/*    Copyright 2012 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

#include <string>

#include "mongo/bson/bsonobj.h"

namespace mongo {

/**
 * A BSONField holds the name and the type intended for a given BSON element. The
 * class helps documenting and enforcing that field's type.
 *
 * Example usages:
 *
 *     In a header file:
 *     // Determines the types for the fields used in a collection.
 *     static const string MyColl;
 *     struct MyCollFields {
 *         static BSONField<string> name;
 *         static BSONField<bool> draining;
 *         static BSONField<int> count;
 *     };
 *
 *     In a cpp file:
 *     const string MyColl = "my_collection_name";
 *
 *     // determines the names used for the fields
 *     BSONField<string> MyCollFields::name("_id");
 *     BSONField<bool> MyCollFields::draining("draining");
 *     BSONField<int> MyCollFields::count("count");
 *
 *     In an insert:
 *     conn->insert(myColl,
 *                  BSON(MyCollFields::name("id_for_this_doc") <<
 *                       MyCollFields::draining(true) <<
 *                       MyCollFields::count(0)));
 *
 *     In a query:
 *     conn->findOne(myColl, BSON(MyCollFields::count.gt(10))) ;
 *
 */

template <typename T>
class BSONFieldValue {
public:
    BSONFieldValue(const std::string& name, const T& t) : _name(name), _t(t) {}

    const T& value() const {
        return _t;
    }
    const std::string& name() const {
        return _name;
    }

private:
    std::string _name;
    T _t;
};

template <typename T>
class BSONField {
public:
    BSONField(const std::string& name) : _name(name), _defaultSet(false) {}

    BSONField(const std::string& name, const T& defaultVal)
        : _name(name), _default(defaultVal), _defaultSet(true) {}

    BSONFieldValue<T> make(const T& t) const {
        return BSONFieldValue<T>(_name, t);
    }

    BSONFieldValue<T> operator()(const T& t) const {
        return BSONFieldValue<T>(_name, t);
    }

    const std::string& name() const {
        return _name;
    }

    const T& getDefault() const {
        return _default;
    }

    bool hasDefault() const {
        return _defaultSet;
    }

    std::string operator()() const {
        return _name;
    }

    BSONFieldValue<BSONObj> query(const char* q, const T& t) const;

    BSONFieldValue<BSONObj> gt(const T& t) const {
        return query("$gt", t);
    }

    BSONFieldValue<BSONObj> lt(const T& t) const {
        return query("$lt", t);
    }

    BSONFieldValue<BSONObj> ne(const T& t) const {
        return query("$ne", t);
    }

private:
    std::string _name;
    T _default;
    bool _defaultSet;
};

}  // namespace mongo
