Implement auto-save of old game when starting a new game

The 20 most recently auto-saved games are kept in the file
DroidFish/pgn/.autosave.pgn.

Overwriting an existing game when saving a new game also auto-saves
the old game.

DroidFishApp/src/main/java/org/petero/droidfish/DroidFish.java

@@ -588,7 +588,7 @@ public class DroidFish extends Activity
         ctrl.startGame();
         if (intentPgnOrFen != null) {
             try {
-                ctrl.setFENOrPGN(intentPgnOrFen);
+                ctrl.setFENOrPGN(intentPgnOrFen, true);
                 setBoardFlip(true);
             } catch (ChessParseError e) {
                 // If FEN corresponds to illegal chess position, go into edit board mode.
@@ -1019,6 +1019,8 @@ public class DroidFish extends Activity
         });
     }
 
+    private static final int serializeVersion = 4;
+
     @Override
     protected void onSaveInstanceState(Bundle outState) {
         super.onSaveInstanceState(outState);
@@ -1026,7 +1028,7 @@ public class DroidFish extends Activity
             byte[] data = ctrl.toByteArray();
             byte[] token = data == null ? null : cache.storeBytes(data);
             outState.putByteArray("gameStateT", token);
-            outState.putInt("gameStateVersion", 3);
+            outState.putInt("gameStateVersion", serializeVersion);
         }
     }
 
@@ -1049,7 +1051,7 @@ public class DroidFish extends Activity
             Editor editor = settings.edit();
             String dataStr = byteArrToString(data);
             editor.putString("gameState", dataStr);
-            editor.putInt("gameStateVersion", 3);
+            editor.putInt("gameStateVersion", serializeVersion);
             editor.apply();
         }
         lastVisibleMillis = System.currentTimeMillis();
@@ -1568,16 +1570,17 @@ public class DroidFish extends Activity
         }
     }
 
-    static private final int RESULT_EDITBOARD = 0;
+    static private final int RESULT_EDITBOARD   =  0;
-    static private final int RESULT_SETTINGS = 1;
+    static private final int RESULT_SETTINGS    =  1;
-    static private final int RESULT_LOAD_PGN = 2;
+    static private final int RESULT_LOAD_PGN    =  2;
-    static private final int RESULT_LOAD_FEN = 3;
+    static private final int RESULT_LOAD_FEN    =  3;
-    static private final int RESULT_SELECT_SCID = 4;
+    static private final int RESULT_SAVE_PGN    =  4;
-    static private final int RESULT_OI_PGN_SAVE = 5;
+    static private final int RESULT_SELECT_SCID =  5;
-    static private final int RESULT_OI_PGN_LOAD = 6;
+    static private final int RESULT_OI_PGN_SAVE =  6;
-    static private final int RESULT_OI_FEN_LOAD = 7;
+    static private final int RESULT_OI_PGN_LOAD =  7;
-    static private final int RESULT_GET_FEN = 8;
+    static private final int RESULT_OI_FEN_LOAD =  8;
-    static private final int RESULT_EDITOPTIONS = 9;
+    static private final int RESULT_GET_FEN     =  9;
+    static private final int RESULT_EDITOPTIONS = 10;
 
     private void startEditBoard(String fen) {
         Intent i = new Intent(DroidFish.this, EditBoard.class);
@@ -1595,7 +1598,7 @@ public class DroidFish extends Activity
             if (resultCode == RESULT_OK) {
                 try {
                     String fen = data.getAction();
-                    ctrl.setFENOrPGN(fen);
+                    ctrl.setFENOrPGN(fen, true);
                     setBoardFlip(false);
                 } catch (ChessParseError ignore) {
                 }
@@ -1609,13 +1612,19 @@ public class DroidFish extends Activity
                     int modeNr = ctrl.getGameMode().getModeNr();
                     if ((modeNr != GameMode.ANALYSIS) && (modeNr != GameMode.EDIT_GAME))
                         newGameMode(GameMode.EDIT_GAME);
-                    ctrl.setFENOrPGN(pgn);
+                    ctrl.setFENOrPGN(pgn, false);
                     setBoardFlip(true);
                 } catch (ChessParseError e) {
                     DroidFishApp.toast(getParseErrString(e), Toast.LENGTH_SHORT);
                 }
             }
             break;
+        case RESULT_SAVE_PGN:
+            if (resultCode == RESULT_OK) {
+                long hash = data.getLongExtra("org.petero.droidfish.treeHash", -1);
+                ctrl.setLastSaveHash(hash);
+            }
+            break;
         case RESULT_SELECT_SCID:
             if (resultCode == RESULT_OK) {
                 String pathName = data.getAction();
@@ -1662,13 +1671,13 @@ public class DroidFish extends Activity
                     String pathName = getFilePathFromUri(data.getData());
                     loadFENFromFile(pathName);
                 }
-                setFenHelper(fen);
+                setFenHelper(fen, true);
             }
             break;
         case RESULT_LOAD_FEN:
             if (resultCode == RESULT_OK) {
                 String fen = data.getAction();
-                setFenHelper(fen);
+                setFenHelper(fen, false);
             }
             break;
         case RESULT_EDITOPTIONS:
@@ -2090,7 +2099,6 @@ public class DroidFish extends Activity
             editor.apply();
             gameMode = new GameMode(gameModeType);
         }
-//        savePGNToFile(".autosave.pgn", true);
         TimeControlData tcData = new TimeControlData();
         tcData.setTimeControl(timeControl, movesPerSession, timeIncrement);
         speech.flushQueue();
@@ -2161,10 +2169,10 @@ public class DroidFish extends Activity
                                 writer.close();
                                 loadPGNFromFile(fn);
                             } catch (IOException ex) {
-                                ctrl.setFENOrPGN(fenPgnData);
+                                ctrl.setFENOrPGN(fenPgnData, true);
                             }
                         } else {
-                            ctrl.setFENOrPGN(fenPgnData);
+                            ctrl.setFENOrPGN(fenPgnData, true);
                         }
                         setBoardFlip(true);
                     } catch (ChessParseError e) {
@@ -3476,8 +3484,33 @@ public class DroidFish extends Activity
         i.setAction("org.petero.droidfish.saveFile");
         i.putExtra("org.petero.droidfish.pathname", pathName);
         i.putExtra("org.petero.droidfish.pgn", pgnToken);
-        i.putExtra("org.petero.droidfish.silent", false);
+        setEditPGNBackup(i, pathName);
-        startActivity(i);
+        startActivityForResult(i, RESULT_SAVE_PGN);
+    }
+
+    /** Set a Boolean value in the Intent to decide if backups should be made
+     *  when games in a PGN file are overwritten or deleted. */
+    private void setEditPGNBackup(Intent i, String pathName) {
+        boolean backup = storageAvailable() && !pathName.equals(getAutoSaveFile());
+        i.putExtra("org.petero.droidfish.backup", backup);
+    }
+
+    /** Get the full path to the auto-save file. */
+    private static String getAutoSaveFile() {
+        String sep = File.separator;
+        return Environment.getExternalStorageDirectory() + sep + pgnDir + sep + ".autosave.pgn";
+    }
+
+    @Override
+    public void autoSaveGameIfAllowed(String pgn) {
+        if (storageAvailable())
+            autoSaveGame(pgn);
+    }
+
+    /** Save a copy of the pgn data in the .autosave.pgn file. */
+    public static void autoSaveGame(String pgn) {
+        PGNFile pgnFile = new PGNFile(getAutoSaveFile());
+        pgnFile.autoSave(pgn);
     }
 
     /** Load a PGN game from a file. */
@@ -3489,6 +3522,7 @@ public class DroidFish extends Activity
         Intent i = new Intent(DroidFish.this, EditPGNLoad.class);
         i.setAction("org.petero.droidfish.loadFile");
         i.putExtra("org.petero.droidfish.pathname", pathName);
+        setEditPGNBackup(i, pathName);
         startActivityForResult(i, RESULT_LOAD_PGN);
     }
 
@@ -3506,11 +3540,11 @@ public class DroidFish extends Activity
         startActivityForResult(i, RESULT_LOAD_FEN);
     }
 
-    private void setFenHelper(String fen) {
+    private void setFenHelper(String fen, boolean setModified) {
         if (fen == null)
             return;
         try {
-            ctrl.setFENOrPGN(fen);
+            ctrl.setFENOrPGN(fen, setModified);
         } catch (ChessParseError e) {
             // If FEN corresponds to illegal chess position, go into edit board mode.
             try {

DroidFishApp/src/main/java/org/petero/droidfish/GUIInterface.java

@@ -108,4 +108,7 @@ public interface GUIInterface {
 
     /** Return true if only main-line moves are to be kept. */
     boolean discardVariations();
+
+    /** Save the current game to the auto-save file, if storage permission has been granted. */
+    void autoSaveGameIfAllowed(String pgn);
 }

DroidFishApp/src/main/java/org/petero/droidfish/Util.java

@@ -128,4 +128,26 @@ public final class Util {
             ((MoveListView) v).setTextColor(fg);
         }
     }
+
+    /** Return a hash value for a string, with better quality than String.hashCode(). */
+    public static long stringHash(String s) {
+        int n = s.length();
+        long h = n;
+        for (int i = 0; i < n; i += 4) {
+            long tmp = s.charAt(i) & 0xffff;
+            try {
+                tmp = (tmp << 16) | (s.charAt(i+1) & 0xffff);
+                tmp = (tmp << 16) | (s.charAt(i+2) & 0xffff);
+                tmp = (tmp << 16) | (s.charAt(i+3) & 0xffff);
+            } catch (IndexOutOfBoundsException ignore) {}
+
+            h += tmp;
+
+            h *= 0x7CF9ADC6FE4A7653L;
+            h ^= h >>> 37;
+            h *= 0xC25D3F49433E7607L;
+            h ^= h >>> 43;
+        }
+        return h;
+    }
 }

DroidFishApp/src/main/java/org/petero/droidfish/activities/EditPGN.java

@@ -30,7 +30,6 @@ import android.os.Bundle;
 import android.preference.PreferenceManager;
 import android.text.Editable;
 import android.text.TextWatcher;
-import android.util.Pair;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
@@ -45,6 +44,7 @@ import androidx.appcompat.app.AppCompatActivity;
 import androidx.databinding.DataBindingUtil;
 
 import org.petero.droidfish.ColorTheme;
+import org.petero.droidfish.DroidFish;
 import org.petero.droidfish.DroidFishApp;
 import org.petero.droidfish.ObjectCache;
 import org.petero.droidfish.R;
@@ -74,6 +74,7 @@ public abstract class EditPGN extends AppCompatActivity {
     private String lastFileName = "";
     private long lastModTime = -1;
     private boolean useRegExp = false;
+    private boolean backup = false; // If true, backup PGN games before overwriting
 
     private Thread workThread = null;
     private boolean canceled = false;
@@ -109,6 +110,7 @@ public abstract class EditPGN extends AppCompatActivity {
         Intent i = getIntent();
         String action = i.getAction();
         String fileName = i.getStringExtra("org.petero.droidfish.pathname");
+        backup = i.getBooleanExtra("org.petero.droidfish.backup", false);
         canceled = false;
         if ("org.petero.droidfish.loadFile".equals(action)) {
             pgnFile = new PGNFile(fileName);
@@ -167,36 +169,37 @@ public abstract class EditPGN extends AppCompatActivity {
             loadGame = false;
             String token = i.getStringExtra("org.petero.droidfish.pgn");
             pgnToSave = (new ObjectCache()).retrieveString(token);
-            boolean silent = i.getBooleanExtra("org.petero.droidfish.silent", false);
+            pgnFile = new PGNFile(fileName);
-            if (silent) { // Silently append to file
+            showDialog(PROGRESS_DIALOG);
-                PGNFile pgnFile2 = new PGNFile(fileName);
+            workThread = new Thread(() -> {
-                pgnFile2.appendPGN(pgnToSave);
+                if (!readFile())
-            } else {
+                    return;
-                pgnFile = new PGNFile(fileName);
+                runOnUiThread(() -> {
-                showDialog(PROGRESS_DIALOG);
+                    if (canceled) {
-                workThread = new Thread(() -> {
+                        setResult(RESULT_CANCELED);
-                    if (!readFile())
+                        finish();
-                        return;
+                    } else if (gamesInFile.isEmpty()) {
-                    runOnUiThread(() -> {
+                        pgnFile.appendPGN(pgnToSave, false);
-                        if (canceled) {
+                        saveFileFinished();
-                            setResult(RESULT_CANCELED);
+                    } else {
-                            finish();
+                        showList();
-                        } else if (gamesInFile.isEmpty()) {
+                    }
-                            pgnFile.appendPGN(pgnToSave);
-                            finish();
-                        } else {
-                            showList();
-                        }
-                    });
                 });
-                workThread.start();
+            });
-            }
+            workThread.start();
         } else { // Unsupported action
             setResult(RESULT_CANCELED);
             finish();
         }
     }
 
+    private void saveFileFinished() {
+        Intent i = new Intent();
+        i.putExtra("org.petero.droidfish.treeHash", Util.stringHash(pgnToSave));
+        setResult(RESULT_OK, i);
+        finish();
+    }
+
     @Override
     protected void attachBaseContext(Context newBase) {
         super.attachBaseContext(DroidFishApp.setLanguage(newBase, false));
@@ -403,8 +406,9 @@ public abstract class EditPGN extends AppCompatActivity {
                     finish();
                     return;
                 }
-                pgnFile.replacePGN(pgnToSave, giToReplace);
+                doBackup(giToReplace);
-                finish();
+                pgnFile.replacePGN(pgnToSave, giToReplace, false);
+                saveFileFinished();
             });
             return builder.create();
         }
@@ -475,6 +479,7 @@ public abstract class EditPGN extends AppCompatActivity {
     }
 
     private void deleteGame(GameInfo gi) {
+        doBackup(gi);
         if (pgnFile.deleteGame(gi, gamesInFile)) {
             createAdapter();
             String s = binding.selectGameFilter.getText().toString();
@@ -485,6 +490,15 @@ public abstract class EditPGN extends AppCompatActivity {
         }
     }
 
+    private void doBackup(GameInfo gi) {
+        if (!backup)
+            return;
+        String pgn = pgnFile.readOneGame(gi);
+        if (pgn == null || pgn.isEmpty())
+            return;
+        DroidFish.autoSaveGame(pgn);
+    }
+
     private void createAdapter() {
         aa = new GameAdapter<GameInfo>(this, R.layout.select_game_list_item, gamesInFile) {
             @Override

DroidFishApp/src/main/java/org/petero/droidfish/activities/PGNFile.java

@@ -121,6 +121,7 @@ public class PGNFile {
         public void reset() {
             len = 0;
         }
+        @Override
         public String toString() {
             return new String(buf, 0, len);
         }
@@ -421,11 +422,37 @@ public class PGNFile {
     }
 
     /** Append PGN to the end of this PGN file. */
-    public void appendPGN(String pgn) {
+    public void appendPGN(String pgn, boolean silent) {
         mkDirs();
         try (FileWriter fw = new FileWriter(fileName, true)) {
             fw.write(pgn);
-            DroidFishApp.toast(R.string.game_saved, Toast.LENGTH_SHORT);
+            if (!silent)
+                DroidFishApp.toast(R.string.game_saved, Toast.LENGTH_SHORT);
+        } catch (IOException e) {
+            DroidFishApp.toast(R.string.failed_to_save_game, Toast.LENGTH_SHORT);
+        }
+    }
+
+    /** Save a PGN game first in the file and remove games at the end of the file
+     *  to enforce a maximum number of games in the auto-save file. */
+    public void autoSave(String pgn) {
+        final int maxAutoSaveGames = 20;
+        try {
+            if (!fileName.exists()) {
+                appendPGN(pgn, true);
+            } else {
+                ArrayList<GameInfo> gamesInFile = getGameInfo(null, null);
+                for (int i = gamesInFile.size() - 1; i >= 0; i--) {
+                    GameInfo gi = gamesInFile.get(i);
+                    String oldGame = readOneGame(gi);
+                    if (pgn.equals(oldGame))
+                        deleteGame(gi, gamesInFile);
+                }
+                while (gamesInFile.size() > maxAutoSaveGames - 1)
+                    deleteGame(gamesInFile.get(gamesInFile.size() - 1), gamesInFile);
+                GameInfo gi = new GameInfo().setNull(0);
+                replacePGN(pgn, gi, true);
+            }
         } catch (IOException e) {
             DroidFishApp.toast(R.string.failed_to_save_game, Toast.LENGTH_SHORT);
         }
@@ -463,7 +490,7 @@ public class PGNFile {
         return false;
     }
 
-    void replacePGN(String pgnToSave, GameInfo gi) {
+    void replacePGN(String pgnToSave, GameInfo gi, boolean silent) {
         try {
             File tmpFile = new File(fileName + ".tmp_delete");
             try (RandomAccessFile fileReader = new RandomAccessFile(fileName, "r");
@@ -475,7 +502,8 @@ public class PGNFile {
             }
             if (!tmpFile.renameTo(fileName))
                 throw new IOException();
-            DroidFishApp.toast(R.string.game_saved, Toast.LENGTH_SHORT);
+            if (!silent)
+                DroidFishApp.toast(R.string.game_saved, Toast.LENGTH_SHORT);
         } catch (IOException e) {
             DroidFishApp.toast(R.string.failed_to_save_game, Toast.LENGTH_SHORT);
         }
@@ -494,6 +522,7 @@ public class PGNFile {
         }
     }
 
+    /** Delete the file. */
     boolean delete() {
         return fileName.delete();
     }

DroidFishApp/src/main/java/org/petero/droidfish/gamelogic/DroidChessController.java

@@ -49,7 +49,7 @@ import org.petero.droidfish.gamelogic.GameTree.Node;
 /** The glue between the chess engine and the GUI. */
 public class DroidChessController {
     private DroidComputerPlayer computerPlayer = null;
-    private PgnToken.PgnTokenReceiver gameTextListener = null;
+    private PgnToken.PgnTokenReceiver gameTextListener;
     private BookOptions bookOptions = new BookOptions();
     private EngineOptions engineOptions = new EngineOptions();
     private Game game = null;
@@ -94,10 +94,25 @@ public class DroidChessController {
         }
         computerPlayer.queueStartEngine(searchId, engine);
         searchId++;
+        Game oldGame = game;
         game = new Game(gameTextListener, tcData);
         computerPlayer.uciNewGame();
         setPlayerNames(game);
         updateGameMode();
+        game.resetModified(pgnOptions);
+        autoSaveOldGame(oldGame, game.treeHashSignature);
+    }
+
+    /** Save old game if has been modified since start/load of game and is
+     *  not equal to the new game. */
+    private void autoSaveOldGame(Game oldGame, long newGameHash) {
+        if (oldGame == null)
+            return;
+        String pgn = oldGame.tree.toPGN(pgnOptions);
+        long oldGameOrigHash = oldGame.treeHashSignature;
+        long oldGameCurrHash = Util.stringHash(pgn);
+        if (oldGameCurrHash != oldGameOrigHash && oldGameCurrHash != newGameHash)
+            gui.autoSaveGameIfAllowed(pgn);
     }
 
     /** Start playing a new game. Should be called after newGame(). */
@@ -137,7 +152,7 @@ public class DroidChessController {
         }
     }
 
-    public GameMode getGameMode() {
+    public final GameMode getGameMode() {
         return gameMode;
     }
 
@@ -245,7 +260,7 @@ public class DroidChessController {
     }
 
     /** Parse a string as FEN or PGN data. */
-    public final synchronized void setFENOrPGN(String fenPgn) throws ChessParseError {
+    public final synchronized void setFENOrPGN(String fenPgn, boolean setModified) throws ChessParseError {
         if (!fenPgn.isEmpty() && fenPgn.charAt(0) == '\ufeff')
             fenPgn = fenPgn.substring(1); // Remove BOM
         Game newGame = new Game(gameTextListener, game.timeController.tcData);
@@ -260,6 +275,7 @@ public class DroidChessController {
             newGame.tree.translateMoves();
         }
         searchId++;
+        Game oldGame = game;
         game = newGame;
         gameTextListener.clear();
         updateGameMode();
@@ -268,6 +284,14 @@ public class DroidChessController {
         updateComputeThreads();
         gui.setSelection(-1);
         updateGUI();
+        game.resetModified(pgnOptions);
+        autoSaveOldGame(oldGame, game.treeHashSignature);
+        if (setModified)
+            game.treeHashSignature = oldGame.treeHashSignature;
+    }
+
+    public final synchronized void setLastSaveHash(long hash) {
+        game.treeHashSignature = hash;
     }
 
     /** True if human's turn to make a move. (True in analysis mode.) */

DroidFishApp/src/main/java/org/petero/droidfish/gamelogic/Game.java

@@ -27,11 +27,13 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.petero.droidfish.PGNOptions;
+import org.petero.droidfish.Util;
 import org.petero.droidfish.gamelogic.GameTree.Node;
 
 public class Game {
     boolean pendingDrawOffer;
     public GameTree tree;
+    long treeHashSignature;  // Hash corresponding to "tree" when last saved to file
     TimeControl timeController;
     private boolean gamePaused;
     /** If true, add new moves as mainline moves. */
@@ -51,6 +53,8 @@ public class Game {
     /** De-serialize from input stream. */
     final void readFromStream(DataInputStream dis, int version) throws IOException, ChessParseError {
         tree.readFromStream(dis, version);
+        if (version >= 4)
+            treeHashSignature = dis.readLong();
         if (version >= 3)
             timeController.readFromStream(dis, version);
         updateTimeControl(true);
@@ -59,9 +63,15 @@ public class Game {
     /** Serialize to output stream. */
     final synchronized void writeToStream(DataOutputStream dos) throws IOException {
         tree.writeToStream(dos);
+        dos.writeLong(treeHashSignature);
         timeController.writeToStream(dos);
     }
 
+    /** Set game to "not modified" state. */
+    final void resetModified(PGNOptions options) {
+        treeHashSignature = Util.stringHash(tree.toPGN(options));
+    }
+
     public final void setGamePaused(boolean gamePaused) {
         if (gamePaused != this.gamePaused) {
             this.gamePaused = gamePaused;

README.md

@@ -458,6 +458,15 @@ game with the selected position.
 
 Saving a position to a FEN/EPD file has not been implemented.
 
+## Autosave
+
+When an action is performed that causes the current game to be discarded, the
+game is automatically saved in the file `DroidFish/pgn/.autosave.pgn` before
+being discarded. The autosave file has a maximum size of 20 games and the most
+recently autosaved game is stored first in the file. If the number of games
+becomes too large, the oldest stored game is removed from the file.
+
+
 ## OI File Manager
 
 If the [*OI File Manager*](https://play.google.com/store/apps/details?id=org.openintents.filemanager)