From cfa5b4b9292080972da2f9743eb72b748e6a8564 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Thu, 3 Dec 2020 22:03:13 -0800
Subject: [PATCH] Day 4 Part 2

---
 2020/day4/day4.ex | 63 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 62 insertions(+), 1 deletion(-)

diff --git a/2020/day4/day4.ex b/2020/day4/day4.ex
index 0103866..02629ea 100644
--- a/2020/day4/day4.ex
+++ b/2020/day4/day4.ex
@@ -27,7 +27,7 @@ defmodule Day4 do
     # "cid"
   ]
 
-  defp valid?(passport) do
+  defp all_fields?(passport) do
     Enum.all?(@required_fields, fn field ->
       case Map.fetch(passport, field) do
         {:ok, _val} -> true
@@ -36,7 +36,67 @@ defmodule Day4 do
     end)
   end
 
+  defp parse_int(val, default) do
+    try do
+      String.to_integer(val)
+    rescue
+      ArgumentError -> default
+    end
+  end
+
+  defp valid?(passport) do
+    validators = %{
+      "byr" => fn val ->
+        int = parse_int(val, 0)
+        1920 <= int && int <= 2002
+      end,
+      "iyr" => fn val ->
+        int = parse_int(val, 0)
+        2010 <= int && int <= 2020
+      end,
+      "eyr" => fn val ->
+        int = parse_int(val, 0)
+        2020 <= int && int <= 2030
+      end,
+      "hgt" => fn val ->
+        case Regex.named_captures(~r/^(?<num>\d+)(?<units>cm|in)$/, val) do
+          %{"num" => num, "units" => units} ->
+            int = parse_int(num, 0)
+
+            case units do
+              "cm" ->
+                150 <= int && int <= 193
+
+              "in" ->
+                59 <= int && int <= 76
+            end
+
+          _ ->
+            false
+        end
+      end,
+      "hcl" => fn val -> Regex.match?(~r/^#[0-9a-f]{6}$/, val) end,
+      "ecl" => fn val -> Enum.member?(["amb", "blu", "brn", "gry", "grn", "hzl", "oth"], val) end,
+      "pid" => fn val -> Regex.match?(~r/^[0-9]{9}$/, val) end
+      # cid
+    }
+
+    Map.to_list(validators)
+    |> Enum.all?(fn {field, validator} ->
+      case Map.get(passport, field) do
+        nil -> false
+        val -> validator.(val)
+      end
+    end)
+  end
+
   def part1 do
+    read_input()
+    |> parse_passports()
+    |> Enum.count(&all_fields?/1)
+  end
+
+  def part2 do
     read_input()
     |> parse_passports()
     |> Enum.count(&valid?/1)
@@ -44,3 +104,4 @@ defmodule Day4 do
 end
 
 Day4.part1() |> IO.inspect()
+Day4.part2() |> IO.inspect()