/*
This Source Code Form is subject to the
terms of the Mozilla Public License, v.
2.0. If a copy of the MPL was not
distributed with this file, You can
obtain one at
http://mozilla.org/MPL/2.0/.
*/

#pragma once

#include <atomic>
#include <deque>
#include <memory>
#include <mutex>
#include <thread>
#include <vector>

#include "hardware/diagnostics/hardware_diagnostics.h"
#include "hardware/hardware_config.h"
#include "hardware/protocol/protocol_session.h"
#include "hardware/transport/hardware_transport.h"

// owner of every hardware protocol v2 connection, regardless of the transport behind it
//
// threading: a single worker thread does all of the blocking work, that is opening ports, reading
// and writing bytes and turning them into frames. the simulation thread only exchanges ready made
// frames with it through small locked queues, and is the only one which ever touches simulation
// state. a device which stops responding, floods the link or disappears therefore cannot stall the
// simulation
//
// links may be added, switched off and removed while the simulation runs, which is what lets the
// debug panel release a port so that a controller can be reprogrammed and then reconnected

namespace hardware
{

class hardware_link : public session_output
{

public:
// methods
	hardware_link( std::unique_ptr<hardware_transport> Transport, config const &Config );
	~hardware_link() override;

	// worker thread: services the transport
	void service();
	// simulation thread: processes received frames and runs the session
	void update( double const Deltatime, state_snapshot const &Snapshot );
	// simulation thread: the report gathered during the last update
	link_report const &report() const { return m_report; }
	// simulation thread: the session, for the debug panel
	protocol_session &session() { return m_session; }

	// switching a link off closes the port and stops reconnecting, which frees the device
	void set_enabled( bool const Enabled );
	bool enabled() const { return m_enabled; }
	std::string const &endpoint() const { return m_endpoint; }

	void send_packet( packet_header const &Header, std::vector<std::uint8_t> const &Payload ) override;

private:
// members
	std::unique_ptr<hardware_transport> m_transport;
	config m_config;
	protocol_session m_session;
	link_report m_report;
	std::string m_endpoint;
	std::atomic<bool> m_enabled { true };

	// worker thread only
	frame_decoder m_decoder;
	std::vector<std::uint8_t> m_readbuffer;
	std::vector<std::uint8_t> m_writebuffer;
	std::chrono::steady_clock::time_point m_lastconnectattempt;

	// simulation thread only
	frame_decoder::counters m_lastframeerrors;

	// shared
	std::mutex m_mutex;
	std::deque<decoded_packet> m_rxqueue;
	std::deque<std::vector<std::uint8_t>> m_txqueue;
	transport_diagnostics m_transportstatus;
	frame_decoder::counters m_framecounters;
	bool m_transportdropped = false;
};

class hardware_manager
{

public:
// methods
	explicit hardware_manager( config const &Config );
	~hardware_manager();

	// called once per simulation frame from the input polling code; the time step is measured here
	void update();

	std::vector<link_report> const &reports() const { return m_reports; }
	bool active() const { return false == m_reports.empty(); }

	// ---- operations available from the debug panel, simulation thread only ----

	// adds a serial link while the simulation runs; false if the port is already in use
	bool add_serial_link( std::string const &Port, int const Baud );
	// removes a link; its port is released
	bool remove_link( std::size_t const Index );
	// switching a link off releases its port without forgetting the link
	void set_link_enabled( std::size_t const Index, bool const Enabled );

	bool start_diagnostic( std::size_t const Index, std::uint8_t const Function );
	void cancel_diagnostic( std::size_t const Index );
	void answer_prompt( std::size_t const Index, std::uint8_t const Option );

	// serial ports present in the system, refreshed by the worker thread
	std::vector<std::string> available_ports() const;

	// the running instance, if any; used by the debug panel
	static hardware_manager *instance() { return s_instance; }

private:
// methods
	void worker();
	std::shared_ptr<hardware_link> link_at( std::size_t const Index ) const;

// members
	static hardware_manager *s_instance;

	config m_config;
	mutable std::mutex m_linksmutex;
	std::vector<std::shared_ptr<hardware_link>> m_links;
	std::vector<link_report> m_reports;
	state_snapshot m_snapshot;

	mutable std::mutex m_portsmutex;
	std::vector<std::string> m_ports;
	std::chrono::steady_clock::time_point m_lastportscan;

	std::chrono::steady_clock::time_point m_lastupdate;
	bool m_updatestarted = false;
	std::thread m_thread;
	std::atomic<bool> m_quit { false };
};

} // namespace hardware