From 8295fa578377f4491dbec486d18cd13b944216ed Mon Sep 17 00:00:00 2001
From: Yorick Peterse <yorickpeterse@gmail.com>
Date: Tue, 26 Aug 2014 18:14:44 +0200
Subject: [PATCH] Support for the XPath translate() function.

---
 lib/oga/xpath/evaluator.rb                    | 29 ++++++++++++++++
 .../xpath/evaluator/calls/translate_spec.rb   | 34 +++++++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 spec/oga/xpath/evaluator/calls/translate_spec.rb

diff --git a/lib/oga/xpath/evaluator.rb b/lib/oga/xpath/evaluator.rb
index 1ca2d28..4231341 100644
--- a/lib/oga/xpath/evaluator.rb
+++ b/lib/oga/xpath/evaluator.rb
@@ -1002,6 +1002,35 @@ module Oga
         return str.strip.gsub(/\s+/, ' ')
       end
 
+      ##
+      # Processes the `translate()` function call.
+      #
+      # This function takes the string of the 1st argument and replaces all
+      # characters of the 2nd argument with those specified in the 3rd argument.
+      #
+      # @example
+      #  translate("bar", "abc", "ABC") # => "BAr"
+      #
+      # @param [Oga::XML::NodeSet] context
+      # @param [Oga::XPath::Node] input
+      # @param [Oga::XPath::Node] find
+      # @param [Oga::XPath::Node] replace
+      # @return [String]
+      #
+      def on_call_translate(context, input, find, replace)
+        input_str     = on_call_string(context, input)
+        find_chars    = on_call_string(context, find).chars
+        replace_chars = on_call_string(context, replace).chars
+        replaced      = input_str
+
+        find_chars.each_with_index do |char, index|
+          replace_with = replace_chars[index] ? replace_chars[index] : ''
+          replaced     = replaced.gsub(char, replace_with)
+        end
+
+        return replaced
+      end
+
       ##
       # Processes an `(int)` node.
       #
diff --git a/spec/oga/xpath/evaluator/calls/translate_spec.rb b/spec/oga/xpath/evaluator/calls/translate_spec.rb
new file mode 100644
index 0000000..bdc1491
--- /dev/null
+++ b/spec/oga/xpath/evaluator/calls/translate_spec.rb
@@ -0,0 +1,34 @@
+require 'spec_helper'
+
+describe Oga::XPath::Evaluator do
+  context 'translate() function' do
+    before do
+      @document  = parse('<root><a>bar</a><b>abc</b><c>ABC</c></root>')
+      @evaluator = described_class.new(@document)
+    end
+
+    example 'translate a string using all string literals' do
+      @evaluator.evaluate('translate("bar", "abc", "ABC")').should == 'BAr'
+    end
+
+    example "remove characters that don't occur in the replacement string" do
+      @evaluator.evaluate('translate("-aaa-", "abc-", "ABC")').should == 'AAA'
+    end
+
+    example 'use the first character occurence in the search string' do
+      @evaluator.evaluate('translate("ab", "aba", "123")').should == '12'
+    end
+
+    example 'ignore excess characters in the replacement string' do
+      @evaluator.evaluate('translate("abc", "abc", "123456")').should == '123'
+    end
+
+    example 'translate a node set string using string literals' do
+      @evaluator.evaluate('translate(root/a, "abc", "ABC")').should == 'BAr'
+    end
+
+    example 'translate a node set string using other node set strings' do
+      @evaluator.evaluate('translate(root/a, root/b, root/c)').should == 'BAr'
+    end
+  end
+end