Fixed file path detection bug in build method polymorphism

(when string was recognised as path cause of  "xml", "yml", etc. content in it)
Refactored file detection duplication in few places
Fixed xml file format detection (f variable assigned but never used)
Deleted some trailing spaces in the refactored file

lib/treat/entities/entity/buildable.rb

@@ -17,6 +17,9 @@ module Treat::Entities::Entity::Buildable
   EmailRegexp = /.+\@.+\..+/
   Enclitics = %w['ll 'm 're 's 't 've 'nt]
 
+  # Accepted formats of serialized files
+  AcceptedFormats = ['.xml', '.yml', '.yaml', '.mongo']
+
   # Reserved folder names
   Reserved = ['.index']
 
@@ -24,7 +27,7 @@ module Treat::Entities::Entity::Buildable
   # a string, numeric,folder, or file name
   # representing a raw or serialized file).
   def build(*args)
-    
+
     # This probably needs some doc.
     if args.size == 0
       file_or_value = ''
@@ -46,9 +49,7 @@ module Treat::Entities::Entity::Buildable
       from_array(file_or_value)
     elsif file_or_value.is_a?(Hash)
       from_db(file_or_value)
-    elsif self == Treat::Entities::Document ||
-      (fv.index('.yml') || fv.index('.yaml') ||
-      fv.index('.xml'))
+    elsif self == Treat::Entities::Document || (is_serialized_file?(fv))
       if fv =~ UriRegexp
         from_url(fv)
       else
@@ -94,7 +95,7 @@ module Treat::Entities::Entity::Buildable
     end
     e
   end
-  
+
   # Build a document from an array
   # of builders.
   def from_array(array)
@@ -118,7 +119,7 @@ module Treat::Entities::Entity::Buildable
     begin
       folder = Treat.paths.files
       if folder[-1] == '/'
-        folder = folder[0..-2] 
+        folder = folder[0..-2]
       end
       f = Schiphol.download(url,
       download_folder: folder,
@@ -178,15 +179,15 @@ module Treat::Entities::Entity::Buildable
 
     c = Treat::Entities::Collection.new(folder)
     folder += '/' unless folder[-1] == '/'
-    
+
     if !FileTest.directory?(folder)
       FileUtils.mkdir(folder)
     end
-    
+
     c.set :folder, folder
     i = folder + '/.index'
     c.set :index, i if FileTest.directory?(i)
-    
+
     Dir[folder + '*'].each do |f|
       if FileTest.directory?(f)
         c2 = Treat::Entities::Collection.
@@ -197,7 +198,7 @@ module Treat::Entities::Entity::Buildable
         from_file(f), false)
       end
     end
-    
+
     return c
 
   end
@@ -205,9 +206,7 @@ module Treat::Entities::Entity::Buildable
   # Build a document from a raw or serialized file.
   def from_file(file,def_fmt=nil)
 
-    if file.index('.yml') ||
-      file.index('.yaml') ||
-      file.index('.xml')
+    if is_serialized_file?(file)
       from_serialized_file(file)
     else
       fmt = Treat::Workers::Formatters::Readers::Autoselect.detect_format(file,def_fmt)
@@ -240,7 +239,7 @@ module Treat::Entities::Entity::Buildable
 
   # Build an entity from a serialized file.
   def from_serialized_file(file)
-    
+
     unless File.readable?(file)
       raise Treat::Exception,
       "Path '#{file}' does not "+
@@ -249,11 +248,11 @@ module Treat::Entities::Entity::Buildable
     doc = Treat::Entities::Document.new
     doc.set :file, file
     format = nil
-    if file.index('yml') || 
-      file.index('yaml')
+    if File.extname(file) == '.yml' ||
+       File.extname(file) == '.yaml'
       format = :yaml
-    elsif file.index('xml')
-      f = :xml
+    elsif File.extname(file) == '.xml'
+      format = :xml
     else
       raise Treat::Exception,
       "Unreadable serialized format for #{file}."
@@ -261,7 +260,10 @@ module Treat::Entities::Entity::Buildable
     doc.unserialize(format)
     doc.children[0].set_as_root!              # Fix this
     doc.children[0]
+  end
 
+  def is_serialized_file?(path_to_check)
+    (AcceptedFormats.include? File.extname(path_to_check)) && (File.file?(path_to_check))
   end
 
   def from_db(hash)
@@ -285,7 +287,7 @@ module Treat::Entities::Entity::Buildable
       if folder[-1] == '/'
         folder = folder[0..-2]
       end
-      
+
       now = Time.now.to_f
       doc_file = folder+ "/#{now}.txt"
       string.force_encoding('UTF-8')
@@ -383,7 +385,7 @@ module Treat::Entities::Entity::Buildable
     end
 
   end
-  
+
   def create_collection(fv)
     FileUtils.mkdir(fv)
     Treat::Entities::Collection.new(fv)