FIX: If HEAD is not supported, try GET. Also set cookies

lib/final_destination.rb

@@ -7,6 +7,7 @@ require 'rate_limiter'
 class FinalDestination
 
   attr_reader :status
+  attr_reader :cookie
 
   def initialize(url, opts=nil)
     @uri = URI(url) rescue nil
@@ -21,6 +22,11 @@ class FinalDestination
     end
     @limit = @opts[:max_redirects]
     @status = :ready
+    @cookie = nil
+  end
+
+  def self.connection_timeout
+    20
   end
 
   def redirected?
@@ -28,9 +34,27 @@ class FinalDestination
   end
 
   def request_headers
-    { "User-Agent" => "Mozilla/5.0 (Windows NT 6.2; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
+    result = {
+      "User-Agent" => "Mozilla/5.0 (Windows NT 6.2; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
       "Accept" => "text/html",
-      "Host" => @uri.hostname }
+      "Host" => @uri.hostname
+    }
+
+    result['cookie'] = @cookie if @cookie
+
+    result
+  end
+
+  def small_get(headers)
+    Net::HTTP.start(@uri.host, @uri.port, use_ssl: @uri.is_a?(URI::HTTPS)) do |http|
+      http.open_timeout = FinalDestination.connection_timeout
+      http.read_timeout = FinalDestination.connection_timeout
+
+      request = Net::HTTP::Get.new(@uri.request_uri, headers)
+      http.request(request) do |response|
+        return response
+      end
+    end
   end
 
   def resolve
@@ -41,17 +65,41 @@ class FinalDestination
 
     return nil unless validate_uri
     headers = request_headers
-    head = Excon.head(@uri.to_s, read_timeout: 20, headers: headers)
+    response = Excon.head(
+      @uri.to_s,
+      read_timeout: FinalDestination.connection_timeout,
+      headers: headers
+    )
 
-    # If the site does not allow HEAD, just try the url
-    return @uri if head.status == 405
+    location = nil
+    case response.status
+    when 200
+      @status = :resolved
+      return @uri
+    when 405, 501
+      get_response = small_get(headers)
 
-    if head.status == 200
+      if get_response.code.to_i == 200
         @status = :resolved
         return @uri
       end
 
-    location = FinalDestination.header_for(head, 'location')
+      if cookie_val = get_response.get_fields('set-cookie')
+        @cookie = cookie_val.join
+      end
+
+      if location_val = get_response.get_fields('location')
+        location = location_val.join
+      end
+    else
+      response.headers.each do |k, v|
+        case k.downcase
+        when 'set-cookie' then @cookie = v
+        when 'location' then location = v
+        end
+      end
+    end
+
     if location
       location = "#{@uri.scheme}://#{@uri.host}#{location}" if location[0] == "/"
       @uri = URI(location) rescue nil
@@ -127,11 +175,4 @@ class FinalDestination
     IPSocket::getaddress(host)
   end
 
-  def self.header_for(head, name)
-    header = head.headers.detect do |k, _|
-      name == k.downcase
-    end
-    header[1] if header
-  end
-
 end

spec/components/final_destination_spec.rb

@@ -120,6 +120,45 @@ describe FinalDestination do
         expect(final.status).to eq(:invalid_address)
       end
     end
+
+    context "HEAD not supported" do
+      before do
+        stub_request(:get, 'https://eviltrout.com').to_return(
+          status: 301,
+          headers: {
+            "Location" => 'https://discourse.org',
+            'Set-Cookie' => 'evil=trout'
+          }
+        )
+        stub_request(:head, 'https://discourse.org').to_return(status: 200)
+      end
+
+      context "when the status code is 405" do
+        before do
+          stub_request(:head, 'https://eviltrout.com').to_return(status: 405)
+        end
+
+        it "will try a GET" do
+          final = FinalDestination.new('https://eviltrout.com', opts)
+          expect(final.resolve.to_s).to eq('https://discourse.org')
+          expect(final.status).to eq(:resolved)
+          expect(final.cookie).to eq('evil=trout')
+        end
+      end
+
+      context "when the status code is 501" do
+        before do
+          stub_request(:head, 'https://eviltrout.com').to_return(status: 501)
+        end
+
+        it "will try a GET" do
+          final = FinalDestination.new('https://eviltrout.com', opts)
+          expect(final.resolve.to_s).to eq('https://discourse.org')
+          expect(final.status).to eq(:resolved)
+          expect(final.cookie).to eq('evil=trout')
+        end
+      end
+    end
   end
 
   describe '.validate_uri' do