/*
 * Copyright Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags and
 * the COPYRIGHT.txt file distributed with this work.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * 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 org.teiid.translator.odata4;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.olingo.client.api.data.ResWrap;
import org.apache.olingo.client.api.serialization.ODataDeserializerException;
import org.apache.olingo.client.core.serialization.JsonDeserializer;
import org.apache.olingo.commons.api.data.ComplexValue;
import org.apache.olingo.commons.api.data.Entity;
import org.apache.olingo.commons.api.data.EntityCollection;
import org.apache.olingo.commons.api.data.Property;
import org.teiid.translator.TranslatorException;
import org.teiid.translator.document.DocumentNode;
import org.teiid.translator.odata4.ODataMetadataProcessor.ODataType;
import org.teiid.translator.odata4.deserializer.JsonEntitySetDeserializer;


public abstract class ODataResponse {
	private URI nextUri;
	private Iterator<ODataDocument> results;
	private ODataType resultsType;
	private List<Map<String, Object>> currentDocumentRows;
	private DocumentNode rootNode;

	public ODataResponse(InputStream payload, ODataType type, DocumentNode rootNode) throws TranslatorException {
		this.resultsType = type;
		this.rootNode = rootNode;
		this.results = parsePayload(payload);
	}

	private Iterator<ODataDocument> parsePayload(InputStream payload) throws TranslatorException {
		try {
			JsonDeserializer parser = new JsonDeserializer(false);
			if (this.resultsType == ODataType.ENTITY) {
				Entity entity = parser.toEntity(payload).getPayload();
				ODataDocument document = ODataDocument.createDocument(entity);
				return Arrays.asList(document).iterator();
			} else if (this.resultsType == ODataType.ENTITY_COLLECTION) {
				try {
					JsonParser jsonParser = new JsonFactory(new ObjectMapper()).createParser(payload);
					ResWrap<EntityCollection> resWrap = new JsonEntitySetDeserializer(false).doDeserialize(jsonParser);
					EntityCollection entityCollection = resWrap.getPayload();
					this.nextUri = entityCollection.getNext();
					ArrayList<ODataDocument> documents = new ArrayList<ODataDocument>();
					for (Entity entity : entityCollection.getEntities()) {
						documents.add(ODataDocument.createDocument(entity));
					}
					return documents.iterator();
				} catch (IOException e) {
					throw new TranslatorException(e);
				}
			} else {
				// complex
				Property property = parser.toProperty(payload).getPayload();
				if (property.isCollection()) {
					ArrayList<ODataDocument> documents = new ArrayList<ODataDocument>();
					for (Object obj : property.asCollection()) {
						ComplexValue complexValue = (ComplexValue) obj;
						documents.add(ODataDocument.createDocument(complexValue));
					}
					return documents.iterator();
				} else {
					ODataDocument document = ODataDocument.createDocument(property.asComplex());
					return Arrays.asList(document).iterator();
				}
			}
		} catch (ODataDeserializerException e) {
			throw new TranslatorException(e);
		}
	}

	public Map<String, Object> getNext() throws TranslatorException {

		if (this.currentDocumentRows != null && !this.currentDocumentRows.isEmpty()) {
			return this.currentDocumentRows.remove(0);
		}

		if (this.results.hasNext()) {
			this.currentDocumentRows = this.rootNode.tuples(this.results.next());
			return getNext();
		} else {
			if (this.nextUri != null) {
				this.results = fetchSkipToken(this.nextUri);
				return getNext();
			}
		}
		return null;
	}

	private Iterator<ODataDocument> fetchSkipToken(URI uri) throws TranslatorException {
		return parsePayload(nextBatch(uri));
	}

	public abstract InputStream nextBatch(URI uri) throws TranslatorException;
}

