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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package sun.security.jca;

import java.util.*;

import java.security.*;

import java.security.Provider.Service;

/**

 * List of Providers. Used to represent the provider preferences.

 *

 * The system starts out with a ProviderList that only has the classNames

 * of the Providers. Providers are loaded on demand only when needed.

 *

 * For compatibility reasons, Providers that could not be loaded are ignored

 * and internally presented as the instance EMPTY_PROVIDER. However, those

 * objects cannot be presented to applications. Call the convert() method

 * to force all Providers to be loaded and to obtain a ProviderList with

 * invalid entries removed. All this is handled by the Security class.

 *

 * Note that all indices used by this class are 0-based per general Java

 * convention. These must be converted to the 1-based indices used by the

 * Security class externally when needed.

 *

 * Instances of this class are immutable. This eliminates the need for

 * cloning and synchronization in consumers. The add() and remove() style

 * methods are static in order to avoid confusion about the immutability.

 *

 * @author  Andreas Sterbenz

 * @since   1.5

 */

public final class ProviderList {

    final static sun.security.util.Debug debug =

        sun.security.util.Debug.getInstance("jca", "ProviderList");

    private final static ProviderConfig[] PC0 = new ProviderConfig[0];

    private final static Provider[] P0 = new Provider[0];

    // constant for an ProviderList with no elements

    static final ProviderList EMPTY = new ProviderList(PC0, true);

    // dummy provider object to use during initialization

    // used to avoid explicit null checks in various places

    private static final Provider EMPTY_PROVIDER =

        new Provider("##Empty##", 1.0d, "initialization in progress") {

            private static final long serialVersionUID = 1151354171352296389L;

            // override getService() to return null slightly faster

            public Service getService(String type, String algorithm) {

                return null;

            }

        };

    // construct a ProviderList from the security properties

    // (static provider configuration in the java.security file)

    static ProviderList fromSecurityProperties() {

        // doPrivileged() because of Security.getProperty()

        return AccessController.doPrivileged(

                        new PrivilegedAction<ProviderList>() {

            public ProviderList run() {

                return new ProviderList();

            }

        });

    }

    public static ProviderList add(ProviderList providerList, Provider p) {

        return insertAt(providerList, p, -1);

    }

    public static ProviderList insertAt(ProviderList providerList, Provider p,

            int position) {

        if (providerList.getProvider(p.getName()) != null) {

            return providerList;

        }

        List<ProviderConfig> list = new ArrayList<>

                                    (Arrays.asList(providerList.configs));

        int n = list.size();

        if ((position < 0) || (position > n)) {

            position = n;

        }

        list.add(position, new ProviderConfig(p));

        return new ProviderList(list.toArray(PC0), true);

    }

    public static ProviderList remove(ProviderList providerList, String name) {

        // make sure provider exists

        if (providerList.getProvider(name) == null) {

            return providerList;

        }

        // copy all except matching to new list

        ProviderConfig[] configs = new ProviderConfig[providerList.size() - 1];

        int j = 0;

        for (ProviderConfig config : providerList.configs) {

            if (config.getProvider().getName().equals(name) == false) {

                configs[j++] = config;

            }

        }

        return new ProviderList(configs, true);

    }

    // Create a new ProviderList from the specified Providers.

    // This method is for use by SunJSSE.

    public static ProviderList newList(Provider ... providers) {

        ProviderConfig[] configs = new ProviderConfig[providers.length];

        for (int i = 0; i < providers.length; i++) {

            configs[i] = new ProviderConfig(providers[i]);

        }

        return new ProviderList(configs, true);

    }

    // configuration of the providers

    private final ProviderConfig[] configs;

    // flag indicating whether all configs have been loaded successfully

    private volatile boolean allLoaded;

    // List returned by providers()

    private final List<Provider> userList = new AbstractList<Provider>() {

        public int size() {

            return configs.length;

        }

        public Provider get(int index) {

            return getProvider(index);

        }

    };

    /**

     * Create a new ProviderList from an array of configs

     */

    private ProviderList(ProviderConfig[] configs, boolean allLoaded) {

        this.configs = configs;

        this.allLoaded = allLoaded;

    }

    /**

     * Return a new ProviderList parsed from the java.security Properties.

     */

    private ProviderList() {

        List<ProviderConfig> configList = new ArrayList<>();

        for (int i = 1; true; i++) {

            String entry = Security.getProperty("security.provider." + i);

            if (entry == null) {

                break;

            }

            entry = entry.trim();

            if (entry.length() == 0) {

                System.err.println("invalid entry for " +

                                   "security.provider." + i);

                break;

            }

            int k = entry.indexOf(' ');

            ProviderConfig config;

            if (k == -1) {

                config = new ProviderConfig(entry);

            } else {

                String argument = entry.substring(k + 1).trim();

            }

            // Get rid of duplicate providers.

            if (configList.contains(config) == false) {

                configList.add(config);

            }

        }

        configs = configList.toArray(PC0);

        if (debug != null) {

            debug.println("provider configuration: " + configList);

        }

    }

    /**

     * Construct a special ProviderList for JAR verification. It consists

     * of the providers specified via jarClassNames, which must be on the

     * bootclasspath and cannot be in signed JAR files. This is to avoid

     * possible recursion and deadlock during verification.

     */

        List<ProviderConfig> newConfigs = new ArrayList<>();

            for (ProviderConfig config : configs) {

                // if the equivalent object is present in this provider list,

                // use the old object rather than the new object.

                // this ensures that when the provider is loaded in the

                // new thread local list, it will also become available

                // in this provider list

                if (config.equals(newConfig)) {

                    newConfig = config;

                    break;

                }

            }

            newConfigs.add(newConfig);

        }

        ProviderConfig[] configArray = newConfigs.toArray(PC0);

        return new ProviderList(configArray, false);

    }

    public int size() {

        return configs.length;

    }

    /**

     * Return the Provider at the specified index. Returns EMPTY_PROVIDER

     * if the provider could not be loaded at this time.

     */

    Provider getProvider(int index) {

        Provider p = configs[index].getProvider();

        return (p != null) ? p : EMPTY_PROVIDER;

    }

    /**

     * Return an unmodifiable List of all Providers in this List. The

     * individual Providers are loaded on demand. Elements that could not

     * be initialized are replaced with EMPTY_PROVIDER.

     */

    public List<Provider> providers() {

        return userList;

    }

    private ProviderConfig getProviderConfig(String name) {

        int index = getIndex(name);

        return (index != -1) ? configs[index] : null;

    }

    // return the Provider with the specified name or null

    public Provider getProvider(String name) {

        ProviderConfig config = getProviderConfig(name);

        return (config == null) ? null : config.getProvider();

    }

    /**

     * Return the index at which the provider with the specified name is

     * installed or -1 if it is not present in this ProviderList.

     */

    public int getIndex(String name) {

        for (int i = 0; i < configs.length; i++) {

            Provider p = getProvider(i);

            if (p.getName().equals(name)) {

                return i;

            }

        }

        return -1;

    }

    // attempt to load all Providers not already loaded

    private int loadAll() {

        if (allLoaded) {

            return configs.length;

        }

        if (debug != null) {

            debug.println("Loading all providers");

            new Exception("Call trace").printStackTrace();

        }

        int n = 0;

        for (int i = 0; i < configs.length; i++) {

            Provider p = configs[i].getProvider();

            if (p != null) {

                n++;

            }

        }

        if (n == configs.length) {

            allLoaded = true;

        }

        return n;

    }

    /**

     * Try to load all Providers and return the ProviderList. If one or

     * more Providers could not be loaded, a new ProviderList with those

     * entries removed is returned. Otherwise, the method returns this.

     */

    ProviderList removeInvalid() {

        int n = loadAll();

        if (n == configs.length) {

            return this;

        }

        ProviderConfig[] newConfigs = new ProviderConfig[n];

        for (int i = 0, j = 0; i < configs.length; i++) {

            ProviderConfig config = configs[i];

            if (config.isLoaded()) {

                newConfigs[j++] = config;

            }

        }

        return new ProviderList(newConfigs, true);

    }

    // return the providers as an array

    public Provider[] toArray() {

        return providers().toArray(P0);

    }

    // return a String representation of this ProviderList

    public String toString() {

        return Arrays.asList(configs).toString();

    }

    /**

     * Return a Service describing an implementation of the specified

     * algorithm from the Provider with the highest precedence that

     * supports that algorithm. Return null if no Provider supports this

     * algorithm.

     */

    public Service getService(String type, String name) {

        for (int i = 0; i < configs.length; i++) {

            Provider p = getProvider(i);

            Service s = p.getService(type, name);

            if (s != null) {

                return s;

            }

        }

        return null;

    }

    /**

     * Return a List containing all the Services describing implementations

     * of the specified algorithms in precedence order. If no implementation

     * exists, this method returns an empty List.

     *

     * The elements of this list are determined lazily on demand.

     *

     * The List returned is NOT thread safe.

     */

    public List<Service> getServices(String type, String algorithm) {

        return new ServiceList(type, algorithm);

    }

    /**

     * This method exists for compatibility with JCE only. It will be removed

     * once JCE has been changed to use the replacement method.

     * @deprecated use {@code getServices(List<ServiceId>)} instead

     */

    @Deprecated

    public List<Service> getServices(String type, List<String> algorithms) {

        List<ServiceId> ids = new ArrayList<>();

        for (String alg : algorithms) {

            ids.add(new ServiceId(type, alg));

        }

        return getServices(ids);

    }

    public List<Service> getServices(List<ServiceId> ids) {

        return new ServiceList(ids);

    }

    /**

     * Inner class for a List of Services. Custom List implementation in

     * order to delay Provider initialization and lookup.

     * Not thread safe.

     */

    private final class ServiceList extends AbstractList<Service> {

        // type and algorithm for simple lookup

        // avoid allocating/traversing the ServiceId list for these lookups

        private final String type;

        private final String algorithm;

        // list of ids for parallel lookup

        // if ids is non-null, type and algorithm are null

        private final List<ServiceId> ids;

        // first service we have found

        // it is stored in a separate variable so that we can avoid

        // allocating the services list if we do not need the second service.

        // this is the case if we don't failover (failovers are typically rare)

        private Service firstService;

        // list of the services we have found so far

        private List<Service> services;

        // index into config[] of the next provider we need to query

        private int providerIndex;

        ServiceList(String type, String algorithm) {

            this.type = type;

            this.algorithm = algorithm;

            this.ids = null;

        }

        ServiceList(List<ServiceId> ids) {

            this.type = null;

            this.algorithm = null;

            this.ids = ids;

        }

        private void addService(Service s) {

            if (firstService == null) {

                firstService = s;

            } else {

                if (services == null) {

                    services = new ArrayList<Service>(4);

                    services.add(firstService);

                }

                services.add(s);

            }

        }

        private Service tryGet(int index) {

            while (true) {

                if ((index == 0) && (firstService != null)) {

                    return firstService;

                } else if ((services != null) && (services.size() > index)) {

                    return services.get(index);

                }

                if (providerIndex >= configs.length) {

                    return null;

                }

                // check all algorithms in this provider before moving on

                Provider p = getProvider(providerIndex++);

                if (type != null) {

                    // simple lookup

                    Service s = p.getService(type, algorithm);

                    if (s != null) {

                        addService(s);

                    }

                } else {

                    // parallel lookup

                    for (ServiceId id : ids) {

                        Service s = p.getService(id.type, id.algorithm);

                        if (s != null) {

                            addService(s);

                        }

                    }

                }

            }

        }

        public Service get(int index) {

            Service s = tryGet(index);

            if (s == null) {

                throw new IndexOutOfBoundsException();

            }

            return s;

        }

        public int size() {

            int n;

            if (services != null) {

                n = services.size();

            } else {

                n = (firstService != null) ? 1 : 0;

            }

            while (tryGet(n) != null) {

                n++;

            }

            return n;

        }

        // override isEmpty() and iterator() to not call size()

        // this avoids loading + checking all Providers

        public boolean isEmpty() {

            return (tryGet(0) == null);

        }

        public Iterator<Service> iterator() {

            return new Iterator<Service>() {

                int index;

                public boolean hasNext() {

                    return tryGet(index) != null;

                }

                public Service next() {

                    Service s = tryGet(index);

                    if (s == null) {

                        throw new NoSuchElementException();

                    }

                    index++;

                    return s;

                }

                public void remove() {

                    throw new UnsupportedOperationException();

                }

            };

        }

    }

}