Add offline mode to flagsmith.rb

Author: zachaysan

lib/flagsmith.rb

@@ -1,4 +1,6 @@
 # frozen_string_literal: true
+require "pry"
+require "pry-byebug"
 
 require 'faraday'
 require 'faraday/retry'
@@ -16,6 +18,7 @@
 require 'flagsmith/sdk/pooling_manager'
 require 'flagsmith/sdk/models/flags'
 require 'flagsmith/sdk/models/segments'
+require 'flagsmith/sdk/offline_handlers'
 
 require 'flagsmith/engine/core'
 
@@ -44,7 +47,9 @@ class Client # rubocop:disable Metrics/ClassLength
     # Available Configs.
     #
     # :environment_key, :api_url, :custom_headers, :request_timeout_seconds, :enable_local_evaluation,
-    # :environment_refresh_interval_seconds, :retries, :enable_analytics, :default_flag_handler
+    # :environment_refresh_interval_seconds, :retries, :enable_analytics, :default_flag_handler,
+    # :offline_mode, :offline_handler
+    #
     # You can see full description in the Flagsmith::Config
 
     attr_reader :config, :environment
@@ -55,10 +60,24 @@ def initialize(config)
       @_mutex = Mutex.new
       @config = Flagsmith::Config.new(config)
 
+      validate_offline_mode!
+
       api_client
       analytics_processor
       environment_data_polling_manager
       engine
+      load_offline_handler
+    end
+
+    def validate_offline_mode!
+      if @config.offline_mode? and not @config.offline_handler
+        raise Flagsmith::ClientError,
+              'The offline_mode config param requires a matching offline_handler.'
+      end
+      if @config.offline_handler and @config.default_flag_handler
+        raise Flagsmith::ClientError,
+        'Cannot use offline_handler and default_flag_handler at the same time.'
+      end
     end
 
     def api_client
@@ -79,6 +98,10 @@ def analytics_processor
         )
     end
 
+    def load_offline_handler
+      @environment = offline_handler.environment if offline_handler
+    end
+
     def environment_data_polling_manager
       return nil unless @config.local_evaluation?
 
@@ -103,7 +126,9 @@ def environment_from_api
     # Get all the default for flags for the current environment.
     # @returns Flags object holding all the flags for the current environment.
     def get_environment_flags # rubocop:disable Naming/AccessorMethodName
-      return environment_flags_from_document if @config.local_evaluation?
+      if @config.local_evaluation? or @config.offline_mode
+        return environment_flags_from_document
+      end
 
       environment_flags_from_api
     end
@@ -154,7 +179,7 @@ def get_value_for_identity(feature_name, user_id = nil, default: nil)
     def get_identity_segments(identifier, traits = {})
       unless environment
         raise Flagsmith::ClientError,
-              'Local evaluation required to obtain identity segments.'
+              'Local evaluation or offline handler is required to obtain identity segments.'
       end
 
       identity_model = build_identity_model(identifier, traits)
@@ -168,7 +193,8 @@ def environment_flags_from_document
       Flagsmith::Flags::Collection.from_feature_state_models(
         engine.get_environment_feature_states(environment),
         analytics_processor: analytics_processor,
-        default_flag_handler: default_flag_handler
+        default_flag_handler: default_flag_handler,
+        offline_handler: offline_handler,
       )
     end
 
@@ -178,35 +204,62 @@ def get_identity_flags_from_document(identifier, traits = {})
       Flagsmith::Flags::Collection.from_feature_state_models(
         engine.get_identity_feature_states(environment, identity_model),
         analytics_processor: analytics_processor,
-        default_flag_handler: default_flag_handler
+        default_flag_handler: default_flag_handler,
+        offline_handler: offline_handler,
       )
     end
 
     def environment_flags_from_api
-      rescue_with_default_handler do
-        api_flags = api_client.get(@config.environment_flags_url).body
-        api_flags = api_flags.select { |flag| flag[:feature_segment].nil? }
-        Flagsmith::Flags::Collection.from_api(
-          api_flags,
-          analytics_processor: analytics_processor,
-          default_flag_handler: default_flag_handler
-        )
+      if offline_handler
+        begin
+          return _environment_flags_from_api
+        rescue
+          return environment_flags_from_document
+        end
+      else
+        rescue_with_default_handler do
+          return _environment_flags_from_api
+        end
       end
     end
 
-    def get_identity_flags_from_api(identifier, traits = {})
-      rescue_with_default_handler do
-        data = generate_identities_data(identifier, traits)
-        json_response = api_client.post(@config.identities_url, data.to_json).body
+    def _environment_flags_from_api
+      api_flags = api_client.get(@config.environment_flags_url).body
+      api_flags = api_flags.select { |flag| flag[:feature_segment].nil? }
+      Flagsmith::Flags::Collection.from_api(
+        api_flags,
+        analytics_processor: analytics_processor,
+        default_flag_handler: default_flag_handler,
+        offline_handler: offline_handler
+      )
+    end
 
-        Flagsmith::Flags::Collection.from_api(
-          json_response[:flags],
-          analytics_processor: analytics_processor,
-          default_flag_handler: default_flag_handler
-        )
+    def get_identity_flags_from_api(identifier, traits = {})
+      if offline_handler
+        begin
+          return _get_identity_flags_from_api(identifier, traits)
+        rescue
+          return get_identity_flags_from_document(identifier, traits)
+        end
+      else
+        rescue_with_default_handler do
+          return _get_identity_flags_from_api(identifier, traits)
+        end
       end
     end
 
+    def _get_identity_flags_from_api(identifier, traits = {})
+      data = generate_identities_data(identifier, traits)
+      json_response = api_client.post(@config.identities_url, data.to_json).body
+
+      Flagsmith::Flags::Collection.from_api(
+        json_response[:flags],
+        analytics_processor: analytics_processor,
+        default_flag_handler: default_flag_handler,
+        offline_handler: offline_handler
+      )
+    end
+
     def rescue_with_default_handler
       yield
     rescue StandardError