/*
 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. 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.  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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.lookup;

import static jdk.nashorn.internal.runtime.JSType.isString;

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.invoke.SwitchPoint;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.logging.Level;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.Debug;
import jdk.nashorn.internal.runtime.ScriptObject;
import jdk.nashorn.internal.runtime.logging.DebugLogger;
import jdk.nashorn.internal.runtime.logging.Loggable;
import jdk.nashorn.internal.runtime.logging.Logger;
import jdk.nashorn.internal.runtime.options.Options;

This class is abstraction for all method handle, switchpoint and method type
operations. This enables the functionality interface to be subclassed and
instrumented, as it has been proven vital to keep the number of method
handles in the system down.
All operations of the above type should go through this class, and not
directly into java.lang.invoke
/**
 * This class is abstraction for all method handle, switchpoint and method type
 * operations. This enables the functionality interface to be subclassed and
 * instrumented, as it has been proven vital to keep the number of method
 * handles in the system down.
 *
 * All operations of the above type should go through this class, and not
 * directly into java.lang.invoke
 *
 */
public final class MethodHandleFactory {

    private static final MethodHandles.Lookup PUBLIC_LOOKUP = MethodHandles.publicLookup();
    private static final MethodHandles.Lookup LOOKUP        = MethodHandles.lookup();

    private static final Level TRACE_LEVEL = Level.INFO;

    private MethodHandleFactory() {
    }

    
Runtime exception that collects every reason that a method handle lookup operation can go wrong
/**
     * Runtime exception that collects every reason that a method handle lookup operation can go wrong
     */
    @SuppressWarnings("serial")
    public static class LookupException extends RuntimeException {
        
Constructor
Params:
e – causing exception/**
         * Constructor
         * @param e causing exception
         */
        public LookupException(final Exception e) {
            super(e);
        }
    }

    
Helper function that takes a class or an object with a toString override
and shortens it to notation after last dot. This is used to facilitiate
pretty printouts in various debug loggers - internal only
Params:
obj – class or object
Returns:
pretty version of object as string/**
     * Helper function that takes a class or an object with a toString override
     * and shortens it to notation after last dot. This is used to facilitiate
     * pretty printouts in various debug loggers - internal only
     *
     * @param obj class or object
     *
     * @return pretty version of object as string
     */
    public static String stripName(final Object obj) {
        if (obj == null) {
            return "null";
        }

        if (obj instanceof Class) {
            return ((Class<?>)obj).getSimpleName();
        }
        return obj.toString();
    }

    private static final MethodHandleFunctionality FUNC = new StandardMethodHandleFunctionality();
    private static final boolean PRINT_STACKTRACE = Options.getBooleanProperty("nashorn.methodhandles.debug.stacktrace");

    
Return the method handle functionality used for all method handle operations
Returns:
a method handle functionality implementation/**
     * Return the method handle functionality used for all method handle operations
     * @return a method handle functionality implementation
     */
    public static MethodHandleFunctionality getFunctionality() {
        return FUNC;
    }

    private static final MethodHandle TRACE             = FUNC.findStatic(LOOKUP, MethodHandleFactory.class, "traceArgs",   MethodType.methodType(void.class, DebugLogger.class, String.class, int.class, Object[].class));
    private static final MethodHandle TRACE_RETURN      = FUNC.findStatic(LOOKUP, MethodHandleFactory.class, "traceReturn", MethodType.methodType(Object.class, DebugLogger.class, Object.class));
    private static final MethodHandle TRACE_RETURN_VOID = FUNC.findStatic(LOOKUP, MethodHandleFactory.class, "traceReturnVoid", MethodType.methodType(void.class, DebugLogger.class));

    private static final String VOID_TAG = "[VOID]";

    private static void err(final String str) {
        Context.getContext().getErr().println(str);
    }

    
Tracer that is applied before a value is returned from the traced function. It will output the return
value and its class
Params:
value – return value for filter
Returns:
return value unmodified/**
     * Tracer that is applied before a value is returned from the traced function. It will output the return
     * value and its class
     *
     * @param value return value for filter
     * @return return value unmodified
     */
    static Object traceReturn(final DebugLogger logger, final Object value) {
        final String str = "    return" +
                (VOID_TAG.equals(value) ?
                        ";" :
                            " " + stripName(value) + "; // [type=" + (value == null ? "null]" : stripName(value.getClass()) + ']'));
        if (logger == null) {
            err(str);
        } else if (logger.isEnabled()) {
            logger.log(TRACE_LEVEL, str);
        }

        return value;
    }

    static void traceReturnVoid(final DebugLogger logger) {
        traceReturn(logger, VOID_TAG);
    }

    
Tracer that is applied before a function is called, printing the arguments
Params:
tag –  tag to start the debug printout string
paramStart – param index to start outputting from
args – arguments to the function/**
     * Tracer that is applied before a function is called, printing the arguments
     *
     * @param tag  tag to start the debug printout string
     * @param paramStart param index to start outputting from
     * @param args arguments to the function
     */
    static void traceArgs(final DebugLogger logger, final String tag, final int paramStart, final Object... args) {
        final StringBuilder sb = new StringBuilder();

        sb.append(tag);

        for (int i = paramStart; i < args.length; i++) {
            if (i == paramStart) {
                sb.append(" => args: ");
            }

            sb.append('\'').
            append(stripName(argString(args[i]))).
            append('\'').
            append(' ').
            append('[').
            append("type=").
            append(args[i] == null ? "null" : stripName(args[i].getClass())).
            append(']');

            if (i + 1 < args.length) {
                sb.append(", ");
            }
        }

        if (logger == null) {
            err(sb.toString());
        } else {
            logger.log(TRACE_LEVEL, sb);
        }
        stacktrace(logger);
    }

    private static void stacktrace(final DebugLogger logger) {
        if (!PRINT_STACKTRACE) {
            return;
        }
        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
        final PrintStream ps = new PrintStream(baos);
        new Throwable().printStackTrace(ps);
        final String st = baos.toString();
        if (logger == null) {
            err(st);
        } else {
            logger.log(TRACE_LEVEL, st);
        }
    }

    private static String argString(final Object arg) {
        if (arg == null) {
            return "null";
        }

        if (arg.getClass().isArray()) {
            final List<Object> list = new ArrayList<>();
            for (final Object elem : (Object[])arg) {
                list.add('\'' + argString(elem) + '\'');
            }

            return list.toString();
        }

        if (arg instanceof ScriptObject) {
            return arg.toString() +
                    " (map=" + Debug.id(((ScriptObject)arg).getMap()) +
                    ')';
        }

        return arg.toString();
    }

    
Add a debug printout to a method handle, tracing parameters and return values
Output will be unconditional to stderr
Params:
mh –  method handle to trace
tag – start of trace message
Returns:
traced method handle/**
     * Add a debug printout to a method handle, tracing parameters and return values
     * Output will be unconditional to stderr
     *
     * @param mh  method handle to trace
     * @param tag start of trace message
     * @return traced method handle
     */
    public static MethodHandle addDebugPrintout(final MethodHandle mh, final Object tag) {
        return addDebugPrintout(null, Level.OFF, mh, 0, true, tag);
    }

    
Add a debug printout to a method handle, tracing parameters and return values
Params:
logger – a specific logger to which to write the output
level – level over which to print
mh –  method handle to trace
tag – start of trace message
Returns:
traced method handle/**
     * Add a debug printout to a method handle, tracing parameters and return values
     *
     * @param logger a specific logger to which to write the output
     * @param level level over which to print
     * @param mh  method handle to trace
     * @param tag start of trace message
     * @return traced method handle
     */
    public static MethodHandle addDebugPrintout(final DebugLogger logger, final Level level, final MethodHandle mh, final Object tag) {
        return addDebugPrintout(logger, level, mh, 0, true, tag);
    }

    
Add a debug printout to a method handle, tracing parameters and return values
Output will be unconditional to stderr
Params:
mh –  method handle to trace
paramStart – first param to print/trace
printReturnValue – should we print/trace return value if available?
tag – start of trace message
Returns:
 traced method handle/**
     * Add a debug printout to a method handle, tracing parameters and return values
     * Output will be unconditional to stderr
     *
     * @param mh  method handle to trace
     * @param paramStart first param to print/trace
     * @param printReturnValue should we print/trace return value if available?
     * @param tag start of trace message
     * @return  traced method handle
     */
    public static MethodHandle addDebugPrintout(final MethodHandle mh, final int paramStart, final boolean printReturnValue, final Object tag) {
        return addDebugPrintout(null, Level.OFF, mh, paramStart, printReturnValue, tag);
    }

    
Add a debug printout to a method handle, tracing parameters and return values
Params:
logger – a specific logger to which to write the output
level – level over which to print
mh –  method handle to trace
paramStart – first param to print/trace
printReturnValue – should we print/trace return value if available?
tag – start of trace message
Returns:
 traced method handle/**
     * Add a debug printout to a method handle, tracing parameters and return values
     *
     * @param logger a specific logger to which to write the output
     * @param level level over which to print
     * @param mh  method handle to trace
     * @param paramStart first param to print/trace
     * @param printReturnValue should we print/trace return value if available?
     * @param tag start of trace message
     * @return  traced method handle
     */
    public static MethodHandle addDebugPrintout(final DebugLogger logger, final Level level, final MethodHandle mh, final int paramStart, final boolean printReturnValue, final Object tag) {
        final MethodType type = mh.type();

        //if there is no logger, or if it's set to log only coarser events
        //than the trace level, skip and return
        if (logger == null || !logger.isLoggable(level)) {
            return mh;
        }

        assert TRACE != null;

        MethodHandle trace = MethodHandles.insertArguments(TRACE, 0, logger, tag, paramStart);

        trace = MethodHandles.foldArguments(
                mh,
                trace.asCollector(
                        Object[].class,
                        type.parameterCount()).
                        asType(type.changeReturnType(void.class)));

        final Class<?> retType = type.returnType();
        if (printReturnValue) {
            if (retType != void.class) {
                final MethodHandle traceReturn = MethodHandles.insertArguments(TRACE_RETURN, 0, logger);
                trace = MethodHandles.filterReturnValue(trace,
                        traceReturn.asType(
                                traceReturn.type().changeParameterType(0, retType).changeReturnType(retType)));
            } else {
                trace = MethodHandles.filterReturnValue(trace, MethodHandles.insertArguments(TRACE_RETURN_VOID, 0, logger));
            }
        }

        return trace;
    }

    
Class that marshalls all method handle operations to the java.lang.invoke
package. This exists only so that it can be subclassed and method handles created from
Nashorn made possible to instrument.
All Nashorn classes should use the MethodHandleFactory for their method handle operations
/**
     * Class that marshalls all method handle operations to the java.lang.invoke
     * package. This exists only so that it can be subclassed and method handles created from
     * Nashorn made possible to instrument.
     *
     * All Nashorn classes should use the MethodHandleFactory for their method handle operations
     */
    @Logger(name="methodhandles")
    private static class StandardMethodHandleFunctionality implements MethodHandleFunctionality, Loggable {

        // for bootstrapping reasons, because a lot of static fields use MH for lookups, we
        // need to set the logger when the Global object is finished. This means that we don't
        // get instrumentation for public static final MethodHandle SOMETHING = MH... in the builtin
        // classes, but that doesn't matter, because this is usually not where we want it
        private DebugLogger log = DebugLogger.DISABLED_LOGGER;

        public StandardMethodHandleFunctionality() {
        }

        @Override
        public DebugLogger initLogger(final Context context) {
            return this.log = context.getLogger(this.getClass());
        }

        @Override
        public DebugLogger getLogger() {
            return log;
        }

        protected static String describe(final Object... data) {
            final StringBuilder sb = new StringBuilder();

            for (int i = 0; i < data.length; i++) {
                final Object d = data[i];
                if (d == null) {
                    sb.append("<null> ");
                } else if (isString(d)) {
                    sb.append(d.toString());
                    sb.append(' ');
                } else if (d.getClass().isArray()) {
                    sb.append("[ ");
                    for (final Object da : (Object[])d) {
                        sb.append(describe(new Object[]{ da })).append(' ');
                    }
                    sb.append("] ");
                } else {
                    sb.append(d)
                    .append('{')
                    .append(Integer.toHexString(System.identityHashCode(d)))
                    .append('}');
                }

                if (i + 1 < data.length) {
                    sb.append(", ");
                }
            }

            return sb.toString();
        }

        public MethodHandle debug(final MethodHandle master, final String str, final Object... args) {
            if (log.isEnabled()) {
                if (PRINT_STACKTRACE) {
                    stacktrace(log);
                }
                return addDebugPrintout(log, Level.INFO, master, Integer.MAX_VALUE, false, str + ' ' + describe(args));
            }
            return master;
        }

        @Override
        public MethodHandle filterArguments(final MethodHandle target, final int pos, final MethodHandle... filters) {
            final MethodHandle mh = MethodHandles.filterArguments(target, pos, filters);
            return debug(mh, "filterArguments", target, pos, filters);
        }

        @Override
        public MethodHandle filterReturnValue(final MethodHandle target, final MethodHandle filter) {
            final MethodHandle mh = MethodHandles.filterReturnValue(target, filter);
            return debug(mh, "filterReturnValue", target, filter);
        }

        @Override
        public MethodHandle guardWithTest(final MethodHandle test, final MethodHandle target, final MethodHandle fallback) {
            final MethodHandle mh = MethodHandles.guardWithTest(test, target, fallback);
            return debug(mh, "guardWithTest", test, target, fallback);
        }

        @Override
        public MethodHandle insertArguments(final MethodHandle target, final int pos, final Object... values) {
            final MethodHandle mh = MethodHandles.insertArguments(target, pos, values);
            return debug(mh, "insertArguments", target, pos, values);
        }

        @Override
        public MethodHandle dropArguments(final MethodHandle target, final int pos, final Class<?>... values) {
            final MethodHandle mh = MethodHandles.dropArguments(target, pos, values);
            return debug(mh, "dropArguments", target, pos, values);
        }

        @Override
        public MethodHandle dropArguments(final MethodHandle target, final int pos, final List<Class<?>> values) {
            final MethodHandle mh = MethodHandles.dropArguments(target, pos, values);
            return debug(mh, "dropArguments", target, pos, values);
        }

        @Override
        public MethodHandle asType(final MethodHandle handle, final MethodType type) {
            final MethodHandle mh = handle.asType(type);
            return debug(mh, "asType", handle, type);
        }

        @Override
        public MethodHandle bindTo(final MethodHandle handle, final Object x) {
            final MethodHandle mh = handle.bindTo(x);
            return debug(mh, "bindTo", handle, x);
        }

        @Override
        public MethodHandle foldArguments(final MethodHandle target, final MethodHandle combiner) {
            final MethodHandle mh = MethodHandles.foldArguments(target, combiner);
            return debug(mh, "foldArguments", target, combiner);
        }

        @Override
        public MethodHandle explicitCastArguments(final MethodHandle target, final MethodType type) {
            final MethodHandle mh = MethodHandles.explicitCastArguments(target, type);
            return debug(mh, "explicitCastArguments", target, type);
        }

        @Override
        public MethodHandle arrayElementGetter(final Class<?> type) {
            final MethodHandle mh = MethodHandles.arrayElementGetter(type);
            return debug(mh, "arrayElementGetter", type);
        }

        @Override
        public MethodHandle arrayElementSetter(final Class<?> type) {
            final MethodHandle mh = MethodHandles.arrayElementSetter(type);
            return debug(mh, "arrayElementSetter", type);
        }

        @Override
        public MethodHandle throwException(final Class<?> returnType, final Class<? extends Throwable> exType) {
            final MethodHandle mh = MethodHandles.throwException(returnType, exType);
            return debug(mh, "throwException", returnType, exType);
        }

        @Override
        public MethodHandle catchException(final MethodHandle target, final Class<? extends Throwable> exType, final MethodHandle handler) {
            final MethodHandle mh = MethodHandles.catchException(target, exType, handler);
            return debug(mh, "catchException", exType);
        }

        @Override
        public MethodHandle constant(final Class<?> type, final Object value) {
            final MethodHandle mh = MethodHandles.constant(type, value);
            return debug(mh, "constant", type, value);
        }

        @Override
        public MethodHandle identity(final Class<?> type) {
            final MethodHandle mh = MethodHandles.identity(type);
            return debug(mh, "identity", type);
        }

        @Override
        public MethodHandle asCollector(final MethodHandle handle, final Class<?> arrayType, final int arrayLength) {
            final MethodHandle mh = handle.asCollector(arrayType, arrayLength);
            return debug(mh, "asCollector", handle, arrayType, arrayLength);
        }

        @Override
        public MethodHandle asSpreader(final MethodHandle handle, final Class<?> arrayType, final int arrayLength) {
            final MethodHandle mh = handle.asSpreader(arrayType, arrayLength);
            return debug(mh, "asSpreader", handle, arrayType, arrayLength);
        }

        @Override
        public MethodHandle getter(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final Class<?> type) {
            try {
                final MethodHandle mh = explicitLookup.findGetter(clazz, name, type);
                return debug(mh, "getter", explicitLookup, clazz, name, type);
            } catch (final NoSuchFieldException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle staticGetter(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final Class<?> type) {
            try {
                final MethodHandle mh = explicitLookup.findStaticGetter(clazz, name, type);
                return debug(mh, "static getter", explicitLookup, clazz, name, type);
            } catch (final NoSuchFieldException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle setter(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final Class<?> type) {
            try {
                final MethodHandle mh = explicitLookup.findSetter(clazz, name, type);
                return debug(mh, "setter", explicitLookup, clazz, name, type);
            } catch (final NoSuchFieldException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle staticSetter(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final Class<?> type) {
            try {
                final MethodHandle mh = explicitLookup.findStaticSetter(clazz, name, type);
                return debug(mh, "static setter", explicitLookup, clazz, name, type);
            } catch (final NoSuchFieldException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle find(final Method method) {
            try {
                final MethodHandle mh = PUBLIC_LOOKUP.unreflect(method);
                return debug(mh, "find", method);
            } catch (final IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle findStatic(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final MethodType type) {
            try {
                final MethodHandle mh = explicitLookup.findStatic(clazz, name, type);
                return debug(mh, "findStatic", explicitLookup, clazz, name, type);
            } catch (final NoSuchMethodException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle findSpecial(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final MethodType type, final Class<?> thisClass) {
            try {
                final MethodHandle mh = explicitLookup.findSpecial(clazz, name, type, thisClass);
                return debug(mh, "findSpecial", explicitLookup, clazz, name, type);
            } catch (final NoSuchMethodException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public MethodHandle findVirtual(final MethodHandles.Lookup explicitLookup, final Class<?> clazz, final String name, final MethodType type) {
            try {
                final MethodHandle mh = explicitLookup.findVirtual(clazz, name, type);
                return debug(mh, "findVirtual", explicitLookup, clazz, name, type);
            } catch (final NoSuchMethodException | IllegalAccessException e) {
                throw new LookupException(e);
            }
        }

        @Override
        public SwitchPoint createSwitchPoint() {
            final SwitchPoint sp = new SwitchPoint();
            log.log(TRACE_LEVEL, "createSwitchPoint ", sp);
            return sp;
        }

        @Override
        public MethodHandle guardWithTest(final SwitchPoint sp, final MethodHandle before, final MethodHandle after) {
            final MethodHandle mh = sp.guardWithTest(before, after);
            return debug(mh, "guardWithTest", sp, before, after);
        }

        @Override
        public MethodType type(final Class<?> returnType, final Class<?>... paramTypes) {
            final MethodType mt = MethodType.methodType(returnType, paramTypes);
            log.log(TRACE_LEVEL, "methodType ", returnType, " ", Arrays.toString(paramTypes), " ", mt);
            return mt;
        }
    }
}