bundles/org.simantics.spreadsheet.graph/src/org/simantics/spreadsheet/graph/SpreadsheetGraphUtils.java

   1 package org.simantics.spreadsheet.graph;
   2
   3 import java.io.File;
   4 import java.io.FileNotFoundException;
   5 import java.io.FileOutputStream;
   6 import java.io.IOException;
   7 import java.io.ObjectOutputStream;
   8 import java.util.ArrayList;
   9 import java.util.Collection;
  10 import java.util.HashMap;
  11 import java.util.Iterator;
  12 import java.util.List;
  13 import java.util.Map;
  14
  15 import org.simantics.Simantics;
  16 import org.simantics.databoard.Bindings;
  17 import org.simantics.databoard.binding.mutable.Variant;
  18 import org.simantics.databoard.util.binary.RandomAccessBinary;
  19 import org.simantics.datatypes.DatatypeResource;
  20 import org.simantics.datatypes.literal.Font;
  21 import org.simantics.datatypes.literal.RGB;
  22 import org.simantics.datatypes.utils.BTree;
  23 import org.simantics.db.ReadGraph;
  24 import org.simantics.db.Resource;
  25 import org.simantics.db.WriteGraph;
  26 import org.simantics.db.common.request.BinaryRead;
  27 import org.simantics.db.common.request.ObjectsWithType;
  28 import org.simantics.db.common.request.UnaryRead;
  29 import org.simantics.db.common.utils.LiteralFileUtil;
  30 import org.simantics.db.exception.DatabaseException;
  31 import org.simantics.db.exception.ServiceException;
  32 import org.simantics.db.layer0.util.Layer0Utils;
  33 import org.simantics.db.layer0.variable.Variable;
  34 import org.simantics.db.layer0.variable.Variables;
  35 import org.simantics.db.procedure.Listener;
  36 import org.simantics.db.service.ClusteringSupport;
  37 import org.simantics.layer0.Layer0;
  38 import org.simantics.scl.runtime.tuple.Tuple2;
  39 import org.simantics.simulator.toolkit.StandardRealm;
  40 import org.simantics.spreadsheet.ExternalRef;
  41 import org.simantics.spreadsheet.Range;
  42 import org.simantics.spreadsheet.Spreadsheets;
  43 import org.simantics.spreadsheet.graph.synchronization.SpreadsheetSynchronizationEventHandler;
  44 import org.simantics.spreadsheet.resource.SpreadsheetResource;
  45 import org.simantics.spreadsheet.solver.SheetNode;
  46 import org.simantics.spreadsheet.solver.SpreadsheetBook;
  47 import org.simantics.spreadsheet.solver.SpreadsheetEngine;
  48 import org.simantics.spreadsheet.solver.SpreadsheetLine;
  49 import org.simantics.spreadsheet.solver.SpreadsheetStyle;
  50 import org.simantics.spreadsheet.util.SpreadsheetUtils;
  51 import org.simantics.structural.synchronization.client.Synchronizer;
  52 import org.slf4j.Logger;
  53 import org.slf4j.LoggerFactory;
  54
  55 import gnu.trove.iterator.TObjectIntIterator;
  56 import gnu.trove.map.hash.TObjectIntHashMap;
  57
  58 public class SpreadsheetGraphUtils {
  59
  60     private static final Logger LOGGER = LoggerFactory.getLogger(SpreadsheetGraphUtils.class);
  61
  62     public static File extractInitialCondition(ReadGraph graph, Resource ic) throws DatabaseException, IOException {
  63
  64         SpreadsheetResource SR = SpreadsheetResource.getInstance(graph);
  65
  66         File temp = Simantics.getTempfile("excel","ic");
  67
  68         LiteralFileUtil.copyRandomAccessBinaryToFile(graph, ic, SR.InitialCondition_bytes, temp);
  69         if (temp.length() == 0)
  70             throw new FileNotFoundException("Snapshot file does not exist.\nThis seems to be a database bug that manifests as total loss of state file data.\nThis error prevents the program from crashing.");
  71
  72         return temp;
  73
  74     }
  75
  76     public static RandomAccessBinary getOrCreateRandomAccessBinary(WriteGraph graph, Resource initialCondition) throws DatabaseException, IOException {
  77
  78         SpreadsheetResource SR = SpreadsheetResource.getInstance(graph);
  79
  80         // We put snapshot literals in their own clusters for now just to be safe
  81         Resource literal = graph.getPossibleObject(initialCondition, SR.InitialCondition_bytes);
  82         if (literal != null) {
  83             RandomAccessBinary rab = graph.getRandomAccessBinary(literal);
  84             rab.position(0);
  85             rab.removeBytes(rab.length(), RandomAccessBinary.ByteSide.Right);
  86             return rab;
  87         } else {
  88             Layer0 L0 = Layer0.getInstance(graph);
  89             ClusteringSupport cs = graph.getService(ClusteringSupport.class);
  90             literal = graph.newResource(cs.createCluster());
  91             graph.claim(literal, L0.InstanceOf, null, L0.ByteArray);
  92             graph.claim(initialCondition, SR.InitialCondition_bytes, SR.InitialCondition_bytes_Inverse, literal);
  93             return graph.createRandomAccessBinary(literal, Bindings.BYTE_ARRAY.type(), null);
  94         }
  95     }
  96
  97     public static Resource saveInitialCondition(WriteGraph graph, Variable run, Resource container, String name) throws DatabaseException {
  98
  99                 String sessionName = run.getParent(graph).getURI(graph);
 100
 101                 Resource bookResource = run.getRepresents(graph);
 102
 103         StandardRealm<SheetNode, SpreadsheetBook> realm = SpreadsheetSessionManager.getInstance().getOrCreateRealm(graph, sessionName);
 104         SpreadsheetBook book = realm.getEngine();
 105
 106         try {
 107
 108                 File temp = Simantics.getTempfile("excel", "ic");
 109                 System.err.println("Saving initial condition to " + temp.getAbsolutePath());
 110
 111                         FileOutputStream fileOut = new FileOutputStream(temp);
 112                         ObjectOutputStream out = new ObjectOutputStream(fileOut);
 113                         out.writeObject(book);
 114                         out.close();
 115                         fileOut.close();
 116
 117                         Layer0 L0 = Layer0.getInstance(graph);
 118                 SpreadsheetResource SR = SpreadsheetResource.getInstance(graph);
 119                         Resource ic = graph.newResource();
 120                         graph.claim(ic, L0.InstanceOf, SR.InitialCondition);
 121                         graph.addLiteral(ic, L0.HasName, L0.NameOf, L0.String, name, Bindings.STRING);
 122
 123                 RandomAccessBinary rab = getOrCreateRandomAccessBinary(graph, ic);
 124                 LiteralFileUtil.copyRandomAccessBinaryFromFile(temp, rab);
 125
 126                         graph.claim(container, L0.ConsistsOf, L0.PartOf, ic);
 127
 128                         graph.deny(bookResource, SR.HasInitialCondition);
 129                         graph.claim(bookResource, SR.HasInitialCondition, ic);
 130                         graph.claim(ic, SR.InitialCondition_ConditionOf, bookResource);
 131
 132                         setDefaultInitialConditionForBook(graph, bookResource, ic);
 133
 134                 return ic;
 135
 136         } catch (IOException e) {
 137
 138                 throw new DatabaseException(e);
 139
 140         }
 141     }
 142
 143     public static void setDefaultInitialConditionForBook(WriteGraph graph, Resource book, Resource ic) throws ServiceException {
 144         SpreadsheetResource SR = SpreadsheetResource.getInstance(graph);
 145         graph.deny(book, SR.Book_HasDefaultInitialCondition);
 146         graph.claim(ic, SR.InitialCondition_DefaultConditionOf, book);
 147     }
 148
 149     public static void evaluateAll(ReadGraph graph, Variable run) throws DatabaseException {
 150
 151                 String sessionName = run.getParent(graph).getURI(graph);
 152         StandardRealm<SheetNode, SpreadsheetBook> realm = SpreadsheetSessionManager.getInstance().getOrCreateRealm(graph, sessionName);
 153         SpreadsheetBook book = realm.getEngine();
 154         book.accept(new EvaluateAll(book));
 155
 156     }
 157
 158     public static void invalidateAll(ReadGraph graph, Variable run) throws DatabaseException {
 159
 160                 String sessionName = run.getParent(graph).getURI(graph);
 161         StandardRealm<SheetNode, SpreadsheetBook> realm = SpreadsheetSessionManager.getInstance().getOrCreateRealm(graph, sessionName);
 162         SpreadsheetBook book = realm.getEngine();
 163         book.accept(new InvalidateAll());
 164         realm.getNodeManager().refreshVariables();
 165
 166     }
 167
 168     public static boolean fullSynchronization(ReadGraph graph, Variable run) throws DatabaseException {
 169         return partialSynchronization(graph, run, null);
 170     }
 171
 172     public static boolean partialSynchronization(ReadGraph graph, Variable run, TObjectIntHashMap<Variable> changeFlags) throws DatabaseException {
 173
 174         Synchronizer synchronizer = new Synchronizer(graph);
 175                 String sessionName = run.getParent(graph).getURI(graph);
 176
 177         Resource bookResource = run.getRepresents(graph);
 178         Variable configuration = Variables.getVariable(graph, bookResource);
 179
 180         StandardRealm<SheetNode, SpreadsheetBook> realm = SpreadsheetSessionManager.getInstance().getOrCreateRealm(graph, sessionName);
 181         SpreadsheetBook book = realm.getEngine();
 182
 183         SpreadsheetSynchronizationEventHandler handler = new SpreadsheetSynchronizationEventHandler(graph, book);
 184
 185         if (changeFlags == null) {
 186             synchronizer.fullSynchronization(configuration, handler);
 187         } else {
 188
 189             TObjectIntIterator<Variable> iter = changeFlags.iterator();
 190             iter.advance();
 191             Variable row = iter.key();
 192
 193             Variable rowParent = row.getParent(graph);
 194             while (!rowParent.equals(configuration)) {
 195                 changeFlags.put(rowParent, 1);
 196                 rowParent = rowParent.getParent(graph);
 197             }
 198
 199             changeFlags.put(configuration, 1);
 200
 201             synchronizer.partialSynchronization(configuration, handler, changeFlags);
 202         }
 203
 204         realm.getNodeManager().fireNodeListeners();
 205         return handler.getDidChanges();
 206
 207     }
 208
 209     public static Variable findCell(ReadGraph graph, Variable run, String reference) throws DatabaseException {
 210
 211         int pos = reference.indexOf("!");
 212         String sheetName = reference.substring(0, pos);
 213         String cellName = reference.substring(pos+1);
 214
 215                 String sessionName = run.getParent(graph).getURI(graph);
 216         StandardRealm<SheetNode, SpreadsheetBook> realm = SpreadsheetSessionManager.getInstance().getOrCreateRealm(graph, sessionName);
 217         SpreadsheetBook book = realm.getEngine();
 218         SpreadsheetEngine engine = book.getEngine(sheetName);
 219         if(engine == null) return null;
 220
 221         Range r = Spreadsheets.decodeCellAbsolute(cellName);
 222         SpreadsheetLine line = engine.getLine(r.startRow);
 223         if(line == null) return null;
 224
 225         String path = line.getPath();
 226         if(path == null) return null;
 227
 228         Variable lineVariable = run.browse(graph, path);
 229         if(lineVariable==null) return null;
 230
 231         return lineVariable.getChild(graph, cellName);
 232
 233     }
 234
 235
 236
 237     public static List<Variable> possibleConfigurationCellVariables(ReadGraph graph, Variable sheet, Range range) throws DatabaseException {
 238         List<Variable> rowVariables = possibleConfigurationLineVariables(graph, sheet, range);
 239         List<Variable> result = new ArrayList<>();
 240         for (Variable variable : rowVariables) {
 241             Collection<Variable> children = variable.getChildren(graph);
 242             for (Variable child : children) {
 243                 if (variableInRange(graph, child, range)) {
 244                     result.add(child);
 245                 }
 246             }
 247         }
 248         return result;
 249     }
 250
 251     public static Map<Integer, Resource> possibleConfigurationLineResources(ReadGraph graph, Variable sheet, Range range) throws DatabaseException {
 252         Variable lines = sheet.getPossibleChild(graph, "Lines");
 253         if (lines == null)
 254             throw new DatabaseException("Invalid input variable " + sheet.getURI(graph));
 255         Resource linesR = lines.getRepresents(graph);
 256         BTree bt = new BTree(graph, linesR);
 257         List<Tuple2> tuples = bt.searchRangeBTree(graph, Variant.ofInstance(range.startRow), Variant.ofInstance(range.endRow));
 258         Map<Integer, Resource> result = new HashMap<>(tuples.size());
 259         for (Tuple2 tuple : tuples) {
 260             Integer lineNumber = (Integer)((Variant)tuple.c0).getValue();
 261             Resource resource = (Resource)tuple.c1;
 262             result.put(lineNumber, resource);
 263         }
 264         return result;
 265     }
 266
 267     public static List<Variable> possibleConfigurationLineVariables(ReadGraph graph, Variable sheet, Range range) throws DatabaseException {
 268         Map<Integer, Resource> rows = possibleConfigurationLineResources(graph, sheet, range);
 269         List<Variable> result = new ArrayList<>(rows.size());
 270         for (Resource row: rows.values()) {
 271             Variable lineVar = Variables.getPossibleVariable(graph, row);
 272             if (lineVar != null)
 273                 result.add(lineVar);
 274         }
 275         return result;
 276     }
 277
 278     public static List<Variable> possibleRunLineVariables(ReadGraph graph, Variable sheetRun, Range range) throws DatabaseException {
 279
 280         Variable run = sheetRun.getParent(graph);
 281
 282         String sheetName = sheetRun.getName(graph);
 283         String sessionName = run.getParent(graph).getURI(graph);
 284
 285         StandardRealm<SheetNode, SpreadsheetBook> realm = SpreadsheetSessionManager.getInstance().getOrCreateRealm(graph, sessionName);
 286         SpreadsheetBook book = realm.getEngine();
 287
 288         SpreadsheetEngine engine = book.getEngine(sheetName);
 289         if(engine == null) return null;
 290
 291         List<Variable> result = new ArrayList<>();
 292
 293         int end = range.endRow < engine.lines.getMaxRow() ? range.endRow : engine.lines.getMaxRow();
 294         for (int i = range.startRow; i <= end; i++) {
 295                 SpreadsheetLine line = engine.getLine(i);
 296                 if(line == null)
 297                         continue;
 298
 299                 String path = line.getPath();
 300                 path = line.getPath();
 301                 if(path == null)
 302                         continue;
 303
 304                 Variable lineVariable = run.browse(graph, path);
 305                 if(lineVariable==null)
 306                         continue;
 307                 result.add(lineVariable);
 308         }
 309
 310         return result;
 311     }
 312
 313     public static List<Variable> possibleRunCellVariables(ReadGraph graph, Variable sheetRun, Range range) throws DatabaseException {
 314         List<Variable> runLineVariable = possibleRunLineVariables(graph, sheetRun, range);
 315         List<Variable> result = new ArrayList<>();
 316         for (Variable variable : runLineVariable) {
 317 //              System.out.println("line: " + variable.getURI(graph));
 318             for (Variable child : variable.getChildren(graph)) {
 319 //              System.out.print("cell : " + child.getURI(graph));
 320                 if (variableInRange(graph, child, range)) {
 321                     result.add(child);
 322                 }
 323             }
 324         }
 325         return result;
 326     }
 327
 328     private static boolean variableInRange(ReadGraph graph, Variable child, Range range) throws DatabaseException {
 329         String name = child.getName(graph);
 330         Range childRange = Spreadsheets.decodeCellAbsolute(name);
 331 //        System.out.print(" and range " + childRange);
 332         if (childRange != null && range.contains(childRange)) {
 333 //              System.out.println(" => range.contains(childRange) = true");
 334             return true;
 335         }
 336 //        System.out.println();
 337         return false;
 338     }
 339
 340     public static Map<Integer, Resource> createConfigurationLineResources(WriteGraph graph, Variable sheet, Range range) throws DatabaseException {
 341         Layer0 L0 = Layer0.getInstance(graph);
 342         SpreadsheetResource SHEET = SpreadsheetResource.getInstance(graph);
 343
 344         Variable lines = sheet.getPossibleChild(graph, "Lines");
 345         if (lines == null)
 346             throw new DatabaseException("Invalid input variable " + sheet.getURI(graph));
 347         Resource linesR = lines.getRepresents(graph);
 348         BTree bt = new BTree(graph, linesR);
 349
 350         Map<Integer, Resource> result = new HashMap<>();
 351         for (int lineNumber = range.startRow; lineNumber <= range.endRow; lineNumber++) {
 352             Resource line = graph.newResource();
 353             graph.claim(line, L0.InstanceOf, null, SHEET.Line);
 354             graph.claimLiteral(line, L0.HasName, L0.NameOf, L0.String, "Row" + lineNumber, Bindings.STRING);
 355             bt.insertBTree(graph, Variant.ofInstance(lineNumber), line);
 356             result.put(lineNumber, line);
 357         }
 358         return result;
 359     }
 360
 361     public static List<Variable> getOrCreateConfigurationCellVariables(WriteGraph graph, Variable sheet, Range range) throws DatabaseException {
 362
 363         List<Variable> rows = possibleConfigurationLineVariables(graph, sheet, range);
 364         if (rows.isEmpty()) {
 365             createConfigurationLineResources(graph, sheet, range);
 366             rows = possibleConfigurationLineVariables(graph, sheet, range);
 367         }
 368
 369         List<Variable> cells = possibleConfigurationCellVariables(graph, sheet, range);
 370         if (cells.isEmpty()) {
 371             Iterator<Variable> rowIterator = rows.iterator();
 372             for (int rowNumber = range.startRow; rowNumber <= range.endRow; rowNumber++) {
 373                 Variable row = rowIterator.next();
 374                 for (int colNumber = range.startColumn; colNumber <= range.endColumn; colNumber++) {
 375                     String location = Spreadsheets.cellName(rowNumber, colNumber);
 376                     defaultCreateCell(graph, row, location, new Variant(Bindings.STRING, ""));
 377                 }
 378             }
 379         }
 380
 381         cells = possibleConfigurationCellVariables(graph, sheet, range);
 382         if(cells.isEmpty())
 383             throw new DatabaseException("Unexpected problem while creating spreadsheet cell at '" + range + "'");
 384
 385         return cells;
 386     }
 387
 388     private static void defaultCreateCell(WriteGraph graph, Variable parent, String location, Variant value) throws DatabaseException {
 389
 390         Layer0 L0 = Layer0.getInstance(graph);
 391         SpreadsheetResource SHEET = SpreadsheetResource.getInstance(graph);
 392         Resource container = parent.getRepresents(graph);
 393
 394         Resource cell = graph.newResource();
 395         graph.claim(cell, L0.InstanceOf, null, SHEET.TextCell);
 396         graph.addLiteral(cell, L0.HasName, L0.NameOf, L0.String, location, Bindings.STRING);
 397         graph.addLiteral(cell, SHEET.Cell_content, SHEET.Cell_content_Inverse, L0.Variant, value, Bindings.VARIANT);
 398         graph.claim(cell, L0.PartOf, container);
 399
 400         Resource book = Variables.getContext(graph, parent).getRepresents(graph);
 401
 402
 403         Collection<Resource> objects = graph.sync(new ObjectsWithType(book, L0.ConsistsOf, SHEET.Style));
 404
 405         int styleId = SpreadsheetStyle.empty().getStyleId();
 406         Resource style = null;
 407         for (Resource possibleStyle : objects) {
 408             int possibleStyleId = graph.getRelatedValue2(possibleStyle, SHEET.Style_id, Bindings.INTEGER);
 409             if (possibleStyleId == styleId) {
 410                 style = possibleStyle;
 411                 break;
 412             }
 413         }
 414
 415         if (style == null) {
 416             style = graph.newResource();
 417             graph.claim(style, L0.InstanceOf, null, SHEET.Style);
 418             graph.claim(style, L0.PartOf, book);
 419
 420             int id = objects.size();
 421             graph.claimLiteral(style, L0.HasName, "Style_" + id);
 422             graph.claimLiteral(style, SHEET.Style_id, styleId, Bindings.INTEGER);
 423         }
 424         graph.claim(cell, SHEET.Cell_HasStyle, style);
 425         Layer0Utils.addCommentMetadata(graph, "Created cell on location " + location + " with value " + value.toString());
 426     }
 427
 428     public static Resource createStyle(WriteGraph graph, Resource book, SpreadsheetStyle sstyle) throws DatabaseException {
 429         Layer0 L0 = Layer0.getInstance(graph);
 430         SpreadsheetResource SR = SpreadsheetResource.getInstance(graph);
 431         Resource style = graph.newResource();
 432         graph.claim(style, L0.InstanceOf, null, SR.Style);
 433         graph.claim(style, L0.PartOf, book);
 434
 435         int styleId = sstyle.getStyleId();
 436         String styleName = sstyle.name;
 437
 438         graph.claimLiteral(style, L0.HasName, styleName);
 439         //System.err.println("CREATING STYLE " + styleName + " WITH ID: " + styleId);
 440         graph.claimLiteral(style, SR.Style_id, styleId, Bindings.INTEGER);
 441
 442         DatatypeResource DATATYPES = DatatypeResource.getInstance(graph);
 443         if (sstyle.foreground != null)
 444             graph.claimLiteral(style, SR.Cell_foreground, DATATYPES.RGB_Integer, sstyle.foreground, RGB.Integer.BINDING);
 445         if (sstyle.background != null)
 446             graph.claimLiteral(style, SR.Cell_background, DATATYPES.RGB_Integer, sstyle.background, RGB.Integer.BINDING);
 447         if (sstyle.align != -1)
 448             graph.claimLiteral(style, SR.Cell_align, sstyle.align, Bindings.INTEGER);
 449         if (sstyle.font != null)
 450             graph.claimLiteral(style, SR.Cell_font, DATATYPES.Font, sstyle.font, Font.BINDING);
 451         if (sstyle.border != -1)
 452             graph.claimLiteral(style, SR.Cell_border, sstyle.border);
 453         if (sstyle.formatString != null && !sstyle.formatString.isEmpty())
 454             graph.claimLiteral(style, SR.Cell_formatString, sstyle.formatString, Bindings.STRING);
 455         if (sstyle.formatIndex != -1)
 456             graph.claimLiteral(style, SR.Cell_formatIndex, sstyle.formatIndex, Bindings.INTEGER);
 457
 458         return style;
 459     }
 460
 461     public static Resource createBook(WriteGraph graph, Resource parent, String name) throws DatabaseException {
 462         Layer0 L0 = Layer0.getInstance(graph);
 463         SpreadsheetResource SR = SpreadsheetResource.getInstance(graph);
 464         Resource book = graph.newResource();
 465         graph.claim(book, L0.InstanceOf, SR.Book);
 466         graph.claimLiteral(book, L0.HasName, L0.NameOf, L0.String, name, Bindings.STRING);
 467         graph.claim(parent, L0.ConsistsOf, book);
 468
 469         return book;
 470     }
 471
 472     public static Variable constructAndInitializeRunVariable(WriteGraph graph, Resource root) throws DatabaseException {
 473         Variable run = SpreadsheetUtils.getBookVariable(graph, root);
 474         SpreadsheetGraphUtils.fullSynchronization(graph, run);
 475         SpreadsheetGraphUtils.evaluateAll(graph, run);
 476         SpreadsheetGraphUtils.saveInitialCondition(graph, run, root, "Initial");
 477         return run;
 478     }
 479
 480     public static Variant extRefVariable(ReadGraph graph, Variable var) throws DatabaseException {
 481         return new Variant(Bindings.VOID, new ExternalRefVariable(graph, var));
 482     }
 483
 484     static class ExternalRefVariable implements ExternalRef {
 485
 486         final private String uri;
 487
 488         public ExternalRefVariable(ReadGraph graph, Variable variable) throws DatabaseException {
 489             this.uri = variable.getURI(graph);
 490         }
 491
 492         @Override
 493         public void listen(Object context, ExternalRefListener listener) {
 494             Simantics.getSession().asyncRequest(new UnaryRead<String, Variant>(uri) {
 495
 496                 @Override
 497                 public Variant perform(ReadGraph graph) throws DatabaseException {
 498                     Variable variable = Variables.getVariable(graph, parameter);
 499                     return variable.getVariantValue(graph);
 500                 }
 501
 502             }, new Listener<Variant>() {
 503
 504                 @Override
 505                 public void execute(Variant result) {
 506                     listener.newValue(result);
 507                 }
 508
 509                 @Override
 510                 public void exception(Throwable t) {
 511                     LOGGER.error("Error while evaluating variable value", t);
 512                 }
 513
 514                 @Override
 515                 public boolean isDisposed() {
 516                     return listener.isDisposed();
 517                 }
 518
 519             });
 520         }
 521
 522     }
 523
 524     public static Variant extRefActiveVariable(ReadGraph graph, Variable var) throws DatabaseException {
 525         return new Variant(Bindings.VOID, new ExternalRefActiveVariable(graph, var));
 526     }
 527
 528     static class ExternalRefActiveVariable implements ExternalRef {
 529
 530         final private String uri;
 531
 532         public ExternalRefActiveVariable(ReadGraph graph, Variable variable) throws DatabaseException {
 533             this.uri = variable.getURI(graph);
 534         }
 535
 536         @Override
 537         public void listen(Object context, ExternalRefListener listener) {
 538             Simantics.getSession().asyncRequest(new BinaryRead<String, String, Variant>((String)context, uri) {
 539
 540                 @Override
 541                 public Variant perform(ReadGraph graph) throws DatabaseException {
 542                     Variable contextVariable = Variables.getVariable(graph, parameter);
 543                     Variable configVariable = Variables.getVariable(graph, parameter2);
 544                     Variable activeVariable = Variables.switchPossibleContext(graph, configVariable, contextVariable.getRepresents(graph));
 545                     return activeVariable.getVariantValue(graph);
 546                 }
 547             }, new Listener<Variant>() {
 548
 549                 @Override
 550                 public void execute(Variant result) {
 551                     listener.newValue(result);
 552                 }
 553
 554                 @Override
 555                 public void exception(Throwable t) {
 556                     LOGGER.error("Error while evaluating variable value", t);
 557                 }
 558
 559                 @Override
 560                 public boolean isDisposed() {
 561                     return listener.isDisposed();
 562                 }
 563
 564             });
 565         }
 566
 567     }
 568
 569 }