rss-bridge/bridges/AmazonPriceTrackerBridge.php

<?php

class AmazonPriceTrackerBridge extends BridgeAbstract
{
    const MAINTAINER = 'captn3m0, sal0max';
    const NAME = 'Amazon Price Tracker';
    const URI = 'https://www.amazon.com/';
    const CACHE_TIMEOUT = 3600; // 1h
    const DESCRIPTION = 'Tracks price for a single product on Amazon';

    const PARAMETERS = [
        [
        'asin' => [
            'name'          => 'ASIN',
            'required'      => true,
            'exampleValue'  => 'B071GB1VMQ',
            // https://stackoverflow.com/a/12827734
            'pattern'       => 'B[\dA-Z]{9}|\d{9}(X|\d)',
        ],
        'tld' => [
            'name' => 'Country',
            'type' => 'list',
            'values' => [
                'Australia'         => 'com.au',
                'Brazil'        => 'com.br',
                'Canada'        => 'ca',
                'China'         => 'cn',
                'France'        => 'fr',
                'Germany'       => 'de',
                'India'         => 'in',
                'Italy'         => 'it',
                'Japan'         => 'co.jp',
                'Mexico'        => 'com.mx',
                'Netherlands'       => 'nl',
                'Spain'         => 'es',
                'Sweden'        => 'se',
                'Turkey'        => 'com.tr',
                'United Kingdom'    => 'co.uk',
                'United States'     => 'com',
            ],
            'defaultValue' => 'com',
        ],
        ]];

    const PRICE_SELECTORS = [
        '#priceblock_ourprice',
        '.priceBlockBuyingPriceString',
        '#newBuyBoxPrice',
        '#tp_price_block_total_price_ww',
        'span.offer-price',
        '.a-color-price',
    ];

    const WHITESPACE = " \t\n\r\0\x0B\xC2\xA0";

    protected $title;

    /**
     * Generates domain name given a amazon TLD
     */
    private function getDomainName()
    {
        return 'https://www.amazon.' . $this->getInput('tld');
    }

    /**
     * Generates URI for a Amazon product page
     */
    public function getURI()
    {
        if (!is_null($this->getInput('asin'))) {
            return $this->getDomainName() . '/dp/' . $this->getInput('asin');
        }
        return parent::getURI();
    }

    /**
     * Scrapes the product title from the html page
     * returns the default title if scraping fails
     */
    private function getTitle($html)
    {
        $titleTag = $html->find('#productTitle', 0);

        if (!$titleTag) {
            return $this->getDefaultTitle();
        } else {
            return trim(html_entity_decode($titleTag->innertext, ENT_QUOTES));
        }
    }

    /**
     * Title used by the feed if none could be found
     */
    private function getDefaultTitle()
    {
        return 'Amazon.' . $this->getInput('tld') . ': ' . $this->getInput('asin');
    }

    /**
     * Returns name for the feed
     * Uses title (already scraped) if it has one
     */
    public function getName()
    {
        if (isset($this->title)) {
            return $this->title;
        } else {
            return parent::getName();
        }
    }

    private function parseDynamicImage($attribute)
    {
        $json = json_decode(html_entity_decode($attribute), true);

        if ($json and count($json) > 0) {
            return array_keys($json)[0];
        }
    }

    /**
     * Returns a generated image tag for the product
     */
    private function getImage($html)
    {
        $imageSrc = $html->find('#main-image-container img', 0);

        if ($imageSrc) {
            $hiresImage = $imageSrc->getAttribute('data-old-hires');
            $dynamicImageAttribute = $imageSrc->getAttribute('data-a-dynamic-image');
            $image = $hiresImage ?: $this->parseDynamicImage($dynamicImageAttribute);
        }
        $image = $image ?: 'https://placekitten.com/200/300';

        return <<<EOT
<img width="300" style="max-width:300;max-height:300" src="$image" alt="{$this->title}" />
EOT;
    }

    /**
     * Return \simple_html_dom object
     * for the entire html of the product page
     */
    private function getHtml()
    {
        $uri = $this->getURI();

        return getSimpleHTMLDOM($uri) ?: returnServerError('Could not request Amazon.');
    }

    private function scrapePriceFromMetrics($html)
    {
        $asinData = $html->find('#cerberus-data-metrics', 0);

        // <div id="cerberus-data-metrics" style="display: none;"
        //  data-asin="B00WTHJ5SU" data-asin-price="14.99" data-asin-shipping="0"
        //  data-asin-currency-code="USD" data-substitute-count="-1" ... />
        if ($asinData) {
            return [
                'price'     => $asinData->getAttribute('data-asin-price'),
                'currency'  => $asinData->getAttribute('data-asin-currency-code'),
                'shipping'  => $asinData->getAttribute('data-asin-shipping')
            ];
        }

        return false;
    }

    private function scrapePriceTwister($html)
    {
        $str = $html->find('.twister-plus-buying-options-price-data', 0);

        $data = json_decode($str->innertext, true);
        if (count($data) === 1) {
            $data = $data[0];
            return [
                'displayPrice' => $data['displayPrice'],
                'currency' => $data['currency'],
                'shipping' => '0',
            ];
        }

        return false;
    }

    private function scrapePriceGeneric($html)
    {
        $priceDiv = null;

        foreach (self::PRICE_SELECTORS as $sel) {
            $priceDiv = $html->find($sel, 0);
            if ($priceDiv) {
                break;
            }
        }

        if (!$priceDiv) {
            return false;
        }

        $priceString = str_replace(str_split(self::WHITESPACE), '', $priceDiv->plaintext);
        preg_match('/(\d+\.\d{0,2})/', $priceString, $matches);

        $price = $matches[0];
        $currency = str_replace($price, '', $priceString);

        if ($price != null && $currency != null) {
            return [
                'price'     => $price,
                'currency'  => $currency,
                'shipping'  => '0'
            ];
        }

        return false;
    }

    private function renderContent($image, $data)
    {
        $price = $data['displayPrice'];
        if (!$price) {
            $price = "{$data['price']} {$data['currency']}";
        }

        $html = "$image<br>Price: $price";

        if ($data['shipping'] !== '0') {
            $html .= "<br>Shipping: {$data['shipping']} {$data['currency']}</br>";
        }

        return $html;
    }

    /**
     * Scrape method for Amazon product page
     * @return [type] [description]
     */
    public function collectData()
    {
        $html = $this->getHtml();
        $this->title = $this->getTitle($html);
        $imageTag = $this->getImage($html);

        $data = $this->scrapePriceGeneric($html);

        $item = [
            'title'     => $this->title,
            'uri'       => $this->getURI(),
            'content'   => $this->renderContent($imageTag, $data),
            // This is to ensure that feed readers notice the price change
            'uid'       => md5($data['price'])
        ];

        $this->items[] = $item;
    }
}