<?php
require_once __DIR__ . '/../connect.php';

$lat = filterRequest("lat");
$lng = filterRequest("lng");

if (!$lat || !$lng) {
    jsonError("Missing coordinates");
    exit();
}

if (!isset($redis) || $redis === null) {
    // If Redis is not available, we fail gracefully.
    jsonSuccess(null, "Demand logged (fallback)");
    exit();
}

// Create a 1.5 km grid cell
// 1 degree latitude is approximately 111 km. 
// 1.5 km / 111 km ≈ 0.0135 degrees.
$grid_size = 0.0135;

$grid_lat = round((float)$lat / $grid_size) * $grid_size;
$grid_lng = round((float)$lng / $grid_size) * $grid_size;

$grid_id = $grid_lat . "_" . $grid_lng;
$redisKey = "demand:grid:" . $grid_id;

try {
    // Increment the demand count for this grid
    $currentCount = $redis->incr($redisKey);
    
    // If this is the first request, set the expiry to 60 seconds
    if ($currentCount == 1) {
        $redis->expire($redisKey, 60);
    }
    
    jsonSuccess(["grid_id" => $grid_id, "count" => $currentCount], "Demand logged successfully");
} catch (Exception $e) {
    error_log("[log_demand.php] Redis error: " . $e->getMessage());
    jsonError("Error logging demand");
}
?>