#include <Arduino.h>

#define C 0
#define D 1
#define E 2
#define Db 3
#define Eb 4

// Mux control pins
const int MUX0_S0 = 0;
const int MUX0_S1 = 1;
const int MUX0_S2 = 2;
const int MUX0_S3 = 3;

const int MUX_CHN[16][4] = {
    {0, 0, 0, 0}, // channel 0
    {1, 0, 0, 0}, // channel 1
    {0, 1, 0, 0}, // channel 2
    {1, 1, 0, 0}, // channel 3
    {0, 0, 1, 0}, // channel 4
    {1, 0, 1, 0}, // channel 5
    {0, 1, 1, 0}, // channel 6
    {1, 1, 1, 0}, // channel 7
    {0, 0, 0, 1}, // channel 8
    {1, 0, 0, 1}, // channel 9
    {0, 1, 0, 1}, // channel 10
    {1, 1, 0, 1}, // channel 11
    {0, 0, 1, 1}, // channel 12
    {1, 0, 1, 1}, // channel 13
    {0, 1, 1, 1}, // channel 14
    {1, 1, 1, 1}  // channel 15
};

// Keyboard
const int KEY_R0 = 15;
const int KEY_R1 = 16;

// key #, pressed?
int keys[5][2] = {{C, 0}, {D, 0}, {E, 0}, {Db, 0}, {Eb, 0}};

String keyNames[5] = {
    "C",
    "D",
    "E",
    "Db",
    "Eb"
};

void setup() {
  pinMode(MUX0_S0, OUTPUT);
  pinMode(MUX0_S1, OUTPUT);
  pinMode(MUX0_S2, OUTPUT);
  pinMode(MUX0_S3, OUTPUT);

  digitalWrite(MUX0_S0, LOW);
  digitalWrite(MUX0_S1, LOW);
  digitalWrite(MUX0_S2, LOW);
  digitalWrite(MUX0_S3, LOW);

  pinMode(KEY_R0, INPUT_PULLDOWN);
  pinMode(KEY_R1, INPUT_PULLDOWN);

  Serial.begin(115200);
}

// in the future, Mux should be turned into a class,
// where, say, Mux1.readMux() would call this method
void setMux(int channel) {
  int controlPin[] = {MUX0_S0, MUX0_S1, MUX0_S2, MUX0_S3};
  // loop through the 4 sig
  for (int i = 0; i < 4; i++) {
    digitalWrite(controlPin[i], MUX_CHN[channel][i]);
  }
}

void toggleKey(int key, int state) {
  if (keys[key][1] != state) {
    keys[key][1] = state;
    if (state == 1) {
      Serial.print("Key ");
      Serial.print(keyNames[key]);
      Serial.println(" pressed.");
    } else {
      Serial.print("Key ");
      Serial.print(keyNames[key]);
      Serial.println(" released.");
    }
  }
}

void loop() {

    // select each mux line so far connected
  for (int i = 0; i < 3; i++) {
    delay(10);
    setMux(i); // set the current line (col), 0-2

        // read pins connected to uC
    int row0 = digitalRead(KEY_R0); // read row_0
    int row1 = digitalRead(KEY_R1); // read row_1

        // picture the first five-note cluster of a keyboard.
    if (i == 0) {
      toggleKey(E, row1);
    } else if (i == 1) {
      toggleKey(Eb, row0);
      toggleKey(D, row1);
    } else if (i == 2) {
      toggleKey(Db, row0);
      toggleKey(C, row1);
    }
  }
}