/*

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.tools.javac.comp;

import com.sun.source.tree.LambdaExpressionTree.BodyKind;

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

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

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

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

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

import com.sun.tools.javac.comp.Attr.ResultInfo;

import com.sun.tools.javac.comp.Attr.TargetInfo;

import com.sun.tools.javac.comp.Check.CheckContext;

import com.sun.tools.javac.comp.DeferredAttr.AttrMode;

import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;

import com.sun.tools.javac.comp.DeferredAttr.DeferredType;

import com.sun.tools.javac.comp.DeferredAttr.DeferredTypeCompleter;

import com.sun.tools.javac.comp.DeferredAttr.LambdaReturnScanner;

import com.sun.tools.javac.comp.Infer.PartiallyInferredMethodType;

import com.sun.tools.javac.comp.Resolve.MethodResolutionPhase;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

import java.util.HashMap;

import java.util.LinkedHashMap;

import java.util.Map;

import java.util.Optional;

import java.util.function.Function;

import java.util.function.Supplier;

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

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

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

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

/**

 * This class performs attribution of method/constructor arguments when target-typing is enabled

 * (source >= 8); for each argument that is potentially a poly expression, this class builds

 * a rich representation (see {@link ArgumentType} which can then be used for performing fast overload

 * checks without requiring multiple attribution passes over the same code.

 *

 * The attribution strategy for a given method/constructor argument A is as follows:

 *

 * - if A is potentially a poly expression (i.e. diamond instance creation expression), a speculative

 * pass over A is performed; the results of such speculative attribution are then saved in a special

 * type, so that enclosing overload resolution can be carried by simply checking compatibility against the

 * type determined during this speculative pass.

 *

 * - if A is a standalone expression, regular atributtion takes place.

 *

 * To minimize the speculative work, a cache is used, so that already computed argument types

 * associated with a given unique source location are never recomputed multiple times.

 */

public class ArgumentAttr extends JCTree.Visitor {

    protected static final Context.Key<ArgumentAttr> methodAttrKey = new Context.Key<>();

    private final DeferredAttr deferredAttr;

    private final Attr attr;

    private final Symtab syms;

    private final Log log;

    /** Attribution environment to be used. */

    private Env<AttrContext> env;

    /** Result of method attribution. */

    private Type result;

    /** Cache for argument types; behavior is influences by the currrently selected cache policy. */

    Map<UniquePos, ArgumentType<?>> argumentTypeCache = new LinkedHashMap<>();

    public static ArgumentAttr instance(Context context) {

        ArgumentAttr instance = context.get(methodAttrKey);

        if (instance == null)

            instance = new ArgumentAttr(context);

        return instance;

    }

    protected ArgumentAttr(Context context) {

        context.put(methodAttrKey, this);

        deferredAttr = DeferredAttr.instance(context);

        attr = Attr.instance(context);

        syms = Symtab.instance(context);

        log = Log.instance(context);

    }

    /**

     * Set the results of method attribution.

     */

    void setResult(JCExpression tree, Type type) {

        result = type;

        if (env.info.isSpeculative) {

            //if we are in a speculative branch we can save the type in the tree itself

            //as there's no risk of polluting the original tree.

            tree.type = result;

        }

    }

    /**

     * Checks a type in the speculative tree against a given result; the type can be either a plain

     * type or an argument type,in which case a more complex check is required.

     */

    Type checkSpeculative(JCExpression expr, ResultInfo resultInfo) {

        return checkSpeculative(expr, expr.type, resultInfo);

    }

    /**

     * Checks a type in the speculative tree against a given result; the type can be either a plain

     * type or an argument type,in which case a more complex check is required.

     */

    Type checkSpeculative(DiagnosticPosition pos, Type t, ResultInfo resultInfo) {

        if (t.hasTag(DEFERRED)) {

            return ((DeferredType)t).check(resultInfo);

        } else {

            return resultInfo.check(pos, t);

        }

    }

    /**

     * Returns a local caching context in which argument types can safely be cached without

     * the risk of polluting enclosing contexts. This is useful when attempting speculative

     * attribution of potentially erroneous expressions, which could end up polluting the cache.

     */

    LocalCacheContext withLocalCacheContext() {

        return new LocalCacheContext();

    }

    /**

     * Local cache context; this class keeps track of the previous cache and reverts to it

     * when the {@link LocalCacheContext#leave()} method is called.

     */

    class LocalCacheContext {

        Map<UniquePos, ArgumentType<?>> prevCache;

        public LocalCacheContext() {

            this.prevCache = argumentTypeCache;

            argumentTypeCache = new HashMap<>();

        }

        public void leave() {

            argumentTypeCache = prevCache;

        }

    }

    /**

     * Main entry point for attributing an argument with given tree and attribution environment.

     */

    Type attribArg(JCTree tree, Env<AttrContext> env) {

        Env<AttrContext> prevEnv = this.env;

        try {

            this.env = env;

            tree.accept(this);

            return result;

        } finally {

            this.env = prevEnv;

        }

    }

    @Override

    public void visitTree(JCTree that) {

        //delegates to Attr

        that.accept(attr);

        result = attr.result;

    }

    /**

     * Process a method argument; this method takes care of performing a speculative pass over the

     * argument tree and calling a well-defined entry point to build the argument type associated

     * with such tree.

     */

    @SuppressWarnings("unchecked")

    <T extends JCExpression, Z extends ArgumentType<T>> void processArg(T that, Function<T, Z> argumentTypeFactory) {

        UniquePos pos = new UniquePos(that);

        processArg(that, () -> {

            T speculativeTree = (T)deferredAttr.attribSpeculative(that, env, attr.new MethodAttrInfo() {

                @Override

                protected void attr(JCTree tree, Env<AttrContext> env) {

                    //avoid speculative attribution loops

                    if (!new UniquePos(tree).equals(pos)) {

                        super.attr(tree, env);

                    } else {

                        visitTree(tree);

                    }

                }

            });

            return argumentTypeFactory.apply(speculativeTree);

        });

    }

    /**

     * Process a method argument; this method allows the caller to specify a custom speculative attribution

     * logic (this is used e.g. for lambdas).

     */

    @SuppressWarnings("unchecked")

    <T extends JCExpression, Z extends ArgumentType<T>> void processArg(T that, Supplier<Z> argumentTypeFactory) {

        UniquePos pos = new UniquePos(that);

        Z cached = (Z)argumentTypeCache.get(pos);

        if (cached != null) {

            //dup existing speculative type

            setResult(that, cached.dup(that, env));

        } else {

            Z res = argumentTypeFactory.get();

            argumentTypeCache.put(pos, res);

            setResult(that, res);

        }

    }

    @Override

    public void visitParens(JCParens that) {

        processArg(that, speculativeTree -> new ParensType(that, env, speculativeTree));

    }

    @Override

    public void visitConditional(JCConditional that) {

        processArg(that, speculativeTree -> new ConditionalType(that, env, speculativeTree));

    }

    @Override

    public void visitReference(JCMemberReference tree) {

        //perform arity-based check

        Env<AttrContext> localEnv = env.dup(tree);

        JCExpression exprTree = (JCExpression)deferredAttr.attribSpeculative(tree.getQualifierExpression(), localEnv,

                attr.memberReferenceQualifierResult(tree));

        JCMemberReference mref2 = new TreeCopier<Void>(attr.make).copy(tree);

        mref2.expr = exprTree;

        Symbol lhsSym = TreeInfo.symbol(exprTree);

        localEnv.info.selectSuper = lhsSym != null && lhsSym.name == lhsSym.name.table.names._super;

        Symbol res =

                attr.rs.getMemberReference(tree, localEnv, mref2,

                        exprTree.type, tree.name);

        if (!res.kind.isResolutionError()) {

            tree.sym = res;

        }

        if (res.kind.isResolutionTargetError() ||

                res.type != null && res.type.hasTag(FORALL) ||

                (res.flags() & Flags.VARARGS) != 0 ||

                (TreeInfo.isStaticSelector(exprTree, tree.name.table.names) &&

            tree.overloadKind = JCMemberReference.OverloadKind.OVERLOADED;

        } else {

            tree.overloadKind = JCMemberReference.OverloadKind.UNOVERLOADED;

        }

        //return a plain old deferred type for this

        setResult(tree, deferredAttr.new DeferredType(tree, env));

    }

    @Override

    public void visitLambda(JCLambda that) {

        if (that.paramKind == ParameterKind.EXPLICIT) {

            //if lambda is explicit, we can save info in the corresponding argument type

            processArg(that, () -> {

                JCLambda speculativeLambda =

                        deferredAttr.attribSpeculativeLambda(that, env, attr.methodAttrInfo);

                return new ExplicitLambdaType(that, env, speculativeLambda);

            });

        } else {

            //otherwise just use a deferred type

            setResult(that, deferredAttr.new DeferredType(that, env));

        }

    }

    @Override

    public void visitApply(JCMethodInvocation that) {

        if (that.getTypeArguments().isEmpty()) {

            processArg(that, speculativeTree -> new ResolvedMethodType(that, env, speculativeTree));

        } else {

            //not a poly expression, just call Attr

            setResult(that, attr.attribTree(that, env, attr.unknownExprInfo));

        }

    }

    @Override

    public void visitNewClass(JCNewClass that) {

        if (TreeInfo.isDiamond(that)) {

            processArg(that, speculativeTree -> new ResolvedConstructorType(that, env, speculativeTree));

        } else {

            //not a poly expression, just call Attr

            setResult(that, attr.attribTree(that, env, attr.unknownExprInfo));

        }

    }

    /**

     * An argument type is similar to a plain deferred type; the most important difference is that

     * the completion logic associated with argument types allows speculative attribution to be skipped

     * during overload resolution - that is, an argument type always has enough information to

     * perform an overload check without the need of calling back to Attr. This extra information

     * is typically stored in the form of a speculative tree.

     */

    abstract class ArgumentType<T extends JCExpression> extends DeferredType implements DeferredTypeCompleter {

        /** The speculative tree carrying type information. */

        T speculativeTree;

        /** Types associated with this argument (one type per possible target result). */

        Map<ResultInfo, Type> speculativeTypes;

        public ArgumentType(JCExpression tree, Env<AttrContext> env, T speculativeTree, Map<ResultInfo, Type> speculativeTypes) {

            deferredAttr.super(tree, env);

            this.speculativeTree = speculativeTree;

            this.speculativeTypes = speculativeTypes;

        }

        @Override

        final DeferredTypeCompleter completer() {

            return this;

        }

        @Override

        final public Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {

            Assert.check(dt == this);

            if (deferredAttrContext.mode == AttrMode.SPECULATIVE) {

                Type t = (resultInfo.pt == Type.recoveryType) ?

                        deferredAttr.basicCompleter.complete(dt, resultInfo, deferredAttrContext) :

                        overloadCheck(resultInfo, deferredAttrContext);

                speculativeTypes.put(resultInfo, t);

                return t;

            } else {

                if (!env.info.isSpeculative) {

                    argumentTypeCache.remove(new UniquePos(dt.tree));

                }

                return deferredAttr.basicCompleter.complete(dt, resultInfo, deferredAttrContext);

            }

        }

        @Override

        Type speculativeType(Symbol msym, MethodResolutionPhase phase) {

            for (Map.Entry<ResultInfo, Type> _entry : speculativeTypes.entrySet()) {

                DeferredAttrContext deferredAttrContext = _entry.getKey().checkContext.deferredAttrContext();

                if (deferredAttrContext.phase == phase && deferredAttrContext.msym == msym) {

                    return _entry.getValue();

                }

            }

            return Type.noType;

        }

        @Override

        JCTree speculativeTree(DeferredAttrContext deferredAttrContext) {

            return speculativeTree;

        }

        /**

         * Performs an overload check against a given target result.

         */

        abstract Type overloadCheck(ResultInfo resultInfo, DeferredAttrContext deferredAttrContext);

        /**

         * Creates a copy of this argument type with given tree and environment.

         */

        abstract ArgumentType<T> dup(T tree, Env<AttrContext> env);

    }

    /**

     * Argument type for parenthesized expression.

     */

    class ParensType extends ArgumentType<JCParens> {

        ParensType(JCExpression tree, Env<AttrContext> env, JCParens speculativeParens) {

            this(tree, env, speculativeParens, new HashMap<>());

        }

        ParensType(JCExpression tree, Env<AttrContext> env, JCParens speculativeParens, Map<ResultInfo, Type> speculativeTypes) {

           super(tree, env, speculativeParens, speculativeTypes);

        }

        @Override

        Type overloadCheck(ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {

            return checkSpeculative(speculativeTree.expr, resultInfo);

        }

        @Override

        ArgumentType<JCParens> dup(JCParens tree, Env<AttrContext> env) {

            return new ParensType(tree, env, speculativeTree, speculativeTypes);

        }

    }

    /**

     * Argument type for conditionals.

     */

    class ConditionalType extends ArgumentType<JCConditional> {

        ConditionalType(JCExpression tree, Env<AttrContext> env, JCConditional speculativeCond) {

            this(tree, env, speculativeCond, new HashMap<>());

        }

        ConditionalType(JCExpression tree, Env<AttrContext> env, JCConditional speculativeCond, Map<ResultInfo, Type> speculativeTypes) {

           super(tree, env, speculativeCond, speculativeTypes);

        }

        @Override

        Type overloadCheck(ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {

            ResultInfo localInfo = resultInfo.dup(attr.conditionalContext(resultInfo.checkContext));

            if (speculativeTree.isStandalone()) {

                return localInfo.check(speculativeTree, speculativeTree.type);

            } else if (resultInfo.pt.hasTag(VOID)) {

                //this means we are returning a poly conditional from void-compatible lambda expression

                resultInfo.checkContext.report(tree, attr.diags.fragment("conditional.target.cant.be.void"));

                return attr.types.createErrorType(resultInfo.pt);

            } else {

                //poly

                checkSpeculative(speculativeTree.truepart, localInfo);

                checkSpeculative(speculativeTree.falsepart, localInfo);

                return localInfo.pt;

            }

        }

        @Override

        ArgumentType<JCConditional> dup(JCConditional tree, Env<AttrContext> env) {

            return new ConditionalType(tree, env, speculativeTree, speculativeTypes);

        }

    }

    /**

     * Argument type for explicit lambdas.

     */

    class ExplicitLambdaType extends ArgumentType<JCLambda> {

        /** List of argument types (lazily populated). */

        Optional<List<Type>> argtypes = Optional.empty();

        /** List of return expressions (lazily populated). */

        Optional<List<JCReturn>> returnExpressions = Optional.empty();

        ExplicitLambdaType(JCLambda originalLambda, Env<AttrContext> env, JCLambda speculativeLambda) {

            this(originalLambda, env, speculativeLambda, new HashMap<>());

        }

        ExplicitLambdaType(JCLambda originalLambda, Env<AttrContext> env, JCLambda speculativeLambda, Map<ResultInfo, Type> speculativeTypes) {

            super(originalLambda, env, speculativeLambda, speculativeTypes);

        }

        /** Compute argument types (if needed). */

        List<Type> argtypes() {

            return argtypes.orElseGet(() -> {

                List<Type> res = TreeInfo.types(speculativeTree.params);

                argtypes = Optional.of(res);

                return res;

            });

        }

        /** Compute return expressions (if needed). */

        List<JCReturn> returnExpressions() {

            return returnExpressions.orElseGet(() -> {

                final List<JCReturn> res;

                if (speculativeTree.getBodyKind() == BodyKind.EXPRESSION) {

                    res = List.of(attr.make.Return((JCExpression)speculativeTree.body));

                } else {

                    ListBuffer<JCReturn> returnExpressions = new ListBuffer<>();

                    new LambdaReturnScanner() {

                        @Override

                        public void visitReturn(JCReturn tree) {

                            returnExpressions.add(tree);

                        }

                    }.scan(speculativeTree.body);

                    res = returnExpressions.toList();

                }

                returnExpressions = Optional.of(res);

                return res;

            });

        }

        @Override

        Type overloadCheck(ResultInfo resultInfo, DeferredAttrContext deferredAttrContext) {

            try {

                //compute target-type; this logic could be shared with Attr

                TargetInfo targetInfo = attr.getTargetInfo(speculativeTree, resultInfo, argtypes());

                Type lambdaType = targetInfo.descriptor;

                Type currentTarget = targetInfo.target;

                //check compatibility

                checkLambdaCompatible(lambdaType, resultInfo);

                return currentTarget;

            } catch (FunctionDescriptorLookupError ex) {

                resultInfo.checkContext.report(null, ex.getDiagnostic());

                return null; //cannot get here

            }

        }

        /** Check lambda against given target result */

        private void checkLambdaCompatible(Type descriptor, ResultInfo resultInfo) {

            CheckContext checkContext = resultInfo.checkContext;

            ResultInfo bodyResultInfo = attr.lambdaBodyResult(speculativeTree, descriptor, resultInfo);

            for (JCReturn ret : returnExpressions()) {

                Type t = getReturnType(ret);

                if (speculativeTree.getBodyKind() == BodyKind.EXPRESSION || !t.hasTag(VOID)) {

                    checkSpeculative(ret.expr, t, bodyResultInfo);

                }

            }