#!/usr/bin/perl

# Generate Git history.
#
# Copyright 2016 Robert Krawitz (rlk@alum.mit.edu)
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 2 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

use Getopt::Long;

use strict;

my ($base_file);
my ($base_revision);

GetOptions("i=s" => \$base_file,
	   "r=s" => \$base_revision);

my ($autline) = "";
my ($curmsg) = "";
my ($curtag) = "";
my (%addlines);
my (%removelines);
my (%filechanges);
my (%files);

my ($state) = 0;
my ($ostate) = 0;
my ($firsttime) = 1;

sub print_it {
    if ($curtag ne "") {
	print "===============================================================================\n";
	print "Name: $curtag\n\n"
    }
    print "$autline\n";
    my (@files) = sort keys %files;
    if ($#files >= 0) {
	my ($add) = 0;
	my ($remove) = 0;
	map { $add += $addlines{$_} } @files;
	map { $remove += $removelines{$_} } @files;
	print "	Lines: +$add, -$remove\n";
	print "	Files:";
	my ($fcount) = 0;
	foreach my $fn (@files) {
	    if ($fcount++ == 0) {
		print "	$fn (";
	    } else {
		print "		$fn (";
	    }
	    if ($filechanges{$fn} eq 'D') {
		print "removed -$removelines{$fn}";
	    } elsif ($filechanges{$fn} eq 'C') {
		    print "added +$addlines{$fn}";
	    } else {
		print "+$addlines{$fn}, -$removelines{$fn}";
	    }
	    print ")\n";
	}
	print "\n";
    }
    print "$curmsg\n";
    $autline = "";
    $curmsg = "";
    $curtag = "";
    %addlines = ();
    %removelines = ();
    %filechanges = ();
    %files = ();
}

if ($base_revision) {
    $base_revision = "'$base_revision..HEAD'";
}

open(GITLOG, "git log --diff-algorithm=default --summary --numstat --date=short --pretty=format:'>>>GIT1%n%cd  <%an>	%H%n>>>GIT2%n%B>>>GIT3%n%D%n>>>GIT4' $base_revision|") or die "Can't run git log: $!\n";

while (<GITLOG>) {
    if (/>>>GIT([0-9]+)$/) {
	$state = $1;
	if ($state == 1) {
	    if (! $firsttime) {
		print_it();
	    }
	    $firsttime = 0;
	}
    } elsif ($state == 1) {
	$autline = $_;
    } elsif ($state == 2) {
	if ($_ ne "\n") {
	    $curmsg .= "	";
	}
	$curmsg .= $_;
    } elsif ($state == 3) {
	if (/^tag: ((guten|gimp-)?print-[0-9]+_.*)/) {
	    $curtag = $1;
	}
    } elsif ($state == 4) {
	if ($_ ne "\n") {
	    chomp;
	    $_ =~ s/^[ 	]+//;
	    if (/^delete/) {
		my ($junk, $junk, $junk, $fn) = split(/ /, $_, 4);
		$filechanges{$fn} = 'D';
	    } elsif (/^create/) {
		my ($junk, $junk, $junk, $fn) = split(/ /, $_, 4);
		$filechanges{$fn} = 'C';
	    } elsif (/^[-0-9]/) {
		my ($add, $remove, $fn) = split(/	/, $_, 3);
		$add = 0 if ($add eq '-');
		$remove = 0 if ($remove eq '-');
		$files{$fn} = 1;
		$addlines{$fn} = $add;
		$removelines{$fn} = $remove;
	    }
	}
    } else {
	die "Unknown state $state\n";
    }
}

print_it();

if ($base_file) {
    open IN, $base_file or die "Can't open baseline file $base_file: $!";
    while (<IN>) {
	print;
    }
}

exit 0;