<?php
include 'config.php';
include 'database.php';

// Postavi CORS zaglavlja
header('Access-Control-Allow-Origin: ' . implode(', ', ALLOWED_ORIGINS));
header('Access-Control-Allow-Methods: POST, OPTIONS');
header('Access-Control-Allow-Headers: Content-Type, X-API-Key');
header('Content-Type: application/json; charset=utf-8');

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

// Provera HTTP metode
if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
    exit;
}

// Autentifikacija preko API ključa
$apiKey = $_SERVER['HTTP_X_API_KEY'] ?? '';
if ($apiKey !== API_KEY) {
    http_response_code(401);
    echo json_encode(['error' => 'Invalid API key']);
    logEvent('WARNING', 'Invalid API key attempt: ' . $apiKey);
    exit;
}

// Provera Content-Type
$contentType = $_SERVER['CONTENT_TYPE'] ?? '';
if (stripos($contentType, 'application/json') === false) {
    http_response_code(415);
    echo json_encode(['error' => 'Unsupported Media Type. Use application/json']);
    exit;
}

// Čitanje i parsiranje JSON podataka
$json = file_get_contents('php://input');
$data = json_decode($json, true);

if (json_last_error() !== JSON_ERROR_NONE) {
    http_response_code(400);
    echo json_encode(['error' => 'Invalid JSON: ' . json_last_error_msg()]);
    exit;
}

// Validacija obaveznih polja
$requiredFields = ['temperature', 'sensor_id'];
foreach ($requiredFields as $field) {
    if (!isset($data[$field])) {
        http_response_code(400);
        echo json_encode(['error' => "Missing required field: $field"]);
        exit;
    }
}

$sensorId = $data['sensor_id'];
$temperature = floatval($data['temperature']);
$humidity = isset($data['humidity']) ? floatval($data['humidity']) : null;
$pressure = isset($data['pressure']) ? floatval($data['pressure']) : null;

// Provera da li je sensor dozvoljen
if (!in_array($sensorId, $allowedSensors)) {
    http_response_code(403);
    echo json_encode(['error' => 'Unauthorized sensor ID']);
    logEvent('WARNING', "Unauthorized sensor attempt: $sensorId");
    exit;
}

// Validacija temperature
if ($temperature < -50 || $temperature > 100) {
    http_response_code(400);
    echo json_encode(['error' => 'Temperature out of valid range (-50 to 100)']);
    exit;
}

// Inicijalizacija baze
$db = new TemperatureDB();

// Dobijanje poslednjeg stanja grejanja za histerezu
$lastHeatingState = $db->getLastHeatingState($sensorId);
$lastHeatingOn = ($lastHeatingState === 'on');

// Logika za kontrolu grejanja sa histerezom
$heatingCommand = determineHeatingCommand($temperature, $lastHeatingOn);

// Snimanje u bazu
if ($db->logTemperature($sensorId, $temperature, $humidity, $pressure, $heatingCommand)) {
    logEvent('INFO', "Sensor $sensorId: Temp=$temperature°C, Heating=$heatingCommand");
} else {
    logEvent('ERROR', "Failed to log data for sensor $sensorId");
}

// Dodatne statistike
$stats = $db->getTemperatureStats($sensorId, 24);

// Generisanje odgovora
$response = [
    'status' => 'success',
    'data' => [
        'received_temperature' => $temperature,
        'received_humidity' => $humidity,
        'received_pressure' => $pressure,
        'sensor_id' => $sensorId
    ],
    'command' => [
        'heating' => $heatingCommand,
        'message' => getHeatingMessage($heatingCommand, $temperature)
    ],
    'thresholds' => [
        'low_temp' => LOW_TEMP_THRESHOLD,
        'high_temp' => HIGH_TEMP_THRESHOLD,
        'hysteresis' => HYSTERESIS
    ],
    'statistics' => $stats,
    'timestamp' => date('Y-m-d H:i:s'),
    'server_id' => gethostname()
];

http_response_code(200);
echo json_encode($response, JSON_PRETTY_PRINT);

// Funkcija za određivanje komande grejanja sa histerezom
function determineHeatingCommand($temperature, $isCurrentlyHeating) {
    if ($isCurrentlyHeating) {
        // Ako grejanje radi, gasi ga tek kada temperatura predje HIGH + histereza
        if ($temperature > (HIGH_TEMP_THRESHOLD + HYSTERESIS)) {
            return 'off';
        }
        return 'on';
    } else {
        // Ako grejanje ne radi, uključi ga kada temperatura padne ispod LOW - histereza
        if ($temperature < (LOW_TEMP_THRESHOLD - HYSTERESIS)) {
            return 'on';
        }
        return 'off';
    }
}

// Funkcija za generisanje poruke
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.";
    }
}

// Funkcija za logovanje
function logEvent($level, $message) {
    $logEntry = sprintf(
        "[%s] %s: %s\n",
        date('Y-m-d H:i:s'),
        $level,
        $message
    );
    
    // Rotacija logova
    if (file_exists(LOG_FILE) && filesize(LOG_FILE) > MAX_LOG_SIZE) {
        $backupFile = LOG_FILE . '.' . date('Y-m-d_His');
        rename(LOG_FILE, $backupFile);
    }
    
    file_put_contents(LOG_FILE, $logEntry, FILE_APPEND | LOCK_EX);
}
?>