/* -*-c++-*- */
/* osgEarth - Geospatial SDK for OpenSceneGraph
* Copyright 2020 Pelican Mapping
* http://osgearth.org
*
* osgEarth is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program.  If not, see <http://www.gnu.org/licenses/>
*/

#ifndef OSGEARTH_CACHE_H
#define OSGEARTH_CACHE_H 1

#include <osgEarth/Common>
#include <osgEarth/CacheBin>
#include <osgEarth/CachePolicy>
#include <osgEarth/Config>
#include <osgEarth/TileKey>
#include <osgEarth/Containers>
#include <sys/types.h>
#include <map>

// environment variables
#define OSGEARTH_ENV_CACHE_DRIVER  "OSGEARTH_CACHE_DRIVER"
#define OSGEARTH_ENV_CACHE_PATH    "OSGEARTH_CACHE_PATH"
#define OSGEARTH_ENV_CACHE_ONLY    "OSGEARTH_CACHE_ONLY"
#define OSGEARTH_ENV_DEFAULT_COMPRESSOR "OSGEARTH_DEFAULT_COMPRESSOR"

#define OSGEARTH_ENV_NO_CACHE      "OSGEARTH_NO_CACHE"
#define OSGEARTH_ENV_CACHE_MAX_AGE "OSGEARTH_CACHE_MAX_AGE"

namespace osgEarth
{
    class Cache;
    class CachePolicy;
}

namespace osgEarth { namespace Util
{
#define DEFAULT_BIN_ID ""

    /**
     * CacheSettings is an object stored in the osgDB::Options structure that
     * propagates throughout the osgEarth data model. It represents a Cache state
     * that includes the actual Cache, the active CacheBin, and a policy.
     */
    class OSGEARTH_EXPORT CacheSettings : public osg::Object
    {
    public:
        META_Object(osgEarth,CacheSettings);

        typedef UID ID;

        typedef std::string BinID;

        /** default constructor */
        CacheSettings();

        /** copier */
        CacheSettings(const CacheSettings& rhs, const osg::CopyOp& copy =osg::CopyOp::SHALLOW_COPY);

        /** Whether this object support an active cache. */
        bool isCacheEnabled() const;
        bool isCacheDisabled() const { return !isCacheEnabled(); }

        /** Cache used by these settings */
        Cache* getCache() const { return _cache.get(); }
        void setCache(Cache* cache) { _cache = cache; }

        /** Sets the active cache bin to use under these settings. */
        void setCacheBin(CacheBin* bin) { _activeBin = bin; }
        CacheBin* getCacheBin() { return _activeBin.get(); }

        /** The caching policy in effect for all bins; this starts out the same as
          * defaultCachePolicy() but you can change it. */
        optional<CachePolicy>& cachePolicy() { return _policy; }
        const optional<CachePolicy>& cachePolicy() const { return _policy; }

        /** Integrates an outside cache policy with the one in these settings. This method
          * also takes care of global (registry) override policy. */
        void integrateCachePolicy(const optional<CachePolicy>& policy);

        /** Integrates an outside cache policy with the one in these settings. This method
        * also takes care of global (registry) override policy. */
        void integrateCachePolicy(const CachePolicy& policy);

        /** Extracts the settings from a read-options structure. */
        static CacheSettings* get(const osgDB::Options* readOptions);

        /** Stores this instance in an Options data container. Extract using get(). */
        void store(osgDB::Options* readOptions);

        /** for debugging */
        std::string toString() const;

    protected:
        virtual ~CacheSettings() { }

        osg::ref_ptr<Cache>      _cache;
        osg::ref_ptr<CacheBin>   _activeBin;
        optional<CachePolicy>    _policy;
    };
} }

//--------------------------------------------------------------------

namespace osgEarth
{
    /**
     * Base class for Cache options.
     */
    class OSGEARTH_EXPORT CacheOptions : public DriverConfigOptions
    {
    public:
        CacheOptions( const ConfigOptions& options =ConfigOptions() )
            : DriverConfigOptions( options )
        {
            fromConfig( _conf );
        }
        
        optional<bool>& enableNodeCaching() { return _enableNodeCaching; }
        const optional<bool>& enableNodeCaching() const { return _enableNodeCaching; }

        /** dtor */
        virtual ~CacheOptions();

    public:
        virtual Config getConfig() const;

        virtual void mergeConfig( const Config& conf ) {
            ConfigOptions::mergeConfig( conf );
            fromConfig( conf );
        }

    private:
        void fromConfig(const Config& conf);
        optional<bool> _enableNodeCaching;
    };
}

OSGEARTH_SPECIALIZE_CONFIG(osgEarth::CacheOptions);

//--------------------------------------------------------------------

namespace osgEarth
{
    using ThreadSafeCacheBinMap = PerObjectRefMap<std::string, CacheBin>;

    /**
     * Cache is a container for local storage of keyed data elements.
     */
    class OSGEARTH_EXPORT Cache : public osg::Object
    {
    protected:
        Cache( const CacheOptions& options =CacheOptions() );
        Cache( const Cache& rhs, const osg::CopyOp& op =osg::CopyOp::DEEP_COPY_ALL );

        /** dtor */
        virtual ~Cache();

    public:
        /**
         * Whether this cache is valid and available for use
         */
        const Status& getStatus() const { return _status; }

        /**
         * Gets a caching bin within this cache.
         * @param name Name of the caching bin
         * @param rw   Read/write driver for the bin (can be null)
         */
        CacheBin* getBin( const std::string& name );

        /**
         * Gets the default caching bin within this cache. This may or may not
         * be supported by the implementation, so be sure to check the result
         * before using it.
         */
        virtual CacheBin* getOrCreateDefaultBin() { return _defaultBin.get(); }

        /**
         * Creates (and returns a pointer to) a new Cache Bin, or returns an
         * already-existing one with that ID.
         * @param binID Name of the new bin
         */
        virtual CacheBin* addBin(const std::string& binID) =0;

        /**
         * Removes a cache bin from the cache.
         * @param bin Bin to remove.
         */
        virtual void removeBin( CacheBin* bin );

        /**
         * Gets an Options structure representing this cache's configuration.
         */
        const CacheOptions& getCacheOptions() const { return _options; }

        /**
         * Gets the (approximate) size of the cache on disk, or zero if
         * the size cannot be calculated
         */
        virtual off_t getApproximateSize() const { return 0; }

        /**
         * Compacts the cache (if applicable).
         */
        virtual bool compact() { return false; }

        /**
         * Removes all records in the cache (if possible). This could take
         * some time to complete.
         */
        virtual bool clear() { return false; }
        
        //! Set the number of background threads to use. You must call this 
        //! prior to addBin().
        virtual void setNumThreads(unsigned num) { }

        //! Make a legal cache key with an optional prefix
        static std::string makeCacheKey(const std::string& input, const std::string& prefix="");

    protected:
        Status _status;
        CacheOptions           _options;
        ThreadSafeCacheBinMap  _bins;
        osg::ref_ptr<CacheBin> _defaultBin;
    };

//----------------------------------------------------------------------

    namespace Util
    {
        /**
         * Base class for a cache driver plugin.
         */
        class OSGEARTH_EXPORT CacheDriver : public osgDB::ReaderWriter
        {
        public:
            const CacheOptions& getCacheOptions( const osgDB::ReaderWriter::Options* options ) const;

            /** dtor */
            virtual ~CacheDriver();
        };

        /**
         * Factory class that can load and instantiate a Cache implementation based on the
         * information in the CacheOptions settings.
         */
        class OSGEARTH_EXPORT CacheFactory
        {
        public:
            static osgEarth::Cache* create( const CacheOptions& options);
        };
    }
}

#endif // OSGEARTH_CACHE_H