module GmailComposeEncoder

# File lib/gmail_compose_encoder.rb, line 5
def self.compose_draft_url(from_address, thread_id, message_id)
  tmp=encode("thread-f:#{thread_id.to_i(16)}+msg-a:#{message_id}")
  "https://mail.google.com/mail/u/#{from_address}/#all?compose=#{tmp}"
end

# File lib/gmail_compose_encoder/encoder.rb, line 11
def self.encode(url_parameter)
  transliterate(Base64.strict_encode64(url_parameter.gsub(THREAD_PREFIX,'')).gsub(/=/,''), FULL_ALPHABET, RESTRICTED_ALPHABET)
end

# File lib/gmail_compose_encoder/encoder.rb, line 15
def self.transliterate(string, input_alphabet=FULL_ALPHABET, output_alphabet=RESTRICTED_ALPHABET)
  string_indices = string.chars.reverse.map {|char| input_alphabet.index(char)}
  # string_indices.each {|xxx| puts "inputIndices #{xxx}"}
  result_indices = []
  string_indices.reverse.each_with_index do |string_index,iii|
    offset=0
    result_indices.each.with_index do |result_index,j|
      index = result_index * input_alphabet.size + offset
      if(index >=input_alphabet.size)
        remainder = index % output_alphabet.size
        offset = (index - remainder) / output_alphabet.size
        index=remainder
      else
        offset = 0
      end
      result_indices[j]=index
    end
    while(!offset.zero?)
      remainder = offset % output_alphabet.size
      result_indices.push(remainder)
      offset = (offset - remainder) / output_alphabet.size
    end
    jjj=0
    offset=string_index
    while(!offset.zero?)
      result_indices[jjj] = 0 if result_indices[jjj].nil?
      index = result_indices[jjj] + offset
      if(index >=output_alphabet.size)
        remainder = index % output_alphabet.size
        offset = (index - remainder) / output_alphabet.size
        result_indices[jjj]=remainder
      else
        offset=0
        result_indices[jjj]=index
      end
      jjj+=1
    end
  end

  result_indices.reverse.map {|idx| output_alphabet[idx]}.join
end