#!/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 $i = 0;
	my %seen;
	while (my $rev = shift @revqueue) {
		next if $seen{$rev}++;

		my %revinfo = git_commit_info($rev);

		foreach my $p (@{$revs{$rev}{'parents'}}) {

			git_diff_parse($p, $rev, %revinfo);
			push @revqueue, $p;
		}


		if (scalar @{$revs{$rev}{parents}} == 0) {
			# 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;
}


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

	my $diff = $repo->command_output_pipe('diff-tree', '-M', '-p',
			$rev, $parent, '--',
			$revs{$rev}{'filename'}, $revs{$parent}{'filename'});

	_git_diff_parse($diff, $parent, $rev, %revinfo);

	$repo->command_close_pipe($diff);
}

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

	my ($ri, $pi) = (0,0);
	my $slines = $revs{$rev}{'lines'};
	my @plines;

	my $gotheader = 0;
	my ($remstart);
	my ($hunk_start, $hunk_index);
	while(<$diff>) {
		chomp;
		if (m/^@@ -(\d+),(\d+) \+(\d+),(\d+)/) {
			$remstart = $1;
			# Adjust for 0-based arrays
			$remstart--;
			# Reinit hunk tracking.
			$hunk_start = $remstart;
			$hunk_index = 0;
			$gotheader = 1;

			for (my $i = $ri; $i < $remstart; $i++) {
				$plines[$pi++] = $slines->[$i];
				$ri++;
			}
			next;
		} elsif (!$gotheader) {
			next;
		}

		if (m/^\+(.*)$/) {
			my $line = $1;
			$plines[$pi++] = [ $line, '', '', '', 0 ];
			next;

		} elsif (m/^-(.*)$/) {
			my $line = $1;
			if (get_line($slines, $ri) eq $line) {
				# Found a match, claim
				claim_line($ri, $rev, $slines, %revinfo);
			} else {
				die sprintf("Sync error: %d/%d\n|%s\n|%s\n%s => %s\n",
						$ri, $hunk_start + $hunk_index,
						$line,
						get_line($slines, $ri),
						$rev, $parent);
			}
			$ri++;

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

		} else {
			if (substr($_,1) ne get_line($slines,$ri) ) {
				die sprintf("Line %d (%d) does not match:\n|%s\n|%s\n%s => %s\n",
						$hunk_start + $hunk_index, $ri,
						substr($_,1),
						get_line($slines,$ri),
						$rev, $parent);
			}
			$plines[$pi++] = $slines->[$ri++];
		}
		$hunk_index++;
	}
	for (my $i = $ri; $i < @{$slines} ; $i++) {
		push @plines, $slines->[$ri++];
	}

	$revs{$parent}{lines} = \@plines;
	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));
}