feat: get evaluation get result

Gemfile.lock

@@ -4,6 +4,7 @@ PATH
     flagsmith (4.3.0)
       faraday (>= 2.0.1)
       faraday-retry
+      jsonpath (~> 1.1)
       semantic
 
 GEM
@@ -21,8 +22,11 @@ GEM
       faraday (~> 2.0)
     gem-release (2.2.2)
     json (2.7.1)
+    jsonpath (1.1.5)
+      multi_json
     language_server-protocol (3.17.0.3)
     method_source (1.0.0)
+    multi_json (1.17.0)
     net-http (0.4.1)
       uri
     parallel (1.24.0)

flagsmith.gemspec

@@ -34,6 +34,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency 'faraday', '>= 2.0.1'
   spec.add_dependency 'faraday-retry'
+  spec.add_dependency 'jsonpath', '~> 1.1'
   spec.add_dependency 'semantic'
   spec.metadata['rubygems_mfa_required'] = 'true'
 end

lib/flagsmith/engine/evaluation/core.rb

@@ -1,20 +1,142 @@
 # frozen_string_literal: true
 
+require_relative '../utils/hash_func'
+require_relative '../features/constants'
+require_relative '../segments/evaluator'
+
 module Flagsmith
   module Engine
     module Evaluation
       # Core evaluation logic for feature flags
       module Core
+        extend self
+        include Flagsmith::Engine::Utils::HashFunc
+        include Flagsmith::Engine::Features::TargetingReasons
+        include Flagsmith::Engine::Segments::Evaluator
         # Get evaluation result from evaluation context
         #
         # @param evaluation_context [Hash] The evaluation context
         # @return [Hash] Evaluation result with flags and segments
-        def self.get_evaluation_result(_evaluation_context)
-          # TODO: Implement core evaluation logic
+        # returns EvaluationResultWithMetadata
+        def get_evaluation_result(evaluation_context)
+          evaluation_context = get_enriched_context(evaluation_context)
+          segments, segment_overrides = evaluate_segments(evaluation_context)
+          flags = evaluate_features(evaluation_context, segment_overrides)
           {
-            flags: {},
-            segments: []
+            flags: flags,
+            segments: segments
+          }
+        end
+
+        # Returns { segments: EvaluationResultSegments; segmentOverrides: Record<string, SegmentOverride>; }
+        def evaluate_segments(evaluation_context)
+          return [], {} if evaluation_context[:segments].nil?
+
+          identity_segments = get_segments_from_context(evaluation_context)
+
+          segments = identity_segments.map do |segment|
+            { name: segment[:name], metadata: segment[:metadata] }.compact
+          end
+
+          segment_overrides = process_segment_overrides(identity_segments)
+
+          [segments, segment_overrides]
+        end
+
+        # Returns Record<string: override.name, SegmentOverride>
+        def process_segment_overrides(identity_segments) # rubocop:disable Metrics/MethodLength
+          segment_overrides = {}
+
+          identity_segments.each do |segment|
+            Array(segment[:overrides]).each do |override|
+              next unless should_apply_override(override, segment_overrides)
+
+              segment_overrides[override[:name]] = {
+                feature: override,
+                segment_name: segment[:name]
+              }
+            end
+          end
+
+          segment_overrides
+        end
+
+        # returns EvaluationResultFlags<Metadata>
+        def evaluate_features(evaluation_context, segment_overrides)
+          identity_key = get_identity_key(evaluation_context)
+
+          (evaluation_context[:features] || {}).each_with_object({}) do |(_, feature), flags|
+            segment_override = segment_overrides[feature[:name]]
+            final_feature = segment_override ? segment_override[:feature] : feature
+
+            flag_result = build_flag_result(final_feature, identity_key, segment_override)
+            flags[final_feature[:name].to_sym] = flag_result
+          end
+        end
+
+        # Returns {value: any; reason?: string}
+        def evaluate_feature_value(feature, identity_key = nil)
+          return get_multivariate_feature_value(feature, identity_key) if feature[:variants]&.any? && identity_key
+
+          { value: feature[:value], reason: nil }
+        end
+
+        # Returns {value: any; reason?: string}
+        def get_multivariate_feature_value(feature, identity_key)
+          percentage_value = hashed_percentage_for_object_ids([feature[:key], identity_key])
+          sorted_variants = (feature[:variants] || []).sort_by { |v| v[:priority] || WEAKEST_PRIORITY }
+
+          variant = find_matching_variant(sorted_variants, percentage_value)
+          variant || { value: feature[:value], reason: nil }
+        end
+
+        def find_matching_variant(sorted_variants, percentage_value)
+          start_percentage = 0
+          sorted_variants.each do |variant|
+            limit = start_percentage + variant[:weight]
+            return { value: variant[:value], reason: "#{TARGETING_REASON_SPLIT}; weight=#{variant[:weight]}" } if start_percentage <= percentage_value && percentage_value < limit
+
+            start_percentage = limit
+          end
+          nil
+        end
+
+        # returns boolean
+        def should_apply_override(override, existing_overrides)
+          current_override = existing_overrides[override[:name]]
+          !current_override || stronger_priority?(override[:priority], current_override[:feature][:priority])
+        end
+
+        private
+
+        def build_flag_result(feature, identity_key, segment_override)
+          evaluated = evaluate_feature_value(feature, identity_key)
+
+          flag_result = {
+            name: feature[:name],
+            enabled: feature[:enabled],
+            value: evaluated[:value],
+            reason: evaluated[:reason] || (segment_override ? "#{TARGETING_REASON_TARGETING_MATCH}; segment=#{segment_override[:segment_name]}" : TARGETING_REASON_DEFAULT)
           }
+
+          flag_result[:metadata] = feature[:metadata] if feature[:metadata]
+          flag_result
+        end
+
+        # Extract identity key from evaluation context
+        #
+        # @param evaluation_context [Hash] The evaluation context
+        # @return [String, nil] The identity key or nil if no identity
+        def get_identity_key(evaluation_context)
+          return nil unless evaluation_context[:identity]
+
+          evaluation_context[:identity][:key] ||
+            "#{evaluation_context[:environment][:key]}_#{evaluation_context[:identity][:identifier]}"
+        end
+
+        # returns boolean
+        def stronger_priority?(priority_a, priority_b)
+          (priority_a || WEAKEST_PRIORITY) < (priority_b || WEAKEST_PRIORITY)
         end
       end
     end

lib/flagsmith/engine/features/constants.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Flagsmith
+  module Engine
+    module Features
+      # Targeting reason constants for evaluation results
+      module TargetingReasons
+        TARGETING_REASON_DEFAULT = 'DEFAULT'
+        TARGETING_REASON_TARGETING_MATCH = 'TARGETING_MATCH'
+        TARGETING_REASON_SPLIT = 'SPLIT'
+      end
+    end
+  end
+end