Add nested md5 digest

lib/linguist/md5.rb

@@ -0,0 +1,50 @@
+require 'digest/md5'
+
+module Linguist
+  module MD5
+    # Public: Create deep nested digest of value object.
+    #
+    # Useful for object comparsion.
+    #
+    # obj - Object to digest.
+    #
+    # Returns String hex digest
+    def self.hexdigest(obj)
+      digest = Digest::MD5.new
+      digest_strings(obj).each { |e| digest.update(e) }
+      digest.hexdigest
+    end
+
+    # Internal: Get String representations for digest.
+    #
+    # obj - Object to digest
+    #
+    # Returns an Array of Strings.
+    def self.digest_strings(obj)
+      case obj
+      when String
+        ["#{obj.class}", "#{obj}"]
+      when Symbol
+        ["#{obj.class}", "#{obj}"]
+      when Integer
+        ["#{obj.class}", "#{obj}"]
+      when TrueClass, FalseClass, NilClass
+        ["#{obj.class}"]
+      when Array
+        r = ["#{obj.class}"]
+        obj.each do |e|
+          r.concat(digest_strings(e))
+        end
+        r
+      when Hash
+        r = ["#{obj.class}"]
+        obj.map { |k, v| digest_strings([k, v]) }.sort.each do |e|
+          r.concat(digest_strings(e))
+        end
+        r
+      else
+        raise TypeError, "can't convert #{obj.inspect} into String"
+      end
+    end
+  end
+end