Parsing DBS transactions

parser.ex

defmodule Parser do
  @moduledoc """
  Sample parser for data from DBS. It is annoying that there isn't a csv from DBS bank
  
  Sample data:
  
  18 Mar 2019   GRAB *16236905-9-139   S$23.00
  18 Mar 2019   GRAB *2B3B63422351042EE  S$10.00
  18 Mar 2019   GRAB *1391705-9-138   S$15.00
  19 Mar 2019   2C2P - ZARA.COM SG  S$29.90 cr
  19 Mar 2019   2C2P - ZARA.COM SG  S$79.80
  21 Mar 2019   STARBUCKS COFFEE SINGA  S$50.00
  """
  @regex_figures ~r/(S\$)(\d{0,}\.\d{0,2})/

  @doc """
  Parses file
  """
  def parse() do
    File.read!("./sample")
    |> String.split("\n")
    |> Enum.map(&(&1 |> parse_line!))
  end

  def parse_line!(line) do
    case <<date::binary-size(11), rest::binary>> = line do
      line -> 
        {item, amount, type} = rest |> parse_rest
        %{
          date: date,
          item: item,
          amount: amount,
          type: type
        }
      _ -> 
        {:error}
    end
  end

  def parse_rest(line) do
    case Regex.split(@regex_figures, line, include_captures: :true, trim: true) do
      [line, figures] ->
        {line |> String.trim, figures, "debit"} 
      [line, figures, " cr"] ->
        {line |> String.trim, figures, "credit"} 
      _rest -> 
        {:error}
    end
  end

end