package org.javacs;

import com.sun.source.tree.*;

import com.sun.source.util.*;

import java.util.Optional;

class FindCursor {

public static Optional<TreePath> find(

JavacTask task, CompilationUnitTree source, int line, int column) {

SourcePositions sourcePositions = Trees.instance(task).getSourcePositions();

long offset = source.getLineMap().getPosition(line, column);

class Finished extends RuntimeException {

final TreePath found;

Finished(TreePath of) {

found = of;

}

}

class Search extends TreePathScanner<Void, Void> {

@Override

public Void scan(Tree leaf, Void nothing) {

if (containsCursor(leaf)) {

super.scan(leaf, nothing);

throw new Finished(new TreePath(getCurrentPath(), leaf));

} else return null;

}

boolean containsCursor(Tree leaf) {

long start = sourcePositions.getStartPosition(source, leaf);

long end = sourcePositions.getEndPosition(source, leaf);

return start <= offset && offset <= end;

}

@Override

public Void visitErroneous(ErroneousTree node, Void nothing) {

return super.scan(node.getErrorTrees(), nothing);

}

}

try {

new Search().scan(source, null);

return Optional.empty();

} catch (Finished found) {

return Optional.of(found.found);

}

}

}