## make-metainfo.rb -- interactive .torrent creater
## Copyright 2005 William Morgan.
##
## This file is part of RubyTorrent. RubyTorrent is free software;
## you can redistribute it and/or modify it under the terms of version
## 2 of the GNU General Public License as published by the Free
## Software Foundation.
##
## RubyTorrent is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License (in the file COPYING) for more details.

require 'digest/sha1'
require "rubytorrent"

def die(x); $stderr << "#{x}\n" && exit(-1); end
def syntax
  %{
  Syntax: make-metainfo.rb [<file or directory>]+

  make-metainfo is an interactive program for creating .torrent files from a set
  of files or directories. any directories specified will be scanned recursively.
  }
end

def find_files(f)
  if FileTest.directory? f
    Dir.new(f).entries.map { |x| find_files(File.join(f, x)) unless x =~ /^\.[\.\/]*$/}.compact
  else
    f
  end
end

class Numeric
  def to_size_s
    if self < 1024
      "#{self.round}b"
    elsif self < 1024**2
      "#{(self / 1024.0).round}kb"
    elsif self < 1024**3
      "#{(self / (1024.0**2)).round}mb"
    else
      "#{(self / (1024.0**3)).round}gb"
    end
  end
end

def read_pieces(files, length)
  buf = ""
  files.each do |f|
    File.open(f) do |fh|
      begin
        read = fh.read(length - buf.length)
        if (buf.length + read.length) == length
          yield(buf + read)
          buf = ""
        else
          buf += read
        end
      end until fh.eof?
    end
  end

  yield buf
end 

die syntax if ARGV.length == 0

puts "Scanning..."
files = ARGV.map { |f| find_files f }.flatten
single = files.length == 1

puts "Building #{(single ? 'single' : 'multi')}-file .torrent for #{files.length} file#{(single ? '' : 's')}."

mi = RubyTorrent::MetaInfo.new
mii = RubyTorrent::MetaInfoInfo.new

maybe_name = if single
               ARGV[0]
             else
               (File.directory?(ARGV[0]) ? File.basename(ARGV[0]) : File.basename(File.dirname(ARGV[0])))
             end
puts
print %{Default output file/directory name (enter for "#{maybe_name}"): }
name = $stdin.gets.chomp
mii.name = (name == "" ? maybe_name : name)
puts %{We'll use "#{mii.name}".}

puts
puts "Measuring..."
length = nil
if single
  length = mii.length = files.inject(0) { |s, f| s + File.size(f) }
else
  mii.files = []
  length = files.inject(0) do |s, f|
    miif = RubyTorrent::MetaInfoInfoFile.new
    miif.length = File.size f
    miif.path = f.split File::SEPARATOR
    miif.path = miif.path[1, miif.path.length - 1] if miif.path[0] == mii.name
    mii.files << miif
    s + miif.length
  end
end

puts <<EOS

The file is #{length.to_size_s}. What piece size would you like? A smaller piece size
will result in a larger .torrent file; a larger piece size may cause
transfer inefficiency. Common sizes are 256, 512, and 1024kb.

Hint: for this .torrent,
EOS

size = nil
[64, 128, 256, 512, 1024, 2048, 4096].each do |size|
  num_pieces = (length.to_f / size / 1024.0).ceil
  tsize = num_pieces.to_f * 20.0 + 100
  puts "  - piece size of #{size}kb => #{num_pieces} pieces and .torrent size of approx. #{tsize.to_size_s}."
  break if tsize < 10240
end

maybe_plen = [size, 256].min
begin
  print "Piece size in kb (enter for #{maybe_plen}k): "
  plen = $stdin.gets.chomp
end while plen !~ /^\d*$/

plen = (plen == "" ? maybe_plen : plen.to_i)

mii.piece_length = plen * 1024
num_pieces = (length.to_f / mii.piece_length.to_f).ceil
puts "Using piece size of #{plen}kb => .torrent size of approx. #{(num_pieces * 20.0).to_size_s}."

print "Calculating #{num_pieces} piece SHA1s... " ; $stdout.flush

mii.pieces = ""
i = 0
read_pieces(files, mii.piece_length) do |piece|
  mii.pieces += Digest::SHA1.digest(piece)
  i += 1
  if (i % 100) == 0
    print "#{(i.to_f / num_pieces * 100.0).round}%... "; $stdout.flush
  end
end
puts "done"

mi.info = mii
puts <<EOS

Enter the tracker URL or URLs that will be hosting the .torrent
file. These are typically of the form:

  http://tracker.example.com:6969/announce

Multiple trackers may be partitioned into tiers; clients will try all
servers (in random order) from an earlier tier before trying those of
a later tier. See http://home.elp.rr.com/tur/multitracker-spec.txt
for details.

Enter the tracker URL(s) now. Separate multiple tracker URLs on the
same tier with spaces. Enter a blank line when you're done.

(Note that if you have multiple trackers, some clients may only use
the first one, so that should be the one capable of handling the most
traffic.)
EOS

tier = 0
trackers = []
begin
  print "Tier #{tier} tracker(s): "
  these = $stdin.gets.chomp.split(/\s+/)
  trackers.push these unless these.length == 0
  tier += 1 unless these.length == 0
end while (these.length != 0) || (tier == 0)

mi.announce = URI.parse(trackers[0][0])
mi.announce_list = trackers.map do |tier|
  tier.map { |x| URI.parse(x) }
end unless (trackers.length == 1) && (trackers[0].length == 1)

puts <<EOS

Enter any comments. No one will probably ever see these. End with a blank line.
EOS
comm = ""
while true
  s = $stdin.gets.chomp
  break if s == ""
  comm += s + "\n"
end
mi.comment = comm.chomp unless comm == ""

mi.created_by = "RubyTorrent make-metainfo (http://rubytorrent.rubyforge.org)"
mi.creation_date = Time.now

maybe_name = "#{mii.name}.torrent"
begin
  print "Output filename (enter for #{maybe_name}): "
  name = $stdin.gets.chomp
end while name.length == ""

name = (name == "" ? maybe_name : name)
File.open(name, "w") do |f|
  f.write mi.to_bencoding
end

puts "Succesfully created #{name}"