parse_prop(propstring, passport)

    case parse_prop(propstring, passport) do
      {:ok, pport} ->
        pport
      {:error, reason} ->
        IO.inspect(reason)
        passport
    end

    %{passport | birth_year: byr}

    {byr, _} = Integer.parse(byr)
    if !Enum.member?(1920..2002, byr) do
      {:error, "Birth Year outside valid range: #{byr}"}
    else
      {:ok, %{passport | birth_year: byr}}
    end

    %{passport | expiration_year: eyr}

    {eyr, _} = Integer.parse(eyr)
    if !Enum.member?(2020..2030, eyr) do
      {:error, "Expiration Year outside valid range: #{eyr}"}
    else
      {:ok, %{passport | expiration_year: eyr}}
    end

    %{passport | height: hgt}

    h =
      case hgt do
        <<a, b, c>> <> "cm" ->
          {n, _} = Integer.parse(<<a, b, c>>)
          if Enum.member?(150..193, n) do
            {:ok, {n, :cm}}
          else
            {:error, "Height outside valid range: #{n}cm"}
          end
        <<a, b>> <> "in" ->
          {n, _} = Integer.parse(<<a, b>>)
          if Enum.member?(59..76, n) do
            {:ok, {n, :inches}}
          else
            {:error, "Height outside valid range: #{n} inches"}
          end
        whatever ->
          {:error, "Height not right: #{whatever}"}
      end
    case h do
      {:ok, heit} -> {:ok, %{passport | height: heit}}
      {:error, reason} -> {:error, reason}
    end

    %{passport | passport_id: pid}

    if pid =~ ~r/^\d{9}$/ do
      {:ok, %{passport | passport_id: pid}}
    else
      {:error, "Invalid passport id: #{pid}"}
    end

    %{passport | eye_color: ecl}

    colors = ~w(amb blu brn gry grn hzl oth)
    if Enum.member?(colors, ecl) do
      {:ok, %{passport | eye_color: ecl}}
    else
      {:error, "Invalid eye color: #{ecl}"}
    end

    %{passport | hair_color: hcl}

    try do
      ["#", a, b, c, d, e, f] = String.graphemes(hcl)
      n =
        [a, b, c, d, e, f]
        |> Enum.map(&String.to_integer(&1, 16))
      n
      |> Enum.map(&Enum.member?(0x0..0xF, &1))
      |> Enum.all?(&Kernel.==(&1, true))
      |> case do
        true ->
          s = n |> Enum.map(&Integer.to_string(&1, 16)) |> Enum.join()
          {:ok, %{passport | hair_color: "##{s}"}}
      end
    rescue
      _ -> {:error, "Not valid hair color: #{hcl}"}
    end

    %{passport | issue_year: iyr}

    {iyr, _} = Integer.parse(iyr)
    if !Enum.member?(2010..2020, iyr) do
      {:error, "Issue Year outside valid range: #{iyr}"}
    else
      {:ok, %{passport | issue_year: iyr}}
    end

    %{passport | country_id: cid}

    {:ok, %{passport | country_id: cid}}

# tests
%{birth_year: 2002} = Passport.parse_input("byr:2002")
%{birth_year: nil} = Passport.parse_input("byr:2003")
%{height: {60, :inches}} = Passport.parse_input("hgt:60in")
%{height: {190, :cm}} = Passport.parse_input("hgt:190cm")
%{height: nil} = Passport.parse_input("hgt:190in")
%{height: nil} = Passport.parse_input("hgt:190")
%{hair_color: "#123ABC"} = Passport.parse_input("hcl:#123abc")
%{hair_color: nil} = Passport.parse_input("hcl:#123abz")
%{hair_color: nil} = Passport.parse_input("hcl:123abc")

%{eye_color: "brn"} = Passport.parse_input("ecl:brn")
%{eye_color: nil} = Passport.parse_input("ecl:wat")
%{passport_id: "000000001"} = Passport.parse_input("pid:000000001")
%{passport_id: nil} = Passport.parse_input("pid:0123456789")
IO.puts("Alles cool")

IO.inspect(outs)