Auto-format plugin HTTP pages from known formats

If we detect the requested plugin resource does not exist, but a
file with a .md extension instead does exist, open the .md file and
reformat as html. Do that reformatting using the pegdown library.

Change-Id: I29e1b1c58607a9faf2acfdc387a7418b545c5b48

Documentation/licenses.txt

@@ -52,6 +52,7 @@ Included Components
 |JSR 305                    | <<jsr305,New-Style BSD>>
 |dk.brics.automaton         | <<automaton,New-Style BSD>>
 |Java Concurrency in Practice Annotations | <<jcip,Create Commons Attribution License>>
+|pegdown                    | <<apache2,Apache License 2.0>>
 |======================================================================
 
 Cryptography Notice

gerrit-httpd/src/main/java/com/google/gerrit/httpd/plugins/HttpPluginServlet.java

@@ -18,6 +18,7 @@ import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
+import com.google.gerrit.server.documentation.MarkdownFormatter;
 import com.google.gerrit.server.MimeUtilFileTypeRegistry;
 import com.google.gerrit.server.plugins.Plugin;
 import com.google.gerrit.server.plugins.ReloadPluginListener;
@@ -173,8 +174,15 @@ class HttpPluginServlet extends HttpServlet
     if (file.startsWith("Documentation/") || file.startsWith("static/")) {
       JarFile jar = holder.plugin.getJarFile();
       JarEntry entry = jar.getJarEntry(file);
-      if (entry != null && entry.getSize() > 0) {
+      if (file.startsWith("Documentation/") && !isValidEntry(entry)) {
-        sendResource(jar, entry, res);
+        entry = getRealFileEntry(jar, file);
+        if (isValidEntry(entry)) {
+          sendResource(jar, entry, res, holder.plugin.getName(), true);
+          return;
+        }
+      }
+      if (isValidEntry(entry)) {
+        sendResource(jar, entry, res, holder.plugin.getName());
         return;
       }
     }
@@ -183,8 +191,24 @@ class HttpPluginServlet extends HttpServlet
     res.sendError(HttpServletResponse.SC_NOT_FOUND);
   }
 
-  private void sendResource(JarFile jar, JarEntry entry, HttpServletResponse res)
+  private JarEntry getRealFileEntry(JarFile jar, String file) {
+    // TODO: Replace with a loop iterating over possible formatters
+    return jar.getJarEntry(file.replaceAll("\\.html$", ".md"));
+  }
+
+  private boolean isValidEntry(JarEntry entry) {
+    return entry != null && entry.getSize() > 0;
+  }
+
+  private void sendResource(JarFile jar, JarEntry entry,
+      HttpServletResponse res, String pluginName) throws IOException {
+    sendResource(jar, entry, res, pluginName, false);
+  }
+
+  private void sendResource(JarFile jar, JarEntry entry,
+      HttpServletResponse res, String pluginName, boolean format)
       throws IOException {
+    String entryName = entry.getName();
     byte[] data = null;
     if (entry.getSize() <= 128 * 1024) {
       data = new byte[(int) entry.getSize()];
@@ -194,24 +218,44 @@ class HttpPluginServlet extends HttpServlet
       } finally {
         in.close();
       }
+    } else if (format == true) {
+      log.warn(String.format("Plugin '%s' file '%s' too large to format",
+          pluginName, entryName));
     }
 
     String contentType = null;
+    String charEnc = null;
     Attributes atts = entry.getAttributes();
     if (atts != null) {
       contentType = Strings.emptyToNull(atts.getValue("Content-Type"));
+      charEnc = Strings.emptyToNull(atts.getValue("Character-Encoding"));
     }
+
     if (contentType == null) {
-      MimeType type = mimeUtil.getMimeType(entry.getName(), data);
+      MimeType type = mimeUtil.getMimeType(entryName, data);
       contentType = type.toString();
     }
 
+    if (format && data != null) {
+      if (charEnc == null) {
+        charEnc = "UTF-8";
+      }
+      MarkdownFormatter fmter = new MarkdownFormatter();
+      data = fmter.getHtmlFromMarkdown(data, charEnc);
+      res.setHeader("Content-Length", Long.toString(data.length));
+      contentType = "text/html";
+    } else {
+      res.setHeader("Content-Length", Long.toString(entry.getSize()));
+    }
+
     long time = entry.getTime();
     if (0 < time) {
       res.setDateHeader("Last-Modified", time);
     }
     res.setContentType(contentType);
-    res.setHeader("Content-Length", Long.toString(entry.getSize()));
+    if (charEnc != null) {
+      res.setCharacterEncoding(charEnc);
+    }
     if (data != null) {
       res.getOutputStream().write(data);
     } else {

gerrit-server/pom.xml

@@ -170,6 +170,11 @@ limitations under the License.
       <groupId>com.googlecode.prolog-cafe</groupId>
       <artifactId>PrologCafe</artifactId>
     </dependency>
+
+    <dependency>
+      <groupId>org.pegdown</groupId>
+      <artifactId>pegdown</artifactId>
+    </dependency>
   </dependencies>
 
   <build>

gerrit-server/src/main/java/com/google/gerrit/server/documentation/MarkdownFormatter.java

@@ -0,0 +1,35 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.documentation;
+
+import static org.pegdown.Extensions.ALL;
+
+import org.eclipse.jgit.util.RawParseUtils;
+import org.pegdown.PegDownProcessor;
+
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
+
+public class MarkdownFormatter {
+
+  public byte[] getHtmlFromMarkdown(byte[] data, String charEnc)
+      throws UnsupportedEncodingException {
+    String decodedData = RawParseUtils.decode(Charset.forName(charEnc), data);
+    String formatted = new PegDownProcessor(ALL).markdownToHtml(decodedData);
+    data = formatted.getBytes(charEnc);
+    return data;
+  }
+  // TODO: Add a cache
+}

pom.xml

@@ -822,6 +822,12 @@ limitations under the License.
         <artifactId>PrologCafe</artifactId>
         <version>1.3</version>
       </dependency>
+
+      <dependency>
+        <groupId>org.pegdown</groupId>
+        <artifactId>pegdown</artifactId>
+        <version>1.1.0</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>
 
@@ -850,5 +856,10 @@ limitations under the License.
       <id>clojars-repo</id>
       <url>http://clojars.org/repo</url>
     </repository>
+
+    <repository>
+      <id>scala-tools</id>
+      <url>http://scala-tools.org/repo-releases</url>
+    </repository>
   </repositories>
 </project>