Add basic OEmbed provider API, fix #247

app/controllers/api/oembed_controller.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+class Api::OembedController < ApiController
+  respond_to :json
+
+  def show
+    @stream_entry = stream_entry_from_url(params[:url])
+    @width        = [300, params[:maxwidth].to_i].min
+    @height       = [200, params[:maxheight].to_i].min
+  end
+
+  private
+
+  def stream_entry_from_url(url)
+    params = Rails.application.routes.recognize_path(url)
+
+    raise ActiveRecord::NotFound unless params[:controller] == 'stream_entries' && params[:action] == 'show'
+
+    StreamEntry.find(params[:id])
+  end
+end