#include <util/delay.h>
#include "u8x8_avr.h"

#ifdef AVR_USE_HW_I2C
#include <avr-hw-i2c/i2cmaster.h>
#endif

#ifdef AVR_USE_HW_SPI

#ifndef SCK_DDR
#error "SCK_DDR must be defined externally, eg: -DSCK_DDR=DDRB, for atmega328p."
#endif

#ifndef SCK_BIT
#error "SCK_BIT must be defined externally, eg: -DSCK_BIT=5, for atmega328p."
#endif

#ifndef MOSI_DDR
#error "MOSI_DDR must be defined externally, eg: -DMOSI_DDR=DDRB, for atmega328p."
#endif

#ifndef MOSI_BIT
#error "MOSI_BIT must be defined externally, eg: -DMOSI_BIT=3, for atmega328p."
#endif

#endif

#define P_CPU_NS (1000000000UL / F_CPU)


#ifdef AVR_USE_HW_SPI
uint8_t u8x8_byte_avr_hw_spi (u8x8_t * u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr) {
  uint8_t *data;

  switch (msg) {
    case U8X8_MSG_BYTE_INIT:
      SCK_DDR |= _BV (SCK_BIT);
      MOSI_DDR |= _BV (MOSI_BIT);

      SPCR = (_BV (SPE) | _BV (MSTR));

      switch (u8x8->display_info->spi_mode) {
        case 0:
          break;
        case 1:
          SPCR |= _BV (CPHA);
          break;
        case 2:
          SPCR |= _BV (CPOL);
          break;
        case 3:
          SPCR |= _BV (CPOL);
          SPCR |= _BV (CPHA);
          break;
      };

      switch (F_CPU / u8x8->display_info->sck_clock_hz) {
        case 2:
          SPSR |= _BV (SPI2X);
          break;
        case 4:
          break;
        case 8:
          SPSR |= _BV (SPI2X);
          SPCR |= _BV (SPR0);
          break;
        case 16:
          SPCR |= _BV (SPR0);
          break;
        case 32:
          SPSR |= _BV (SPI2X);
          SPCR |= _BV (SPR1);
          break;
        case 64:
          SPCR |= _BV (SPR1);
          break;
        case 128:
          SPCR |= _BV (SPR1);
          SPCR |= _BV (SPR0);
          break;
      }

      u8x8_gpio_SetCS(u8x8, u8x8->display_info->chip_disable_level);
      break;
    case U8X8_MSG_BYTE_SET_DC:
      u8x8_gpio_SetDC(u8x8, arg_int);
      break;
    case U8X8_MSG_BYTE_START_TRANSFER:
      u8x8_gpio_SetCS(u8x8, u8x8->display_info->chip_enable_level);
      u8x8->gpio_and_delay_cb(u8x8, U8X8_MSG_DELAY_NANO, u8x8->display_info->post_chip_enable_wait_ns, NULL);
      break;
    case U8X8_MSG_BYTE_SEND:
      data = (uint8_t *) arg_ptr;
      while (arg_int > 0) {
          SPDR = (uint8_t) * data;
          while (!(SPSR & _BV (SPIF)));
          data++;
          arg_int--;
      }
      break;
    case U8X8_MSG_BYTE_END_TRANSFER:
      u8x8->gpio_and_delay_cb(u8x8, U8X8_MSG_DELAY_NANO, u8x8->display_info->pre_chip_disable_wait_ns, NULL);
      u8x8_gpio_SetCS(u8x8, u8x8->display_info->chip_disable_level);
      break;
    default:
      return 0;
  }
  
  return 1;
}
#endif

#ifdef AVR_USE_HW_I2C
uint8_t u8x8_byte_avr_hw_i2c(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr)
{
	uint8_t *data;
	switch(msg){
		case U8X8_MSG_BYTE_SEND:
			data = (uint8_t *)arg_ptr;
			while( arg_int-- )
				i2c_write(*data++);
			break;
		case U8X8_MSG_BYTE_INIT:
			i2c_init();
			break;
		case U8X8_MSG_BYTE_SET_DC:
			/* ignored for i2c */
			break;
		case U8X8_MSG_BYTE_START_TRANSFER:
			i2c_start_wait(u8x8_GetI2CAddress(u8x8)+I2C_WRITE);
			break;
		case U8X8_MSG_BYTE_END_TRANSFER:
			i2c_stop();
			break;
		default:
			return 0;
	}
	return 1;
}
#endif

uint8_t u8x8_avr_delay (u8x8_t * u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr) {
	uint8_t cycles;

	switch(msg) {
		case U8X8_MSG_DELAY_NANO:  // delay arg_int * 1 nano second
			// At 20Mhz, each cycle is 50ns, the call itself is slower.
			break;
		case U8X8_MSG_DELAY_100NANO:       // delay arg_int * 100 nano seconds
			// Approximate best case values...
			#define CALL_CYCLES 26UL
			#define CALC_CYCLES 4UL
			#define RETURN_CYCLES 4UL
			#define CYCLES_PER_LOOP 4UL

			cycles = (100UL * arg_int) / (P_CPU_NS * CYCLES_PER_LOOP);

			if (cycles > CALL_CYCLES + RETURN_CYCLES + CALC_CYCLES)
				break;

			__asm__ __volatile__ (
			  "1: sbiw %0,1" "\n\t"  // 2 cycles
			  "brne 1b":"=w" (cycles):"0" (cycles)  // 2 cycles
			);
			break;
		case U8X8_MSG_DELAY_10MICRO: // delay arg_int * 10 micro seconds
			while( arg_int-- ) _delay_us(10);
			break;
		case U8X8_MSG_DELAY_MILLI:  // delay arg_int * 1 milli second
			while( arg_int-- ) _delay_ms(1);
			break;
		default:
			return 0;
	}

	return 1;
}