#include <uart.h>
#include <gpio.h>
#include <stddef.h>

/* Auxilary mini UART registers */
#define AUX_ENABLE      ((volatile unsigned int*)(MMIO_BASE + 0x00215004))
#define AUX_MU_IO       ((volatile unsigned int*)(MMIO_BASE + 0x00215040))
#define AUX_MU_IER      ((volatile unsigned int*)(MMIO_BASE + 0x00215044))
#define AUX_MU_IIR      ((volatile unsigned int*)(MMIO_BASE + 0x00215048))
#define AUX_MU_LCR      ((volatile unsigned int*)(MMIO_BASE + 0x0021504C))
#define AUX_MU_MCR      ((volatile unsigned int*)(MMIO_BASE + 0x00215050))
#define AUX_MU_LSR      ((volatile unsigned int*)(MMIO_BASE + 0x00215054))
#define AUX_MU_MSR      ((volatile unsigned int*)(MMIO_BASE + 0x00215058))
#define AUX_MU_SCRATCH  ((volatile unsigned int*)(MMIO_BASE + 0x0021505C))
#define AUX_MU_CNTL     ((volatile unsigned int*)(MMIO_BASE + 0x00215060))
#define AUX_MU_STAT     ((volatile unsigned int*)(MMIO_BASE + 0x00215064))
#define AUX_MU_BAUD     ((volatile unsigned int*)(MMIO_BASE + 0x00215068))

int is_uart_inited = 0;

/**
 * Set baud rate and characteristics (115200 8N1) and map to GPIO
 */
void uart_init()
{
  register unsigned int r;

  /* initialize UART */
  *AUX_ENABLE |= 1;       // enable UART1, AUX mini uart
  *AUX_MU_CNTL = 0;
  *AUX_MU_LCR  = 3;       // 8 bits
  *AUX_MU_MCR  = 0;
  *AUX_MU_IER  = 0;
  *AUX_MU_IIR  = 0xc6;    // disable interrupts
  *AUX_MU_BAUD = 270;    // 115200 baud
  /* map UART1 to GPIO pins */
  r = *GPFSEL1;
  r &= ~((7 << 12) | (7 << 15)); // gpio14, gpio15
  r |= (2 << 12) | (2 << 15);    // alt5
  *GPFSEL1 = r;
  *GPPUD = 0;            // enable pins 14 and 15
  r = 150; while (r--) { asm volatile("nop"); }
  *GPPUDCLK0 = (1 << 14) | (1 << 15);
  r = 150; while (r--) { asm volatile("nop"); }
  *GPPUDCLK0 = 0;        // flush GPIO setup
  *AUX_MU_CNTL = 3;      // enable Tx, Rx

  is_uart_inited = 1;
}

/**
 * Send a character
 */
void uart_send(unsigned int c)
{
  /* wait until we can send */
  do { asm volatile("nop"); } while (!(*AUX_MU_LSR & 0x20));
  /* write the character to the buffer */
  *AUX_MU_IO = c;
}

uint8_t uart_getb()
{
  uint8_t r;
  /* wait until something is in the buffer */
  do { asm volatile("nop"); } while (!(*AUX_MU_LSR & 0x01));
  /* read it and return */
  r = (uint8_t)(*AUX_MU_IO);

  return r;
}

/**
 * Receive a character
 */
char uart_getc()
{
  char r = (char)uart_getb();

  /* convert carrige return to newline */
  return r == '\r' ? '\n' : r;
}

/**
 * Display a string
 */
void uart_puts(const char *s)
{
  while (*s) {
    /* convert newline to carrige return + newline */
    if(*s == '\n')
      uart_send('\r');
    uart_send(*s++);
  }
}

/**
 * Display a binary value in hexadecimal
 */
void uart_hex(uint64_t d)
{
  unsigned int n;
  for (int c = 28; c >= 0; c -= 4) {
    // get highest tetrad
    n = (d >> c) & 0xF;
    // 0-9 => '0'-'9', 10-15 => 'A'-'F'
    n += n > 9 ? 0x37 : 0x30;
    uart_send(n);
  }
}

void uart_int(int d)
{
  unsigned int buf[11];
  int size = 0;
 
  if (d == 0) {
    uart_send((unsigned int)'0');
    return;
  }

  int is_neg = (d < 0);

  while (d != 0) {
    buf[size++] = '0' + d % 10;
    d /= 10;
  }

  if (is_neg)
    uart_send((unsigned int)'-');
  while (size--)
    uart_send(buf[size]);
}