From 88e5cb430afc4e03d5934bb8eaff0ca9bccb846c Mon Sep 17 00:00:00 2001
From: cryptogopher <git6453hub@michalczyk.pro>
Date: Wed, 6 Nov 2019 23:11:58 +0100
Subject: [PATCH] Quantity computation from formula

---
 app/models/ingredient.rb |  4 +++-
 app/models/quantity.rb   | 11 ++++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/app/models/ingredient.rb b/app/models/ingredient.rb
index 5547f90..45eb478 100644
--- a/app/models/ingredient.rb
+++ b/app/models/ingredient.rb
@@ -71,7 +71,9 @@ class Ingredient < ActiveRecord::Base
             i,
             input_q.map do |i_q|
               nutrient_data = (completed_q[i_q.name] || nutrients[i_q.name])[i.id]
-              [i_q.name, (nutrient_data || [nil, nil])[0]]
+              # FIXME: result for computation with nil values (substituted with 0s)
+              # should be marked as not precise
+              [i_q.name, (nutrient_data || [0, nil])[0]]
             end.to_h
           ]
         end
diff --git a/app/models/quantity.rb b/app/models/quantity.rb
index 7ed3757..08077f8 100644
--- a/app/models/quantity.rb
+++ b/app/models/quantity.rb
@@ -70,6 +70,15 @@ class Quantity < ActiveRecord::Base
   end
 
   def calculate(inputs)
-    inputs.map { |i, values| [i, 1.0] }
+    paramed_formula = Ripper.lex(formula).map do |*, ttype, token|
+      QUANTITY_TTYPES.include?(ttype) ? "params['#{token}']" : token
+    end.join
+    inputs.map { |i, values| [i, get_binding(values).eval(paramed_formula)] }
+  end
+
+  private
+
+  def get_binding(params)
+    binding
   end
 end