Copyright (c) 2015 Google Inc and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    John Glassmyer  - import group sorting is broken - https://bugs.eclipse.org/430303
/*******************************************************************************
 * Copyright (c) 2015 Google Inc and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     John Glassmyer <jogl@google.com> - import group sorting is broken - https://bugs.eclipse.org/430303
 *******************************************************************************/
package org.eclipse.jdt.internal.core.dom.rewrite.imports;

import java.util.Comparator;

import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.core.Signature;
import org.eclipse.jdt.internal.core.JavaProject;

Sorts imports according to a lexicographic comparison of their containing package names.

This requires use of the JavaProject to look up packages and/or types by name in order to
distinguish segments of the import's container name as containing package name vs. containing
type name.
 The alternative is PackageAndContainingTypeImportComparator. See https://bugs.eclipse.org/194358. /**
 * Sorts imports according to a lexicographic comparison of their containing package names.
 * <p>
 * This requires use of the JavaProject to look up packages and/or types by name in order to
 * distinguish segments of the import's container name as containing package name vs. containing
 * type name.
 * <p>
 * The alternative is {@link PackageAndContainingTypeImportComparator}. See
 * https://bugs.eclipse.org/194358.
 */
final class PackageImportComparator implements Comparator<ImportName> {
	private final JavaProject javaProject;

	PackageImportComparator(JavaProject javaProject) {
		this.javaProject = javaProject;
	}

	@Override
	public int compare(ImportName o1, ImportName o2) {
		return determinePackageName(o1).compareTo(determinePackageName(o2));
	}

	private String determinePackageName(ImportName importName) {
		String containerName = importName.containerName;

		try {
			// Loop from longest to shortest prefix (of dot-separated name segments) of the
			// container name until a package name is found.
			String containerNamePrefix = containerName;
			while (true) {
				// Try to find a package named with this prefix.
				if (this.javaProject.findPackageFragment(containerNamePrefix) != null) {
					return containerNamePrefix;
				}

				int lastSegmentStart = containerNamePrefix.lastIndexOf(Signature.C_DOT) + 1;

				// Use the heuristic that a prefix whose last segment starts with a lowercase letter
				// is a package name, if we don't recognize the prefix as the name of a type.
				if (this.javaProject.findType(containerNamePrefix) == null) {
					if (Character.isLowerCase(containerNamePrefix.charAt(lastSegmentStart))) {
						return containerNamePrefix;
					}
				}

				if (lastSegmentStart == 0) {
					// No prefix of containerName could be resolved to a package name.
					break;
				}

				containerNamePrefix = containerNamePrefix.substring(0, lastSegmentStart - 1);
			}
		} catch (JavaModelException e) {
			// An error occurred when we asked the JavaProject to resolve a name,
			// so there is no point in proceeding with the loop.
		}

		return containerName;
	}
}