#define F_CPU 8*1000000UL
#include <stdint.h>
#include <string.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/pgmspace.h>
#include <util/delay.h>

#ifndef PIN
#error need to define a PIN
#endif

/* port B		RJ45
 *  0
 *  1 BEEP (OC1A)
 *  2 SS		up:8
 *  3 MOSI		up:2
 *  4 MISO		up:4
 *  5 SCK		up:7
 * port C
 *  0-3
 *  4 (SDA)
 *  5 (SCL)
 * port D
 *  0 PS2_DATA (RXD)	kb:3
 *  1 PS2_DATA_O (TXD)
 *  2
 *  3 PS2_CLK_O (INT1)
 *  4 PS2_CLK (XCK)	kb:2
 *  5 PS2_PWREN
 *  6-7
 */

#define D_DATA		(1 << 0)
#define D_CLK		(1 << 4)
#define D_PWR		(1 << 5)

#define B_BEEP		(1 << 1)
#define B_OPEN		0
#define B_CLOSE		0
#define B_MISO		(1 << 4)

enum state {
	STATE_NONE = 0,
	STATE_FAILURE,
	STATE_POWERUP,
	STATE_INITRESET,
	STATE_CONFIG,
	STATE_IDLE,
	STATE_IDLEBLINK,
	STATE_INPUT,
	STATE_ACCEPT,
	STATE_REJECT,
#ifdef KILLSWITCH
	STATE_ERROR,
#endif
};
static volatile enum state state, nextstate;

static void power_up()
{
	DDRD = D_PWR;
	PORTD = D_DATA | D_CLK;
}

static void power_down()
{
	DDRD = D_PWR;
	PORTD = D_PWR;
}

static void usart_rx()
{
	UCSR0A = 0;
	UCSR0B = (1 << RXCIE0)				/* recv int en */
		| (1 << RXEN0);				/* do RX */
}

static void usart_rxpoll()
{
	UCSR0A = 0;
	UCSR0B = (1 << RXEN0);				/* do RX*/
}

static void usart_dis()
{
	UCSR0B = 0;
	(void)UDR0;
}

static uint8_t dbgtx[64];
static uint8_t dbgpos;

static void dbg_wr(uint8_t what)
{
	cli();
	if (dbgpos < sizeof(dbgtx))
		dbgtx[dbgpos++] = what;
	SPCR = (1 << SPIE) | (1 << SPE);
	sei();
}

ISR(SIG_SPI)
{
	if (dbgpos) {
		SPDR = dbgtx[0];
		for (uint8_t c = 0; c < sizeof(dbgtx); c++)
			dbgtx[c] = dbgtx[c + 1];
		dbgpos--;
	} else {
		SPDR = 0xff;
		SPCR = (1 << SPE);
	}
}

static void dbg_init(void)
{
	DDRB |= B_MISO;
	/* MSB first, cpol = rise,fall, cpha = sample(r),setup(f) */
	SPCR = (1 << SPIE) | (1 << SPE);
}

static volatile uint8_t statecntr = 0;

#define mayabort if (TIFR0 & (1 << TOV0)) return bit;
#define _wait_CLK(cond) while(cond) { mayabort; }
#define wait_CLKlo _wait_CLK(  PIND /* & p0 & p1 & p2 */ & D_CLK)
#define wait_CLKhi _wait_CLK(!(PIND /* & p0 & p1 & p2 */ & D_CLK))
#define wait_CLK wait_CLKhi; wait_CLKlo; _delay_us(15)
#define wait_CLKb

#define wait_CLK_set wait_CLKlo
#define wait_CLK_samp wait_CLKhi

static void timer_return(void)
{
	TCNT0 = 0;
	TIFR0 = (1 << TOV0);
	__asm__ volatile("nop\n");
	TIMSK0 = (1 << TOIE0);
}

static void timer_clear(void)
{
	TCNT0 = 0;
	__asm__ volatile("nop\n");
	TIFR0 = (1 << TOV0);
}

static uint16_t do_send_byte(uint8_t byte)
{
	uint8_t bit = 0, parity = 1, rv, usarts;

	usart_dis();

	_delay_us(5);

	/* make clock low, request clock from keyboard */
	PORTD &= ~D_CLK;
	DDRD |= D_CLK;

	_delay_us(166);

	PORTD &= ~D_DATA;
	DDRD |= D_DATA;

	// _delay_us(3);

	DDRD &= ~D_CLK;
	PORTD |= D_CLK;

	wait_CLK_samp;

	/* data bits */
	for (bit = 0; bit < 8; bit++) {
		wait_CLK_set;
		if (byte & 1) {
			PORTD |= D_DATA;
			parity ^= 1;
		} else {
			PORTD &= ~D_DATA;
		}
		byte >>= 1;
		wait_CLK_samp;
	}

	timer_clear();

	bit = 0x10;
	/* parity */
	wait_CLK_set;
	if (parity)
		PORTD |= D_DATA;
	else
		PORTD &= ~D_DATA;
	wait_CLK_samp;

	bit = 0x11;
	/* stop bit */
	wait_CLK_set;
	PORTD |= D_DATA;
	wait_CLK_samp;
	DDRD &= ~D_DATA;

#if 0
	bit = 0x12;
	/* ACK from keyboard */
	wait_CLK_set;
	wait_CLK_samp;
#endif

	bit = 0x14;
	while (PIND & D_DATA) { mayabort; }
	bit = 0x15;
	while (!(PIND & D_DATA)) { mayabort; }

	wait_CLKhi;

	/* response from keyboard */

	timer_clear();
	bit = 0x16;
	usart_rxpoll();

	usarts = 0;
	while (!(usarts & ((1 << RXC0) | (1 << UPE0) | (1 << FE0)))) {
		__asm__ volatile("nop\nnop\n");
		usarts = UCSR0A;
		if (TIFR0 & (1 << TOV0)) {
			TIFR0 = (1 << TOV0);
			if (++bit == 0x27)
				return bit;
		};
	}

	rv = UDR0;
	return rv | 0x100;
}

static uint8_t send_byte(uint8_t byte)
{
	uint16_t rv;
	uint8_t attempts;

	/* stop timer, use for ourselves to enforce 8 ms timeout */
	TIMSK0 = 0;

	for (attempts = 5; attempts; attempts--) {
		TCNT0 = 0;
		__asm__ volatile("nop\n");
		TIFR0 = (1 << TOV0);

		rv = do_send_byte(byte);
		if (rv == 0x1fa)
			goto out;

		/* clear state, wait, retry */
		DDRD &= ~(D_DATA | D_CLK);
		PORTD |= D_DATA | D_CLK;

		if (rv == 0x1fe)
			_delay_ms(33);
	}

	dbg_wr(0x01);
	dbg_wr(0x80 | (byte & 0x0f));
	dbg_wr(0x80 | (byte >> 4));

out:
	/* hand back timer to state machine */
	timer_return();
	usart_rx();
	return rv;
}

static uint8_t wait_byte(void)
{
	uint8_t data, usarts;

	usart_rxpoll();
	/* stop timer, use for ourselves to enforce 8 ms timeout */
	TIMSK0 = 0;
	TCNT0 = 0;
	TIFR0 |= (1 << TOV0);

	usarts = 0;
	while (!(usarts & ((1 << RXC0) | (1 << UPE0) | (1 << FE0)))) {
		if (TIFR0 & (1 << TOV0)) {
			(void)UDR0;
			timer_return();
			usart_rx();

			return 0;
		}

		__asm__ volatile("nop\nnop\n");
		usarts = UCSR0A;
	}

	data = UDR0;
	timer_return();
	usart_rx();

	return data;
}

#define KBLED_STATE 0x02
#define KBLED_ERROR 0x04
#define KBLED_OK    0x01

#define CNTRTOP		122

#define ENTER_FAIL	1
#define WAIT_FAIL	5
#define WAIT_POWERUP	3
#define WAIT_INIT	3
#define WAIT_IDLE	3

#define WAIT_IDLEBLINK	1	/* no full cycle */
#define CNTR_BLINK	6
#define CNTR_ERROR	61

#define WAIT_INPUT	5
#define WAIT_ACCEPT	5
#define WAIT_REJECT	10

static uint8_t cntr = 0;

#ifdef KILLSWITCH
static uint8_t error;
#endif

static const char passwd[sizeof(PIN) - 1] = PIN;
static char code[sizeof(PIN)];

static void state_enter(void)
{
	switch (state) {
	case STATE_NONE:
	case STATE_FAILURE:
		statecntr = WAIT_FAIL;
		usart_dis();
		power_down();
		break;
	case STATE_POWERUP:
		statecntr = WAIT_POWERUP;
		power_up();
		usart_rx();
		break;
	case STATE_INITRESET:
		statecntr = WAIT_INIT;
		send_byte(0xff);
		break;
	case STATE_CONFIG:
		/* statecntr not used */
		nextstate = STATE_FAILURE;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(0x00) != 0xfa)
			break;
		/* identify */
		if (send_byte(0xf2) != 0xfa)
			break;
		if (wait_byte() != 0xab)
			break;
		if (wait_byte() != 0x83)
			break;
#if 0
		/* scan code set 3 */
		if (send_byte(0xf0) != 0xfa)
			break;
		if (send_byte(0x03) != 0xfa)
			break;
		/* make codes only */
		if (send_byte(0xf9) != 0xfa)
			break;
#endif
		nextstate = STATE_IDLE;
		break;
	case STATE_IDLE:
		statecntr = WAIT_IDLE;
		nextstate = STATE_FAILURE;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(0x00) != 0xfa)
			break;
		nextstate = STATE_NONE;
		break;
	case STATE_IDLEBLINK:
		statecntr = WAIT_IDLEBLINK;
		nextstate = STATE_FAILURE;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(KBLED_STATE) != 0xfa)
			break;
		nextstate = STATE_NONE;
		cntr = CNTR_BLINK;
		break;
	case STATE_INPUT:
		statecntr = WAIT_INPUT;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(KBLED_STATE) != 0xfa)
			break;
		break;
	case STATE_ACCEPT:
		statecntr = WAIT_ACCEPT;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(KBLED_OK) != 0xfa)
			break;
		break;
	case STATE_REJECT:
		statecntr = WAIT_REJECT;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(KBLED_ERROR) != 0xfa)
			break;
		break;
#ifdef KILLSWITCH
	case STATE_ERROR:
		statecntr = 1;
		cntr = CNTR_ERROR;
		error ^= KBLED_ERROR;
		if (send_byte(0xed) != 0xfa)
			break;
		if (send_byte(error) != 0xfa)
			break;
		break;
#endif
	}
}

static void state_timeout(void)
{
	switch (state) {
	case STATE_NONE:
	case STATE_FAILURE:
		state = STATE_POWERUP;
		break;
	case STATE_POWERUP:
		state = STATE_INITRESET;
		break;
	case STATE_INITRESET:
	case STATE_CONFIG:
		state = STATE_FAILURE;
		break;
	case STATE_IDLE:
		state = STATE_IDLEBLINK;
		break;
	case STATE_INPUT:
		memset(&code, 0, sizeof(code));
	case STATE_IDLEBLINK:
	case STATE_ACCEPT:
	case STATE_REJECT:
		state = STATE_IDLE;
		break;
#ifdef KILLSWITCH
	case STATE_ERROR:
		state = STATE_ERROR;
		break;
#endif
	}
	state_enter();
}

ISR(SIG_OVERFLOW0)
{
	if (!--cntr) {
		cntr = CNTRTOP;
		if (statecntr)
			statecntr--;
	}
}

#define ESC	0x1b
#define ENT	0x0d

#define KBC_BASE 0x16
const PROGMEM char kbc[] = {
/*	 0    1    2    3    4    5    6    7
 *	 8    9    a    b    c    d    e    f
 */
	                              '1', '_', /* 10 - 17 */
	'_', '_', '_', '_', '_', '_', '2', '_', /* 18 - 1f */
	'_', '_', '_', '_', '_', '4', '3', '_', /* 20 - 27 */
	'_', '_', '_', '_', '_', '_', '5', '_', /* 28 - 2f */
	'_', '_', '_', '_', '_', '_', '6', '_', /* 30 - 37 */
	'_', '_', '_', '_', '_', '7', '8', '_', /* 38 - 3f */
	'_', '_', '_', '_', '_', '0', '9', '_', /* 40 - 47 */
	'_', '_', '_', '_', '_', '_', '_', '_', /* 48 - 4f */
	'_', '_', '_', '_', '_', '_', '_', '_', /* 50 - 57 */
	'_', '_', ENT, '_', '_', '_', '_', '_', /* 58 - 5f */
	'_', '_', '_', '_', '_', '_', '_', '_', /* 60 - 67 */
	'_', '1', '_', '4', '7', '_', '_', '_', /* 68 - 6f */
	'0', '_', '2', '5', '6', '8', ESC, ESC, /* 70 - 77 */
	'_', '_', '3', '_', '_', '9'            /* 78 - 7f */
};

#define NUMPAD_ENTER 0xda	/* e0 5a */

static uint8_t pressed = 0, e0 = 0, release = 0;

static void handle_keypress(uint8_t data)
{
	uint8_t unlock, lock;
	uint8_t ascii = '_';
	uint8_t c;

	if (release) {
		pressed = 0;
		release = 0;
		return;
	}
	if (data == pressed)
		return;

	if (data == 0xe0) {
		e0 = 0x80;
		return;
	}
	if (data == 0xf0) {
		release = 1;
		return;
	}
	if (data >= 0x80)
		return;

	pressed = data;

	data |= e0;
	e0 = 0;

	if (data >= KBC_BASE && data < KBC_BASE + sizeof(kbc))
		ascii = pgm_read_byte(kbc + data - KBC_BASE);

	dbg_wr(0x03);
	dbg_wr(0x80 | (ascii & 0xf));
	dbg_wr(0x80 | (ascii >> 4));

	lock = ascii == ESC;
	unlock = ascii == ENT || data == NUMPAD_ENTER;

	if (lock || unlock) {
		/* passwd:  a  b  c  d
		 * code:   \0  a  b  c  d
		 */
#ifdef KILLSWITCH
		if (code[0] || !memcmp("9164", code + 1, 4)) {
			error = 0;
			nextstate = STATE_ERROR;
			return;
		}
#endif
		if (code[0] || memcmp(passwd, code + 1, sizeof(passwd))) {
			dbg_wr(0x20);
			nextstate = STATE_REJECT;
		} else {
			dbg_wr(lock ? 0x21 : 0x22);
			nextstate = STATE_ACCEPT;
		}
		memset(&code, 0, sizeof(code));
		return;
	}

	for (c = 0; c < sizeof(code) - 1; c++)
		code[c] = code[c + 1];
	code[c] = ascii;

	statecntr = WAIT_INPUT;
	nextstate = STATE_INPUT;
}

ISR(SIG_USART_RECV)
{
	uint8_t data = UDR0;

	dbg_wr(0x80 | (data & 0x3f));
	dbg_wr(0x84 | (data >> 6));

	switch (state) {
	case STATE_POWERUP:
	case STATE_INITRESET:
		if (data == 0xaa)
			nextstate = STATE_CONFIG;
		break;
	case STATE_IDLE:
	case STATE_IDLEBLINK:
	case STATE_INPUT:
		handle_keypress(data);
	default:
		break;
	}
}

int main()
{
	dbg_init();

	/* /256 = 31'250 Hz = 32 µs per 1 unit
	 * /256 = 122 Hz = 8'192 µs per for overflow
	 * /122 = 1,0006 Hz = 1 s per CNTRTOP */
	TCCR0A = 0;
	TIMSK0 = (1 << TOIE0);
	TCCR0B = (1 << CS02);

	UCSR0C = (1 << UMSEL00)				/* synch mode */
		| (1 << UPM01) | (1 << UPM00)		/* odd parity */
		| (1 << UCSZ01) | (1 << UCSZ00)		/* 8-bit chars */
		| (0 << UCPOL0);			/* polarity: sample on falling */

	state = STATE_FAILURE;
	nextstate = STATE_NONE;
	state_enter();

	for (int i = 0; i < 5000; i++) {
		__asm__ volatile("nop\nnop\n");
	}

	sei();
	while (1) {
		if (nextstate != STATE_NONE) {
			state = nextstate;
			nextstate = STATE_NONE;
			state_enter();
		} else if (!statecntr) {
			state_timeout();
		}
	}
}