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Computes the AST difference between two Spoon abstract syntax trees using the Gumtree algorithm.
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package gumtree.spoon;

import java.io.File;

import gumtree.spoon.builder.SpoonGumTreeBuilder;
import gumtree.spoon.diff.Diff;
import gumtree.spoon.diff.DiffImpl;
import spoon.SpoonModelBuilder;
import spoon.compiler.SpoonResource;
import spoon.compiler.SpoonResourceHelper;
import spoon.reflect.declaration.CtElement;
import spoon.reflect.declaration.CtType;
import spoon.reflect.factory.Factory;
import spoon.reflect.factory.FactoryImpl;
import spoon.support.DefaultCoreFactory;
import spoon.support.StandardEnvironment;
import spoon.support.compiler.VirtualFile;
import spoon.support.compiler.jdt.JDTBasedSpoonCompiler;

/**
 * Computes the differences between two CtElements.
 *
 * @author Matias Martinez, [email protected]
 */
public class AstComparator {
	// For the moment, let's create a factory each type we get a type.
	// Sharing the factory produces a bug when asking the path of different types
	// (>1)
	// private final Factory factory;

	static {
		// default 0.3
		// it seems that default value is really bad
		// 0.1 one failing much more changes
		// 0.2 one failing much more changes
		// 0.3 one failing test_t_224542
		// 0.4 fails for issue31
		// 0.5 fails for issue31
		// 0.6 OK
		// 0.7 1 failing
		// 0.8 2 failing
		// 0.9 two failing tests with more changes
		// see GreedyBottomUpMatcher.java in Gumtree
		System.setProperty("gumtree.match.bu.sim", "0.6");

		// default 2
		// 0 is really bad for 211903 t_224542 225391 226622
		// 1 is required for t_225262 and t_213712 to pass
		System.setProperty("gumtree.match.gt.minh", "1");

		// default 1000
		// 0 fails
		// 1 fails
		// 10 fails
		// 100 OK
		// 1000 OK
		// see AbstractBottomUpMatcher#SIZE_THRESHOD in Gumtree
		// System.setProperty("gumtree.match.bu.size","10");
		// System.setProperty("gt.bum.szt", "1000");
	}

	public AstComparator() {
		super();
	}

	protected Factory createFactory() {
		Factory factory = new FactoryImpl(new DefaultCoreFactory(), new StandardEnvironment());
		factory.getEnvironment().setNoClasspath(true);
		factory.getEnvironment().setCommentEnabled(false);
		return factory;
	}

	/**
	 * compares two java files
	 */
	public Diff compare(File f1, File f2) throws Exception {
		return this.compare(getCtType(f1), getCtType(f2));
	}

	/**
	 * compares two snippet
	 */
	public Diff compare(String left, String right) {
		return compare(getCtType(left), getCtType(right));
	}

	/**
	 * compares two AST nodes
	 */
	public Diff compare(CtElement left, CtElement right) {
		final SpoonGumTreeBuilder scanner = new SpoonGumTreeBuilder();
		return new DiffImpl(scanner.getTreeContext(), scanner.getTree(left), scanner.getTree(right));
	}

	public CtType getCtType(File file) throws Exception {

		SpoonResource resource = SpoonResourceHelper.createResource(file);
		return getCtType(resource);
	}

	public CtType getCtType(SpoonResource resource) {
		Factory factory = createFactory();
		factory.getModel().setBuildModelIsFinished(false);
		SpoonModelBuilder compiler = new JDTBasedSpoonCompiler(factory);
		compiler.getFactory().getEnvironment().setLevel("OFF");
		compiler.addInputSource(resource);
		compiler.build();

		if (factory.Type().getAll().size() == 0) {
			return null;
		}

		// let's first take the first type.
		CtType type = factory.Type().getAll().get(0);
		// Now, let's ask to the factory the type (which it will set up the
		// corresponding
		// package)
		return factory.Type().get(type.getQualifiedName());
	}

	public CtType getCtType(String content) {
		VirtualFile resource = new VirtualFile(content, "/test");
		return getCtType(resource);
	}

	public static void main(String[] args) throws Exception {
		if (args.length != 2) {
			System.out.println("Usage: DiffSpoon   ");
			return;
		}

		final Diff result = new AstComparator().compare(new File(args[0]), new File(args[1]));
		System.out.println(result.toString());
	}
}