Copyright (c) 2008, 2017 IBM Corporation 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:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2008, 2017 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.osgi.internal.permadmin;

import java.io.File;
import java.lang.reflect.Constructor;
import java.security.AccessController;
import java.security.AllPermission;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import org.osgi.service.permissionadmin.PermissionInfo;

public final class PermissionInfoCollection extends PermissionCollection {
	private static final long serialVersionUID = 3140511562980923957L;
	/* Used to find permission constructors in addPermissions */
	static private final Class<?> twoStringClassArray[] = new Class[] {String.class, String.class};
	static private final Class<?> oneStringClassArray[] = new Class[] {String.class};
	static private final Class<?> noArgClassArray[] = new Class[] {};
	static private final Class<?>[][] permClassArrayArgs = new Class[][] {noArgClassArray, oneStringClassArray, twoStringClassArray};

	/* @GuardedBy(cachedPermisssionCollections) */
	private final Map<Class<? extends Permission>, PermissionCollection> cachedPermissionCollections = new HashMap<>();
	private final boolean hasAllPermission;
	private final PermissionInfo[] permInfos;

	public PermissionInfoCollection(PermissionInfo[] permInfos) {
		this.permInfos = permInfos;
		boolean tempAllPermissions = false;
		for (int i = 0; i < permInfos.length && !tempAllPermissions; i++)
			if (permInfos[i].getType().equals(AllPermission.class.getName()))
				tempAllPermissions = true;
		this.hasAllPermission = tempAllPermissions;
		setReadOnly(); // collections are managed with ConditionalPermissionAdmin
	}

	@Override
	public void add(Permission arg0) {
		throw new SecurityException();
	}

	@Override
	public Enumeration<Permission> elements() {
		// TODO return an empty enumeration for now; 
		return BundlePermissions.EMPTY_ENUMERATION;
	}

	@Override
	public boolean implies(Permission perm) {
		if (hasAllPermission)
			return true;
		final Class<? extends Permission> permClass = perm.getClass();
		PermissionCollection collection;
		synchronized (cachedPermissionCollections) {
			collection = cachedPermissionCollections.get(permClass);
		}
		// must populate the collection outside of the lock to prevent class loader deadlock
		if (collection == null) {
			collection = perm.newPermissionCollection();
			if (collection == null) {
				collection = new PermissionsHash();
			}
			try {
				final PermissionCollection targetCollection = collection;
				AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
					@Override
					public Object run() throws Exception {
						addPermissions(targetCollection, permClass);
						return null;
					}

				});

			} catch (Exception e) {
				if (e instanceof PrivilegedActionException) {
					e = ((PrivilegedActionException) e).getException();
				}
				throw new SecurityException("Exception creating permissions: " + permClass + ": " + e.getMessage(), e); //$NON-NLS-1$ //$NON-NLS-2$
			}
			synchronized (cachedPermissionCollections) {
				// check to see if another thread beat this thread at adding the collection
				PermissionCollection exists = cachedPermissionCollections.get(permClass);
				if (exists != null)
					collection = exists;
				else
					cachedPermissionCollections.put(permClass, collection);
			}
		}
		return collection.implies(perm);
	}

	PermissionInfo[] getPermissionInfos() {
		return permInfos;
	}

	void addPermissions(PermissionCollection collection, Class<? extends Permission> permClass) throws Exception {
		String permClassName = permClass.getName();
		Constructor<? extends Permission> constructor = null;
		int numArgs = -1;
		for (int i = permClassArrayArgs.length - 1; i >= 0; i--) {
			try {
				constructor = permClass.getConstructor(permClassArrayArgs[i]);
				numArgs = i;
				break;
			} catch (NoSuchMethodException e) {
				// ignore
			}
		}
		if (constructor == null)
			throw new NoSuchMethodException(permClass.getName() + ".<init>()"); //$NON-NLS-1$
		/*
		 * TODO: We need to cache the permission constructors to enhance performance (see bug 118813).
		 */
		for (PermissionInfo permInfo : permInfos) {
			if (permInfo.getType().equals(permClassName)) {
				String args[] = new String[numArgs];
				if (numArgs > 0) {
					args[0] = permInfo.getName();
				}
				if (numArgs > 1) {
					args[1] = permInfo.getActions();
				}
				if (permInfo.getType().equals("java.io.FilePermission")) { //$NON-NLS-1$
					// map FilePermissions for relative names to the bundle's data area
					if (!args[0].equals("<<ALL FILES>>")) { //$NON-NLS-1$
						File file = new File(args[0]);
						if (!file.isAbsolute()) { // relative name
							// TODO need to figure out how to do relative FilePermissions from the dataFile
							continue;
						}
					}
				}
				collection.add(constructor.newInstance((Object[]) args));
			}
		}
	}

	void clearPermissionCache() {
		synchronized (cachedPermissionCollections) {
			cachedPermissionCollections.clear();
		}
	}
}