--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/luan/host/Backup.java	Wed Feb 21 21:22:16 2018 -0700
@@ -0,0 +1,112 @@
+package luan.host;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.Map;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.lucene.index.SnapshotDeletionPolicy;
+import org.apache.lucene.index.IndexCommit;
+import org.apache.lucene.store.FSDirectory;
+import luan.LuanState;
+import luan.LuanTable;
+import luan.LuanException;
+import luan.modules.PackageLuan;
+import luan.modules.lucene.LuceneIndex;
+import luan.host.Log4j;
+
+
+public final class Backup {
+	private static final Logger logger = LoggerFactory.getLogger(Backup.class);
+
+	private Backup() {}  // never
+
+	private static void mkdir(File dir) {
+		if( !dir.mkdirs() )
+			throw new RuntimeException("couldn't make "+dir);
+	}
+
+	private static void link(File from,File to) throws IOException {
+		Files.createLink( to.toPath(), from.toPath() );
+	}
+
+	private static void backupNonlocal(File from,File to) throws IOException {
+		mkdir(to);
+		for( File fromChild : from.listFiles() ) {
+			File toChild = new File( to, fromChild.getName() );
+			if( fromChild.isDirectory() ) {
+				if( !fromChild.getName().equals("local") )
+					backupNonlocal( fromChild, toChild );
+			} else if( fromChild.isFile() ) {
+				link( fromChild, toChild );
+			} else {
+				throw new RuntimeException(fromChild+" isn't dir or file");
+			}
+		}
+	}
+
+	private static final String getLucenes =
+		"local Lucene = require 'luan:lucene/Lucene.luan'\n"
+		+"local Table = require 'luan:Table.luan'\n"
+		+"return Table.copy(Lucene.instances)\n"
+	;
+
+	private static void backupLucene(File from,File to) throws IOException {
+		if( !new File(from,"site/init.luan").exists() ) {
+			return;
+		}
+		String fromPath = from.getCanonicalPath() + "/";
+		LuanTable luceneInstances;
+		LuanState luan = null;
+		try {
+			if( WebHandler.isServing() ) {
+				luceneInstances = (LuanTable)WebHandler.runLuan( from.getName(), getLucenes, "getLucenes" );
+			} else {
+				luan = new LuanState();
+				WebHandler.initLuan( luan, from.toString(), from.getName() );
+				PackageLuan.load(luan,"site:/init.luan");
+				luceneInstances = (LuanTable)luan.eval(getLucenes);
+			}
+		} catch(LuanException e) {
+			throw new RuntimeException(e);
+		}
+		for( Map.Entry entry : luceneInstances.rawIterable() ) {
+			LuanTable tbl = (LuanTable)entry.getKey();
+			LuceneIndex li = (LuceneIndex)tbl.rawGet("java");
+			SnapshotDeletionPolicy snapshotDeletionPolicy = li.snapshotDeletionPolicy();
+			IndexCommit ic = snapshotDeletionPolicy.snapshot();
+			try {
+				FSDirectory fsdir = (FSDirectory)ic.getDirectory();
+				File dir = fsdir.getDirectory();
+				String dirPath = dir.toString();
+				if( !dirPath.startsWith(fromPath) )
+					throw new RuntimeException(fromPath+" "+dirPath);
+				File toDir = new File( to, dirPath.substring(fromPath.length()) );
+				mkdir(toDir);
+				for( String name : ic.getFileNames() ) {
+					link( new File(dir,name), new File(toDir,name) );
+				}
+			} finally {
+				snapshotDeletionPolicy.release(ic);
+			}
+		}
+		if( luan != null )
+			luan.close();
+	}
+
+	public static void backup(File sitesDir,File backupDir) throws IOException {
+		mkdir(backupDir);
+		for( File siteDir : sitesDir.listFiles() ) {
+			File to = new File( backupDir, siteDir.getName() );
+			backupNonlocal( siteDir, to );
+			backupLucene( siteDir, to );
+		}
+	}
+
+	public static void main(String[] args) throws Exception {
+		Log4j.initForConsole();
+		backup( new File(args[0]), new File(args[1]) );
+		System.exit(0);
+	}
+}