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A java library for reading/writing/manipulating epub files
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package nl.siegmann.epublib.epub;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.xml.namespace.QName;

import nl.siegmann.epublib.domain.Author;
import nl.siegmann.epublib.domain.Date;
import nl.siegmann.epublib.domain.Identifier;
import nl.siegmann.epublib.domain.Metadata;
import nl.siegmann.epublib.util.StringUtil;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 * Reads the package document metadata.
 * 
 * In its own separate class because the PackageDocumentReader became a bit large and unwieldy.
 * 
 * @author paul
 *
 */
// package
class PackageDocumentMetadataReader extends PackageDocumentBase {

	private static final Logger log = LoggerFactory.getLogger(PackageDocumentMetadataReader.class);

	public static Metadata readMetadata(Document packageDocument) {
		Metadata result = new Metadata();
		Element metadataElement = DOMUtil.getFirstElementByTagNameNS(packageDocument.getDocumentElement(), NAMESPACE_OPF, OPFTags.metadata);
		if(metadataElement == null) {
			log.error("Package does not contain element " + OPFTags.metadata);
			return result;
		}
		result.setTitles(DOMUtil.getElementsTextChild(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.title));
		result.setPublishers(DOMUtil.getElementsTextChild(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.publisher));
		result.setDescriptions(DOMUtil.getElementsTextChild(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.description));
		result.setRights(DOMUtil.getElementsTextChild(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.rights));
		result.setTypes(DOMUtil.getElementsTextChild(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.type));
		result.setSubjects(DOMUtil.getElementsTextChild(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.subject));
		result.setIdentifiers(readIdentifiers(metadataElement));
		result.setAuthors(readCreators(metadataElement));
		result.setContributors(readContributors(metadataElement));
		result.setDates(readDates(metadataElement));
        result.setOtherProperties(readOtherProperties(metadataElement));
        result.setMetaAttributes(readMetaProperties(metadataElement));
        Element languageTag = DOMUtil.getFirstElementByTagNameNS(metadataElement, NAMESPACE_DUBLIN_CORE, DCTags.language);
        if (languageTag != null) {
            result.setLanguage(DOMUtil.getTextChildrenContent(languageTag));
        }


		return result;
	}
	
	/**
	 * consumes meta tags that have a property attribute as defined in the standard. For example:
	 * <meta property="rendition:layout">pre-paginated</meta>
	 * @param metadataElement
	 * @return
	 */
	private static Map readOtherProperties(Element metadataElement) {
		Map result = new HashMap();
		
		NodeList metaTags = metadataElement.getElementsByTagNameNS(NAMESPACE_OPF, OPFTags.meta);
		for (int i = 0; i < metaTags.getLength(); i++) {
			Node metaNode = metaTags.item(i);
			Node property = metaNode.getAttributes().getNamedItem(OPFAttributes.property);
			if (property != null) {
				String name = property.getNodeValue();
				String value = metaNode.getTextContent();
				result.put(new QName(name), value);
			}
		}
		
		return result;
	}

	/**
	 * consumes meta tags that have a property attribute as defined in the standard. For example:
	 * <meta property="rendition:layout">pre-paginated</meta>
	 * @param metadataElement
	 * @return
	 */
	private static Map readMetaProperties(Element metadataElement) {
		Map result = new HashMap();
		
		NodeList metaTags = metadataElement.getElementsByTagName(OPFTags.meta);
		for (int i = 0; i < metaTags.getLength(); i++) {
			Element metaElement = (Element) metaTags.item(i);
			String name = metaElement.getAttribute(OPFAttributes.name);
			String value = metaElement.getAttribute(OPFAttributes.content);
			result.put(name,  value);
		}
		
		return result;
	}

	private static String getBookIdId(Document document) {
		Element packageElement = DOMUtil.getFirstElementByTagNameNS(document.getDocumentElement(), NAMESPACE_OPF, OPFTags.packageTag);
		if(packageElement == null) {
			return null;
		}
		String result = packageElement.getAttributeNS(NAMESPACE_OPF, OPFAttributes.uniqueIdentifier);
		return result;
	}
		
	private static List readCreators(Element metadataElement) {
		return readAuthors(DCTags.creator, metadataElement);
	}
	
	private static List readContributors(Element metadataElement) {
		return readAuthors(DCTags.contributor, metadataElement);
	}
	
	private static List readAuthors(String authorTag, Element metadataElement) {
		NodeList elements = metadataElement.getElementsByTagNameNS(NAMESPACE_DUBLIN_CORE, authorTag);
		List result = new ArrayList(elements.getLength());
		for(int i = 0; i < elements.getLength(); i++) {
			Element authorElement = (Element) elements.item(i);
			Author author = createAuthor(authorElement);
			if (author != null) {
				result.add(author);
			}
		}
		return result;
		
	}

	private static List readDates(Element metadataElement) {
		NodeList elements = metadataElement.getElementsByTagNameNS(NAMESPACE_DUBLIN_CORE, DCTags.date);
		List result = new ArrayList(elements.getLength());
		for(int i = 0; i < elements.getLength(); i++) {
			Element dateElement = (Element) elements.item(i);
			Date date;
			try {
				date = new Date(DOMUtil.getTextChildrenContent(dateElement), dateElement.getAttributeNS(NAMESPACE_OPF, OPFAttributes.event));
				result.add(date);
			} catch(IllegalArgumentException e) {
				log.error(e.getMessage());
			}
		}
		return result;
		
	}

	private static Author createAuthor(Element authorElement) {
		String authorString = DOMUtil.getTextChildrenContent(authorElement);
		if (StringUtil.isBlank(authorString)) {
			return null;
		}
		int spacePos = authorString.lastIndexOf(' ');
		Author result;
		if(spacePos < 0) {
			result = new Author(authorString);
		} else {
			result = new Author(authorString.substring(0, spacePos), authorString.substring(spacePos + 1));
		}
		result.setRole(authorElement.getAttributeNS(NAMESPACE_OPF, OPFAttributes.role));
		return result;
	}
	
	
	private static List readIdentifiers(Element metadataElement) {
		NodeList identifierElements = metadataElement.getElementsByTagNameNS(NAMESPACE_DUBLIN_CORE, DCTags.identifier);
		if(identifierElements.getLength() == 0) {
			log.error("Package does not contain element " + DCTags.identifier);
			return new ArrayList();
		}
		String bookIdId = getBookIdId(metadataElement.getOwnerDocument());
		List result = new ArrayList(identifierElements.getLength());
		for(int i = 0; i < identifierElements.getLength(); i++) {
			Element identifierElement = (Element) identifierElements.item(i);
			String schemeName = identifierElement.getAttributeNS(NAMESPACE_OPF, DCAttributes.scheme);
			String identifierValue = DOMUtil.getTextChildrenContent(identifierElement);
			if (StringUtil.isBlank(identifierValue)) {
				continue;
			}
			Identifier identifier = new Identifier(schemeName, identifierValue);
			if(identifierElement.getAttribute("id").equals(bookIdId) ) {
				identifier.setBookId(true);
			}
			result.add(identifier);
		}
		return result;
	}
}