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<?php |
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|
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namespace Money\Exchange; |
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|
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use Money\Calculator; |
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use Money\Calculator\BcMathCalculator; |
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use Money\Calculator\GmpCalculator; |
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use Money\Calculator\PhpCalculator; |
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use Money\Currencies; |
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use Money\Currency; |
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use Money\CurrencyPair; |
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use Money\Exception\UnresolvableCurrencyPairException; |
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use Money\Exchange; |
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|
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/** |
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* Provides a way to get an exchange rate through a minimal set of intermediate conversions. |
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* |
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* @author Michael Cordingley <[email protected]> |
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*/ |
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final class IndirectExchange implements Exchange |
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{ |
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/** |
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* @var Calculator |
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*/ |
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private static $calculator; |
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|
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/** |
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* @var array |
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*/ |
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private static $calculators = [ |
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BcMathCalculator::class, |
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GmpCalculator::class, |
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PhpCalculator::class, |
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]; |
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|
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/** |
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* @var Currencies |
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*/ |
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private $currencies; |
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|
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/** |
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* @var Exchange |
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*/ |
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private $exchange; |
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|
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public function __construct(Exchange $exchange, Currencies $currencies) |
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{ |
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$this->exchange = $exchange; |
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$this->currencies = $currencies; |
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} |
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|
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/** |
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* @param string $calculator |
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*/ |
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public static function registerCalculator($calculator) |
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{ |
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if (is_a($calculator, Calculator::class, true) === false) { |
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throw new \InvalidArgumentException('Calculator must implement '.Calculator::class); |
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} |
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|
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array_unshift(self::$calculators, $calculator); |
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} |
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|
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/** |
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* {@inheritdoc} |
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*/ |
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public function quote(Currency $baseCurrency, Currency $counterCurrency) |
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{ |
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try { |
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return $this->exchange->quote($baseCurrency, $counterCurrency); |
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} catch (UnresolvableCurrencyPairException $exception) { |
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$rate = array_reduce($this->getConversions($baseCurrency, $counterCurrency), function ($carry, CurrencyPair $pair) { |
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return static::getCalculator()->multiply($carry, $pair->getConversionRatio()); |
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}, '1.0'); |
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|
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return new CurrencyPair($baseCurrency, $counterCurrency, $rate); |
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} |
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} |
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|
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/** |
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* @return CurrencyPair[] |
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* |
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* @throws UnresolvableCurrencyPairException |
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*/ |
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private function getConversions(Currency $baseCurrency, Currency $counterCurrency) |
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{ |
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$startNode = $this->initializeNode($baseCurrency); |
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$startNode->discovered = true; |
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|
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$nodes = [$baseCurrency->getCode() => $startNode]; |
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|
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$frontier = new \SplQueue(); |
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$frontier->enqueue($startNode); |
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|
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while ($frontier->count()) { |
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/** @var \stdClass $currentNode */ |
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$currentNode = $frontier->dequeue(); |
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|
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/** @var Currency $currentCurrency */ |
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$currentCurrency = $currentNode->currency; |
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|
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if ($currentCurrency->equals($counterCurrency)) { |
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return $this->reconstructConversionChain($nodes, $currentNode); |
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} |
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|
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/** @var Currency $candidateCurrency */ |
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foreach ($this->currencies as $candidateCurrency) { |
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if (!isset($nodes[$candidateCurrency->getCode()])) { |
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$nodes[$candidateCurrency->getCode()] = $this->initializeNode($candidateCurrency); |
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} |
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|
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/** @var \stdClass $node */ |
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$node = $nodes[$candidateCurrency->getCode()]; |
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|
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if (!$node->discovered) { |
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try { |
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// Check if the candidate is a neighbor. This will throw an exception if it isn't. |
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$this->exchange->quote($currentCurrency, $candidateCurrency); |
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|
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$node->discovered = true; |
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$node->parent = $currentNode; |
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|
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$frontier->enqueue($node); |
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} catch (UnresolvableCurrencyPairException $exception) { |
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// Not a neighbor. Move on. |
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} |
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} |
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} |
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} |
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|
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throw UnresolvableCurrencyPairException::createFromCurrencies($baseCurrency, $counterCurrency); |
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} |
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|
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/** |
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* @return \stdClass |
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*/ |
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private function initializeNode(Currency $currency) |
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{ |
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$node = new \stdClass(); |
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|
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$node->currency = $currency; |
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$node->discovered = false; |
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$node->parent = null; |
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|
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return $node; |
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} |
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|
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/** |
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* @return CurrencyPair[] |
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*/ |
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private function reconstructConversionChain(array $currencies, \stdClass $goalNode) |
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{ |
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$current = $goalNode; |
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$conversions = []; |
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|
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while ($current->parent) { |
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$previous = $currencies[$current->parent->currency->getCode()]; |
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$conversions[] = $this->exchange->quote($previous->currency, $current->currency); |
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$current = $previous; |
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} |
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|
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return array_reverse($conversions); |
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} |
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|
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/** |
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* @return Calculator |
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*/ |
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private function getCalculator() |
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{ |
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if (null === self::$calculator) { |
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self::$calculator = self::initializeCalculator(); |
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} |
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|
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return self::$calculator; |
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} |
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|
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/** |
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* @return Calculator |
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* |
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* @throws \RuntimeException If cannot find calculator for money calculations |
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*/ |
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private static function initializeCalculator() |
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{ |
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$calculators = self::$calculators; |
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|
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foreach ($calculators as $calculator) { |
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/** @var Calculator $calculator */ |
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if ($calculator::supported()) { |
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return new $calculator(); |
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} |
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} |
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|
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throw new \RuntimeException('Cannot find calculator for money calculations'); |
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} |
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} |
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|
