prolog-shell: Simple command line Prolog interpreter

Since Prolog isn't the most popular language, define a small
interactive interpreter that users or site administartors can play
around with by downloading the Gerrit WAR file and executing:

  java -jar gerrit.war prolog-shell

Change-Id: I0474b59e6ace24e6e6bfda58f574add3b2bf79e0

Documentation/pgm-index.txt

@@ -18,6 +18,9 @@ link:pgm-daemon.html[daemon]::
 link:pgm-gsql.html[gsql]::
 	Administrative interface to idle database.
 
+link:pgm-prolog-shell.html[prolog-shell]::
+	Simple interactive Prolog interpreter.
+
 link:pgm-rulec.html[rulec]::
 	Compile project-specific Prolog rules to JARs.
 

Documentation/pgm-prolog-shell.txt

@@ -0,0 +1,57 @@
+prolog-shell
+============
+
+NAME
+----
+prolog-shell - Simple interactive Prolog interpreter
+
+SYNOPSIS
+--------
+[verse]
+'java' -jar gerrit.war 'prolog-shell' [-s FILE.pl ...]
+
+DESCRIPTION
+-----------
+Provides a simple interactive Prolog interpreter for development
+and testing.
+
+OPTIONS
+-------
+-s::
+	Dynamically load the Prolog source code at startup,
+	as though the user had entered `['FILE.pl'].` into
+	the interepter once it was running. This option may
+	be supplied more than once to load multiple files.
+
+EXAMPLES
+--------
+Define a simple predicate and test it:
+
+====
+	$ cat >simple.pl
+	food(apple).
+	food(orange).
+	^D
+
+	$ java -jar gerrit.war prolog-shell -s simple.pl
+	Gerrit Code Review 2.2.1-84-ge9c3992 - Interactive Prolog Shell
+	based on Prolog Cafe 1.2.5 (mantis)
+	         Copyright(C) 1997-2009 M.Banbara and N.Tamura
+	(type Ctrl-D or "halt." to exit, "['path/to/file.pl']." to load a file)
+
+	{consulting /usr/local/google/users/sop/gerrit2/gerrit/simple.pl ...}
+	{/usr/local/google/users/sop/gerrit2/gerrit/simple.pl consulted 99 msec}
+
+	| ?- food(Type).
+
+	Type = apple ? ;
+
+	Type = orange ? ;
+
+	no
+	| ?-
+====
+
+GERRIT
+------
+Part of link:index.html[Gerrit Code Review]

gerrit-launcher/src/main/java/com/google/gerrit/launcher/GerritLauncher.java

@@ -120,7 +120,17 @@ public final class GerritLauncher {
       try {
         String cn = name;
         if (cn.equals(cn.toLowerCase())) {
-          cn = cn.substring(0, 1).toUpperCase() + cn.substring(1);
+          StringBuilder buf = new StringBuilder();
+          buf.append(Character.toUpperCase(cn.charAt(0)));
+          for (int i = 1; i < cn.length(); i++) {
+            if (cn.charAt(i) == '-' && i + 1 < cn.length()) {
+              i++;
+              buf.append(Character.toUpperCase(cn.charAt(i)));
+            } else {
+              buf.append(cn.charAt(i));
+            }
+          }
+          cn = buf.toString();
         }
         clazz = Class.forName(pkg + "." + cn, true, loader);
       } catch (ClassNotFoundException cnfe) {

gerrit-pgm/src/main/java/com/google/gerrit/pgm/PrologShell.java

@@ -0,0 +1,93 @@
+// Copyright (C) 2011 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.pgm;
+
+import com.google.gerrit.pgm.util.AbstractProgram;
+
+import com.googlecode.prolog_cafe.lang.BufferingPrologControl;
+import com.googlecode.prolog_cafe.lang.HaltException;
+import com.googlecode.prolog_cafe.lang.Prolog;
+import com.googlecode.prolog_cafe.lang.PrologClassLoader;
+import com.googlecode.prolog_cafe.lang.PrologMain;
+import com.googlecode.prolog_cafe.lang.SymbolTerm;
+
+import org.kohsuke.args4j.Option;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.EnumSet;
+import java.util.List;
+
+public class PrologShell extends AbstractProgram {
+  @Option(name = "-s", multiValued = true, metaVar = "FILE.pl", usage = "file to load")
+  private List<String> fileName = new ArrayList<String>();
+
+  @Override
+  public int run() {
+    banner();
+
+    BufferingPrologControl pcl = new BufferingPrologControl();
+    pcl.setPrologClassLoader(new PrologClassLoader(getClass().getClassLoader()));
+    pcl.setEnabled(EnumSet.allOf(Prolog.Feature.class), false);
+    pcl.setEnabled(Prolog.Feature.IO, true);
+    pcl.setEnabled(Prolog.Feature.STATISTICS_RUNTIME, true);
+
+    pcl.initialize(Prolog.BUILTIN);
+    pcl.execute(Prolog.BUILTIN, "set_prolog_flag",
+        SymbolTerm.intern("print_stack_trace"),
+        SymbolTerm.intern("on"));
+
+    for (String file : fileName) {
+      String path;
+      try {
+        path = new File(file).getCanonicalPath();
+      } catch (IOException e) {
+        path = new File(file).getAbsolutePath();
+      }
+      pcl.execute(Prolog.BUILTIN, "consult", SymbolTerm.create(path));
+      System.err.println();
+      System.err.flush();
+    }
+
+    try {
+      pcl.execute(Prolog.BUILTIN, "cafeteria");
+      write("% halt\n");
+      return 0;
+    } catch (HaltException halt) {
+      write("% halt(" + halt.getStatus() + ")\n");
+      return halt.getStatus();
+    }
+  }
+
+  private void banner() {
+    System.err.format("Gerrit Code Review %s - Interactive Prolog Shell",
+        com.google.gerrit.common.Version.getVersion());
+    System.err.println();
+    System.err.println("based on " + PrologMain.VERSION);
+    System.err.println("         " + PrologMain.COPYRIGHT);
+    System.err.println("(type Ctrl-D or \"halt.\" to exit,"
+        + " \"['path/to/file.pl'].\" to load a file)");
+    System.err.println();
+    System.err.flush();
+  }
+
+  private void write(String msg) {
+    System.out.flush();
+    System.err.flush();
+    System.out.println(msg);
+    System.out.flush();
+  }
+}