From 80f7cc110da0e55de396a905a05e7a39d09bf57f Mon Sep 17 00:00:00 2001
From: Guillaume Grossetie <ggrossetie@gmail.com>
Date: Wed, 4 Aug 2021 08:37:56 +0200
Subject: [PATCH] resolves #842 creates SVG and PNG error images

Use svgSalamander to create SVG and PNG images.
Batik adds ~7mb of dependencies.
---
 pom.xml                                       |  2 +-
 server/pom.xml                                | 18 ++--
 .../io/kroki/server/error/ErrorHandler.java   | 63 +++++++++---
 .../io/kroki/server/error/ErrorImage.java     | 99 +++++++++++++++++++
 .../java/io/kroki/server/ErrorImageTest.java  | 24 +++++
 .../kroki/server/error/ErrorHandlerTest.java  | 46 ++++++++-
 6 files changed, 225 insertions(+), 27 deletions(-)
 create mode 100644 server/src/main/java/io/kroki/server/error/ErrorImage.java
 create mode 100644 server/src/test/java/io/kroki/server/ErrorImageTest.java

diff --git a/pom.xml b/pom.xml
index 89b2f7884..e30885987 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,6 +3,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>io.kroki</groupId>
   <artifactId>kroki</artifactId>
+  <name>kroki</name>
   <packaging>pom</packaging>
   <version>0.14.0</version>
   <properties>
@@ -29,5 +30,4 @@
       </plugin>
     </plugins>
   </build>
-  <name>kroki</name>
 </project>
diff --git a/server/pom.xml b/server/pom.xml
index a438ba4e1..57b5ce8eb 100644
--- a/server/pom.xml
+++ b/server/pom.xml
@@ -80,6 +80,11 @@
       <artifactId>plantuml</artifactId>
       <version>${plantuml.version}</version>
     </dependency>
+    <dependency>
+      <groupId>guru.nidi.com.kitfox</groupId>
+      <artifactId>svgSalamander</artifactId>
+      <version>1.1.3</version>
+    </dependency>
     <dependency>
       <groupId>org.junit.jupiter</groupId>
       <artifactId>junit-jupiter-api</artifactId>
@@ -108,6 +113,7 @@
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
       <version>${mockito-core.version}</version>
+      <scope>test</scope>
     </dependency>
     <!--
     Due to a bug in JDK 8 we need to add vertx-codegen as a test dependency otherwise the following exception is thrown:
@@ -133,18 +139,6 @@
       <version>${vertx.version}</version>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>org.apache.xmlgraphics</groupId>
-      <artifactId>batik-transcoder</artifactId>
-      <version>1.14</version>
-      <scope>test</scope>
-    </dependency>
-    <dependency>
-      <groupId>com.twelvemonkeys.imageio</groupId>
-      <artifactId>imageio-batik</artifactId>
-      <version>3.7.0</version>
-      <scope>test</scope>
-    </dependency>
   </dependencies>
   <build>
     <resources>
diff --git a/server/src/main/java/io/kroki/server/error/ErrorHandler.java b/server/src/main/java/io/kroki/server/error/ErrorHandler.java
index 5b4cfca7c..ef69abbc3 100644
--- a/server/src/main/java/io/kroki/server/error/ErrorHandler.java
+++ b/server/src/main/java/io/kroki/server/error/ErrorHandler.java
@@ -1,17 +1,23 @@
 package io.kroki.server.error;
 
+import com.kitfox.svg.SVGException;
 import io.kroki.server.log.Logging;
 import io.vertx.core.Vertx;
+import io.vertx.core.buffer.Buffer;
 import io.vertx.core.http.HttpHeaders;
 import io.vertx.core.http.HttpServerResponse;
 import io.vertx.core.json.JsonArray;
 import io.vertx.core.json.JsonObject;
 import io.vertx.ext.web.MIMEHeader;
 import io.vertx.ext.web.RoutingContext;
-import io.vertx.ext.web.impl.Utils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import javax.imageio.ImageIO;
+import java.awt.image.BufferedImage;
+import java.awt.image.DataBufferByte;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import java.util.List;
 
 public class ErrorHandler implements io.vertx.ext.web.handler.ErrorHandler {
@@ -143,28 +149,59 @@ private boolean sendError(RoutingContext context, String mime, int errorCode, St
         }
         jsonError.put("stack", stack);
       }
-
       response.putHeader(HttpHeaders.CONTENT_TYPE, "application/json");
       response.end(jsonError.encode());
       return true;
     }
 
     if (mime.startsWith("text/plain")) {
+      String completeErrorMessage = getCompleteErrorMessage(context, errorCode, errorMessage);
       response.putHeader(HttpHeaders.CONTENT_TYPE, "text/plain");
-      StringBuilder sb = new StringBuilder();
-      sb.append("Error ");
-      sb.append(errorCode);
-      sb.append(": ");
-      sb.append(errorMessage);
-      if (context.failure() != null && displayExceptionDetails) {
-        for (StackTraceElement elem : context.failure().getStackTrace()) {
-          sb.append("\tat ").append(elem).append("\n");
-        }
-      }
-      response.end(sb.toString());
+      response.end(completeErrorMessage);
       return true;
     }
 
+    if (mime.startsWith("image/svg+xml")) {
+      String completeErrorMessage = getCompleteErrorMessage(context, errorCode, errorMessage);
+      try {
+        String svgImage = ErrorImage.buildSVGImage(completeErrorMessage).getSource();
+        response.putHeader(HttpHeaders.CONTENT_TYPE, "image/svg+xml");
+        response.end(svgImage);
+        return true;
+      } catch (IOException | SVGException e) {
+        logger.warn("Unable to generate error image", e);
+        return false;
+      }
+    }
+
+    if (mime.startsWith("image/png") || mime.startsWith("image/*")) {
+      String completeErrorMessage = getCompleteErrorMessage(context, errorCode, errorMessage);
+      try ( ByteArrayOutputStream output = new ByteArrayOutputStream()) {
+        BufferedImage bufferedImage = ErrorImage.buildPNGImage(completeErrorMessage);
+        ImageIO.write(bufferedImage, "png", output);
+        response.putHeader(HttpHeaders.CONTENT_TYPE, "image/png");
+        response.end(Buffer.buffer(output.toByteArray()));
+        return true;
+      } catch (IOException | SVGException e) {
+        logger.warn("Unable to generate error image", e);
+        return false;
+      }
+    }
+
     return false;
   }
+
+  private String getCompleteErrorMessage(RoutingContext context, int errorCode, String errorMessage) {
+    StringBuilder sb = new StringBuilder();
+    sb.append("Error ");
+    sb.append(errorCode);
+    sb.append(": ");
+    sb.append(errorMessage);
+    if (context.failure() != null && displayExceptionDetails) {
+      for (StackTraceElement elem : context.failure().getStackTrace()) {
+        sb.append("\tat ").append(elem).append("\n");
+      }
+    }
+    return sb.toString();
+  }
 }
diff --git a/server/src/main/java/io/kroki/server/error/ErrorImage.java b/server/src/main/java/io/kroki/server/error/ErrorImage.java
new file mode 100644
index 000000000..22a411d84
--- /dev/null
+++ b/server/src/main/java/io/kroki/server/error/ErrorImage.java
@@ -0,0 +1,99 @@
+package io.kroki.server.error;
+
+import com.kitfox.svg.SVGDiagram;
+import com.kitfox.svg.SVGElement;
+import com.kitfox.svg.SVGException;
+import com.kitfox.svg.SVGUniverse;
+import com.kitfox.svg.app.beans.SVGIcon;
+
+import java.awt.Dimension;
+import java.awt.Graphics2D;
+import java.awt.geom.Rectangle2D;
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+
+public class ErrorImage {
+
+  public static SVGWithDimension buildSVGImage(String errorMessage) throws IOException, SVGException {
+    String[] lines = errorMessage.split("\\n");
+    StringBuilder text = new StringBuilder();
+    for (String line : lines) {
+      // QUESTION: should we use ellipsis or force break if line length is too long?
+      text.append("<tspan x=\"10\" dy=\"14\">").append(line).append("</tspan>\n");
+    }
+    String svg = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n" +
+      "<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\">\n" +
+      "<rect fill=\"#fff5f7\" width=\"100%\" height=\"100%\"/>\n" +
+      "<text id=\"text\" xml:space=\"preserve\" font-weight=\"bold\" fill=\"#cd0930\" font-family=\"Roboto\" font-size=\"16px\" x=\"0\" y=\"5\" dy=\"0\">\n" +
+      text +
+      "</text>\n" +
+      "<rect fill=\"#ff3860\" width=\"3\" height=\"100%\"/>\n" +
+      "</svg>";
+    Dimension dimension = computeDimension(svg);
+    String result = svg
+      .replaceAll("<svg xmlns=.*>\\n", "<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"" + dimension.width + "\" height=\"" + dimension.height + "\" viewBox=\"0 0 " + dimension.width + " " + dimension.height + "\" version=\"1.1\">\n")
+      .replaceAll("width=\"100%\"", "width=\"" + dimension.width + "\"")
+      .replaceAll("height=\"100%\"", "height=\"" + dimension.height + "\"");
+    return new SVGWithDimension(result, dimension);
+  }
+
+  public static BufferedImage buildPNGImage(String errorMessage) throws IOException, SVGException {
+    SVGWithDimension svgWithDimension = buildSVGImage(errorMessage);
+    try (ByteArrayInputStream svgInputStream = new ByteArrayInputStream(svgWithDimension.source.getBytes(StandardCharsets.UTF_8))) {
+      SVGUniverse svgUniverse = new SVGUniverse();
+      URI svgUri = svgUniverse.loadSVG(svgInputStream, "error-message");
+      SVGDiagram diagram = svgUniverse.getDiagram(svgUri);
+      SVGIcon svgIcon = new SVGIcon();
+      svgIcon.setSvgUniverse(svgUniverse);
+      svgIcon.setSvgURI(svgUri);
+      svgIcon.setAntiAlias(true);
+      // svgIcon.setInterpolation(SVGIcon.INTERP_NEAREST_NEIGHBOR);
+      // svgIcon.setInterpolation(SVGIcon.INTERP_BILINEAR);
+      svgIcon.setInterpolation(SVGIcon.INTERP_BICUBIC);
+      int width = (int) diagram.getWidth();
+      int height = (int) diagram.getHeight();
+      BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
+      Graphics2D g = image.createGraphics();
+      g.setClip(0, 0, width, height);
+      svgIcon.paintIcon(null, g, 0, 0);
+      g.dispose();
+      return image;
+      // ImageIO.write(image, "png", resultOutputStream);
+      // SVGCache.getSVGUniverse().clear();
+      // resultOutputStream.flush();
+      // return image;
+    }
+  }
+
+  private static Dimension computeDimension(String svg) throws IOException, SVGException {
+    try (ByteArrayInputStream svgInputStream = new ByteArrayInputStream(svg.getBytes(StandardCharsets.UTF_8))) {
+      SVGUniverse svgUniverse = new SVGUniverse();
+      URI svgUri = svgUniverse.loadSVG(svgInputStream, "error-message");
+      SVGDiagram diagram = svgUniverse.getDiagram(svgUri);
+      SVGElement textElement = diagram.getElement("text");
+      Rectangle2D bbox = textElement.getRoot().getBoundingBox();
+      return new Dimension((int) Math.floor(bbox.getWidth() + bbox.getX()) + 10, (int) Math.floor(bbox.getHeight() + bbox.getY()) + 5);
+    }
+  }
+
+  public static class SVGWithDimension {
+    private final String source;
+    private final Dimension dimension;
+
+    public SVGWithDimension(String source, Dimension dimension) {
+      this.source = source;
+      this.dimension = dimension;
+    }
+
+    public String getSource() {
+      return source;
+    }
+
+    public Dimension getDimension() {
+      return dimension;
+    }
+  }
+}
diff --git a/server/src/test/java/io/kroki/server/ErrorImageTest.java b/server/src/test/java/io/kroki/server/ErrorImageTest.java
new file mode 100644
index 000000000..129332f4e
--- /dev/null
+++ b/server/src/test/java/io/kroki/server/ErrorImageTest.java
@@ -0,0 +1,24 @@
+package io.kroki.server;
+
+import com.kitfox.svg.SVGException;
+import io.kroki.server.error.ErrorImage;
+import org.junit.jupiter.api.Test;
+
+import java.awt.Dimension;
+import java.io.IOException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ErrorImageTest {
+
+  @Test
+  public void should_generate_svg_error_image() throws IOException, SVGException {
+    ErrorImage.SVGWithDimension svgWithDimension = ErrorImage.buildSVGImage("There is no layout engine support for \"nfds\"\nUse one of: circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi");
+    Dimension dimension = svgWithDimension.getDimension();
+    assertThat(dimension.width).isGreaterThan(500);
+    assertThat(dimension.height).isGreaterThan(40);
+    assertThat(svgWithDimension.getSource()).contains("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n");
+    assertThat(svgWithDimension.getSource()).contains("<tspan x=\"10\" dy=\"14\">There is no layout engine support for \"nfds\"</tspan>\n");
+    assertThat(svgWithDimension.getSource()).contains("<tspan x=\"10\" dy=\"14\">Use one of: circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi</tspan>\n");
+  }
+}
diff --git a/server/src/test/java/io/kroki/server/error/ErrorHandlerTest.java b/server/src/test/java/io/kroki/server/error/ErrorHandlerTest.java
index 4e9c6cbeb..be30841b4 100644
--- a/server/src/test/java/io/kroki/server/error/ErrorHandlerTest.java
+++ b/server/src/test/java/io/kroki/server/error/ErrorHandlerTest.java
@@ -7,13 +7,20 @@
 import io.vertx.core.http.HttpServerRequest;
 import io.vertx.core.http.HttpServerResponse;
 import io.vertx.core.http.impl.headers.HeadersMultiMap;
+import io.vertx.core.json.JsonObject;
 import io.vertx.ext.web.RoutingContext;
+import io.vertx.ext.web.impl.ParsableHeaderValuesContainer;
+import io.vertx.ext.web.impl.ParsableMIMEValue;
 import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentMatcher;
 import org.mockito.Mockito;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
+import static org.mockito.ArgumentMatchers.argThat;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -105,9 +112,46 @@ void should_return_service_unavailable_error_json() {
     Mockito.verify(httpServerResponse).end("{\"error\":{\"code\":503,\"message\":\"Mermaid service is unavailable!\"}}");
   }
 
-  private HttpServerResponse jsonServerResponse() {
+  @Test
+  void should_return_svg_error_image() {
+    Vertx vertx = Vertx.vertx();
+    RoutingContext routingContext = mock(RoutingContext.class);
+    HttpServerResponse httpServerResponse = plainResponse();
+    HttpServerRequest httpServerRequest = mock(HttpServerRequest.class);
+
+    when(httpServerResponse.getStatusMessage()).thenReturn(null);
+    when(routingContext.parsedHeaders()).thenReturn(new ParsableHeaderValuesContainer(
+      Collections.singletonList(new ParsableMIMEValue("image/svg+xml")),
+      new ArrayList<>(),
+      new ArrayList<>(),
+      new ArrayList<>(),
+      new ParsableMIMEValue("*/*")
+    ));
+    when(routingContext.response()).thenReturn(httpServerResponse);
+    when(routingContext.request()).thenReturn(httpServerRequest);
+    when(routingContext.failure()).thenReturn(new BadRequestException("Syntax Error? (line: 1)"));
+    when(httpServerRequest.method()).thenReturn(HttpMethod.GET);
+    ErrorHandler errorHandler = new ErrorHandler(vertx, false);
+
+    errorHandler.handle(routingContext);
+
+    Mockito.verify(httpServerResponse).setStatusMessage("Bad Request");
+    Mockito.verify(httpServerResponse).setStatusCode(400);
+    Mockito.verify(httpServerResponse).end(argThat((ArgumentMatcher<String>) argument ->
+      argument.contains("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n") &&
+        argument.contains("<tspan x=\"10\" dy=\"14\">Error 400: Syntax Error? (line: 1)</tspan>\n")
+    ));
+  }
+
+  private HttpServerResponse plainResponse() {
     HttpServerResponse httpServerResponse = mock(HttpServerResponse.class);
+    MultiMap headers = new HeadersMultiMap();
+    when(httpServerResponse.headers()).thenReturn(headers);
+    return httpServerResponse;
+  }
 
+  private HttpServerResponse jsonServerResponse() {
+    HttpServerResponse httpServerResponse = mock(HttpServerResponse.class);
     MultiMap headers = new HeadersMultiMap();
     headers.add(HttpHeaders.CONTENT_TYPE, "application/json");
     when(httpServerResponse.headers()).thenReturn(headers);