/*
  Copyright 2015 David Robillard <http://drobilla.net>

  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.

  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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 LV2_PLUGIN_HPP
#define LV2_PLUGIN_HPP

#include "lv2/lv2plug.in/ns/lv2core/lv2.h"

namespace lv2 {

/**
   C++ wrapper for an LV2 plugin.

   This interface is a convenience for plugin authors only, and is not an ABI
   used by hosts.  Plugin authors should inherit from this interface, and use
   the resulting class as the template parameter to lv2::set_descriptor() to
   initialise a descriptor for the plugin.

   This class is a stateless interface and imposes no restrictions or overhead
   compared to a plugin implemented using the underlying C interface.  Note
   that this is not a virtual class, so calling methods from a Plugin* base
   pointer will not work.  Instead, anything that must dispatch on Plugin
   methods takes a template parameter for static dispatch.
*/
class Plugin
{
public:
	/**
	   Instantiate the plugin.

	   Note that instance initialisation should generally occur in activate()
	   rather than here. If a host calls instantiate(), it MUST call cleanup()
	   at some point in the future.

	   @param sample_rate Sample rate, in Hz, for the new plugin instance.

	   @param bundle_path Path to the LV2 bundle which contains this plugin
	   binary. It MUST include the trailing directory separator (e.g. '/') so
	   that simply appending a filename will yield the path to that file in the
	   bundle.

	   @param features A NULL terminated array of LV2_Feature structs which
	   represent the features the host supports. Plugins may refuse to
	   instantiate if required features are not found here. However, hosts MUST
	   NOT use this as a discovery mechanism: instead, use the RDF data to
	   determine which features are required and do not attempt to instantiate
	   unsupported plugins at all. This parameter MUST NOT be NULL, i.e. a host
	   that supports no features MUST pass a single element array containing
	   NULL.

	   @return A handle for the new plugin instance, or NULL if instantiation
	   has failed.
	*/
	Plugin(double                   sample_rate,
	       const char*              bundle_path,
	       const LV2_Feature*const* features)
	{}

	/**
	   Connect a port on a plugin instance to a memory location.

	   Plugin writers should be aware that the host may elect to use the same
	   buffer for more than one port and even use the same buffer for both
	   input and output (see lv2:inPlaceBroken in lv2.ttl).

	   If the plugin has the feature lv2:hardRTCapable then there are various
	   things that the plugin MUST NOT do within the connect_port() function;
	   see lv2core.ttl for details.

	   connect_port() MUST be called at least once for each port before run()
	   is called, unless that port is lv2:connectionOptional. The plugin must
	   pay careful attention to the block size passed to run() since the block
	   allocated may only just be large enough to contain the data, and is not
	   guaranteed to remain constant between run() calls.

	   connect_port() may be called more than once for a plugin instance to
	   allow the host to change the buffers that the plugin is reading or
	   writing. These calls may be made before or after activate() or
	   deactivate() calls.

	   @param port Index of the port to connect. The host MUST NOT try to
	   connect a port index that is not defined in the plugin's RDF data. If
	   it does, the plugin's behaviour is undefined (a crash is likely).

	   @param data_location Pointer to data of the type defined by the port
	   type in the plugin's RDF data (e.g. an array of float for an
	   lv2:AudioPort). This pointer must be stored by the plugin instance and
	   used to read/write data when run() is called. Data present at the time
	   of the connect_port() call MUST NOT be considered meaningful.
	*/
	void connect_port(uint32_t port, void* data_location) {}

	/**
	   Initialise a plugin instance and activate it for use.

	   This is separated from instantiate() to aid real-time support and so
	   that hosts can reinitialise a plugin instance by calling deactivate()
	   and then activate(). In this case the plugin instance MUST reset all
	   state information dependent on the history of the plugin instance except
	   for any data locations provided by connect_port(). If there is nothing
	   for activate() to do then this field may be NULL.

	   When present, hosts MUST call this function once before run() is called
	   for the first time. This call SHOULD be made as close to the run() call
	   as possible and indicates to real-time plugins that they are now live,
	   however plugins MUST NOT rely on a prompt call to run() after
	   activate().

	   The host MUST NOT call activate() again until deactivate() has been
	   called first. If a host calls activate(), it MUST call deactivate() at
	   some point in the future. Note that connect_port() may be called before
	   or after activate().
	*/
	void activate() {}

	/**
	   Run a plugin instance for a block.

	   Note that if an activate() function exists then it must be called before
	   run(). If deactivate() is called for a plugin instance then run() may
	   not be called until activate() has been called again.

	   If the plugin has the feature lv2:hardRTCapable then there are various
	   things that the plugin MUST NOT do within the run() function (see
	   lv2core.ttl for details).

	   As a special case, when `sample_count` is 0, the plugin should update
	   any output ports that represent a single instant in time (e.g. control
	   ports, but not audio ports). This is particularly useful for latent
	   plugins, which should update their latency output port so hosts can
	   pre-roll plugins to compute latency. Plugins MUST NOT crash when
	   `sample_count` is 0.

	   @param sample_count The block size (in samples) for which the plugin
	   instance must run.
	*/
	void run(uint32_t sample_count) {}

	/**
	   Deactivate a plugin instance (counterpart to activate()).

	   Hosts MUST deactivate all activated instances after they have been run()
	   for the last time. This call SHOULD be made as close to the last run()
	   call as possible and indicates to real-time plugins that they are no
	   longer live, however plugins MUST NOT rely on prompt deactivation. If
	   there is nothing for deactivate() to do then this field may be NULL

	   Deactivation is not similar to pausing since the plugin instance will be
	   reinitialised by activate(). However, deactivate() itself MUST NOT fully
	   reset plugin state. For example, the host may deactivate a plugin, then
	   store its state (using some extension to do so).

	   Hosts MUST NOT call deactivate() unless activate() was previously
	   called. Note that connect_port() may be called before or after
	   deactivate().
	*/
	void deactivate() {}

	/**
	   Return additional plugin data defined by some extenion.

	   A typical use of this facility is to return a struct containing function
	   pointers to extend the LV2_Descriptor API.

	   The actual type and meaning of the returned object MUST be specified
	   precisely by the extension. This function MUST return NULL for any
	   unsupported URI. If a plugin does not support any extension data, this
	   field may be NULL.

	   The host is never responsible for freeing the returned value.
	*/
	static const void* extension_data(const char* uri) { return NULL; }
};

template<typename Plugin>
static LV2_Handle s_instantiate(const LV2_Descriptor*     descriptor,
                                double                    sample_rate,
                                const char*               bundle_path,
                                const LV2_Feature* const* features) {
	Plugin* t = new Plugin(sample_rate, bundle_path, features);
	if (!t) {
		delete t;
		return nullptr;
	}

	return reinterpret_cast<LV2_Handle>(t);
}

template<typename Plugin>
static void s_connect_port(LV2_Handle instance, uint32_t port, void* buf)
{
	reinterpret_cast<Plugin*>(instance)->connect_port(port, buf);
}

template<typename Plugin>
static void s_activate(LV2_Handle instance)
{
	reinterpret_cast<Plugin*>(instance)->activate();
}

template<typename Plugin>
static void s_run(LV2_Handle instance, uint32_t sample_count)
{
	reinterpret_cast<Plugin*>(instance)->run(sample_count);
}

template<typename Plugin>
static void s_deactivate(LV2_Handle instance)
{
	reinterpret_cast<Plugin*>(instance)->deactivate();
}

template<typename Plugin>
static void s_cleanup(LV2_Handle instance)
{
	delete reinterpret_cast<Plugin*>(instance);
}

/**
   Get an LV2_Descriptor for a plugin class.

   @code
   static const LV2_Descriptor a = lv2::descriptor<Amp>("http://example.org/amp");
   @endcode
*/
template<typename Plugin>
static LV2_Descriptor
descriptor(const char* uri)
{
	const LV2_Descriptor desc = { uri,
	                              &s_instantiate<Plugin>,
	                              &s_connect_port<Plugin>,
	                              &s_activate<Plugin>,
	                              &s_run<Plugin>,
	                              &s_deactivate<Plugin>,
	                              &s_cleanup<Plugin>,
	                              &Plugin::extension_data };
	return desc;
}

} /* namespace lv2 */

#endif /* LV2_PLUGIN_HPP */