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#include <avr/interrupt.h>

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#include "stdlib.h"

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#include "timer.h"

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void timer_init (void)

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{

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    TCCR1A = (

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            // OC1A output pin disconnected

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            0b00 << COM1A0

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            // OC1B output pin disconnected

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        |   0b00 << COM1B0

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            // no PWM

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        |   0b00 << WGM10

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    );

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    TCCR1B = (

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            // CTC mode

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            0b01 << WGM12

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    );

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    TCCR1C = 0;

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}

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static void timer1_set ()

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{

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    sbi(&TIMER_FLAGS, TIMER1_BUSY);

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}

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static void timer1_start (short cycles)

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{

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    // count up from zero...

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    TCNT1 = 0;

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    // ...to the given number of timer cycles

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    OCR1A = cycles;

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    // start!

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    timer1_set();

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    TIMSK1 = (

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            // OCA interrupt

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            0b1 << OCIE1A       // enable

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    );

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    TCCR1B = (

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            // WGM

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            0b01  << WGM12      // CTC

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            // clocksource

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        |   0b101 << CS10       // 1024'th

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    );

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}

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/*

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 * Keep the timer running, but clear the flag..

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 */

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static void timer1_clear ()

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{

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    cbi(&TIMER_FLAGS, TIMER1_BUSY);

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}

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/*

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 * Stop the timer at its current value.

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 */

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static void timer1_stop ()

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{

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    // WGM: normal

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    // clocksource: stop

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    TCCR1B = 0;

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    timer1_clear();

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}

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ISR(TIMER1_COMPA_vect)

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{

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    timer1_clear();

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    // cpu will wake up from sleep()

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}

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/*

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 * Sleep on timer1 interrupt.

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 *

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 * Starts fresh timer that sleeps given cycles if given, or continues on the running timer.

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 *

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 * Returns 1 on timeout, 0 on other interrupt.

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 */

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byte timer_sleep (unsigned cycles)

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{

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    if (cycles) {

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        // set fresh timer

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        timer1_start(cycles);

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    } else {

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        // wait for next cycle...

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        timer1_set();

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    }

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    // sleep while timer is running

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    // XXX: atomic?

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    if (tbi(&TIMER_FLAGS, TIMER1_BUSY)) {

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        // TODO: PRR

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        SMCR = (

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                // idle sleep

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                (0b00 << SM0)

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                // enable sleep

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            |   (0b1 << SE)

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        );

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        // sleep

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        __asm__ ( "sleep" :: );

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        // cleanup

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        SMCR = 0;

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    }

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    if (tbi(&TIMER_FLAGS, TIMER1_BUSY)) {

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        // interrupt

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        return 0;

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    } else {

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        // timeout

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        return 1;

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    }

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}