;
        }
    }
    if (@$ren) {                # renamed
        if (@$ren % 2) {
            die "Odd number of entries in rename!?";
        }
        ;
        while (@$ren) {
            my $from = pop @$ren;
            my $to   = pop @$ren;           

            unless (-d dirname($to)) {
                mkpath(dirname($to)); # will die on err
            }
            #print "moving $from $to";
            `mv $from $to`;
            die "Error renaming $from $to : $!" if $?;
            `git-update-index --remove $from`;
            die "Error in git-update-index --remove: $!" if $?;
            `git-update-index --add $to`;
            die "Error in git-update-index --add: $!" if $?;
        }

    }
    if (@$mod) {                # must be _after_ renames
        while (@$mod) {
            my @slice = splice(@$mod, 0, 100);
            my $slice = join(' ', @slice);
            `git-update-index $slice`;
            die "Error in git-update-index: $!" if $?;
        }
    }

    # warn "errors when running git-update-index! $!";
    $tree = `git-write-tree`;
    die "cannot write tree $!" if $?;
    chomp $tree;
        
    
    #
    # Who's your daddy?
    #
    my @par;
    if ( -e ".git/refs/heads/$ps->{branch}") {
        if (open HEAD, "<.git/refs/heads/$ps->{branch}") {
            my $p = <HEAD>;
            close HEAD;
            chomp $p;
            push @par, '-p', $p;
        } else { 
            if ($ps->{type} eq 's') {
                warn "Could not find the right head for the branch $ps->{branch}";
            }
        }
    }
    
    if ($ps->{merges}) {
        push @par, find_parents($ps);
    }
    my $par = join (' ', @par);

    #    
    # Commit, tag and clean state
    #
    $ENV{TZ}                  = 'GMT';
    $ENV{GIT_AUTHOR_NAME}     = $ps->{author};
    $ENV{GIT_AUTHOR_EMAIL}    = $ps->{email};
    $ENV{GIT_AUTHOR_DATE}     = $ps->{date};
    $ENV{GIT_COMMITTER_NAME}  = $ps->{author};
    $ENV{GIT_COMMITTER_EMAIL} = $ps->{email};
    $ENV{GIT_COMMITTER_DATE}  = $ps->{date};

    my ($pid, $commit_rh, $commit_wh);
    $commit_rh = 'commit_rh';
    $commit_wh = 'commit_wh';
    
    $pid = open2(*READER, *WRITER, "git-commit-tree $tree $par") 
        or die $!;
    print WRITER $logmessage;   # write
    close WRITER;
    my $commitid = <READER>;    # read
    chomp $commitid;
    close READER;
    waitpid $pid,0;             # close;

    if (length $commitid != 40) {
        die "Something went wrong with the commit! $! $commitid";
    }
    #
    # Update the branch
    # 
    open  HEAD, ">.git/refs/heads/$ps->{branch}";
    print HEAD $commitid;
    close HEAD;
    unlink ('.git/HEAD');
    symlink("refs/heads/$ps->{branch}",".git/HEAD");

    # tag accordingly
    ptag($ps->{id}, $commitid); # private tag
    if ($opt_T || $ps->{type} eq 't' || $ps->{type} eq 'i') {
        tag($ps->{id}, $commitid);
    }
    print " * Committed $ps->{id}\n";
    print "   + tree   $tree\n";
    print "   + commit $commitid\n";
    $opt_v && print "   + commit date is  $ps->{date} \n";
    $opt_v && print "   + parents:  $par \n";
}

sub branchname {
    my $id = shift;
    $id =~ s#^.+?/##;
    my @parts = split(m/--/, $id);
    return join('--', @parts[0..1]);
}

sub apply_import {
    my $ps = shift;
    my $bname = branchname($ps->{id});

    `mkdir -p $tmp`;

    `tla get -s --no-pristine -A $ps->{repo} $ps->{id} $tmp/import`;
    die "Cannot get import: $!" if $?;    
    `rsync -v --archive --delete --exclude '.git' --exclude '.arch-ids' --exclude '{arch}' $tmp/import/* ./`;
    die "Cannot rsync import:$!" if $?;
    
    `rm -fr $tmp/import`;
    die "Cannot remove tempdir: $!" if $?;
    

    return 1;
}

sub apply_cset {
    my $ps = shift;

    `mkdir -p $tmp`;

    # get the changeset
    `tla get-changeset  -A $ps->{repo} $ps->{id} $tmp/changeset`;
    die "Cannot get changeset: $!" if $?;
    
    # apply patches
    if (`find $tmp/changeset/patches -type f -name '*.patch'`) {
        # this can be sped up considerably by doing
        #    (find | xargs cat) | patch
        # but that cna get mucked up by patches
        # with missing trailing newlines or the standard 
        # 'missing newline' flag in the patch - possibly
        # produced with an old/buggy diff.
        # slow and safe, we invoke patch once per patchfile
        `find $tmp/changeset/patches -type f -name '*.patch' -print0 | grep -zv '{arch}' | xargs -iFILE -0 --no-run-if-empty patch -p1 --forward -iFILE`;
        die "Problem applying patches! $!" if $?;
    }

    # apply changed binary files
    if (my @modified = `find $tmp/changeset/patches -type f -name '*.modified'`) {
        foreach my $mod (@modified) {
            chomp $mod;
            my $orig = $mod;
            $orig =~ s/\.modified$//; # lazy
            $orig =~ s!^\Q$tmp\E/changeset/patches/!!;
            #print "rsync -p '$mod' '$orig'";
            `rsync -p $mod ./$orig`;
            die "Problem applying binary changes! $!" if $?;
        }
    }

    # bring in new files
    `rsync --archive --exclude '.git' --exclude '.arch-ids' --exclude '{arch}' $tmp/changeset/new-files-archive/* ./`;

    # deleted files are hinted from the commitlog processing

    `rm -fr $tmp/changeset`;
}


# =for reference
# A log entry looks like 
# Revision: moodle-org--moodle--1.3.3--patch-15
# Archive: arch-eduforge@catalyst.net.nz--2004
# Creator: Penny Leach <penny@catalyst.net.nz>
# Date: Wed May 25 14:15:34 NZST 2005
# Standard-date: 2005-05-25 02:15:34 GMT
# New-files: lang/de/.arch-ids/block_glossary_random.php.id
#     lang/de/.arch-ids/block_html.php.id
# New-directories: lang/de/help/questionnaire
#     lang/de/help/questionnaire/.arch-ids
# Renamed-files: .arch-ids/db_sears.sql.id db/.arch-ids/db_sears.sql.id
#    db_sears.sql db/db_sears.sql
# Removed-files: lang/be/docs/.arch-ids/release.html.id
#     lang/be/docs/.arch-ids/releaseold.html.id
# Modified-files: admin/cron.php admin/delete.php
#     admin/editor.html backup/lib.php backup/restore.php
# New-patches: arch-eduforge@catalyst.net.nz--2004/moodle-org--moodle--1.3.3--patch-15
# Summary: Updating to latest from MOODLE_14_STABLE (1.4.5+)
# Keywords:
#
# Updating yadda tadda tadda madda
sub parselog {
    my $log = shift;
    #print $log;

    my (@add, @del, @mod, @ren, @kw, $sum, $msg );

    if ($log =~ m/(?:\n|^)New-files:(.*?)(?=\n\w)/s ) {
        my $files = $1;
        @add = split(m/\s+/s, $files);
    }
       
    if ($log =~ m/(?:\n|^)Removed-files:(.*?)(?=\n\w)/s ) {
        my $files = $1;
        @del = split(m/\s+/s, $files);
    }
    
    if ($log =~ m/(?:\n|^)Modified-files:(.*?)(?=\n\w)/s ) {
        my $files = $1;
        @mod = split(m/\s+/s, $files);
    }
    
    if ($log =~ m/(?:\n|^)Renamed-files:(.*?)(?=\n\w)/s ) {
        my $files = $1;
        @ren = split(m/\s+/s, $files);
    }

    $sum ='';
    if ($log =~ m/^Summary:(.+?)$/m ) {
        $sum = $1;
        $sum =~ s/^\s+//;
        $sum =~ s/\s+$//;
    }

    $msg = '';
    if ($log =~ m/\n\n(.+)$/s) {
        $msg = $1;
        $msg =~ s/^\s+//;
        $msg =~ s/\s+$//;
    }


    # cleanup the arrays
    foreach my $ref ( (\@add, \@del, \@mod, \@ren) ) {
        my @tmp = ();
        while (my $t = pop @$ref) {
            next unless length ($t);
            next if $t =~ m!\{arch\}/!;
            next if $t =~ m!\.arch-ids/!;
            next if $t =~ m!\.arch-inventory$!;
            push (@tmp, shell_quote($t));
        }
        @$ref = @tmp;
    }
    
    #print Dumper [$sum, $msg, \@add, \@del, \@mod, \@ren]; 
    return       ($sum, $msg, \@add, \@del, \@mod, \@ren); 
}

# write/read a tag
sub tag {
    my ($tag, $commit) = @_;
    $tag =~ s|/|--|g; 
    $tag = shell_quote($tag);
    
    if ($commit) {
        open(C,">.git/refs/tags/$tag")
            or die "Cannot create tag $tag: $!\n";
        print C "$commit\n"
            or die "Cannot write tag $tag: $!\n";
        close(C)
            or die "Cannot write tag $tag: $!\n";
        print " * Created tag ' $tag' on '$commit'\n" if $opt_v;
    } else {                    # read
        open(C,"<.git/refs/tags/$tag")
            or die "Cannot read tag $tag: $!\n";
        $commit = <C>;
        chomp $commit;
        die "Error reading tag $tag: $!\n" unless length $commit == 40;
        close(C)
            or die "Cannot read tag $tag: $!\n";
        return $commit;
    }
}

# write/read a private tag
# reads fail softly if the tag isn't there
sub ptag {
    my ($tag, $commit) = @_;
    $tag =~ s|/|--|g; 
    $tag = shell_quote($tag);
    
    unless (-d '.git/archimport/tags') {
        mkpath('.git/archimport/tags');
    }

    if ($commit) {              # write
        open(C,">.git/archimport/tags/$tag")
            or die "Cannot create tag $tag: $!\n";
        print C "$commit\n"
            or die "Cannot write tag $tag: $!\n";
        close(C)
            or die "Cannot write tag $tag: $!\n";
        $rptags{$commit} = $tag 
            unless $tag =~ m/--base-0$/;
    } else {                    # read
        # if the tag isn't there, return 0
        unless ( -s ".git/archimport/tags/$tag") {
            return 0;
        }
        open(C,"<.git/archimport/tags/$tag")
            or die "Cannot read tag $tag: $!\n";
        $commit = <C>;
        chomp $commit;
        die "Error reading tag $tag: $!\n" unless length $commit == 40;
        close(C)
            or die "Cannot read tag $tag: $!\n";
        unless (defined $rptags{$commit}) {
            $rptags{$commit} = $tag;
        }
        return $commit;
    }
}

sub find_parents {
    #
    # Identify what branches are merging into me
    # and whether we are fully merged
    # git-merge-base <headsha> <headsha> should tell
    # me what the base of the merge should be 
    #
    my $ps = shift;

    my %branches; # holds an arrayref per branch
                  # the arrayref contains a list of
                  # merged patches between the base
                  # of the merge and the current head

    my @parents;  # parents found for this commit

    # simple loop to split the merges
    # per branch
    foreach my $merge (@{$ps->{merges}}) {
        my $branch = branchname($merge);
        unless (defined $branches{$branch} ){
            $branches{$branch} = [];
        }
        push @{$branches{$branch}}, $merge;
    }

    #
    # foreach branch find a merge base and walk it to the 
    # head where we are, collecting the merged patchsets that
    # Arch has recorded. Keep that in @have
    # Compare that with the commits on the other branch
    # between merge-base and the tip of the branch (@need)
    # and see if we have a series of consecutive patches
    # starting from the merge base. The tip of the series
    # of consecutive patches merged is our new parent for 
    # that branch.
    #
    foreach my $branch (keys %branches) {
        my $mergebase = `git-merge-base $branch $ps->{branch}`;
        die "Cannot find merge base for $branch and $ps->{branch}" if $?;
        chomp $mergebase;

        # now walk up to the mergepoint collecting what patches we have
        my $branchtip = git_rev_parse($ps->{branch});
        my @ancestors = `git-rev-list --merge-order $branchtip ^$mergebase`;
        my %have; # collected merges this branch has
        foreach my $merge (@{$ps->{merges}}) {
            $have{$merge} = 1;
        }
        my %ancestorshave;
        foreach my $par (@ancestors) {
            $par = commitid2pset($par);
            if (defined $par->{merges}) {
                foreach my $merge (@{$par->{merges}}) {
                    $ancestorshave{$merge}=1;
                }
            }
        }
        # print "++++ Merges in $ps->{id} are....\n";
        # my @have = sort keys %have;   print Dumper(\@have);

        # merge what we have with what ancestors have
        %have = (%have, %ancestorshave);

        # see what the remote branch has - these are the merges we 
        # will want to have in a consecutive series from the mergebase
        my $otherbranchtip = git_rev_parse($branch);
        my @needraw = `git-rev-list --merge-order $otherbranchtip ^$mergebase`;
        my @need;
        foreach my $needps (@needraw) {         # get the psets
            $needps = commitid2pset($needps);
            # git-rev-list will also
            # list commits merged in via earlier 
            # merges. we are only interested in commits
            # from the branch we're looking at
            if ($branch eq $needps->{branch}) {
                push @need, $needps->{id};
            }
        }

        # print "++++ Merges from $branch we want are....\n";
        # print Dumper(\@need);

        my $newparent;
        while (my $needed_commit = pop @need) {
            if ($have{$needed_commit}) {
                $newparent = $needed_commit;
            } else {
                last; # break out of the while
            }
        }
        if ($newparent) {
            push @parents, $newparent;
        }


    } # end foreach branch

    # prune redundant parents
    my %parents;
    foreach my $p (@parents) {
        $parents{$p} = 1;
    }
    foreach my $p (@parents) {
        next unless exists $psets{$p}{merges};
        next unless ref    $psets{$p}{merges};
        my @merges = @{$psets{$p}{merges}};
        foreach my $merge (@merges) {
            if ($parents{$merge}) { 
                delete $parents{$merge};
            }
        }
    }
    @parents = keys %parents;
    @parents = map { " -p " . ptag($_) } @parents;
    return @parents;
}

sub git_rev_parse {
    my $name = shift;
    my $val  = `git-rev-parse $name`;
    die "Error: git-rev-parse $name" if $?;
    chomp $val;
    return $val;
}

# resolve a SHA1 to a known patchset
sub commitid2pset {
    my $commitid = shift;
    chomp $commitid;
    my $name = $rptags{$commitid} 
        || die "Cannot find reverse tag mapping for $commitid";
    # the keys in %rptag  are slightly munged; unmunge
    # reconvert the 3rd '--' sequence from the end
    # into a slash
    $name = reverse $name;
    $name =~ s!^(.+?--.+?--.+?--.+?)--(.+)$!$1/$2!;
    $name = reverse $name;
    my $ps   = $psets{$name} 
        || (print Dumper(sort keys %psets)) && die "Cannot find patchset for $name";
    return $ps;
}