// https://forum.arduino.cc/t/vu-meter-lcd-20x4/1403043

#include <LiquidCrystal.h>

byte Bar[8]          = {B11111, B00000, B11111, B11111, B11111, B11111, B00000, B11111};
byte L[8]            = {B00111, B01000, B10100, B10100, B10100, B10111, B01000, B00111};
byte R[8]            = {B00111, B01000, B10110, B10101, B10110, B10101, B01000, B00111};
byte EndMark[8]      = {B10000, B01000, B00100, B00100, B00100, B00100, B01000, B10000};
byte EmptyBar[8]     = {B11111, B00000, B00000, B00000, B00000, B00000, B00000, B11111};
byte peakHoldChar[8] = {B11111, B00000, B01110, B01110, B01110, B01110, B00000, B11111};
byte Smile1[8]       = {B00000, B00000, B00000, B00000, B00000, B00000, B10010, B00000};
byte Smile2[8]       = {B10010, B01100, B00000, B00000, B00000, B00000, B00000, B00000};

const int numReadings = 5;  //Refresh rate. Lower value = higher rate. 5 is the defaul
const int screenHeight = 4; // 4 rows
const int screenWidth = 20; // 20 columns

int left;                   //Variables to  store and calculate the channel levels
int indexL = 0;             //Actual channel index
int totalL = 0;             //Total  channel data
int maxL = 0;               //Maximal level
int inputPinL = A0;  //Input pin for LEFT  channel
int volL = 0;
int leftAvg = 0;
int leftPeak = 0;

int right;                   //Variables to  store and calculate the channel levels
int indexR = 0;             //Actual channel index
int totalR = 0;             //Total  channel data
int maxR = 0;               //Maximal level
int inputPinR = A1;  //Input pin for RIGHT  channel
int volR = 0;
int rightAvg = 0;
int rightPeak = 0;

long peakHoldTime = 1000;  //peak hold time in miliseconds
long peakHold = 0;
long decayTime = 0;
long actualMillis = 0;

LiquidCrystal lcd(12, 10, 5, 4, 3, 2);  //lcd configuration

void setup() {
  lcd.begin(20, 4);  //Setting up LCD. 16 chars and 2 rows
  lcd.createChar(1, Bar);
  lcd.createChar(2, L);
  lcd.createChar(3, R);
  lcd.createChar(4, EmptyBar);
  lcd.createChar(5, EndMark);
  lcd.createChar(6, peakHoldChar);
  lcd.createChar(7, Smile1);
  lcd.createChar(8, Smile2);
  drawLeftChannels();
  decayTime = millis();
}

void drawLeftChannels() {
  lcd.setCursor(0, 0);   //L channel index
  lcd.write(2);          //L  symbol
  lcd.setCursor(screenWidth / 2, screenHeight / 2 - 1);
  lcd.write(7);
  lcd.setCursor(screenWidth / 2, screenHeight / 2);
  lcd.write(8);
  lcd.setCursor(0, screenHeight - 1);   //R channel index
  lcd.write(3);          //R  symbol
  lcd.setCursor(screenWidth - 1, 0);  //closing tag / end mark index 1
  lcd.write(5);          //closing tag / end mark
  lcd.setCursor(screenWidth - 1, screenHeight - 1);  //closing tag / end mark index 1
  lcd.write(5);          //closing tag / end mark
}

void loop() {
  actualMillis = millis();

  // totalL = map(analogRead(inputPinL), 0, 1023, 1, screenWidth - 1);
  // totalR = map(analogRead(inputPinR), 0, 1023, 1, screenWidth - 1);
  totalL = analogRead(inputPinL);
  totalR = analogRead(inputPinR);
  //==========

  if (totalL > maxL) {
    maxL = totalL;
  } indexL++;

  if (totalR > maxR) {
    maxR = totalR;
  } indexR++;

  //==========

  if (indexL >= numReadings) {
    indexL = 0;
    left = maxL;
    maxL = 0;
  }

  if (indexR >= numReadings) {
    indexR = 0;
    right = maxR;
    maxR = 0;
  }

  //==========

  volL = left / 2;
  if (volL > 18) {
    volL = 18;
  }

  volR = right / 2;
  if (volR > 18) {
    volR = 18;
  }
  //==========

  if (volL < (leftAvg - 2)) {
    if (decayTime < actualMillis)
      leftAvg--;
    volL = leftAvg;
  } else if (volL > (leftAvg + 2)) {
    volL = (leftAvg + 2);
    leftAvg = volL;
  } else {
    leftAvg = volL;
  }
  if (volL > leftPeak) {
    leftPeak = volL;
  }

  if (volR < (rightAvg - 2)) {
    if (decayTime < actualMillis)
      rightAvg--;
    volR = rightAvg;
  } else if (volR > (rightAvg + 2)) {
    volR = (rightAvg + 2);
    rightAvg = volR;
  } else {
    rightAvg = volR;
  }
  if (volR > rightPeak) {
    rightPeak = volR;
  }

  //==========

  drawBar(volL, leftPeak, 0);
  drawBar(volR, rightPeak, screenHeight - 1);

  //==========

  if (decayTime < actualMillis)
    decayTime = (millis() + 50);
  if (peakHold < actualMillis) {
    peakHold = (millis() + peakHoldTime);
    leftPeak -= 1;
    // leftPeak = -1;
    rightPeak -= 1;
  }
}

void drawBar(int data, int peakData, int row) {
  if (peakData < 2) {
    peakData = -1;
  }
  for (int col = 1; col < 19; col++) {
    lcd.setCursor(col, row);
    if (col < data) {
      lcd.write(1);
    } else if (peakData == col) {
      lcd.write(6);  //write the peak marker
    } else {
      lcd.write(4);  //write  "empty"
    }
  }
}