Add like service

app/services/like_service.rb

+class LikeService
+  def initialize(user=nil)
+    @user = user
+  end
+
+  def create(post_id)
+    post = post_service.find!(post_id)
+    user.like!(post)
+  end
+
+  def destroy(like_id)
+    like = Like.find(like_id)
+    if user.owns?(like)
+      user.retract(like)
+      true
+    else
+      false
+    end
+  end
+
+  def find_for_post(post_id)
+    likes = post_service.find!(post_id).likes
+    user ? likes.order("author_id = #{user.person.id} DESC") : likes
+  end
+
+  private
+
+  attr_reader :user
+
+  def post_service
+    @post_service ||= PostService.new(user)
+  end
+end

spec/services/like_service_spec.rb

+describe LikeService do
+  let(:post) { alice.post(:status_message, text: "hello", to: alice.aspects.first) }
+
+  describe "#create" do
+    it "creates a like on my own post" do
+      expect {
+        LikeService.new(alice).create(post.id)
+      }.not_to raise_error
+    end
+
+    it "creates a like on a post of a contact" do
+      expect {
+        LikeService.new(bob).create(post.id)
+      }.not_to raise_error
+    end
+
+    it "attaches the like to the post" do
+      like = LikeService.new(alice).create(post.id)
+      expect(post.likes.first.id).to eq(like.id)
+    end
+
+    it "fails if the post does not exist" do
+      expect {
+        LikeService.new(bob).create("unknown id")
+      }.to raise_error ActiveRecord::RecordNotFound
+    end
+
+    it "fails if the user can't see the post" do
+      expect {
+        LikeService.new(eve).create(post.id)
+      }.to raise_error ActiveRecord::RecordNotFound
+    end
+
+    it "fails if the user already liked the post" do
+      LikeService.new(alice).create(post.id)
+      expect {
+        LikeService.new(alice).create(post.id)
+      }.to raise_error ActiveRecord::RecordInvalid
+    end
+  end
+
+  describe "#destroy" do
+    let(:like) { LikeService.new(bob).create(post.id) }
+
+    it "lets the user destroy their own like" do
+      result = LikeService.new(bob).destroy(like.id)
+      expect(result).to be_truthy
+    end
+
+    it "doesn't let the parent author destroy others likes" do
+      result = LikeService.new(alice).destroy(like.id)
+      expect(result).to be_falsey
+    end
+
+    it "doesn't let someone destroy others likes" do
+      result = LikeService.new(eve).destroy(like.id)
+      expect(result).to be_falsey
+    end
+
+    it "fails if the like doesn't exist" do
+      expect {
+        LikeService.new(bob).destroy("unknown id")
+      }.to raise_error ActiveRecord::RecordNotFound
+    end
+  end
+
+  describe "#find_for_post" do
+    context "with user" do
+      it "returns likes for a public post" do
+        post = alice.post(:status_message, text: "hello", public: true)
+        like = LikeService.new(alice).create(post.id)
+        expect(LikeService.new(eve).find_for_post(post.id)).to include(like)
+      end
+
+      it "returns likes for a visible private post" do
+        like = LikeService.new(alice).create(post.id)
+        expect(LikeService.new(bob).find_for_post(post.id)).to include(like)
+      end
+
+      it "doesn't return likes for a private post the user can not see" do
+        LikeService.new(alice).create(post.id)
+        expect {
+          LikeService.new(eve).find_for_post(post.id)
+        }.to raise_error ActiveRecord::RecordNotFound
+      end
+
+      it "returns the user's like first" do
+        post = alice.post(:status_message, text: "hello", public: true)
+        [alice, bob, eve].map {|user| LikeService.new(user).create(post.id) }
+
+        [alice, bob, eve].each do |user|
+          expect(
+            LikeService.new(user).find_for_post(post.id).first.author.id
+          ).to be user.person.id
+        end
+      end
+    end
+
+    context "without user" do
+      it "returns likes for a public post" do
+        post = alice.post(:status_message, text: "hello", public: true)
+        like = LikeService.new(alice).create(post.id)
+        expect(LikeService.new.find_for_post(post.id)).to include(like)
+      end
+
+      it "doesn't return likes a for private post" do
+        LikeService.new(alice).create(post.id)
+        expect {
+          LikeService.new.find_for_post(post.id)
+        }.to raise_error Diaspora::NonPublic
+      end
+    end
+
+    it "returns all likes of a post" do
+      post = alice.post(:status_message, text: "hello", public: true)
+      likes = [alice, bob, eve].map {|user| LikeService.new(user).create(post.id) }
+
+      expect(LikeService.new.find_for_post(post.id)).to match_array(likes)
+    end
+  end
+end