Rewrite cache and exchange rate tables functionality

README.md

@@ -19,9 +19,17 @@ $ composer require ksdev/nbp-currency-converter
 ## Usage
 
 ``` php
-$converter = new Ksdev\NBPCurrencyConverter(
-    new GuzzleHttp\Client(), 
-    'path/to/cache/folder'
+use Ksdev\NBPCurrencyConverter\CurrencyConverter;
+use Ksdev\NBPCurrencyConverter\ExRatesDayTableFinder;
+use Ksdev\NBPCurrencyConverter\ExRatesDayTableFactory;
+use GuzzleHttp\Client;
+
+$converter = new CurrencyConverter(
+    new ExRatesDayTableFinder(
+        new Client(),
+        new ExRatesDayTableFactory(),
+        'path/to/cache/folder'
+    )
 );
 try {
     $result = $converter->convert('123.4567', 'PLN', 'USD')

src/CurrencyConverter.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Ksdev\NBPCurrencyConverter;
+
+class CurrencyConverter
+{
+    private $ratesTableFinder;
+
+    public function __construct(ExRatesDayTableFinder $ratesTableFinder)
+    {
+        $this->ratesTableFinder = $ratesTableFinder;
+    }
+
+    /**
+     * Get the average exchange rates
+     *
+     * @param \DateTime $pubDate Optional rates table publication date
+     *
+     * @return array
+     *
+     * @throws \Exception
+     */
+    public function averageExchangeRates(\DateTime $pubDate = null)
+    {
+        $file = $this->ratesTableFinder->getExRatesDayTable($pubDate);
+        return $file->parsedContent;
+    }
+
+    /**
+     * Convert amount from one currency to another
+     *
+     * @param string $fromAmount Amount with four digits after decimal point, e.g. '123.0000'
+     * @param string $fromCurrency E.g. 'USD' or 'EUR'
+     * @param string $toCurrency E.g. 'USD' or 'EUR'
+     * @param \DateTime $pubDate Optional rates table publication date
+     *
+     * @return array
+     *
+     * @throws \Exception
+     */
+    public function convert($fromAmount, $fromCurrency, $toCurrency, \DateTime $pubDate = null)
+    {
+        if (!preg_match('/^\d+\.(\d{4})$/', $fromAmount)) {
+            throw new \Exception('Invalid format of amount');
+        }
+
+        $rates = $this->averageExchangeRates($pubDate);
+
+        $fromCurrency = strtoupper($fromCurrency);
+        $toCurrency = strtoupper($toCurrency);
+        if (!isset($rates['waluty'][$fromCurrency]) || !isset($rates['waluty'][$toCurrency])) {
+            throw new \Exception('Invalid currency code');
+        }
+
+        $fromMultiplier = str_replace(',', '.', $rates['waluty'][$fromCurrency]['przelicznik']);
+        $fromAverageRate = str_replace(',', '.', $rates['waluty'][$fromCurrency]['kurs_sredni']);
+        $toMultiplier = str_replace(',', '.', $rates['waluty'][$toCurrency]['przelicznik']);
+        $toAverageRate = str_replace(',', '.', $rates['waluty'][$toCurrency]['kurs_sredni']);
+
+        bcscale(6);
+        $plnAmount = bcdiv(bcmul($fromAmount, $fromAverageRate), $fromMultiplier);
+        $resultAmount = bcdiv(bcmul($plnAmount, $toMultiplier), $toAverageRate);
+        $roundedResult = BCMathHelper::bcround($resultAmount, 4);
+
+        return [
+            'publication_date' => $rates['data_publikacji'],
+            'amount'   => $roundedResult,
+            'currency' => $toCurrency
+        ];
+    }
+}

src/ExRatesDayTable.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace Ksdev\NBPCurrencyConverter;
+
+class ExRatesDayTable
+{
+    /** @var string */
+    public $rawContent;
+
+    /** @var array */
+    public $parsedContent;
+
+    /**
+     * @param string $rawContent Raw xml content
+     *
+     * @throws \Exception
+     */
+    public function __construct($rawContent)
+    {
+        $this->rawContent = $rawContent;
+        $this->parsedContent = $this->parseXml($rawContent);
+    }
+
+    /**
+     * Transform the raw xml content into an array
+     *
+     * @param string $rawContent
+     *
+     * @return array
+     *
+     * @throws \Exception
+     */
+    private function parseXml($rawContent)
+    {
+        $xml = new \SimpleXMLElement($rawContent);
+        if (empty($xml->numer_tabeli) || empty($xml->data_publikacji) || empty($xml->pozycja)) {
+            throw new \Exception('Invalid xml response content');
+        }
+        $rates = [
+            'numer_tabeli'    => (string)$xml->numer_tabeli,
+            'data_publikacji' => (string)$xml->data_publikacji,
+            'waluty'          => [
+                'PLN' => [
+                    'nazwa_waluty' => 'złoty polski',
+                    'przelicznik'  => '1',
+                    'kurs_sredni'  => '1'
+                ]
+            ]
+        ];
+        foreach ($xml->pozycja as $pozycja) {
+            $rates['waluty'] += [
+                (string)$pozycja->kod_waluty => [
+                    'nazwa_waluty' => (string)$pozycja->nazwa_waluty,
+                    'przelicznik'  => (string)$pozycja->przelicznik,
+                    'kurs_sredni'  => (string)$pozycja->kurs_sredni
+                ]
+            ];
+        }
+        return $rates;
+    }
+}

src/ExRatesDayTableFactory.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Ksdev\NBPCurrencyConverter;
+
+class ExRatesDayTableFactory
+{
+    /**
+     * Get new ExRatesDayTable
+     *
+     * @param string $rawContent Raw xml content
+     *
+     * @return ExRatesDayTable
+     */
+    public function getInstance($rawContent)
+    {
+        return new ExRatesDayTable($rawContent);
+    }
+}

src/ExRatesDayTableFinder.php

@@ -0,0 +1,217 @@
+<?php
+
+namespace Ksdev\NBPCurrencyConverter;
+
+class ExRatesDayTableFinder
+{
+    const NBP_XML_URL = 'http://www.nbp.pl/kursy/xml/';
+    const MAX_ONE_TIME_API_REQ = 7;
+
+    /** @var \GuzzleHttp\Client */
+    private $guzzle;
+
+    /** @var ExRatesDayTableFactory */
+    private $ratesTableFactory;
+
+    /** @var string */
+    private $cachePath;
+
+    /** @var \DateTime */
+    private $soughtPubDate;
+
+    /**
+     * @param \GuzzleHttp\Client $guzzle
+     * @param ExRatesDayTableFactory $ratesTableFactory
+     * @param string $cachePath Optional path to an existing folder where the cache files will be stored
+     *
+     * @throws \Exception
+     */
+    public function __construct(
+        \GuzzleHttp\Client $guzzle,
+        ExRatesDayTableFactory $ratesTableFactory,
+        $cachePath = ''
+    ) {
+        $this->guzzle = $guzzle;
+        $this->ratesTableFactory = $ratesTableFactory;
+        if ($cachePath) {
+            if (!is_dir($cachePath)) {
+                throw new \Exception('Invalid cache path');
+            }
+            $this->cachePath = rtrim((string)$cachePath, '/') . '/';
+        }
+    }
+
+    /**
+     * Get the ExRatesDayTable instance
+     *
+     * @param \DateTime $pubDate Optional rates table publication date
+     *
+     * @return ExRatesDayTable
+     *
+     * @throws \Exception
+     */
+    public function getExRatesDayTable(\DateTime $pubDate = null)
+    {
+        $this->setSoughtPubDate($pubDate);
+
+        $i = 0;
+        do {
+            // Limit the number of times the loop repeats
+            if ($i === self::MAX_ONE_TIME_API_REQ) {
+                throw new \Exception('Max request to api limit has been reached');
+            }
+
+            // If user doesn't want a specific date, try to get the rates from the last working day
+            if (!$pubDate) {
+                $this->soughtPubDate = $this->soughtPubDate->sub(new \DateInterval('P1D'));
+            }
+
+            // Try to find the file in cache, otherwise download it
+            if ($this->cachePath && ($cachedXml = $this->getCachedXml())) {
+                $rawContent = $cachedXml;
+            } else {
+                $rawContent = $this->downloadXml();
+            }
+
+            // If a specific date is sought then break, otherwise continue
+            if ($pubDate) {
+                break;
+            }
+
+            $i++;
+        } while (!$rawContent);
+
+        if (!$rawContent) {
+            throw new \Exception('Exchange rates file not found');
+        }
+
+        return $this->ratesTableFactory->getInstance($rawContent);
+    }
+
+    /**
+     * Set the sought publication date necessary for finder operation
+     *
+     * @param \DateTime|null $pubDate
+     *
+     * @throws \Exception
+     */
+    private function setSoughtPubDate($pubDate)
+    {
+        if ($pubDate instanceof \DateTime) {
+            if (!($pubDate >= new \DateTime('2002-01-02') && $pubDate <= new \DateTime())) {
+                throw new \Exception('Invalid publication date');
+            }
+        } else {
+            $pubDate = new \DateTime();
+        }
+        $this->soughtPubDate = $pubDate;
+    }
+
+    /**
+     * Get the raw xml content from a cache file
+     *
+     * @return string|int Content string or 0 if the file doesn't exist
+     */
+    private function getCachedXml()
+    {
+        $filesArray = scandir($this->cachePath);
+        $filename = $this->matchFilename($filesArray);
+
+        if ($filename) {
+            $rawContent = file_get_contents($this->cachePath . $filename);
+            return $rawContent;
+        }
+
+        return 0;
+    }
+
+    /**
+     * Get the raw xml content from the NBP api
+     *
+     * @return string|int Content string or 0 if the file doesn't exist
+     *
+     * @throws \Exception
+     */
+    private function downloadXml()
+    {
+        $filename = $this->findFileInRatesDir();
+        if ($filename) {
+            $response = $this->guzzle->get(self::NBP_XML_URL . $filename);
+            if ($response->getStatusCode() === 200) {
+                $rawContent = (string)$response->getBody();
+                if ($this->cachePath) {
+                    file_put_contents($this->cachePath . $filename, $rawContent);
+                }
+                return $rawContent;
+            } else {
+                throw new \Exception(
+                    "Invalid response status code: {$response->getStatusCode()} {$response->getReasonPhrase()}"
+                );
+            }
+        } else {
+            return 0;
+        }
+    }
+
+    /**
+     * Find the file related to the publication date
+     *
+     * @return string|int Filename or 0 if the file was not found
+     *
+     * @throws \Exception
+     */
+    private function findFileInRatesDir()
+    {
+        $dirname = $this->constructDirname();
+
+        $response = $this->guzzle->get(self::NBP_XML_URL . $dirname);
+        if ($response->getStatusCode() === 200) {
+            $rawContent = (string)$response->getBody();
+        } else {
+            throw new \Exception(
+                "Invalid response status code: {$response->getStatusCode()} {$response->getReasonPhrase()}"
+            );
+        }
+
+        $filesArray = explode("\r\n", $rawContent);
+        $filename = $this->matchFilename($filesArray);
+
+        return $filename;
+    }
+
+    /**
+     * Construct the name of directory containing the files
+     *
+     * @return string
+     */
+    private function constructDirname()
+    {
+        if ($this->soughtPubDate->format('Y') !== (new \DateTime())->format('Y')) {
+            $dirname = "dir{$this->soughtPubDate->format('Y')}.txt";
+        } else {
+            $dirname = 'dir.txt';
+        }
+        return $dirname;
+    }
+
+    /**
+     * Searches files array for a match to the publication date
+     *
+     * @todo Optimize to avoid unnecessary regex
+     *
+     * @param array $filesArray
+     *
+     * @return string|int Filename or 0 if the file was not found
+     */
+    private function matchFilename(array $filesArray)
+    {
+        foreach ($filesArray as $filename) {
+            if (preg_match('/(a\d{3}z' . $this->soughtPubDate->format('ymd') . ')/', $filename, $matches)) {
+                $filename = "{$matches[1]}.xml";
+                return $filename;
+            }
+        }
+
+        return 0;
+    }
+}