/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * Copyright (C) 2019, Raspberry Pi Ltd
 *
 * alsc.h - ALSC (auto lens shading correction) control algorithm
 */
#pragma once

#include <array>
#include <mutex>
#include <condition_variable>
#include <thread>
#include <vector>

#include <libcamera/geometry.h>

#include "../algorithm.h"
#include "../alsc_status.h"
#include "../statistics.h"

namespace RPiController {

/* Algorithm to generate automagic LSC (Lens Shading Correction) tables. */

/*
 * The Array2D class is a very thin wrapper round std::vector so that it can
 * be used in exactly the same way in the code but carries its correct width
 * and height ("dimensions") with it.
 */

template<typename T>
class Array2D
{
public:
	using Size = libcamera::Size;

	const Size &dimensions() const { return dimensions_; }

	size_t size() const { return data_.size(); }

	const std::vector<T> &data() const { return data_; }

	void resize(const Size &dims)
	{
		dimensions_ = dims;
		data_.resize(dims.width * dims.height);
	}

	void resize(const Size &dims, const T &value)
	{
		resize(dims);
		std::fill(data_.begin(), data_.end(), value);
	}

	T &operator[](int index) { return data_[index]; }

	const T &operator[](int index) const { return data_[index]; }

	T *ptr() { return data_.data(); }

	const T *ptr() const { return data_.data(); }

	auto begin() { return data_.begin(); }
	auto end() { return data_.end(); }

private:
	Size dimensions_;
	std::vector<T> data_;
};

/*
 * We'll use the term SparseArray for the large sparse matrices that are
 * XY tall but have only 4 non-zero elements on each row.
 */

template<typename T>
using SparseArray = std::vector<std::array<T, 4>>;

struct AlscCalibration {
	double ct;
	Array2D<double> table;
};

struct AlscConfig {
	/* Only repeat the ALSC calculation every "this many" frames */
	uint16_t framePeriod;
	/* number of initial frames for which speed taken as 1.0 (maximum) */
	uint16_t startupFrames;
	/* IIR filter speed applied to algorithm results */
	double speed;
	double sigmaCr;
	double sigmaCb;
	double minCount;
	uint16_t minG;
	double omega;
	uint32_t nIter;
	Array2D<double> luminanceLut;
	double luminanceStrength;
	std::vector<AlscCalibration> calibrationsCr;
	std::vector<AlscCalibration> calibrationsCb;
	double defaultCt; /* colour temperature if no metadata found */
	double threshold; /* iteration termination threshold */
	double lambdaBound; /* upper/lower bound for lambda from a value of 1 */
	libcamera::Size tableSize;
};

class Alsc : public Algorithm
{
public:
	Alsc(Controller *controller = NULL);
	~Alsc();
	char const *name() const override;
	void initialise() override;
	void switchMode(CameraMode const &cameraMode, Metadata *metadata) override;
	int read(const libcamera::YamlObject &params) override;
	void prepare(Metadata *imageMetadata) override;
	void process(StatisticsPtr &stats, Metadata *imageMetadata) override;

private:
	/* configuration is read-only, and available to both threads */
	AlscConfig config_;
	bool firstTime_;
	CameraMode cameraMode_;
	Array2D<double> luminanceTable_;
	std::thread asyncThread_;
	void asyncFunc(); /* asynchronous thread function */
	std::mutex mutex_;
	/* condvar for async thread to wait on */
	std::condition_variable asyncSignal_;
	/* condvar for synchronous thread to wait on */
	std::condition_variable syncSignal_;
	/* for sync thread to check  if async thread finished (requires mutex) */
	bool asyncFinished_;
	/* for async thread to check if it's been told to run (requires mutex) */
	bool asyncStart_;
	/* for async thread to check if it's been told to quit (requires mutex) */
	bool asyncAbort_;

	/*
	 * The following are only for the synchronous thread to use:
	 * for sync thread to note its has asked async thread to run
	 */
	bool asyncStarted_;
	/* counts up to framePeriod before restarting the async thread */
	int framePhase_;
	/* counts up to startupFrames */
	int frameCount_;
	/* counts up to startupFrames for Process function */
	int frameCount2_;
	std::array<Array2D<double>, 3> syncResults_;
	std::array<Array2D<double>, 3> prevSyncResults_;
	void waitForAysncThread();
	/*
	 * The following are for the asynchronous thread to use, though the main
	 * thread can set/reset them if the async thread is known to be idle:
	 */
	void restartAsync(StatisticsPtr &stats, Metadata *imageMetadata);
	/* copy out the results from the async thread so that it can be restarted */
	void fetchAsyncResults();
	double ct_;
	RgbyRegions statistics_;
	std::array<Array2D<double>, 3> asyncResults_;
	Array2D<double> asyncLambdaR_;
	Array2D<double> asyncLambdaB_;
	void doAlsc();
	Array2D<double> lambdaR_;
	Array2D<double> lambdaB_;

	/* Temporaries for the computations */
	std::array<Array2D<double>, 5> tmpC_;
	std::array<SparseArray<double>, 3> tmpM_;
};

} /* namespace RPiController */