// Copyright (C) 2010  Internet Systems Consortium, Inc. ("ISC")
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

#ifndef __RRSET_CACHE_H
#define __RRSET_CACHE_H

#include <cache/rrset_entry.h>
#include <nsas/hash_table.h>

#include <util/lru_list.h>

using namespace isc::nsas;

namespace isc {
namespace cache {

class RRsetEntry;

/// \brief RRset Cache
/// The object of RRsetCache represented the cache for class-specific
/// RRsets.
///
/// \todo The rrset cache class should provide the interfaces for
///       loading, dumping and resizing.
class RRsetCache{
    ///
    /// \name Constructors and Destructor
    ///
    /// Note: The copy constructor and the assignment operator are intentionally
    /// defined as private to make it uncopyable
    //@{
private:
    RRsetCache(const RRsetCache&);
    RRsetCache& operator=(const RRsetCache&);
public:
    /// \brief Constructor and Destructor
    ///
    /// \param cache_size the size of rrset cache.
    /// \param rrset_class the class of rrset cache.
    RRsetCache(uint32_t cache_size, uint16_t rrset_class);
    virtual ~RRsetCache() {
        rrset_lru_.clear(); // Clear the rrset entries in the list.
    }
    //@}

    /// \brief Look up rrset in cache.
    ///
    /// \param qname The query name to look up
    /// \param qtype The query type 
    /// \return return the shared_ptr of rrset entry if it can be
    /// found in the cache, or else, return NULL.
    RRsetEntryPtr lookup(const isc::dns::Name& qname,
                         const isc::dns::RRType& qtype);

    /// \brief Update RRset Cache
    /// Update the rrset entry in the cache with the new one.
    /// If the rrset has expired or doesn't exist in the cache,
    /// it will be added directly. It may be ingored if the new
    /// rrset is not more authoritative than the old rrset in cache.
    ///
    /// \param rrset The new rrset used to update cache.
    /// \param level trustworthiness of the rrset.
    /// \return return the rrset entry in the cache, it may be the
    /// new added rrset entry or existed one if it is not replaced.
    RRsetEntryPtr update(const isc::dns::RRset& rrset,
                         const RRsetTrustLevel& level);

    /// \short Protected memebers, so they can be accessed by tests.
protected:
    uint16_t class_; // The class of the rrset cache.
    isc::nsas::HashTable<RRsetEntry> rrset_table_;
    isc::util::LruList<RRsetEntry> rrset_lru_;
};

typedef boost::shared_ptr<RRsetCache> RRsetCachePtr;
typedef boost::shared_ptr<const RRsetCache> ConstRRsetCachePtr;

} // namespace cache
} // namespace isc

#endif // __RRSET_CACHE_H