Viewing file:  IndirectExchange.php (4.16 KB) -rw-r--r--
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<?php
declare(strict_types=1);
namespace Money\Exchange;
use Money\Currencies;
use Money\Currency;
use Money\CurrencyPair;
use Money\Exception\UnresolvableCurrencyPairException;
use Money\Exchange;
use Money\Money;
use SplQueue;
use function array_reduce;
use function array_reverse;
/**
* Provides a way to get an exchange rate through a minimal set of intermediate conversions.
*/
final class IndirectExchange implements Exchange
{
private Currencies $currencies;
private Exchange $exchange;
public function __construct(Exchange $exchange, Currencies $currencies)
{
$this->exchange = $exchange;
$this->currencies = $currencies;
}
public function quote(Currency $baseCurrency, Currency $counterCurrency): CurrencyPair
{
try {
return $this->exchange->quote($baseCurrency, $counterCurrency);
} catch (UnresolvableCurrencyPairException) {
$rate = array_reduce(
$this->getConversions($baseCurrency, $counterCurrency),
/**
* @psalm-param numeric-string $carry
*
* @psalm-return numeric-string
*/
static function (string $carry, CurrencyPair $pair) {
$calculator = Money::getCalculator();
return $calculator::multiply($carry, $pair->getConversionRatio());
},
'1.0'
);
return new CurrencyPair($baseCurrency, $counterCurrency, $rate);
}
}
/**
* @return CurrencyPair[]
*
* @throws UnresolvableCurrencyPairException
*/
private function getConversions(Currency $baseCurrency, Currency $counterCurrency): array
{
$startNode = new IndirectExchangeQueuedItem($baseCurrency);
$startNode->discovered = true;
/** @psalm-var array<non-empty-string, IndirectExchangeQueuedItem> $nodes */
$nodes = [$baseCurrency->getCode() => $startNode];
/** @psam-var SplQueue<IndirectExchangeQueuedItem> $frontier */
$frontier = new SplQueue();
$frontier->enqueue($startNode);
while ($frontier->count()) {
/** @psalm-var IndirectExchangeQueuedItem $currentNode */
$currentNode = $frontier->dequeue();
$currentCurrency = $currentNode->currency;
if ($currentCurrency->equals($counterCurrency)) {
return $this->reconstructConversionChain($nodes, $currentNode);
}
foreach ($this->currencies as $candidateCurrency) {
if (! isset($nodes[$candidateCurrency->getCode()])) {
$nodes[$candidateCurrency->getCode()] = new IndirectExchangeQueuedItem($candidateCurrency);
}
$node = $nodes[$candidateCurrency->getCode()];
if ($node->discovered) {
continue;
}
try {
// Check if the candidate is a neighbor. This will throw an exception if it isn't.
$this->exchange->quote($currentCurrency, $candidateCurrency);
$node->discovered = true;
$node->parent = $currentNode;
$frontier->enqueue($node);
} catch (UnresolvableCurrencyPairException $exception) {
// Not a neighbor. Move on.
}
}
}
throw UnresolvableCurrencyPairException::createFromCurrencies($baseCurrency, $counterCurrency);
}
/**
* @psalm-param array<non-empty-string, IndirectExchangeQueuedItem> $currencies
*
* @return CurrencyPair[]
* @psalm-return list<CurrencyPair>
*/
private function reconstructConversionChain(array $currencies, IndirectExchangeQueuedItem $goalNode): array
{
$current = $goalNode;
$conversions = [];
while ($current->parent) {
$previous = $currencies[$current->parent->currency->getCode()];
$conversions[] = $this->exchange->quote($previous->currency, $current->currency);
$current = $previous;
}
return array_reverse($conversions);
}
}
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