From 11975a6e5d2918ba62a391ec4baad41676e463b7 Mon Sep 17 00:00:00 2001
From: Justin Wernick <justin@worthe-it.co.za>
Date: Wed, 25 Sep 2024 10:46:32 +0200
Subject: Day 12

---
 2015/day12.exs | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 2015/day12.exs

(limited to '2015')

diff --git a/2015/day12.exs b/2015/day12.exs
new file mode 100644
index 0000000..df77e94
--- /dev/null
+++ b/2015/day12.exs
@@ -0,0 +1,103 @@
+jsonString = String.trim(File.read!("inputs/day12.txt"))
+
+numberSum =
+  Regex.scan(~r/[+-]?\d+/, jsonString)
+  |> Enum.map(fn [numString] ->
+    {num, ""} = Integer.parse(numString)
+    num
+  end)
+  |> Enum.sum()
+
+IO.puts("Number sum: #{numberSum}")
+
+defmodule JsonParser do
+  def sumNonRedNumbers(<<"{" <> rest>>) do
+    [{:end, redStatus, sum, rest}] =
+      Stream.iterate({:open, :not_red, 0, rest}, fn {_, redStatus, sum, rest} ->
+        {endNow, newRedStaus, subSum, rest} = readObjectContent(rest)
+
+        {endNow,
+         if newRedStaus == :red do
+           :red
+         else
+           redStatus
+         end, sum + subSum, rest}
+      end)
+      |> Stream.filter(fn
+        {:end, _, _, _} -> true
+        _ -> false
+      end)
+      |> Enum.take(1)
+
+    sum =
+      if redStatus == :red do
+        0
+      else
+        sum
+      end
+
+    {sum, rest}
+  end
+
+  def sumNonRedNumbers(<<"\"" <> rest>>) do
+    [_, rest] = String.split(rest, "\"", parts: 2)
+    {0, rest}
+  end
+
+  def sumNonRedNumbers(<<"[" <> rest>>) do
+    [{:end, sum, rest}] =
+      Stream.iterate({:open, 0, rest}, fn {_, sum, rest} ->
+        {endNow, subSum, rest} = readArrayContent(rest)
+        {endNow, sum + subSum, rest}
+      end)
+      |> Stream.filter(fn
+        {:end, _, _} -> true
+        _ -> false
+      end)
+      |> Enum.take(1)
+
+    {sum, rest}
+  end
+
+  def sumNonRedNumbers(numberNext) do
+    Integer.parse(numberNext)
+  end
+
+  def readObjectContent(<<"\"" <> rest>>) do
+    [_, rest] = String.split(rest, "\":", parts: 2)
+
+    case rest do
+      <<"\"red\"" <> rest>> ->
+        {:open, :red, 0, rest}
+
+      _ ->
+        {sum, rest} = sumNonRedNumbers(rest)
+        {:open, :not_red, sum, rest}
+    end
+  end
+
+  def readObjectContent(<<"," <> rest>>) do
+    {:open, :not_red, 0, rest}
+  end
+
+  def readObjectContent(<<"}" <> rest>>) do
+    {:end, :not_red, 0, rest}
+  end
+
+  def readArrayContent(<<"," <> rest>>) do
+    {:open, 0, rest}
+  end
+
+  def readArrayContent(<<"]" <> rest>>) do
+    {:end, 0, rest}
+  end
+
+  def readArrayContent(json) do
+    {sum, rest} = sumNonRedNumbers(json)
+    {:open, sum, rest}
+  end
+end
+
+{nonRedNumbers, ""} = JsonParser.sumNonRedNumbers(jsonString)
+
+IO.puts("Non red number sum: #{nonRedNumbers}")
-- 
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