package org.gcube.common.metadataprofilediscovery;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import javax.xml.XMLConstants;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Source;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;

import org.gcube.common.metadataprofilediscovery.bean.MetadataProfile;
import org.gcube.common.metadataprofilediscovery.jaxb.MetadataFormat;
import org.gcube.common.metadataprofilediscovery.jaxb.NamespaceCategory;
import org.gcube.common.metadataprofilediscovery.reader.MetadataFormatDiscovery;
import org.gcube.common.metadataprofilediscovery.reader.MetadataFormatReader;
import org.gcube.common.metadataprofilediscovery.reader.NamespaceCategoryReader;
import org.gcube.common.scope.api.ScopeProvider;
import org.gcube.common.scope.impl.ScopeBean;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;


/**
 * The Class MetadataProfileReader.
 *
 * @author Francesco Mangiacrapa at ISTI-CNR (francesco.mangiacrapa@isti.cnr.it)
 * 
 * Sep 30, 2020
 */
public class MetadataProfileReader implements MetadataProfileDiscovery {

	public static final String URL_OF_GCDCMETADATAPROFILEV3_XSD = "https://wiki.gcube-system.org/images_gcube/e/e8/Gcdcmetadataprofilev3.xsd";

	private static String SCHEMA_FILENAME = "Gdcmetadataprofilev3.xsd";

	private MetadataFormatDiscovery medataFormatDiscovery;
	private ScopeBean scope;
	private Map<String, MetadataFormat> hashMetadataFormats = null;
	private List<NamespaceCategory> namespaceCategories = null;

	private String profileSchema = null;

	private String grMetadataProfileSecondaryType;

	private static Logger logger = LoggerFactory.getLogger(MetadataProfileReader.class);
	
	
	/**
	 * Instantiates a new metadata profile reader.
	 *
	 * @param grMetadataProfileSecondaryType the SecondaryType that must be used to discover the "gCube Metadata Profiles" from Information System
	 * @throws Exception the exception
	 */
	public MetadataProfileReader(String grMetadataProfileSecondaryType) throws Exception {
		
		if(grMetadataProfileSecondaryType==null || grMetadataProfileSecondaryType.isEmpty())
			throw new NullPointerException("Invalid input parameter");
		
		this.grMetadataProfileSecondaryType = grMetadataProfileSecondaryType;
		
		String scopeString = ScopeProvider.instance.get();
		logger.debug("Read scope " + scopeString + " from ScopeProvider");

		if (scopeString == null || scopeString.isEmpty())
			throw new Exception("Please set a valid scope into ScopeProvider");

		scope = new ScopeBean(scopeString);
		
		readNamespaces();
		readMetadataFormats();
	}
	
	/**
	 * Read metada formats.
	 *
	 * @throws Exception the exception
	 */
	private void readMetadataFormats() throws Exception {
		
		//reading from Generic Resource for Secondary Type passed in input
		medataFormatDiscovery = new MetadataFormatDiscovery(scope, grMetadataProfileSecondaryType);

		logger.info("MedataFormatDiscovery has retrieved: " + medataFormatDiscovery.getMetadataProfiles().size()
				+ " metadata type/s");
		logger.debug("filling cache for MedataFormat");
		hashMetadataFormats = new HashMap<String, MetadataFormat>(medataFormatDiscovery.getMetadataProfiles().size());
		for (MetadataProfile mT : medataFormatDiscovery.getMetadataProfiles()) {
			if (mT == null)
				continue;

			MetadataFormatReader reader = new MetadataFormatReader(scope, mT.getId());
			hashMetadataFormats.put(mT.getId(), reader.getMetadataFormat());
			logger.debug("MetadataType id: " + mT.getId() + " cached as: " + reader.getMetadataFormat());
		}
	
	}

	/**
	 * Read namespaces.
	 * @throws Exception 
	 */
	private void readNamespaces() throws Exception {

		try {
			if (namespaceCategories == null || namespaceCategories.isEmpty()) {

				if (namespaceCategories == null)
					namespaceCategories = new ArrayList<NamespaceCategory>();

				NamespaceCategoryReader rd = new NamespaceCategoryReader(scope);
				namespaceCategories.addAll(rd.getNamespaces().getNamespaceCategories());
			}
		} catch (Exception e) {
			logger.debug("An error occurred during read namespaces for categories: ", e);
			throw e;
		}
	}

	/**
	 * Gets the profile schema string.
	 *
	 * @return the profile schema string
	 */
	public static String getProfileSchemaString() {
		InputStream inputStream = MetadataProfileReader.getProfileSchemaInputStream();
		return new BufferedReader(new InputStreamReader(inputStream)).lines().collect(Collectors.joining("\n"));
	}

	/**
	 * Gets the profile schema input stream.
	 *
	 * @return the profile schema input stream
	 */
	public static InputStream getProfileSchemaInputStream() {
		try {
			logger.info("Trying to return the URL resource: "+URL_OF_GCDCMETADATAPROFILEV3_XSD);
			return new URL(URL_OF_GCDCMETADATAPROFILEV3_XSD).openStream();
			
		} catch (Exception e) {
			logger.warn("Error on reading the URL: "+URL_OF_GCDCMETADATAPROFILEV3_XSD);
		}
		logger.info("Returning local resource: "+SCHEMA_FILENAME);
		return MetadataProfileReader.class.getResourceAsStream(SCHEMA_FILENAME);
	}

	/**
	 * Gets the profile schema URL.
	 *
	 * @return the profile schema URL
	 */
	public static URL getProfileSchemaURL() {
		try {
			logger.info("Trying to return the URL object: "+URL_OF_GCDCMETADATAPROFILEV3_XSD);
			return new URL(URL_OF_GCDCMETADATAPROFILEV3_XSD);
			
		} catch (Exception e) {
			logger.warn("Error on reading the URL: "+URL_OF_GCDCMETADATAPROFILEV3_XSD);
		}
		logger.info("Returning local URL of: "+SCHEMA_FILENAME);
		return MetadataProfileReader.class.getResource(SCHEMA_FILENAME);
	}

	/**
	 * Validate against XSD.
	 *
	 * @param xml the xml
	 * @param xsd the xsd
	 * @throws SAXException the SAX exception
	 * @throws IOException  Signals that an I/O exception has occurred.
	 */
	static void validateAgainstXSD(Source xml, URL xsd) throws SAXException, IOException {
		SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
		Schema schema = factory.newSchema(xsd);
		Validator validator = schema.newValidator();
		validator.validate(xml);
	}

	/**
	 * Validate profile.
	 *
	 * @param xml the xml
	 * @throws Exception the exception
	 */
	public static void validateProfile(InputStream xml) throws Exception {
		validateAgainstXSD(new StreamSource(xml), getProfileSchemaURL());
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * getMetadataFormatForMetadataProfile(org.gcube.common.metadataprofilediscovery
	 * .bean.MetadataProfile)
	 */
	public MetadataFormat getMetadataFormatForMetadataProfile(MetadataProfile profile) throws Exception {

		if (profile == null)
			throw new Exception("Input " + MetadataProfile.class.getSimpleName() + " is null");

		MetadataFormat format = hashMetadataFormats.get(profile.getId());
		if (format != null)
			return format;

		MetadataFormatReader reader = new MetadataFormatReader(scope, profile.getId());
		return reader.getMetadataFormat();
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * getListOfMetadataProfiles()
	 */
	public List<MetadataProfile> getListOfMetadataProfiles() throws Exception {

		if (medataFormatDiscovery == null)
			readMetadataFormats();

		return medataFormatDiscovery.getMetadataProfiles();
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * getListOfNamespaceCategories()
	 */
	public List<NamespaceCategory> getListOfNamespaceCategories() throws Exception {

		if (namespaceCategories == null)
			readNamespaces();

		return namespaceCategories;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * resetMetadataProfile()
	 */
	public void resetMetadataProfile() {

		medataFormatDiscovery = null;
		hashMetadataFormats = null;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * resetNamespaceCategories()
	 */
	public void resetNamespaceCategories() {

		namespaceCategories = null;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * getProfileSchema()
	 */
	public String getProfileSchema() {
		if (profileSchema == null) {
			profileSchema = MetadataProfileReader.getProfileSchemaString();
		}
		return profileSchema;

	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.gcube.common.metadataprofilediscovery.DataCatalogueMetadataDiscovery#
	 * validateProfile(java.lang.String)
	 */
	public void validateProfile(String xmlProfile) throws ParserConfigurationException, SAXException, IOException {
		DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
		Document doc = db.parse(new InputSource(new StringReader(xmlProfile)));
		DOMSource source = new DOMSource(doc);
		validateAgainstXSD(source, getProfileSchemaURL());
	}
	
	/**
	 * Utility method to get a metadata format from a "gCube Metadata Profiles" model (XML-based)
	 *
	 * @param metadataProfileStream the metadata profile stream
	 * @return the metadata format
	 * @throws JAXBException the JAXB exception
	 */
	public static MetadataFormat toMetadataFormat(InputStream metadataProfileStream) throws JAXBException{
		
		if(metadataProfileStream==null)
			throw new NullPointerException("Invalid input parameter");
		
		JAXBContext jaxbContext = JAXBContext.newInstance(MetadataFormat.class);
	    Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
	    return (MetadataFormat) jaxbUnmarshaller.unmarshal(metadataProfileStream);
	}


}