/*
  interrupt.c - replacement for the avr library of the same name to provide
  dummy register variables

  Part of Grbl Simulator

  Copyright (c) 2012 Jens Geisler

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "interrupt.h"
#include "io.h"
#include "wdt.h"

//pseudo-Interrupt vector table
isr_fp compa_vect[6]={0};
isr_fp compb_vect[6]={0};
isr_fp ovf_vect[6]={0};
isr_fp wdt_vect = 0;
isr_fp pc_vect = 0;

void sei() {io.sreg|=SEI;}
void cli() {io.sreg&=~SEI;}



int16_t sim_scaling[8]={0,1,8,64,256,1024,1,1}; //clock scalars
//Timer/Counter modes:  these are incomplete, but enough for this application
enum sim_wgm_mode {
  wgm_NORMAL,
  wgm_CTC,
  wgm_FAST_PWM,
  wgm_PHASE_PWM,
  wgm_PH_F_PWM,
  wgm_RESERVED
};

//3-bit wgm table for 8-bit timers
enum sim_wgm_mode sim_wgm_3[] = {wgm_NORMAL,wgm_PHASE_PWM,wgm_CTC,wgm_FAST_PWM,
                                 wgm_RESERVED,wgm_PHASE_PWM, wgm_RESERVED, wgm_FAST_PWM};

//4-bit wgm modes for 16-bit timers
enum sim_wgm_mode sim_wgm_4[16] = {wgm_NORMAL,wgm_PHASE_PWM,wgm_PHASE_PWM,wgm_PHASE_PWM,
                                   wgm_CTC, wgm_FAST_PWM, wgm_FAST_PWM, wgm_FAST_PWM,
                                   wgm_PH_F_PWM, wgm_PH_F_PWM, wgm_PHASE_PWM, wgm_PHASE_PWM,
                                   wgm_CTC, wgm_RESERVED, wgm_FAST_PWM, wgm_FAST_PWM};

static const uint16_t timer_bitdepth[SIM_N_TIMERS] = {
  0xFF,0xFFFF,0xFF,
  //0xFFFF,0xFFFF,0xFFFF   3 more for mega
};

void timer_interrupts() {
  int i;
  uint8_t ien = io.sreg&SEI;  //interrupts enabled?
  io.prescaler++;

  //all clocks
  for (i=0;i<SIM_N_TIMERS;i++){
    uint8_t cs = io.tccrb[i]&7; //clock select bits
    int16_t increment = sim_scaling[cs];
    uint16_t bitmask = timer_bitdepth[i];

    //check scaling to see if timer fires
    if (increment && (io.prescaler&(increment-1))==0) { 

    //select waveform generation mode
    enum sim_wgm_mode mode;
    if (i==0 || i==2) {  //(T0 and T2 use only 3 wgm bits)
      uint8_t wgm = ((io.tccrb[i]&0x08)>>1) | (io.tccra[i]&3);
      mode = sim_wgm_3[wgm];
    }
    else {
      uint8_t wgm = ((io.tccrb[i]&0x18)>>1) | (io.tccra[i]&3);  //4 wgm bits
      mode = sim_wgm_4[wgm];
    }

    //tick
    if (io.tifr[i]&(1<<SIM_ROLL)) {  //handle CTC mode rollover
      io.tcnt[i]=0;
      io.tifr[i]&=~(1<<SIM_ROLL);
    }
    else {
      io.tcnt[i]++;
    }
    io.tcnt[i]&=bitmask; //limit the 8 bit timers

    switch (mode) {
      case wgm_NORMAL: //Normal mode, ovf on rollover
        if (io.tcnt[i]==0) io.tifr[i]|=(1<<SIM_TOV);  //overflow
       break;

        case wgm_CTC: //CTC mode, ovf at TOP, 0 next tick
        if (io.tcnt[i]==(io.ocra[i]&bitmask)) {
          io.tifr[i]|=(1<<SIM_TOV)|(1<<SIM_ROLL);  //overflow
        }
       break;
        default:  //unsupported
       break;
    }

    //comparators
    if ((io.timsk[i]&(1<<SIM_OCA)) && io.tcnt[i]==(io.ocra[i]&bitmask)) io.tifr[i]|=(1<<SIM_OCA);
    if ((io.timsk[i]&(1<<SIM_OCB)) && io.tcnt[i]==(io.ocrb[i]&bitmask)) io.tifr[i]|=(1<<SIM_OCB);
    if ((io.timsk[i]&(1<<SIM_OCC)) && io.tcnt[i]==(io.ocrc[i]&bitmask)) io.tifr[i]|=(1<<SIM_OCC);

    //call any triggered interupts
    if (ien && io.tifr[i]) {
      if (compa_vect[i] && (io.tifr[i]&(1<<SIM_OCA))) {
       compa_vect[i]();
       io.tifr[i]&=~(1<<SIM_OCA);
       //TODO: insert port_monitor call here
      }
      if (compb_vect[i] && (io.tifr[i]&(1<<SIM_OCB))) {
       compb_vect[i]();
       io.tifr[i]&=~(1<<SIM_OCB);
      }
      if (ovf_vect[i] && (io.tifr[i]&(1<<SIM_TOV))) {
       ovf_vect[i]();
       io.tifr[i]&=~(1<<SIM_TOV);
      }
    }
   }
  }
   //// TODO for more complete timer sim.
   // pwm modes. (only used for variable spindle, I think).
    // -- would require fixing wgm mode for Timers1..5
    // -- phase correct modes need updown counter.
    // output pins (also only for variable spindle, I think).

    //// Other chip features not needed yet for grbl:
   // writes to TCNT0 prevent compare match (need write detector.)
    // force output compare (unused)
    // input capture (unused and how would we signal it?)
    // define the other output compare registers.
   // usercode can clear unhandled interrupt flags by writing 1.
    //  --(this may be impossible, since bit was 1 before the write.)
    // prescaler reset.
    // maybe need to cli on interrupt entry

}