require "gdbm"
require "openssl"
require "optparse"

$digest = OpenSSL::Digest::SHA256.new

$opts = Array.new
$args = Hash.new
op = OptionParser.new { |opts|
  opts.banner = "Usage: #{__FILE__} [OPTIONS]"
  opts.on("--show-public", "Show public key") { |arg| $opts.push :pub }
  opts.on("--show-private", "Show private key") { |arg| $opts.push :priv }
  opts.on("--show-only", "Show only keys") { |arg| $opts.push :showonly }
  opts.on("-n", "--name NAME", "Name of the file that contains or should contain the signature and the data") { |arg| $args[:name] = arg }
  opts.on("-d", "--data DATA", "The data to be saved and signed.") { |arg| $args[:data] = arg }
  opts.on("-f", "--file FILE", "The file that contains the key") { |arg| $fn = arg }
  opts.on("-p", "--pack", "Pack data") { |arg| $opts.push :pack }
  opts.on("-u", "--unpack", "Unpack data") { |arg| $opts.push :unpack }
  opts.on("-s", "--key-strength STRENGTH", "Unpack data") { |arg| $args[:keystr] = arg }
  opts.on("-c", "--create", "Create key") { |arg| $opts.push :create }
  opts.on("-e", "--extract-public", "Save the public key in a separate file") { |arg| $opts.push :extract }
  opts.on("--extract-from-i2prm", "Extract private key from i2prm database") { |arg|  $opts.push :i2prm }
  
  opts.on("-h", "--help", "Prints this help") {
    puts "OpenSSL RSA key manager"
    puts "=======================\n\n"
    puts opts
    puts "Examples:"
    puts "   Create a new key: ruby #{__FILE__} --create --key-strength 512 -f key.rsa"
    puts "   Extract public key: ruby #{__FILE__} --extract-public -n pub.rsa -f key.rsa"
    puts "   Pack data: ruby #{__FILE__} --pack --name result --data \"Hello World!\" -f key.rsa"
    puts "   Unpack data: ruby #{__FILE__} --unpack --name result -f pub.rsa"
    puts "   Extract key from i2prm database: ruby #{__FILE__} --extract-from-i2prm -f key.rsa -n i2prm.gdbm"
    exit
  }
  
  
}
op.parse!

#pp $opts
#pp $args

def packdata name, data
  db = GDBM.new name
  db["data"] = data
  db["sign"] = $key.sign $digest, data
  db.close
end

def unpackdata name
  db = GDBM.new name
  puts "*#{db["data"]}*."
  puts "#{$key.verify($digest, db["sign"], db["data"]) ? "Valid" : "Invalid"} signature."
  db.close
end

def defaultoptions
  if $fn == nil
    puts "Require filename"
    exit
  end
  $key =  OpenSSL::PKey::RSA.new File.read $fn
  if $opts.include? :pub
    puts $key.public_key.to_s
  end
  if $opts.include? :priv
    puts $key.to_s
  end
end

if $opts.include? :create
  if $args[:keystr] == nil
    puts "Require key strength"
    exit
  elsif $args[:keystr].to_i < 512
    puts "key strength must be over 512 bytes"
    exit
  elsif $fn == nil
    puts "Require filename"
    exit
  end
  $key = OpenSSL::PKey::RSA.new $args[:keystr].to_i
  File.write $fn, $key.to_s
elsif $opts.include? :showonly
  defaultoptions
elsif $opts.include? :pack
  defaultoptions
  if $args[:name] == nil
    puts "Require target filename"
    exit
  elsif $args[:data] == nil
    puts "Require data"
    exit
  end
  packdata $args[:name], $args[:data]
elsif $opts.include? :unpack
  defaultoptions
  if $args[:name] == nil
    puts "Require target filename"
    exit
  end
  unpackdata $args[:name]
elsif $opts.include? :extract
  defaultoptions
  if $args[:name] == nil
    puts "Require target filename"
    exit
  end
  File.write $args[:name], $key.public_key.to_s
elsif $opts.include? :i2prm
  if $fn == nil
    puts "Require filename"
    exit
  end
  if $args[:name] == nil
    puts "Require target filename"
    exit
  end
  i2prm = GDBM.new $args[:name], 0555, GDBM::READER
  File.write $fn, i2prm["keypair-privkey"].chars.map { |c| c == "|" ? "\n" : c }.join
  i2prm.close
end