/* Reorder samples hook.
 *
 * Author: Philipp Jungkamp <philipp.jungkamp@opal-rt.com>
 * SPDX-FileCopyrightText: 2023, OPAL-RT Germany GmbH
 * SPDX-License-Identifier: Apache-2.0
 */

#include <cinttypes>
#include <cstring>
#include <ctime>
#include <vector>
#include <algorithm>

#include <villas/hook.hpp>
#include <villas/sample.hpp>
#include <villas/timing.hpp>

namespace villas {
namespace node {

class ReorderTsHook : public Hook {

protected:
	std::vector<Sample *> window;
	std::size_t window_size;
	Sample *buffer;

	void swapSample(Sample *lhs, Sample *rhs)
	{
		if (buffer) {
			sample_copy(buffer, lhs);
			sample_copy(lhs, rhs);
			sample_copy(rhs, buffer);
		} else {
			buffer = sample_clone(lhs);
			sample_copy(lhs, rhs);
			sample_copy(rhs, buffer);
		}
	}

public:
	ReorderTsHook(Path *p, Node *n, int fl, int prio, bool en = true) :
		Hook(p, n, fl, prio, en),
		window{},
		window_size(16),
		buffer(nullptr)
	{ }

	virtual
	void parse(json_t *json)
	{
		assert(state != State::STARTED);

		json_error_t err;
		int ret = json_unpack_ex(json, &err, 0, "{ s?: i }",
			"window_size", &window_size
		);
		if (ret)
			throw ConfigError(json, err, "node-config-hook-reorder-ts");

		state = State::PARSED;
	}

	virtual
	void start()
	{
		assert(state == State::PREPARED || state == State::STOPPED);

		window.reserve(window_size);

		state = State::STARTED;
	}

	virtual
	void stop()
	{
		assert(state == State::STARTED);

		for (auto sample : window)
			sample_free(sample);

		if (buffer)
			sample_free(buffer);

		window.clear();

		state = State::STOPPED;
	}

	virtual
	Hook::Reason process(Sample *smp)
	{
		assert(state == State::STARTED);
		assert(smp);

		if (window.empty()) {
			window.push_back(sample_clone(smp));

			logger->debug("window.size={}/{}", window.size(), window_size);

			return Hook::Reason::SKIP_SAMPLE;
		}

		for (std::size_t i = window.size() - 1;; i--) {
			if (time_cmp(&smp->ts.origin, &window[i]->ts.origin) >= 0) {
				if (i != window.size() - 1)
					logger->warn("Fixing reordered Sample");

				if (window.size() == window_size) {
					Sample *window_sample = window.front();
					std::copy(
						++std::begin(window),
						std::next(std::begin(window), i + 1),
						std::begin(window));
					window[i] = window_sample;
					swapSample(window_sample, smp);

					return Hook::Reason::OK;
				} else {
					window.push_back(nullptr);
					std::copy_backward(
						std::next(std::begin(window), i + 1),
						--std::end(window),
						std::end(window));
					window[i + 1] = sample_clone(smp);

					logger->debug("window.size={}/{}", window.size(), window_size);

					return Hook::Reason::SKIP_SAMPLE;
				}
			}

			if (!i)
				break;
		}

		logger->error("Could not reorder Sample");

		return Hook::Reason::SKIP_SAMPLE;
	}

	virtual
	void restart()
	{
		assert(state == State::STARTED);

		for (auto sample : window)
			sample_free(sample);

		window.clear();
	}
};

// Register hook
static char n[] = "reorder_ts";
static char d[] = "Reorder messages by their timestamp";
static HookPlugin<ReorderTsHook, n, d, (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH | (int) Hook::Flags::NODE_READ, 2> p;

} // namespace node
} // namespace villas