apollo18

defmodule Apollo18.CipherDecisor do

  @moduledoc """
  Utilitary module to help to choice best cipher parameter
  options to be used whit ```Apollo18``` cipher functionality modules.
  (This module functionalities are'nt in web/javascript version).
  """


  
  @doc """
  Receives a string to be ciphered and the max time in seconds desired
  to the resultant ciphered string should take in moment of decipher.
  Return the best estimated parameters to be used to decide cipher 
  configurations.
  
  If these returned parameters aren't good for you, you should
  manually inform other parameters to ```Apollo 18``` cipher
  functionalities as desired/needed.
  
  Keep in mind that's better slice a long text into 2,3 or more parts
  and cipher each part separately if you want be more performatic,
  or obtain more ```salt``` application on cipher without increase 
  exponentially the time to cipher/decipher.
  
  For very small strings (<= 200) the ```salt``` parameter vary from 5
  to 6. For small strings (<= 1000) the ```salt``` parameter vary from 3
  to 4. For all other cases the ```salt``` parameter vary from 1 to 3.
  
  ## Examples
  
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(400)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,1)
  %{base64: false, salt: 4} 
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(400)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,1)
  %{base64: false, salt: 4} 
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(400)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,1.3)
  %{base64: true, salt: 4} 
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(2000)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,2)
  %{base64: true, salt: 3} 
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(2000)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,1)
  %{base64: true, salt: 2} 
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(6000)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,12)
  %{base64: false, salt: 3} 
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(6000)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,20)
  %{base64: true, salt: 3}
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(20000)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,16)
  %{base64: false, salt: 2}
  ```
  ```elixir
  iex > string = Krug.SanitizerUtil.generate_random(20000)
  iex > Apollo18.CipherDecisor.get_best_parameters(string,20)
  %{base64: true, salt: 2} 
  ```
  """
  @doc since: "1.0.0"
  def get_best_parameters(string,max_decipher_time_execution_seconds \\ 1) do
    max_time = cond do
      (!(max_decipher_time_execution_seconds > 0)) -> 1
      true -> max_decipher_time_execution_seconds
    end
    length = string |> String.length()
    rate = length / max_time
    cond do
      (length <= 50 and rate <= 40) -> get_salt_and_base64(6,true)
      (length <= 50 and rate <= 50) -> get_salt_and_base64(6,false)
      (length <= 200 and rate <= 180) -> get_salt_and_base64(5,true)
      (length <= 200 and rate <= 200) -> get_salt_and_base64(5,false)
      (length <= 400 and rate <= 340) -> get_salt_and_base64(4,true)
      (length <= 400 and rate <= 400) -> get_salt_and_base64(4,false)
      (length <= 500 and rate <= 230) -> get_salt_and_base64(4,true)
      (length <= 500 and rate <= 300) -> get_salt_and_base64(4,false)
      (length <= 600 and rate <= 200) -> get_salt_and_base64(4,true)
      (length <= 600 and rate <= 260) -> get_salt_and_base64(4,false)
      (length <= 700 and rate <= 180) -> get_salt_and_base64(4,true)
      (length <= 700 and rate <= 230) -> get_salt_and_base64(4,false)
      (length <= 800 and rate <= 150) -> get_salt_and_base64(4,true)
      (length <= 800 and rate <= 190) -> get_salt_and_base64(4,false)
      (length <= 900 and rate <= 140) -> get_salt_and_base64(4,true)
      (length <= 900 and rate <= 180) -> get_salt_and_base64(4,false)
      (length <= 1000 and rate <= 125) -> get_salt_and_base64(4,true)
      (length <= 1000 and rate <= 150) -> get_salt_and_base64(4,false)
      (length <= 1000) -> get_salt_and_base64(3,true)
      (length <= 2000 and rate <= 1000) -> get_salt_and_base64(3,true)
      (length <= 2000 and rate <= 1300) -> get_salt_and_base64(3,false)
      (length <= 3000 and rate <= 750) -> get_salt_and_base64(3,true)
      (length <= 3000 and rate <= 1000) -> get_salt_and_base64(3,false)
      (length <= 6000 and rate <= 300) -> get_salt_and_base64(3,true)
      (length <= 6000 and rate <= 500) -> get_salt_and_base64(3,false)
      (length <= 6000) -> get_salt_and_base64(2,true)
      (length <= 10000 and rate <= 3300) -> get_salt_and_base64(2,true)
      (length <= 10000 and rate <= 5000) -> get_salt_and_base64(2,false)
      (length <= 20000 and rate <= 1000) -> get_salt_and_base64(2,true)
      (length <= 20000 and rate <= 1300) -> get_salt_and_base64(2,false)
      (length <= 20000) -> get_salt_and_base64(1,true)
      (length <= 35000 and rate <= 1400) -> get_salt_and_base64(1,true)
      true -> get_salt_and_base64(1,false)
    end
  end
  
  
  
  @doc false
  defp get_salt_and_base64(salt,base64) do
    %{
      salt: salt,
      base64: base64,
    }
  end



end