diff --git a/2019/ruby/day_14.rb b/2019/ruby/day_14.rb
new file mode 100644
index 0000000..453416e
--- /dev/null
+++ b/2019/ruby/day_14.rb
@@ -0,0 +1,41 @@
+reactions = ARGF.read.lines.map {|line|
+  input, output = line.split(" => ")
+  inputs = input.split(", ").map(&:split).each.with_object({}) {|(q,c),h| h[c] = q.to_i }
+  q, c = output.split
+  [c, { quantity: q.to_i, inputs: inputs }]
+}.to_h
+
+class Factory
+  attr_reader :ore_consumed
+
+  def initialize(reactions)
+    @reactions = reactions
+    @supply = Hash.new(0)
+    @supply["ORE"] = Float::INFINITY
+    @ore_consumed = 0
+  end
+
+  def produce(want)
+    case @reactions.fetch(want)
+    in { quantity: quantity, inputs: inputs }
+      until inputs.all? {|c,q| @supply[c] >= q }
+        inputs
+          .select {|c,q| @supply[c] < q }
+          .each do |c,q|
+            produce(c)
+          end
+      end
+
+      inputs.each do |c,q|
+        @supply[c] -= q
+      end
+
+      @ore_consumed += inputs.fetch("ORE") { 0 }
+      @supply[want] += quantity
+    end
+  end
+end
+
+factory = Factory.new(reactions)
+factory.produce("FUEL")
+puts factory.ore_consumed