/*
 * Licensed to the Technische Universität Darmstadt under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The Technische Universität Darmstadt 
 * licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.
 *  
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.tudarmstadt.ukp.wikipedia.api;

import java.math.BigInteger;
import java.util.HashSet;
import java.util.Set;

import org.hibernate.LockMode;
import org.hibernate.Session;
import org.hibernate.type.LongType;
import org.hibernate.type.StringType;

import de.tudarmstadt.ukp.wikipedia.api.exception.WikiApiException;
import de.tudarmstadt.ukp.wikipedia.api.exception.WikiPageNotFoundException;
import de.tudarmstadt.ukp.wikipedia.api.exception.WikiTitleParsingException;
import de.tudarmstadt.ukp.wikipedia.api.hibernate.CategoryDAO;

public class Category implements WikiConstants {

    private CategoryDAO catDAO;
    private de.tudarmstadt.ukp.wikipedia.api.hibernate.Category hibernateCategory;
    private Wikipedia wiki;


    /**
     * Creates a category object.
     * @param wiki The wikipedia object.
     * @param id The hibernate id of the category.
     * @throws WikiPageNotFoundException If the category does not exist.
     */
    protected Category (Wikipedia wiki, long id) throws WikiPageNotFoundException {
        this.wiki = wiki;
        catDAO = new CategoryDAO(wiki);
        createCategory(id);
    }

    /**
     * Creates a category object.
     * @param wiki The wikipedia object.
     * @param pageID The pageID of the category.
     * @throws WikiPageNotFoundException If the category does not exist.
     */
    protected Category (Wikipedia wiki, int pageID) throws WikiPageNotFoundException {
        this.wiki = wiki;
        catDAO = new CategoryDAO(wiki);
        createCategory(pageID);
    }

    /**
     * Creates a category object.
     * @param wiki The wikipedia object.
     * @param pName The name of the category.
     * @throws WikiPageNotFoundException If the category does not exist.
     */
    public Category(Wikipedia wiki, String pName) throws WikiApiException {
        if (pName == null || pName.length() == 0) {
            throw new WikiPageNotFoundException();
        }
        this.wiki = wiki;
        catDAO = new CategoryDAO(wiki);
        Title catTitle = new Title(pName);
        createCategory(catTitle);
    }

    /**
     * @see de.tudarmstadt.ukp.wikipedia.api.Category#Category(Wikipedia, long)
     */
    private void createCategory(long id) throws WikiPageNotFoundException {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        hibernateCategory = catDAO.findById(id);
        session.getTransaction().commit();

        if (hibernateCategory == null) {
            throw new WikiPageNotFoundException("No category with id " + id + " was found.");
        }
    }

    /**
     * @see de.tudarmstadt.ukp.wikipedia.api.Category#Category(Wikipedia, int)
     */
    private void createCategory(int pageID) throws WikiPageNotFoundException {
        createCategory( wiki.__getCategoryHibernateId(pageID));
    }

    /**
     * @see de.tudarmstadt.ukp.wikipedia.api.Category#Category(Wikipedia, String)
     */
    private void createCategory(Title title) throws WikiPageNotFoundException {
        String name = title.getWikiStyleTitle();
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();

        Object returnValue;

        String query = "select cat.pageId from Category as cat where cat.name = :name";
        if(wiki.getDatabaseConfiguration().supportsCollation()) {
            query += Wikipedia.SQL_COLLATION;
        }
        returnValue = session.createNativeQuery(query)
                .setParameter("name", name, StringType.INSTANCE)
                .uniqueResult();
        session.getTransaction().commit();

        // if there is no category with this name, the hibernateCategory is null
        if (returnValue == null) {
            hibernateCategory = null;
            throw new WikiPageNotFoundException("No category with name " + name + " was found.");
        }
        else {
            // now cast it into an integer
            int pageID = (Integer) returnValue;
            createCategory( pageID);
        }
    }

    /**
     * This returns the internal id. Do not confuse this with the pageId.
     * @return Returns the internal id.
     */
    /*
     * Note well:
     * Access is limited to package-private here intentionally, as the database ID is considered framework-internal use.
     */
    long __getId() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        long id = hibernateCategory.getId();
        session.getTransaction().commit();
        return id;
    }

    /**
     * @return A unique page id.
     */
    public int getPageId() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        int pageID = hibernateCategory.getPageId();
        session.getTransaction().commit();
        return pageID;
    }

    /**
     * @return A set containing parents (supercategories) of this category.
     */
    public Set<Category> getParents() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        Set<Integer> tmpSet = new HashSet<Integer>(hibernateCategory.getInLinks());
        session.getTransaction().commit();

        Set<Category> categories = new HashSet<Category>();
        for (int pageID : tmpSet) {
            categories.add(this.wiki.getCategory(pageID));
        }
        return categories;
    }

    /**
     * This is a more efficient shortcut for writing "getParents().size()", as that would require to load all the parents first.
     * @return The number of parents of this category.
     */
    public int getNumberOfParents() {
        BigInteger nrOfInlinks = new BigInteger("0");

        long id = this.__getId();
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        Object returnValue = session.createNativeQuery("select count(inLinks) from category_inlinks where id = :id")
            .setParameter("id", id, LongType.INSTANCE)
            .uniqueResult();
        session.getTransaction().commit();

        if (returnValue != null) {
            nrOfInlinks = (BigInteger) returnValue;
        }
        return nrOfInlinks.intValue();
    }

    /**
     * @return A set containing the IDs of the parents of this category.
     */
    public Set<Integer> getParentIDs() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        Set<Integer> tmpSet = new HashSet<Integer>(hibernateCategory.getInLinks());
        session.getTransaction().commit();
        return tmpSet;
    }

    /**
     * @return A set containing the children (subcategories) of this category.
     */
    public Set<Category> getChildren() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        Set<Integer> tmpSet = new HashSet<Integer>(hibernateCategory.getOutLinks());
        session.getTransaction().commit();

        Set<Category> categories = new HashSet<Category>();
        for (int pageID : tmpSet) {
            categories.add(this.wiki.getCategory(pageID));
        }
        return categories;
    }

    /**
     * This is a more efficient shortcut for writing "getChildren().size()", as that would require to load all the children first.
     * @return The number of children of this category.
     */
    public int getNumberOfChildren() {
        BigInteger nrOfOutlinks = new BigInteger("0");

        long id = this.__getId();
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        Object returnValue = session.createNativeQuery("select count(outLinks) from category_outlinks where id = :id")
            .setParameter("id", id, LongType.INSTANCE)
            .uniqueResult();
        session.getTransaction().commit();

        if (returnValue != null) {
            nrOfOutlinks = (BigInteger) returnValue;
        }
        return nrOfOutlinks.intValue();
    }

    /**
     * @return A set containing the IDs of the children of this category.
     */
    public Set<Integer> getChildrenIDs() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        Set<Integer> tmpSet = new HashSet<Integer>(hibernateCategory.getOutLinks());
        session.getTransaction().commit();
        return tmpSet;
    }

    /**
     * @return The title of the category.
     * @throws WikiTitleParsingException
     */
    public Title getTitle() throws WikiTitleParsingException  {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        String name = hibernateCategory.getName();
        session.getTransaction().commit();
        Title title = new Title(name);
        return title;
    }

    /**
     * @return The set of articles that are categorized under this category.
     * @throws WikiApiException
     */
    public Set<Page> getArticles() throws WikiApiException {
        Set<Integer> tmpSet = getArticleIds();
        Set<Page> pages = new HashSet<Page>();
        for (int pageID : tmpSet) {
            pages.add(this.wiki.getPage(pageID));
        }
        return pages;
    }

    /**
     * @return The set of article ids that are categorized under this category.
     */
    public Set<Integer> getArticleIds() {
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        session.lock(hibernateCategory, LockMode.NONE);
        Set<Integer> tmpSet = new HashSet<Integer>(hibernateCategory.getPages());
        session.getTransaction().commit();

        return tmpSet;
    }

    /**
     * This is a more efficient shortcut for writing "getPages().size()", as that would require to load all the pages first.
     * @return The number of pages.
     */
    public int getNumberOfPages() {
        BigInteger nrOfPages = new BigInteger("0");

        long id = this.__getId();
        Session session = this.wiki.__getHibernateSession();
        session.beginTransaction();
        Object returnValue = session.createNativeQuery("select count(pages) from category_pages where id = :id")
            .setParameter("id", id, LongType.INSTANCE)
            .uniqueResult();
        session.getTransaction().commit();

        if (returnValue != null) {
            nrOfPages = (BigInteger) returnValue;
        }
        return nrOfPages.intValue();
    }

    /**
     * This method exposes implementation details and should not be made public.
     * It is used for performance tuning.
     * @return The set of pages that are categorized under this category.
     */
    /*
     * Note well:
     * Access is limited to package-private here intentionally, as it is API-internal use only.
     */
    Set<Integer> __getPages() {
        return getArticleIds();
    }

    /**
     * Returns *all* recursively collected descendants (=subcategories) of this category.
     * @return An iterable of all descendants (=subcategories) of this category.
     */
    public Iterable <Category> getDescendants() {
        return new CategoryDescendantsIterable(wiki, this);
    }

    /**
     * Returns *all* recursively collected descendants (=subcategories) of this category.
     * @return An iterable of all descendants (=subcategories) of this category.
     */
    protected Iterable <Category> getDescendants(int bufferSize) {
        return new CategoryDescendantsIterable(wiki, bufferSize, this);
    }

    /**
     * Returns the siblings of this category.
     * @return Returns the siblings of this category or null, if there are none.
     */
    public Set<Category> getSiblings() {
        Set<Category> siblings = new HashSet<Category>();

        // add siblings
        for (Category parent : this.getParents()) {
            siblings.addAll(parent.getChildren());
        }

        // remove this category from list
        siblings.remove(this);

        return siblings;
    }

    /**
     * @return A string with information about a {@link Category}.
     * @throws WikiApiException
     */
    protected String getCategoryInfo() throws WikiApiException {
        StringBuilder sb = new StringBuilder(1000);

        sb.append("ID             : ").append(__getId()).append(LF);
        sb.append("PageID         : ").append(getPageId()).append(LF);
        sb.append("Name           : ").append(getTitle()).append(LF);
        sb.append("In-Links").append(LF);
        for (Category parent : getParents()) {
            sb.append("  ").append(parent.getTitle()).append(LF);
        }
        sb.append("Out-Links").append(LF);
        for (Category child : getChildren()) {
            sb.append("  ").append(child.getTitle()).append(LF);
        }
        sb.append("Pages").append(LF);
        for (Page page : getArticles()) {
            sb.append("  ").append(page.getTitle()).append(LF);
        }
        return sb.toString();
    }

}