Refactor image hash loading to use PetService.getPet, not CPN redirs

Previously, the way we loaded the image hash for a given pet was to
navigate to `https://pets.neopets.com/cpn/<pet_name>/1/1.png`, but
*not* follow the redirect, and extract the image hash from the URL
where it redirected us to.

In this change, we refactor to use the AMFPHP RPC `PetService.getPet`
instead. I don't think it had this data last time I looked at it, but
now it does! Much prefer to use an actual RPC than our weird hacky
thing!

(We might also be able to use this call for other stuff, like
auto-labeling gender & mood for pet states, maybe?? That's in this data
too! We used to load petlookups for this, long long ago, before the
petlookup captchas got added.)

app/models/pet.rb

@@ -4,8 +4,9 @@ require 'ostruct'
 class Pet < ApplicationRecord
   NEOPETS_URL_ORIGIN = ENV['NEOPETS_URL_ORIGIN'] || 'https://www.neopets.com'
   GATEWAY_URL = NEOPETS_URL_ORIGIN + '/amfphp/gateway.php'
-  PET_VIEWER = RocketAMFExtensions::RemoteGateway.new(GATEWAY_URL).
-    service('CustomPetService').action('getViewerData')
+  GATEWAY = RocketAMFExtensions::RemoteGateway.new(GATEWAY_URL)
+  CUSTOM_PET_SERVICE = GATEWAY.service('CustomPetService')
+  PET_SERVICE = GATEWAY.service('PetService')
 
   belongs_to :pet_type
 
@@ -123,66 +124,48 @@ class Pet < ApplicationRecord
   # slow sometimes! Since we're on the Falcon server, long timeouts shouldn't
   # slow down the rest of the request queue, like it used to be in the past.
   def self.fetch_viewer_data(name, timeout: 10)
-    begin
-      envelope = PET_VIEWER.request([name, 0]).post(timeout: timeout)
-    rescue RocketAMFExtensions::RemoteGateway::AMFError => e
-      raise DownloadError, e.message
-    rescue RocketAMFExtensions::RemoteGateway::ConnectionError => e
-      raise DownloadError, e.message, e.backtrace
-    end
-    
-    HashWithIndifferentAccess.new(envelope.messages[0].data.body).tap do |data|
-      # When the pet doesn't exist, the service returns an empty pet object.
+    request = CUSTOM_PET_SERVICE.action('getViewerData').request([name])
+    send_amfphp_request(request).tap do |data|
       if data[:custom_pet][:name].blank?
         raise PetNotFound, "Pet #{name.inspect} does not exist"
       end
     end
   end
 
+  def self.fetch_metadata(name, timeout: 10)
+    request = PET_SERVICE.action('getPet').request([name])
+    send_amfphp_request(request).tap do |data|
+      if data[:name].blank?
+        raise PetNotFound, "Pet #{name.inspect} does not exist"
+      end
+    end
+  end
+
   # Given a pet's name, load its image hash, for use in `pets.neopets.com`
   # image URLs. (This corresponds to its current biology and items.)
-  IMAGE_CPN_FORMAT = 'https://pets.neopets.com/cpn/%s/1/1.png';
-  IMAGE_CP_LOCATION_REGEX = %r{^/cp/(.+?)/[0-9]+/[0-9]+\.png$};
-  IMAGE_CPN_ACCEPTABLE_NAME = /^[A-Za-z0-9_]+$/
-  def self.fetch_image_hash(name)
-    return nil unless name.match?(IMAGE_CPN_ACCEPTABLE_NAME)
-
-    cpn_uri = URI.parse sprintf(IMAGE_CPN_FORMAT, CGI.escape(name))
-    begin
-      res = Net::HTTP.get_response(cpn_uri, {
-        'User-Agent' => Rails.configuration.user_agent_for_neopets
-      })
-    rescue Exception => e
-      raise DownloadError, e.message
-    end
-    unless res.is_a? Net::HTTPFound
-      begin
-        res.error!
-      rescue Exception => e
-        Rails.logger.warn "Error loading CPN image at #{cpn_uri}: #{e.message}"
-        return
-      else
-        Rails.logger.warn "Error loading CPN image at #{cpn_uri}. Response: #{res.inspect}"
-        return
-      end
-    end
-    new_url = res['location']
-    new_image_hash = get_hash_from_cp_path(new_url)
-    if new_image_hash
-      Rails.logger.info "Successfully loaded #{cpn_uri}, with image hash #{new_image_hash}"
-      new_image_hash
-    else
-      Rails.logger.warn "CPN image pointed to #{new_url}, which does not match CP image format"
-    end
-  end
-
-  def self.get_hash_from_cp_path(path)
-    match = path.match(IMAGE_CP_LOCATION_REGEX)
-    match ? match[1] : nil
+  def self.fetch_image_hash(name, timeout: 10)
+    metadata = fetch_metadata(name, timeout:)
+    metadata[:hash]
   end
 
   class PetNotFound < RuntimeError;end
   class DownloadError < RuntimeError;end
   class UnexpectedDataFormat < RuntimeError;end
+
+  private
+
+  # Send an AMFPHP request, re-raising errors as `Pet::DownloadError`.
+  # Return the response body as a `HashWithIndifferentAccess`.
+  def self.send_amfphp_request(request, timeout: 10)
+    begin
+      response = request.post(timeout: timeout)
+    rescue RocketAMFExtensions::RemoteGateway::AMFError => e
+      raise DownloadError, e.message
+    rescue RocketAMFExtensions::RemoteGateway::ConnectionError => e
+      raise DownloadError, e.message, e.backtrace
+    end
+
+    HashWithIndifferentAccess.new(response.messages[0].data.body)
+  end
 end