/*

 * Copyright (c) 2016, 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 org.graalvm.compiler.replacements.classfile;

import java.io.DataInputStream;

import java.io.IOException;

import java.io.InputStream;

import org.graalvm.compiler.api.replacements.SnippetReflectionProvider;

import org.graalvm.compiler.bytecode.Bytecode;

import org.graalvm.compiler.bytecode.BytecodeProvider;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.MetaAccessProvider;

import jdk.vm.ci.meta.ResolvedJavaField;

import jdk.vm.ci.meta.ResolvedJavaMethod;

import jdk.vm.ci.meta.ResolvedJavaType;

/**

 * A {@link BytecodeProvider} that provides bytecode properties of a {@link ResolvedJavaMethod} as

 * parsed from a class file. This avoids all {@linkplain java.lang.instrument.Instrumentation

 * instrumentation} and any bytecode rewriting performed by the VM.

 *

 * This mechanism retrieves class files based on the name and {@link ClassLoader} of existing

 * {@link Class} instances. It bypasses all VM parsing and verification of the class file and

 * assumes the class files are well formed. As such, it should only be used for classes from a

 * trusted source such as the boot class (or module) path.

 *

 * A combination of {@link Class#forName(String)} and an existing {@link MetaAccessProvider} is used

 * to resolve constant pool references. This opens up the opportunity for linkage errors if the

 * referee is structurally changed through redefinition (e.g., a referred to method is renamed or

 * deleted). This will result in an appropriate {@link LinkageError} being thrown. The only way to

 * avoid this is to have a completely isolated {@code jdk.vm.ci.meta} implementation for parsing

 * snippet/intrinsic bytecodes.

 */

public final class ClassfileBytecodeProvider implements BytecodeProvider {

    private final ClassLoader loader;

    private final EconomicMap<Class<?>, Classfile> classfiles = EconomicMap.create(Equivalence.IDENTITY);

    private final EconomicMap<String, Class<?>> classes = EconomicMap.create();

    private final EconomicMap<ResolvedJavaType, FieldsCache> fields = EconomicMap.create();

    private final EconomicMap<ResolvedJavaType, MethodsCache> methods = EconomicMap.create();

    final MetaAccessProvider metaAccess;

    final SnippetReflectionProvider snippetReflection;

    public ClassfileBytecodeProvider(MetaAccessProvider metaAccess, SnippetReflectionProvider snippetReflection) {

        this.metaAccess = metaAccess;

        this.snippetReflection = snippetReflection;

        ClassLoader cl = getClass().getClassLoader();

        this.loader = cl == null ? ClassLoader.getSystemClassLoader() : cl;

    }

    public ClassfileBytecodeProvider(MetaAccessProvider metaAccess, SnippetReflectionProvider snippetReflection, ClassLoader loader) {

        this.metaAccess = metaAccess;

        this.snippetReflection = snippetReflection;

        this.loader = loader;

    }

    @Override

    public Bytecode getBytecode(ResolvedJavaMethod method) {

        Classfile classfile = getClassfile(resolveToClass(method.getDeclaringClass().getName()));

        return classfile.getCode(method.getName(), method.getSignature().toMethodDescriptor());

    }

    @Override

    public boolean supportsInvokedynamic() {

        return false;

    }

    @Override

    public boolean shouldRecordMethodDependencies() {

        return false;

    }

    /**

     * Gets a {@link Classfile} created by parsing the class file bytes for {@code c}.

     *

     * @throws NoClassDefFoundError if the class file cannot be found

     */

    private synchronized Classfile getClassfile(Class<?> c) {

        assert !c.isPrimitive() && !c.isArray() : c;

        Classfile classfile = classfiles.get(c);

        if (classfile == null) {

            try {

                ResolvedJavaType type = metaAccess.lookupJavaType(c);

                if (in != null) {

                    DataInputStream stream = new DataInputStream(in);

                    classfile = new Classfile(type, stream, this);

                    classfiles.put(c, classfile);

                    return classfile;

                }

                throw new NoClassDefFoundError(c.getName());

            } catch (IOException e) {

                throw (NoClassDefFoundError) new NoClassDefFoundError(c.getName()).initCause(e);

            }

        }

        return classfile;

    }

    synchronized Class<?> resolveToClass(String descriptor) {

        Class<?> c = classes.get(descriptor);

        if (c == null) {

            if (descriptor.length() == 1) {

                c = JavaKind.fromPrimitiveOrVoidTypeChar(descriptor.charAt(0)).toJavaClass();

            } else {

                int dimensions = 0;

                while (descriptor.charAt(dimensions) == '[') {

                    dimensions++;

                }

                String name;

                if (dimensions == 0 && descriptor.startsWith("L") && descriptor.endsWith(";")) {

                    name = descriptor.substring(1, descriptor.length() - 1).replace('/', '.');

                } else {

                    name = descriptor.replace('/', '.');

                }

                try {

                    c = Class.forName(name, true, loader);

                    classes.put(descriptor, c);

                } catch (ClassNotFoundException e) {

                    throw new NoClassDefFoundError(descriptor);

                }

            }

        }

        return c;

    }

    /**

     * Name and type of a field.

     */

    static final class FieldKey {

        final String name;

        final String type;

        FieldKey(String name, String type) {

            this.name = name;

            this.type = type;

        }

        @Override

        public String toString() {

            return name + ":" + type;

        }

        @Override

        public boolean equals(Object obj) {

            if (obj instanceof FieldKey) {

                FieldKey that = (FieldKey) obj;

                return that.name.equals(this.name) && that.type.equals(this.type);

            }

            return false;

        }

        @Override

        public int hashCode() {

            return name.hashCode() ^ type.hashCode();

        }

    }

    /**

     * Name and descriptor of a method.

     */

    static final class MethodKey {

        final String name;

        final String descriptor;

        MethodKey(String name, String descriptor) {

            this.name = name;

            this.descriptor = descriptor;

        }

        @Override

        public String toString() {

            return name + ":" + descriptor;

        }

        @Override

        public boolean equals(Object obj) {

            if (obj instanceof MethodKey) {

                MethodKey that = (MethodKey) obj;

                return that.name.equals(this.name) && that.descriptor.equals(this.descriptor);

            }

            return false;

        }

        @Override

        public int hashCode() {

            return name.hashCode() ^ descriptor.hashCode();

        }

    }

    /**

     * Method cache for a {@link ResolvedJavaType}.

     */

    static final class MethodsCache {

        volatile EconomicMap<MethodKey, ResolvedJavaMethod> constructors;

        volatile EconomicMap<MethodKey, ResolvedJavaMethod> methods;

        ResolvedJavaMethod lookup(ResolvedJavaType type, String name, String descriptor) {

            MethodKey key = new MethodKey(name, descriptor);

            if (name.equals("<clinit>")) {

                // No need to cache <clinit> as it will be looked up at most once

                return type.getClassInitializer();

            }

            if (!name.equals("<init>")) {

                if (methods == null) {

                    // Racy initialization is safe since `methods` is volatile

                    methods = createMethodMap(type.getDeclaredMethods());

                }

                return methods.get(key);

            } else {

                if (constructors == null) {

                    // Racy initialization is safe since instanceFields is volatile

                    constructors = createMethodMap(type.getDeclaredConstructors());

                }

                return constructors.get(key);

            }

        }

        private static EconomicMap<MethodKey, ResolvedJavaMethod> createMethodMap(ResolvedJavaMethod[] methodArray) {

            EconomicMap<MethodKey, ResolvedJavaMethod> map = EconomicMap.create();

            for (ResolvedJavaMethod m : methodArray) {

                map.put(new MethodKey(m.getName(), m.getSignature().toMethodDescriptor()), m);

            }

            return map;

        }

    }

    /**

     * Field cache for a {@link ResolvedJavaType}.

     */

    static final class FieldsCache {

        volatile EconomicMap<FieldKey, ResolvedJavaField> instanceFields;

        volatile EconomicMap<FieldKey, ResolvedJavaField> staticFields;

        ResolvedJavaField lookup(ResolvedJavaType type, String name, String fieldType, boolean isStatic) {

            FieldKey key = new FieldKey(name, fieldType);

            if (isStatic) {

                if (staticFields == null) {

                    // Racy initialization is safe since staticFields is volatile

                    staticFields = createFieldMap(type.getStaticFields());

                }

                return staticFields.get(key);

            } else {

                if (instanceFields == null) {

                    // Racy initialization is safe since instanceFields is volatile

                    instanceFields = createFieldMap(type.getInstanceFields(false));

                }

                return instanceFields.get(key);

            }

        }

        private static EconomicMap<FieldKey, ResolvedJavaField> createFieldMap(ResolvedJavaField[] fieldArray) {

            EconomicMap<FieldKey, ResolvedJavaField> map = EconomicMap.create();

            for (ResolvedJavaField f : fieldArray) {

                map.put(new FieldKey(f.getName(), f.getType().getName()), f);

            }

            return map;

        }

    }

    /**

     * Gets the methods cache for {@code type}.

     *

     * Synchronized since the cache is lazily created.

     */

    private synchronized MethodsCache getMethods(ResolvedJavaType type) {

        MethodsCache methodsCache = methods.get(type);

        if (methodsCache == null) {

            methodsCache = new MethodsCache();

            methods.put(type, methodsCache);

        }

        return methodsCache;

    }

    /**

     * Gets the fields cache for {@code type}.

     *

     * Synchronized since the cache is lazily created.

     */

    private synchronized FieldsCache getFields(ResolvedJavaType type) {

        FieldsCache fieldsCache = fields.get(type);

        if (fieldsCache == null) {

            fieldsCache = new FieldsCache();

            fields.put(type, fieldsCache);

        }

        return fieldsCache;

    }

    ResolvedJavaField findField(ResolvedJavaType type, String name, String fieldType, boolean isStatic) {

        return getFields(type).lookup(type, name, fieldType, isStatic);

    }

    ResolvedJavaMethod findMethod(ResolvedJavaType type, String name, String descriptor, boolean isStatic) {

        ResolvedJavaMethod method = getMethods(type).lookup(type, name, descriptor);

        if (method != null && method.isStatic() == isStatic) {

            return method;

        }

        return null;

    }

}