#include <RCSwitch.h>

RCSwitch rx = RCSwitch();

// باید با فرستنده یکسان باشد
const String PRIVATE_KEY = "as23f";

// دستگاه‌های مجاز
const String ALLOWED_DEVICES[] = {"dr142", "abcde", "fghij"};
const int NUM_ALLOWED_DEVICES = 3;

// بافرهای دریافت
String receivedKey = "";
String receivedHex = "";

// کنترل فریم
bool receivingPublicKey = true;
int  receivedChars = 0;
unsigned long lastReceiveTime = 0;
const unsigned long TIMEOUT_MS = 500;

// طول متن اصلی انتظار می‌رود 25 باشد
const int EXPECTED_PLAIN_LEN = 25;

// XOR ساده
String decryptData(const String &data, const String &key) {
  String out;
  out.reserve(data.length());
  for (int i = 0; i < data.length(); i++) {
    out += (char)(data[i] ^ key[i % key.length()]);
  }
  return out;
}

bool isDeviceAllowed(const String &deviceId) {
  for (int i = 0; i < NUM_ALLOWED_DEVICES; i++) {
    if (deviceId == ALLOWED_DEVICES[i]) return true;
  }
  return false;
}

static inline bool isHexChar(char c) {
  return (c >= '0' && c <= '9') ||
         (c >= 'A' && c <= 'F') ||
         (c >= 'a' && c <= 'f');
}

void resetFrame() {
  receivedKey = "";
  receivedHex = "";
  receivingPublicKey = true;
  receivedChars = 0;
}

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

  rx.enableReceive(0);   // interrupt 0 → پایه 2 در آردوینو UNO
  rx.setProtocol(1);
  rx.setPulseLength(300);

  resetFrame();

  Serial.println(F("=== Receiver Started ==="));
  Serial.print(F("Private Key: ")); Serial.println(PRIVATE_KEY);
  Serial.print(F("Allowed IDs: "));
  for (int i = 0; i < NUM_ALLOWED_DEVICES; i++) { Serial.print(ALLOWED_DEVICES[i]); Serial.print(' '); }
  Serial.println();
}

void loop() {
  if (rx.available()) {
    unsigned long value = rx.getReceivedValue();
    unsigned int bitlen = rx.getReceivedBitlength();

    if (bitlen == 8) {
      char c = (char)value;

      if (receivingPublicKey) {
        if (receivedKey.length() < 5) {
          receivedKey += c;
          //Serial.print(F("Received key char: ")); Serial.println(c);
          receivedChars++;
          if (receivedKey.length() == 5) {
            receivingPublicKey = false;
            Serial.println(F("Now receiving encrypted HEX data..."));
          }
        }
      } else {
        // فقط کاراکتر HEX معتبر ذخیره شود
        if (isHexChar(c)) {
          receivedHex += c;
          //Serial.print(F("Received HEX char: ")); Serial.println(c);
          receivedChars++;
        } else {
          // نویز را رد کن
          Serial.print(F("Ignored non-HEX char: 0x"));
          Serial.println((int)(uint8_t)c, HEX);
        }
      }

      lastReceiveTime = millis();
    }

    rx.resetAvailable();
  }

  // اگر وقفه افتاد، پردازش کن
  if (receivedChars >= 5 && (millis() - lastReceiveTime) > TIMEOUT_MS) {
    Serial.println(F("=== Processing Data ==="));
    Serial.print(F("Received Public Key: ")); Serial.println(receivedKey);

    if (receivedKey != PRIVATE_KEY) {
      Serial.println(F("Key verification: FAILED"));
      resetFrame();
      return;
    }
    Serial.println(F("Key verification: SUCCESS"));

    // طول HEX باید زوج باشد (هر دو کاراکتر → یک بایت)
    if ((receivedHex.length() % 2) != 0) {
      Serial.print(F("Odd HEX length: ")); Serial.println(receivedHex.length());
      resetFrame();
      return;
    }

    // تبدیل HEX → بایت‌ها
    String decoded; decoded.reserve(receivedHex.length() / 2);
    for (int i = 0; i + 1 < receivedHex.length(); i += 2) {
      char hex2[3] = { receivedHex[i], receivedHex[i+1], '\0' };
      char b = (char) strtol(hex2, NULL, 16);
      decoded += b;
    }

    Serial.print(F("Decoded length: ")); Serial.println(decoded.length());
    Serial.print(F("Decoded (raw XORed) bytes: "));
    for (int i = 0; i < decoded.length(); i++) {
      Serial.print((int)(uint8_t)decoded[i]); Serial.print(' ');
    }
    Serial.println();

    // باید دقیقاً به طول 25 بایت باشد
    if (decoded.length() != EXPECTED_PLAIN_LEN) {
      Serial.println(F("Unexpected decoded length (should be 25)."));
      resetFrame();
      return;
    }

    // رمزگشایی
    String plain = decryptData(decoded, PRIVATE_KEY);
    Serial.print(F("Decrypted Data: ")); Serial.println(plain);

    // اعتبارسنجی قالب
    if (plain.length() != EXPECTED_PLAIN_LEN ||
        plain[5]  != 'S' || plain[10] != 'G' ||
        plain[15] != 'T' || plain[20] != 'H') {
      Serial.println(F("Format check failed."));
      resetFrame();
      return;
    }

    String deviceId = plain.substring(0, 5);
    Serial.print(F("Device ID: ")); Serial.println(deviceId);

    if (!isDeviceAllowed(deviceId)) {
      Serial.println(F("Device authorization: FAILED"));
      resetFrame();
      return;
    }

    Serial.println(F("Device authorization: SUCCESS"));

    // پارس مقادیر
    String sSoil = plain.substring(6, 10);   // بین S و G
    String sGas  = plain.substring(11, 15);  // بین G و T
    String sTemp = plain.substring(16, 20);  // بین T و H
    String sHum  = plain.substring(21, 25);  // بعد از H

    int   soilMoisture = sSoil.toInt();
    int   gasValue     = sGas.toInt();
    float temperature  = sTemp.toInt() / 10.0;
    float humidity     = sHum.toInt()  / 10.0;

    Serial.println(F("=== Authorized Data ==="));
    Serial.print(F("Soil Moisture: ")); Serial.print(soilMoisture);
    Serial.print(F("  -  Gas Value    : ")); Serial.print(gasValue);
    Serial.print(F("  -  Temperature  : ")); Serial.print(temperature); Serial.print(F(" C"));
    Serial.print(F("  -  Humidity     : ")); Serial.print(humidity);    Serial.println(F(" %"));
    Serial.println(F("======================="));

    // آماده دریافت بعدی
    resetFrame();
  }

  delay(5);
}