/*
 * Copyright (c) 2011, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.snippets;

import java.lang.annotation.*;
import java.lang.reflect.*;

import com.oracle.graal.api.meta.*;
import com.oracle.graal.graph.Node.NodeIntrinsic;
import com.oracle.graal.nodes.extended.*;
import com.oracle.graal.nodes.type.*;
import com.oracle.graal.snippets.nodes.*;
import com.oracle.graal.word.*;

/**
 * A snippet is a Graal graph expressed as a Java source method. Graal snippets can be used for:
 * <ul>
 * <li>intrinsifying native JDK methods (see {@link ClassSubstitution})</li>
 * <li>lowering operations that have runtime dependent semantics (e.g. the {@code CHECKCAST}
 * bytecode)</li>
 * <li>replacing a method call with a single graph node (see {@link NodeIntrinsic})</li>
 * </ul>
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Snippet {

    /**
     * Specifies the class defining the inlining policy for this snippet. A
     * {@linkplain DefaultSnippetInliningPolicy default} policy is used if none is supplied.
     */
    Class<? extends SnippetInliningPolicy> inlining() default SnippetInliningPolicy.class;

    /**
     * Guides inlining decisions used when installing a snippet.
     */
    public interface SnippetInliningPolicy {

        /**
         * Determines if {@code method} should be inlined into {@code caller}.
         */
        boolean shouldInline(ResolvedJavaMethod method, ResolvedJavaMethod caller);
    }

    /**
     * The default inlining policy which inlines everything except for methods in any of the
     * following categories.
     * <ul>
     * <li>{@linkplain Fold foldable} methods</li>
     * <li>{@linkplain NodeIntrinsic node intrinsics}</li>
     * <li>native methods</li>
     * <li>constructors of {@link Throwable} classes</li>
     * </ul>
     */
    public static class DefaultSnippetInliningPolicy implements SnippetInliningPolicy {

        private final MetaAccessProvider metaAccess;
        private final BoxingMethodPool pool;

        public DefaultSnippetInliningPolicy(MetaAccessProvider metaAccess, BoxingMethodPool pool) {
            this.metaAccess = metaAccess;
            this.pool = pool;
        }

        @Override
        public boolean shouldInline(ResolvedJavaMethod method, ResolvedJavaMethod caller) {
            if (Modifier.isNative(method.getModifiers())) {
                return false;
            }
            if (method.getAnnotation(Fold.class) != null) {
                return false;
            }
            if (method.getAnnotation(NodeIntrinsic.class) != null) {
                return false;
            }
            if (metaAccess.lookupJavaType(Throwable.class).isAssignableFrom(method.getDeclaringClass())) {
                if (method.getName().equals("<init>")) {
                    return false;
                }
            }
            if (method.getAnnotation(Word.Operation.class) != null) {
                return false;
            }
            if (pool.isSpecialMethod(method)) {
                return false;
            }
            return true;
        }
    }

    /**
     * Annotates a method replaced by a compile-time constant. A (resolved) call to the annotated
     * method is replaced with a constant obtained by calling the annotated method via reflection.
     * 
     * All arguments to such a method (including the receiver if applicable) must be compile-time
     * constants.
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    public static @interface Fold {
    }

    /**
     * Denotes a snippet parameter that will be bound during snippet template
     * {@linkplain SnippetTemplate#instantiate instantiation}.
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.PARAMETER)
    public @interface Parameter {

        /**
         * The name of this parameter.
         */
        String value();
    }

    /**
     * Denotes a snippet parameter representing 0 or more arguments that will be bound during
     * snippet template {@linkplain SnippetTemplate#instantiate instantiation}. During snippet
     * template creation, its value must be an array whose length specifies the number of arguments
     * (the contents of the array are ignored) bound to the parameter during
     * {@linkplain SnippetTemplate#instantiate instantiation}.
     * 
     * Such a parameter must be used in a counted loop in the snippet preceded by a call to
     * {@link ExplodeLoopNode#explodeLoop()}. The counted looped must be a standard iteration over
     * all the loop's elements (i.e. {@code for (T e : arr) ... }).
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.PARAMETER)
    public @interface VarargsParameter {

        /**
         * The name of this parameter.
         */
        String value();
    }

    /**
     * Denotes a snippet parameter that will bound to a constant value during snippet template
     * {@linkplain SnippetTemplate#instantiate instantiation}.
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.PARAMETER)
    public @interface ConstantParameter {

        /**
         * The name of this constant.
         */
        String value();
    }

    /**
     * Wrapper for the prototype value of a {@linkplain VarargsParameter varargs} parameter.
     */
    public static class Varargs {

        private final Object args;
        private final Class argType;
        private final int length;
        private final Stamp argStamp;

        public static Varargs vargargs(Object array, Stamp argStamp) {
            return new Varargs(array, argStamp);
        }

        public Varargs(Object array, Stamp argStamp) {
            assert array != null;
            this.argType = array.getClass().getComponentType();
            this.argStamp = argStamp;
            assert this.argType != null;
            this.length = java.lang.reflect.Array.getLength(array);
            this.args = array;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj instanceof Varargs) {
                Varargs other = (Varargs) obj;
                return other.argType == argType && other.length == length;
            }
            return false;
        }

        public Object getArray() {
            return args;
        }

        public Stamp getArgStamp() {
            return argStamp;
        }

        @Override
        public int hashCode() {
            return argType.hashCode() ^ length;
        }

        @Override
        public String toString() {
            return argType.getName() + "[" + length + "]";
        }
    }
}