Add title field to documentation index.

The title field is extracted from the first line of the txt files (in some cases
the second line). This will make the search result page looks better.

Change-Id: Ibcb03c69e6e12ca1afed702d912ef1ce4d1e0269

lib/asciidoctor/java/DocIndexer.java

@@ -12,10 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import java.io.BufferedInputStream;
+import java.io.BufferedReader;
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.FileReader;
 import java.io.IOException;
+import java.io.InputStreamReader;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.zip.ZipOutputStream;
@@ -43,6 +47,7 @@ public class DocIndexer {
   private static final Version LUCENE_VERSION = Version.LUCENE_44;
   private static final String DOC_FIELD = "doc";
   private static final String URL_FIELD = "url";
+  private static final String TITLE_FIELD = "title";
 
   @Option(name = "-z", usage = "output zip file")
   private String zipFile;
@@ -82,6 +87,17 @@ public class DocIndexer {
     IndexWriter iwriter = new IndexWriter(directory, config);
     for (String inputFile : inputFiles) {
       File file = new File(inputFile);
+
+      BufferedReader titleReader = new BufferedReader(
+          new InputStreamReader(new FileInputStream(file), "UTF-8"));
+      String title = titleReader.readLine();
+      if (title.startsWith("[[")) {
+        // Generally the first line of the txt is the title. In a few cases the
+        // first line is a "[[tag]]" and the second line is the title.
+        title = titleReader.readLine();
+      }
+      titleReader.close();
+
       String outputFile = AsciiDoctor.mapInFileToOutFile(
           inputFile, inExt, outExt);
       FileReader reader = new FileReader(file);
@@ -89,6 +105,7 @@ public class DocIndexer {
       doc.add(new TextField(DOC_FIELD, reader));
       doc.add(new StringField(
             URL_FIELD, prefix + outputFile, Field.Store.YES));
+      doc.add(new TextField(TITLE_FIELD, title, Field.Store.YES));
       iwriter.addDocument(doc);
       reader.close();
     }