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/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * Copyright (C) 2019, Raspberry Pi (Trading) Limited
 *
 * agc.cpp - AGC/AEC control algorithm
 */

#include <map>

#include "linux/bcm2835-isp.h"

#include "../awb_status.h"
#include "../device_status.h"
#include "../histogram.hpp"
#include "../logging.hpp"
#include "../lux_status.h"
#include "../metadata.hpp"

#include "agc.hpp"

using namespace RPi;

#define NAME "rpi.agc"

#define PIPELINE_BITS 13 // seems to be a 13-bit pipeline

void AgcMeteringMode::Read(boost::property_tree::ptree const &params)
{
	int num = 0;
	for (auto &p : params.get_child("weights")) {
		if (num == AGC_STATS_SIZE)
			throw std::runtime_error("AgcConfig: too many weights");
		weights[num++] = p.second.get_value<double>();
	}
	if (num != AGC_STATS_SIZE)
		throw std::runtime_error("AgcConfig: insufficient weights");
}

static std::string
read_metering_modes(std::map<std::string, AgcMeteringMode> &metering_modes,
		    boost::property_tree::ptree const &params)
{
	std::string first;
	for (auto &p : params) {
		AgcMeteringMode metering_mode;
		metering_mode.Read(p.second);
		metering_modes[p.first] = std::move(metering_mode);
		if (first.empty())
			first = p.first;
	}
	return first;
}

static int read_double_list(std::vector<double> &list,
			    boost::property_tree::ptree const &params)
{
	for (auto &p : params)
		list.push_back(p.second.get_value<double>());
	return list.size();
}

void AgcExposureMode::Read(boost::property_tree::ptree const &params)
{
	int num_shutters =
		read_double_list(shutter, params.get_child("shutter"));
	int num_ags = read_double_list(gain, params.get_child("gain"));
	if (num_shutters < 2 || num_ags < 2)
		throw std::runtime_error(
			"AgcConfig: must have at least two entries in exposure profile");
	if (num_shutters != num_ags)
		throw std::runtime_error(
			"AgcConfig: expect same number of exposure and gain entries in exposure profile");
}

static std::string
read_exposure_modes(std::map<std::string, AgcExposureMode> &exposure_modes,
		    boost::property_tree::ptree const &params)
{
	std::string first;
	for (auto &p : params) {
		AgcExposureMode exposure_mode;
		exposure_mode.Read(p.second);
		exposure_modes[p.first] = std::move(exposure_mode);
		if (first.empty())
			first = p.first;
	}
	return first;
}

void AgcConstraint::Read(boost::property_tree::ptree const &params)
{
	std::string bound_string = params.get<std::string>("bound", "");
	transform(bound_string.begin(), bound_string.end(),
		  bound_string.begin(), ::toupper);
	if (bound_string != "UPPER" && bound_string != "LOWER")
		throw std::runtime_error(
			"AGC constraint type should be UPPER or LOWER");
	bound = bound_string == "UPPER" ? Bound::UPPER : Bound::LOWER;
	q_lo = params.get<double>("q_lo");
	q_hi = params.get<double>("q_hi");
	Y_target.Read(params.get_child("y_target"));
}

static AgcConstraintMode
read_constraint_mode(boost::property_tree::ptree const &params)
{
	AgcConstraintMode mode;
	for (auto &p : params) {
		AgcConstraint constraint;
		constraint.Read(p.second);
		mode.push_back(std::move(constraint));
	}
	return mode;
}

static std::string read_constraint_modes(
	std::map<std::string, AgcConstraintMode> &constraint_modes,
	boost::property_tree::ptree const &params)
{
	std::string first;
	for (auto &p : params) {
		constraint_modes[p.first] = read_constraint_mode(p.second);
		if (first.empty())
			first = p.first;
	}
	return first;
}

void AgcConfig::Read(boost::property_tree::ptree const &params)
{
	RPI_LOG("AgcConfig");
	default_metering_mode = read_metering_modes(
		metering_modes, params.get_child("metering_modes"));
	default_exposure_mode = read_exposure_modes(
		exposure_modes, params.get_child("exposure_modes"));
	default_constraint_mode = read_constraint_modes(
		constraint_modes, params.get_child("constraint_modes"));
	Y_target.Read(params.get_child("y_target"));
	speed = params.get<double>("speed", 0.2);
	startup_frames = params.get<uint16_t>("startup_frames", 10);
	fast_reduce_threshold =
		params.get<double>("fast_reduce_threshold", 0.4);
	base_ev = params.get<double>("base_ev", 1.0);
}

Agc::Agc(Controller *controller)
	: AgcAlgorithm(controller), metering_mode_(nullptr),
	  exposure_mode_(nullptr), constraint_mode_(nullptr),
	  frame_count_(0), lock_count_(0)
{
	ev_ = status_.ev = 1.0;
	flicker_period_ = status_.flicker_period = 0.0;
	fixed_shutter_ = status_.fixed_shutter = 0;
	fixed_analogue_gain_ = status_.fixed_analogue_gain = 0.0;
	// set to zero initially, so we can tell it's not been calculated
	status_.total_exposure_value = 0.0;
	status_.target_exposure_value = 0.0;
	status_.locked = false;
	output_status_ = status_;
}

char const *Agc::Name() const
{
	return NAME;
}

void Agc::Read(boost::property_tree::ptree const &params)
{
	RPI_LOG("Agc");
	config_.Read(params);
	// Set the config's defaults (which are the first ones it read) as our
	// current modes, until someone changes them.  (they're all known to
	// exist at this point)
	metering_mode_name_ = config_.default_metering_mode;
	metering_mode_ = &config_.metering_modes[metering_mode_name_];
	exposure_mode_name_ = config_.default_exposure_mode;
	exposure_mode_ = &config_.exposure_modes[exposure_mode_name_];
	constraint_mode_name_ = config_.default_constraint_mode;
	constraint_mode_ = &config_.constraint_modes[constraint_mode_name_];
}

void Agc::SetEv(double ev)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	ev_ = ev;
}

void Agc::SetFlickerPeriod(double flicker_period)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	flicker_period_ = flicker_period;
}

void Agc::SetFixedShutter(double fixed_shutter)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	fixed_shutter_ = fixed_shutter;
}

void Agc::SetFixedAnalogueGain(double fixed_analogue_gain)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	fixed_analogue_gain_ = fixed_analogue_gain;
}

void Agc::SetMeteringMode(std::string const &metering_mode_name)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	metering_mode_name_ = metering_mode_name;
}

void Agc::SetExposureMode(std::string const &exposure_mode_name)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	exposure_mode_name_ = exposure_mode_name;
}

void Agc::SetConstraintMode(std::string const &constraint_mode_name)
{
	std::unique_lock<std::mutex> lock(settings_mutex_);
	constraint_mode_name_ = constraint_mode_name;
}

void Agc::SwitchMode(CameraMode const &camera_mode, Metadata *metadata)
{
	// On a mode switch, it's possible the exposure profile could change,
	// so we run through the dividing up of exposure/gain again and
	// write the results into the metadata we've been given.
	if (status_.total_exposure_value) {
		housekeepConfig();
		divvyupExposure();
		writeAndFinish(metadata, false);
	}
}

void Agc::Prepare(Metadata *image_metadata)
{
	AgcStatus status;
	{
		std::unique_lock<std::mutex> lock(output_mutex_);
		status = output_status_;
	}
	int lock_count = lock_count_;
	lock_count_ = 0;
	status.digital_gain = 1.0;
	if (status_.total_exposure_value) {
		// Process has run, so we have meaningful values.
		DeviceStatus device_status;
		if (image_metadata->Get("device.status", device_status) == 0) {
			double actual_exposure = device_status.shutter_speed *
						 device_status.analogue_gain;
			if (actual_exposure) {
				status.digital_gain =
					status_.total_exposure_value /
					actual_exposure;
				RPI_LOG("Want total exposure " << status_.total_exposure_value);
				// Never ask for a gain < 1.0, and also impose
				// some upper limit. Make it customisable?
				status.digital_gain = std::max(
					1.0,
					std::min(status.digital_gain, 4.0));
				RPI_LOG("Actual exposure " << actual_exposure);
				RPI_LOG("Use digital_gain " << status.digital_gain);
				RPI_LOG("Effective exposure " << actual_exposure * status.digital_gain);
				// Decide whether AEC/AGC has converged.
				// Insist AGC is steady for MAX_LOCK_COUNT
				// frames before we say we are "locked".
				// (The hard-coded constants may need to
				// become customisable.)
				if (status.target_exposure_value) {
#define MAX_LOCK_COUNT 3
					double err = 0.10 * status.target_exposure_value + 200;
					if (actual_exposure <
					    status.target_exposure_value + err
					    && actual_exposure >
					    status.target_exposure_value - err)
						lock_count_ =
							std::min(lock_count + 1,
							       MAX_LOCK_COUNT);
					else if (actual_exposure <
						 status.target_exposure_value
						 + 1.5 * err &&
						 actual_exposure >
						 status.target_exposure_value
						 - 1.5 * err)
						lock_count_ = lock_count;
					RPI_LOG("Lock count: " << lock_count_);
				}
			}
		} else
			RPI_LOG(Name() << ": no device metadata");
		status.locked = lock_count_ >= MAX_LOCK_COUNT;
		//printf("%s\n", status.locked ? "+++++++++" : "-");
		image_metadata->Set("agc.status", status);
	}
}

void Agc::Process(StatisticsPtr &stats, Metadata *image_metadata)
{
	frame_count_++;
	// First a little bit of housekeeping, fetching up-to-date settings and
	// configuration, that kind of thing.
	housekeepConfig();
	// Get the current exposure values for the frame that's just arrived.
	fetchCurrentExposure(image_metadata);
	// Compute the total gain we require relative to the current exposure.
	double gain, target_Y;
	computeGain(stats.get(), image_metadata, gain, target_Y);
	// Now compute the target (final) exposure which we think we want.
	computeTargetExposure(gain);
	// Some of the exposure has to be applied as digital gain, so work out
	// what that is. This function also tells us whether it's decided to
	// "desaturate" the image more quickly.
	bool desaturate = applyDigitalGain(image_metadata, gain, target_Y);
	// The results have to be filtered so as not to change too rapidly.
	filterExposure(desaturate);
	// The last thing is to divvy up the exposure value into a shutter time
	// and analogue_gain, according to the current exposure mode.
	divvyupExposure();
	// Finally advertise what we've done.
	writeAndFinish(image_metadata, desaturate);
}

static void copy_string(std::string const &s, char *d, size_t size)
{
	size_t length = s.copy(d, size - 1);
	d[length] = '\0';
}

void Agc::housekeepConfig()
{
	// First fetch all the up-to-date settings, so no one else has to do it.
	std::string new_exposure_mode_name, new_constraint_mode_name,
		new_metering_mode_name;
	{
		std::unique_lock<std::mutex> lock(settings_mutex_);
		new_metering_mode_name = metering_mode_name_;
		new_exposure_mode_name = exposure_mode_name_;
		new_constraint_mode_name = constraint_mode_name_;
		status_.ev = ev_;
		status_.fixed_shutter = fixed_shutter_;
		status_.fixed_analogue_gain = fixed_analogue_gain_;
		status_.flicker_period = flicker_period_;
	}
	RPI_LOG("ev " << status_.ev << " fixed_shutter "
		      << status_.fixed_shutter << " fixed_analogue_gain "
		      << status_.fixed_analogue_gain);
	// Make sure the "mode" pointers point to the up-to-date things, if
	// they've changed.
	if (strcmp(new_metering_mode_name.c_str(), status_.metering_mode)) {
		auto it = config_.metering_modes.find(new_metering_mode_name);
		if (it == config_.metering_modes.end())
			throw std::runtime_error("Agc: no metering mode " +
						 new_metering_mode_name);
		metering_mode_ = &it->second;
		copy_string(new_metering_mode_name, status_.metering_mode,
			    sizeof(status_.metering_mode));
	}
	if (strcmp(new_exposure_mode_name.c_str(), status_.exposure_mode)) {
		auto it = config_.exposure_modes.find(new_exposure_mode_name);
		if (it == config_.exposure_modes.end())
			throw std::runtime_error("Agc: no exposure profile " +
						 new_exposure_mode_name);
		exposure_mode_ = &it->second;
		copy_string(new_exposure_mode_name, status_.exposure_mode,
			    sizeof(status_.exposure_mode));
	}
	if (strcmp(new_constraint_mode_name.c_str(), status_.constraint_mode)) {
		auto it =
			config_.constraint_modes.find(new_constraint_mode_name);
		if (it == config_.constraint_modes.end())
			throw std::runtime_error("Agc: no constraint list " +
						 new_constraint_mode_name);
		constraint_mode_ = &it->second;
		copy_string(new_constraint_mode_name, status_.constraint_mode,
			    sizeof(status_.constraint_mode));
	}
	RPI_LOG("exposure_mode "
		<< new_exposure_mode_name << " constraint_mode "
		<< new_constraint_mode_name << " metering_mode "
		<< new_metering_mode_name);
}

void Agc::fetchCurrentExposure(Metadata *image_metadata)
{
	std::unique_lock<Metadata> lock(*image_metadata);
	DeviceStatus *device_status =
		image_metadata->GetLocked<DeviceStatus>("device.status");
	if (!device_status)
		throw std::runtime_error("Agc: no device metadata");
	current_.shutter = device_status->shutter_speed;
	current_.analogue_gain = device_status->analogue_gain;
	AgcStatus *agc_status =
		image_metadata->GetLocked<AgcStatus>("agc.status");
	current_.total_exposure = agc_status ? agc_status->total_exposure_value : 0;
	current_.total_exposure_no_dg = current_.shutter * current_.analogue_gain;
}

static double compute_initial_Y(bcm2835_isp_stats *stats, Metadata *image_metadata,
				double weights[])
{
	bcm2835_isp_stats_region *regions = stats->agc_stats;
	struct AwbStatus awb;
	awb.gain_r = awb.gain_g = awb.gain_b = 1.0; // in case no metadata
	if (image_metadata->Get("awb.status", awb) != 0)
		RPI_WARN("Agc: no AWB status found");
	double Y_sum = 0, weight_sum = 0;
	for (int i = 0; i < AGC_STATS_SIZE; i++) {
		if (regions[i].counted == 0)
			continue;
		weight_sum += weights[i];
		double Y = regions[i].r_sum * awb.gain_r * .299 +
			   regions[i].g_sum * awb.gain_g * .587 +
			   regions[i].b_sum * awb.gain_b * .114;
		Y /= regions[i].counted;
		Y_sum += Y * weights[i];
	}
	return Y_sum / weight_sum / (1 << PIPELINE_BITS);
}

// We handle extra gain through EV by adjusting our Y targets. However, you
// simply can't monitor histograms once they get very close to (or beyond!)
// saturation, so we clamp the Y targets to this value. It does mean that EV