KamilLelonek

# config.exs

config :my_app,
  http_adapter: HTTPoison

# test.exs

config :my_app,
  http_adapter: Http.Mock

KamilLelonek

defmodule Http.Behaviour do
  @typep url     :: binary()
  @typep body    :: {:form, [{atom(), any()}]}
  @typep headers :: [{atom, binary}] | [{binary, binary}] | %{binary => binary}
  @typep options :: Keyword.t()

  @callback post(url, body, headers, options) :: {:ok, map()} | {:error, binary() | map()}
end

KamilLelonek

def derive_key(%Private{chain_code: chain_code} = private_key, index)
     when normal?(index) do
  chain_code
  |> compressed_hmac_sha512(private_key, index)
  |> private_derivation(private_key)
end

def derive_key(%Private{key: key, chain_code: chain_code} = private_key, index)
     when hardened?(index) do
  chain_code

KamilLelonek

defmodule Pathlist do
  @mersenne_prime 2_147_483_647

  def to_list(<<"m/", path::binary>>), do: {:private, to_list(path)}
  def to_list(<<"M/", path::binary>>), do: {:public,  to_list(path)}

  def to_list(path) do
    path
    |> String.split("/")
    |> Enum.map(&cast_to_integer/1)

KamilLelonek

<<fingerprint::binary-4, _rest::binary>> =
  pub_key
  |> compress()
  |> hash_160()

KamilLelonek

@mersenne_prime 2_147_483_647

defguardp hardened?(index) when index >  @mersenne_prime
defguardp normal?(index)   when index <= @mersenne_prime and index > -1

KamilLelonek

defmodule Task2 do
  @doc """
  Problem:
  We would like to check what users are actively using one of our web applications and, if so, ask for their opinion.

  Each user enters the application and navigates between pages.
  For each user, we log whenever he or she opens main page or any other page.
  Whenever he or she open a page for the first time or after a break of at least 30 minutes,
  we count it as a new session. We will ask the user for his or her opinion
  only when for the last three days he or she used the application each day

KamilLelonek

defmodule Task1 do
  @doc """
  A function that receives two sequences: A and B of integers and returns one sequence C.
  Sequence C should contain all elements from sequence A (maintaining the order) except those,
  that are present in sequence B p times, where p is a prime number.

  Example:
  A=[2,3,9,2,5,1,3,7,10]
  B=[2,1,3,4,3,10,6,6,1,7,10,10,10]
  C=[2,9,2,5,7,10]

KamilLelonek

def compress(<<0x04::8, x_coordinate::256, y_coordinate::256>>) do
  y_coordinate
  |> rem(2)
  |> compress(x_coordinate)
end

def compress(0, x_coordinate), do: <<0x02::8, x_coordinate::256>>
def compress(1, x_coordinate), do: <<0x03::8, x_coordinate::256>>

KamilLelonek

<<
  version_number::binary,
  0::8,  # depth
  0::32, # fingerprint
  0::32, # key index
  chain_code::binary,
  key::binary
>>