// Copyright 2012 Olivier Gillet.
//
// Author: Olivier Gillet (ol.gillet@gmail.com)
//
// This program 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.
// This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

#include <avr/eeprom.h>
#include <avr/pgmspace.h>

#include "avrlib/adc.h"
#include "avrlib/boot.h"
#include "avrlib/gpio.h"
#include "avrlib/watchdog_timer.h"

using namespace avrlib;

enum LedState {
  LED_STATE_OFF,
  LED_STATE_RED,
  LED_STATE_GREEN
};

Gpio<PortD, 4> in_1;
Gpio<PortD, 3> out_1_a;
Gpio<PortD, 0> out_1_b;
Gpio<PortD, 1> led_1_a;
Gpio<PortD, 2> led_1_k;

Gpio<PortD, 7> in_2;
Gpio<PortD, 6> out_2_a;
Gpio<PortD, 5> out_2_b;
Gpio<PortB, 1> led_2_a;
Gpio<PortB, 0> led_2_k;

Gpio<PortC, 2> switch_2;
Gpio<PortC, 3> switch_1;

Adc adc;

const uint16_t kLongPressTime = 6250;  // 800 * 8000 / 1024
const uint16_t kLedGateDelay = 0x1ff;

static uint8_t adc_channel;
static uint16_t p[2];

bool toggle_mode[2];
bool latch_mode[2];

bool input_state[2];
bool previous_state[2];

bool switch_state[2];
bool inhibit_switch[2];
uint16_t press_time[2];

uint8_t led_state[2];
uint16_t led_gate_delay[2];

uint32_t rng_state;

const prog_uint16_t linear_table[] PROGMEM = {
      0,     0,   259,   518,   777,  1036,  1295,  1554,
   1813,  2072,  2331,  2590,  2849,  3108,  3367,  3626,
   3885,  4145,  4404,  4663,  4922,  5181,  5440,  5699,
   5958,  6217,  6476,  6735,  6994,  7253,  7512,  7771,
   8030,  8289,  8548,  8807,  9066,  9325,  9584,  9843,
  10102, 10361, 10620, 10879, 11138, 11397, 11656, 11915,
  12174, 12434, 12693, 12952, 13211, 13470, 13729, 13988,
  14247, 14506, 14765, 15024, 15283, 15542, 15801, 16060,
  16319, 16578, 16837, 17096, 17355, 17614, 17873, 18132,
  18391, 18650, 18909, 19168, 19427, 19686, 19945, 20204,
  20463, 20723, 20982, 21241, 21500, 21759, 22018, 22277,
  22536, 22795, 23054, 23313, 23572, 23831, 24090, 24349,
  24608, 24867, 25126, 25385, 25644, 25903, 26162, 26421,
  26680, 26939, 27198, 27457, 27716, 27975, 28234, 28493,
  28753, 29012, 29271, 29530, 29789, 30048, 30307, 30566,
  30825, 31084, 31343, 31602, 31861, 32120, 32379, 32638,
  32897, 33156, 33415, 33674, 33933, 34192, 34451, 34710,
  34969, 35228, 35487, 35746, 36005, 36264, 36523, 36782,
  37042, 37301, 37560, 37819, 38078, 38337, 38596, 38855,
  39114, 39373, 39632, 39891, 40150, 40409, 40668, 40927,
  41186, 41445, 41704, 41963, 42222, 42481, 42740, 42999,
  43258, 43517, 43776, 44035, 44294, 44553, 44812, 45072,
  45331, 45590, 45849, 46108, 46367, 46626, 46885, 47144,
  47403, 47662, 47921, 48180, 48439, 48698, 48957, 49216,
  49475, 49734, 49993, 50252, 50511, 50770, 51029, 51288,
  51547, 51806, 52065, 52324, 52583, 52842, 53101, 53361,
  53620, 53879, 54138, 54397, 54656, 54915, 55174, 55433,
  55692, 55951, 56210, 56469, 56728, 56987, 57246, 57505,
  57764, 58023, 58282, 58541, 58800, 59059, 59318, 59577,
  59836, 60095, 60354, 60613, 60872, 61131, 61390, 61650,
  61909, 62168, 62427, 62686, 62945, 63204, 63463, 63722,
  63981, 64240, 64499, 64758, 65017, 65276, 65535, 65535,
};

void Init() {
  Gpio<PortB, 4>::set_mode(DIGITAL_OUTPUT);
  Gpio<PortB, 4>::Low();
  
  in_1.set_mode(DIGITAL_INPUT);
  in_2.set_mode(DIGITAL_INPUT);
  in_1.High();
  in_2.High();
  
  switch_1.set_mode(DIGITAL_INPUT);
  switch_2.set_mode(DIGITAL_INPUT);
  switch_1.High();
  switch_2.High();

  out_1_a.set_mode(DIGITAL_OUTPUT);
  out_1_b.set_mode(DIGITAL_OUTPUT);
  led_1_a.set_mode(DIGITAL_OUTPUT);
  led_1_k.set_mode(DIGITAL_OUTPUT);

  out_2_a.set_mode(DIGITAL_OUTPUT);
  out_2_b.set_mode(DIGITAL_OUTPUT);
  led_2_a.set_mode(DIGITAL_OUTPUT);
  led_2_k.set_mode(DIGITAL_OUTPUT);
  
  led_1_a.Low();
  led_2_a.Low();
  led_1_k.Low();
  led_2_k.Low();
  
  adc.Init();
  adc.set_reference(ADC_DEFAULT);
  adc.set_alignment(ADC_LEFT_ALIGNED);
  adc.StartConversion(0);
  
  uint8_t configuration_byte = ~eeprom_read_byte((uint8_t*) 0);
  toggle_mode[0] = configuration_byte & 1;
  latch_mode[0] = configuration_byte & 2;
  toggle_mode[1] = configuration_byte & 4;
  latch_mode[1] = configuration_byte & 8;
  
  led_state[0] = led_state[1] = 0;
  switch_state[0] = switch_state[1] = false;
  
  TCCR1A = 0;
  TCCR1B = 5;
}

bool Read(uint8_t channel) {
  return channel == 0 ? !in_1.value() : !in_2.value();
}

bool ReadSwitch(uint8_t channel) {
  return channel == 0 ? !switch_1.value() : !switch_2.value();
}

void GateOn(uint8_t channel, bool outcome) {
  if (channel == 0) {
    if (outcome) {
      out_1_a.Low();
      out_1_b.High();
    } else {
      out_1_a.High();
      out_1_b.Low();
    }
  } else {
    if (outcome) {
      out_2_a.Low();
      out_2_b.High();
    } else {
      out_2_a.High();
      out_2_b.Low();
    }
  }
}

void GateOff(uint8_t channel) {
  if (channel == 0) {
    out_1_a.Low();
    out_1_b.Low();
  } else {
    out_2_a.Low();
    out_2_b.Low();
  }
}

void LedOff(uint8_t channel) {
  if (channel == 0) {
    led_1_a.Low();
    led_1_k.Low();
  } else {
    led_2_a.Low();
    led_2_k.Low();
  }
}

void DisplayConfigurationAndSave(uint8_t channel) {
  uint8_t configuration_byte = 0;
  if (toggle_mode[0]) configuration_byte |= 1;
  if (latch_mode[0]) configuration_byte |= 2;
  if (toggle_mode[1]) configuration_byte |= 4;
  if (latch_mode[1]) configuration_byte |= 8;
  eeprom_write_byte((uint8_t*) 0, ~configuration_byte);
}

int main(void) {
  ResetWatchdog();
  Init();

  input_state[0] = input_state[1] = false;
  rng_state = 1;
  while (1) {
    // Whenever an ADC cycle is finished, update the probability variables.
    if (adc.ready()) {
      uint8_t channel_index = 1 - adc_channel;  // ADC pins are swapped!
      p[channel_index] = pgm_read_word(linear_table + adc.ReadOut8());
      adc_channel = (adc_channel + 1) & 1;
      adc.StartConversion(adc_channel);
    }
    
    // Scan switches
    for (uint8_t i = 0; i < 2; ++i) {
      bool new_input_state = ReadSwitch(i);
      if (!switch_state[i] && new_input_state) {
        press_time[i] = TCNT1;
        inhibit_switch[i] = false;
      }
      if (switch_state[i] && !inhibit_switch[i]) {
        uint16_t this_press_time = TCNT1 - press_time[i];
        if (this_press_time >= kLongPressTime) {
          inhibit_switch[i] = true;
          latch_mode[i] = !latch_mode[i];
          DisplayConfigurationAndSave(i);
        } else if (this_press_time >= 64 && !new_input_state) {
          toggle_mode[i] = !toggle_mode[i];
          DisplayConfigurationAndSave(i);
        }
      }
      switch_state[i] = new_input_state;
    }
    
    // Scan inputs
    uint32_t random_words = rng_state;
    for (uint8_t i = 0; i < 2; ++i) {
      bool new_input_state = Read(i);
      
      if (new_input_state || latch_mode[i]) {
        // Hold the LED while the trigger is high or when in latch mode
        led_gate_delay[i] = kLedGateDelay;
      }
      
      if (new_input_state && !input_state[i] /* Rising edge */) {
        uint16_t random = random_words & 0xffff;
        uint16_t threshold = p[i];
        bool outcome = random >= threshold && threshold != 65535;
        if (toggle_mode[i]) {
          outcome = outcome ^ previous_state[i];
        }
        previous_state[i] = outcome;
        GateOn(i, outcome);
        led_state[i] = outcome ? 1 : 2;
      } else if (!new_input_state && input_state[i] && !latch_mode[i]) {
        GateOff(i);
      }
      input_state[i] = new_input_state;
      random_words >>= 16;
      
      if (led_gate_delay[i]) {
        --led_gate_delay[i];
        if (!led_gate_delay[i]) {
          led_state[i] = 0;
        }
      }
    }
    
    // Refresh LEDs
    if (led_state[0] == 0) {
      led_1_a.Low();
      led_1_k.Low();
    } else if (led_state[0] == 1) {
      led_1_a.Low();
      led_1_k.High();
    } else {
      led_1_a.High();
      led_1_k.Low();
    }
    
    if (led_state[1] == 0) {
      led_2_a.Low();
      led_2_k.Low();
    } else if (led_state[1] == 1) {
      led_2_a.Low();
      led_2_k.High();
    } else {
      led_2_a.High();
      led_2_k.Low();
    }

    // rng_state = rng_state * 1664525 + 1013904223;
    rng_state = (rng_state >> 1) ^ (-(rng_state & 1u) & 0xD0000001u);
  }
}