#!/usr/bin/env perl
use strict;
use Config;
use File::Spec::Functions;

my %seen;

sub print_modules_real {
    my ($base, $dir, $word) = @_;

    # return immediatly if potential completion doesn't match current word
    # a double comparaison is used to avoid dealing with string lengths
    # (the shorter being the pattern to be used as the regexp)
    # word 'Fi', base 'File' -> match 'File' against 'Fi'
    # word 'File::Sp', base 'File' -> match 'File::Sp' againt 'File'
    return if
        $base               &&
        $word               &&
        $base !~ /^\Q$word/ &&
        $word !~ /^\Q$base/;

    chdir($dir) or return;

    # print each file
    foreach my $file (glob('*.pm')) {
        $file =~ s/\.pm$//;
        my $module = $base . $file;
        next if $module !~ /^\Q$word/;
        next if $seen{$module}++;
        print $module . "\n";
    }

    # recurse in each subdirectory
    foreach my $directory (grep { -d } glob('*')) {
        my $subdir = $dir . '/' . $directory;
        if ($directory =~ /^(?:[.\d]+|$Config{archname}|auto)$/) {
            # exclude subdirectory name from base
            print_modules_real(undef, $subdir, $word);
        } else {
            # add subdirectory name to base
            print_modules_real($base . $directory . '::', $subdir, $word);
        }
    }
}

sub print_modules {
    my ($word) = @_;

    foreach my $directory (@INC) {
        print_modules_real(undef, $directory, $word);
    }
}

sub print_functions {
    my ($word) = @_;

    my $perlfunc;
    for ( @INC, undef ) {
        return if not defined;
        $perlfunc = catfile $_, qw( pod perlfunc.pod );
        last if -r $perlfunc;
    }

    open my $fh, '<', $perlfunc or return;

    my $nest_level = -1;
    while ( <$fh> ) {
        next if 1 .. /^=head2 Alphabetical Listing of Perl Functions$/;
        ++$nest_level if /^=over/;
        --$nest_level if /^=back/;
        next if $nest_level;
        next unless /^=item (-?\w+)/;
        my $function = $1;
        next if $function !~ /^\Q$word/;
        next if $seen{$function}++;
        print $function . "\n";
    }

}

my $type = shift;
my $word = shift;

if ($type eq 'functions') {
    print_functions($word);
} elsif ($type eq 'modules') {
    print_modules($word);
}