#!/usr/bin/perl -w
use Getopt::Std;
use strict;

our ($opt_A, $opt_n);
getopts('nA');
my $dry_run = $opt_n;
my $add_braces = !$opt_A;
my $any_bad = 0;

my @files = @ARGV;
undef $/;
unless (@files)
{
    @files = (grep /\.(cc|h)$/ && !/(^|\/)prebuilt\//, split /\n/, `git ls-files`);
}

sub rebrace($$$)
{
    my ($condition, $indent, $body) = @_;
    my $orig = "$condition$body";

    # Don't add braces if it's only two lines.
    return $orig unless $orig =~ /\n.*\n.*\n/;

    # Don't add braces if the "body" consists of only comments.
    return $orig unless $body =~ m&^\s++(?!//)&s;

    return "$condition$indent\{\n$body$indent\}\n";
}

for my $f (@files)
{
    open F, "<", $f or die "Can't read $f\n";
    my $old = $_ = <F>;
    close F;

    # Eliminate braces around one-line blocks.
    s&^( +(?:if|while|for|do|else)\b[^\n]*)\n +{\n( *[^/ }][^\n]*)\n +}$&$1\n$2&msg;

    # Add braces in blocks that need them.
    s/# $1 = the keyword and condition
      (
        # $2 = first-line indent
        ^(\s+)   (?:if|while|for|do|else)\b \s*
                 # $3 = nested parenthesised expression, possibly multi-line
                 (
                   \(
                      (?: [^()]* (?3))*
                      [^()]*
                   \)
                 ) \s*\n
      )
      # $4 = the body
      (
        # Higher indent than the keyword.
        \2 \s++
        # Not another flow control statement or braces
        (?! { | (?:if|while|for|do|else)\b) [^\n]*\n
        # And possibly more lines of higher indent than the keyword
        (?: \2 \s+ [^\n]* \n)*
      )
    /rebrace($1,$2,$4)/egsmx if $add_braces;

    # return is not a function, eliminate totally enclosing parentheses.
    # This part handles parenthese-less payloads.
    while (/^( *)return \(([^()]+)\);/sm)
    {
        # Done this roundabout way to properly unindent multiline blocks.
        my $prev = "$`$1return ";
        my $next = ";$'";
        my $cur = $2;
        $cur =~ s/\n /\n/sg;
        $_ = "$prev$cur$next";
    }

    # return (x) where x contains parentheses.
    # Looks like no one told Larry Wall properties of regular expression,
    # including the part where they can't do arbitrarily nested parentheses.
    while (/^(\s*)return\s+
            \((
             (?: [^()]*+
                 (\( (?: [^()]++ | (?3) )* \))
             )+
             [^()]*+
            )\);/sxm)
    {
        my $prev = "$`$1return ";
        my $next = ";$'";
        my $cur = "$2";
        $cur =~ s/\n /\n/sg;
        $_ = "$prev$cur$next";
    }

    if ($old ne $_)
    {
        print "$f\n";
        $any_bad = 1;
        if (!$dry_run)
        {
            open F, ">", $f or die "Can't write $f\n";
            print F;
            close F;
        }
    }
}

exit 1 if ($dry_run and $any_bad);