Fix inconsistent chunking

The chunking performed within RestorePlan#price and Cli#restore was
inconsistent. This did not show because of the memoization that existed
previously.

Author: bjorne

lib/tina/cli.rb

@@ -16,9 +16,9 @@ def restore(prefix_file)
 
       prefixes = File.readlines(prefix_file).map(&:chomp)
       objects = RestorePlan::ObjectCollection.new(s3_client.list_bucket_prefixes(prefixes))
-      restore_plan = RestorePlan.new(total_storage.to_i, objects)
-      price = restore_plan.price(duration_in_seconds)
-      chunks = objects.chunk(duration_in_seconds)
+      restore_plan = RestorePlan.new(total_storage.to_i, objects, duration_in_seconds)
+      price = restore_plan.price
+      chunks = restore_plan.object_chunks
       say
       say "Restores will be performed in the following chunks:"
       say "-" * 60

lib/tina/restore_plan.rb

@@ -5,31 +5,34 @@ class RestorePlan
     DAYS_PER_MONTH = 30
     PRICE_PER_GB_PER_HOUR = 0.011
 
-    def initialize(total_storage_size, objects, options = {})
+    def initialize(total_storage_size, objects, total_time, options = {})
       @total_storage_size = total_storage_size
       @objects = objects
+      @total_time = [@total_time, 4 * 3600].max
       @price_per_gb_per_hour = options[:price_per_gb_per_hour] || PRICE_PER_GB_PER_HOUR
 
       @daily_allowance = @total_storage_size * MONTHLY_FREE_TIER_ALLOWANCE_FACTOR / DAYS_PER_MONTH
     end
 
-    def price(total_time)
-      total_time = [total_time, 4 * 3600].max
-      chunk_size = quadhourly_restore_rate(total_time)
-      chunks = @objects.chunk(chunk_size)
-      largest_chunk_object_size = chunks.map { |chunk| chunk.map(&:size).reduce(&:+) }.max
-      quadhours = chunks.size
+    def price
+      largest_chunk_object_size = object_chunks.map { |chunk| chunk.map(&:size).reduce(&:+) }.max
+      quadhours = object_chunks.size
       quadhourly_allowance = @daily_allowance / ( [(24 / 4), quadhours].min * 4)
 
       peak_retrieval_rate = largest_chunk_object_size / 4
       peak_billable_retrieval_rate = [0, peak_retrieval_rate - quadhourly_allowance].max
 
       peak_billable_retrieval_rate * (@price_per_gb_per_hour / 1024 ** 3) * 720
     end
+
+    def object_chunks
+      @object_chunks ||= @objects.chunk(quadhourly_restore_rate)
+    end
+
     private
 
-    def quadhourly_restore_rate(total_time)
-      @objects.total_size / (total_time / (4 * 3600))
+    def quadhourly_restore_rate
+      @objects.total_size / (@total_time / (4 * 3600))
     end
 
     class ObjectCollection