#include <Arduino.h>
#include <Wire.h>
#include <WiFi.h>
#include <WebServer.h>
#include <SPIFFS.h>
#include <ESPmDNS.h>
#include <Adafruit_BME680.h>

#define SEALEVEL_HPA (1013.25f)   // adjust for better altitude accuracy

// ===== WiFi =====
const char* WIFI_SSID = "YOUR_SSID";
const char* WIFI_PASS = "YOUR_PASSWORD";
const char* MDNS_NAME = "sparrow";        // -> http://sparrow.local/

// ===== Web =====
WebServer server(80);

// ===== BME680 =====
Adafruit_BME680 bme;
bool haveBME = false;

// ===== History buffer (5 minutes @ 1 Hz) =====
static const size_t HISTORY_MAX = 300;

struct Sample {
  uint32_t t_ms;
  float tC;
  float hPct;
  float pHpa;
  float altM;
};

Sample hist[HISTORY_MAX];
size_t histHead = 0;
size_t histCount = 0;

void pushSample(const Sample& s) {
  hist[histHead] = s;
  histHead = (histHead + 1) % HISTORY_MAX;
  if (histCount < HISTORY_MAX) histCount++;
}

Sample getSampleByAge(size_t iOldToNew) {
  size_t idx = (histHead + HISTORY_MAX - histCount + iOldToNew) % HISTORY_MAX;
  return hist[idx];
}

// ===== Sensor init and reading =====
bool beginBME680() {
  Wire.begin(21, 22); // set custom SDA/SCL here if needed: Wire.begin(SDA, SCL);

  if (bme.begin(0x76, &Wire)) { Serial.println("[BME680] Found at 0x76"); return true; }
  if (bme.begin(0x77, &Wire)) { Serial.println("[BME680] Found at 0x77"); return true; }
  Serial.println("[BME680] Not found at 0x76/0x77");
  return false;
}

void setupBME680() {
  bme.setTemperatureOversampling(BME680_OS_8X);
  bme.setHumidityOversampling(BME680_OS_2X);
  bme.setPressureOversampling(BME680_OS_4X);
  bme.setIIRFilterSize(BME680_FILTER_SIZE_3);
  bme.setGasHeater(320, 150); // optional
}

bool takeAndStoreSample() {
  if (!haveBME) return false;
  if (!bme.performReading()) return false;

  Sample s;
  s.t_ms = millis();
  s.tC   = bme.temperature;
  s.hPct = bme.humidity;
  s.pHpa = bme.pressure / 100.0f;
  s.altM = bme.readAltitude(SEALEVEL_HPA);
  pushSample(s);
  return true;
}

// ===== HTTP handlers =====
void handleRoot() {
  File f = SPIFFS.open("/index.html", "r");
  if (!f) { server.send(500, "text/plain", "index.html missing"); return; }
  server.streamFile(f, "text/html");
  f.close();
}

void handleApiSensor() {
  if (histCount == 0) takeAndStoreSample();
  Sample s = (histCount == 0) ? Sample{millis(), NAN, NAN, NAN, NAN}
                              : getSampleByAge(histCount - 1);

  String json = "{";
  json += "\"ok\":" + String(haveBME ? "true" : "false");
  json += ",\"temperature_c\":" + String(isnan(s.tC)?0:s.tC, 2);
  json += ",\"humidity_pct\":" + String(isnan(s.hPct)?0:s.hPct, 1);
  json += ",\"pressure_hpa\":" + String(isnan(s.pHpa)?0:s.pHpa, 2);
  json += ",\"altitude_m\":" + String(isnan(s.altM)?0:s.altM, 1);
  json += "}";
  server.send(200, "application/json", json);
}

void handleApiHistory() {
  uint32_t nowms = millis();
  size_t n = histCount;
  if (n == 0) { server.send(200, "application/json", "{\"ok\":true,\"n\":0}"); return; }

  String json;
  json.reserve(n * 64 + 128);
  json += "{\"ok\":true,\"n\":" + String(n);

  // seconds ago array
  json += ",\"s\":[";
  for (size_t i = 0; i < n; ++i) {
    Sample s = getSampleByAge(i);
    uint32_t secAgo = (nowms - s.t_ms) / 1000;
    json += String(secAgo);
    if (i + 1 < n) json += ",";
  }
  json += "]";

  auto appendSeries = [&](const char* key, float Sample::*field, int digits) {
    json += ",\""; json += key; json += "\":[";
    for (size_t i = 0; i < n; ++i) {
      Sample s = getSampleByAge(i);
      json += String(s.*field, digits);
      if (i + 1 < n) json += ",";
    }
    json += "]";
  };

  appendSeries("tc",  &Sample::tC,   2);
  appendSeries("rh",  &Sample::hPct, 1);
  appendSeries("p",   &Sample::pHpa, 2);
  appendSeries("alt", &Sample::altM, 1);

  json += "}";
  server.send(200, "application/json", json);
}

void handleApiStatus() {
  bool up = WiFi.status() == WL_CONNECTED;
  long rssi = up ? WiFi.RSSI() : -127;   // dBm
  uint32_t uptimeS = millis() / 1000;

  String json = "{";
  json += "\"ok\":true";
  json += ",\"rssi_dbm\":" + String(rssi);
  json += ",\"uptime_s\":" + String(uptimeS);
  json += ",\"hostname\":\"" + String(MDNS_NAME) + "\"";
  json += ",\"ip\":\"" + (up ? WiFi.localIP().toString() : String("")) + "\"";
  json += "}";
  server.send(200, "application/json", json);
}

void setup() {
  Serial.begin(115200);
  while (!Serial) { delay(10); }
  Serial.println("\n[BOOT] ESP32-C6 BME680 Web Graphs + Status + mDNS");

  if (!SPIFFS.begin(true)) Serial.println("[SPIFFS] Mount failed");
  else Serial.println("[SPIFFS] Mounted");

  // WiFi + mDNS
  WiFi.mode(WIFI_STA);
  WiFi.setSleep(false);
  WiFi.setHostname(MDNS_NAME);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  Serial.printf("[WiFi] Connecting to %s", WIFI_SSID);
  unsigned long t0 = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - t0 < 20000) {
    Serial.print(".");
    delay(500);
  }
  Serial.println();
  if (WiFi.status() == WL_CONNECTED) {
    Serial.printf("[WiFi] Connected. IP: %s\n", WiFi.localIP().toString().c_str());
    if (MDNS.begin(MDNS_NAME)) {
      MDNS.addService("http", "tcp", 80);
      Serial.printf("[mDNS] http://%s.local/\n", MDNS_NAME);
    } else {
      Serial.println("[mDNS] start failed");
    }
  } else {
    Serial.println("[WiFi] Failed to connect (continuing)");
  }

  // Sensor
  haveBME = beginBME680();
  if (haveBME) setupBME680();

  // Prime buffer
  takeAndStoreSample();

  // Routes
  server.on("/",           HTTP_GET, handleRoot);
  server.on("/api/sensor", HTTP_GET, handleApiSensor);
  server.on("/api/history",HTTP_GET, handleApiHistory);
  server.on("/api/status", HTTP_GET, handleApiStatus);

  server.onNotFound([]() {
    String path = server.uri();
    if (path == "/") { handleRoot(); return; }
    if (!SPIFFS.exists(path)) { server.send(404, "text/plain", "Not found"); return; }
    String ct = "text/plain";
    if      (path.endsWith(".html")) ct = "text/html";
    else if (path.endsWith(".css"))  ct = "text/css";
    else if (path.endsWith(".js"))   ct = "application/javascript";
    File f = SPIFFS.open(path, "r"); server.streamFile(f, ct); f.close();
  });

  server.begin();
  Serial.println("[HTTP] Server started");
  if (WiFi.status() == WL_CONNECTED)
    Serial.println("[HTTP] Open: http://" + WiFi.localIP().toString() + "/  or  http://sparrow.local/");
}

void loop() {
  server.handleClient();

  // 1 Hz sampling
  static uint32_t lastSample = 0;
  uint32_t now = millis();
  if (now - lastSample >= 1000) {
    lastSample = now;
    takeAndStoreSample();
  }
  delay(2);
}