#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

const int gsrPin = A0;
int graphIndex = 0;
uint8_t graphBuffer[128];

void setup() {
  Serial.begin(9600);

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    while(true); // stop if OLED not found
  }

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.display();
}

void loop() {
  int gsr = analogRead(gsrPin);

  // Map reading to graph height (0–63)
  int h = map(gsr, 0, 1023, 63, 0);
  graphBuffer[graphIndex] = h;

  graphIndex++;
  if (graphIndex >= 128) graphIndex = 0;

  // Draw
  display.clearDisplay();

  // Display value
  display.setCursor(0, 0);
  display.print("GSR: ");
  display.print(gsr);

  // Draw graph (bottom strip)
  for (int x = 0; x < 128; x++) {
    int y = graphBuffer[(graphIndex + x) % 128];
    display.drawPixel(x, y, SSD1306_WHITE);
  }

  display.display();
  delay(30);
}