Added create_cart_params method to help with remote cart operations

lib/asin.rb

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 require 'httpi'
 require 'crack/xml'
 require 'cgi'
@@ -142,6 +143,49 @@ def search(params={:SearchIndex => :Books})
     (response['ItemSearchResponse']['Items']['Item'] || []).map {|item| Item.new(item)}
   end
 
+  # Takes an array of item => quantity pairs and returns a hash of usable parameters
+  # 
+  # [{:asin => "foo", :quantity => 2}, 
+  #  {:offer_listing_id => "bar", :quantity => 3}
+  #  {:cart_item_id => "baz", :quantity => 4}]
+  # 
+  # #=>
+  # 
+  # {
+  #   "Item.1.ASIN" => "foo",
+  #   "Item.1.Quantity" => 2,
+  #   "Item.2.OfferListingId" => "bar",
+  #   "Item.2.Quantity" => 3,
+  #   "Item.3.CartItemId" => "baz",
+  #   "Item.3.Quantity" => 3
+  # }
+
+  def create_cart_params(items)
+    item_identifiers = [:asin, :offer_listing_id, :cart_item_id]
+    item_identifiers_override_map = {:asin => "ASIN"}
+
+    items.reject! do |item|
+      !item.keys.any? {|key| item_identifiers.include? key}
+    end
+
+    items.map! do |item|
+      item.each do |key,value|
+        item[key.to_s.downcase.to_sym] = item.delete(key)
+      end
+    end
+
+    params = {}
+    items.each_with_index do |item_hash, index|
+      item_identifiers.each do |identifier|
+        param_key = item_identifiers_override_map[identifier] || 
+          identifier.to_s.split('_').map!{|m| m.capitalize}.join # poor-mans String#camelize
+        params["Item.#{index+1}.#{param_key}"] = item_hash[identifier] if item_hash.has_key?(identifier)
+      end
+      params["Item.#{index+1}.Quantity"] = item_hash[:quantity] || 1
+    end
+    params
+  end
+
   private
 
   def credentials_valid?

spec/asin_spec.rb

@@ -70,5 +70,45 @@
       items.first.title.should =~ /Nevermind/
     end
   end
+
+  context "cart operations" do
+    before do
+      @helper.configure :secret => @secret, :key => @key
+      @items = [
+                {:quantity=>3, :offer_listing_id=>"321"},
+                {:quantity=>2, :asin=>"foo"},
+                {:quantity=>4, :cart_item_id=>"bar"}]
+    end
+
+    describe "#create_cart_params" do
+      it "should filter items with a valid Item Identifier" do
+        items = @items + [{:foo => "bar"}]
+        @helper.create_cart_params(items).size.should == @items.size * 2
+      end
+
+      it "should use the default quantity of 1" do
+        items = [{:asin => "foo"}]
+        params = @helper.create_cart_params(items)
+        params["Item.1.Quantity"].should == 1
+      end
+
+      it "should reject items without a valid item identifier" do
+        items = [{:foo => "bar"}]
+        params = @helper.create_cart_params(items)
+        params.should be_empty
+      end
+
+      it "should return a valid hash of parameters" do
+        params = @helper.create_cart_params(@items)
+        params.keys.should be_any {|m| m =~ /Item\.\d\.ASIN/ }
+        params.keys.should be_any {|m| m =~ /Item\.\d\.OfferListingId/ }
+        params.keys.should be_any {|m| m =~ /Item\.\d\.CartItemId/ }
+        params.values.should include "321"
+        params.values.should include "foo"
+        params.values.should include "bar"
+      end      
+    end
+
+  end
 end