#include <Wire.h>
#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>
#include <Adafruit_SSD1306.h>

const char* ssid = "Wokwi-GUEST";

// 🔴 PASTE YOUR ACTIVE LOCALTUNNEL OR HUGGING FACE URL HERE
const char* serverUrl = "https://petite-places-fetch.loca.lt"; 

Adafruit_SSD1306 display(128, 64, &Wire, -1);
const int WINDOW_SIZE = 1500; // Full 30-second clinical scan at 50Hz
float ppg_buffer[WINDOW_SIZE];
int sample_idx = 0;

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  display.setTextColor(WHITE);
  
  WiFi.begin(ssid, "");
  while(WiFi.status() != WL_CONNECTED) delay(500);
  Serial.println("WiFi Connected! Starting 30s Edge-Computing Scan...");
}

void processAndSend() {
  display.clearDisplay();
  display.setCursor(0,10);
  display.setTextSize(1);
  display.println("Processing Math...");
  display.display();
  Serial.println("\n[1] Finalizing 1,500 points and standardizing...");
  
  // 1. Calculate Mean and StdDev for Standardization
  float sum = 0;
  for(int i=0; i<WINDOW_SIZE; i++) sum += ppg_buffer[i];
  float mean = sum / WINDOW_SIZE;

  float sq_sum = 0;
  for(int i=0; i<WINDOW_SIZE; i++) {
    sq_sum += pow(ppg_buffer[i] - mean, 2);
  }
  float stdev = sqrt(sq_sum / WINDOW_SIZE);
  if (stdev == 0) stdev = 0.00001; // Prevent division by zero

  // 2. Estimate HR using a basic peak detector
  int peaks = 0;
  float threshold = mean + (stdev * 0.5); 
  for(int i=1; i<WINDOW_SIZE-1; i++) {
    if(ppg_buffer[i] > ppg_buffer[i-1] && ppg_buffer[i] > ppg_buffer[i+1] && ppg_buffer[i] > threshold) {
      peaks++;
    }
  }
  
  // 30 seconds of data. Multiply peaks by 2 for Beats Per Minute (BPM)
  float calculated_hr = peaks * 2.0; 
  if (calculated_hr < 40) calculated_hr = 40.0; 
  if (calculated_hr > 220) calculated_hr = 220.0; 

  // 3. Prepare the 2D JSON Array
  // 32000 bytes optimized for the ESP32 RAM limit
  DynamicJsonDocument doc(32000); 
  JsonArray signal = doc.createNestedArray("signal");
  JsonArray ppg_json = signal.createNestedArray();
  JsonArray hr_json = signal.createNestedArray();

  for(int i=0; i<WINDOW_SIZE; i++) {
    // Standardization: (x - mean) / stdev
    ppg_json.add((ppg_buffer[i] - mean) / stdev);
    
    // Heart Rate Normalization: (HR - 30) / (220 - 30)
    hr_json.add((calculated_hr - 30.0) / (220.0 - 30.0)); 
  }

  String body; 
  serializeJson(doc, body);

  display.clearDisplay();
  display.setCursor(0,10);
  display.println("Sending to AI...");
  display.display();
  Serial.println("[2] Firing HTTP POST over Tunnel...");
  
  HTTPClient http;
  http.setTimeout(30000); // 30 second timeout for the massive payload
  http.begin(serverUrl); 

  http.addHeader("Content-Type", "application/json");
  http.addHeader("Bypass-Tunnel-Reminder", "true"); 
  http.addHeader("User-Agent", "FibWatch-Medical-IoT");

  int code = http.POST(body);
  Serial.print("Server Response Code: "); Serial.println(code);

  if(code == 200 || code == 201) {
    display.clearDisplay();
    display.setCursor(0,10);
    display.setTextSize(2); 
    display.println("Data Sent!"); 
    display.display();
    delay(4000); 
  } else {
    Serial.println("Error: Could not reach your server.");
    display.clearDisplay();
    display.setCursor(0,10);
    display.println("SERVER ERROR");
    display.display();
    delay(3000);
  }
  http.end();
}

void loop() {
  Wire.requestFrom(0x22, 1);
  if(Wire.available()) {
    ppg_buffer[sample_idx++] = (float)Wire.read();
    
    // Update progress bar every 150 samples (10%)
    if(sample_idx % 150 == 0) {
      int prog = (sample_idx * 100) / WINDOW_SIZE;
      display.clearDisplay();
      display.setCursor(0,0);
      display.setTextSize(1);
      display.print("Scanning: "); display.print(prog); display.println("%");
      display.fillRect(0, 20, prog * 1.28, 10, 1);
      display.display();
    }

    if(sample_idx >= WINDOW_SIZE) { 
      processAndSend(); 
      sample_idx = 0; 
    }
  }
  delay(20); // 50Hz sampling rate
}