#!/usr/bin/perl

use strict;
use warnings;

sub OutputOf($@)
{
	my ($cmd, @args) = @_;
	$cmd =~ s/#(\d)/"\$ARG$1"/g;
	$ENV{"ARG$_"} = $args[$_-1]
		for 1..@args;

	open my $fh, '-|', $cmd
		or die "popen $cmd: $!";

	$ENV{"ARG$_"} = ''
		for 1..@args;

	undef local $/;
	my $ret = <$fh>;
	close $fh;

	return $ret;
}

my %conf = 
(
	master => '',
	revisions_applied => ''
);
my @revisions_applied = (); # array of [first, last] ranges

sub LoadSettings()
{
	open my $fh, '<', ".patchsets"
		or return;
	while(<$fh>)
	{
		chomp;
		/^([^=]*?)\s*=\s*(.*?)$/s
			or next;
		die "Invalid config item: $1 (allowed: @{[sort keys %conf]})"
			if not exists $conf{$1};
		$conf{$1} = $2;
	}

	@revisions_applied = map { /^(\d+)-(\d+)$/s or die "Invalid revision spec $_"; [$1, $2]; } split /,/, $conf{revisions_applied};
}

sub WriteSettings()
{
	$conf{revisions_applied} = join ',', map { "$_->[0]-$_->[1]" } @revisions_applied;

	open my $fh, '>', ".patchsets"
		or die "writing settings: $!";
	for(sort keys %conf)
	{
		print $fh "$_ = $conf{$_}\n";
	}
}

sub AddPatch($$)
{
	my ($first, $last) = @_;
	die "Invalid range" if $first > $last;

	my @rev = sort { $a->[0] <=> $b->[0] } (@revisions_applied, [$first, $last]);

	my $i = 0;
	while($i < @rev - 1)
	{
		my $a = $rev[$i][0];
		my $b = $rev[$i][1];
		my $c = $rev[$i+1][0];
		my $d = $rev[$i+1][1];

		if($b >= $c)
		{
			die "overlapping patch: $a-$b overlaps $c-$d";
		}
		if($b == $c - 1)
		{
			splice @rev, $i, 2, [$a, $d];
			next;
		}
		++$i;
	}

	@revisions_applied = @rev;
}

sub RemovePatch($$)
{
	my ($first, $last) = @_;
	die "Invalid range" if $first > $last;

	my @rev = sort { $a->[0] <=> $b->[0] } (@revisions_applied);

	my $i = 0;
	while($i < @rev)
	{
		my $a = $rev[$i][0];
		my $b = $rev[$i][1];

		if($first >= $a && $last <= $b)
		{
			# this is the range
			my @replacement;

			if($first == $a && $last == $b)
			{
				@replacement = ();
			}
			elsif($first == $a)
			{
				@replacement = ([$last + 1, $b]);
			}
			elsif($last == $b)
			{
				@replacement = ([$a, $first - 1]);
			}
			else
			{
				@replacement = ([$a, $first - 1], [$last + 1, $b]);
			}
			splice @rev, $i, 1, @replacement;
			@revisions_applied = @rev;
			return;
		}
	}

	die "could not remove range: not in set";
}

sub GetUnappliedRanges($)
{
	my ($lastrev) = @_;
	my @unapplied = ();

	my $cur = 0;
	for(@revisions_applied)
	{
		my ($a, $b) = @$_;
		if($a - 1 >= $cur + 1)
		{
			push @unapplied, [$cur + 1, $a - 1];
		}
		$cur = $b;
	}
	if($lastrev >= $cur + 1)
	{
		push @unapplied, [$cur + 1, $lastrev];
	}
	return @unapplied;
}

sub GetMasterRev()
{
	my $svninfo = OutputOf 'svn info #1', $conf{master};
	$svninfo =~ /^Last Changed Rev: (\d+)$/m
		or die "could not get svn info";
	return $1;
}

sub GetLog($$)
{
	my ($first, $last) = @_;
	my $log = OutputOf 'svn log -r#1:#2 #3', $first, $last, $conf{master};
	$log =~ s/^-*$//gm;
	$log =~ s/\n+/\n/gs;
	$log =~ s/^\n//s;
	$log =~ s/\n$//s;
	return $log;
}

sub GetDiff($$)
{
	my ($first, $last) = @_;
	return OutputOf 'svn diff -r#1:#2 #3', $first-1, $last, $conf{master};
}

my ($cmd, @args) = @ARGV;
$cmd = 'help' if not defined $cmd;

if($cmd eq 'info')
{
	LoadSettings();
	for(@revisions_applied)
	{
		my ($a, $b) = @$_;
		print "Applied: $a to $b\n";
	}
	for(GetUnappliedRanges(GetMasterRev()))
	{
		my ($a, $b) = @$_;
		print "Unapplied: $a to $b\n";
	}
}
elsif($cmd eq 'unmerged-diff')
{
	LoadSettings();
	my @autoadd = ();
	for(GetUnappliedRanges(GetMasterRev()))
	{
		my ($a, $b) = @$_;
		my $log = GetLog $a, $b;
		if($log eq '')
		{
			push @autoadd, [$a, $b];
			next;
		}
		$log =~ s/^/  /gm;
		print "Unapplied: $a to $b\n";
		print "$log\n";
		print GetDiff $a, $b;
		print "\n";
	}
	for(@autoadd)
	{
		my ($a, $b) = @$_;
		print "Autofilled revision hole $a to $b\n";
		AddPatch $a, $b;
	}
	WriteSettings() if @autoadd;
}
elsif($cmd eq 'unmerged')
{
	LoadSettings();
	my @autoadd = ();
	for(GetUnappliedRanges(GetMasterRev()))
	{
		my ($a, $b) = @$_;
		my $log = GetLog $a, $b;
		if($log eq '')
		{
			push @autoadd, [$a, $b];
			next;
		}
		$log =~ s/^/  /gm;
		print "Unapplied: $a to $b\n";
		print "$log\n\n";
	}
	for(@autoadd)
	{
		my ($a, $b) = @$_;
		print "Autofilled revision hole $a to $b\n";
		AddPatch $a, $b;
	}
	WriteSettings() if @autoadd;
}
elsif($cmd eq 'merge')
{
	my ($first, $last, $force) = @args;
	die "Usage: $0 merge first last [--force]"
		if not defined $first;
	$last = $first if not defined $last;

	die "Usage: $0 merge first last"
		if "$first$last" =~ /[^0-9]/;

	die "There is an uncommitted merge"
		if -f '.commitmsg' and $force ne '--force';

	LoadSettings();
	AddPatch $first, $last;

	print OutputOf 'svn merge -r#1:#2 #3', ($first - 1), $last, $conf{master};
	print "You may also want to run $0 unmerged to fill possible revision holes\n";
	print "Make sure there are no conflicts, then run $0 commit\n";
	print "To abort, use $0 revert\n";
	
	open my $fh, '>>', '.commitmsg'
		or die "open .commitmsg";
	print $fh GetLog $first, $last;
	print $fh "\n";
	close $fh;

	WriteSettings();
}
elsif($cmd eq 'undo')
{
	my ($first, $last, $force) = @args;
	die "Usage: $0 undo first last"
		if not defined $first;
	$last = $first if not defined $last;

	die "Usage: $0 merge first last"
		if "$first$last" =~ /[^0-9]/;

	die "There is an uncommitted merge"
		if -f '.commitmsg' and $force ne '--force';

	LoadSettings();
	RemovePatch $first, $last;

	print OutputOf 'svn merge -r#2:#1 #3', ($first - 1), $last, $conf{master};
	print "Make sure there are no conflicts, then run $0 commit\n";
	print "To abort, use $0 revert\n";

	open my $fh, '>>', '.commitmsg'
		or die "open .commitmsg";
	print $fh "undo the following merge:\n", GetLog $first, $last;
	close $fh;

	WriteSettings();
}
elsif($cmd eq 'commit')
{
	system 'vim .commitmsg';
	print "Hit Enter if OK to commit, Ctrl-C otherwise...\n";
	my $ok = <STDIN>;
	if(!system 'svn commit -F .commitmsg')
	{
		unlink '.commitmsg';
	}
}
elsif($cmd eq 'revert')
{
	if(!system 'svn revert -R .')
	{
		unlink '.commitmsg';
	}
}
elsif($cmd eq 'init')
{
	my ($master, $rev) = @args;
	$conf{master} = $master;
	@revisions_applied = [1, $rev];
	WriteSettings();
}
else
{
	print <<EOF;
Usage:
  $0 init masterrepo rev
  $0 info
  $0 unmerged
  $0 unmerged-diff
  $0 merge rev1 [rev2] [--force]
  $0 undo rev1 [rev2] [--force]
  $0 commit
  $0 revert
EOF
}