#!/usr/bin/perl -w

use strict;

use POSIX;
use IPC::Open2;

$!=0; $?=0;
my $refs=`git-for-each-ref`;
die "$? $!" if $?;

chomp $refs;

my $gcfpid = open2 \*GCFO, \*GCFI, 'git cat-file --batch' or die $!;

sub getobj ($$) {
    my ($obj, $type) = @_;
    print GCFI $obj, "\n" or die $!;
    my $x = <GCFO>;
    $x =~ m/^\w+ (\w+) (\d+)\n/ or die "$obj ?";
    my ($gtype, $gsize) = ($1,$2,$3);
    $gtype eq $type or die "$obj $gtype != $type ?";
    my $gdata;
    read GFCO, $gdata, $gsize == $gsize or die "$obj $!";
    $x = <GFCO>;
    $x eq "\n" or die "$obj $!";
    return $gdata;
}

our %memo;
our %count;

sub rewrite_commit ($) {
    my ($obj) = @_;
    my $m = \ $memo{$obj};
    return $$m if defined $$m;
    my $olddata = getobj $obj, 'commit';
    die "$obj ?" unless $old;
    $olddata =~ m/(?<=\n)(?=\n)/ or die "$obj ?";
    my $msg = $';
    $_ = $`;
    s{^(parent )(\w+)$}{ $1 . rewrite_commit($2) }gme;
    $count{fix_overwrite} += s{^commiter }{committer }gm;
    if (!m{^author }m && !m{^committer }m) {
	m{^parent (\w+)}m or die "$obj ?";
	my $parent = getobj $1, 'commit';
	$parent =~ m/^(?:.+\n)+(author .*\ncommitter .*\n)/;
	m/\n$/ or die "$obj ?";
	$_ .= $1;
	$count{fix_import}++;
    }
    $newdata = $_.$msg;
    my $newobj;
    if ($newdata eq $olddata) {
	$newobj = $oldobj;
    } else {
	my $gwopid = open2 \*GWO, \*GWI,
	    'git hash-object -t comit --stdin'
	    or die $!;
	print GWI $newdata or die $!;
	close GWI or die $!;
	$_ = <GWO>;
	close GWO or die $!;
	waitpid $gwopid,0 == $gwopid or die $!;
	die $? if $?;
	m/^(\w+)\n/ or die "$_ ?";
	$newobj = $1;
	$count{commits}++;
    }
    $$m= $newobj;
    return $newobj;
}

sub rewrite_tag ($) {
    my ($obj) = @_;
    $_ = getobj $obj, 'tag';
    m/^type (\w+)\n/m or die "$obj ?";
    if ($1 ne 'commit') {
	$count{"oddtags $1"}++;
	return;
    }
    m/^object (\w+)\n/m or die "$obj ?";
    my $oldref = $1;
    my $newref = rewrite_commit $oldref;
    if ($oldref eq $newref) {
	return $obj;
    }
    s/^(?<=object )\w+(?=\n)/$newref/m or die "$obj ?";
    
}

foreach my $rline (split /\n/, $refs) {
    die "$_ ?" unless m/^(\w+)\s+(\w+)\s+(\S.*)/;
    my ($obj, $type, $refname) = @_;
    my $rewrite;
    if ($type eq 'commit') {
	$rewrite = rewrite_commit($obj);
    } elsif ($type eq 'tag') {
	my $rewrite = rewrite_tag($obj);
    } else {
	warn "ref $refname refers to $type\n";
	next;
    }
    next if $refname eq $rewrite;
    push @updates, [ $refname, $rewrite ];
}



if git-symbolic-ref HEAD >/dev/null 2>&1; then
    refs+=' HEAD'



my $gfo = `LC_MESSAGES=C git fsck --no-dangling 2>&1`;
$? == 256 or die "$? $!"




 m/^error in commit (\w+):.*invalid format - expected 'committer/;

case `wc -l <$tmp/bad` in
    0)
	echo >&2 'nothing bad found - is git-fsck doing as we expect?' ;
	exit 8 ;;
    1)
	read <$tmp/bad bads
	nots="^$bads^0 ^$bads^1"
	;;
    *)
	bads="cat $tmp/bad"
	;;
esac

args="$nots"

refs=`git-for-each-ref --format='%(refname)'`

if git-symbolic-ref HEAD >/dev/null 2>&1; then
    refs+=' HEAD'
fi

for head in $refs; do
    exec <$tmp/bad
    needed=false
    for bad in $bads; do
	if git merge-base --is-ancestor $bad $head; then
	    needed=true
	    break
	fi
    done 
    if ! $needed; then continue; fi
    args+=" $head"
done

git filter-branch --original dgit-badcommit --commit-filter '
echo >&2 "FOO $*"
cat >&2
echo >&2 ====
false
    sed -e '\''1,/^$/ s/^commiter /committer /'\''
' $args