v0.2.1 with feed encryption helpers

README.md

@@ -59,6 +59,27 @@ require 'fulfillment-outbound-api-model'
 
 This is a handy way to see all the API model class names and corresponding files you need to require for them, e.g. require 'finances-api-model' to use https://www.rubydoc.info/gems/amz_sp_api/AmzSpApi/FinancesApiModel/DefaultApi 
 
+## Feeds
+
+This gem also offers encrypt/decrypt helper methods for feeds, but actually using that API as per https://github.com/amzn/selling-partner-api-docs/blob/main/guides/en-US/use-case-guides/feeds-api-use-case-guide requires the following calls:
+
+```ruby
+feeds = AmzSpApi::FeedsApiModel::FeedsApi.new(AmzSpApi::SpApiClient.new)
+response = feeds.create_feed_document({"contentType" => content_type})
+feed_document_id = response&.payload&.dig(:feedDocumentId)
+url = response.payload[:url]
+encrypted = AmzSpApi.encrypt_feed(feed_content, response.payload)
+# PUT to url with lowercase "content-type" header, it's already pre-signed
+response = feeds.create_feed({"feedType" => feed_type, "marketplaceIds" => marketplace_ids, "inputFeedDocumentId" => feed_document_id})
+feed_id = response&.payload&.dig(:feedId)
+response = feeds.get_feed(feed_id)
+result_feed_document_id = response&.payload&.dig(:resultFeedDocumentId) # present once it is successful
+response = feeds.get_feed_document(result_feed_document_id)
+url = response&.payload&.dig(:url)
+# GET response&.payload&.dig(:url) into ciphertext, again it's pre-signed so no authorization needed
+AmzSpApi.decrypt_and_inflate_feed(ciphertext, response.payload)
+```
+
 ## Thanks
 
 to https://github.com/patterninc/muffin_man as the basis for [sp_api_client.rb](lib/sp_api_client.rb)

lib/amz_sp_api.rb

@@ -15,5 +15,38 @@ def configure
         SpConfiguration.default
       end
     end
+
+    def encrypt_feed(feed_content, feed_document_response_payload)
+      cipher = feed_cipher(feed_document_response_payload, encrypt: true)
+      cipher.update(feed_content) + cipher.final
+    end
+
+    def decrypt_and_inflate_feed(ciphertext, feed_document_response_payload)
+      cipher = feed_cipher(feed_document_response_payload, encrypt: false)
+
+      compression = feed_document_response_payload[:compressionAlgorithm]
+      raise "unknown compressionAlgorithm #{compression}" if compression && compression != "GZIP"
+
+      result = cipher.update(ciphertext) + cipher.final
+      result = Zlib::Inflate.inflate(result) if compression
+      result
+    end
+
+    # from https://github.com/amzn/selling-partner-api-models/blob/main/clients/sellingpartner-api-documents-helper-java/src/main/java/com/amazon/spapi/documents/impl/AESCryptoStreamFactory.java
+    def feed_cipher(response, encrypt:)
+      key = Base64.decode64(response.dig(:encryptionDetails, :key))
+
+      cipher = case response.dig(:encryptionDetails, :standard)
+      when "AES"
+        OpenSSL::Cipher.new("AES-#{key.size * 8}-CBC")
+      else
+        raise "unknown encryption standard #{response.inspect}"
+      end
+
+      encrypt ? cipher.encrypt : cipher.decrypt
+      cipher.key = key
+      cipher.iv = Base64.decode64(response.dig(:encryptionDetails, :initializationVector))
+      cipher
+    end
   end
 end

lib/amz_sp_api_version.rb

@@ -1,3 +1,3 @@
 module AmzSpApi
-  VERSION = '0.2.0'
+  VERSION = '0.2.1'
 end