/*

  Copyright 2006-2016 David Robillard <d@drobilla.net>

  Copyright 2006 Steve Harris <steve@plugin.org.uk>

  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.

 */

/**

   LV2 headers are based on the URI of the specification they come from, so a

   consistent convention can be used even for unofficial extensions.  The URI

   of the core LV2 specification is <http://lv2plug.in/ns/lv2core>, by

   replacing `http:/` with `lv2` any header in the specification bundle can be

   included, in this case `lv2.h`.

 */

#include <lv2.h>

/** Include standard C headers */

#include <math.h>

#include <stdint.h>

#include <stdlib.h>

/**

   The URI is the identifier for a plugin, and how the host associates this

   implementation in code with its description in data.  In this plugin it is

   only used once in the code, but defining the plugin URI at the top of the

   file is a good convention to follow.  If this URI does not match that used

   in the data files, the host will fail to load the plugin.

 */

#define AMP_URI "http://lv2plug.in/plugins/eg-amp"

/**

   In code, ports are referred to by index.  An enumeration of port indices

   should be defined for readability.

 */

typedef enum {

	AMP_GAIN = 0,

	AMP_INPUT = 1,

	AMP_OUTPUT = 2

} PortIndex;

/**

   Every plugin defines a private structure for the plugin instance.  All data

   associated with a plugin instance is stored here, and is available to

   every instance method.  In this simple plugin, only port buffers need to be

   stored, since there is no additional instance data.

 */

typedef struct {

	// Port buffers

	const float* gain;

	const float* input;

	float* output;

} Amp;

/**

   The `instantiate()` function is called by the host to create a new plugin

   instance.  The host passes the plugin descriptor, sample rate, and bundle

   path for plugins that need to load additional resources (e.g. waveforms).

   The features parameter contains host-provided features defined in LV2

   extensions, but this simple plugin does not use any.

   This function is in the ``instantiation'' threading class, so no other

   methods on this instance will be called concurrently with it.

 */

static LV2_Handle

instantiate(const LV2_Descriptor* descriptor,

		double rate,

		const char* bundle_path,

		const LV2_Feature * const* features) {

	Amp* amp = (Amp*) calloc(1, sizeof (Amp));

	return (LV2_Handle) amp;

}

/**

   The `connect_port()` method is called by the host to connect a particular

   port to a buffer.  The plugin must store the data location, but data may not

   be accessed except in run().

   This method is in the ``audio'' threading class, and is called in the same

   context as run().

 */

static void

connect_port(LV2_Handle instance,

		uint32_t port,

		void* data) {

	Amp* amp = (Amp*) instance;

	switch ((PortIndex) port) {

		case AMP_GAIN:

			amp->gain = (const float*) data;

			break;

		case AMP_INPUT:

			amp->input = (const float*) data;

			break;

		case AMP_OUTPUT:

			amp->output = (float*) data;

			break;

	}

}

/**

   The `activate()` method is called by the host to initialise and prepare the

   plugin instance for running.  The plugin must reset all internal state

   except for buffer locations set by `connect_port()`.  Since this plugin has

   no other internal state, this method does nothing.

   This method is in the ``instantiation'' threading class, so no other

   methods on this instance will be called concurrently with it.

 */

static void

activate(LV2_Handle instance) {

}

/** Define a macro for converting a gain in dB to a coefficient. */

#define DB_CO(g) ((g) > -90.0f ? powf(10.0f, (g) * 0.05f) : 0.0f)

/**

   The `run()` method is the main process function of the plugin.  It processes

   a block of audio in the audio context.  Since this plugin is

   `lv2:hardRTCapable`, `run()` must be real-time safe, so blocking (e.g. with

   a mutex) or memory allocation are not allowed.

 */

static void

run(LV2_Handle instance, uint32_t n_samples) {

	const Amp* amp = (const Amp*) instance;

	const float gain = *(amp->gain);

	const float* const input = amp->input;

	float* const output = amp->output;

	const float coef = DB_CO(gain);

	for (uint32_t pos = 0; pos < n_samples; pos++) {

		output[pos] = input[pos] * coef;

	}

}

/**

   The `deactivate()` method is the counterpart to `activate()`, and is called by

   the host after running the plugin.  It indicates that the host will not call

   `run()` again until another call to `activate()` and is mainly useful for more

   advanced plugins with ``live'' characteristics such as those with auxiliary

   processing threads.  As with `activate()`, this plugin has no use for this

   information so this method does nothing.

   This method is in the ``instantiation'' threading class, so no other

   methods on this instance will be called concurrently with it.

 */

static void

deactivate(LV2_Handle instance) {

}

/**

   Destroy a plugin instance (counterpart to `instantiate()`).

   This method is in the ``instantiation'' threading class, so no other

   methods on this instance will be called concurrently with it.

 */

static void

cleanup(LV2_Handle instance) {

	free(instance);

}

/**

   The `extension_data()` function returns any extension data supported by the

   plugin.  Note that this is not an instance method, but a function on the

   plugin descriptor.  It is usually used by plugins to implement additional

   interfaces.  This plugin does not have any extension data, so this function

   returns NULL.

   This method is in the ``discovery'' threading class, so no other functions

   or methods in this plugin library will be called concurrently with it.

 */

static const void*

extension_data(const char* uri) {

	return NULL;

}

/**

   Every plugin must define an `LV2_Descriptor`.  It is best to define

   descriptors statically to avoid leaking memory and non-portable shared

   library constructors and destructors to clean up properly.

 */

static const LV2_Descriptor descriptor = {

	AMP_URI,

	instantiate,

	connect_port,

	activate,

	run,

	deactivate,

	cleanup,

	extension_data

};

/**

   The `lv2_descriptor()` function is the entry point to the plugin library.  The

   host will load the library and call this function repeatedly with increasing

   indices to find all the plugins defined in the library.  The index is not an

   indentifier, the URI of the returned descriptor is used to determine the

   identify of the plugin.

   This method is in the ``discovery'' threading class, so no other functions

   or methods in this plugin library will be called concurrently with it.

 */

LV2_SYMBOL_EXPORT

const LV2_Descriptor*

lv2_descriptor(uint32_t index) {

	switch (index) {

		case 0: return &descriptor;

		default: return NULL;

	}

}