// +build avr

package machine

import (
	"device/avr"
)

type GPIOMode uint8

const (
	GPIO_INPUT = iota
	GPIO_OUTPUT
)

// LED on the Arduino
const LED = 13

func (p GPIO) Configure(config GPIOConfig) {
	if config.Mode == GPIO_OUTPUT { // set output bit
		if p.Pin < 8 {
			*avr.DDRD |= 1 << p.Pin
		} else {
			*avr.DDRB |= 1 << (p.Pin - 8)
		}
	} else { // configure input: clear output bit
		if p.Pin < 8 {
			*avr.DDRD &^= 1 << p.Pin
		} else {
			*avr.DDRB &^= 1 << (p.Pin - 8)
		}
	}
}

func (p GPIO) Set(value bool) {
	if value { // set bits
		if p.Pin < 8 {
			*avr.PORTD |= 1 << p.Pin
		} else {
			*avr.PORTB |= 1 << (p.Pin - 8)
		}
	} else { // clear bits
		if p.Pin < 8 {
			*avr.PORTD &^= 1 << p.Pin
		} else {
			*avr.PORTB &^= 1 << (p.Pin - 8)
		}
	}
}

// Get returns the current value of a GPIO pin.
func (p GPIO) Get() bool {
	if p.Pin < 8 {
		val := *avr.PIND & (1 << p.Pin)
		return (val > 0)
	} else {
		val := *avr.PINB & (1 << (p.Pin - 8))
		return (val > 0)
	}
}

// InitPWM initializes the registers needed for PWM.
func InitPWM() {
	// use waveform generation
	*avr.TCCR0A |= avr.TCCR0A_WGM00

	// set timer 0 prescale factor to 64
	*avr.TCCR0B |= avr.TCCR0B_CS01 | avr.TCCR0B_CS00

	// set timer 1 prescale factor to 64
	*avr.TCCR1B |= avr.TCCR1B_CS11

	// put timer 1 in 8-bit phase correct pwm mode
	*avr.TCCR1A |= avr.TCCR1A_WGM10

	// set timer 2 prescale factor to 64
	*avr.TCCR2B |= avr.TCCR2B_CS22

	// configure timer 2 for phase correct pwm (8-bit)
	*avr.TCCR2A |= avr.TCCR2A_WGM20
}

// Configure configures a PWM pin for output.
func (pwm PWM) Configure() {
	if pwm.Pin < 8 {
		*avr.DDRD |= 1 << pwm.Pin
	} else {
		*avr.DDRB |= 1 << (pwm.Pin - 8)
	}
}

// Set turns on the duty cycle for a PWM pin using the provided value. On the AVR this is normally a
// 8-bit value ranging from 0 to 255.
func (pwm PWM) Set(value uint16) {
	value8 := value >> 8
	switch pwm.Pin {
	case 3:
		// connect pwm to pin on timer 2, channel B
		*avr.TCCR2A |= avr.TCCR2A_COM2B1
		*avr.OCR2B = avr.RegValue(value8) // set pwm duty
	case 5:
		// connect pwm to pin on timer 0, channel B
		*avr.TCCR0A |= avr.TCCR0A_COM0B1
		*avr.OCR0B = avr.RegValue(value8) // set pwm duty
	case 6:
		// connect pwm to pin on timer 0, channel A
		*avr.TCCR0A |= avr.TCCR0A_COM0A1
		*avr.OCR0A = avr.RegValue(value8) // set pwm duty
	case 9:
		// connect pwm to pin on timer 1, channel A
		*avr.TCCR1A |= avr.TCCR1A_COM1A1
		// this is a 16-bit value, but we only currently allow the low order bits to be set
		*avr.OCR1AL = avr.RegValue(value8) // set pwm duty
	case 10:
		// connect pwm to pin on timer 1, channel B
		*avr.TCCR1A |= avr.TCCR1A_COM1B1
		// this is a 16-bit value, but we only currently allow the low order bits to be set
		*avr.OCR1BL = avr.RegValue(value8) // set pwm duty
	case 11:
		// connect pwm to pin on timer 2, channel A
		*avr.TCCR2A |= avr.TCCR2A_COM2A1
		*avr.OCR2A = avr.RegValue(value8) // set pwm duty
	default:
		panic("Invalid PWM pin")
	}
}

// ADC on the Arduino
const (
	ADC0 = 0
	ADC1 = 1
	ADC2 = 2
	ADC3 = 3
	ADC4 = 4
	ADC5 = 5
)

// InitADC initializes the registers needed for ADC.
func InitADC() {
	// set a2d prescaler so we are inside the desired 50-200 KHz range at 16MHz.
	*avr.ADCSRA |= (avr.ADCSRA_ADPS2 | avr.ADCSRA_ADPS1 | avr.ADCSRA_ADPS0)

	// enable a2d conversions
	*avr.ADCSRA |= avr.ADCSRA_ADEN
}

// Configure configures a ADCPin to be able to be used to read data.
func (a ADC) Configure() {
	return // no pin specific setup on AVR machine.
}

// Get returns the current value of a ADC pin. The AVR will return a 10bit value ranging
// from 0-1023.
func (a ADC) Get() uint16 {
	// set the analog reference (high two bits of ADMUX) and select the
	// channel (low 4 bits), masked to only turn on one ADC at a time.
	// this also sets ADLAR (left-adjust result) to 0 (the default).
	*avr.ADMUX = avr.RegValue(avr.ADMUX_REFS0 | (a.Pin & 0x07))

	// start the conversion
	*avr.ADCSRA |= avr.ADCSRA_ADSC

	// ADSC is cleared when the conversion finishes
	for ok := true; ok; ok = (*avr.ADCSRA & avr.ADCSRA_ADSC) > 0 {
	}

	low := uint16(*avr.ADCL)
	high := uint16(*avr.ADCH)
	return uint16(low) | uint16(high<<8)
}