<?php namespace RVR\Finance;

use DateTime;
use RVR\PersistentData\Model\Currency;
use RVR\PersistentData\Model\CurrencyExchangeRate;
use RVR\Repository\CurrencyExchangeRateRepository;

class ExchangeRateCalculator
{
    private Currency $mainCurrency;

    private CurrencyExchangeRateRepository $currencyExchangeRateRepository;

    private array $exchangeRates = [];

    public function __construct(Currency $mainCurrency)
    {
        $this->mainCurrency = $mainCurrency;
        $this->currencyExchangeRateRepository = new CurrencyExchangeRateRepository();
    }

    public function calculate(float $sumInCurrency, Currency $currency, DateTime $time): float
    {
        if ($currency->getId() === $this->mainCurrency->getId()) {
            return $sumInCurrency;
        }

        $currentExchangeRate = $this->getCurrentExchangeRate($currency, $time);
        if ($currentExchangeRate === null) {
            return 0.0;
        }

        return $sumInCurrency * $currentExchangeRate->getExchangeRate();
    }

    private function getCurrentExchangeRate(Currency $currency, DateTime $time): ?CurrencyExchangeRate
    {
        if (!isset($this->exchangeRates[$currency->getId()])) {
            $this->exchangeRates[$currency->getId()] = iterator_to_array($this->currencyExchangeRateRepository->getAllByCurrency($currency));
        }

        $currentExchangeRate = null;
        foreach ($this->exchangeRates[$currency->getId()] as $exchangeRate) {
            if ($exchangeRate->getValidFromDate() > $time) {
                break;
            }
            $currentExchangeRate = $exchangeRate;
        }

        return $currentExchangeRate;
    }
}