import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class DangDangCrawlStrategy extends AbstractCrawlStrategy<CrawlResult> {
    
    private static final String BASE_URL = "http://bang.dangdang.com/books/bestsellers/%d";

    public String getBaseUrl() {
        return BASE_URL;
    }

    public List<CrawlResult> crawlPage(int page) throws IOException {
        List<CrawlResult> results = new ArrayList<CrawlResult>();
        String url = String.format(BASE_URL, page);
        Document doc = fetchDocument(url);
        
        Elements bookElements = doc.select("li.clearfix");
        if (bookElements.isEmpty()) {
            bookElements = doc.select("li");
        }

        for (Element e : bookElements) {
            CrawlResult result = parseItem(e);
            if (result != null) {
                results.add(result);
            }
        }
        return results;
    }

    public CrawlResult parseItem(Element element) {
        String title = element.select("a[title]").attr("title");
        if (title == null || title.isEmpty() || title.length() < 10) {
            title = element.select(".name a").text();
        }
        if (title == null || title.isEmpty() || title.length() < 10) {
            return null;
        }

        String priceText = element.select("span.price_n").text();
        if (priceText.isEmpty()) priceText = element.select(".price").text();
        if (priceText.isEmpty()) priceText = element.select("[class*=price]").text();

        String originalPriceText = element.select("span.price_r").text();
        if (originalPriceText.isEmpty()) originalPriceText = priceText;

        String imageUrl = element.select("img").attr("src");
        if (imageUrl.isEmpty()) imageUrl = element.select("img").attr("data-original");
        if (imageUrl.isEmpty()) imageUrl = element.select("img").attr("data-src");

        String author = element.select("span.author").text();
        if (author.isEmpty()) author = element.select("[class*=author]").text();
        if (author.isEmpty()) author = "DangDang";

        double price = parsePrice(priceText);
        double originalPrice = parsePrice(originalPriceText);
        double discount = parseDiscount(price, originalPrice);

        return new CrawlResult(title, price, originalPrice, discount, imageUrl, author);
    }
}