post queries: add methods for normalizing queries.

app/logical/post_query.rb

@@ -3,14 +3,40 @@
 class PostQuery
   extend Memoist
 
-  attr_reader :search, :parser, :builder, :ast
-  delegate :tag?, :metatag?, :wildcard?, :metatags, :wildcards, :tag_names, :metatags, to: :ast
+  private attr_reader :current_user, :tag_limit, :safe_mode, :hide_deleted_posts, :builder
 
-  def initialize(search, current_user: User.anonymous, tag_limit: nil, safe_mode: false, hide_deleted_posts: false)
-    @search = search
-    @parser = Parser.new(search)
-    @builder = PostQueryBuilder.new(search, current_user, tag_limit: tag_limit, safe_mode: safe_mode, hide_deleted_posts: hide_deleted_posts)
-    @ast = parser.parse.simplify
+  delegate :tag?, :metatag?, :wildcard?, :metatags, :wildcards, :tag_names, :metatags, to: :ast
+  alias_method :safe_mode?, :safe_mode
+  alias_method :hide_deleted_posts?, :hide_deleted_posts
+
+  def initialize(search_or_ast, current_user: User.anonymous, tag_limit: nil, safe_mode: false, hide_deleted_posts: false)
+    if search_or_ast.is_a?(AST)
+      @ast = search_or_ast
+    else
+      @search = search_or_ast.to_s
+    end
+
+    @current_user = current_user
+    @tag_limit = tag_limit
+    @safe_mode = safe_mode
+    @hide_deleted_posts = hide_deleted_posts
+  end
+
+  # Build a new PostQuery from the given AST and the current settings.
+  def build(ast)
+    PostQuery.new(ast, current_user: current_user, tag_limit: tag_limit, safe_mode: safe_mode, hide_deleted_posts: hide_deleted_posts)
+  end
+
+  def builder
+    @builder ||= PostQueryBuilder.new(search, current_user, tag_limit: tag_limit, safe_mode: safe_mode, hide_deleted_posts: hide_deleted_posts)
+  end
+
+  def search
+    @search ||= ast.to_infix
+  end
+
+  def ast
+    @ast ||= Parser.parse(search)
   end
 
   def fast_count(...)
@@ -47,15 +73,47 @@ class PostQuery
     select_metatags(*names).first&.value
   end
 
-  # Return a new query AST, with aliased tags replaced with real tags.
-  def replace_aliases
-    ast.replace_tags(aliases)
+  # Return a new PostQuery with aliases replaced, implicit metatags added, and the query converted to conjunctive normal form.
+  def normalize
+    replace_aliases.with_implicit_metatags.to_cnf
   end
 
-  # A hash mapping aliased tag names to real tag names.
+  # Return a new PostQuery with aliases replaced.
+  def replace_aliases
+    return self if aliases.empty?
+    build(ast.replace_tags(aliases))
+  end
+
+  # Return a new PostQuery with implicit metatags (rating:safe and -status:deleted) added.
+  def with_implicit_metatags
+    return self if implicit_metatags.empty?
+    build(AST.new(:and, [ast, *implicit_metatags]))
+  end
+
+  # Return a new PostQuery converted to conjunctive normal form.
+  def to_cnf
+    build(ast.to_cnf)
+  end
+
+  # Return a hash mapping aliased tag names to real tag names.
   def aliases
     TagAlias.aliases_for(tag_names)
   end
 
-  memoize :tags, :aliases
+  # Implicit metatags are metatags added by the user's account settings. rating:s is implicit
+  # under safe mode. -status:deleted is implicit when the "hide deleted posts" setting is on.
+  def implicit_metatags
+    metatags = []
+    metatags << AST.metatag("rating", "s") if safe_mode?
+    metatags << -AST.metatag("status", "deleted") if hide_deleted?
+    metatags
+  end
+
+  # XXX unify with PostSets::Post#show_deleted?
+  def hide_deleted?
+    has_status_metatag = select_metatags(:status).any? { |metatag| metatag.value.downcase.in?(%w[deleted active any all unmoderated modqueue appealed]) }
+    hide_deleted_posts? && !has_status_metatag
+  end
+
+  memoize :tags, :normalize, :replace_aliases, :with_implicit_metatags, :to_cnf, :aliases, :implicit_metatags, :hide_deleted?
 end

app/logical/post_query/ast.rb

@@ -54,9 +54,37 @@ class PostQuery
       @args = args
     end
 
-    # Create an AST node.
-    def node(type, *args)
-      AST.new(type, args)
+    concerning :ConstructorMethods do
+      class_methods do
+        def tag(name)
+          AST.new(:tag, [name])
+        end
+
+        def metatag(name, value)
+          AST.new(:metatag, [name, value])
+        end
+      end
+
+      def &(other)
+        AST.new(:and, [self, other])
+      end
+
+      def |(other)
+        AST.new(:or, [self, other])
+      end
+
+      def ~
+        AST.new(:opt, [self])
+      end
+
+      def -@
+        AST.new(:not, [self])
+      end
+
+      # Create an AST node.
+      def node(type, *args)
+        AST.new(type, args)
+      end
     end
 
     concerning :SimplificationMethods do