<?php
// ============================================================
// osrm_routing.php
// Helper functions for OpenStreetMap Routing Machine (OSRM)
// Used to estimate accurate distance (km) and duration (mins)
// ============================================================

/**
 * Get Distance and Duration between two coordinates using public OSRM server.
 * Note: If you host your own OSRM, replace the $osrmBaseUrl.
 * 
 * @param float $startLat
 * @param float $startLng
 * @param float $endLat
 * @param float $endLng
 * @return array|null Returns ['distance_km' => float, 'duration_min' => float] or null on failure.
 */
function getOsrmRouteDetails($startLat, $startLng, $endLat, $endLng) {
    // Format: longitude,latitude
    $coordinates = "{$startLng},{$startLat};{$endLng},{$endLat}";
    
    // Using public demo server. Note: Has rate limits.
    // For production, highly recommended to use: "http://your-own-osrm-server.com:5000"
    $osrmBaseUrl = "http://router.project-osrm.org";
    $url = "{$osrmBaseUrl}/route/v1/driving/{$coordinates}?overview=false";

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_TIMEOUT, 5); // 5 seconds timeout
    
    // Add a User-Agent to avoid being blocked by the public demo server
    curl_setopt($ch, CURLOPT_USERAGENT, "SiroRideHailingApp/1.0");

    $response = curl_exec($ch);
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    if ($httpCode === 200 && $response) {
        $data = json_decode($response, true);
        if (isset($data['code']) && $data['code'] === 'Ok' && isset($data['routes'][0])) {
            $route = $data['routes'][0];
            $distanceMeters = isset($route['distance']) ? (float)$route['distance'] : 0;
            $durationSeconds = isset($route['duration']) ? (float)$route['duration'] : 0;
            
            return [
                'distance_km' => round($distanceMeters / 1000, 2),
                'duration_min' => round($durationSeconds / 60, 2)
            ];
        }
    }
    
    return null;
}