#include <CapacitiveSensor.h>

// After adding the code for checking the last touched pad,
// there were not enough memory for the display, so I disabled
// the code for the screen temporarily
//#define SCREEN

#ifdef SCREEN
#include <Adafruit_SSD1306.h>
#define W 128
#define H 64
#define ADDR 0x3C
Adafruit_SSD1306 display(W, H);
#endif

CapacitiveSensor pads[] = {
  { 2, 3 }, { 2, 4 }, { 2, 5 }, { 2, 6 },
  { 2, 7 }, { 2, 8 }, { 2, 9 }, { 2, 10 },
  { 2, 11 }, { 2, 12 },
};
#define array_len(a) (sizeof(a) / sizeof *(a))

void setup() {
  Serial.begin(9600);
  Serial.println();
  pinMode(13, OUTPUT);

#ifdef SCREEN
  if (!display.begin(SSD1306_SWITCHCAPVCC, ADDR)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);  // Don't proceed, loop forever
  }
  Serial.println(F("Init display"));
  display.setTextColor(WHITE);
  display.setTextSize(2);
#endif
}

unsigned long last_touch_time[array_len(pads)] = {};

void loop() {
  unsigned long start = millis();

  int last_touched = -1;
  for (int i = 0; i < array_len(pads); ++i) {
    long val = pads[i].capacitiveSensor(30);
    Serial.print(i);
    Serial.print(": ");
    Serial.print(val);
    Serial.print("\t");

    bool current = val > 200;
    if (current) {
      if (last_touch_time[i] == 0) {
        last_touch_time[i] = millis();
      }
      if (last_touched < 0 || last_touch_time[last_touched] < last_touch_time[i]) {
        last_touched = i;
      }
    } else {
      last_touch_time[i] = 0;
    }
  }
  Serial.println();

  if (last_touched < 0) {
    noTone(13);
  } else {
    tone(13, 300 + last_touched * 100);
  }

  unsigned long processing_time = millis() - start;

  Serial.print(F("Last touched: "));
  Serial.println(last_touched);
  Serial.println(processing_time);

#ifdef SCREEN
  display.clearDisplay();
  display.setCursor(0, 0);
  if (last_touched < 0) {
    display.println(F("No touch"));
  } else {
    display.print(F("Touched "));
    display.println(last_touched);
  }
  display.print(F("T:"));
  display.println(processing_time);
  display.display();
#endif
}