Solution

store.rb

@@ -1 +1,132 @@
-# Yout little input goes here!
+require 'rubygems'
+require 'json'
+require 'bigdecimal'
+
+class Store
+  def initialize
+    @items = []
+    @purchased_items = {}
+  end
+
+  def import_items(filepath)
+    data = JSON.parse(open(filepath).read())
+    data.each do |row|
+      @items << StoreItem.new(
+          row["name"],
+          row["category"],
+          row["color"],
+          row["size"],
+          BigDecimal.new(row["price"].to_s),
+          row["in_store"]
+      )
+    end
+  end
+
+  def categories
+    @items.map(&:category).uniq
+  end
+
+  def items_sorted_by(property, sorting)
+    sorted_items = @items.sort_by { |i| i.send(property) }
+    sorting == :desc ? sorted_items.reverse : sorted_items
+  end
+
+  def unique_articles_in_category(category)
+    search(:category => category).map(&:name).uniq
+  end
+
+  def search(criteria)
+    def harmonize(value)
+      case value
+        when String
+          return value.downcase
+        else
+          return value
+      end
+    end
+
+    @items.select do |row|
+      !criteria.map { |k, v| harmonize(row.send(k)) == harmonize(v) }.include?(false)
+    end
+  end
+
+  def total_sale
+    @purchased_items.map do |store_item, quantity|
+      quantity * store_item.price
+    end.inject(&:+) || 0
+  end
+
+  def purchase_item(store_item, quantity)
+    purchased_count = @purchased_items.fetch(store_item, 0)
+    @purchased_items[store_item] = purchased_count + quantity
+    store_item.in_store -= quantity
+  end
+
+  class Cart
+    attr_reader :store
+
+    def initialize(store)
+      @store = store
+      @items = {}
+    end
+
+    def add_item(store_item, quantity = 1)
+      previous_quantity = @items.fetch(store_item, 0)
+      quantity = store_item.in_store < previous_quantity + quantity ? store_item.in_store - previous_quantity : quantity
+      return if quantity <= 0
+      @items[store_item] = previous_quantity + quantity
+    end
+
+    def checkout!
+      @items.each do |store_item, quantity|
+        @store.purchase_item(store_item, quantity)
+      end
+    end
+
+    def items
+      @items.keys
+    end
+
+    def total_items
+      @items.values.inject(&:+)
+    end
+
+    def total_cost
+      @items.map do |store_item, quantity|
+        quantity * store_item.price
+      end.inject(&:+) || 0
+    end
+
+    def unique_items
+      @items.keys
+    end
+
+    class CartItem
+      attr_reader :store_item, :quantity
+
+      def initialize(store_item, quantity)
+        @store_item = store_item
+        @quantity = quantity
+      end
+    end
+  end
+
+  class StoreItem
+    attr_reader :name, :category, :color, :size, :price, :in_store
+    attr_writer :in_store
+
+    def initialize(name, category, color, size, price, in_store)
+      @name = name
+      @category = category
+      @color = color
+      @size = size
+      @price = price
+      @in_store = in_store
+    end
+
+    def available
+      @in_store > 0
+    end
+  end
+end
+