#include <avr/io.h>
#define  F_CPU 16000000UL //Our CPU speed (16MHz)
#include <util/delay.h> //Libraries for delay and interrupt utilities
#include <avr/interrupt.h>
#define command 0 //explained in dispSend() function
#define write 1

uint8_t upperBuff[16] , downerBuff[16], overMsgUpper[] = "Score: ", overMsgDowner[] = "Best: ", scoremsg[] = "Score:" , din[] = {0x0E, 0x17, 0x1E, 0x1F, 0x18, 0x1F, 0x1A, 0x12}, cact[] = {0x04, 0x05, 0x15, 0x15, 0x16, 0x0C, 0x04, 0x04};
        //Buffers for line one and two. Message to display after lost game.                     //Score text during game. //Dinosaur and cactus bitmaps
uint8_t canup = 1, longhold = 0, distance = 6, speed = 200, isup = 0, dontprint = 0; //All of these are explained further
uint16_t aVal = 0, score = 1, bestscore = 0;
int i;

void dispInit();
void dispWrite(uint8_t bits);
void dispSend(uint8_t bits, uint8_t act);
void dispSetLine(uint8_t line);
void dispClear();
void dispHome();
void dispPrintChar(uint8_t chr[], uint8_t size);
uint16_t aRead();

void setup() {
  for(i = 0; i < 17; i++) downerBuff[i] = ' '; //Initialize upper and downward buffer
  for(i = 0; i < 17; i++) upperBuff[i] = ' ';

  dispInit(); //Initialize the display

  TCCR1B |= (1 << WGM12) | (1 << CS11); //Set Timer1 to compare to OCR1A and prescaler of 8
  OCR1AH = (500 >> 8); //This equals to 2000Hz or 500us timing, look for TIMER1_COMPA_vect down below
  OCR1AL = 500;
  TIMSK1 |= (1 << OCIE1A); //Enable Timer1 CompA ISR
  sei(); //Enable global interrupt


  ADMUX = (1 << REFS0); //Set AREF to VCC
  ADCSRA = (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0) | (1 << ADEN); //set ADC prescaler to 128 and enable ADC (defaulted to free running mode)

}

void loop() {
  ADMUX |= (1 << MUX2) | (1 << MUX0); //Set pin from ADMUX to ADC5 (floating)
    srand(aRead()); //Use it as a random seed
    ADMUX &= ~(1 << MUX2) & ~(1 << MUX0); //Revert back to ADC0 to read the button value

    if(aRead() > 900) longhold = 0; //Reads if Up button has been released to prevent cheating. The value is so low because if you hold your fingers beneath one of the buttons the voltage would drop, this prevents the dinosaur from locking up

    for(i = 0; i < 16; i++) downerBuff[i] = downerBuff[i + 1]; //Shifts everything in downward buffer by one place to the left
     if((rand() % 100) > (rand() % 100) && !dontprint){ //This portion decides if it should put a cactus or a blank spot, dontprint is used to prevent cactus grouping
      downerBuff[15] = 0x01; //0x01 represents the cactus (we added cactus and dinosaur to CGRAM when we initialized the display)
      dontprint = 1; //This part acts both as a boolean and a counter to ensure cactus separation
     }
     else downerBuff[15] = ' ';
     char lastchar = downerBuff[3]; //We remember the whats initially added to the downward buffer before replacing it with the dinosaur
     if(!isup){ //If din should be placed down
      downerBuff[3] = 0x00; //Place it down
      dispSetLine(2);
      dispPrintChar(downerBuff, sizeof(downerBuff)); //Draw it
      downerBuff[3] = lastchar; //Place back previous thing to the buffer
      canup = 1;  //This flag is used to disable dinosaur from getting up before it was drawn down, in this case he can go up
    } else { //If din should be placed up
      upperBuff[3] = 0x00; //Place it up in upper buff
      dispSetLine(1);
      dispPrintChar(upperBuff, sizeof(upperBuff));
      dispSetLine(2);
      dispPrintChar(downerBuff, sizeof(downerBuff)); //Draw it
      canup = 0; //In this case he wont go up until rendered on line 2
    }

    if(dontprint) dontprint++;
    if(dontprint > distance) dontprint = 0; //This is the part that ensures cactus separation, it will keep the cactus 3-5 spaces apart minimally (depends on the game progress)

    if(isup) isup++; //This part makes sure din is on upper side for 3 loops after he was initially drawn there
    if(isup > 4){
     upperBuff[3] = ' ';
     dispSetLine(1);
     dispPrintChar(upperBuff, sizeof(upperBuff));
     isup = 0;
    }
    for(i = 0; i < sizeof(scoremsg); i++) upperBuff[i + 5] = scoremsg[i]; //This part prints the current score during the game
    uint8_t cnt = 11;
    for(i = 10000; i > 0; i /= 10){
      upperBuff[cnt] = ((score / i) % 10) + '0';
      cnt++;
      dispSetLine(1);
      dispPrintChar(upperBuff, sizeof(upperBuff));
    }

    score++; //Increment the score once on loop
    if(score > bestscore) bestscore = score; //Remember best score

    if(lastchar == 0x01 && !isup){ //Check if the dinosaur is downward and hit a cactus
      dispClear(); //Clear the display and buffers
      for(i = 0; i < 17; i++) downerBuff[i] = ' ';
      for(i = 0; i < 17; i++) upperBuff[i] = ' ';
      uint8_t cnt;

      dispSetLine(1);
      for(i = 0; i < sizeof(overMsgUpper); i++) upperBuff[i] = overMsgUpper[i]; //Display worst and best score
      cnt = sizeof(overMsgUpper) - 1;
      for(i = 10000; i > 0; i /= 10){
        upperBuff[cnt] = ((score / i) % 10) + '0';
        cnt++;
      }
      dispPrintChar(upperBuff, sizeof(upperBuff));

      dispSetLine(2);
      for(i = 0; i < sizeof(overMsgDowner); i++) downerBuff[i] = overMsgDowner[i];
      cnt = sizeof(overMsgDowner) - 1;
      for(i = 10000; i > 0; i /= 10){
        downerBuff[cnt] = ((bestscore / i) % 10) + '0';
        cnt++;
      }
      dispPrintChar(downerBuff, sizeof(downerBuff));

      while(1){ //Wait for select button to be pressed
        aVal = aRead();
        if(aVal > 635 && aVal < 645){ //After that clear all the variables
          for(i = 0; i < 17; i++) downerBuff[i] = ' ';
          dispSetLine(1);
          dispPrintChar(downerBuff, sizeof(downerBuff));
          for(i = 0; i < 17; i++) upperBuff[i] = ' ';
          dispSetLine(2);
          dispPrintChar(upperBuff, sizeof(upperBuff));
          dontprint = 0;
          isup = 0;
          score = 1;
          speed = 200;
          longhold = 0;
          distance = 6;
          canup = 1;
          break;
             }
      }

    }
        if(score % 5 == 0) speed -=2; //If score is divisible by 5 make game faster by -2ms
    if(speed < 85) speed = 85; //Minimal time in ms (+ ~2ms) that the loop will be halted for (limited by display refreshing, in my testing 11.8Hz was readable enough to be playable)
    if(score % 175 == 0) distance--; //Every time you score a number divisible by 175 minimal cactus distance gets smaller
    if(distance < 4) distance = 4;
    for(i = 0; i < speed; i++) _delay_ms(1); //This is the only way as the compiler expects a const number here
}

void dispInit(){
  _delay_ms(50); //Just in case
  DDRD = 0b11110000; //Set these pins to output. PD4 - PD7 correspond to D4 - D7 on display, we need to configure it to run in 4 bit mode
  DDRB = 0b00000011; //PB0 is tied to RS and PB1 to EN
  dispWrite(0x30);//*This part here is explained in Hitachi HD44780 datasheet on how to initialize the display in 4bit mode
  _delay_us(4500);//*Essentially you send the reset signal 3 times, and then set it to 4 bit mode
  dispWrite(0x30);//*
  _delay_us(4500);//*
  dispWrite(0x30);//*
  _delay_us(4500);//*
  dispWrite(0x28);//*
  dispSend(0x28, command); //Send 4bit mode function set
  dispSend(0x08, command); //Turn the display off
  dispSend(0x01, command); //Clear its RAM (if MCU resets that doesn't mean the display was reset, so we clear everything)
    _delay_ms(50);
  dispSend(0x0C, command); //Turn the display on
  _delay_ms(5);
  dispSend(0x40, command); //Tell the display we want to enter a custom character to its CGRAM (on address 0x00)
  for(i=0; i<8; i++) dispSend(din[i], write);
  dispSend(0x80, command); //Transaction end
  dispSend(0x48, command); //Same thing, but for 0x01
  for(i=0; i<8; i++) dispSend(cact[i], write);
  dispSend(0x80, command);
}

void dispPrintChar(uint8_t chr[], uint8_t size){
  for(uint8_t i = 0; i < size; i++) dispSend(chr[i], write); //Self explanatory
}

void dispSetLine(uint8_t line){
  if(line == 2) dispSend(0xC0, command); //Sets the line where 0xC0 is line 2 and 0x80 is line 1
  else dispSend(0x80, command);
}

void dispClear(){
  dispSend(0x01, command); //Self explanatory
  _delay_ms(2); //This command takes longer for the IC to process, this delay is necessary
}

void dispHome(){ //This function isn't used in this application but its there for expandability, it places the cursor on the line 1 column 1
  dispSend(0x02, command); //Self explanatory
  _delay_ms(2);
}

void dispSend(uint8_t bits, uint8_t act){
  if(act) PORTB |= (1 << DDB0); //Set PB0 if we are writing a character, else pull it low
  else PORTB &= ~(1<<DDB0);
  dispWrite(bits); //Send the bit then shift them 4 bit to the left to work in displays 4bit mode
  dispWrite(bits << 4);
  _delay_us(80);
}

void dispWrite(uint8_t bits){
  PORTD = bits; //This is a dirty way to write it but it's perfect for this application as it's not bulky and PORTD isn't used for anything else anyway
  PORTB |= (1<<DDB1); //Pulse the PB1 to signal the IC to read the data
  _delay_us(1);
  PORTB &= ~(1<<DDB1);
  _delay_us(1);
}

uint16_t aRead(){
  ADCSRA |= (1 << ADSC); //This signal the avr to read the ADC value
  while  (ADCSRA & (1 << ADSC)); //Wait until it's finished
  return ADCL | (ADCH << 8); //Send it back stitched together
}

ISR (TIMER1_COMPA_vect){ //Timer ISR we set up earlier
  if(!longhold){ //Return if the Up button was still held
    aVal = aRead(); //Read from ADC0
    if(aVal > 95 && aVal < 104 && canup){ //Check if Up is pressed and that din was rendered down
     isup = 1;
     longhold++;
     }
    }
}