Fragment caching (#8)

Author: beauby

README.md

@@ -48,7 +48,7 @@ class ResourceInterface
   # @return [String]
   def jsonapi_id; end
 
-  # Returns a hash containing, for each included relationship, an array of the 
+  # Returns a hash containing, for each included relationship, an array of the
   # resources to be included from that one.
   # @param included_relationships [Array<Symbol>] The keys of the relationships
   #   to be included.
@@ -57,8 +57,8 @@ class ResourceInterface
 
   # Returns a JSON API-compliant representation of the resource as a hash.
   # @param options [Hash]
-  #   @option fields [Array<Symbol>, Nil] The requested fields, or nil.
-  #   @option include [Array<Symbol>] The requested relationships to 
+  #   @option fields [Set<Symbol>, Nil] The requested fields, or nil.
+  #   @option include [Set<Symbol>] The requested relationships to
   #     include (defaults to []).
   # @return [Hash]
   def as_jsonapi(options = {}); end
@@ -100,6 +100,32 @@ returns a JSON API-compliant representation of the error.
 
 This returns a JSON API compliant hash representing the described document.
 
+### Caching
+
+The generated JSON fragments can be cached in any cache implementation
+supporting the `fetch_multi` method.
+
+When using caching, the serializable resources must implement an
+additional `jsonapi_cache_key` method:
+```ruby
+  # Returns a cache key for the resource, parametered by the `include` and
+  #   `fields` options.
+  # @param options [Hash]
+  #   @option fields [Set<Symbol>, Nil] The requested fields, or nil.
+  #   @option include [Set<Symbol>] The requested relationships to
+  #     include (defaults to []).
+  # @return [String]
+  def jsonapi_cache_key(options = {}); end
+```
+
+The cache instance must be passed to the renderer as follows:
+```ruby
+JSONAPI.render(data: resources,
+               include: include_string,
+               fields: fields_hash,
+               cache: cache_instance)
+```
+
 ## License
 
 jsonapi-renderer is released under the [MIT License](http://www.opensource.org/licenses/MIT).

lib/jsonapi/renderer/cached_resources_processor.rb

@@ -0,0 +1,42 @@
+require 'jsonapi/renderer/resources_processor'
+
+module JSONAPI
+  class Renderer
+    # @private
+    class CachedResourcesProcessor < ResourcesProcessor
+      class JSONString < String
+        def to_json(*)
+          self
+        end
+      end
+
+      def initialize(cache)
+        @cache = cache
+      end
+
+      def process_resources
+        [@primary, @included].each do |resources|
+          cache_hash = cache_key_map(resources)
+          processed_resources = @cache.fetch_multi(cache_hash.keys) do |key|
+            res, include, fields = cache_hash[key]
+            json = res.as_jsonapi(include: include, fields: fields).to_json
+
+            JSONString.new(json)
+          end
+
+          resources.replace(processed_resources.values)
+        end
+      end
+
+      def cache_key_map(resources)
+        resources.each_with_object({}) do |res, h|
+          ri = [res.jsonapi_type, res.jsonapi_id]
+          include_dir = @include_rels[ri]
+          fields = @fields[ri.first.to_sym]
+          h[res.jsonapi_cache_key(include: include_dir, fields: fields)] =
+            [res, include_dir, fields]
+        end
+      end
+    end
+  end
+end

lib/jsonapi/renderer/document.rb

@@ -1,5 +1,6 @@
 require 'jsonapi/include_directive'
-require 'jsonapi/renderer/resources_processor'
+require 'jsonapi/renderer/simple_resources_processor'
+require 'jsonapi/renderer/cached_resources_processor'
 
 module JSONAPI
   class Renderer
@@ -12,6 +13,7 @@ def initialize(params = {})
         @fields  = _symbolize_fields(params[:fields] || {})
         @jsonapi = params[:jsonapi]
         @include = JSONAPI::IncludeDirective.new(params[:include] || {})
+        @cache   = params[:cache]
       end
 
       def to_hash
@@ -36,13 +38,21 @@ def document_hash
 
       def data_hash
         primary, included =
-          ResourcesProcessor.new(Array(@data), @include, @fields).process
+          resources_processor.process(Array(@data), @include, @fields)
         {}.tap do |hash|
           hash[:data]     = @data.respond_to?(:to_ary) ? primary : primary[0]
           hash[:included] = included if included.any?
         end
       end
 
+      def resources_processor
+        if @cache
+          CachedResourcesProcessor.new(@cache)
+        else
+          SimpleResourcesProcessor.new
+        end
+      end
+
       def errors_hash
         {}.tap do |hash|
           hash[:errors] = @errors.flat_map(&:as_jsonapi)

lib/jsonapi/renderer/resources_processor.rb

@@ -2,14 +2,13 @@
 
 module JSONAPI
   class Renderer
+    # @api private
     class ResourcesProcessor
-      def initialize(resources, include, fields)
+      def process(resources, include, fields)
         @resources = resources
         @include   = include
         @fields    = fields
-      end
 
-      def process
         traverse_resources
         process_resources
 
@@ -73,14 +72,7 @@ def enqueue_resource(res, prefix, include_dir)
       end
 
       def process_resources
-        [@primary, @included].each do |resources|
-          resources.map! do |res|
-            ri = [res.jsonapi_type, res.jsonapi_id]
-            include_dir = @include_rels[ri]
-            fields = @fields[res.jsonapi_type.to_sym]
-            res.as_jsonapi(include: include_dir, fields: fields)
-          end
-        end
+        raise 'Not implemented'
       end
     end
   end

lib/jsonapi/renderer/simple_resources_processor.rb

@@ -0,0 +1,19 @@
+require 'jsonapi/renderer/resources_processor'
+
+module JSONAPI
+  class Renderer
+    # @api private
+    class SimpleResourcesProcessor < ResourcesProcessor
+      def process_resources
+        [@primary, @included].each do |resources|
+          resources.map! do |res|
+            ri = [res.jsonapi_type, res.jsonapi_id]
+            include_dir = @include_rels[ri]
+            fields = @fields[res.jsonapi_type.to_sym]
+            res.as_jsonapi(include: include_dir, fields: fields)
+          end
+        end
+      end
+    end
+  end
+end

spec/caching_spec.rb

@@ -0,0 +1,101 @@
+require 'spec_helper'
+
+class Cache
+  def initialize
+    @cache = {}
+  end
+
+  def fetch_multi(keys)
+    keys.each_with_object({}) do |k, h|
+      @cache[k] = yield(k) unless @cache.key?(k)
+      h[k] = @cache[k]
+    end
+  end
+end
+
+describe JSONAPI::Renderer, '#render' do
+  before(:all) do
+    @users = [
+      UserResource.new(1, 'User 1', '123 Example st.', []),
+      UserResource.new(2, 'User 2', '234 Example st.', []),
+      UserResource.new(3, 'User 3', '345 Example st.', []),
+      UserResource.new(4, 'User 4', '456 Example st.', [])
+    ]
+    @posts = [
+      PostResource.new(1, 'Post 1', 'yesterday', @users[1]),
+      PostResource.new(2, 'Post 2', 'today', @users[0]),
+      PostResource.new(3, 'Post 3', 'tomorrow', @users[1])
+    ]
+    @users[0].posts = [@posts[1]]
+    @users[1].posts = [@posts[0], @posts[2]]
+  end
+
+  it 'renders included relationships' do
+    cache = Cache.new
+    # Warm up the cache.
+    subject.render(data: @users[0],
+                   include: 'posts',
+                   cache: cache)
+    # Actual call on warm cache.
+    actual = subject.render(data: @users[0],
+                            include: 'posts',
+                            cache: cache)
+    expected = {
+      data: {
+        type: 'users',
+        id: '1',
+        attributes: {
+          name: 'User 1',
+          address: '123 Example st.'
+        },
+        relationships: {
+          posts: {
+            data: [{ type: 'posts', id: '2' }],
+            links: {
+              self: 'http://api.example.com/users/1/relationships/posts',
+              related: {
+                href: 'http://api.example.com/users/1/posts',
+                meta: {
+                  do_not_use: true
+                }
+              }
+            },
+            meta: {
+              deleted_posts: 5
+            }
+          }
+        },
+        links: {
+          self: 'http://api.example.com/users/1'
+        },
+        meta: {
+          user_meta: 'is_meta'
+        }
+      },
+      included: [
+        {
+          type: 'posts',
+          id: '2',
+          attributes: {
+            title: 'Post 2',
+            date: 'today'
+          },
+          relationships: {
+            author: {
+              links: {
+                self: 'http://api.example.com/posts/2/relationships/author',
+                related: 'http://api.example.com/posts/2/author'
+              },
+              meta: {
+                author_active: true
+              }
+            }
+          }
+        }
+      ]
+    }
+
+    expect(JSON.parse(actual.to_json)).to eq(JSON.parse(expected.to_json))
+    expect(actual[:data]).to be_a(JSONAPI::Renderer::CachedResourcesProcessor::JSONString)
+  end
+end