/*
 * Copyright 2003 Sun Microsystems, Inc.  All Rights Reserved.
 * 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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package sun.rmi.rmic.newrmic.jrmp;

import com.sun.javadoc.ClassDoc;
import com.sun.javadoc.MethodDoc;
import com.sun.javadoc.Parameter;
import com.sun.javadoc.Type;
import java.io.IOException;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.security.MessageDigest;
import java.security.DigestOutputStream;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.HashMap;
import java.util.Map;
import sun.rmi.rmic.newrmic.BatchEnvironment;

import static sun.rmi.rmic.newrmic.Constants.*;
import static sun.rmi.rmic.newrmic.jrmp.Constants.*;

/**
 * Encapsulates RMI-specific information about a remote implementation
 * class (a class that implements one or more remote interfaces).
 *
 * WARNING: The contents of this source file are not part of any
 * supported API.  Code that depends on them does so at its own risk:
 * they are subject to change or removal without notice.
 *
 * @author Peter Jones
 **/
final class RemoteClass {

    /** rmic environment for this object */
    private final BatchEnvironment env;

    /** the remote implementation class this object represents */
    private final ClassDoc implClass;

    /** remote interfaces implemented by this class */
    private ClassDoc[] remoteInterfaces;

    /** the remote methods of this class */
    private Method[] remoteMethods;

    /** stub/skeleton "interface hash" for this class */
    private long interfaceHash;

    /**
     * Creates a RemoteClass instance that represents the RMI-specific
     * information about the specified remote implementation class.
     *
     * If the class is not a valid remote implementation class or if
     * some other error occurs, the return value will be null, and
     * errors will have been reported to the supplied
     * BatchEnvironment.
     **/
    static RemoteClass forClass(BatchEnvironment env, ClassDoc implClass) {
        RemoteClass remoteClass = new RemoteClass(env, implClass);
        if (remoteClass.init()) {
            return remoteClass;
        } else {
            return null;
        }
    }

    /**
     * Creates a RemoteClass instance for the specified class.  The
     * resulting object is not yet initialized.
     **/
    private RemoteClass(BatchEnvironment env, ClassDoc implClass) {
        this.env = env;
        this.implClass = implClass;
    }

    /**
     * Returns the ClassDoc for this remote implementation class.
     **/
    ClassDoc classDoc() {
        return implClass;
    }

    /**
     * Returns the remote interfaces implemented by this remote
     * implementation class.
     *
     * A remote interface is an interface that is a subinterface of
     * java.rmi.Remote.  The remote interfaces of a class are the
     * direct superinterfaces of the class and all of its superclasses
     * that are remote interfaces.
     *
     * The order of the array returned is arbitrary, and some elements
     * may be superfluous (i.e., superinterfaces of other interfaces
     * in the array).
     **/
    ClassDoc[] remoteInterfaces() {
        return (ClassDoc[]) remoteInterfaces.clone();
    }

    /**
     * Returns an array of RemoteClass.Method objects representing all
     * of the remote methods of this remote implementation class (all
     * of the member methods of the class's remote interfaces).
     *
     * The methods in the array are ordered according to a comparison
     * of strings consisting of their name followed by their
     * descriptor, so each method's index in the array corresponds to
     * its "operation number" in the JDK 1.1 version of the JRMP
     * stub/skeleton protocol.
     **/
    Method[] remoteMethods() {
        return (Method[]) remoteMethods.clone();
    }

    /**
     * Returns the "interface hash" used to match a stub/skeleton pair
     * for this remote implementation class in the JDK 1.1 version of
     * the JRMP stub/skeleton protocol.
     **/
    long interfaceHash() {
        return interfaceHash;
    }

    /**
     * Validates this remote implementation class and computes the
     * RMI-specific information.  Returns true if successful, or false
     * if an error occurred.
     **/
    private boolean init() {
        /*
         * Verify that it is really a class, not an interface.
         */
        if (implClass.isInterface()) {
            env.error("rmic.cant.make.stubs.for.interface",
                      implClass.qualifiedName());
            return false;
        }

        /*
         * Find all of the remote interfaces of our remote
         * implementation class-- for each class up the superclass
         * chain, add each directly-implemented interface that somehow
         * extends Remote to a list.
         */
        List<ClassDoc> remotesImplemented = new ArrayList<ClassDoc>();
        for (ClassDoc cl = implClass; cl != null; cl = cl.superclass()) {
            for (ClassDoc intf : cl.interfaces()) {
                /*
                 * Add interface to the list if it extends Remote and
                 * it is not already there.
                 */
                if (!remotesImplemented.contains(intf) &&
                    intf.subclassOf(env.docRemote()))
                {
                    remotesImplemented.add(intf);
                    if (env.verbose()) {
                        env.output("[found remote interface: " +
                                   intf.qualifiedName() + "]");
                    }
                }
            }

            /*
             * Verify that the candidate remote implementation class
             * implements at least one remote interface directly.
             */
            if (cl == implClass && remotesImplemented.isEmpty()) {
                if (implClass.subclassOf(env.docRemote())) {
                    /*
                     * This error message is used if the class does
                     * implement a remote interface through one of its
                     * superclasses, but not directly.
                     */
                    env.error("rmic.must.implement.remote.directly",
                              implClass.qualifiedName());
                } else {
                    /*
                     * This error message is used if the class does
                     * not implement a remote interface at all.
                     */
                    env.error("rmic.must.implement.remote",
                              implClass.qualifiedName());
                }
                return false;
            }
        }

        /*
         * Convert list of remote interfaces to an array
         * (order is not important for this array).
         */
        remoteInterfaces =
            remotesImplemented.toArray(
                new ClassDoc[remotesImplemented.size()]);

        /*
         * Collect the methods from all of the remote interfaces into
         * a table, which maps from method name-and-descriptor string
         * to Method object.
         */
        Map<String,Method> methods = new HashMap<String,Method>();
        boolean errors = false;
        for (ClassDoc intf : remotesImplemented) {
            if (!collectRemoteMethods(intf, methods)) {
                /*
                 * Continue iterating despite errors in order to
                 * generate more complete error report.
                 */
                errors = true;
            }
        }
        if (errors) {
            return false;
        }

        /*
         * Sort table of remote methods into an array.  The elements
         * are sorted in ascending order of the string of the method's
         * name and descriptor, so that each elements index is equal
         * to its operation number in the JDK 1.1 version of the JRMP
         * stub/skeleton protocol.
         */
        String[] orderedKeys =
            methods.keySet().toArray(new String[methods.size()]);
        Arrays.sort(orderedKeys);
        remoteMethods = new Method[methods.size()];
        for (int i = 0; i < remoteMethods.length; i++) {
            remoteMethods[i] = methods.get(orderedKeys[i]);
            if (env.verbose()) {
                String msg = "[found remote method <" + i + ">: " +
                    remoteMethods[i].operationString();
                ClassDoc[] exceptions = remoteMethods[i].exceptionTypes();
                if (exceptions.length > 0) {
                    msg += " throws ";
                    for (int j = 0; j < exceptions.length; j++) {
                        if (j > 0) {
                            msg += ", ";
                        }
                        msg +=  exceptions[j].qualifiedName();
                    }
                }
                msg += "\n\tname and descriptor = \"" +
                    remoteMethods[i].nameAndDescriptor();
                msg += "\n\tmethod hash = " +
                    remoteMethods[i].methodHash() + "]";
                env.output(msg);
            }
        }

        /*
         * Finally, pre-compute the interface hash to be used by
         * stubs/skeletons for this remote class in the JDK 1.1
         * version of the JRMP stub/skeleton protocol.
         */
        interfaceHash = computeInterfaceHash();

        return true;
    }

    /**
     * Collects and validates all methods from the specified interface
     * and all of its superinterfaces as remote methods.  Remote
     * methods are added to the supplied table.  Returns true if
     * successful, or false if an error occurred.
     **/
    private boolean collectRemoteMethods(ClassDoc intf,
                                         Map<String,Method> table)
    {
        if (!intf.isInterface()) {
            throw new AssertionError(
                intf.qualifiedName() + " not an interface");
        }

        boolean errors = false;

        /*
         * Search interface's declared methods.
         */
    nextMethod:
        for (MethodDoc method : intf.methods()) {

            /*
             * Verify that each method throws RemoteException (or a
             * superclass of RemoteException).
             */
            boolean hasRemoteException = false;
            for (ClassDoc ex : method.thrownExceptions()) {
                if (env.docRemoteException().subclassOf(ex)) {
                    hasRemoteException = true;
                    break;
                }
            }

            /*
             * If this method did not throw RemoteException as required,
             * generate the error but continue, so that multiple such
             * errors can be reported.
             */
            if (!hasRemoteException) {
                env.error("rmic.must.throw.remoteexception",
                          intf.qualifiedName(),
                          method.name() + method.signature());
                errors = true;
                continue nextMethod;
            }

            /*
             * Verify that the implementation of this method throws only
             * java.lang.Exception or its subclasses (fix bugid 4092486).
             * JRMP does not support remote methods throwing
             * java.lang.Throwable or other subclasses.
             */
            MethodDoc implMethod = findImplMethod(method);
            if (implMethod != null) {           // should not be null
                for (ClassDoc ex : implMethod.thrownExceptions()) {
                    if (!ex.subclassOf(env.docException())) {
                        env.error("rmic.must.only.throw.exception",
                                  implMethod.name() + implMethod.signature(),
                                  ex.qualifiedName());
                        errors = true;
                        continue nextMethod;
                    }
                }
            }

            /*
             * Create RemoteClass.Method object to represent this method
             * found in a remote interface.
             */
            Method newMethod = new Method(method);

            /*
             * Store remote method's representation in the table of
             * remote methods found, keyed by its name and descriptor.
             *
             * If the table already contains an entry with the same
             * method name and descriptor, then we must replace the
             * old entry with a Method object that represents a legal
             * combination of the old and the new methods;
             * specifically, the combined method must have a throws
             * clause that contains (only) all of the checked
             * exceptions that can be thrown by both the old and the
             * new method (see bugid 4070653).
             */
            String key = newMethod.nameAndDescriptor();
            Method oldMethod = table.get(key);
            if (oldMethod != null) {
                newMethod = newMethod.mergeWith(oldMethod);
            }
            table.put(key, newMethod);
        }

        /*
         * Recursively collect methods for all superinterfaces.
         */
        for (ClassDoc superintf : intf.interfaces()) {
            if (!collectRemoteMethods(superintf, table)) {
                errors = true;
            }
        }

        return !errors;
    }

    /**
     * Returns the MethodDoc for the method of this remote
     * implementation class that implements the specified remote
     * method of a remote interface.  Returns null if no matching
     * method was found in this remote implementation class.
     **/
    private MethodDoc findImplMethod(MethodDoc interfaceMethod) {
        String name = interfaceMethod.name();
        String desc = Util.methodDescriptorOf(interfaceMethod);
        for (MethodDoc implMethod : implClass.methods()) {
            if (name.equals(implMethod.name()) &&
                desc.equals(Util.methodDescriptorOf(implMethod)))
            {
                return implMethod;
            }
        }
        return null;
    }

    /**
     * Computes the "interface hash" of the stub/skeleton pair for
     * this remote implementation class.  This is the 64-bit value
     * used to enforce compatibility between a stub class and a
     * skeleton class in the JDK 1.1 version of the JRMP stub/skeleton
     * protocol.
     *
     * It is calculated using the first 64 bits of an SHA digest.  The
     * digest is of a stream consisting of the following data:
     *     (int) stub version number, always 1
     *     for each remote method, in order of operation number:
     *         (UTF-8) method name
     *         (UTF-8) method descriptor
     *         for each declared exception, in alphabetical name order:
     *             (UTF-8) name of exception class
     * (where "UTF-8" includes a 16-bit length prefix as written by
     * java.io.DataOutput.writeUTF).
     **/
    private long computeInterfaceHash() {
        long hash = 0;
        ByteArrayOutputStream sink = new ByteArrayOutputStream(512);
        try {
            MessageDigest md = MessageDigest.getInstance("SHA");
            DataOutputStream out = new DataOutputStream(
                new DigestOutputStream(sink, md));

            out.writeInt(INTERFACE_HASH_STUB_VERSION);

            for (Method method : remoteMethods) {
                MethodDoc methodDoc = method.methodDoc();

                out.writeUTF(methodDoc.name());
                out.writeUTF(Util.methodDescriptorOf(methodDoc));
                                // descriptors already use binary names

                ClassDoc exceptions[] = methodDoc.thrownExceptions();
                Arrays.sort(exceptions, new ClassDocComparator());
                for (ClassDoc ex : exceptions) {
                    out.writeUTF(Util.binaryNameOf(ex));
                }
            }
            out.flush();

            // use only the first 64 bits of the digest for the hash
            byte hashArray[] = md.digest();
            for (int i = 0; i < Math.min(8, hashArray.length); i++) {
                hash += ((long) (hashArray[i] & 0xFF)) << (i * 8);
            }
        } catch (IOException e) {
            throw new AssertionError(e);
        } catch (NoSuchAlgorithmException e) {
            throw new AssertionError(e);
        }

        return hash;
    }

    /**
     * Compares ClassDoc instances according to the lexicographic
     * order of their binary names.
     **/
    private static class ClassDocComparator implements Comparator<ClassDoc> {
        public int compare(ClassDoc o1, ClassDoc o2) {
            return Util.binaryNameOf(o1).compareTo(Util.binaryNameOf(o2));
        }
    }

    /**
     * Encapsulates RMI-specific information about a particular remote
     * method in the remote implementation class represented by the
     * enclosing RemoteClass.
     **/
    final class Method implements Cloneable {

        /**
         * MethodDoc for this remove method, from one of the remote
         * interfaces that this method was found in.
         *
         * Note that this MethodDoc may be only one of multiple that
         * correspond to this remote method object, if multiple of
         * this class's remote interfaces contain methods with the
         * same name and descriptor.  Therefore, this MethodDoc may
         * declare more exceptions thrown that this remote method
         * does.
         **/
        private final MethodDoc methodDoc;

        /** java.rmi.server.Operation string for this remote method */
        private final String operationString;

        /** name and descriptor of this remote method */
        private final String nameAndDescriptor;

        /** JRMP "method hash" for this remote method */
        private final long methodHash;

        /**
         * Exceptions declared to be thrown by this remote method.
         *
         * This list may include superfluous entries, such as
         * unchecked exceptions and subclasses of other entries.
         **/
        private ClassDoc[] exceptionTypes;

        /**
         * Creates a new Method instance for the specified method.
         **/
        Method(MethodDoc methodDoc) {
            this.methodDoc = methodDoc;
            exceptionTypes = methodDoc.thrownExceptions();
            /*
             * Sort exception types to improve consistency with
             * previous implementations.
             */
            Arrays.sort(exceptionTypes, new ClassDocComparator());
            operationString = computeOperationString();
            nameAndDescriptor =
                methodDoc.name() + Util.methodDescriptorOf(methodDoc);
            methodHash = computeMethodHash();
        }

        /**
         * Returns the MethodDoc object corresponding to this method
         * of a remote interface.
         **/
        MethodDoc methodDoc() {
            return methodDoc;
        }

        /**
         * Returns the parameter types declared by this method.
         **/
        Type[] parameterTypes() {
            Parameter[] parameters = methodDoc.parameters();
            Type[] paramTypes = new Type[parameters.length];
            for (int i = 0; i < paramTypes.length; i++) {
                paramTypes[i] = parameters[i].type();
            }
            return paramTypes;
        }

        /**
         * Returns the exception types declared to be thrown by this
         * remote method.
         *
         * For methods with the same name and descriptor inherited
         * from multiple remote interfaces, the array will contain the
         * set of exceptions declared in all of the interfaces'
         * methods that can be legally thrown by all of them.
         **/
        ClassDoc[] exceptionTypes() {
            return (ClassDoc[]) exceptionTypes.clone();
        }

        /**
         * Returns the JRMP "method hash" used to identify this remote
         * method in the JDK 1.2 version of the stub protocol.
         **/
        long methodHash() {
            return methodHash;
        }

        /**
         * Returns the string representation of this method
         * appropriate for the construction of a
         * java.rmi.server.Operation object.
         **/
        String operationString() {
            return operationString;
        }

        /**
         * Returns a string consisting of this method's name followed
         * by its descriptor.
         **/
        String nameAndDescriptor() {
            return nameAndDescriptor;
        }

        /**
         * Returns a new Method object that is a legal combination of
         * this Method object and another one.
         *
         * Doing this requires determining the exceptions declared by
         * the combined method, which must be (only) all of the
         * exceptions declared in both old Methods that may thrown in
         * either of them.
         **/
        Method mergeWith(Method other) {
            if (!nameAndDescriptor().equals(other.nameAndDescriptor())) {
                throw new AssertionError(
                    "attempt to merge method \"" +
                    other.nameAndDescriptor() + "\" with \"" +
                    nameAndDescriptor());
            }

            List<ClassDoc> legalExceptions = new ArrayList<ClassDoc>();
            collectCompatibleExceptions(
                other.exceptionTypes, exceptionTypes, legalExceptions);
            collectCompatibleExceptions(
                exceptionTypes, other.exceptionTypes, legalExceptions);

            Method merged = clone();
            merged.exceptionTypes =
                legalExceptions.toArray(new ClassDoc[legalExceptions.size()]);

            return merged;
        }

        /**
         * Cloning is supported by returning a shallow copy of this
         * object.
         **/
        protected Method clone() {
            try {
                return (Method) super.clone();
            } catch (CloneNotSupportedException e) {
                throw new AssertionError(e);
            }
        }

        /**
         * Adds to the supplied list all exceptions in the "froms"
         * array that are subclasses of an exception in the "withs"
         * array.
         **/
        private void collectCompatibleExceptions(ClassDoc[] froms,
                                                 ClassDoc[] withs,
                                                 List<ClassDoc> list)
        {
            for (ClassDoc from : froms) {
                if (!list.contains(from)) {
                    for (ClassDoc with : withs) {
                        if (from.subclassOf(with)) {
                            list.add(from);
                            break;
                        }
                    }
                }
            }
        }

        /**
         * Computes the JRMP "method hash" of this remote method.  The
         * method hash is a long containing the first 64 bits of the
         * SHA digest from the UTF-8 encoded string of the method name
         * and descriptor.
         **/
        private long computeMethodHash() {
            long hash = 0;
            ByteArrayOutputStream sink = new ByteArrayOutputStream(512);
            try {
                MessageDigest md = MessageDigest.getInstance("SHA");
                DataOutputStream out = new DataOutputStream(
                    new DigestOutputStream(sink, md));

                String methodString = nameAndDescriptor();
                out.writeUTF(methodString);

                // use only the first 64 bits of the digest for the hash
                out.flush();
                byte hashArray[] = md.digest();
                for (int i = 0; i < Math.min(8, hashArray.length); i++) {
                    hash += ((long) (hashArray[i] & 0xFF)) << (i * 8);
                }
            } catch (IOException e) {
                throw new AssertionError(e);
            } catch (NoSuchAlgorithmException e) {
                throw new AssertionError(e);
            }

            return hash;
        }

        /**
         * Computes the string representation of this method
         * appropriate for the construction of a
         * java.rmi.server.Operation object.
         **/
        private String computeOperationString() {
            /*
             * To be consistent with previous implementations, we use
             * the deprecated style of placing the "[]" for the return
             * type (if any) after the parameter list.
             */
            Type returnType = methodDoc.returnType();
            String op = returnType.qualifiedTypeName() + " " +
                methodDoc.name() + "(";
            Parameter[] parameters = methodDoc.parameters();
            for (int i = 0; i < parameters.length; i++) {
                if (i > 0) {
                    op += ", ";
                }
                op += parameters[i].type().toString();
            }
            op += ")" + returnType.dimension();
            return op;
        }
    }
}