<?php
/**
 * Get data from the solarprognose.de API.
 * This function waits until it is allowed to call the API and then returns the data.
 * @param string $url The url to call.
 * @param string $cacheFilePreferredNextApiRequestAtSecondOfHour The path and filename of the file to cache the preferredNextApiRequestAt.
 * @param boolean $quiet Do not print infos.
 * @param boolean $force Force the update, do not sleep
 * @return array The API result data.
 * @author Solarprognose.de
 * Usage Example:

// include
require_once('SolarpredictionApi.php');
// url
$url = 'https://www.solarprognose.de/web/de/solarprediction/api/v1/index?access-token=YOUR-API-KEY&algorithm=own-v1&type=hourly&_format=json';
// cache file to store preferredNextApiRequestAt
$filePreferredNextApiRequestAtSecondOfHour = './solarprognose_preferredNextApiRequestAt.txt';
try {
    // execute the api request
    $data = getSolarpredictionApi($url, $filePreferredNextApiRequestAtSecondOfHour, false, false);
    // this should print the api result data as a array:
    print_r($data);
} catch(\Exception $e) {
    echo $e;
}
 */
function getSolarpredictionApi($url, $cacheFilePreferredNextApiRequestAtSecondOfHour, $quiet = false, $force = false)
{
    $preferredNextApiRequestAtSecondOfHourCached = -1;

    // if file not exists, then continue without waiting (first call)
    if (file_exists($cacheFilePreferredNextApiRequestAtSecondOfHour)) {
        $preferredNextApiRequestAtSecondOfHourCached = intval(file_get_contents($cacheFilePreferredNextApiRequestAtSecondOfHour));

        // sleep until it is time to update
        $secondsNow = intval(idate('s')+idate('i')*60);
        $sleepTime = 0;
        if ($secondsNow > $preferredNextApiRequestAtSecondOfHourCached) {
            $sleepTime = 3600 - $secondsNow + $preferredNextApiRequestAtSecondOfHourCached;
        } else {
            $sleepTime = $preferredNextApiRequestAtSecondOfHourCached - $secondsNow;
        }
        if (!$quiet) {
            echo 'sleep until execution of next request in '.$sleepTime."s\n";
        }

        // a few seconds +/- is OK
        if ($force) {
            if (!$quiet) {
                echo 'force detected, do not sleep'."\n";
            }
        } else {
            sleep($sleepTime);
        }
    }

    // get api data
    $apiResult = [];
    if (is_callable('file_get_contents')) {
        $result = false;
        for ($i = 1; $i < 3; $i++) {
            $result = file_get_contents($url);
            if ($result !== false) {
                break;
            }
            sleep(rand(5, 15));
        }
    } elseif (function_exists('curl_version')) {
        $ch = curl_init($url);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
        curl_setopt($ch, CURLOPT_TIMEOUT, 100);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

        $resultinfo = null;
        for ($i = 1; $i < 3; $i++) {
            $result = curl_exec($ch);
            $resultinfo = curl_getinfo ($ch);

            if ($resultinfo['http_code'] == 200) {
                break;
            }
            sleep(rand(5, 15));
        }
    }

    $apiResult = json_decode($result, true);
    if (json_last_error() !== JSON_ERROR_NONE) {
        throw new \Exception(__FUNCTION__.': json is invalid');
    }

    if (isset($apiResult['preferredNextApiRequestAt']) && isset($apiResult['preferredNextApiRequestAt']['secondOfHour'])) {
        $preferredNextApiRequestAtSecondOfHour = $apiResult['preferredNextApiRequestAt']['secondOfHour'];
    }

    // cache if required: at first call and if the time has changed
    if ($preferredNextApiRequestAtSecondOfHour != $preferredNextApiRequestAtSecondOfHourCached) {
        if (!is_writable($cacheFilePreferredNextApiRequestAtSecondOfHour)) {
            file_put_contents($cacheFilePreferredNextApiRequestAtSecondOfHour, $preferredNextApiRequestAtSecondOfHour);
        } else {
            throw new \Exception(__FUNCTION__.': Cannot write to file: '.$cacheFilePreferredNextApiRequestAtSecondOfHour);
        }
    }
    
    return $apiResult;
} // function