<?php
// Enable error reporting for debugging
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

require_once __DIR__ . '/../config.php';

$bulkFileName = 'weather_14.json.gz';
$bulkUrl = "https://bulk.openweathermap.org/snapshot/{$bulkFileName}?appid=" . OWM_API_KEY;

// Use a stream context to capture HTTP status headers
$context = stream_context_create(['http' => ['ignore_errors' => true]]);
$gzData = @file_get_contents($bulkUrl, false, $context);

// Check for errors and specific HTTP status codes
if ($gzData === false || !isset($http_response_header[0]) || strpos($http_response_header[0], '200 OK') === false) {
    $error_message = 'Failed to download bulk weather data.';
    if (isset($http_response_header[0])) {
        if (strpos($http_response_header[0], '401 Unauthorized') !== false) {
            $error_message = 'OpenWeatherMap API key is invalid for the Bulk Data service. The key may be correct for other services like weather tiles, but lacks permission for bulk downloads.';
            http_response_code(401);
        } else {
            $error_message .= ' Server responded with: ' . $http_response_header[0];
            http_response_code(500);
        }
    } else {
        http_response_code(500);
    }
    echo json_encode(['error' => $error_message]);
    exit;
}

$jsonData = gzdecode($gzData);
if ($jsonData === false) {
    http_response_code(500);
    echo json_encode(['error' => 'Failed to decompress weather data.']);
    exit;
}

// The file contains JSON objects separated by newlines
$lines = explode("\n", trim($jsonData));
$cities = [];
foreach ($lines as $line) {
    if (!empty($line)) {
        $cities[] = json_decode($line, true);
    }
}

if (empty($cities)) {
    http_response_code(500);
    echo json_encode(['error' => 'Failed to parse weather data JSON or file is empty.']);
    exit;
}

// --- Interpolation ---

$nx = 72; // Grid points in longitude (every 5 degrees)
$ny = 37; // Grid points in latitude (every 5 degrees)
$lo1 = -180;
$la1 = 90;
$dx = 5;
$dy = 5;

$uData = [];
$vData = [];

for ($j = 0; $j < $ny; $j++) {
    $lat = $la1 - $j * $dy;
    for ($i = 0; $i < $nx; $i++) {
        $lon = $lo1 + $i * $dx;
        $wind = interpolatePoint($lat, $lon, $cities);
        $uData[] = $wind['u'];
        $vData[] = $wind['v'];
    }
}

// --- Format Data ---

$refTime = gmdate("Y-m-d\\TH:i:s.v\\Z");

$formattedData = [
    [
        "header" => [
            "nx" => $nx,
            "ny" => $ny,
            "lo1" => $lo1,
            "la1" => $la1,
            "dx" => $dx,
            "dy" => $dy,
            "parameterCategory" => 2,
            "parameterNumber" => 2,
            "forecastTime" => 0,
            "refTime" => $refTime,
        ],
        "data" => $uData
    ],
    [
        "header" => [
            "nx" => $nx,
            "ny" => $ny,
            "lo1" => $lo1,
            "la1" => $la1,
            "dx" => $dx,
            "dy" => $dy,
            "parameterCategory" => 2,
            "parameterNumber" => 3,
            "forecastTime" => 0,
            "refTime" => $refTime,
        ],
        "data" => $vData
    ]
];

// --- Caching and Output ---
$cacheDir = dirname($cacheFile);
if (!is_dir($cacheDir)) {
    mkdir($cacheDir, 0755, true);
}
file_put_contents($cacheFile, json_encode($formattedData));

echo json_encode($formattedData);

?>