<?php
// temperature_handler.php - Kompletan kod sa bazom podataka

// ================= KONFIGURACIJA =================
define('API_KEY', 'esp32-secure-key-2024');
define('LOW_TEMP_THRESHOLD', 18.0);
define('HIGH_TEMP_THRESHOLD', 25.0);
define('HYSTERESIS', 1.0);
define('LOG_FILE', __DIR__ . '/temperature.log');

// Konfiguracija baze podataka
define('DB_HOST', 'localhost');
define('DB_NAME', 'temperature_db');
define('DB_USER', 'temperature_user');
define('DB_PASS', 'secure_password_123');
define('DB_CHARSET', 'utf8mb4');

// Dozvoljeni sensor IDs
$allowedSensors = ['esp32-bme280-01', 'esp32-bme280-02'];

// ================= INICIJALIZACIJA =================
header('Content-Type: application/json; charset=utf-8');
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, OPTIONS');
header('Access-Control-Allow-Headers: Content-Type, X-API-Key');

// Obradi OPTIONS zahtev za CORS
if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    http_response_code(200);
    exit;
}

// Funkcija za logovanje
function logEvent($level, $message) {
    $logEntry = sprintf(
        "[%s] [%s] %s\n",
        date('Y-m-d H:i:s'),
        $level,
        $message
    );
    
    @file_put_contents(LOG_FILE, $logEntry, FILE_APPEND | LOCK_EX);
}

// Funkcija za slanje JSON greške
function sendJsonError($message, $code = 500) {
    http_response_code($code);
    echo json_encode([
        'status' => 'error',
        'message' => $message,
        'timestamp' => date('Y-m-d H:i:s')
    ], JSON_UNESCAPED_UNICODE);
    exit;
}

// Provera HTTP metode
if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    sendJsonError('Samo POST zahtevi su dozvoljeni', 405);
}

// ================= AUTENTIFIKACIJA =================
$apiKey = $_SERVER['HTTP_X_API_KEY'] ?? '';
if (empty($apiKey)) {
    sendJsonError('API ključ je obavezan', 401);
}

if ($apiKey !== API_KEY) {
    sendJsonError('Nevažeći API ključ', 401);
}

// ================= KONEKCIJA SA BAZOM =================
try {
    $dsn = "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=" . DB_CHARSET;
    $pdo = new PDO($dsn, DB_USER, DB_PASS, [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES => false,
    ]);
    
    logEvent('INFO', 'Uspešna konekcija sa bazom podataka');
    
} catch (PDOException $e) {
    logEvent('ERROR', 'Greška pri konekciji sa bazom: ' . $e->getMessage());
    sendJsonError('Database connection failed', 500);
}

// ================= OBRADA ZAHTEVA =================
try {
    $json = file_get_contents('php://input');
    
    if (empty($json)) {
        sendJsonError('JSON podaci su prazni', 400);
    }
    
    $data = json_decode($json, true);
    
    if (json_last_error() !== JSON_ERROR_NONE) {
        sendJsonError('Nevažeći JSON format: ' . json_last_error_msg(), 400);
    }
    
    // Validacija obaveznih polja
    if (!isset($data['temperature']) || !isset($data['sensor_id'])) {
        sendJsonError('Nedostaje temperatura ili sensor_id', 400);
    }
    
    $sensorId = trim($data['sensor_id']);
    $temperature = floatval($data['temperature']);
    $humidity = isset($data['humidity']) ? floatval($data['humidity']) : null;
    $pressure = isset($data['pressure']) ? floatval($data['pressure']) : null;
    
    // Provera dozvoljenog senzora
    if (!in_array($sensorId, $allowedSensors)) {
        sendJsonError('Nedozvoljeni sensor ID: ' . $sensorId, 403);
    }
    
    // Validacija temperature
    if ($temperature < -50 || $temperature > 100) {
        sendJsonError('Temperatura van opsega (-50 do 100)', 400);
    }
    
    // ================= LOGIKA ZA GREJANJE =================
    $lastHeatingState = getLastHeatingState($pdo, $sensorId);
    $isCurrentlyHeating = ($lastHeatingState === 'on');
    
    // Određivanje komande sa histerezom
    $heatingCommand = determineHeatingCommand($temperature, $isCurrentlyHeating);
    
    // Snimanje podataka u bazu
    $insertSuccess = saveTemperatureData($pdo, $sensorId, $temperature, $humidity, $pressure, $heatingCommand);
    
    if (!$insertSuccess) {
        logEvent('ERROR', 'Greška pri snimanju u bazu za sensor: ' . $sensorId);
        sendJsonError('Database insert failed', 500);
    }
    
    // ================= GENERISANJE ODGOVORA =================
    $response = [
        'status' => 'success',
        'received_data' => [
            'temperature' => $temperature,
            'humidity' => $humidity,
            'pressure' => $pressure,
            'sensor_id' => $sensorId,
            'timestamp' => date('Y-m-d H:i:s')
        ],
        'heating_command' => $heatingCommand,
        'message' => getHeatingMessage($heatingCommand, $temperature),
        'database' => [
            'insert_id' => $pdo->lastInsertId(),
            'rows_affected' => $insertSuccess
        ],
        'threshold_info' => [
            'low_threshold' => LOW_TEMP_THRESHOLD,
            'high_threshold' => HIGH_TEMP_THRESHOLD,
            'hysteresis' => HYSTERESIS,
            'current_temperature' => $temperature
        ]
    ];
    
    http_response_code(200);
    echo json_encode($response, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
    
    logEvent('INFO', "Uspeh - Sensor $sensorId: Temp={$temperature}°C, Cmd=$heatingCommand, ID: " . $pdo->lastInsertId());
    
} catch (Exception $e) {
    logEvent('ERROR', 'Exception: ' . $e->getMessage());
    sendJsonError('Internal server error: ' . $e->getMessage(), 500);
}

// ================= POMOĆNE FUNKCIJE =================

function determineHeatingCommand($temperature, $isCurrentlyHeating) {
    if ($isCurrentlyHeating) {
        return ($temperature > (HIGH_TEMP_THRESHOLD + HYSTERESIS)) ? 'off' : 'on';
    } else {
        return ($temperature < (LOW_TEMP_THRESHOLD - HYSTERESIS)) ? 'on' : 'off';
    }
}

function getHeatingMessage($command, $temperature) {
    if ($command === 'on') {
        return "Grejanje UKLJUČENO. Temperatura ($temperature°C) je ispod donjeg praga.";
    } else {
        return "Grejanje ISKLJUČENO. Temperatura ($temperature°C) je iznad gornjeg praga.";
    }
}

function getLastHeatingState($pdo, $sensorId) {
    try {
        $stmt = $pdo->prepare("
            SELECT heating_command FROM temperature_logs 
            WHERE sensor_id = ? 
            ORDER BY created_at DESC 
            LIMIT 1
        ");
        
        $stmt->execute([$sensorId]);
        $result = $stmt->fetch();
        
        return $result ? $result['heating_command'] : 'off';
        
    } catch (PDOException $e) {
        logEvent('WARNING', 'getLastHeatingState error: ' . $e->getMessage());
        return 'off';
    }
}

function saveTemperatureData($pdo, $sensorId, $temperature, $humidity, $pressure, $command) {
    try {
        $stmt = $pdo->prepare("
            INSERT INTO temperature_logs 
            (sensor_id, temperature, humidity, pressure, heating_command) 
            VALUES (?, ?, ?, ?, ?)
        ");
        
        return $stmt->execute([$sensorId, $temperature, $humidity, $pressure, $command]);
        
    } catch (PDOException $e) {
        logEvent('ERROR', 'saveTemperatureData error: ' . $e->getMessage());
        return false;
    }
}

?>