#pragma once

#include <stdint.h>

// Checks that the Nano shows what was sent. The Nano has no acknowledgement and drops
// bytes when its serial buffer overflows; a lost byte in a bitmap shifts the rest of the
// image (the dots after it land too early). After a frame the ESP32 asks for the checksum
// of the Nano's image (C command, bufferCrc() in lib/BROSE9323) and compares it with its
// own copy. A wrong checksum, a missing answer or a restarted Nano (READY) makes it send
// the whole image again (repair). Besides that the whole image is sent again every
// resync interval, which also fixes what the check can't see.
//
// Pure logic (tested in test/test_esp32); nano_link/nano_monitor does the serial part.

struct FrameCheckStats
{
	uint32_t checks = 0;     // answers that matched
	uint32_t mismatches = 0; // answers that didn't
	uint32_t no_reply = 0;   // checks without an answer in FRAME_CHECK_TIMEOUT
	uint32_t errors = 0;     // ERR: lines from the Nano
	uint32_t restarts = 0;   // READY while it was on: the Nano restarted (power dip?)
	uint32_t repairs = 0;    // whole image sent again because of one of the above
	char last_error[48] = "";
};

class FrameCheck
{
public:
	// The Nano was switched on or off: forget the check in progress
	void reset(uint32_t now);

	// A check (C) should be sent now: a frame was sent since the last one (frames_sent
	// changed), none is waiting for its answer and the last one is FRAME_CHECK_INTERVAL ago
	bool due(uint32_t frames_sent, uint32_t now) const;
	// The C was sent; expected: the checksum of the ESP32's copy
	void sent(uint16_t expected, uint32_t frames_sent, uint32_t now);

	// One line from the Nano (without the '\n')
	void line(const char *text, uint32_t now);

	// Call each loop(). True: send the whole image now (repair, or every resync_ms; 0 = no
	// periodic resync)
	bool resyncNow(uint32_t now, uint32_t resync_ms);

	const FrameCheckStats &stats() const { return _stats; }

private:
	FrameCheckStats _stats;
	bool _pending = false;
	uint16_t _expected = 0;
	uint32_t _sent_at = 0;
	bool _checked_any = false;  // since reset()
	uint32_t _checked_frames = 0;
	uint32_t _last_check = 0;
	bool _replied = false;      // the Nano answered since reset(): its TX is wired
	bool _problem = false;      // repair at the next chance
	uint32_t _last_resync = 0;
};