/*

 * Copyright (c) 2011, 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.  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 jdk.internal.vm.annotation.DontInline;

import jdk.internal.vm.annotation.Stable;

import sun.invoke.util.Wrapper;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Arrays;

import java.util.HashMap;

import java.util.List;

import static java.lang.invoke.LambdaForm.BasicType.*;

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

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

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

/**

 * The symbolic, non-executable form of a method handle's invocation semantics.

 * It consists of a series of names.

 * The first N (N=arity) names are parameters,

 * while any remaining names are temporary values.

 * Each temporary specifies the application of a function to some arguments.

 * The functions are method handles, while the arguments are mixes of

 * constant values and local names.

 * The result of the lambda is defined as one of the names, often the last one.

 * <p>

 * Here is an approximate grammar:

 * <blockquote><pre>{@code

 * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"

 * ArgName = "a" N ":" T

 * TempName = "t" N ":" T "=" Function "(" Argument* ");"

 * Function = ConstantValue

 * Argument = NameRef | ConstantValue

 * Result = NameRef | "void"

 * NameRef = "a" N | "t" N

 * N = (any whole number)

 * T = "L" | "I" | "J" | "F" | "D" | "V"

 * }</pre></blockquote>

 * Names are numbered consecutively from left to right starting at zero.

 * (The letters are merely a taste of syntax sugar.)

 * Thus, the first temporary (if any) is always numbered N (where N=arity).

 * Every occurrence of a name reference in an argument list must refer to

 * a name previously defined within the same lambda.

 * A lambda has a void result if and only if its result index is -1.

 * If a temporary has the type "V", it cannot be the subject of a NameRef,

 * even though possesses a number.

 * Note that all reference types are erased to "L", which stands for {@code Object}.

 * All subword types (boolean, byte, short, char) are erased to "I" which is {@code int}.

 * The other types stand for the usual primitive types.

 * <p>

 * Function invocation closely follows the static rules of the Java verifier.

 * Arguments and return values must exactly match when their "Name" types are

 * considered.

 * Conversions are allowed only if they do not change the erased type.

 * <ul>

 * <li>L = Object: casts are used freely to convert into and out of reference types

 * <li>I = int: subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})

 * <li>J = long: no implicit conversions

 * <li>F = float: no implicit conversions

 * <li>D = double: no implicit conversions

 * <li>V = void: a function result may be void if and only if its Name is of type "V"

 * </ul>

 * Although implicit conversions are not allowed, explicit ones can easily be

 * encoded by using temporary expressions which call type-transformed identity functions.

 * <p>

 * Examples:

 * <blockquote><pre>{@code

 * (a0:J)=>{ a0 }

 *     == identity(long)

 * (a0:I)=>{ t1:V = System.out#println(a0); void }

 *     == System.out#println(int)

 * (a0:L)=>{ t1:V = System.out#println(a0); a0 }

 *     == identity, with printing side-effect

 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);

 *                 t3:L = BoundMethodHandle#target(a0);

 *                 t4:L = MethodHandle#invoke(t3, t2, a1); t4 }

 *     == general invoker for unary insertArgument combination

 * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);

 *                 t3:L = MethodHandle#invoke(t2, a1);

 *                 t4:L = FilterMethodHandle#target(a0);

 *                 t5:L = MethodHandle#invoke(t4, t3); t5 }

 *     == general invoker for unary filterArgument combination

 * (a0:L, a1:L)=>{ ...(same as previous example)...

 *                 t5:L = MethodHandle#invoke(t4, t3, a1); t5 }

 *     == general invoker for unary/unary foldArgument combination

 * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }

 *     == invoker for identity method handle which performs i2l

 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);

 *                 t3:L = Class#cast(t2,a1); t3 }

 *     == invoker for identity method handle which performs cast

 * }</pre></blockquote>

 * <p>

 * @author John Rose, JSR 292 EG

 */

class LambdaForm {

    final int arity;

    final int result;

    final boolean forceInline;

    final MethodHandle customized;

    @Stable final Name[] names;

    final String debugName;

    MemberName vmentry;   // low-level behavior, or null if not yet prepared

    private boolean isCompiled;

    // Either a LambdaForm cache (managed by LambdaFormEditor) or a link to uncustomized version (for customized LF)

    volatile Object transformCache;

    public static final int VOID_RESULT = -1, LAST_RESULT = -2;

    enum BasicType {

        L_TYPE('L', Object.class, Wrapper.OBJECT),  // all reference types

        I_TYPE('I', int.class,    Wrapper.INT),

        J_TYPE('J', long.class,   Wrapper.LONG),

        F_TYPE('F', float.class,  Wrapper.FLOAT),

        D_TYPE('D', double.class, Wrapper.DOUBLE),  // all primitive types

        V_TYPE('V', void.class,   Wrapper.VOID);    // not valid in all contexts

        static final BasicType[] ALL_TYPES = BasicType.values();

        static final BasicType[] ARG_TYPES = Arrays.copyOf(ALL_TYPES, ALL_TYPES.length-1);

        static final int ARG_TYPE_LIMIT = ARG_TYPES.length;

        static final int TYPE_LIMIT = ALL_TYPES.length;

        private final char btChar;

        private final Class<?> btClass;

        private final Wrapper btWrapper;

        private BasicType(char btChar, Class<?> btClass, Wrapper wrapper) {

            this.btChar = btChar;

            this.btClass = btClass;

            this.btWrapper = wrapper;

        }

        char basicTypeChar() {

            return btChar;

        }

        Class<?> basicTypeClass() {

            return btClass;

        }

        Wrapper basicTypeWrapper() {

            return btWrapper;

        }

        int basicTypeSlots() {

            return btWrapper.stackSlots();

        }

        static BasicType basicType(byte type) {

            return ALL_TYPES[type];

        }

        static BasicType basicType(char type) {

            switch (type) {

                case 'L': return L_TYPE;

                case 'I': return I_TYPE;

                case 'J': return J_TYPE;

                case 'F': return F_TYPE;

                case 'D': return D_TYPE;

                case 'V': return V_TYPE;

                // all subword types are represented as ints

                case 'Z':

                case 'B':

                case 'S':

                case 'C':

                    return I_TYPE;

                default:

                    throw newInternalError("Unknown type char: '"+type+"'");

            }

        }

        static BasicType basicType(Wrapper type) {

            char c = type.basicTypeChar();

            return basicType(c);

        }

        static BasicType basicType(Class<?> type) {

            if (!type.isPrimitive())  return L_TYPE;

            return basicType(Wrapper.forPrimitiveType(type));

        }

        static BasicType[] basicTypes(String types) {

            BasicType[] btypes = new BasicType[types.length()];

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

                btypes[i] = basicType(types.charAt(i));

            }

            return btypes;

        }

        static char basicTypeChar(Class<?> type) {

            return basicType(type).btChar;

        }

        static byte[] basicTypesOrd(Class<?>[] types) {

            byte[] ords = new byte[types.length];

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

                ords[i] = (byte)basicType(types[i]).ordinal();

            }

            return ords;

        }

        static boolean isBasicTypeChar(char c) {

            return "LIJFDV".indexOf(c) >= 0;

        }

        static boolean isArgBasicTypeChar(char c) {

            return "LIJFD".indexOf(c) >= 0;

        }

        static { assert(checkBasicType()); }

        private static boolean checkBasicType() {

            for (int i = 0; i < ARG_TYPE_LIMIT; i++) {

                assert ARG_TYPES[i].ordinal() == i;

                assert ARG_TYPES[i] == ALL_TYPES[i];

            }

            for (int i = 0; i < TYPE_LIMIT; i++) {

                assert ALL_TYPES[i].ordinal() == i;

            }

            assert ALL_TYPES[TYPE_LIMIT - 1] == V_TYPE;

            assert !Arrays.asList(ARG_TYPES).contains(V_TYPE);

            return true;

        }

    }

    LambdaForm(String debugName,

               int arity, Name[] names, int result) {

        this(debugName, arity, names, result, /*forceInline=*/true, /*customized=*/null);

    }

    LambdaForm(String debugName,

               int arity, Name[] names, int result, boolean forceInline, MethodHandle customized) {

        assert(namesOK(arity, names));

        this.arity = arity;

        this.result = fixResult(result, names);

        this.names = names.clone();

        this.debugName = fixDebugName(debugName);

        this.forceInline = forceInline;

        this.customized = customized;

        int maxOutArity = normalize();

        if (maxOutArity > MethodType.MAX_MH_INVOKER_ARITY) {

            // Cannot use LF interpreter on very high arity expressions.

            assert(maxOutArity <= MethodType.MAX_JVM_ARITY);

            compileToBytecode();

        }

    }

    LambdaForm(String debugName,

               int arity, Name[] names) {

        this(debugName, arity, names, LAST_RESULT, /*forceInline=*/true, /*customized=*/null);

    }

    LambdaForm(String debugName,

               int arity, Name[] names, boolean forceInline) {

        this(debugName, arity, names, LAST_RESULT, forceInline, /*customized=*/null);

    }

    LambdaForm(String debugName,

               Name[] formals, Name[] temps, Name result) {

        this(debugName,

             formals.length, buildNames(formals, temps, result), LAST_RESULT, /*forceInline=*/true, /*customized=*/null);

    }

    LambdaForm(String debugName,

               Name[] formals, Name[] temps, Name result, boolean forceInline) {

        this(debugName,

             formals.length, buildNames(formals, temps, result), LAST_RESULT, forceInline, /*customized=*/null);

    }

    private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {

        int arity = formals.length;

        int length = arity + temps.length + (result == null ? 0 : 1);

        Name[] names = Arrays.copyOf(formals, length);

        System.arraycopy(temps, 0, names, arity, temps.length);

        if (result != null)

            names[length - 1] = result;

        return names;

    }

    private LambdaForm(MethodType mt) {

        // Make a blank lambda form, which returns a constant zero or null.

        // It is used as a template for managing the invocation of similar forms that are non-empty.

        // Called only from getPreparedForm.

        this.arity = mt.parameterCount();

        this.result = (mt.returnType() == void.class || mt.returnType() == Void.class) ? -1 : arity;

        this.names = buildEmptyNames(arity, mt, result == -1);

        this.debugName = "LF.zero";

        this.forceInline = true;

        this.customized = null;

        assert(nameRefsAreLegal());

        assert(isEmpty());

        String sig = null;

        assert(isValidSignature(sig = basicTypeSignature()));

        assert(sig.equals(basicTypeSignature())) : sig + " != " + basicTypeSignature();

    }

    private static Name[] buildEmptyNames(int arity, MethodType mt, boolean isVoid) {

        Name[] names = arguments(isVoid ? 0 : 1, mt);

        if (!isVoid) {

            Name zero = new Name(constantZero(basicType(mt.returnType())));

            names[arity] = zero.newIndex(arity);

        }

        return names;

    }

    private static int fixResult(int result, Name[] names) {

        if (result == LAST_RESULT)

            result = names.length - 1;  // might still be void

        if (result >= 0 && names[result].type == V_TYPE)

            result = VOID_RESULT;

        return result;

    }

    private static String fixDebugName(String debugName) {

        if (DEBUG_NAME_COUNTERS != null) {

            int under = debugName.indexOf('_');

            int length = debugName.length();

            if (under < 0)  under = length;

            String debugNameStem = debugName.substring(0, under);

            Integer ctr;

            synchronized (DEBUG_NAME_COUNTERS) {

                ctr = DEBUG_NAME_COUNTERS.get(debugNameStem);

                if (ctr == null)  ctr = 0;

                DEBUG_NAME_COUNTERS.put(debugNameStem, ctr+1);

            }

            StringBuilder buf = new StringBuilder(debugNameStem);

            buf.append('_');

            int leadingZero = buf.length();

            buf.append((int) ctr);

            for (int i = buf.length() - leadingZero; i < 3; i++)

                buf.insert(leadingZero, '0');

            if (under < length) {

                ++under;    // skip "_"

                while (under < length && Character.isDigit(debugName.charAt(under))) {

                    ++under;

                }

                if (under < length && debugName.charAt(under) == '_')  ++under;

                if (under < length)

                    buf.append('_').append(debugName, under, length);

            }

            return buf.toString();

        }

        return debugName;

    }

    private static boolean namesOK(int arity, Name[] names) {

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

            Name n = names[i];

            assert(n != null) : "n is null";

            if (i < arity)

                assert( n.isParam()) : n + " is not param at " + i;

            else

                assert(!n.isParam()) : n + " is param at " + i;

        }

        return true;

    }

    /** Customize LambdaForm for a particular MethodHandle */

    LambdaForm customize(MethodHandle mh) {

        LambdaForm customForm = new LambdaForm(debugName, arity, names, result, forceInline, mh);

        if (COMPILE_THRESHOLD > 0 && isCompiled) {

            // If shared LambdaForm has been compiled, compile customized version as well.

            customForm.compileToBytecode();

        }

        customForm.transformCache = this; // LambdaFormEditor should always use uncustomized form.

        return customForm;

    }

    /** Get uncustomized flavor of the LambdaForm */

    LambdaForm uncustomize() {

        if (customized == null) {

            return this;

        }

        assert(transformCache != null); // Customized LambdaForm should always has a link to uncustomized version.

        LambdaForm uncustomizedForm = (LambdaForm)transformCache;

        if (COMPILE_THRESHOLD > 0 && isCompiled) {

            // If customized LambdaForm has been compiled, compile uncustomized version as well.

            uncustomizedForm.compileToBytecode();

        }

        return uncustomizedForm;

    }

    /** Renumber and/or replace params so that they are interned and canonically numbered.

     *  @return maximum argument list length among the names (since we have to pass over them anyway)

     */

    private int normalize() {

        Name[] oldNames = null;

        int maxOutArity = 0;

        int changesStart = 0;

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

            Name n = names[i];

            if (!n.initIndex(i)) {

                if (oldNames == null) {

                    oldNames = names.clone();

                    changesStart = i;

                }

                names[i] = n.cloneWithIndex(i);

            }

            if (n.arguments != null && maxOutArity < n.arguments.length)

                maxOutArity = n.arguments.length;

        }

        if (oldNames != null) {

            int startFixing = arity;

            if (startFixing <= changesStart)

                startFixing = changesStart+1;

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

                Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);

                names[i] = fixed.newIndex(i);

            }

        }

        assert(nameRefsAreLegal());

        int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);

        boolean needIntern = false;

        for (int i = 0; i < maxInterned; i++) {

            Name n = names[i], n2 = internArgument(n);

            if (n != n2) {

                names[i] = n2;

                needIntern = true;

            }

        }

        if (needIntern) {

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

                names[i].internArguments();

            }

        }

        assert(nameRefsAreLegal());

        return maxOutArity;

    }

    /**

     * Check that all embedded Name references are localizable to this lambda,

     * and are properly ordered after their corresponding definitions.

     * <p>

     * Note that a Name can be local to multiple lambdas, as long as

     * it possesses the same index in each use site.

     * This allows Name references to be freely reused to construct

     * fresh lambdas, without confusion.

     */

    boolean nameRefsAreLegal() {

        assert(arity >= 0 && arity <= names.length);

        assert(result >= -1 && result < names.length);

        // Do all names possess an index consistent with their local definition order?

        for (int i = 0; i < arity; i++) {

            Name n = names[i];

            assert(n.index() == i) : Arrays.asList(n.index(), i);

            assert(n.isParam());

        }

        // Also, do all local name references

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

            Name n = names[i];

            assert(n.index() == i);

            for (Object arg : n.arguments) {

                if (arg instanceof Name) {

                    Name n2 = (Name) arg;

                    int i2 = n2.index;

                    assert(0 <= i2 && i2 < names.length) : n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;

                    assert(names[i2] == n2) : Arrays.asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-", names[i2].debugString(), "-6-", this);

                    assert(i2 < i);  // ref must come after def!

                }

            }

        }

        return true;

    }

    /** Invoke this form on the given arguments. */

    // final Object invoke(Object... args) throws Throwable {

    //     // NYI: fit this into the fast path?

    //     return interpretWithArguments(args);

    // }

    /** Report the return type. */

    BasicType returnType() {

        if (result < 0)  return V_TYPE;

        Name n = names[result];

        return n.type;

    }

    /** Report the N-th argument type. */

    BasicType parameterType(int n) {

        return parameter(n).type;

    }

    /** Report the N-th argument name. */

    Name parameter(int n) {

        assert(n < arity);

        Name param = names[n];

        assert(param.isParam());

        return param;

    }