.svg (or .png). A
* country is only asked if it is in tk_countries with its isoCode filled
* in AND there is a flag file for that code.
* - The flag is not linked by file name: the page shows flag.php, which sends
* the flag for the student's open question. A name like AUS.svg in the page
* would give the answer away.
* - Easy countries first: tk_countries.difficulty (1 = easy ... 10 = hard)
* decides the order. At level 0 a student gets the easiest 15% of the
* countries, and the pool grows to all of them as their accuracy grows
* (scaled up over their first 30 answers). Within the same difficulty the
* order is shuffled differently for each student.
* - Countries the student has been asked least this month come first.
* - Names are decoded from e107's HTML entities, and a code that has two rows
* (Bosnia and Herzegovina) is asked once.
*
* The expected answer is stored server-side (TkAnswerStore); the checker
* (answerChecker2::checkFlags) accepts alternative names such as "USA" or
* "Holland" through CountryNames.
*/
class flags {
const SUBJECT = 'flags';
private $user;
private $level = 0; // 0-100: how much of the country list to use
/**
* @param string $user User to supply the question for.
*/
public function __construct($user) {
$this->user = $user;
}
/**
* Make a question, show it, and remember it as the student's open question.
*/
public function getFlag() {
$problem = $this->getProblem();
if ($problem === null) {
e107::getRender()->tablerender('Flags', 'There are no flags to ask about yet. Please refresh the page.');
return;
}
$questionHtml = $this->htmlify($problem);
$db = e107::getDb();
$db->delete('tkLastQuestion', "user = '" . $db->escape($this->user) . "'");
$db->insert('tkLastQuestion', ['user' => $this->user, 'LastQuestionHtml' => base64_encode($questionHtml)]);
e107::getRender()->tablerender('Flags', $questionHtml);
}
/**
* Choose a flag without showing it.
*
* @return array|null ['answer1' => country name, 'question' => string, 'type' => 'flags',
* 'flag' => file name, 'iso' => code], or null when no flag can be asked.
*/
public function getProblem() {
$this->level = $this->difficulty();
$country = $this->pickCountry($this->flagFiles());
if ($country === null) {
return null;
}
return [
'answer1' => $country['country'],
'question' => 'Name this flag (' . $country['iso'] . ')',
'type' => self::SUBJECT,
'flag' => $country['file'],
'iso' => $country['iso'],
];
}
/**
* How much of the country list to use, 0-100: last month's accuracy, scaled
* up over the first 30 answers.
*
* @return float
*/
private function difficulty() {
$db = e107::getDb();
$stats = $db->retrieve(
"SELECT (SUM(correct)/COUNT(correct)*100) AS percent, COUNT(correct) AS count
FROM `" . MPREFIX . "tkReport`
WHERE answereddatestamp >= UNIX_TIMESTAMP(NOW() - INTERVAL 1 MONTH)
AND username = '" . $db->escape($this->user) . "' AND subject = '" . self::SUBJECT . "'"
);
if (!is_array($stats) || (int) $stats['count'] === 0) {
return 0.0;
}
$sample = min(1.0, ((int) $stats['count']) / 30);
return max(0.0, min(100.0, (float) $stats['percent'])) * $sample;
}
/**
* The flag files that exist: ['AUS' => 'AUS.svg', ...]
*/
private function flagFiles() {
$dir = dirname(__DIR__, 2) . '/resources/flags';
$files = [];
foreach (['svg', 'png'] as $extension) {
$found = glob($dir . '/*.' . $extension);
foreach (($found ? $found : []) as $path) {
$code = strtoupper(pathinfo($path, PATHINFO_FILENAME));
if (preg_match('/^[A-Z]{3}$/', $code) && !isset($files[$code])) {
$files[$code] = basename($path);
}
}
}
return $files;
}
/**
* @param array $files ['AUS' => 'AUS.svg', ...]
* @return array|null ['country', 'iso', 'file', 'difficulty']
*/
private function pickCountry(array $files) {
$db = e107::getDb();
$seen = [];
// Countries that have both an ISO code and a flag file, one row per code
// (the first by id: the table has two rows, Bosnia and Herzegovina, for BIH).
$countries = [];
$db->gen("SELECT `country`, `isoCode`, `difficulty` FROM `" . MPREFIX . "tk_countries` WHERE `isoCode` != '' ORDER BY `id`");
while ($row = $db->fetch()) {
$code = strtoupper(trim($row['isoCode']));
// e107 stores an apostrophe as ' ("Cote d'Ivoire"): show and compare the real name.
$name = trim(html_entity_decode($row['country'], ENT_QUOTES | ENT_HTML5, 'UTF-8'));
if ($name !== '' && isset($files[$code]) && !isset($seen[$code])) {
$seen[$code] = true;
$countries[] = [
'country' => $name,
'iso' => $code,
'file' => $files[$code],
'difficulty' => (int) $row['difficulty'],
'order' => crc32($this->user . '|' . $code),
];
}
}
if (count($countries) < 4) {
return null;
}
// How often each has been asked this month.
$asked = [];
$db->gen("SELECT `answer`, COUNT(*) AS cnt FROM `" . MPREFIX . "tkReport`
WHERE `username` = '" . $db->escape($this->user) . "' AND `subject` = '" . self::SUBJECT . "'
AND `answereddatestamp` >= UNIX_TIMESTAMP(NOW() - INTERVAL 1 MONTH) GROUP BY `answer`");
while ($row = $db->fetch()) {
$asked[$row['answer']] = (int) $row['cnt'];
}
// Easiest first; the same difficulty in an order of this student's own.
usort($countries, function ($a, $b) {
if ($a['difficulty'] !== $b['difficulty']) {
return $a['difficulty'] <=> $b['difficulty'];
}
return $a['order'] <=> $b['order'];
});
$total = count($countries);
$size = (int) ceil($total * (0.15 + 0.85 * $this->level / 100));
$size = max(min($total, 8), min($total, $size));
$pool = array_slice($countries, 0, $size);
// The least-asked countries in the pool, one at random.
$fewest = null;
foreach ($pool as $country) {
$count = isset($asked[$country['country']]) ? $asked[$country['country']] : 0;
if ($fewest === null || $count < $fewest) {
$fewest = $count;
}
}
$candidates = [];
foreach ($pool as $country) {
$count = isset($asked[$country['country']]) ? $asked[$country['country']] : 0;
if ($count === $fewest) {
$candidates[] = $country;
}
}
return $candidates[array_rand($candidates)];
}
private function htmlify($problem) {
// Expected answer stays on the server; the form only carries a token.
$token = TkAnswerStore::issue($this->user, $problem);
$frm = e107::getForm();
$fString = $frm->open('questionForm', 'post', '', ['autocomplete' => 'off', 'class' => 'formclass']);
$fString .= $frm->label('Flags
') . "\n";
$fString .= $frm->label('Which country has this flag? Type its name.') . "\n";
$fString .= '';
// flag.php sends the flag for this student's open question (no file name, so no clue in the page).
$fString .= ') . ')
';
$fString .= $frm->text('a1', '', 60, ['placeholder' => 'Write the country here!', 'autocomplete' => "off", 'spellcheck' => "false"]) . "\n";
$fString .= $frm->hidden('checkerData', $token, ['id' => 'checkerData']);
$fString .= $frm->hidden('subject', self::SUBJECT, ['id' => 'subject']);
$fString .= '' . "\n";
$fString .= $frm->button('Answer', 'Check answer') . "\n";
$fString .= $frm->close();
$fString .= '';
return $fString;
}
}