[Feature] Implement Payload Converters (#49)

* Rename dummy Converter into DataConverter

* Implement converter interface and all the default converters

* Rename Converter to PayloadConverter

* Add default payload converters

* Add tests for the DataConverter

Author: antstorm

lib/temporal/client.rb

@@ -2,7 +2,7 @@
 require 'securerandom'
 require 'socket'
 require 'temporal/errors'
-require 'temporal/converter'
+require 'temporal/data_converter'
 require 'temporal/client/workflow_handle'
 require 'temporal/client/implementation'
 require 'temporal/workflow/id_reuse_policy'
@@ -14,8 +14,8 @@ class Client
     # TODO: More argument to follow for converters, codecs, etc
     def initialize(connection, namespace, interceptors: [])
       @namespace = namespace
-      converter = Converter.new
-      @implementation = Client::Implementation.new(connection, namespace, converter, interceptors)
+      data_converter = DataConverter.new
+      @implementation = Client::Implementation.new(connection, namespace, data_converter, interceptors)
     end
 
     def start_workflow( # rubocop:disable Metrics/ParameterLists

lib/temporal/converter.rb renamed to lib/temporal/data_converter.rb

@@ -1,9 +1,10 @@
-require 'json'
+require 'temporal/payload_converter'
 
-# TODO: This is a dummy converter, a proper implementation will follow
 module Temporal
-  class Converter
-    JSON_ENCODING = 'json/plain'.freeze
+  class DataConverter
+    def initialize(payload_converter: Temporal::PayloadConverter::DEFAULT)
+      @payload_converter = payload_converter
+    end
 
     def to_payloads(data)
       return if data.nil? || Array(data).empty?
@@ -33,17 +34,14 @@ def from_payload_map(payload_map)
 
     private
 
+    attr_reader :payload_converter
+
     def to_payload(data)
-      Temporal::Api::Common::V1::Payload.new(
-        metadata: { 'encoding' => JSON_ENCODING },
-        data: JSON.generate(data).b,
-      )
+      payload_converter.to_payload(data)
     end
 
     def from_payload(payload)
-      if payload.metadata['encoding'] == JSON_ENCODING
-        JSON.parse(payload.data)
-      end
+      payload_converter.from_payload(payload)
     end
   end
 end

lib/temporal/payload_converter.rb

@@ -0,0 +1,14 @@
+require 'temporal/payload_converter/bytes'
+require 'temporal/payload_converter/composite'
+require 'temporal/payload_converter/json'
+require 'temporal/payload_converter/nil'
+
+module Temporal
+  module PayloadConverter
+    DEFAULT = Temporal::PayloadConverter::Composite.new(
+      Temporal::PayloadConverter::Nil.new,
+      Temporal::PayloadConverter::Bytes.new,
+      Temporal::PayloadConverter::JSON.new,
+    )
+  end
+end

lib/temporal/payload_converter/base.rb

@@ -0,0 +1,13 @@
+module Temporal
+  module PayloadConverter
+    class Base
+      def to_payload(_data)
+        raise NoMethodError, 'must implement #to_payload'
+      end
+
+      def from_payload(_payload)
+        raise NoMethodError, 'must implement #from_payload'
+      end
+    end
+  end
+end

lib/temporal/payload_converter/bytes.rb

@@ -0,0 +1,26 @@
+require 'temporal/payload_converter/encoding_base'
+
+module Temporal
+  module PayloadConverter
+    class Bytes < EncodingBase
+      ENCODING = 'binary/plain'.freeze
+
+      def encoding
+        ENCODING
+      end
+
+      def from_payload(payload)
+        payload.data
+      end
+
+      def to_payload(data)
+        return nil unless data.is_a?(String) && data.encoding == Encoding::ASCII_8BIT
+
+        Temporal::Api::Common::V1::Payload.new(
+          metadata: { 'encoding' => ENCODING },
+          data: data,
+        )
+      end
+    end
+  end
+end

lib/temporal/payload_converter/composite.rb

@@ -0,0 +1,47 @@
+require 'temporal/payload_converter/base'
+require 'temporal/errors'
+
+module Temporal
+  module PayloadConverter
+    class Composite < Base
+      class ConverterNotFound < Temporal::Error; end
+      class EncodingNotSet < Temporal::Error; end
+
+      def initialize(*converters)
+        super()
+
+        @converters = converters.each_with_object({}) do |converter, result|
+          result[converter.encoding] = converter
+          result
+        end
+      end
+
+      def to_payload(data)
+        converters.each_value do |converter|
+          payload = converter.to_payload(data)
+          return payload unless payload.nil?
+        end
+
+        available = converters.values.map(&:class).join(', ')
+        raise ConverterNotFound, "Available converters (#{available}) could not convert data"
+      end
+
+      def from_payload(payload)
+        encoding = payload.metadata['encoding']
+        raise EncodingNotSet, 'Missing payload encoding' unless encoding
+
+        converter = converters[encoding]
+        unless converter
+          available = converters.keys.join(', ')
+          raise ConverterNotFound, "Missing converter for encoding '#{encoding}' (available: #{available})"
+        end
+
+        converter.from_payload(payload)
+      end
+
+      private
+
+      attr_reader :converters
+    end
+  end
+end

lib/temporal/payload_converter/encoding_base.rb

@@ -0,0 +1,19 @@
+require 'temporal/api/common/v1/message_pb'
+
+module Temporal
+  module PayloadConverter
+    class EncodingBase
+      def encoding
+        raise NoMethodError, 'must implement #encoding'
+      end
+
+      def to_payload(_data)
+        raise NoMethodError, 'must implement #to_payload'
+      end
+
+      def from_payload(_payload)
+        raise NoMethodError, 'must implement #from_payload'
+      end
+    end
+  end
+end

lib/temporal/payload_converter/json.rb

@@ -0,0 +1,25 @@
+require 'json/ext'
+require 'temporal/payload_converter/encoding_base'
+
+module Temporal
+  module PayloadConverter
+    class JSON < EncodingBase
+      ENCODING = 'json/plain'.freeze
+
+      def encoding
+        ENCODING
+      end
+
+      def from_payload(payload)
+        ::JSON.parse(payload.data, create_additions: true)
+      end
+
+      def to_payload(data)
+        Temporal::Api::Common::V1::Payload.new(
+          metadata: { 'encoding' => ENCODING },
+          data: ::JSON.generate(data).b,
+        )
+      end
+    end
+  end
+end

lib/temporal/payload_converter/nil.rb

@@ -0,0 +1,25 @@
+require 'temporal/payload_converter/encoding_base'
+
+module Temporal
+  module PayloadConverter
+    class Nil < EncodingBase
+      ENCODING = 'binary/null'.freeze
+
+      def encoding
+        ENCODING
+      end
+
+      def from_payload(_payload)
+        nil
+      end
+
+      def to_payload(data)
+        return nil unless data.nil?
+
+        Temporal::Api::Common::V1::Payload.new(
+          metadata: { 'encoding' => ENCODING },
+        )
+      end
+    end
+  end
+end

sig/payload_converter.rbs

@@ -0,0 +1,5 @@
+module Temporal
+  module PayloadConverter
+    DEFAULT: _PayloadConverter
+  end
+end