package org.argeo.publishing.servlet;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLDecoder;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import javax.jcr.Node;
import javax.jcr.Repository;
import javax.jcr.RepositoryException;
import javax.jcr.Session;
import javax.jcr.nodetype.NodeType;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Templates;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.apache.commons.io.IOUtils;
import org.apache.xalan.processor.TransformerFactoryImpl;
import org.argeo.cms.servlet.ServletAuthUtils;
import org.argeo.cms.ui.CmsTheme;
import org.argeo.docbook.DbkType;
import org.argeo.docbook.DbkUtils;
import org.argeo.jcr.Jcr;
import org.argeo.jcr.JcrException;
import org.argeo.jcr.JcrUtils;
import org.w3c.dom.Document;

/**
 * A servlet transforming a dbk:* JCR node into HTML, using the DocBook XSL.
 */
public class DbkServlet extends HttpServlet {
	private static final long serialVersionUID = 6906020513498289335L;

	private Repository repository;

	private DocumentBuilderFactory documentBuilderFactory;
	private TransformerFactory transformerFactory;
	private Templates docBoookTemplates;

	private Map<String, CmsTheme> themes = Collections.synchronizedMap(new HashMap<>());

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

		String pathInfo = req.getPathInfo();
		if (pathInfo.startsWith("//"))
			pathInfo = pathInfo.substring(1);
		String path = URLDecoder.decode(pathInfo, StandardCharsets.UTF_8);

		if (path.toLowerCase().endsWith(".css")) {
			path = path.substring(1);
			int firstSlash = path.indexOf('/');
			String themeId = path.substring(0, firstSlash);
			String cssPath = path.substring(firstSlash);
			CmsTheme cmsTheme = themes.get(themeId);
			if (cmsTheme == null)
				throw new IllegalArgumentException("Theme " + themeId + " not found.");
			resp.setContentType("text/css");
			IOUtils.copy(cmsTheme.getResourceAsStream(cssPath), resp.getOutputStream());
			return;
		}

		Session session = null;
		try {
			session = ServletAuthUtils.doAs(() -> Jcr.login(repository, null), req);
			Node documentNode = session.getNode(path);
			Node node;
			if (documentNode.hasNode(DbkType.article.get()))
				node = documentNode.getNode(DbkType.article.get());
			else {
				throw new IllegalArgumentException("Unsupported node " + documentNode);
			}
			if (DbkUtils.isDbk(node)) {
				CmsTheme cmsTheme = null;
				String themeId = req.getParameter("themeId");
				if (themeId != null) {
					cmsTheme = themes.get(themeId);
					if (cmsTheme == null)
						throw new IllegalArgumentException("Theme " + themeId + " not found.");
				}

				// TODO customise DocBook so that it outputs UTF-8
				// see http://www.sagehill.net/docbookxsl/OutputEncoding.html
				resp.setContentType("text/html; charset=ISO-8859-1");

				// TODO optimise with pipes, SAX, etc. ?
				byte[] arr;
				try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
					session.exportDocumentView(node.getPath(), out, true, false);
					arr = out.toByteArray();
//				System.out.println(new String(arr, StandardCharsets.UTF_8));
				} catch (RepositoryException e) {
					throw new JcrException(e);
				}

				try (InputStream in = new ByteArrayInputStream(arr);
//					ByteArrayOutputStream out = new ByteArrayOutputStream();
				) {

					Result xmlOutput = new StreamResult(resp.getOutputStream());

					DocumentBuilder docBuilder = documentBuilderFactory.newDocumentBuilder();
//				Document doc = docBuilder.parse(new File(
//						System.getProperty("user.home") + "/dev/git/gpl/argeo-qa/doc/platform/argeo-platform.dbk.xml"));
					Document doc = docBuilder.parse(in);
					Source xmlInput = new DOMSource(doc);

					Transformer transformer = docBoookTemplates.newTransformer();

					// gather CSS
					if (cmsTheme != null) {
						StringBuilder sb = new StringBuilder();
						for (String cssPath : cmsTheme.getWebCssPaths()) {
							sb.append(req.getContextPath()).append(req.getServletPath()).append('/');
							sb.append(themeId).append('/').append(cssPath).append(' ');
						}
						sb.append("https://fonts.googleapis.com/css2?family=Roboto:wght@400;700&display=swap")
								.append(' ');
						sb.append(
								"https://fonts.googleapis.com/css2?family=Montserrat:ital,wght@0,300;0,400;0,600;1,400&display=swap")
								.append(' ');
						if (sb.length() > 0)
							transformer.setParameter("html.stylesheet", sb.toString());
					}
					transformer.transform(xmlInput, xmlOutput);
//				resp.getOutputStream().write(out.toByteArray());
				} catch (Exception e) {
					throw new ServletException("Cannot transform " + path, e);
				}
			} else if (node.isNodeType(NodeType.NT_FILE)) {// media download etc.
				String fileNameLowerCase = node.getName().toLowerCase();
				if (fileNameLowerCase.endsWith(".jpg") || fileNameLowerCase.endsWith(".jpeg")) {
					resp.setContentType("image/jpeg");
				} else if (fileNameLowerCase.endsWith(".png")) {
					resp.setContentType("image/png");
				} else if (fileNameLowerCase.endsWith(".gif")) {
					resp.setContentType("image/gif");
				} else if (fileNameLowerCase.endsWith(".svg")) {
					resp.setContentType("image/svg+xml");
				} else {
					// TODO know more content types...
					resp.setHeader("Content-Disposition", "attachment; filename=\"" + node.getName() + "\"");
				}
				IOUtils.copy(JcrUtils.getFileAsStream(node), resp.getOutputStream());
			} else {
				throw new IllegalArgumentException("Unsupported node " + node);
			}
		} catch (RepositoryException e1) {
			throw new JcrException(e1);
		} finally {
			Jcr.logout(session);
		}
	}

	@Override
	public void init() throws ServletException {

		// TODO improve configuration and provisioning of DocBook XSL
		String xslBase = System.getProperty("argeo.docbook.xsl");
		if (xslBase == null) {
			String defaultXslBase = "/opt/docbook-xsl";
			if (!Files.exists(Paths.get(defaultXslBase))) {
				throw new ServletException("System property argeo.docbook.xsl is not set and default location "
						+ defaultXslBase + " does not exist.");
			} else {
				xslBase = defaultXslBase;
			}
		}
		String xsl = xslBase + "/html/docbook.xsl";

		documentBuilderFactory = DocumentBuilderFactory.newInstance();
		documentBuilderFactory.setXIncludeAware(true);
		documentBuilderFactory.setNamespaceAware(true);

		// We must explicitly use the non-XSLTC transformer, as XSLTC is not working
		// with DocBook stylesheets
		transformerFactory = new TransformerFactoryImpl();

		Source xslSource = new StreamSource(xsl);
		try {
			docBoookTemplates = transformerFactory.newTemplates(xslSource);
			if (docBoookTemplates == null)
				throw new ServletException("Could not instantiate XSL " + xsl);
		} catch (TransformerConfigurationException e) {
			throw new ServletException("Cannot instantiate XSL " + xsl, e);
		}
	}

	public void setRepository(Repository repository) {
		this.repository = repository;
	}

	public void addTheme(CmsTheme theme, Map<String, String> properties) {
		themes.put(theme.getThemeId(), theme);
	}

	public void removeTheme(CmsTheme theme, Map<String, String> properties) {
		themes.remove(theme.getThemeId());
	}

}