feat: add inflation_rate

app/models/monetary_data.rb

@@ -8,30 +8,55 @@ def id
   end
 
   def nominal_apc
-    initial_supply = 33.6
-    secondary_supply_per_year = 1.344
     total_supplies_per_year.each_with_index.map do |_, index|
       cumulative_total_supply = index.zero? ? 0 : (0..index).reduce(0) { |memo, value| memo + total_supplies_per_year[value] }
-      total_supply_so_far = initial_supply + cumulative_total_supply
-      (secondary_supply_per_year / total_supply_so_far * 100).truncate(2)
+      total_supply_so_far = INITIAL_SUPPLY + cumulative_total_supply
+      (SECONDARY_SUPPLY_PER_YEAR / total_supply_so_far * 100).truncate(4)
     end
   end
 
+  def inflation_rate
+    secondary_issuance_monthly = SECONDARY_SUPPLY_PER_YEAR / 12
+    rs =
+      total_supplies_per_year(50).each_with_index.map do |_, index|
+        cumulative_total_supply = index.zero? ? 0 : (0..index).reduce(0) { |memo, value| memo + total_supplies_per_year[value] }
+        INITIAL_SUPPLY + cumulative_total_supply
+      end
+    primary_supplies_per_year.map { |item| item + secondary_issuance_monthly }.zip(rs).map { |item| item.reduce(:/) * 12 }
+  end
+
   private
 
-  def total_supplies_per_year
+  def total_supplies_per_year(max_year = 20)
     @total_supplies_per_year ||=
       begin
-        max_year = 20
         secondary_supply_per_month = SECONDARY_SUPPLY_PER_YEAR / 12
         total_supplies_per_year =
-          (0...max_year).map do |year|
-            primary_supply_per_year = 4.2/(2**(year / 4))
+          (0...max_year).each_with_index.map do |year, index|
+            primary_supply_per_year = 4.2 / (2**(year / 4))
             primary_supply_per_month = primary_supply_per_year / 12
-            [primary_supply_per_month + secondary_supply_per_month] * 12
+            if index.zero?
+              [0] + [primary_supply_per_month + secondary_supply_per_month] * 11
+            else
+              [primary_supply_per_month + secondary_supply_per_month] * 12
+            end
           end
 
         total_supplies_per_year.flatten
       end
   end
+
+  def primary_supplies_per_year
+    @primary_supplies_per_year ||=
+      begin
+        max_year = 50
+        primary_supplies_per_year =
+          (0...max_year).map do |year|
+            primary_supply_per_year = 4.2 / (2**(year / 4))
+            [primary_supply_per_year / 12] * 12
+          end
+
+        primary_supplies_per_year.flatten
+      end
+  end
 end