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 * 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.  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

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package com.sun.tools.javac.comp;

import com.sun.tools.javac.code.Symbol;

import com.sun.tools.javac.code.Symbol.OperatorSymbol;

import com.sun.tools.javac.code.Symtab;

import com.sun.tools.javac.code.Type;

import com.sun.tools.javac.code.Type.MethodType;

import com.sun.tools.javac.code.TypeTag;

import com.sun.tools.javac.code.Types;

import com.sun.tools.javac.jvm.ByteCodes;

import com.sun.tools.javac.resources.CompilerProperties.Errors;

import com.sun.tools.javac.tree.JCTree;

import com.sun.tools.javac.tree.JCTree.Tag;

import com.sun.tools.javac.util.Assert;

import com.sun.tools.javac.util.Context;

import com.sun.tools.javac.util.JCDiagnostic;

import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;

import com.sun.tools.javac.util.List;

import com.sun.tools.javac.util.Log;

import com.sun.tools.javac.util.Name;

import com.sun.tools.javac.util.Names;

import java.util.HashMap;

import java.util.Map;

import java.util.Optional;

import java.util.function.BiPredicate;

import java.util.function.Function;

import java.util.function.Predicate;

import java.util.function.Supplier;

import java.util.stream.Stream;

import static com.sun.tools.javac.jvm.ByteCodes.*;

import static com.sun.tools.javac.comp.Operators.OperatorType.*;

/**

 * This class contains the logic for unary and binary operator resolution/lookup.

 *

 * <p><b>This is NOT part of any supported API.

 * If you write code that depends on this, you do so at your own risk.

 * This code and its internal interfaces are subject to change or

 * deletion without notice.</b>

 */

public class Operators {

    protected static final Context.Key<Operators> operatorsKey = new Context.Key<>();

    private final Names names;

    private final Log log;

    private final Symtab syms;

    private final Types types;

    /** Unary operators map. */

    private Map<Name, List<UnaryOperatorHelper>> unaryOperators = new HashMap<>(Tag.getNumberOfOperators());

    /** Binary operators map. */

    private Map<Name, List<BinaryOperatorHelper>> binaryOperators = new HashMap<>(Tag.getNumberOfOperators());

    /** The names of all operators. */

    private Name[] opname = new Name[Tag.getNumberOfOperators()];

    public static Operators instance(Context context) {

        Operators instance = context.get(operatorsKey);

        if (instance == null)

            instance = new Operators(context);

        return instance;

    }

    protected Operators(Context context) {

        context.put(operatorsKey, this);

        syms = Symtab.instance(context);

        names = Names.instance(context);

        log = Log.instance(context);

        types = Types.instance(context);

        initOperatorNames();

        initUnaryOperators();

        initBinaryOperators();

    }

    /**

     * Perform unary promotion of a type; this routine implements JLS 5.6.1.

     * If the input type is not supported by unary promotion, it is returned unaltered.

     */

    Type unaryPromotion(Type t) {

        Type unboxed = types.unboxedTypeOrType(t);

        switch (unboxed.getTag()) {

            case BYTE:

            case SHORT:

            case CHAR:

                return syms.intType;

            default:

                return unboxed;

        }

    }

    /**

     * Perform binary promotion of a pair of types; this routine implements JLS 5.6.2.

     * If the input types are not supported by unary promotion, if such types are identical to

     * a type C, then C is returned, otherwise Object is returned.

     */

    Type binaryPromotion(Type t1, Type t2) {

        Type unboxedT1 = types.unboxedTypeOrType(t1);

        Type unboxedT2 = types.unboxedTypeOrType(t2);

        if (unboxedT1.isNumeric() && unboxedT2.isNumeric()) {

            if (unboxedT1.hasTag(TypeTag.DOUBLE) || unboxedT2.hasTag(TypeTag.DOUBLE)) {

                return syms.doubleType;

            } else if (unboxedT1.hasTag(TypeTag.FLOAT) || unboxedT2.hasTag(TypeTag.FLOAT)) {

                return syms.floatType;

            } else if (unboxedT1.hasTag(TypeTag.LONG) || unboxedT2.hasTag(TypeTag.LONG)) {

                return syms.longType;

            } else {

                return syms.intType;

            }

        } else if (types.isSameType(unboxedT1, unboxedT2)) {

            return unboxedT1;

        } else {

            return syms.objectType;

        }

    }

    /**

     * Entry point for resolving a unary operator given an operator tag and an argument type.

     */

    Symbol resolveUnary(DiagnosticPosition pos, JCTree.Tag tag, Type op) {

        return resolve(tag,

                unaryOperators,

                unop -> unop.test(op),

                unop -> unop.resolve(op),

                () -> reportErrorIfNeeded(pos, tag, op));

    }

    /**

     * Entry point for resolving a binary operator given an operator tag and a pair of argument types.

     */

    Symbol resolveBinary(DiagnosticPosition pos, JCTree.Tag tag, Type op1, Type op2) {

        return resolve(tag,

                binaryOperators,

                binop -> binop.test(op1, op2),

                binop -> binop.resolve(op1, op2),

                () -> reportErrorIfNeeded(pos, tag, op1, op2));

    }

    /**

     * Main operator lookup routine; lookup an operator (either unary or binary) in its corresponding

     * map. If there's a matching operator, its resolve routine is called and the result is returned;

     * otherwise the result of a fallback function is returned.

     */

    private <O> Symbol resolve(Tag tag, Map<Name, List<O>> opMap, Predicate<O> opTestFunc,

                       Function<O, Symbol> resolveFunc, Supplier<Symbol> noResultFunc) {

        return opMap.get(operatorName(tag)).stream()

                .filter(opTestFunc)

                .map(resolveFunc)

                .findFirst()

                .orElseGet(noResultFunc);

    }

    /**

     * Creates an operator symbol.

     */

    private Symbol makeOperator(Name name, List<OperatorType> formals, OperatorType res, int... opcodes) {

        MethodType opType = new MethodType(

                formals.stream()

                        .map(o -> o.asType(syms))

                        .collect(List.collector()),

                res.asType(syms), List.nil(), syms.methodClass);

        return new OperatorSymbol(name, opType, mergeOpcodes(opcodes), syms.noSymbol);

    }

    /**

     * Fold two opcodes in a single int value (if required).

     */

    private int mergeOpcodes(int... opcodes) {

        int opcodesLen = opcodes.length;

        Assert.check(opcodesLen == 1 || opcodesLen == 2);

        return (opcodesLen == 1) ?

                opcodes[0] :

                ((opcodes[0] << ByteCodes.preShift) | opcodes[1]);

    }

    /**

     * Report an operator lookup error.

     */

    private Symbol reportErrorIfNeeded(DiagnosticPosition pos, Tag tag, Type... args) {

        if (Stream.of(args).noneMatch(Type::isErroneous)) {

            Name opName = operatorName(tag);

            JCDiagnostic.Error opError = (args.length) == 1 ?

                    Errors.OperatorCantBeApplied(opName, args[0]) :

                    Errors.OperatorCantBeApplied1(opName, args[0], args[1]);

            log.error(pos, opError);

        }

        return syms.noSymbol;

    }

    /**

     * Return name of operator with given tree tag.

     */

    public Name operatorName(JCTree.Tag tag) {

        return opname[tag.operatorIndex()];

    }

    /**

     * The constants in this enum represent the types upon which all the operator helpers

     * operate upon. This allows lazy and consise mapping between a type name and a type instance.

     */

    enum OperatorType {

        BYTE(syms -> syms.byteType),

        SHORT(syms -> syms.shortType),

        INT(syms -> syms.intType),

        LONG(syms -> syms.longType),

        FLOAT(syms -> syms.floatType),

        DOUBLE(syms -> syms.doubleType),

        CHAR(syms -> syms.charType),

        BOOLEAN(syms -> syms.booleanType),

        OBJECT(syms -> syms.objectType),

        STRING(syms -> syms.stringType),

        BOT(syms -> syms.botType);

        final Function<Symtab, Type> asTypeFunc;

        OperatorType(Function<Symtab, Type> asTypeFunc) {

            this.asTypeFunc = asTypeFunc;

        }

        Type asType(Symtab syms) {

            return asTypeFunc.apply(syms);

        }

    }

    /**

     * Common root for all operator helpers. An operator helper instance is associated with a

     * given operator (i.e. '+'); it contains routines to perform operator lookup, i.e. find

     * which version of the '+' operator is the best given an argument type list. Supported

     * operator symbols are initialized lazily upon first lookup request - this is in order to avoid

     * initialization circularities between this class and {@code Symtab}.

     */

    abstract class OperatorHelper {

        /** The operator name. */

        final Name name;

        /** The list of symbols associated with this operator (lazily populated). */

        Optional<Symbol[]> alternatives = Optional.empty();

        /** An array of operator symbol suppliers (used to lazily populate the symbol list). */

        List<Supplier<Symbol>> operatorSuppliers = List.nil();

        @SuppressWarnings("varargs")

        OperatorHelper(Tag tag) {

            this.name = operatorName(tag);

        }

        /**

         * This routine implements the main operator lookup process. Each operator is tested

         * using an applicability predicate; if the test suceeds that same operator is returned,

         * otherwise a dummy symbol is returned.

         */

        final Symbol doLookup(Predicate<Symbol> applicabilityTest) {

            return Stream.of(alternatives.orElseGet(this::initOperators))

                    .filter(applicabilityTest)

                    .findFirst()

                    .orElse(syms.noSymbol);

        }

        /**

         * This routine performs lazy instantiation of the operator symbols supported by this helper.

         * After initialization is done, the suppliers are cleared, to free up memory.

         */

        private Symbol[] initOperators() {

            Symbol[] operators = operatorSuppliers.stream()

                    .map(op -> op.get())

                    .toArray(Symbol[]::new);

            alternatives = Optional.of(operators);

            operatorSuppliers = null; //let GC do its work

            return operators;

        }

    }

    /**

     * Common superclass for all unary operator helpers.

     */

    abstract class UnaryOperatorHelper extends OperatorHelper implements Predicate<Type> {

        UnaryOperatorHelper(Tag tag) {

            super(tag);

        }

        /**

         * This routine implements the unary operator lookup process. It customizes the behavior

         * of the shared lookup routine in {@link OperatorHelper}, by using an unary applicability test

         * (see {@link UnaryOperatorHelper#isUnaryOperatorApplicable(OperatorSymbol, Type)}

         */

        final Symbol doLookup(Type t) {

            return doLookup(op -> isUnaryOperatorApplicable((OperatorSymbol)op, t));

        }

        /**

         * Unary operator applicability test - is the input type the same as the expected operand type?

         */

        boolean isUnaryOperatorApplicable(OperatorSymbol op, Type t) {

            return types.isSameType(op.type.getParameterTypes().head, t);

        }

        /**

         * Adds a unary operator symbol.

         */

        final UnaryOperatorHelper addUnaryOperator(OperatorType arg, OperatorType res, int... opcode) {

            operatorSuppliers = operatorSuppliers.prepend(() -> makeOperator(name, List.of(arg), res, opcode));

            return this;

        }

        /**

         * This method will be overridden by unary operator helpers to provide custom resolution

         * logic.

         */

        abstract Symbol resolve(Type t);

    }

    abstract class BinaryOperatorHelper extends OperatorHelper implements BiPredicate<Type, Type> {

        BinaryOperatorHelper(Tag tag) {

            super(tag);

        }

        /**

         * This routine implements the binary operator lookup process. It customizes the behavior

         * of the shared lookup routine in {@link OperatorHelper}, by using an unary applicability test

         * (see {@link BinaryOperatorHelper#isBinaryOperatorApplicable(OperatorSymbol, Type, Type)}

         */

        final Symbol doLookup(Type t1, Type t2) {

            return doLookup(op -> isBinaryOperatorApplicable((OperatorSymbol)op, t1, t2));

        }

        /**

         * Binary operator applicability test - are the input types the same as the expected operand types?

         */

        boolean isBinaryOperatorApplicable(OperatorSymbol op, Type t1, Type t2) {

            List<Type> formals = op.type.getParameterTypes();

            return types.isSameType(formals.head, t1) &&

                    types.isSameType(formals.tail.head, t2);

        }

        /**

         * Adds a binary operator symbol.

         */

        final BinaryOperatorHelper addBinaryOperator(OperatorType arg1, OperatorType arg2, OperatorType res, int... opcode) {

            operatorSuppliers = operatorSuppliers.prepend(() -> makeOperator(name, List.of(arg1, arg2), res, opcode));

            return this;

        }

        /**

         * This method will be overridden by binary operator helpers to provide custom resolution

         * logic.

         */

        abstract Symbol resolve(Type t1, Type t2);

    }

    /**

     * Class representing unary operator helpers that operate on reference types.

     */

    class UnaryReferenceOperator extends UnaryOperatorHelper {

        UnaryReferenceOperator(Tag tag) {

            super(tag);

        }

        @Override

        public boolean test(Type type) {

            return type.isNullOrReference();

        }

        @Override

        public Symbol resolve(Type arg) {

            return doLookup(syms.objectType);

        }

    }

    /**

     * Class representing unary operator helpers that operate on numeric types (either boxed or unboxed).

     * Operator lookup is performed after applying numeric promotion of the input type.

     */

    class UnaryNumericOperator extends UnaryOperatorHelper {

        UnaryNumericOperator(Tag tag) {

            super(tag);

        }

        @Override

        public boolean test(Type type) {

            return unaryPromotion(type).isNumeric();

        }

        @Override

        public Symbol resolve(Type arg) {

            return doLookup(unaryPromotion(arg));

        }

    }

    /**

     * Class representing unary operator helpers that operate on boolean types  (either boxed or unboxed).

     * Operator lookup is performed assuming the input type is a boolean type.

     */

    class UnaryBooleanOperator extends UnaryOperatorHelper {

        UnaryBooleanOperator(Tag tag) {

            super(tag);

        }

        @Override

        public boolean test(Type type) {

            return types.unboxedTypeOrType(type).hasTag(TypeTag.BOOLEAN);

        }

        @Override

        public Symbol resolve(Type arg) {

            return doLookup(syms.booleanType);

        }

    }

    /**

     * Class representing prefix/postfix unary operator helpers. Operates on numeric types (either

     * boxed or unboxed). Operator lookup is performed on the unboxed version of the input type.

     */

    class UnaryPrefixPostfixOperator extends UnaryNumericOperator {

        UnaryPrefixPostfixOperator(Tag tag) {

            super(tag);

        }

        @Override

        public Symbol resolve(Type arg) {

            return doLookup(types.unboxedTypeOrType(arg));

        }

    }

    /**

     * Class representing binary operator helpers that operate on numeric types (either boxed or unboxed).

     * Operator lookup is performed after applying binary numeric promotion of the input types.

     */

    class BinaryNumericOperator extends BinaryOperatorHelper {

        BinaryNumericOperator(Tag tag) {

            super(tag);

        }

        @Override

        public Symbol resolve(Type arg1, Type arg2) {

            Type t = binaryPromotion(arg1, arg2);

            return doLookup(t, t);

        }

        @Override

        public boolean test(Type arg1, Type arg2) {

            return unaryPromotion(arg1).isNumeric() && unaryPromotion(arg2).isNumeric();

        }

    }

    /**

     * Class representing bitwise operator helpers that operate on boolean types (either boxed or unboxed).

     * Operator lookup is performed assuming both input types are boolean types.

     */

    class BinaryBooleanOperator extends BinaryOperatorHelper {

        BinaryBooleanOperator(Tag tag) {

            super(tag);

        }

        @Override

        public Symbol resolve(Type arg1, Type arg2) {

            return doLookup(syms.booleanType, syms.booleanType);

        }

        @Override

        public boolean test(Type arg1, Type arg2) {

            return types.unboxedTypeOrType(arg1).hasTag(TypeTag.BOOLEAN) &&

                    types.unboxedTypeOrType(arg2).hasTag(TypeTag.BOOLEAN);

        }

    }

    /**

     * Class representing string concatenation operator helper that operates on at least an

     * string operand. Input types subject to an operator lookup undergoes a special string promotion

     * (see {@link BinaryStringOperator#stringPromotion(Type)}.

     */

    class BinaryStringOperator extends BinaryOperatorHelper {

        BinaryStringOperator(Tag tag) {

            super(tag);

        }

        @Override

        public Symbol resolve(Type arg1, Type arg2) {

            return doLookup(stringPromotion(arg1), stringPromotion(arg2));

        }

        @Override

        public boolean test(Type arg1, Type arg2) {

            return types.isSameType(arg1, syms.stringType) ||

                    types.isSameType(arg2, syms.stringType);

        }

        /**

         * This routine applies following mappings:

         * - if input type is primitive, apply numeric promotion

         * - if input type is either 'null' or 'String' leave it untouched