[tmp/jakarta-migration.git] /

package org.collectionspace.services.common.vocabulary;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.collectionspace.services.client.PoxPayloadIn;
import org.collectionspace.services.client.PoxPayloadOut;
import org.collectionspace.services.common.context.ServiceContext;
import org.collectionspace.services.common.document.DocumentException;
import org.collectionspace.services.common.document.DocumentNotFoundException;
import org.collectionspace.services.common.repository.RepositoryClient;
import org.collectionspace.services.common.vocabulary.RefNameServiceUtils.AuthRefConfigInfo;
import org.collectionspace.services.config.service.ServiceBindingType;
import org.collectionspace.services.nuxeo.client.java.CoreSessionInterface;

import org.nuxeo.ecm.core.api.DocumentModel;
import org.nuxeo.ecm.core.api.DocumentModelList;
import org.nuxeo.ecm.core.api.impl.DocumentModelListImpl;

import com.google.common.collect.AbstractIterator;

/**
 * A DocumentModelList representing all of the documents that potentially reference an
 * authority item, found via full text search. This list must be post-processed to
 * eliminate false positives.
 *
 * Documents in this list are lazily fetched one page at a time, as they are accessed through
 * the list's Iterator, retrieved with the iterator() method. List items may not be accessed
 * through any other means, including the get() method, and the ListIterator retrieved
 * with listIterator(). Attempts to do so will result in unspecified behavior.
 * 
 */
public class LazyAuthorityRefDocList extends DocumentModelListImpl {
        private static final long serialVersionUID = 1L;
        
        private ServiceContext<PoxPayloadIn, PoxPayloadOut> ctx;
        private RepositoryClient<PoxPayloadIn, PoxPayloadOut> repoClient;
        private CoreSessionInterface repoSession;
        private List<String> serviceTypes;
        private String refName;
        private String refPropName;
        private Map<String, ServiceBindingType> queriedServiceBindings;
        private Map<String, List<AuthRefConfigInfo>> authRefFieldsByService;
        private String whereClauseAdditions;
        private String orderByClause;
        private int pageSize;
        
        private DocumentModelList firstPageDocList;
        
        /**
         * Creates a LazyAuthorityRefDocList. The method signature is modeled after
         * RefNameServiceUtils.findAuthorityRefDocs (the non-lazy way of doing this).
         * 
         * @param ctx
         * @param repoClient
         * @param repoSession
         * @param serviceTypes
         * @param refName
         * @param refPropName
         * @param queriedServiceBindings
         * @param authRefFieldsByService
         * @param whereClauseAdditions
         * @param orderByClause
         * @param pageSize                                              The number of documents to retrieve in each page
         * @param computeTotal
         * @throws DocumentException
         * @throws DocumentNotFoundException
         */
        public LazyAuthorityRefDocList(
                ServiceContext<PoxPayloadIn, PoxPayloadOut> ctx,
                RepositoryClient<PoxPayloadIn, PoxPayloadOut> repoClient,
                CoreSessionInterface repoSession, List<String> serviceTypes,
                String refName,
                String refPropName,
                Map<String, ServiceBindingType> queriedServiceBindings,
                Map<String, List<AuthRefConfigInfo>> authRefFieldsByService,
                String whereClauseAdditions,
                String orderByClause,
                int pageSize,
                boolean computeTotal) throws DocumentException, DocumentNotFoundException {

                this.ctx = ctx;
                this.repoClient = repoClient;
                this.repoSession = repoSession;
                this.serviceTypes = serviceTypes;
                this.refName = refName;
                this.refPropName = refPropName;
                this.queriedServiceBindings = queriedServiceBindings;
                this.authRefFieldsByService = authRefFieldsByService;
                this.whereClauseAdditions = whereClauseAdditions;
                this.orderByClause = orderByClause;
                this.pageSize = pageSize;

                // Fetch the first page immediately. This is necessary so that calls
                // to totalSize() will work immediately. The computeTotal flag is passed
                // into this initial page fetch. There's no need to compute totals
                // when fetching subsequent pages.
                
                firstPageDocList = fetchPage(0, computeTotal);
        }

        /**
         * Retrieves a page of authority references.
         * 
         * @param pageNum               The page number
         * @param computeTotal  
         * @return
         * @throws DocumentNotFoundException
         * @throws DocumentException
         */
        private DocumentModelList fetchPage(int pageNum, boolean computeTotal) throws DocumentNotFoundException, DocumentException {
                return RefNameServiceUtils.findAuthorityRefDocs(ctx, repoClient, repoSession,
                        serviceTypes, refName, refPropName, queriedServiceBindings, authRefFieldsByService,
                        whereClauseAdditions, orderByClause, pageSize, pageNum, computeTotal);
        }
                
        @Override
        public long totalSize() {
                // Return the totalSize from the first page of documents.
                return firstPageDocList.totalSize();
        }

        @Override
        public Iterator<DocumentModel> iterator() {
                // Create a new iterator that starts with the first page of documents.
                return new Itr(0, firstPageDocList);
        }
        
        /**
         * An iterator over a LazyAuthorityRefDocList. The iterator keeps one
         * page of documents in memory at a time, and traverses that page until
         * no items remain. A new page is fetched only when the current page is
         * exhausted.
         *
         */
        private class Itr extends AbstractIterator<DocumentModel> {
                private int currentPageNum = 0;
                private DocumentModelList currentPageDocList;
                private Iterator<DocumentModel> currentPageIterator;
                
                /**
                 * Creates a new iterator.
                 * 
                 * @param currentPageNum                The initial page number
                 * @param currentPageDocList    The documents in the initial page
                 */
                protected Itr(int pageNum, DocumentModelList pageDocList) {
                        setCurrentPage(pageNum, pageDocList);
                }

                /**
                 * Changes the current page.
                 * 
                 * @param pageNum               The new page number
                 * @param pageDocList   The documents in the new page
                 */
                private void setCurrentPage(int pageNum, DocumentModelList pageDocList) {
                        this.currentPageNum = pageNum;
                        this.currentPageDocList = pageDocList;
                        this.currentPageIterator = pageDocList.iterator();
                }
                
                @Override
                protected DocumentModel computeNext() {
                        // Find the next document to return, looking first in the current
                        // page. If the current page is exhausted, fetch the next page.
                        
                        if (currentPageIterator.hasNext()) {
                                // There is still an element to return from the current page.
                                return currentPageIterator.next();
                        }
                        
                        // The current page is exhausted.
                        
                        if (pageSize == 0 || (currentPageDocList.size() < pageSize)) { 
                                // There are no more pages.
                                return endOfData();
                        }
                        
                        // There may be more pages. Try to fetch the next one.
                        
                        int nextPageNum = currentPageNum + 1;
                        DocumentModelList nextPageDocList = null;
                        
                        try {
                                nextPageDocList = fetchPage(nextPageNum, false);
                        }
                        catch(DocumentException e) {}
                        
                        if (nextPageDocList == null || nextPageDocList.size() == 0) {
                                // There are no more pages.
                                return endOfData();
                        }

                        // There is another page. Make it the current page.
                        
                        setCurrentPage(nextPageNum, nextPageDocList);
                        
                        if (currentPageIterator.hasNext()) {
                                return currentPageIterator.next();
                        }

                        // Shouldn't get here.

                        return endOfData();
                }
        }
}