#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <string.h>
#define F_CPU 12000000UL  // 12 MHz

/*
 * Valve data
 */
typedef enum {
  VALVE_CLOSED =0,
  VALVE_OPENED,
  VALVE_HOLDING,
} ValveState;

typedef struct {
  ValveState state;
  int msHold;
  int msStart;
} ValveData;

#define VALVE_COUNT 6

ValveData valves[VALVE_COUNT];
int pwmState;

/*
 * Timer setup
 */
#define CYCLES_PER_MS (F_CPU / 1000UL)

#define CLOCKS_PER_MS 187

#define MS_START 10

void configureTimer() {
  // TIMER 0
  // Set prescaler to 1/64
  // 187 cycles per ms
  // no output compare match pin
  // output compare register A triggers interrupt
  TCCR0A = 0x00; // compare
  TCCR0B = 0x03; // prescaler at 1/64
  TCNT0  = 0x00; // initial cycle at 0
  OCR0A  = CLOCKS_PER_MS;
  TIMSK0 = 0x02; // interrupt on match A
  // TIMER 1
  // Set prescaler to 1/16
  // 750 cycles per ms
  // no output compare match pin
  // output compare register A triggers interrupt
  TCCR1A = 0x00; // compare
  TCCR1B = 0x01; // prescaler at 1/8
  TCNT1  = 0x00; // initial cycle at 0
  OCR1A  = 100; // 8 PWM cycles/ms
  TIMSK1 = 0x02; // interrupt on match A
}

/*
 * Serial setup
 */
#define FLAG_PENDING_COMMAND 0x01
char flags = 0;

#define RX_BUF_SIZE 64
char rxBuf[RX_BUF_SIZE];
int rxOffset;

#define TX_BUF_SIZE 448
char txBuf[TX_BUF_SIZE];

char* pNextTx = NULL;

void openValve( unsigned char valve );
void closeValve( unsigned char valve );
void dispense( unsigned char valve, unsigned int ms );

void dispense( unsigned char valve, unsigned int ms ) {
  if ( valve < VALVE_COUNT ) {
    openValve( valve );
    valves[valve].state = VALVE_OPENED;
    if ( ms > MS_START ) {
      valves[valve].msStart = MS_START;
      valves[valve].msHold = ms - MS_START;
    } else {
      valves[valve].msStart = ms;
      valves[valve].msHold = 0;
    }
  }
}

void configureSerial() {
  // Setting to 9600 baud, 8N1.
  // 9600 baud: U2X = 0, UBRR = 71
  UBRR0H = 0;
  UBRR0L = 77;
  UCSR0A = 0;
  // enable TX/RX
  UCSR0B = (1<<RXCIE0) | (1<<RXEN0) | (1<<TXEN0);
  // 8 bits, no parity, 1 stop bit
  UCSR0C = (1<<UCSZ01) | (1<<UCSZ00);
  rxOffset = 0;
}

void putString( char* pStr ) {
  pNextTx = pStr;
  UCSR0B |= (1 << UDRIE0);
}

void processCommand()
{
  flags &= ~FLAG_PENDING_COMMAND;
  rxBuf[RX_BUF_SIZE-1] = '\0';
  char* pR = rxBuf;
  if ( *(pR++) != '+' ) return;
  if (strncmp("valve", pR, 5) == 0) {
    pR += 5;
    int v = *(pR++)-'a';
    if ( v < 0 || v >= 6 ) {
      putString( "Valve out of range" );
    }
    int whole = 0;
    int fract = 0;
    int frsig = 100;
    while (*pR >= '0' && *pR <= '9' ) {
      whole = (whole * 10) + (*(pR++) - '0');
    }
    if ( *pR == '.' ) {
      pR++;
      while (*pR >= '0' && *pR <= '9' ) {
	fract += frsig * (*(pR++) - '0');
	frsig /= 10;
      }
    }
    if ( *pR == '-' ) {
      dispense( v, whole*1000 + fract );
    }
    else
    {
      putString( "No terminator" );
    }
  }
}


/*
 * PC0-5 Configure as digital outputs for driving
 */
void configurePins()
{
  PORTC  = 0x00;
  DDRC   = 0x3f;  // Set C0-C5 as outputs
}

void openValve( unsigned char valve ) {
  if ( valve < 6 ) {
    PORTC |= 0x01 << valve;
  }
}

void closeValve( unsigned char valve ) {
  if ( valve < 6 ) {
    PORTC &= (0xff) ^ (0x01 << valve);
  }
}

void init()
{
  int i;

  cli();
  configurePins();
  configureSerial();
  set_sleep_mode( SLEEP_MODE_IDLE );
  for ( i = 0; i < VALVE_COUNT; i++ ) {
    valves[i].state = VALVE_CLOSED;
    valves[i].msHold = 0;
    valves[i].msStart = 0;
  }
  pwmState = 0;
  configureTimer();
  sei();
}

ISR(USART_RX_vect)
{  
  rxBuf[ rxOffset ] = UDR0;
  if ( rxBuf[ rxOffset ] == '\n' ) {
    rxBuf[ rxOffset ] = '\0';
    flags |= FLAG_PENDING_COMMAND;
    rxOffset = 0;
  } else {
    rxOffset = (rxOffset+1) % RX_BUF_SIZE;
  }
}

ISR(USART_UDRE_vect)
{
  if (pNextTx == 0 || *pNextTx == '\0') {
    UCSR0B &= ~(1 << UDRIE0);
  } else {
    UDR0=*pNextTx;
    pNextTx++;
  }
}

ISR( TIMER0_COMPA_vect ) {
  int i;
  for ( i = 0; i < VALVE_COUNT; i++ ) {
    if ( valves[i].state == VALVE_OPENED ) {
      if ( valves[i].msStart == 0 ) {
	valves[i].state = VALVE_HOLDING;
      } else {
	valves[i].msStart--;
      }
    } 
    if ( valves[i].state == VALVE_HOLDING ) {
      if ( valves[i].msHold == 0 ) {
	closeValve(i);
	valves[i].state = VALVE_CLOSED;
      } else {
	valves[i].msHold--;
      }
    }
  }
}

ISR( TIMER1_COMPA_vect ) {
  int i;
  pwmState=(pwmState==0)?1:0;
  for ( i = 0; i < VALVE_COUNT; i++ ) {
    if ( valves[i].state == VALVE_HOLDING ) {
      if ( pwmState == 0 ) {
	closeValve( i );
      } else {
	openValve( i );
      }
    }
  }
}

int main( void )
{
  init();
  putString( "Initialized.\n" );
  while (1) {
    //sleep_cpu();
    if ( (flags & FLAG_PENDING_COMMAND) != 0 ) {
      processCommand();
    }
  }
  return 0;
}