Port Gitlab::JsonCache to CE

lib/gitlab/json_cache.rb

+# frozen_string_literal: true
+
+module Gitlab
+  class JsonCache
+    attr_reader :backend, :cache_key_with_version, :namespace
+
+    def initialize(options = {})
+      @backend = options.fetch(:backend, Rails.cache)
+      @namespace = options.fetch(:namespace, nil)
+      @cache_key_with_version = options.fetch(:cache_key_with_version, true)
+    end
+
+    def active?
+      if backend.respond_to?(:active?)
+        backend.active?
+      else
+        true
+      end
+    end
+
+    def cache_key(key)
+      expanded_cache_key = [namespace, key].compact
+
+      if cache_key_with_version
+        expanded_cache_key << Rails.version
+      end
+
+      expanded_cache_key.join(':')
+    end
+
+    def expire(key)
+      backend.delete(cache_key(key))
+    end
+
+    def read(key, klass = nil)
+      value = backend.read(cache_key(key))
+      value = parse_value(value, klass) if value
+      value
+    end
+
+    def write(key, value, options = nil)
+      backend.write(cache_key(key), value.to_json, options)
+    end
+
+    def fetch(key, options = {}, &block)
+      klass = options.delete(:as)
+      value = read(key, klass)
+
+      return value unless value.nil?
+
+      value = yield
+
+      write(key, value, options)
+
+      value
+    end
+
+    private
+
+    def parse_value(raw, klass)
+      value = ActiveSupport::JSON.decode(raw)
+
+      case value
+      when Hash then parse_entry(value, klass)
+      when Array then parse_entries(value, klass)
+      else
+        value
+      end
+    rescue ActiveSupport::JSON.parse_error
+      nil
+    end
+
+    def parse_entry(raw, klass)
+      klass.new(raw) if valid_entry?(raw, klass)
+    end
+
+    def valid_entry?(raw, klass)
+      return false unless klass && raw.is_a?(Hash)
+
+      (raw.keys - klass.attribute_names).empty?
+    end
+
+    def parse_entries(values, klass)
+      values.map { |value| parse_entry(value, klass) }.compact
+    end
+  end
+end