#!/usr/bin/perl
# Copyright 2006, Ryan Anderson <ryan@michonline.com>
#
# GPL v2 (See COPYING)
#
# This file is licensed under the GPL v2, or a later version
# at the discretion of Linus Torvalds.

use warnings;
use strict;
use Getopt::Long;
use POSIX qw(strftime gmtime);
use File::Basename qw(basename dirname);
use Git;

sub usage() {
        print STDERR "Usage: ${\basename $0} [-s] [-S revs-file] file [ revision ]
        -l, --long
                        Show long rev (Defaults off)
        -t, --time
                        Show raw timestamp (Defaults off)
        -r, --rename
                        Follow renames (Defaults on).
        -S, --rev-file revs-file
                        Use revs from revs-file instead of calling git-rev-list
        -h, --help
                        This message.
";

        exit(1);
}

our ($help, $longrev, $rename, $rawtime, $starting_rev, $rev_file, $repo) = (0, 0, 1);

my $rc = GetOptions(    "long|l" => \$longrev,
                        "time|t" => \$rawtime,
                        "help|h" => \$help,
                        "rename|r" => \$rename,
                        "rev-file|S=s" => \$rev_file);
if (!$rc or $help or !@ARGV) {
        usage();
}

my $filename = shift @ARGV;
if (@ARGV) {
        $starting_rev = shift @ARGV;
}

my @stack = (
        {
                'rev' => defined $starting_rev ? $starting_rev : "HEAD",
                'filename' => $filename,
        },
);

$repo = Git->repository();

our @filelines = ();

if (defined $starting_rev) {
        @filelines = git_cat_file($starting_rev, $filename);
} else {
        open(F,"<",$filename)
                or die "Failed to open filename: $!";

        while(<F>) {
                chomp;
                push @filelines, $_;
        }
        close(F);

}

our %revs;
our @revqueue;
our $head;

my $revsprocessed = 0;
while (my $bound = pop @stack) {
        my @revisions = git_rev_list($bound->{'rev'}, $bound->{'filename'});
        foreach my $revinst (@revisions) {
                my ($rev, @parents) = @$revinst;
                $head ||= $rev;

                if (!defined($rev)) {
                        $rev = "";
                }
                $revs{$rev}{'filename'} = $bound->{'filename'};
                if (scalar @parents > 0) {
                        $revs{$rev}{'parents'} = \@parents;
                        next;
                }

                if (!$rename) {
                        next;
                }

                my $newbound = find_parent_renames($rev, $bound->{'filename'});
                if ( exists $newbound->{'filename'} && $newbound->{'filename'} ne $bound->{'filename'}) {
                        push @stack, $newbound;
                        $revs{$rev}{'parents'} = [$newbound->{'rev'}];
                }
        }
}
push @revqueue, $head;
init_claim( defined $starting_rev ? $head : 'dirty');
unless (defined $starting_rev) {
        my %ident;
        @ident{'author', 'author_email', 'author_date'} = $repo->ident('author');
        my $diff = $repo->command_output_pipe('diff', '-R', 'HEAD', '--', $filename);
        _git_diff_parse($diff, [$head], "dirty", %ident);
        $repo->command_close_pipe($diff);
}
handle_rev();


my $i = 0;
foreach my $l (@filelines) {
        my ($output, $rev, $committer, $date);
        if (ref $l eq 'ARRAY') {
                ($output, $rev, $committer, $date) = @$l;
                if (!$longrev && length($rev) > 8) {
                        $rev = substr($rev,0,8);
                }
        } else {
                $output = $l;
                ($rev, $committer, $date) = ('unknown', 'unknown', 'unknown');
        }

        printf("%s\t(%10s\t%10s\t%d)%s\n", $rev, $committer,
                format_date($date), ++$i, $output);
}

sub init_claim {
        my ($rev) = @_;
        for (my $i = 0; $i < @filelines; $i++) {
                $filelines[$i] = [ $filelines[$i], '', '', '', 1];
                        # line,
                        # rev,
                        # author,
                        # date,
                        # 1 <-- belongs to the original file.
        }
        $revs{$rev}{'lines'} = \@filelines;
}


sub handle_rev {
        my $revseen = 0;
        my %seen;
        while (my $rev = shift @revqueue) {
                next if $seen{$rev}++;

                my %revinfo = git_commit_info($rev);

                if (exists $revs{$rev}{parents} &&
                    scalar @{$revs{$rev}{parents}} != 0) {

                        git_diff_parse($revs{$rev}{'parents'}, $rev, %revinfo);
                        push @revqueue, @{$revs{$rev}{'parents'}};

                } else {
                        # We must be at the initial rev here, so claim everything that is left.
                        for (my $i = 0; $i < @{$revs{$rev}{lines}}; $i++) {
                                if (ref ${$revs{$rev}{lines}}[$i] eq '' || ${$revs{$rev}{lines}}[$i][1] eq '') {
                                        claim_line($i, $rev, $revs{$rev}{lines}, %revinfo);
                                }
                        }
                }
        }
}


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

        my $revlist;
        if ($rev_file) {
                open($revlist, '<' . $rev_file)
                    or die "Failed to open $rev_file : $!";
        } else {
                $revlist = $repo->command_output_pipe('rev-list', '--parents', '--remove-empty', $rev, '--', $file);
        }

        my @revs;
        while(my $line = <$revlist>) {
                chomp $line;
                my ($rev, @parents) = split /\s+/, $line;
                push @revs, [ $rev, @parents ];
        }
        $repo->command_close_pipe($revlist);

        printf("0 revs found for rev %s (%s)\n", $rev, $file) if (@revs == 0);
        return @revs;
}

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

        my $patch = $repo->command_output_pipe('diff-tree', '-M50', '-r', '--name-status', '-z', $rev);

        local $/ = "\0";
        my %bound;
        my $junk = <$patch>;
        while (my $change = <$patch>) {
                chomp $change;
                my $filename = <$patch>;
                if (!defined $filename) {
                        next;
                }
                chomp $filename;

                if ($change =~ m/^[AMD]$/ ) {
                        next;
                } elsif ($change =~ m/^R/ ) {
                        my $oldfilename = $filename;
                        $filename = <$patch>;
                        chomp $filename;
                        if ( $file eq $filename ) {
                                my $parent = git_find_parent($rev, $oldfilename);
                                @bound{'rev','filename'} = ($parent, $oldfilename);
                                last;
                        }
                }
        }
        $repo->command_close_pipe($patch);

        return \%bound;
}


sub git_find_parent {
        my ($rev, $filename) = @_;

        my $parentline = $repo->command_oneline('rev-list', '--remove-empty',
                        '--parents', '--max-count=1', $rev, '--', $filename);
        my ($revfound, $parent) = split m/\s+/, $parentline;

        return $parent;
}

sub git_find_all_parents {
        my ($rev) = @_;

        my $parentline = $repo->command_oneline("rev-list","--remove-empty", "--parents","--max-count=1","$rev");
        my ($origrev, @parents) = split m/\s+/, $parentline;

        return @parents;
}

sub git_merge_base {
        my ($rev1, $rev2) = @_;

        my $base = $repo->command_oneline("merge-base", $rev1, $rev2);
        return $base;
}

# Construct a set of pseudo parents that are in the same order,
# and the same quantity as the real parents,
# but whose SHA1s are as similar to the logical parents
# as possible.
sub get_pseudo_parents {
        my ($all, $fake) = @_;

        my @all = @$all;
        my @fake = @$fake;

        my @pseudo;

        my %fake = map {$_ => 1} @fake;
        my %seenfake;

        my $fakeidx = 0;
        foreach my $p (@all) {
                if (exists $fake{$p}) {
                        if ($fake[$fakeidx] ne $p) {
                                die sprintf("parent mismatch: %s != %s\nall:%s\nfake:%s\n",
                                            $fake[$fakeidx], $p,
                                            join(", ", @all),
                                            join(", ", @fake),
                                           );
                        }

                        push @pseudo, $p;
                        $fakeidx++;
                        $seenfake{$p}++;

                } else {
                        my $base = git_merge_base($fake[$fakeidx], $p);
                        if ($base ne $fake[$fakeidx]) {
                                die sprintf("Result of merge-base doesn't match fake: %s,%s != %s\n",
                                       $fake[$fakeidx], $p, $base);
                        }

                        # The details of how we parse the diffs
                        # mean that we cannot have a duplicate
                        # revision in the list, so if we've already
                        # seen the revision we would normally add, just use
                        # the actual revision.
                        if ($seenfake{$base}) {
                                push @pseudo, $p;
                        } else {
                                push @pseudo, $base;
                                $seenfake{$base}++;
                        }
                }
        }

        return @pseudo;
}


# Get a diff between the current revision and a parent.
# Record the commit information that results.
sub git_diff_parse {
        my ($parents, $rev, %revinfo) = @_;

        my @pseudo_parents;
        my @command = ("diff-tree");
        my $revision_spec;

        if (scalar @$parents == 1) {

                $revision_spec = join("..", $parents->[0], $rev);
                @pseudo_parents = @$parents;
        } else {
                my @all_parents = git_find_all_parents($rev);

                if (@all_parents !=  @$parents) {
                        @pseudo_parents = get_pseudo_parents(\@all_parents, $parents);
                } else {
                        @pseudo_parents = @$parents;
                }

                $revision_spec = $rev;
                push @command, "-c";
        }

        my @filenames = ( $revs{$rev}{'filename'} );

        foreach my $parent (@$parents) {
                push @filenames, $revs{$parent}{'filename'};
        }

        push @command, "-p", "-M", $revision_spec, "--", @filenames;


        my $diff = $repo->command_output_pipe(@command);

        _git_diff_parse($diff, \@pseudo_parents, $rev, %revinfo);

        $repo->command_close_pipe($diff);
}

sub _git_diff_parse {
        my ($diff, $parents, $rev, %revinfo) = @_;

        my $ri = 0;

        my $slines = $revs{$rev}{'lines'};
        my (%plines, %pi);

        my $gotheader = 0;
        my ($remstart);
        my $parent_count = @$parents;

        my $diff_header_regexp = "^@";
        $diff_header_regexp .= "@" x @$parents;
        $diff_header_regexp .= ' -\d+,\d+' x @$parents;
        $diff_header_regexp .= ' \+(\d+),\d+';
        $diff_header_regexp .= " " . ("@" x @$parents);

        my %claim_regexps;
        my $allparentplus = '^' . '\\+' x @$parents . '(.*)$';

        {
                my $i = 0;
                foreach my $parent (@$parents) {

                        $pi{$parent} = 0;
                        my $r = '^' . '.' x @$parents . '(.*)$';
                        my $p = $r;
                        substr($p,$i+1, 1) = '\\+';

                        my $m = $r;
                        substr($m,$i+1, 1) = '-';

                        $claim_regexps{$parent}{plus} = $p;
                        $claim_regexps{$parent}{minus} = $m;

                        $plines{$parent} = [];

                        $i++;
                }
        }

        DIFF:
        while(<$diff>) {
                chomp;
                #printf("%d:%s:\n", $gotheader, $_);
                if (m/$diff_header_regexp/) {
                        $remstart = $1 - 1;
                        # (0-based arrays)

                        $gotheader = 1;

                        foreach my $parent (@$parents) {
                                for (my $i = $ri; $i < $remstart; $i++) {
                                        $plines{$parent}[$pi{$parent}++] = $slines->[$i];
                                }
                        }
                        $ri = $remstart;

                        next DIFF;

                } elsif (!$gotheader) {
                        # Skip over the leadin.
                        next DIFF;
                }

                if (m/^\\/) {
                        ;
                        # Skip \No newline at end of file.
                        # But this can be internationalized, so only look
                        # for an initial \

                } else {
                        my %claims = ();
                        my $negclaim = 0;
                        my $allclaimed = 0;
                        my $line;

                        if (m/$allparentplus/) {
                                claim_line($ri, $rev, $slines, %revinfo);
                                $allclaimed = 1;

                        }

                        PARENT:
                        foreach my $parent (keys %claim_regexps) {
                                my $m = $claim_regexps{$parent}{minus};
                                my $p = $claim_regexps{$parent}{plus};

                                if (m/$m/) {
                                        $line = $1;
                                        $plines{$parent}[$pi{$parent}++] = [ $line, '', '', '', 0 ];
                                        $negclaim++;

                                } elsif (m/$p/) {
                                        $line = $1;
                                        if (get_line($slines, $ri) eq $line) {
                                                # Found a match, claim
                                                $claims{$parent}++;

                                        } else {
                                                die sprintf("Sync error: %d\n|%s\n|%s\n%s => %s\n",
                                                                $ri, $line,
                                                                get_line($slines, $ri),
                                                                $rev, $parent);
                                        }
                                }
                        }

                        if (%claims) {
                                foreach my $parent (@$parents) {
                                        next if $claims{$parent} || $allclaimed;
                                        $plines{$parent}[$pi{$parent}++] = $slines->[$ri];
                                            #[ $line, '', '', '', 0 ];
                                }
                                $ri++;

                        } elsif ($negclaim) {
                                next DIFF;

                        } else {
                                if (substr($_,scalar @$parents) ne get_line($slines,$ri) ) {
                                        foreach my $parent (@$parents) {
                                                printf("parent %s is on line %d\n", $parent, $pi{$parent});
                                        }

                                        my @context;
                                        for (my $i = -2; $i < 2; $i++) {
                                                push @context, get_line($slines, $ri + $i);
                                        }
                                        my $context = join("\n", @context);

                                        my $justline = substr($_, scalar @$parents);
                                        die sprintf("Line %d, does not match:\n|%s|\n|%s|\n%s\n",
                                                    $ri,
                                                    $justline,
                                                    $context);
                                }
                                foreach my $parent (@$parents) {
                                        $plines{$parent}[$pi{$parent}++] = $slines->[$ri];
                                }
                                $ri++;
                        }
                }
        }

        for (my $i = $ri; $i < @{$slines} ; $i++) {
                foreach my $parent (@$parents) {
                        push @{$plines{$parent}}, $slines->[$ri];
                }
                $ri++;
        }

        foreach my $parent (@$parents) {
                $revs{$parent}{lines} = $plines{$parent};
        }

        return;
}

sub get_line {
        my ($lines, $index) = @_;

        return ref $lines->[$index] ne '' ? $lines->[$index][0] : $lines->[$index];
}

sub git_cat_file {
        my ($rev, $filename) = @_;
        return () unless defined $rev && defined $filename;

        my $blob = git_ls_tree($rev, $filename);
        die "Failed to find a blob for $filename in rev $rev\n" if !defined $blob;

        my @lines = split(/\n/, $repo->get_object('blob', $blob));
        pop @lines unless $lines[$#lines]; # Trailing newline
        return @lines;
}

sub git_ls_tree {
        my ($rev, $filename) = @_;

        my $lstree = $repo->command_output_pipe('ls-tree', $rev, $filename);
        my ($mode, $type, $blob, $tfilename);
        while(<$lstree>) {
                chomp;
                ($mode, $type, $blob, $tfilename) = split(/\s+/, $_, 4);
                last if ($tfilename eq $filename);
        }
        $repo->command_close_pipe($lstree);

        return $blob if ($tfilename eq $filename);
        die "git-ls-tree failed to find blob for $filename";
}



sub claim_line {
        my ($floffset, $rev, $lines, %revinfo) = @_;
        my $oline = get_line($lines, $floffset);
        @{$lines->[$floffset]} = ( $oline, $rev,
                $revinfo{'author'}, $revinfo{'author_date'} );
        #printf("Claiming line %d with rev %s: '%s'\n",
        #               $floffset, $rev, $oline) if 1;
}

sub git_commit_info {
        my ($rev) = @_;
        my $commit = $repo->get_object('commit', $rev);

        my %info;
        while ($commit =~ /(.*?)\n/g) {
                my $line = $1;
                if ($line =~ s/^author //) {
                        @info{'author', 'author_email', 'author_date'} = $repo->ident($line);
                } elsif ($line =~ s/^committer//) {
                        @info{'committer', 'committer_email', 'committer_date'} = $repo->ident($line);
                }
        }

        return %info;
}

sub format_date {
        if ($rawtime) {
                return $_[0];
        }
        my ($timestamp, $timezone) = split(' ', $_[0]);
        my $minutes = abs($timezone);
        $minutes = int($minutes / 100) * 60 + ($minutes % 100);
        if ($timezone < 0) {
            $minutes = -$minutes;
        }
        my $t = $timestamp + $minutes * 60;
        return strftime("%Y-%m-%d %H:%M:%S " . $timezone, gmtime($t));
}