Add a new endpoint to unreserve a path

This adds a new command to unreserve (destroy) a PathReservation,
provided the reservation exists and matches the given publishing app.

app/commands/unreserve_path.rb

@@ -0,0 +1,30 @@
+module Commands
+  class UnreservePath < BaseCommand
+    def call
+      reservation = lookup_reservation
+      check_is_owned_by_app(reservation)
+      reservation.destroy
+      Success.new(payload)
+    end
+
+  private
+
+    def lookup_reservation
+      PathReservation.find_by!(
+        base_path: payload[:base_path]
+      )
+    rescue ActiveRecord::RecordNotFound
+      msg = "#{payload[:base_path]} is not reserved"
+      raise CommandError.new(code: 404, message: msg)
+    end
+
+    def check_is_owned_by_app(reservation)
+      publishing_app = payload[:publishing_app]
+      base_path = payload[:base_path]
+      return if reservation.publishing_app == publishing_app
+
+      msg = "#{base_path} is reserved by #{reservation.publishing_app}"
+      raise CommandError.new(code: 422, message: msg)
+    end
+  end
+end

app/controllers/path_reservations_controller.rb

@@ -4,6 +4,11 @@ def reserve_path
     render status: response.code, json: response
   end
 
+  def unreserve_path
+    response = Commands::UnreservePath.call(path_item)
+    render status: response.code, json: response
+  end
+
 private
 
   def path_item

config/routes.rb

@@ -9,6 +9,7 @@ def content_id_constraint(request)
     delete "/publish-intent(/*base_path)", to: "publish_intents#destroy"
 
     put "/paths(/*base_path)", to: "path_reservations#reserve_path"
+    delete "/paths(/*base_path)", to: "path_reservations#unreserve_path"
 
     post '/lookup-by-base-path', to: 'lookups#by_base_path'
 

doc/api.md

@@ -29,6 +29,7 @@ message queue for other apps (e.g. `email-alert-service`) to consume.
 - [`POST /v2/links/by-content-id`](#post-v2linksby-content-id)
 - [`POST /lookup-by-base-path`](#post-lookup-by-base-path)
 - [`PUT /paths/:base_path`](#put-pathsbase_path)
+- [`DELETE /paths/:base_path`](#delete-pathsbase_path)
 - [`GET /debug/:content_id`](#get-debugcontent_id)
 
 ### Optimistic locking (`previous_version`)
@@ -718,6 +719,29 @@ Reserves a path for a publishing application. Returns success or failure only.
   publishing_app, and `override_existing` is true, the existing reservation will
   be updated to the supplied publishing_app.
 
+## `DELETE /paths/:base_path`
+
+ [Request/response detail][unreserve-path-pact]
+
+Unreserves a path for a publishing application. Returns success or failure only.
+
+### Path parameters
+
+- `base_path`
+  - Identifies the path that will be unreserved
+
+### JSON parameters:
+
+- `publishing_app` *(required)*
+  - The name of the application making this request, words separated with hyphens.
+
+### State changes
+
+- If no path reservation for the supplied base_path is present, the command will
+  fail.
+- If a path reservation exists for the supplied base_path but a different
+  publishing_app, the command will fail.
+
 ## `GET /debug/:content_id`
 
 Displays debug information for `content_id`.

spec/commands/unreserve_path_spec.rb

@@ -0,0 +1,40 @@
+require "rails_helper"
+
+RSpec.describe Commands::UnreservePath do
+  describe "#call" do
+    context "when the path is owned by the app" do
+      it "successfully removes the reservation" do
+        payload = { publishing_app: "foo", base_path: "/bar" }
+        create(:path_reservation, payload)
+        described_class.call(payload)
+        expect(PathReservation.count).to be_zero
+      end
+    end
+
+    context "when the path is not owned by the app" do
+      it "returns an error" do
+        payload = { base_path: "/bar", publishing_app: "foo" }
+
+        create(:path_reservation,
+               base_path: "/bar",
+               publishing_app: "bar")
+
+        expect { described_class.call(payload) }
+          .to raise_error(
+            CommandError, /is reserved/
+          )
+      end
+    end
+
+    context "when the path has not been reserved" do
+      it "returns an error" do
+        payload = { base_path: "/bar" }
+
+        expect { described_class.call(payload) }
+          .to raise_error(
+            CommandError, /is not reserved/
+          )
+      end
+    end
+  end
+end

spec/controllers/path_reservations_controller_spec.rb

@@ -26,4 +26,31 @@
       end
     end
   end
+
+  describe "unreserve_path" do
+    let(:payload) { { publishing_app: "foo" } }
+
+    context "with a valid path unreservation request" do
+      it "responds successfuly" do
+        create(:path_reservation, base_path: "/bar", publishing_app: "foo")
+        delete :unreserve_path, params: { base_path: "bar" }, body: payload.to_json
+        expect(response.status).to eq(200)
+      end
+    end
+
+    context "with an invalid path unreservation request" do
+      it "responds with status 422" do
+        create(:path_reservation, base_path: "/bar")
+        delete :unreserve_path, params: { base_path: "bar" }, body: payload.to_json
+        expect(response.status).to eq(422)
+      end
+    end
+
+    context "with a non-existant path unreservation request" do
+      it "responds with status 404" do
+        delete :unreserve_path, params: { base_path: "bar" }, body: payload.to_json
+        expect(response.status).to eq(404)
+      end
+    end
+  end
 end

spec/requests/unreserve_path_requests_spec.rb

@@ -0,0 +1,32 @@
+require "rails_helper"
+
+RSpec.describe "DELETE /paths", type: :request do
+  let(:request_body) { payload.to_json }
+
+  def do_request(body: request_body, headers: {})
+    delete request_path, params: body, headers: headers
+  end
+
+  context "with path /vat-rates" do
+    let(:request_path) { "/paths#{base_path}" }
+    let(:payload) { { publishing_app: "publisher" } }
+
+    before do
+      create(:path_reservation,
+             base_path: base_path,
+             publishing_app: "publisher")
+    end
+
+    it "responds successfully" do
+      do_request
+
+      expect(response.status).to eq(200)
+    end
+
+    it "unreserves the path" do
+      expect {
+        do_request
+      }.to change(PathReservation, :count).by(-1)
+    end
+  end
+end