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Java API for embedding Dia-based diagrams in web pages in a Servlet environment.
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/*
 * semanticcms-dia-servlet - Java API for embedding Dia-based diagrams in web pages in a Servlet environment.
 * Copyright (C) 2013, 2014, 2015, 2016  AO Industries, Inc.
 *     [email protected]
 *     7262 Bull Pen Cir
 *     Mobile, AL 36695
 *
 * This file is part of semanticcms-dia-servlet.
 *
 * semanticcms-dia-servlet is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * semanticcms-dia-servlet is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with semanticcms-dia-servlet.  If not, see .
 */
package com.semanticcms.dia.servlet.impl;

import com.aoindustries.awt.image.ImageSizeCache;
import static com.aoindustries.encoding.TextInJavaScriptEncoder.encodeTextInJavaScript;
import static com.aoindustries.encoding.TextInXhtmlAttributeEncoder.encodeTextInXhtmlAttribute;
import static com.aoindustries.encoding.TextInXhtmlEncoder.encodeTextInXhtml;
import com.aoindustries.io.FileUtils;
import com.aoindustries.lang.ProcessResult;
import com.aoindustries.net.UrlUtils;
import com.aoindustries.servlet.http.LastModifiedServlet;
import com.aoindustries.util.Sequence;
import com.aoindustries.util.UnsynchronizedSequence;
import com.aoindustries.util.WrappedException;
import com.aoindustries.util.concurrent.ConcurrencyLimiter;
import com.semanticcms.core.model.PageRef;
import com.semanticcms.core.servlet.CaptureLevel;
import com.semanticcms.core.servlet.CountConcurrencyFilter;
import com.semanticcms.core.servlet.PageIndex;
import com.semanticcms.core.servlet.PageRefResolver;
import com.semanticcms.dia.model.Dia;
import com.semanticcms.dia.servlet.DiaExportServlet;
import java.awt.Dimension;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

final public class DiaImpl {

	private static final String LINUX_DIA_PATH = "/usr/bin/dia";

	private static final String WINDOWS_DIA_PATH = "C:\\Program Files (x86)\\Dia\\bin\\dia.exe";

	// This was used for opening the diagram, moved to semanticcms-openfile-servlet to avoid dependency.
	//private static final String WINDOWS_DIAW_PATH = "C:\\Program Files (x86)\\Dia\\bin\\diaw.exe";

	private static class TempDirLock {}
	private static final TempDirLock tempDirLock = new TempDirLock();
	private static final String TEMP_SUBDIR = DiaExport.class.getName();

	private static final String MISSING_IMAGE_PATH = "/semanticcms-dia-servlet/images/broken-chain-1164481-640x480.jpg";
	private static final int MISSING_IMAGE_WIDTH = 640;
	private static final int MISSING_IMAGE_HEIGHT = 480;

	public static final char SIZE_SEPARATOR = '-';
	public static final char EMPTY_SIZE = '_';
	public static final char DIMENSION_SEPARATOR = 'x';
	public static final String PNG_EXTENSION = ".png";

	/**
	 * The request key used to ensure per-request unique element IDs.
	 */
	private static final String ID_SEQUENCE_REQUEST_ATTRIBUTE_NAME = DiaImpl.class.getName() + ".idSequence";

	/**
	 * The alt link ID prefix.
	 */
	private static final String ALT_LINK_ID_PREFIX = "semanticcms-dia-servlet-alt-pixel-ratio-";

	/**
	 * The default width when neither width nor height provided.
	 */
	private static final int DEFAULT_WIDTH = 200;

	/**
	 * The supported pixel densities, these must be ordered from lowest to highest.  The first is the default.
	 */
	private static final int[] PIXEL_DENSITIES = {
		1,
		2,
		3,
		4
	};

	private static boolean isWindows() {
		String osName = System.getProperty("os.name");
		return osName!=null && osName.toLowerCase(Locale.ROOT).contains("windows");
	}

	private static String getDiaExportPath() {
		if(isWindows()) {
			return WINDOWS_DIA_PATH;
		} else {
			return LINUX_DIA_PATH;
		}
	}

	/* This was used for opening the diagram, moved to semanticcms-openfile-servlet to avoid dependency.
	public static String getDiaOpenPath() {
		if(isWindows()) {
			return WINDOWS_DIAW_PATH;
		} else {
			return LINUX_DIA_PATH;
		}
	}
	 */

	/**
	 * Make sure each diagram and scaling is only exported once when under concurrent access.
	 */
	private static final ConcurrencyLimiter exportConcurrencyLimiter = new ConcurrencyLimiter();

	public static DiaExport exportDiagram(
		PageRef pageRef,
		final Integer width,
		final Integer height,
		File tmpDir
	) throws InterruptedException, FileNotFoundException, IOException {
		final File diaFile = pageRef.getResourceFile(true, true);

		String diaPath = pageRef.getPath();
		// Strip extension if matches expected value
		if(diaPath.toLowerCase(Locale.ROOT).endsWith(Dia.DOT_EXTENSION)) {
			diaPath = diaPath.substring(0, diaPath.length() - Dia.DOT_EXTENSION.length());
		}
		// Generate the temp filename
		final File tmpFile;
		synchronized(tempDirLock) {
			tmpFile = new File(
				tmpDir,
				TEMP_SUBDIR
					+ pageRef.getBookPrefix().replace('/', File.separatorChar)
					+ diaPath.replace('/', File.separatorChar)
					+ "-"
					+ (width==null ? "_" : width.toString())
					+ "x"
					+ (height==null ? "_" : height.toString())
					+ ".png"
			);
			// Make temp directory if needed (and all parents)
			tmpDir = tmpFile.getParentFile();
			if(!tmpDir.exists()) FileUtils.mkdirs(tmpDir);
		}
		// Re-export when missing or timestamps indicate needs recreated
		try {
			exportConcurrencyLimiter.executeSerialized(
				tmpFile,
				new Callable() {
					@Override
					public Void call() throws IOException {
						if(!tmpFile.exists() || diaFile.lastModified() >= tmpFile.lastModified()) {
							// Determine size for scaling
							final String sizeParam;
							if(width==null) {
								if(height==null) {
									sizeParam = null;
								} else {
									sizeParam = "x" + height;
								}
							} else {
								if(height==null) {
									sizeParam = width + "x";
								} else {
									sizeParam = width + "x" + height;
								}
							}
							// Build the command
							final String diaExePath = getDiaExportPath();
							final String[] command;
							if(sizeParam == null) {
								command = new String[] {
									diaExePath,
									"--export=" + tmpFile.getCanonicalPath(),
									"--filter=png",
									"--log-to-stderr",
									diaFile.getCanonicalPath()
								};
							} else {
								command = new String[] {
									diaExePath,
									"--export=" + tmpFile.getCanonicalPath(),
									"--filter=png",
									"--size=" + sizeParam,
									"--log-to-stderr",
									diaFile.getCanonicalPath()
								};
							}
							// Export using dia
							ProcessResult result = ProcessResult.exec(command);
							int exitVal = result.getExitVal();
							if(exitVal != 0) throw new IOException(diaExePath + ": non-zero exit value: " + exitVal);
							if(!isWindows()) {
								// Dia does not set non-zero exit value, instead, it writes both errors and normal output to stderr
								// (Dia version 0.97.2, compiled 23:51:04 Apr 13 2012)
								String normalOutput = diaFile.getCanonicalPath() + " --> " + tmpFile.getCanonicalPath();
								// Read the standard error, if any one line matches the expected line, then it is OK
								// other lines include stuff like: Xlib:  extension "RANDR" missing on display ":0".
								boolean foundNormalOutput = false;
								String stderr = result.getStderr();
								BufferedReader errIn = new BufferedReader(new StringReader(stderr));
								try {
									String line;
									while((line = errIn.readLine())!=null) {
										if(line.equals(normalOutput)) {
											foundNormalOutput = true;
											break;
										}
									}
								} finally {
									errIn.close();
								}
								if(!foundNormalOutput) {
									throw new IOException(diaExePath + ": " + stderr);
								}
							}
						}
						return null;
					}
				}
			);
		} catch(ExecutionException e) {
			Throwable cause = e.getCause();
			if(cause instanceof IOException) throw (IOException)cause;
			if(cause instanceof RuntimeException) throw (RuntimeException)cause;
			throw new WrappedException(e);
		}
		// Get actual dimensions
		Dimension pngSize = ImageSizeCache.getImageSize(tmpFile);
		
		return new DiaExport(
			tmpFile,
			pngSize.width,
			pngSize.height
		);
	}

	private static String buildUrlPath(
		HttpServletRequest request,
		PageRef pageRef,
		int width,
		int height,
		int pixelDensity,
		DiaExport export
	) throws ServletException {
		String diaPath = pageRef.getPath();
		// Strip extension
		if(!diaPath.endsWith(Dia.DOT_EXTENSION)) throw new ServletException("Unexpected file extension for diagram: " + diaPath);
		diaPath = diaPath.substring(0, diaPath.length() - Dia.DOT_EXTENSION.length());
		StringBuilder urlPath = new StringBuilder();
		urlPath
			.append(request.getContextPath())
			.append(DiaExportServlet.SERVLET_PATH)
			.append(pageRef.getBookPrefix())
			.append(diaPath)
			.append(SIZE_SEPARATOR);
		if(width == 0) {
			urlPath.append(EMPTY_SIZE);
		} else {
			urlPath.append(width * pixelDensity);
		}
		urlPath.append(DIMENSION_SEPARATOR);
		if(height == 0) {
			urlPath.append(EMPTY_SIZE);
		} else {
			urlPath.append(height * pixelDensity);
		}
		urlPath.append(PNG_EXTENSION);
		// Check for header disabling auto last modified
		if(!"false".equalsIgnoreCase(request.getHeader(LastModifiedServlet.LAST_MODIFIED_HEADER_NAME))) {
			urlPath
				.append('?')
				.append(LastModifiedServlet.LAST_MODIFIED_PARAMETER_NAME)
				.append('=')
				.append(LastModifiedServlet.encodeLastModified(export.getTmpFile().lastModified()))
			;
		}
		return urlPath.toString();
	}

	public static void writeDiaImpl(
		ServletContext servletContext,
		HttpServletRequest request,
		HttpServletResponse response,
		Appendable out,
		Dia dia
	) throws ServletException, IOException {
		try {
			// Get the current capture state
			final CaptureLevel captureLevel = CaptureLevel.getCaptureLevel(request);
			if(captureLevel.compareTo(CaptureLevel.META) >= 0) {
				final PageRef pageRef = PageRefResolver.getPageRef(servletContext, request, dia.getBook(), dia.getPath());
				if(captureLevel == CaptureLevel.BODY) {
					final String responseEncoding = response.getCharacterEncoding();
					// Use default width when neither provided
					int width = dia.getWidth();
					int height = dia.getHeight();
					if(width==0 && height==0) width = DEFAULT_WIDTH;
					File resourceFile = pageRef.getResourceFile(false, true);
					// Scale concurrently for each pixel density
					List exports;
					if(resourceFile == null) {
						exports = null;
					} else {
						final File tempDir = (File)servletContext.getAttribute("javax.servlet.context.tempdir" /*ServletContext.TEMPDIR*/);
						final int finalWidth = width;
						final int finalHeight = height;
						List> tasks = new ArrayList>(PIXEL_DENSITIES.length);
						for(int i=0; i() {
									@Override
									public DiaExport call() throws InterruptedException, IOException {
										return exportDiagram(
											pageRef,
											finalWidth==0 ? null : (finalWidth * pixelDensity),
											finalHeight==0 ? null : (finalHeight * pixelDensity),
											tempDir
										);
									}
								}
							);
						}
						try {
							exports = CountConcurrencyFilter.getRecommendedExecutor(servletContext, request).callAll(tasks);
						} catch(ExecutionException e) {
							Throwable cause = e.getCause();
							if(cause instanceof RuntimeException) throw ((RuntimeException)cause);
							if(cause instanceof InterruptedException) throw ((InterruptedException)cause);
							if(cause instanceof IOException) throw ((IOException)cause);
							throw new WrappedException(e);
						}
					}
					// Get the thumbnail image in default pixel density
					DiaExport export = exports == null ? null : exports.get(0);
					// Find id sequence
					Sequence idSequence = (Sequence)request.getAttribute(ID_SEQUENCE_REQUEST_ATTRIBUTE_NAME);
					if(idSequence == null) {
						idSequence = new UnsynchronizedSequence();
						request.setAttribute(ID_SEQUENCE_REQUEST_ATTRIBUTE_NAME, idSequence);
					}
					// Write the img tag
					String refId = PageIndex.getRefIdInPage(servletContext, request, dia.getPage(), dia.getId());
					out.append("");

					if(export != null && PIXEL_DENSITIES.length > 1) {
						assert resourceFile != null;
						assert exports != null;
						// Write links to the exports for higher pixel densities
						long[] altLinkNums = new long[PIXEL_DENSITIES.length];
						for(int i=0; ix");
							encodeTextInXhtml(Integer.toString(pixelDensity), out);
							out.append("");
						}
						// Write script to hide alt links and select best based on device pixel ratio
						out.append("");
					}
				}
			}
		} catch(InterruptedException e) {
			// Restore the interrupted status
			Thread.currentThread().interrupt();
			throw new ServletException(e);
		}
	}

	/**
	 * Make no instances.
	 */
	private DiaImpl() {
	}
}