/*

 * Copyright (c) 2015, 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.

 *

 * 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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 * questions.

 */

package org.graalvm.compiler.nodes.graphbuilderconf;

import static org.graalvm.compiler.nodes.graphbuilderconf.InvocationPlugins.resolveType;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import java.lang.reflect.Type;

import java.util.Arrays;

import java.util.stream.Collectors;

import org.graalvm.compiler.bytecode.BytecodeProvider;

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.nodes.ValueNode;

import jdk.vm.ci.meta.MetaAccessProvider;

import jdk.vm.ci.meta.ResolvedJavaMethod;

/**

 * An {@link InvocationPlugin} for a method where the implementation of the method is provided by a

 * {@linkplain #getSubstitute(MetaAccessProvider) substitute} method. A substitute method must be

 * static even if the substituted method is not.

 *

 * While performing intrinsification with method substitutions is simpler than writing an

 * {@link InvocationPlugin} that does manual graph weaving, it has a higher compile time cost than

 * the latter; parsing bytecodes to create nodes is slower than simply creating nodes. As such, the

 * recommended practice is to use {@link MethodSubstitutionPlugin} only for complex

 * intrinsifications which is typically those using non-straight-line control flow.

 */

public final class MethodSubstitutionPlugin implements InvocationPlugin {

    private ResolvedJavaMethod cachedSubstitute;

    /**

     * The class in which the substitute method is declared.

     */

    private final Class<?> declaringClass;

    /**

     * The name of the original and substitute method.

     */

    private final String name;

    /**

     * The parameter types of the substitute method.

     */

    private final Type[] parameters;

    private final boolean originalIsStatic;

    private final BytecodeProvider bytecodeProvider;

    /**

     * Creates a method substitution plugin.

     *

     * @param bytecodeProvider used to get the bytecodes to parse for the substitute method

     * @param declaringClass the class in which the substitute method is declared

     * @param name the name of the substitute method

     * @param parameters the parameter types of the substitute method. If the original method is not

     *            static, then {@code parameters[0]} must be the {@link Class} value denoting

     *            {@link InvocationPlugin.Receiver}

     */

    public MethodSubstitutionPlugin(BytecodeProvider bytecodeProvider, Class<?> declaringClass, String name, Type... parameters) {

        this.bytecodeProvider = bytecodeProvider;

        this.declaringClass = declaringClass;

        this.name = name;

        this.parameters = parameters;

        this.originalIsStatic = parameters.length == 0 || parameters[0] != InvocationPlugin.Receiver.class;

    }

    @Override

    public boolean inlineOnly() {

        // Conservatively assume MacroNodes may be used in a substitution

        return true;

    }

    /**

     * Gets the substitute method, resolving it first if necessary.

     */

    public ResolvedJavaMethod getSubstitute(MetaAccessProvider metaAccess) {

        if (cachedSubstitute == null) {

            cachedSubstitute = metaAccess.lookupJavaMethod(getJavaSubstitute());

        }

        return cachedSubstitute;

    }

    /**

     * Gets the object used to access the bytecodes of the substitute method.

     */

    public BytecodeProvider getBytecodeProvider() {

        return bytecodeProvider;

    }

    /**

     * Gets the reflection API version of the substitution method.

     */

    Method getJavaSubstitute() throws GraalError {

        Method substituteMethod = lookupSubstitute();

        int modifiers = substituteMethod.getModifiers();

        if (Modifier.isAbstract(modifiers) || Modifier.isNative(modifiers)) {

            throw new GraalError("Substitution method must not be abstract or native: " + substituteMethod);

        }

        if (!Modifier.isStatic(modifiers)) {

            throw new GraalError("Substitution method must be static: " + substituteMethod);

        }

        return substituteMethod;

    }

    /**

     * Determines if a given method is the substitute method of this plugin.

     */

    private boolean isSubstitute(Method m) {

        if (Modifier.isStatic(m.getModifiers()) && m.getName().equals(name)) {

            if (parameters.length == m.getParameterCount()) {

                Class<?>[] mparams = m.getParameterTypes();

                int start = 0;

                if (!originalIsStatic) {

                    start = 1;

                    if (!mparams[0].isAssignableFrom(resolveType(parameters[0], false))) {

                        return false;

                    }

                }

                for (int i = start; i < mparams.length; i++) {

                    if (mparams[i] != resolveType(parameters[i], false)) {

                        return false;

                    }

                }

                return true;

            }

        }

        return false;

    }

    private Method lookupSubstitute(Method excluding) {

        for (Method m : declaringClass.getDeclaredMethods()) {

            if (!m.equals(excluding) && isSubstitute(m)) {

                return m;

            }

        }

        return null;

    }

    /**

     * Gets the substitute method of this plugin.

     */

    private Method lookupSubstitute() {

        Method m = lookupSubstitute(null);

        if (m != null) {

            assert lookupSubstitute(m) == null : String.format("multiple matches found for %s:%n%s%n%s", this, m, lookupSubstitute(m));

            return m;

        }

        throw new GraalError("No method found specified by %s", this);

    }

    @Override

    public boolean execute(GraphBuilderContext b, ResolvedJavaMethod targetMethod, InvocationPlugin.Receiver receiver, ValueNode[] argsIncludingReceiver) {

        ResolvedJavaMethod subst = getSubstitute(b.getMetaAccess());

        return b.intrinsify(bytecodeProvider, targetMethod, subst, receiver, argsIncludingReceiver);

    }

    @Override

    public StackTraceElement getApplySourceLocation(MetaAccessProvider metaAccess) {

        Class<?> c = getClass();

        for (Method m : c.getDeclaredMethods()) {

            if (m.getName().equals("execute")) {

                return metaAccess.lookupJavaMethod(m).asStackTraceElement(0);

            }

        }

        throw new GraalError("could not find method named \"execute\" in " + c.getName());

    }

    @Override

    public String toString() {

        return String.format("%s[%s.%s(%s)]", getClass().getSimpleName(), declaringClass.getName(), name,

                        Arrays.asList(parameters).stream().map(c -> c.getTypeName()).collect(Collectors.joining(", ")));

    }

}