From 8c02e85eb01146bb4a891dc58bf6e94b077b4741 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Wed, 20 Dec 2023 20:52:14 -0800
Subject: [PATCH] 2023 Day 20 Part 2

---
 2023/day20.rb | 154 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 153 insertions(+), 1 deletion(-)

diff --git a/2023/day20.rb b/2023/day20.rb
index db84d1d..da87c15 100644
--- a/2023/day20.rb
+++ b/2023/day20.rb
@@ -4,6 +4,46 @@
 require 'sorbet-runtime'
 require 'sorbet-struct-comparable'
 
+extend T::Sig
+
+sig { params(cond: T::Boolean, msg: String).void }
+def assert(cond, msg)
+  raise StandardError, msg unless cond
+end
+
+sig { params(a: Integer, b: Integer).returns(Integer) }
+def gcd(a, b)
+  while b != 0
+    a, b = b, a % b
+  end
+  a
+end
+
+sig { params(nums: T::Array[Integer]).returns(Integer) }
+def gcd_all(nums)
+  if nums.length == 0
+    return 0
+  end
+
+  result = 1
+  nums.each do |n|
+    result = gcd(result, T.must(n))
+  end
+  result
+end
+
+
+sig { params(nums: T::Array[Integer]).returns(Integer) }
+def lcm(nums)
+  gcd = gcd_all(nums)
+
+  result = 1
+  nums.each do |n|
+    result *= n / gcd
+  end
+  result
+end
+
 module Day20
   class Pulse < T::Enum
     enums do
@@ -186,6 +226,103 @@ module Day20
 
       counts
     end
+
+    sig { returns(T::Array[Integer])}
+    def run
+      gate_firsts = T.let({}, T::Hash[String, Integer])
+
+      count = 0
+      while true
+        count += 1
+
+        queue = T.let([], T::Array[Wire])
+        queue << Wire::new(src: 'button', dst: 'broadcaster', pulse: Pulse::Low)
+
+        while !queue.empty?
+          wire = T.must(queue.shift)
+
+          if wire.pulse == Pulse::High and @gates.any?(wire.src)
+            gate_firsts[wire.src] = gate_firsts[wire.src] || count
+          end
+
+          mod = @modules[wire.dst] or next
+          mod.handle(wire.src, wire.pulse).each do |output|
+            queue << output
+          end
+        end
+
+        if @gates.all? { |g| !gate_firsts[g].nil? }
+          return gate_firsts.values
+        end
+      end
+    end
+
+    def assert_conditions
+      tx = []
+      @modules.each_pair do |name, mod|
+        tx << name if mod.dests.any?('rx')
+      end
+
+      case tx.length
+      when 1
+        @tx = tx[0]
+      when 0
+        raise StandardError, 'no transmitter'
+      else
+        pp tx
+        raise StandardError, 'more than one transmitter'
+      end
+
+      @gates = []
+      @modules.each_pair do |name, mod|
+        if mod.dests.any?(@tx)
+          @gates << name
+          assert mod.dests.length == 1, 'Gate emits to non-tx'
+        end
+      end
+
+      @exits = []
+      @modules.each_pair do |name, mod|
+        ix = mod.dests & @gates
+        next if ix.empty?
+
+        @exits << name
+      end
+    end
+
+    sig { params(gv: String, png: String).void }
+    def show_graph(gv, png)
+      File.open(gv, 'w') do |f|
+        f.puts('strict digraph Day20 {')
+        @modules.each_pair do |name, mod|
+          color = case mod
+          when FlipFlop    then '#5FD65D'
+          when Conjunction then '#00D7FF'
+          else if name == 'rx' then '#FF875F' else 'black' end
+          end
+          label = T.must(mod.class.name).split('::').last
+          exit = if @exits.any?(name) then '*' else '' end
+
+          f.puts("#{name} [fontcolor=\"#{color}\",label=\"\\N\\n#{exit}#{label}\"];")
+          mod.dests.each do |dst|
+            f.puts("#{name} -> #{dst};")
+          end
+        end
+        f.puts('}')
+      end
+
+      system('dot', '-Tpng', gv, out: png)
+      # system('imv', png)
+    end
+
+    sig { returns(T::Hash[String, T.any(T::Boolean, T::Hash[String, Pulse])])}
+    def state
+      state = {}
+      @modules.each_pair do |name, mod|
+
+      end
+      state
+    end
   end
 
   class << self
@@ -203,8 +340,23 @@ module Day20
       end
       high * low
     end
+
+    sig { params(path: String).returns(Integer) }
+    def part2(path)
+      text = File.read(path)
+      machine = Machine::new(text)
+
+      machine.assert_conditions
+
+      gv  = File.join(File.dirname(path), "day20.gv")
+      png = File.join(File.dirname(path), "day20.png")
+      machine.show_graph(gv, png)
+      counts = machine.run
+      lcm(counts)
+    end
   end
 end
 
-puts Day20::part1 File.join(__dir__, 'input/test.txt')
+# puts Day20::part1 File.join(__dir__, 'input/test.txt')
 puts Day20::part1 File.join(__dir__, 'input/day20.txt')
+puts Day20::part2 File.join(__dir__, 'input/day20.txt')