🎄 Year 2020 🔔 Day 04

Parse input

filename = "#{__DIR__}/../../../inputs/2020/day04.txt"

parsed_input_stream =
  File.stream!(filename)
  |> Stream.map(&String.trim(&1))
  |> Stream.map(&String.split(&1))
  |> Stream.chunk_by(fn e -> e == [] end)
  |> Stream.take_every(2)
  |> Stream.map(&Enum.flat_map(&1, fn e -> e end))
  |> Stream.map(
    &Enum.map(&1, fn field -> String.split(field, ":") |> then(fn [k, v] -> {k, v} end) end)
  )
  |> Stream.map(&Map.new/1)

Shared code

Part One

mandatory_keys = ["byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"]

parsed_input_stream
|> Enum.filter(fn passport ->
  Enum.all?(mandatory_keys, fn key -> Map.has_key?(passport, key) end)
end)
|> Enum.count()

Part two

mandatory_keys = ["byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"]

year_in_between = fn year, from, to ->
  String.match?(year, ~r/\d{4}/) && String.to_integer(year) >= from &&
    String.to_integer(year) <= to
end

parsed_input_stream
|> Stream.filter(fn passport ->
  Enum.all?(mandatory_keys, fn key -> Map.has_key?(passport, key) end)
end)
|> Stream.filter(fn %{"byr" => byr, "iyr" => iyr, "eyr" => eyr} ->
  year_in_between.(byr, 1920, 2002) &&
    year_in_between.(iyr, 2010, 2020) &&
    year_in_between.(eyr, 2020, 2030)
end)
|> Stream.filter(fn %{"hgt" => hgt} ->
  case hgt do
    <<cm::bitstring-size(24)>> <> "cm" ->
      String.to_integer(cm) >= 150 && String.to_integer(cm) <= 193

    <<inches::bitstring-size(16)>> <> "in" ->
      String.to_integer(inches) >= 59 && String.to_integer(inches) <= 76

    _ ->
      false
  end
end)
|> Stream.filter(fn %{"hcl" => hcl} ->
  String.match?(hcl, ~r/#[0-9a-f]{6}/)
end)
|> Stream.filter(fn %{"ecl" => ecl} ->
  Enum.member?(["amb", "blu", "brn", "gry", "grn", "hzl", "oth"], ecl)
end)
|> Stream.filter(fn %{"pid" => pid} ->
  String.match?(pid, ~r/[0-9]{9}/)
end)
|> Enum.count()