#include <libopencm3/stm32/i2c.h>
#include <errno.h>

#include "eeprom.h"

/* wait for I2C status register flags to appear */
static bool i2c_wait(uint32_t i2c, uint32_t sr1, uint32_t sr2)
{
	unsigned int i;

	for (i = 0; i < 1000000; i++) {
		if (((I2C_SR1(i2c) & sr1) == sr1) &&
		    ((I2C_SR2(i2c) & sr2) == sr2))
			return true;
	}
	return false;
}

int eeprom_read(uint8_t *buf_out, unsigned int num_bytes, uint16_t read_addr)
{
	unsigned int i;

	if (num_bytes > 255)
		return -EINVAL; /* no reload cycles yet */

	i2c_send_start(I2C1);

	/* Wait for the end of the start condition, master mode selected, and BUSY bit set */
	if (!i2c_wait(I2C1, I2C_SR1_SB, I2C_SR2_MSL|I2C_SR2_BUSY))
		return -EIO;

	/* Send Address, wait until it is transferred */
	i2c_send_7bit_address(I2C1, 0x50, I2C_WRITE);
	if (!i2c_wait(I2C1, I2C_SR1_ADDR, 0))
		return -EIO;

	/* Send memory address */
#if 0 /* 16bit address */
	i2c_send_data(I2C1, read_addr >> 8);
	if (!i2c_wait(I2C1, I2C_SR1_BTF, 0))
		return -EIO;
#endif
	i2c_send_data(I2C1, read_addr & 0xff);
	if (!i2c_wait(I2C1, I2C_SR1_BTF, 0))
		return -EIO;

	/* re-start */
	i2c_send_start(I2C1);
	i2c_enable_ack(I2C1);

	/* Wait for the end of the start condition, master mode selected, and BUSY bit set */
	if (!i2c_wait(I2C1, I2C_SR1_SB, I2C_SR2_MSL|I2C_SR2_BUSY))
		return -EIO;

	/* Send Address, wait until it is transferred */
	i2c_send_7bit_address(I2C1, 0x50, I2C_READ);
	if (!i2c_wait(I2C1, I2C_SR1_ADDR, 0))
		return -EIO;

	for (i = 0; i < num_bytes; i++) {
		if (i == num_bytes - 1)
			i2c_disable_ack(I2C1);
		if (!i2c_wait(I2C1, I2C_SR1_RxNE, 0))
			return -EIO;
		buf_out[i] = i2c_get_data(I2C1);
	}

	i2c_send_stop(I2C1);

	return i;
}

static int wait_write_complete(void)
{
	unsigned int i;

	for (i = 0; i < 100; i++) {
		i2c_send_start(I2C1);
		/* Wait for the end of the start condition, master mode selected, and BUSY bit set */
		if (!i2c_wait(I2C1, I2C_SR1_SB, I2C_SR2_MSL|I2C_SR2_BUSY))
			return -EIO;
		/* Send Address, wait until it is transferred */
		i2c_send_7bit_address(I2C1, 0x50, I2C_WRITE);
		if (i2c_wait(I2C1, I2C_SR1_ADDR, 0)) {
			/* slave has sent an ACK, we may proceed */
			return 0;
		}
		i2c_send_stop(I2C1);
	}
}

int eeprom_write_byte(uint16_t write_addr, uint8_t byte)
{
	i2c_send_start(I2C1);

	/* Wait for the end of the start condition, master mode selected, and BUSY bit set */
	if (!i2c_wait(I2C1, I2C_SR1_SB, I2C_SR2_MSL|I2C_SR2_BUSY))
		return -EIO;

	/* Send Address, wait until it is transferred */
	i2c_send_7bit_address(I2C1, 0x50, I2C_WRITE);
	if (!i2c_wait(I2C1, I2C_SR1_ADDR, 0))
		return -EIO;

	/* Send memory address */
#if 0 /* 16bit address */
	i2c_send_data(I2C1, write_addr >> 8);
	if (!i2c_wait(I2C1, I2C_SR1_BTF, 0))
		return -EIO;
#endif
	i2c_send_data(I2C1, write_addr & 0xff);
	if (!i2c_wait(I2C1, I2C_SR1_BTF, 0))
		return -EIO;

	/* Send data to write */
	i2c_send_data(I2C1, byte);
	if (!i2c_wait(I2C1, I2C_SR1_BTF, 0))
		return -EIO;

	i2c_send_stop(I2C1);

	wait_write_complete();

	return 1;
}