Add `from:` query operator to search syntax (#16526)

* Add 'by:userhandle' parameter to search api

* Use search syntax for "by" prefix

* Codeclimate

* Use 'from' instead of 'by'

app/lib/search_query_transformer.rb

@@ -2,19 +2,21 @@
 
 class SearchQueryTransformer < Parslet::Transform
   class Query
-    attr_reader :should_clauses, :must_not_clauses, :must_clauses
+    attr_reader :should_clauses, :must_not_clauses, :must_clauses, :filter_clauses
 
     def initialize(clauses)
       grouped = clauses.chunk(&:operator).to_h
       @should_clauses = grouped.fetch(:should, [])
       @must_not_clauses = grouped.fetch(:must_not, [])
       @must_clauses = grouped.fetch(:must, [])
+      @filter_clauses = grouped.fetch(:filter, [])
     end
 
     def apply(search)
       should_clauses.each { |clause| search = search.query.should(clause_to_query(clause)) }
       must_clauses.each { |clause| search = search.query.must(clause_to_query(clause)) }
       must_not_clauses.each { |clause| search = search.query.must_not(clause_to_query(clause)) }
+      filter_clauses.each { |clause| search = search.filter(**clause_to_filter(clause)) }
       search.query.minimum_should_match(1)
     end
 
@@ -30,6 +32,15 @@ class SearchQueryTransformer < Parslet::Transform
         raise "Unexpected clause type: #{clause}"
       end
     end
+
+    def clause_to_filter(clause)
+      case clause
+      when PrefixClause
+        { term: { clause.filter => clause.term } }
+      else
+        raise "Unexpected clause type: #{clause}"
+      end
+    end
   end
 
   class Operator
@@ -69,11 +80,33 @@ class SearchQueryTransformer < Parslet::Transform
     end
   end
 
+  class PrefixClause
+    attr_reader :filter, :operator, :term
+
+    def initialize(prefix, term)
+      @operator = :filter
+      case prefix
+      when 'from'
+        @filter = :account_id
+        username, domain = term.split('@')
+        account = Account.find_remote(username, domain)
+
+        raise "Account not found: #{term}" unless account
+
+        @term = account.id
+      else
+        raise "Unknown prefix: #{prefix}"
+      end
+    end
+  end
+
   rule(clause: subtree(:clause)) do
     prefix   = clause[:prefix][:term].to_s if clause[:prefix]
     operator = clause[:operator]&.to_s
 
-    if clause[:term]
+    if clause[:prefix]
+      PrefixClause.new(prefix, clause[:term].to_s)
+    elsif clause[:term]
       TermClause.new(prefix, operator, clause[:term].to_s)
     elsif clause[:shortcode]
       TermClause.new(prefix, operator, ":#{clause[:term]}:")