<?php
$config = parse_ini_file(__DIR__ . '/../config/flashii.ini');

try {
    $pdo = new PDO($config['exrate-dsn'], $config['exrate-user'], $config['exrate-pass'], [
        PDO::ATTR_CASE => PDO::CASE_NATURAL,
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_ORACLE_NULLS => PDO::NULL_NATURAL,
        PDO::ATTR_STRINGIFY_FETCHES => false,
        PDO::ATTR_EMULATE_PREPARES => false,
        PDO::MYSQL_ATTR_INIT_COMMAND => "
            SET SESSION
                sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION',
                time_zone = '+00:00';
        ",
    ]);
} catch(PDOException $ex) {
    die((string)$ex);
}

define('EXRATE_INTER', 'EUR');
define('EXRATE_COMMON', [
    'EUR', 'AUD', 'GBP', 'CAD', 'USD', 'JPY', 'PLN', 'SGD', 'RUB', 'ILS',
]);

$from   = strtoupper((string)filter_input(INPUT_GET, 'from', FILTER_SANITIZE_STRING));
$to     = strtoupper((string)filter_input(INPUT_GET, 'to',   FILTER_SANITIZE_STRING));
$amount = (string)(filter_input(INPUT_GET, 'amount', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION) ?? '1');

if((!empty($to) && strlen($to) !== 3) || strlen($from) !== 3) {
    http_response_code(400);
    die('Invalid currency specified.');
}

$needsRefresh = $pdo->prepare('SELECT MAX(`rate_stored`) <= NOW() - INTERVAL 1 DAY FROM `exchange-rates` LIMIT 1');
$needsRefresh = $needsRefresh->execute() ? $needsRefresh->fetchColumn() : 1;
if($needsRefresh !== 0) {
    $data = json_decode(file_get_contents('https://api.exchangerate.host/latest?base=' . EXRATE_INTER), true);
    if($data !== null) {
        $pdo->exec('TRUNCATE `exchange-rates`;');
        $insertCurrency = $pdo->prepare('REPLACE INTO `exchange-rates` (`rate_from`, `rate_to`, `rate_value`) VALUES (:from, :to, :value)');
        $insertCurrency->bindValue('from', $data['base']);
        foreach($data['rates'] as $currency => $rate) {
            $insertCurrency->bindValue('to', $currency);
            $insertCurrency->bindValue('value', $rate);
            $insertCurrency->execute();
        }
    }
}

$result = new stdClass;
$result->from = $from;
$result->to = $to;
$result->amount = (float)$amount;

if($from === $to) {
    $result->result = $result->amount;
} else {
    $convertCurrency = $pdo->prepare('SELECT (SELECT (:amount / `rate_value`) FROM `exchange-rates` WHERE `rate_from` = \'' . EXRATE_INTER . '\' AND `rate_to` = :from) * `rate_value` FROM `exchange-rates` WHERE `rate_from` = \'' . EXRATE_INTER . '\' AND `rate_to` = :to;');
    $convertCurrency->bindValue('from', $from);
    $convertCurrency->bindValue('amount', $amount);

    if(empty($to)) {
        $result->results = [];
        foreach(EXRATE_COMMON as $commonCurrency) {
            if($commonCurrency === $from)
                continue;
            $result->results[] = $current = new stdClass;
            $current->to = $commonCurrency;
            $convertCurrency->bindValue('to', $commonCurrency);
            $convertCurrency->execute();
            $current->result = $convertCurrency->fetchColumn() ?? 0;
        }
    } else {
        $convertCurrency->bindValue('to', $to);
        $convertCurrency->execute();
        $result->result = $convertCurrency->fetchColumn() ?? 0;
    }
}

http_response_code(200);
header('Content-Type: application/json');
echo json_encode($result);