/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */
package org.purl.sword.atom;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Properties;

import nu.xom.Element;
import nu.xom.Elements;
import org.apache.logging.log4j.Logger;
import org.purl.sword.base.HttpHeaders;
import org.purl.sword.base.Namespaces;
import org.purl.sword.base.SwordElementInterface;
import org.purl.sword.base.SwordValidationInfo;
import org.purl.sword.base.SwordValidationInfoType;
import org.purl.sword.base.UnmarshallException;
import org.purl.sword.base.XmlElement;
import org.purl.sword.base.XmlName;

/**
 * Represents an ATOM entry.
 *
 * @author Neil Taylor
 */
public class Entry extends XmlElement implements SwordElementInterface {
    /**
     * Local name for the element.
     */
    @Deprecated
    public static final String ELEMENT_NAME = "entry";

    /**
     * Local name for the atom id element.
     */
    @Deprecated
    public static final String ELEMENT_ID = "id";

    /**
     * Local name for the atom published element.
     */
    @Deprecated
    public static final String ELEMENT_PUBLISHED = "published";

    /**
     * Local name for the atom updated element.
     */
    @Deprecated
    public static final String ELEMENT_UPDATED = "updated";

    /**
     * Local name for the atom category element.
     */
    @Deprecated
    public static final String ELEMENT_CATEGORY = "category";

    /**
     * Local name for the atom generator element.
     */
    @Deprecated
    public static final String ELEMENT_GENERATOR = "generator";

    /**
     * A list of authors associated with this entry. There can be 0
     * or more of these elements.
     */
    private List<Author> authors;

    /**
     * The atom:category data. There can be 0 or more of these elements.
     */
    private List<Category> categories;

    /**
     * A single content element for the Entry.
     */
    private Content content;

    /**
     * A single content element for the Entry.
     */
    private Generator generator;

    /**
     * A list of contributors associated with this entry. There can be 0 or
     * more of these elements.
     */
    private List<Contributor> contributors;

    /**
     * This is a simplified version. The ID can also have atomCommonAttributes,
     * but these have not been modeled in this version. The content of
     * ID is an unconstrained string, which is intended to represent a URI.
     */
    private Id id;

    /**
     * A list of link elements. This can contain 0 or more entries.
     */
    private List<Link> links;

    /**
     * Simplified version of the atom:published element. This implementation
     * does not record the general atomCommonAttributes. The date is
     * taken from an xsd:dateTime value.
     *
     * This item is optional.
     */
    private Published published;

    /**
     * A single, optional, content element for the Entry.
     */
    private Rights rights;

    /**
     * A single, optional, content element for the Entry.
     */
    @Deprecated
    private Source source;

    /**
     * A single, optional, summary element for the Entry.
     */
    private Summary summary;

    /**
     * A required title element for the entry.
     */
    private Title title;

    /**
     * The date on which the entry was last updated.
     */
    private Updated updated;

    /**
     * The log.
     */
    private static Logger log = org.apache.logging.log4j.LogManager.getLogger(Entry.class);

    /**
     * The prefix, local name and namespace used for this element.
     */
    private static final XmlName XML_NAME =
        new XmlName(Namespaces.PREFIX_ATOM, "entry", Namespaces.NS_ATOM);

    /**
     * Create a new instance of the class and initialise it.
     * Also, set the prefix to 'atom' and the local name to 'entry'.
     */
    public Entry() {
        this(XML_NAME.getPrefix(),
             XML_NAME.getLocalName(),
             XML_NAME.getNamespace());
    }

    /**
     * Create a new instance of the class an initalise it, setting the
     * element namespace and name.
     *
     * @param prefix  The namespace prefix of the element
     * @param element The element name
     */
    public Entry(String prefix, String element) {
        this(prefix, element, XML_NAME.getNamespace());
    }

    /**
     * @param prefix       The prefix.
     * @param element      element name.
     * @param namespaceUri The namespace URI.
     */
    public Entry(String prefix, String element, String namespaceUri) {
        super(prefix, element, namespaceUri);
        initialise();
    }

    public Entry(XmlName name) {
        this(name.getPrefix(), name.getLocalName(), name.getNamespace());
    }


    public static XmlName elementName() {
        return XML_NAME;
    }

    protected boolean isElementChecked(XmlName elementName) {
        if (elementName == null) {
            return false;
        }

        return elementName.equals(Author.elementName()) |
            elementName.equals(Category.elementName()) |
            elementName.equals(Content.elementName()) |
            elementName.equals(Generator.elementName()) |
            elementName.equals(Contributor.elementName()) |
            elementName.equals(Id.elementName()) |
            elementName.equals(Link.elementName()) |
            elementName.equals(Published.elementName()) |
            elementName.equals(Rights.elementName()) |
            elementName.equals(Source.elementName()) |
            elementName.equals(Summary.elementName()) |
            elementName.equals(Title.elementName()) |
            elementName.equals(Updated.elementName());
    }

    /**
     *
     */
    protected void initialise() {
        authors = new ArrayList<>();
        categories = new ArrayList<>();
        contributors = new ArrayList<>();
        links = new ArrayList<>();
    }

    /**
     * Marshal the data stored in this object into Element objects.
     *
     * @return An element that holds the data associated with this object.
     */
    @Override
    public Element marshall() {
        Element entry = new Element(getQualifiedName(), Namespaces.NS_ATOM);
        entry.addNamespaceDeclaration(Namespaces.PREFIX_SWORD, Namespaces.NS_SWORD);
        entry.addNamespaceDeclaration(Namespaces.PREFIX_ATOM, Namespaces.NS_ATOM);
        this.marshallElements(entry);
        return entry;
    }

    protected void marshallElements(Element entry) {
        if (id != null) {
            entry.appendChild(id.marshall());
        }

        for (Author author : authors) {
            entry.appendChild(author.marshall());
        }

        if (content != null) {
            entry.appendChild(content.marshall());
        }

        if (generator != null) {
            entry.appendChild(generator.marshall());
        }

        for (Author contributor : contributors) {
            entry.appendChild(contributor.marshall());
        }

        for (Link link : links) {
            entry.appendChild(link.marshall());
        }

        if (published != null) {
            entry.appendChild(published.marshall());
        }

        if (rights != null) {
            entry.appendChild(rights.marshall());
        }

        if (summary != null) {
            entry.appendChild(summary.marshall());
        }

        if (title != null) {
            entry.appendChild(title.marshall());
        }

        if (source != null) {
            entry.appendChild(source.marshall());
        }

        if (updated != null) {
            entry.appendChild(updated.marshall());
        }

        for (Category category : categories) {
            entry.appendChild(category.marshall());
        }
    }

    /**
     * Unmarshal the contents of the Entry element into the internal data objects
     * in this object.
     *
     * @param entry The Entry element to process.
     * @throws UnmarshallException If the element does not contain an ATOM entry
     *                             element, or if there is a problem processing the element or any
     *                             subelements.
     */
    @Override
    public void unmarshall(Element entry)
        throws UnmarshallException {
        unmarshall(entry, null);
    }

    public SwordValidationInfo unmarshallWithoutValidate(Element entry, Properties validationProperties)
        throws UnmarshallException {
        if (!isInstanceOf(entry, xmlName)) {
            return handleIncorrectElement(entry, validationProperties);
        }

        // used to hold the element and attribute unmarshal info results
        SwordValidationInfo result = new SwordValidationInfo(xmlName);

        try {
            initialise();

            // FIXME - attributes?

            // retrieve all of the sub-elements
            Elements elements = entry.getChildElements();
            Element element = null;
            int length = elements.size();

            for (int i = 0; i < length; i++) {
                element = elements.get(i);

                if (isInstanceOf(element, Author.elementName())) {
                    Author author = new Author();
                    result.addUnmarshallElementInfo(author.unmarshall(element, validationProperties));
                    authors.add(author);
                } else if (isInstanceOf(element, Category.elementName())) {
                    Category category = new Category();
                    result.addUnmarshallElementInfo(category.unmarshall(element, validationProperties));
                    categories.add(category);
                } else if (isInstanceOf(element, Content.elementName())) {
                    if (content == null) {
                        content = new Content();
                        result.addUnmarshallElementInfo(content.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Content.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }

                } else if (isInstanceOf(element, Generator.elementName())) {
                    if (generator == null) {
                        generator = new Generator();
                        result.addUnmarshallElementInfo(generator.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Generator.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Contributor.elementName())) {
                    Contributor contributor = new Contributor();
                    result.addUnmarshallElementInfo(contributor.unmarshall(element, validationProperties));
                    contributors.add(contributor);
                } else if (isInstanceOf(element, Id.elementName())) {
                    if (id == null) {
                        id = new Id();
                        result.addUnmarshallElementInfo(id.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Id.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Link.elementName())) {
                    Link link = new Link();
                    result.addUnmarshallElementInfo(link.unmarshall(element, validationProperties));
                    links.add(link);
                } else if (isInstanceOf(element, Published.elementName())) {
                    if (published == null) {
                        published = new Published();
                        result.addUnmarshallElementInfo(published.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Published.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Rights.elementName())) {
                    if (rights == null) {
                        rights = new Rights();
                        result.addUnmarshallElementInfo(rights.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Rights.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Summary.elementName())) {
                    if (summary == null) {
                        summary = new Summary();
                        result.addUnmarshallElementInfo(summary.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Summary.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Title.elementName())) {
                    if (title == null) {
                        title = new Title();
                        result.addUnmarshallElementInfo(title.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Title.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Updated.elementName())) {
                    if (updated == null) {
                        updated = new Updated();
                        result.addUnmarshallElementInfo(updated.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Updated.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (isInstanceOf(element, Source.elementName())) {
                    if (source == null) {
                        source = new Source();
                        result.addUnmarshallElementInfo(source.unmarshall(element, validationProperties));
                    } else if (validationProperties != null) {
                        SwordValidationInfo info = new SwordValidationInfo(Source.elementName(),
                                                                           SwordValidationInfo.DUPLICATE_ELEMENT,
                                                                           SwordValidationInfoType.WARNING);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                } else if (validationProperties != null) {
                    XmlName name = new XmlName(element);
                    if (!isElementChecked(name)) {
                        SwordValidationInfo info = new SwordValidationInfo(name,
                                                                           SwordValidationInfo.UNKNOWN_ELEMENT,
                                                                           SwordValidationInfoType.INFO);
                        info.setContentDescription(element.getValue());
                        result.addUnmarshallElementInfo(info);
                    }
                }

            } // for
        } catch (Exception ex) {
            log.error("Unable to parse an element in Entry: " + ex.getMessage());
            ex.printStackTrace();
            throw new UnmarshallException("Unable to parse an element in " + getQualifiedName(), ex);
        }

        return result;
    }

    public SwordValidationInfo unmarshall(Element entry, Properties validationProperties)
        throws UnmarshallException {

        SwordValidationInfo result = unmarshallWithoutValidate(entry, validationProperties);
        if (validationProperties != null) {
            result = validate(result, validationProperties);
        }
        return result;
    }

    /**
     * @param validationContext FIXME: PLEASE DOCUMENT.
     * @return SWORD validation info.
     */
    @Override
    public SwordValidationInfo validate(Properties validationContext) {
        return validate(null, validationContext);
    }

    /**
     * @param info              add results to this.  If null, a new one is created.
     * @param validationContext FIXME: PLEASE DOCUMENT.
     * @return SWORD validation info
     */
    protected SwordValidationInfo validate(SwordValidationInfo info,
                                           Properties validationContext) {
        // determine if a full validation is required
        boolean validateAll = (info == null);

        SwordValidationInfo result = info;
        if (result == null) {
            result = new SwordValidationInfo(xmlName);
        }

        // id, title an updated are required
        if (id == null) {
            result.addValidationInfo(new SwordValidationInfo(Id.elementName(),
                                                             SwordValidationInfo.MISSING_ELEMENT_ERROR,
                                                             SwordValidationInfoType.ERROR));
        } else if (validateAll) {
            result.addValidationInfo(id.validate(validationContext));
        }

        if (title == null) {
            result.addValidationInfo(new SwordValidationInfo(Title.elementName(),
                                                             SwordValidationInfo.MISSING_ELEMENT_ERROR,
                                                             SwordValidationInfoType.ERROR));
        } else if (validateAll) {
            result.addValidationInfo(title.validate(validationContext));
        }

        if (updated == null) {
            result.addValidationInfo(new SwordValidationInfo(Updated.elementName(),
                                                             SwordValidationInfo.MISSING_ELEMENT_ERROR,
                                                             SwordValidationInfoType.ERROR));
        } else if (validateAll) {
            result.addValidationInfo(updated.validate(validationContext));
        }

        // additional sword requirements on the element
        if (contributors.isEmpty()) {
            String contributor = validationContext.getProperty(HttpHeaders.X_ON_BEHALF_OF);
            if (contributor != null) {
                result.addValidationInfo(new SwordValidationInfo(Contributor.elementName(),
                                                                 SwordValidationInfo.MISSING_ELEMENT_ERROR +
                                                                     " This item SHOULD contain the value of the " +
                                                                     "X-On-Behalf-Of header, if one was present in " +
                                                                     "the POST request.",
                                                                 SwordValidationInfoType.ERROR));
            }
        } else if ((!contributors.isEmpty()) && validateAll) {
            Iterator<Contributor> iterator = contributors.iterator();
            while (iterator.hasNext()) {
                Contributor contributor = iterator.next();
                result.addValidationInfo(contributor.validate(validationContext));
            }
        }

        if (generator == null) {
            result.addValidationInfo(new SwordValidationInfo(Generator.elementName(),
                                                             SwordValidationInfo.MISSING_ELEMENT_ERROR +
                                                                 " SHOULD contain the URI and version of the server " +
                                                                 "software.",
                                                             SwordValidationInfoType.ERROR));
        } else if (validateAll) {
            result.addValidationInfo(generator.validate(validationContext));
        }

        if (validateAll) {
            // process the remaining items
            Iterator<Link> linksIterator = links.iterator();
            while (linksIterator.hasNext()) {
                Link link = linksIterator.next();
                result.addValidationInfo(link.validate(validationContext));
            }

            Iterator<Author> authorIterator = authors.iterator();
            while (authorIterator.hasNext()) {
                Author author = authorIterator.next();
                result.addValidationInfo(author.validate(validationContext));
            }

            if (content != null) {
                result.addValidationInfo(content.validate(validationContext));
            }

            if (published != null) {
                result.addValidationInfo(published.validate(validationContext));
            }

            if (rights != null) {
                result.addValidationInfo(rights.validate(validationContext));
            }

            if (summary != null) {
                result.addValidationInfo(summary.validate(validationContext));
            }

            Iterator<Category> categoryIterator = categories.iterator();
            while (categoryIterator.hasNext()) {
                Category category = categoryIterator.next();
                result.addValidationInfo(category.validate(validationContext));
            }

        }

        return result;
    }

    /**
     * Get an iterator for the authors in the Entry.
     *
     * @return An iterator.
     */
    public Iterator<Author> getAuthors() {
        return authors.iterator();
    }

    /**
     * Add an author to the Entry.
     *
     * @param author The author to add.
     */
    public void addAuthors(Author author) {
        this.authors.add(author);
    }

    /**
     * Clear the list of authors.
     */
    public void clearAuthors() {
        this.authors.clear();
    }

    /**
     * Get an iterator for the categories in this Entry.
     *
     * @return An iterator.
     */
    public Iterator<String> getCategories() {
        ArrayList<String> items = new ArrayList<>();
        for (int i = 0; i < categories.size(); i++) {
            items.add(categories.get(i).getContent());
        }

        return items.iterator();
    }

    /**
     * Add a category.
     *
     * @param category the category to add.
     */
    public void addCategory(String category) {
        this.categories.add(new Category(category));
    }

    /**
     * Clear the list of categories.
     */
    public void clearCategories() {
        this.categories.clear();
    }

    /**
     * Get the content element for this Entry.
     *
     * @return The content element.
     */
    public Content getContent() {
        return content;
    }

    /**
     * Set the content element for this Entry.
     *
     * @param content content element to set
     */
    public void setContent(Content content) {
        this.content = content;
    }

    /**
     * Get the generator for this Entry.
     *
     * @return The generator element.
     */
    public Generator getGenerator() {
        return generator;
    }

    /**
     * Set the generator for this Entry.
     *
     * @param generator generator element to set
     */
    public void setGenerator(Generator generator) {
        this.generator = generator;
    }

    /**
     * Get a list of contributors.
     *
     * @return An iterator.
     */
    public Iterator<Contributor> getContributors() {
        return contributors.iterator();
    }

    /**
     * Add a contributor.
     *
     * @param contributor The contributor.
     */
    public void addContributor(Contributor contributor) {
        this.contributors.add(contributor);
    }

    /**
     * Clear the list of contributors.
     */
    public void clearContributors() {
        this.contributors.clear();
    }

    /**
     * Get the ID for this Entry.
     *
     * @return The ID.
     */
    public String getId() {
        if (id == null) {
            return null;
        }
        return id.getContent();
    }

    /**
     * Set the ID for this Entry.
     *
     * @param id The ID.
     */
    public void setId(String id) {
        this.id = new Id(id);
    }

    /**
     * Get the list of links for this Entry.
     *
     * @return An iterator.
     */
    public Iterator<Link> getLinks() {
        return links.iterator();
    }

    /**
     * Get the link for this Entry.
     *
     * @param link The link.
     */
    public void addLink(Link link) {
        this.links.add(link);
    }

    /**
     * Clear the list of links.
     */
    public void clearLinks() {
        this.links.clear();
    }

    /**
     * Get the published date, expressed as a String.
     *
     * @return The date.
     */
    public String getPublished() {
        if (published == null) {
            return null;
        }
        return published.getContent();
    }

    /**
     * Set the published date. The date should be in one of the
     * supported formats. This method will not check that the string
     * is in the correct format.
     *
     * @param published The string.
     */
    public void setPublished(String published) {
        this.published = new Published(published);
    }

    /**
     * Get the rights for this Entry.
     *
     * @return The rights.
     */
    public Rights getRights() {
        return rights;
    }

    /**
     * Set the rights for this Entry.
     *
     * @param rights The rights.
     */
    public void setRights(Rights rights) {
        this.rights = rights;
    }

    /**
     * Get the source for this Entry.
     *
     * @return The source.
     * @deprecated
     */
    @Deprecated
    public Source getSource() {
        return source;
    }

    /**
     * Set the source for this entry.
     *
     * @param source The source.
     * @deprecated
     */
    @Deprecated
    public void setSource(Source source) {
        this.source = source;
    }

    /**
     * Get the summary.
     *
     * @return The summary.
     */
    public Summary getSummary() {
        return summary;
    }

    /**
     * Set the summary.
     *
     * @param summary The summary.
     */
    public void setSummary(Summary summary) {
        this.summary = summary;
    }

    /**
     * Get the title.
     *
     * @return The title.
     */
    public Title getTitle() {
        return title;
    }

    /**
     * Set the title.
     *
     * @param title The title.
     */
    public void setTitle(Title title) {
        this.title = title;
    }

    /**
     * Get the updated date, expressed as a String. See
     * org.purl.sword.XmlElement.stringToDate for the
     * list of supported formats. This particular method
     * will not check if the date is formatted correctly.
     *
     * @return The date.
     */
    public String getUpdated() {
        if (updated == null) {
            return null;
        }
        return updated.getContent();
    }

    /**
     * Set the updated date. The date should match one of the
     * supported formats. This method will not check the format of the
     * string.
     *
     * @param updated The string.
     * @see Entry#setPublished(String) setPublished
     */
    public void setUpdated(String updated) {
        this.updated = new Updated(updated);
    }
}