#!/usr/bin/perl

use File::Find;
use Getopt::Long;

my $basedir = ".";
GetOptions("basedir=s" => \$basedir)
        or die("Cannot parse command line arguments\n");

my $found_errors = 0;

sub report {
        my ($where, $what, $error) = @_;
        print "$where: $error: $what\n";
        $found_errors = 1;
}

sub grab_section {
        my ($page) = @_;
        open my $fh, "<", "$basedir/$page.txt";
        my $firstline = <$fh>;
        chomp $firstline;
        close $fh;
        my ($section) = ($firstline =~ /.*\((\d)\)$/);
        return $section;
}

sub lint {
        my ($file) = @_;
        open my $fh, "<", $file
                or return;
        while (<$fh>) {
                my $where = "$file:$.";
                while (s/linkgit:((.*?)\[(\d)\])//) {
                        my ($target, $page, $section) = ($1, $2, $3);

                        # De-AsciiDoc
                        $page =~ s/{litdd}/--/g;

                        if ($page !~ /^git/) {
                                report($where, $target, "nongit link");
                                next;
                        }
                        if (! -f "$basedir/$page.txt") {
                                report($where, $target, "no such source");
                                next;
                        }
                        $real_section = grab_section($page);
                        if ($real_section != $section) {
                                report($where, $target,
                                        "wrong section (should be $real_section)");
                                next;
                        }
                }
        }
        close $fh;
}

sub lint_it {
        lint($File::Find::name) if -f && /\.txt$/;
}

if (!@ARGV) {
        find({ wanted => \&lint_it, no_chdir => 1 }, $basedir);
} else {
        for (@ARGV) {
                lint($_);
        }
}

exit $found_errors;