#----------------------------------------------------------------------
#
# convert_tabcomplete.pl
#	Crude hack to help convert tab-complete's else-if chain to a switch.
#
# Lines looking like
#	else if (Matches("A", "B"))
# are converted to
#	case Matches("A", "B"):
# with insertion of a preceding "break;".
# The function name can be any one of Matches, HeadMatches, TailMatches,
# MatchesCS, HeadMatchesCS, or TailMatchesCS.
#
# There is a limited ability to deal with AND conditions
#	else if (Matches("A", "B") && othercondition)
# by converting that to
#	case Matches("A", "B"):
#		if (othercondition)
# Also, simple OR conditions such as
#	else if (Matches("A", "B") || Matches("C", "D"))
# are converted to adjacent case labels.
#
# Manual intervention is needed at the beginning and end of the switch
# construct, and for any else-ifs that the script fails to handle.
# There are a couple of places in the existing tab-complete.c file
# that have to be adjusted to prevent "can't decipher" complaints
# before the output is usable.
#
# If the input file is named something.c, the output file will be
# named something.out.c.
#----------------------------------------------------------------------

use strict;
use warnings FATAL => 'all';
use Getopt::Long;

my $output_path = '';

GetOptions('output:s' => \$output_path) || usage();

my $input_file = shift @ARGV || die "No input file.\n";

# Make sure output_path ends in a slash if needed.
if ($output_path ne '' && substr($output_path, -1) ne '/')
{
	$output_path .= '/';
}

$input_file =~ /([\w.-]+)\.c$/
  || die "Input file must be named something.c.\n";
my $base_filename = $1;
my $output_file = $output_path . $base_filename . '.out.c';

open(my $infd, '<', $input_file) || die "$input_file: $!\n";
open(my $outfd, '>', $output_file) || die "$output_file: $!\n";

# delayed_lines accumulates comments that we might want to move to
# after an inserted "break;".
my $delayed_lines = '';
# True if we're handling a multiline else-if condition
my $in_else_if = 0;
# The accumulated line
my $else_if_line;
my $else_if_lineno;
# True if we're expecting to suppress any braces appearing within case
my $suppress_braces = 0;

while (<$infd>)
{
	chomp;
	if ($in_else_if)
	{
		my $rest = $_;
		# collapse leading whitespace
		$rest =~ s/^\s+//;
		$else_if_line .= ' ' . $rest;
		# Double right paren is currently sufficient to detect completion
		if ($else_if_line =~ m/\)\)$/)
		{
			process_else_if($else_if_line, $else_if_lineno);
			$in_else_if = 0;
		}
	}
	elsif (m/^\telse if \(.*Matches(CS)?\(/)
	{
		$else_if_line = $_;
		$else_if_lineno = $.;
		# Double right paren is currently sufficient to detect completion
		if ($else_if_line =~ m/\)\)$/)
		{
			process_else_if($else_if_line, $else_if_lineno);
		}
		else
		{
			$in_else_if = 1;
		}
	}
	elsif ($suppress_braces == 1 and m/^\t\{$/)
	{
		# don't print
		$suppress_braces = 2;
	}
	elsif ($suppress_braces == 2 and m/^\t\}$/)
	{
		# don't print, but do flush delayed lines
		if ($delayed_lines ne '')
		{
			print $outfd $delayed_lines;
			$delayed_lines = '';
		}
		$suppress_braces = 0;
	}
	elsif (m/^$/
		|| m|^\s*/\*|
		|| m|^\s*\*/|
		|| m|^\s+\*|)
	{
		# delay output of blank and comment lines
		$delayed_lines .= $_ . "\n";
	}
	else
	{
		if ($delayed_lines ne '')
		{
			print $outfd $delayed_lines;
			$delayed_lines = '';
		}
		print $outfd "$_\n";
	}
}

close($infd);
close($outfd);


sub process_else_if
{
	my ($else_if_line, $else_if_lineno) = @_;

	# Strip the initial "else if (", which we know is there
	$else_if_line =~ s/^\telse if \(//;

	# Handle OR'd conditions
	my $isfirst = 1;
	while ($else_if_line =~
		s/^(Head|Tail|)Matches(CS|)\((("[^"]*"|MatchAnyExcept\("[^"]*"\)|[A-Za-z,\s])+)\)\s*\|\|\s*//
	  )
	{
		my $typ = $1;
		my $cs = $2;
		my $args = $3;
		process_match($typ, $cs, $args, $isfirst);
		$isfirst = 0;
	}

	# Check for AND'd condition
	if ($else_if_line =~
		s/^(Head|Tail|)Matches(CS|)\((("[^"]*"|MatchAnyExcept\("[^"]*"\)|[A-Za-z,\s])+)\)\s*&&\s*//
	  )
	{
		my $typ = $1;
		my $cs = $2;
		my $args = $3;
		process_match($typ, $cs, $args, $isfirst);
		$isfirst = 0;
		print $outfd "\t\tif ($else_if_line\n";
		$suppress_braces = 0;
	}
	elsif ($else_if_line =~
		s/^(Head|Tail|)Matches(CS|)\((("[^"]*"|MatchAnyExcept\("[^"]*"\)|[A-Za-z,\s])+)\)\)$//
	  )
	{
		my $typ = $1;
		my $cs = $2;
		my $args = $3;
		process_match($typ, $cs, $args, $isfirst);
		$isfirst = 0;
		$suppress_braces = 1;
	}
	else
	{
		warn
		  "could not process if condition at line $else_if_lineno: the rest looks like $else_if_line\n";
		if ($delayed_lines ne '')
		{
			print $outfd $delayed_lines;
			$delayed_lines = '';
		}
		print $outfd "\telse if ($else_if_line\n";
	}
}

sub process_match
{
	my ($typ, $cs, $args, $needbreak) = @_;

	print $outfd "\t\t\tbreak;\n" if $needbreak;
	if ($delayed_lines ne '')
	{
		print $outfd $delayed_lines;
		$delayed_lines = '';
	}
	print $outfd "\t\tcase ${typ}Matches${cs}(${args}):\n";
}

sub usage
{
	die <<EOM;
Usage: convert_tabcomplete.pl [--output/-o <path>] input_file
    --output        Output directory (default '.')

convert_tabcomplete.pl transforms tab-complete.c to tab-complete.out.c.
EOM
}