#!/usr/bin/perl -w

use warnings;
use strict;
use Fuse qw(:all);

my @files = (
    "/tmp/one",
    "/tmp/two",
    "/tmp/three",
    );

# get size of files
my %filesize = map { $_ => sizeof($_) } @files;

my $totalfilesize = 0;
map { $totalfilesize += $filesize{$_} } @files;

warn "Starting with total file size $totalfilesize; do not modify files while filesystem mounted!";

sub sizeof {
    my $file = shift;
    my ($size) = (`wc -c $file` =~ /(\d+)/);
    return $size;
}
my (%files) = (
        '.' => {
                type => 0040,
                mode => 0755,
                ctime => time()-1000
        },
        catenated => {
                cont => "This is file 'b'.\n",
                type => 0100,
                mode => 0644,
                ctime => time()-1000
        },
);

sub filename_fixup {
        my ($file) = shift;
        $file =~ s,^/,,;
        $file = '.' unless length($file);
        return $file;
}

sub e_getattr {
        my ($file) = filename_fixup(shift);
        $file =~ s,^/,,;
        $file = '.' unless length($file);
        return -ENOENT() unless exists($files{$file});
        my ($size) = exists($files{$file}{cont}) ? length($files{$file}{cont}) : 0;
	$size = $totalfilesize;
        my ($modes) = ($files{$file}{type}<<9) + $files{$file}{mode};
        my ($dev, $ino, $rdev, $blocks, $gid, $uid, $nlink, $blksize) = (0,0,0,1,0,0,1,1024);
        my ($atime, $ctime, $mtime);
        $atime = $ctime = $mtime = $files{$file}{ctime};
        # 2 possible types of return values:
        #return -ENOENT(); # or any other error you care to
        #print(join(",",($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks)),"\n");
        return ($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks);
}
sub e_getdir {
        # return as many text filenames as you like, followed by the retval.
        print((scalar keys %files)."\n");
        return (keys %files),0;
}

sub e_open {
        # VFS sanity check; it keeps all the necessary state, not much to do here.
        my ($file) = filename_fixup(shift);
        print("open called\n");
        return -ENOENT() unless exists($files{$file});
        return -EISDIR() if $files{$file}{type} & 0040;
        print("open ok\n");
        return 0;
}

sub e_read {
        # return an error numeric, or binary/text string.  (note: 0 means EOF, "0" will
        # give a byte (ascii "0") to the reading program)
        my ($file) = filename_fixup(shift);
        my ($buflen,$off) = @_;
        return -ENOENT() unless exists($files{$file});
        if(!exists($files{$file}{cont})) {
                return -EINVAL() if $off > 0;
                my $context = fuse_get_context();
                return sprintf("pid=0x%08x uid=0x%08x gid=0x%08x\n",@$context{'pid','uid','gid'});
        }
        return -EINVAL() if $off > $totalfilesize; #length($files{$file}{cont});
        return 0 if $off == $totalfilesize; #length($files{$file}{cont});
	my ($o, $i);
	$o = $off; $i = 0;
	while ($o > $filesize{$files[$i]}) {
	    $o -= $filesize{$files[$i]};
	    $i++;
	}
	my $read = 0;
	my $offset = $off;
	my $rtn;
	my $ret = "";
	# Read up to min($buflen,$totalfilesize-$off) bytes
	while ($read < $buflen && $read+$off < $totalfilesize && defined $files[$i]) {
	    open IN, "<$files[$i]" or return -EINVAL;
	    seek IN, $offset, 0;
	    my $r = read IN, $rtn, $buflen - $read;
	    $read += $r;
	    close IN;
	    $o -= $filesize{$files[$i]};
	    $i++;
	    $offset = 0; # one iteration per file, so next iteration reads from the start
	    $ret = $ret . $rtn;
	}
	return "$ret";
}

sub e_statfs { return 255, 1, 1, 1, 1, 2 }

Fuse::main(
    "mountpoint" => "$ENV{HOME}/temp",
    "getattr"=>"main::e_getattr",
    "getdir" =>"main::e_getdir",
    "open"   =>"main::e_open",
    "statfs" =>"main::e_statfs",
    "read"   =>"main::e_read",
    );