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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// ===== ENUM =====
enum Personality { CUTE, LAZY, TSUNDERE, CURIOUS };
enum Expression { IDLE, HAPPY, ANGRY, SLEEPY, SURPRISED, LOOK_LEFT, LOOK_RIGHT };
enum EmotionState { STATE_IDLE, STATE_REACT, STATE_HOLD, STATE_DECAY };

Personality currentPersonality = CUTE;
Expression currentExp = IDLE;
Expression targetExp = IDLE;
EmotionState emoState = STATE_IDLE;

unsigned long emoTimer = 0;

// ===== EYE STRUCT =====
struct Eye {
  float baseX, baseY;
  float x, y;
  float w, h;
  float pupilX, pupilY;
  float targetX, targetY;
  float vx, vy;
  float squish;
};

Eye leftEye  = {40, 32, 40, 32, 30, 20, 0, 0, 40, 32, 0, 0, 0};
Eye rightEye = {88, 32, 88, 32, 30, 20, 0, 0, 88, 32, 0, 0, 0};

// ===== PHYSICS PARAM =====
float getStiffness() {
  switch(currentPersonality) {
    case CUTE: return 0.12;
    case LAZY: return 0.05;
    case TSUNDERE: return 0.15;
    case CURIOUS: return 0.2;
  }
  return 0.1;
}

float getDamping() {
  switch(currentPersonality) {
    case CUTE: return 0.85;
    case LAZY: return 0.9;
    case TSUNDERE: return 0.75;
    case CURIOUS: return 0.7;
  }
  return 0.8;
}

// ===== UPDATE EYE =====
void updateEye(Eye &e) {
  float stiffness = getStiffness();
  float damping = getDamping();

  float ax = (e.targetX - e.x) * stiffness;
  float ay = (e.targetY - e.y) * stiffness;

  e.vx = (e.vx + ax) * damping;
  e.vy = (e.vy + ay) * damping;

  float centerForce = 0.02;
  e.vx += (e.baseX - e.x) * centerForce;
  e.vy += (e.baseY - e.y) * centerForce;

  e.x += e.vx;
  e.y += e.vy;

  e.x = constrain(e.x, e.baseX - 10, e.baseX + 10);
  e.y = constrain(e.y, e.baseY - 6, e.baseY + 6);

  float speed = abs(e.vx) + abs(e.vy);
  e.squish = speed * 0.3;
  if (e.squish > 3) e.squish = 3;
}

// ===== EXPRESSION =====
void applyExpression(Expression exp) {
  leftEye.w = rightEye.w = 30;
  leftEye.h = rightEye.h = 20;
  leftEye.pupilX = rightEye.pupilX = 0;
  leftEye.pupilY = rightEye.pupilY = 0;

  switch(exp) {
    case HAPPY:
      leftEye.h = rightEye.h = 14;
      break;

    case ANGRY:
      leftEye.pupilX = -4;
      rightEye.pupilX = 4;
      leftEye.h = rightEye.h = 12;
      break;

    case SLEEPY:
      leftEye.h = rightEye.h = 6;
      leftEye.pupilY = 2;
      rightEye.pupilY = 2;
      break;

    case SURPRISED:
      leftEye.w = rightEye.w = 36;
      leftEye.h = rightEye.h = 30;
      break;

    case LOOK_LEFT:
      leftEye.pupilX = rightEye.pupilX = -6;
      break;

    case LOOK_RIGHT:
      leftEye.pupilX = rightEye.pupilX = 6;
      break;

    default:
      break;
  }
}

// ===== EXPRESSION ENGINE =====
void triggerExpression(Expression exp) {
  targetExp = exp;
  emoState = STATE_REACT;
  emoTimer = millis();
}

void updateExpression() {
  switch(emoState) {
    case STATE_REACT:
      applyExpression(targetExp);
      if (millis() - emoTimer > 200) {
        emoState = STATE_HOLD;
        emoTimer = millis();
      }
      break;

    case STATE_HOLD:
      if (millis() - emoTimer > 800) {
        emoState = STATE_DECAY;
        emoTimer = millis();
      }
      break;

    case STATE_DECAY:
      applyExpression(IDLE);
      if (millis() - emoTimer > 500) {
        emoState = STATE_IDLE;
      }
      break;

    case STATE_IDLE:
      applyExpression(IDLE);
      break;
  }
}

// ===== IDLE BEHAVIOR =====
void idleBehavior(Eye &e) {
  int rangeX = 8;
  int rangeY = 4;

  if (random(0,100) < 3) {
    e.targetX = e.baseX + random(-rangeX, rangeX);
    e.targetY = e.baseY + random(-rangeY, rangeY);
  }
}

// ===== MICRO EXPRESSION =====
void microExpression() {
  if (random(0,1000) < 5) {
    triggerExpression(SURPRISED);
  }
}

// ===== DRAW =====
void drawEye(Eye e) {
  int w = e.w + e.squish;
  int h = e.h - e.squish;

  display.fillRoundRect(e.x - w/2, e.y - h/2, w, h, 8, WHITE);

  int px = e.x + e.pupilX + e.vx * 2;
  int py = e.y + e.pupilY + e.vy * 2;

  display.fillCircle(px, py, 3, BLACK);
}

// ===== SETUP =====
void setup() {
  delay(100);
  Wire.begin(8, 9);
  Wire.setClock(400000);

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
}

// ===== LOOP =====
unsigned long lastFrame = 0;
#define FRAME_TIME 20

void loop() {
  if (millis() - lastFrame < FRAME_TIME) return;
  lastFrame = millis();

  updateExpression();
  microExpression();

  idleBehavior(leftEye);
  idleBehavior(rightEye);

  updateEye(leftEye);
  updateEye(rightEye);

  display.fillRect(0,0,128,64,BLACK);

  drawEye(leftEye);
  drawEye(rightEye);

  display.display();
}