/*

 * Copyright (c) 2012, 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 java.lang.invoke;

import sun.invoke.util.VerifyAccess;

import java.lang.invoke.LambdaForm.Name;

import java.lang.invoke.MethodHandles.Lookup;

import sun.invoke.util.Wrapper;

import java.io.*;

import java.util.*;

import com.sun.xml.internal.ws.org.objectweb.asm.*;

import java.lang.reflect.*;

import static java.lang.invoke.MethodHandleStatics.*;

import static java.lang.invoke.MethodHandleNatives.Constants.*;

import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;

import sun.invoke.util.ValueConversions;

import sun.invoke.util.VerifyType;

/**

 * Code generation backend for LambdaForm.

 * <p>

 * @author John Rose, JSR 292 EG

 */

class InvokerBytecodeGenerator {

    /** Define class names for convenience. */

    private static final String MH      = "java/lang/invoke/MethodHandle";

    private static final String BMH     = "java/lang/invoke/BoundMethodHandle";

    private static final String LF      = "java/lang/invoke/LambdaForm";

    private static final String LFN     = "java/lang/invoke/LambdaForm$Name";

    private static final String CLS     = "java/lang/Class";

    private static final String OBJ     = "java/lang/Object";

    private static final String OBJARY  = "[Ljava/lang/Object;";

    private static final String LF_SIG  = "L" + LF + ";";

    private static final String LFN_SIG = "L" + LFN + ";";

    private static final String LL_SIG  = "(L" + OBJ + ";)L" + OBJ + ";";

    /** Name of its super class*/

    private static final String superName = LF;

    /** Name of new class */

    private final String className;

    /** Name of the source file (for stack trace printing). */

    private final String sourceFile;

    private final LambdaForm lambdaForm;

    private final String     invokerName;

    private final MethodType invokerType;

    private final int[] localsMap;

    /** ASM bytecode generation. */

    private ClassWriter cw;

    private MethodVisitor mv;

    private static final MemberName.Factory MEMBERNAME_FACTORY = MemberName.getFactory();

    private static final Class<?> HOST_CLASS = LambdaForm.class;

    private InvokerBytecodeGenerator(LambdaForm lambdaForm, int localsMapSize,

                                     String className, String invokerName, MethodType invokerType) {

        if (invokerName.contains(".")) {

            int p = invokerName.indexOf(".");

            className = invokerName.substring(0, p);

            invokerName = invokerName.substring(p+1);

        }

        if (DUMP_CLASS_FILES) {

            className = makeDumpableClassName(className);

        }

        this.className  = superName + "$" + className;

        this.sourceFile = "LambdaForm$" + className;

        this.lambdaForm = lambdaForm;

        this.invokerName = invokerName;

        this.invokerType = invokerType;

        this.localsMap = new int[localsMapSize];

    }

    private InvokerBytecodeGenerator(String className, String invokerName, MethodType invokerType) {

        this(null, invokerType.parameterCount(),

             className, invokerName, invokerType);

        // Create an array to map name indexes to locals indexes.

        for (int i = 0; i < localsMap.length; i++) {

            localsMap[i] = invokerType.parameterSlotCount() - invokerType.parameterSlotDepth(i);

        }

    }

    private InvokerBytecodeGenerator(String className, LambdaForm form, MethodType invokerType) {

        this(form, form.names.length,

             className, form.debugName, invokerType);

        // Create an array to map name indexes to locals indexes.

        Name[] names = form.names;

        for (int i = 0, index = 0; i < localsMap.length; i++) {

            localsMap[i] = index;

            index += Wrapper.forBasicType(names[i].type).stackSlots();

        }

    }

    /** instance counters for dumped classes */

    private final static HashMap<String,Integer> DUMP_CLASS_FILES_COUNTERS;

    /** debugging flag for saving generated class files */

    private final static File DUMP_CLASS_FILES_DIR;

    static {

        if (DUMP_CLASS_FILES) {

            DUMP_CLASS_FILES_COUNTERS = new HashMap<>();

            try {

                File dumpDir = new File("DUMP_CLASS_FILES");

                if (!dumpDir.exists()) {

                    dumpDir.mkdirs();

                }

                DUMP_CLASS_FILES_DIR = dumpDir;

                System.out.println("Dumping class files to "+DUMP_CLASS_FILES_DIR+"/...");

            } catch (Exception e) {

                throw new InternalError(e);

            }

        } else {

            DUMP_CLASS_FILES_COUNTERS = null;

            DUMP_CLASS_FILES_DIR = null;

        }

    }

    static void maybeDump(final String className, final byte[] classFile) {

        if (DUMP_CLASS_FILES) {

            System.out.println("dump: " + className);

            java.security.AccessController.doPrivileged(

            new java.security.PrivilegedAction<Void>() {

                public Void run() {

                    try {

                        String dumpName = className;

                        //dumpName = dumpName.replace('/', '-');

                        File dumpFile = new File(DUMP_CLASS_FILES_DIR, dumpName+".class");

                        dumpFile.getParentFile().mkdirs();

                        FileOutputStream file = new FileOutputStream(dumpFile);

                        file.write(classFile);

                        file.close();

                        return null;

                    } catch (IOException ex) {

                        throw new InternalError(ex);

                    }

                }

            });

        }

    }

    private static String makeDumpableClassName(String className) {

        Integer ctr;

        synchronized (DUMP_CLASS_FILES_COUNTERS) {

            ctr = DUMP_CLASS_FILES_COUNTERS.get(className);

            if (ctr == null)  ctr = 0;

            DUMP_CLASS_FILES_COUNTERS.put(className, ctr+1);

        }

        String sfx = ctr.toString();

        while (sfx.length() < 3)

            sfx = "0"+sfx;

        className += sfx;

        return className;

    }

    class CpPatch {

        int index;

        Object value;

        CpPatch(int index, Object value) {

            this.index = index;

            this.value = value;

        }

    }

    Map<Object, CpPatch> cpPatches = new HashMap<>();

    int cph = 0;  // for counting constant placeholders

    String constantPlaceholder(Object arg) {

        String cpPlaceholder = "CONSTANT_PLACEHOLDER_" + cph++;

        if (DUMP_CLASS_FILES) cpPlaceholder += " <<" + arg.toString() + ">>";  // debugging aid

        if (cpPatches.containsKey(cpPlaceholder)) {

            throw new InternalError("observed CP placeholder twice: " + cpPlaceholder);

        }

        // insert placeholder in CP and remember the patch

        int index = cw.newConst((Object) cpPlaceholder);  // TODO check if aready in the constant pool

        cpPatches.put(cpPlaceholder, new CpPatch(index, arg));

        return cpPlaceholder;

    }

    Object[] cpPatches(byte[] classFile) {

        int size = getConstantPoolSize(classFile);

        Object[] res = new Object[size];

        for (CpPatch p : cpPatches.values()) {

                res[p.index] = p.value;

        }

        return res;

    }

    /**

     * Extract the number of constant pool entries from a given class file.

     *

     * @param classFile the bytes of the class file in question.

     * @return the number of entries in the constant pool.

     */

    private static int getConstantPoolSize(byte[] classFile) {

        // The first few bytes:

        // u4 magic;

        // u2 minor_version;

        // u2 major_version;

        // u2 constant_pool_count;

    }

    /**

     * Extract the MemberName of a newly-defined method.

     *

     * @param classFile

     * @return

     */

    private MemberName loadMethod(byte[] classFile) {

        Class<?> invokerClass = loadAndInitializeInvokerClass(classFile, cpPatches(classFile));

        return resolveInvokerMember(invokerClass, invokerName, invokerType);

    }

    /**

     * Define a given class as anonymous class in the runtime system.

     *

     * @param classBytes

     * @param patches

     * @return

     */

    private static Class<?> loadAndInitializeInvokerClass(byte[] classBytes, Object[] patches) {

        Class<?> invokerClass = UNSAFE.defineAnonymousClass(HOST_CLASS, classBytes, patches);

        UNSAFE.ensureClassInitialized(invokerClass);  // Make sure the class is initialized; VM might complain.

        return invokerClass;

    }

    /**

     * TODO

     *

     * @param invokerClass

     * @param name

     * @param type

     * @return

     */

    private static MemberName resolveInvokerMember(Class<?> invokerClass, String name, MethodType type) {

        MemberName member = new MemberName(invokerClass, name, type, REF_invokeStatic);

        //System.out.println("resolveInvokerMember => "+member);

        //for (Method m : invokerClass.getDeclaredMethods())  System.out.println("  "+m);

        try {

            member = MEMBERNAME_FACTORY.resolveOrFail(REF_invokeStatic, member, HOST_CLASS, ReflectiveOperationException.class);

        } catch (ReflectiveOperationException e) {

            throw new InternalError(e);

        }

        //System.out.println("resolveInvokerMember => "+member);

        return member;

    }

    /**

     * Set up class file generation.

     */

    private void classFilePrologue() {

        cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);

        cw.visit(Opcodes.V1_6, Opcodes.ACC_PUBLIC + Opcodes.ACC_FINAL + Opcodes.ACC_SUPER, className, null, superName, null);

        cw.visitSource(sourceFile, null);

        String invokerDesc = invokerType.toMethodDescriptorString();

        mv = cw.visitMethod(Opcodes.ACC_STATIC, invokerName, invokerDesc, null, null);

        // Force inlining of this invoker method.

        mv.visitAnnotation("Ljava/lang/invoke/ForceInline;", true);

    }

    /**

     * Tear down class file generation.

     */

    private void classFileEpilogue() {

        mv.visitMaxs(0, 0);

        mv.visitEnd();

    }

    /*

     * Low-level emit helpers.

     */

    private void emitConst(Object con) {

        if (con == null) {

            mv.visitInsn(Opcodes.ACONST_NULL);

            return;

        }

        if (con instanceof Integer) {

            emitIconstInsn((int) con);

            return;

        }

        if (con instanceof Long) {

            long x = (long) con;

            if (x == (short) x) {

                emitIconstInsn((int) x);

                mv.visitInsn(Opcodes.I2L);

                return;

            }

        }

        if (con instanceof Float) {

            float x = (float) con;

            if (x == (short) x) {

                emitIconstInsn((int) x);

                mv.visitInsn(Opcodes.I2F);

                return;

            }

        }

        if (con instanceof Double) {

            double x = (double) con;

            if (x == (short) x) {

                emitIconstInsn((int) x);

                mv.visitInsn(Opcodes.I2D);

                return;

            }

        }

        if (con instanceof Boolean) {

            emitIconstInsn((boolean) con ? 1 : 0);

            return;

        }

        // fall through:

        mv.visitLdcInsn(con);

    }

    private void emitIconstInsn(int i) {

        int opcode;

        switch (i) {

        case 0:  opcode = Opcodes.ICONST_0;  break;

        case 1:  opcode = Opcodes.ICONST_1;  break;

        case 2:  opcode = Opcodes.ICONST_2;  break;

        case 3:  opcode = Opcodes.ICONST_3;  break;

        case 4:  opcode = Opcodes.ICONST_4;  break;

        case 5:  opcode = Opcodes.ICONST_5;  break;

        default:

            if (i == (byte) i) {

                mv.visitIntInsn(Opcodes.BIPUSH, i & 0xFF);

            } else if (i == (short) i) {

                mv.visitIntInsn(Opcodes.SIPUSH, (char) i);

            } else {

                mv.visitLdcInsn(i);

            }

            return;

        }

        mv.visitInsn(opcode);

    }

    /*

     * NOTE: These load/store methods use the localsMap to find the correct index!

     */

    private void emitLoadInsn(char type, int index) {

        int opcode;

        switch (type) {

        case 'I':  opcode = Opcodes.ILOAD;  break;

        case 'J':  opcode = Opcodes.LLOAD;  break;

        case 'F':  opcode = Opcodes.FLOAD;  break;

        case 'D':  opcode = Opcodes.DLOAD;  break;

        case 'L':  opcode = Opcodes.ALOAD;  break;

        default:

            throw new InternalError("unknown type: " + type);

        }

        mv.visitVarInsn(opcode, localsMap[index]);

    }

    private void emitAloadInsn(int index) {

        emitLoadInsn('L', index);

    }

    private void emitStoreInsn(char type, int index) {

        int opcode;

        switch (type) {

        case 'I':  opcode = Opcodes.ISTORE;  break;

        case 'J':  opcode = Opcodes.LSTORE;  break;

        case 'F':  opcode = Opcodes.FSTORE;  break;

        case 'D':  opcode = Opcodes.DSTORE;  break;

        case 'L':  opcode = Opcodes.ASTORE;  break;

        default:

            throw new InternalError("unknown type: " + type);

        }

        mv.visitVarInsn(opcode, localsMap[index]);

    }

    private void emitAstoreInsn(int index) {

        emitStoreInsn('L', index);

    }

    /**

     * Emit a boxing call.

     *

     * @param type primitive type class to box.

     */

    private void emitBoxing(Class<?> type) {

        Wrapper wrapper = Wrapper.forPrimitiveType(type);

        String owner = "java/lang/" + wrapper.wrapperType().getSimpleName();

        String name  = "valueOf";

        String desc  = "(" + wrapper.basicTypeChar() + ")L" + owner + ";";

        mv.visitMethodInsn(Opcodes.INVOKESTATIC, owner, name, desc);

    }

    /**

     * Emit an unboxing call (plus preceding checkcast).

     *

     * @param type wrapper type class to unbox.

     */

    private void emitUnboxing(Class<?> type) {

        Wrapper wrapper = Wrapper.forWrapperType(type);

        String owner = "java/lang/" + wrapper.wrapperType().getSimpleName();

        String name  = wrapper.primitiveSimpleName() + "Value";

        String desc  = "()" + wrapper.basicTypeChar();

        mv.visitTypeInsn(Opcodes.CHECKCAST, owner);

        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, owner, name, desc);

    }

    /**

     * Emit an implicit conversion.

     *

     * @param ptype type of value present on stack

     * @param pclass type of value required on stack

     */

    private void emitImplicitConversion(char ptype, Class<?> pclass) {

        switch (ptype) {

        case 'L':

            if (VerifyType.isNullConversion(Object.class, pclass))

                return;

            if (isStaticallyNameable(pclass)) {

                mv.visitTypeInsn(Opcodes.CHECKCAST, getInternalName(pclass));

            } else {

                mv.visitLdcInsn(constantPlaceholder(pclass));

                mv.visitTypeInsn(Opcodes.CHECKCAST, CLS);

                mv.visitInsn(Opcodes.SWAP);

                mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, CLS, "cast", LL_SIG);

                if (pclass.isArray())

                    mv.visitTypeInsn(Opcodes.CHECKCAST, OBJARY);

            }

            return;

        case 'I':

            if (!VerifyType.isNullConversion(int.class, pclass))

                emitPrimCast(ptype, Wrapper.basicTypeChar(pclass));

            return;

        case 'J':

            assert(pclass == long.class);

            return;

        case 'F':

            assert(pclass == float.class);

            return;

        case 'D':

            assert(pclass == double.class);

            return;

        }

        throw new InternalError("bad implicit conversion: tc="+ptype+": "+pclass);

    }

    /**

     * Emits an actual return instruction conforming to the given return type.

     */

    private void emitReturnInsn(Class<?> type) {

        int opcode;

        switch (Wrapper.basicTypeChar(type)) {

        case 'I':  opcode = Opcodes.IRETURN;  break;

        case 'J':  opcode = Opcodes.LRETURN;  break;

        case 'F':  opcode = Opcodes.FRETURN;  break;

        case 'D':  opcode = Opcodes.DRETURN;  break;

        case 'L':  opcode = Opcodes.ARETURN;  break;

        case 'V':  opcode = Opcodes.RETURN;   break;

        default:

            throw new InternalError("unknown return type: " + type);

        }

        mv.visitInsn(opcode);

    }

    private static String getInternalName(Class<?> c) {

        assert(VerifyAccess.isTypeVisible(c, Object.class));

        return c.getName().replace('.', '/');

    }

    /**

     * Generate customized bytecode for a given LambdaForm.

     *

     * @param form

     * @param invokerType

     * @return

     */

    static MemberName generateCustomizedCode(LambdaForm form, MethodType invokerType) {

        InvokerBytecodeGenerator g = new InvokerBytecodeGenerator("MH", form, invokerType);

        return g.loadMethod(g.generateCustomizedCodeBytes());

    }

    /**

     * Generate an invoker method for the passed {@link LambdaForm}.

     */

    private byte[] generateCustomizedCodeBytes() {

        classFilePrologue();

        // Suppress this method in backtraces displayed to the user.

        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);

        // Mark this method as a compiled LambdaForm

        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Compiled;", true);

        // iterate over the form's names, generating bytecode instructions for each

        // start iterating at the first name following the arguments

        for (int i = lambdaForm.arity; i < lambdaForm.names.length; i++) {

            Name name = lambdaForm.names[i];

            MemberName member = name.function.member();

            if (isSelectAlternative(member)) {

                // selectAlternative idiom

                // FIXME: make sure this idiom is really present!