major refactoring of post sets and pagination, incomplete

app/logical/post_sets/base.rb

@@ -1,45 +1,78 @@
+# A PostSet represents a paginated slice of posts. It is used in conjunction
+# with the helpers to render the paginator.
+#
+# Usage:
+#
+# @post_set = PostSets::Base.new(params)
+# @post_set.extend(PostSets::Sequential)
+# @post_set.extend(PostSets::Post)
+
 module PostSets
   class Base
-    attr_accessor :page, :before_id, :count, :posts
-  
-    def initialize(options = {})
-      @page = options[:page] ? options[:page].to_i : 1
-      @before_id = options[:before_id]
-      load_posts
+    attr_reader :params, :posts
+    delegate :to_xml, :to_json, :to => :posts
+    
+    def initialize(params)
+      @params = params
     end
     
-    def has_wiki?
-      false
-    end
-  
-    def use_sequential_paginator?
-      !use_numbered_paginator?
-    end
-  
-    def use_numbered_paginator?
-      before_id.nil?
-    end
-  
-    def load_posts
+    # Should a return a paginated array of posts. This means it should have
+    # at most <limit> elements.
+    def posts
       raise NotImplementedError
     end
-  
-    def to_xml
-      posts.to_xml
+    
+    # Does this post set have a valid wiki page representation?
+    def has_wiki?
+      raise NotImplementedError
     end
-  
-    def to_json
-      posts.to_json
+    
+    # Should return an array of strings representing the tags.
+    def tags
+      raise NotImplementedError
     end
-  
+
+    # Given an ActiveRelation object, perform the necessary pagination to
+    # extract at most <limit> elements. Should return an array.
+    def slice(relation)
+      raise NotImplementedError
+    end
+    
+    # For cases where we're not relying on the default pagination 
+    # implementation (for example, if the ids are cached in a string)
+    # then pass in the offset/before_id/after_id parameters here.
+    def pagination_options
+      raise NotImplementedError
+    end
+    
+    # This method should throw an exception if for whatever reason the query
+    # is invalid or forbidden.
+    def validate
+    end
+    
+    # Clear out any memoized instance variables.
+    def reload
+      @posts = nil
+      @presenter = nil
+      @tag_string = nil
+    end
+
+    def tag_string
+      @tag_string ||= tags.join(" ")
+    end
+    
+    def is_first_page?
+      raise NotImplementedError
+    end
+    
+    def is_last_page?
+      posts.size == 0
+    end
+    
     def presenter
       @presenter ||= PostSetPresenter.new(self)
     end
     
-    def offset
-      ((page < 1) ? 0 : (page - 1)) * count
-    end
-
     def limit
       Danbooru.config.posts_per_page
     end