#include <stdlib.h>
#include <string.h>

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#include "serial.h"

#define SPI_SS         PB2
#define SPI_SCK        PB5
#define SPI_MISO       PB4
#define SPI_MOSI       PB3
#define SPI_DDR        DDRB
#define SPI_PORT       PORTB

#define RX_PIN         PB0
#define RX_DDR         DDRB
#define RX_PORT        PORTB
#define RX_PCIE        PCIE0
#define RX_PCINT       PCINT0
#define RX_PCMSK       PCMSK0
#define RX_PCINTVEC    PCINT0_vect

#define PAYLOAD_LEN    32

static inline uint8_t read_reg(uint8_t reg)
{
	SPI_PORT &= ~(1 << SPI_SS);
	SPDR = reg & 0x7F;
	while (!(SPSR & (1 << SPIF)))
		;
	SPDR = 0;
	while (!(SPSR & (1 << SPIF)))
		;
	SPI_PORT |= (1 << SPI_SS);

	return SPDR;
}

static inline void write_reg(uint8_t reg, uint8_t val)
{
	SPI_PORT &= ~(1 << SPI_SS);
	SPDR = reg | 0x80;
	while (!(SPSR & (1 << SPIF)))
		;
	SPDR = val;
	while (!(SPSR & (1 << SPIF)))
		;
	SPI_PORT |= (1 << SPI_SS);
}

static inline void radio_send(const char *data, uint8_t n)
{
	uint8_t i;

	// STDBY + ListenAbort mode
	write_reg(0x01, 0x04);
	while ((read_reg(0x27) >> 7) != 1)
		;

	SPI_PORT &= ~(1 << SPI_SS);
	SPDR = 0x00 | 0x80;
	while (!(SPSR & (1 << SPIF)))
		;
	for (i = 0; i < n; i++) {
		SPDR = data[i];
		while (!(SPSR & (1 << SPIF)))
			;
	}
	SPI_PORT |= (1 << SPI_SS);

	write_reg(0x01, 0x0C);
	while (!read_reg(0x28))
		;

	write_reg(0x01, 0x04);
	while ((read_reg(0x27) >> 7) != 1)
		;

	// enable ListenOn in STDBY mode
	write_reg(0x01, (read_reg(0x01) | 0x40));
}

static inline uint8_t radio_recv(char *buf, uint8_t n)
{
	uint8_t i;

	if ((read_reg(0x28) & 0x04))
	{
		write_reg(0x01, 0x04);
		while ((read_reg(0x27) >> 7) != 1)
			;

		SPI_PORT &= ~(1 << SPI_SS);
		SPDR = 0x00 | 0x7F;
		while (!(SPSR & (1 << SPIF)))
			;
		for (i = 0; i < n; i++) {
			SPDR = 0;		
			while (!(SPSR & (1 << SPIF)))
				;
			buf[i] = SPDR;
		}	

		SPI_PORT |= (1 << SPI_SS);
	}

	return len;
}

struct radio_cfg {
	uint8_t payload_len
}

static inline void radio_init(struct radio_cfg *cfg)
{
	SPI_DDR |= (1 << SPI_SS) | (1 << SPI_SCK) | (1 << SPI_MOSI);
	SPI_PORT |= (1 << SPI_SS);
	SPCR |= (1 << SPE) | (1 << MSTR);

	if (cfg->payload_len > 0)
		write_reg(0x38, cfg->payload_len);

	RX_DDR &= ~(1 << RX_PIN);
	PCICR |= (1 << RX_PCIE);
	RX_PCMSK |= (1 << RX_PCINT);
}

int main(void)
{
	struct radio_cfg cfg;

	const char *s = "hello";

	cfg.payload_len = PAYLOAD_LEN;

	serial_init();
	radio_init(&cfg);

	sei();

	for (;;) {
		radio_send(s, strlen(s));
		serial_write_line("sent data");
		_delay_ms(2000);
	}

	return 0;
}

ISR(RX_PCINTVEC)
{
	uint8_t n;

	const uint8_t buflen = 32;
	char buf[buflen];
	
	n = radio_recv(buf, buflen);
}