From a7f063dc2178b6745cca289c68687cf6939805ca Mon Sep 17 00:00:00 2001
From: Eliot Horowitz <eliot@10gen.com>
Date: Mon, 21 Jun 2010 11:18:33 -0400
Subject: [PATCH] nicer way to create bson      BSONField<int> x("x");     
 BSONObj o = BSON( x(5) );      ASSERT_EQUALS( BSON( "x" << 5 ) , o );

     o = BSON( x.gt(5) );
     ASSERT_EQUALS( BSON( "x" << BSON( "$gt" << 5 ) ) , o );
---
 bson/bsoninlines.h     |  7 ++++++
 bson/bsonobjbuilder.h  | 55 ++++++++++++++++++++++++++++++++++++++++++
 dbtests/jsobjtests.cpp | 28 +++++++++++++++++++++
 3 files changed, 90 insertions(+)

diff --git a/bson/bsoninlines.h b/bson/bsoninlines.h
index 0eeb1fe5cd539..6cd625b4ab074 100644
--- a/bson/bsoninlines.h
+++ b/bson/bsoninlines.h
@@ -572,4 +572,11 @@ namespace mongo {
     }
 
     inline void BSONElement::Val(BSONObj& v) const { v = Obj(); }
+
+    template<typename T>
+    inline BSONFieldValue<BSONObj> BSONField<T>::query( const char * q , const T& t ) const {
+        BSONObjBuilder b;
+        b.append( q , t );
+        return BSONFieldValue<BSONObj>( _name , b.obj() );
+    }
 }
diff --git a/bson/bsonobjbuilder.h b/bson/bsonobjbuilder.h
index a6ae16633deb1..25b7d26f315a2 100644
--- a/bson/bsonobjbuilder.h
+++ b/bson/bsonobjbuilder.h
@@ -33,6 +33,48 @@ namespace mongo {
 #pragma warning( disable : 4355 )
 #endif
 
+    template<typename T>
+    class BSONFieldValue {
+    public:
+        BSONFieldValue( const string& name , const T& t ){
+            _name = name;
+            _t = t;
+        }
+
+        const T& value() const { return _t; }
+        const string& name() const { return _name; }
+
+    private:
+        string _name;
+        T _t;
+    };
+
+    template<typename T>
+    class BSONField {
+    public:
+        BSONField( const string& name , const string& longName="" ) 
+            : _name(name), _longName(longName){}
+        const string& name() const { return _name; }
+        operator string() const { return _name; }
+
+        BSONFieldValue<T> make( const T& t ) const {
+            return BSONFieldValue<T>( _name , t );
+        }
+
+        BSONFieldValue<BSONObj> gt( const T& t ) const { return query( "$gt" , t ); }
+        BSONFieldValue<BSONObj> lt( const T& t ) const { return query( "$lt" , t ); }
+
+        BSONFieldValue<BSONObj> query( const char * q , const T& t ) const;
+        
+        BSONFieldValue<T> operator()( const T& t ) const {
+            return BSONFieldValue<T>( _name , t );
+        }
+        
+    private:
+        string _name;
+        string _longName;
+    };
+
     /** Utility for creating a BSONObj.
         See also the BSON() and BSON_ARRAY() macros.
     */
@@ -527,6 +569,19 @@ namespace mongo {
             return _s << l;
         }
 
+        template<typename T>
+        BSONObjBuilderValueStream& operator<<( const BSONField<T>& f ) {
+            _s.endField( f.name().c_str() );
+            return _s;
+        } 
+
+        template<typename T>
+        BSONObjBuilder& operator<<( const BSONFieldValue<T>& v ) {
+            append( v.name().c_str() , v.value() );
+            return *this;
+        } 
+        
+
         /** @return true if we are using our own bufbuilder, and not an alternate that was given to us in our constructor */
         bool owned() const { return &_b == &_buf; }
 
diff --git a/dbtests/jsobjtests.cpp b/dbtests/jsobjtests.cpp
index aea51d7c841b5..3d1d9c4d973c7 100644
--- a/dbtests/jsobjtests.cpp
+++ b/dbtests/jsobjtests.cpp
@@ -1512,6 +1512,33 @@ namespace JsobjTests {
         }
     };
 
+    class BSONFieldTests {
+    public:
+        void run(){
+            {
+                BSONField<int> x("x");
+                BSONObj o = BSON( x << 5 );
+                ASSERT_EQUALS( BSON( "x" << 5 ) , o );
+            }
+
+            {
+                BSONField<int> x("x");
+                BSONObj o = BSON( x.make(5) );
+                ASSERT_EQUALS( BSON( "x" << 5 ) , o );
+            }
+
+            {
+                BSONField<int> x("x");
+                BSONObj o = BSON( x(5) );
+                ASSERT_EQUALS( BSON( "x" << 5 ) , o );
+
+                o = BSON( x.gt(5) );
+                ASSERT_EQUALS( BSON( "x" << BSON( "$gt" << 5 ) ) , o );
+            }
+
+        }
+    };
+
     class All : public Suite {
     public:
         All() : Suite( "jsobj" ){
@@ -1607,6 +1634,7 @@ namespace JsobjTests {
             add< ElementSetTest >();
             add< EmbeddedNumbers >();
             add< BuilderPartialItearte >();
+            add< BSONFieldTests >();
         }
     } myall;