From d827d6e9ee10fa0906b7b3cfd191e6f9ac5d6b08 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 12 Aug 2010 15:40:58 -0700
Subject: [PATCH] to_sql visitor started

---
 lib/arel.rb                            |  1 +
 lib/arel/nodes/equality.rb             |  5 ++++
 lib/arel/table.rb                      |  2 ++
 lib/arel/visitors/to_sql.rb            | 38 ++++++++++++++++++++++++++
 spec/arel/attributes/attribute_spec.rb | 10 +++++++
 spec/arel/table_spec.rb                |  8 ++++++
 6 files changed, 64 insertions(+)
 create mode 100644 lib/arel/visitors/to_sql.rb

diff --git a/lib/arel.rb b/lib/arel.rb
index 4584584c35..ea9a462d1f 100644
--- a/lib/arel.rb
+++ b/lib/arel.rb
@@ -2,6 +2,7 @@ require 'arel/version'
 require 'arel/table'
 require 'arel/attributes'
 require 'arel/nodes'
+require 'arel/visitors/to_sql'
 
 # below is deprecated
 require 'arel/sql/engine'
diff --git a/lib/arel/nodes/equality.rb b/lib/arel/nodes/equality.rb
index 11383b1d89..d778380054 100644
--- a/lib/arel/nodes/equality.rb
+++ b/lib/arel/nodes/equality.rb
@@ -7,6 +7,11 @@ module Arel
         @left  = left
         @right = right
       end
+
+      def to_sql
+        viz = Visitors::ToSql.new left.relation.engine
+        viz.accept self
+      end
     end
   end
 end
diff --git a/lib/arel/table.rb b/lib/arel/table.rb
index 78b3ea9933..0ab39f134d 100644
--- a/lib/arel/table.rb
+++ b/lib/arel/table.rb
@@ -3,6 +3,8 @@ module Arel
     @engine = nil
     class << self; attr_accessor :engine; end
 
+    attr_reader :name, :engine
+
     def initialize name, engine = Table.engine
       @name   = name
       @engine = engine
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
new file mode 100644
index 0000000000..ba92ca7ef1
--- /dev/null
+++ b/lib/arel/visitors/to_sql.rb
@@ -0,0 +1,38 @@
+module Arel
+  module Visitors
+    class ToSql
+      def initialize engine
+        @engine     = engine
+        @connection = nil
+      end
+
+      def accept object
+        @connection = @engine.connection
+        visit object
+      end
+
+      private
+      def visit_Arel_Nodes_Equality o
+        "#{visit o.left} = #{visit o.right}"
+      end
+
+      def visit_Arel_Attributes_Integer o
+        "#{quote_table_name o.relation.name}.#{quote_column_name o.name}"
+      end
+
+      def visit_Fixnum o; o end
+
+      def visit object
+        send :"visit_#{object.class.name.gsub('::', '_')}", object
+      end
+
+      def quote_table_name name
+        @connection.quote_table_name name
+      end
+
+      def quote_column_name name
+        @connection.quote_column_name name
+      end
+    end
+  end
+end
diff --git a/spec/arel/attributes/attribute_spec.rb b/spec/arel/attributes/attribute_spec.rb
index 5599bb7b51..ef0e0787fa 100644
--- a/spec/arel/attributes/attribute_spec.rb
+++ b/spec/arel/attributes/attribute_spec.rb
@@ -13,5 +13,15 @@ module Arel
         end
       end
     end
+
+    describe 'equality' do
+      describe '#to_sql' do
+        it 'should produce sql' do
+          table = Table.new :users
+          condition = table['id'].eq 1
+          condition.to_sql.should == '"users"."id" = 1'
+        end
+      end
+    end
   end
 end
diff --git a/spec/arel/table_spec.rb b/spec/arel/table_spec.rb
index c52a111489..be153438c4 100644
--- a/spec/arel/table_spec.rb
+++ b/spec/arel/table_spec.rb
@@ -14,6 +14,14 @@ module Arel
       end
     end
 
+    it "should have a name" do
+      @relation.name.should == :users
+    end
+
+    it "should have an engine" do
+      @relation.engine.should == Table.engine
+    end
+
     describe '[]' do
       describe 'when given a', Symbol do
         it "manufactures an attribute if the symbol names an attribute within the relation" do