Add Danbooru::URL class.

Introduce a Danbooru::URL class for dealing with URLs. This is a wrapper
around Addressable::URI that adds some additional helper methods. Most
significantly, the `parse` method only allows valid http/https URLs, and
it returns nil instead of raising an exception when the URL is invalid.

app/logical/danbooru/url.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module Danbooru
+  class URL
+    class Error < StandardError; end
+
+    attr_reader :original_url, :url
+    delegate_missing_to :url
+
+    # Parse a string into an URL, or raise an exception if the string is not a valid HTTPS or HTTPS URL.
+    #
+    # @param string [String]
+    # @return [Danbooru::URL]
+    def initialize(string)
+      @original_url = string
+      @url = Addressable::URI.heuristic_parse(string).display_uri
+      @url.path = nil if @url.path == "/"
+      raise Error, "#{string} is not an http:// URL" if !@url.normalized_scheme.in?(["http", "https"])
+    rescue Addressable::URI::InvalidURIError => e
+      raise Error, e
+    end
+
+    # Parse a string into an URL, or return nil if the string is not a valid HTTP or HTTPS URL.
+    #
+    # @param string [String]
+    # @return [Danbooru::URL]
+    def self.parse(string)
+      new(string)
+    rescue StandardError => e
+      nil
+    end
+
+    # @return [String] the URL in normalized form
+    def to_s
+      url.to_str
+    end
+
+    # @return [Array<String>] the URL's path split into segments
+    def path_segments
+      path.split("/").compact_blank
+    end
+
+    # @return [Hash] the URL's query parameters
+    def params
+      url.query_values.with_indifferent_access
+    end
+  end
+end

app/logical/sources/strategies/base.rb

@@ -46,8 +46,8 @@ module Sources
         @referer_url = referer_url&.to_s
         @urls = [@url, @referer_url].select(&:present?)
 
-        @parsed_url = Addressable::URI.heuristic_parse(url) rescue nil
-        @parsed_referer = Addressable::URI.heuristic_parse(referer_url) rescue nil
+        @parsed_url = Danbooru::URL.parse(url)
+        @parsed_referer = Danbooru::URL.parse(referer_url)
         @parsed_urls = [parsed_url, parsed_referer].select(&:present?)
       end
 
@@ -65,7 +65,7 @@ module Sources
       end
 
       def site_name
-        host = Addressable::URI.heuristic_parse(url)&.host
+        host = parsed_url&.host
 
         # XXX should go in dedicated strategies.
         case host
@@ -134,8 +134,6 @@ module Sources
         else
           host
         end
-      rescue Addressable::URI::InvalidURIError
-        nil
       end
 
       # Whatever <tt>url</tt> is, this method should return the direct links

app/models/post.rb

@@ -314,10 +314,7 @@ class Post < ApplicationRecord
     def source_domain
       return "" unless source =~ %r{\Ahttps?://}i
 
-      url = Addressable::URI.parse(normalized_source)
-      url.domain
-    rescue StandardError
-      ""
+      Danbooru::URL.parse(normalized_source)&.domain.to_s
     end
   end
 

app/models/upload.rb

@@ -70,8 +70,7 @@ class Upload < ApplicationRecord
     class_methods do
       # percent-encode unicode characters in the URL
       def normalize_source(url)
-        return nil if url.nil?
-        Addressable::URI.normalized_encode(url)
+        Danbooru::URL.parse(url)&.to_s.presence || url
       end
     end
   end