/*

 * Copyright (c) 2012, 2017, 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.source.tree.NewClassTree;

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

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

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

import com.sun.tools.javac.comp.ArgumentAttr.LocalCacheContext;

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

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

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

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

import com.sun.tools.javac.util.DefinedBy.Api;

import com.sun.tools.javac.util.GraphUtils.DependencyKind;

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

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

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

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

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

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

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

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

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;

import java.util.EnumSet;

import java.util.HashSet;

import java.util.LinkedHashSet;

import java.util.Map;

import java.util.Set;

import java.util.WeakHashMap;

import java.util.function.Function;

import com.sun.source.tree.MemberReferenceTree;

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

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

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

/**

 * This is an helper class that is used to perform deferred type-analysis.

 * Each time a poly expression occurs in argument position, javac attributes it

 * with a temporary 'deferred type' that is checked (possibly multiple times)

 * against an expected formal type.

 *

 *  <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 DeferredAttr extends JCTree.Visitor {

    protected static final Context.Key<DeferredAttr> deferredAttrKey = new Context.Key<>();

    final Attr attr;

    final ArgumentAttr argumentAttr;

    final Check chk;

    final JCDiagnostic.Factory diags;

    final Enter enter;

    final Infer infer;

    final Resolve rs;

    final Log log;

    final Symtab syms;

    final TreeMaker make;

    final TreeCopier<Void> treeCopier;

    final TypeMapping<Void> deferredCopier;

    final Types types;

    final Flow flow;

    final Names names;

    final TypeEnvs typeEnvs;

    public static DeferredAttr instance(Context context) {

        DeferredAttr instance = context.get(deferredAttrKey);

        if (instance == null)

            instance = new DeferredAttr(context);

        return instance;

    }

    protected DeferredAttr(Context context) {

        context.put(deferredAttrKey, this);

        attr = Attr.instance(context);

        argumentAttr = ArgumentAttr.instance(context);

        chk = Check.instance(context);

        diags = JCDiagnostic.Factory.instance(context);

        enter = Enter.instance(context);

        infer = Infer.instance(context);

        rs = Resolve.instance(context);

        log = Log.instance(context);

        syms = Symtab.instance(context);

        make = TreeMaker.instance(context);

        types = Types.instance(context);

        flow = Flow.instance(context);

        names = Names.instance(context);

        stuckTree = make.Ident(names.empty).setType(Type.stuckType);

        typeEnvs = TypeEnvs.instance(context);

        emptyDeferredAttrContext =

            new DeferredAttrContext(AttrMode.CHECK, null, MethodResolutionPhase.BOX, infer.emptyContext, null, null) {

                @Override

                void addDeferredAttrNode(DeferredType dt, ResultInfo ri, DeferredStuckPolicy deferredStuckPolicy) {

                    Assert.error("Empty deferred context!");

                }

                @Override

                void complete() {

                    Assert.error("Empty deferred context!");

                }

                @Override

                public String toString() {

                    return "Empty deferred context!";

                }

            };

        // For speculative attribution, skip the class definition in <>.

        treeCopier =

            new TreeCopier<Void>(make) {

                @Override @DefinedBy(Api.COMPILER_TREE)

                public JCTree visitNewClass(NewClassTree node, Void p) {

                    JCNewClass t = (JCNewClass) node;

                    if (TreeInfo.isDiamond(t)) {

                        JCExpression encl = copy(t.encl, p);

                        List<JCExpression> typeargs = copy(t.typeargs, p);

                        JCExpression clazz = copy(t.clazz, p);

                        List<JCExpression> args = copy(t.args, p);

                        JCClassDecl def = null;

                        return make.at(t.pos).NewClass(encl, typeargs, clazz, args, def);

                    } else {

                        return super.visitNewClass(node, p);

                    }

                }

                @Override @DefinedBy(Api.COMPILER_TREE)

                public JCTree visitMemberReference(MemberReferenceTree node, Void p) {

                    JCMemberReference t = (JCMemberReference) node;

                    JCExpression expr = copy(t.expr, p);

                    List<JCExpression> typeargs = copy(t.typeargs, p);

                    /** once the value for overloadKind is determined for a copy, it can be safely forwarded to

                     *  the copied tree, we want to profit from that

                     */

                    JCMemberReference result = new JCMemberReference(t.mode, t.name, expr, typeargs) {

                        @Override

                        public void setOverloadKind(OverloadKind overloadKind) {

                                t.setOverloadKind(overloadKind);

                            }

                        }

                    };

                    result.pos = t.pos;

                    return result;

                }

            };

        deferredCopier = new TypeMapping<Void> () {

                @Override

                public Type visitType(Type t, Void v) {

                    if (t.hasTag(DEFERRED)) {

                        DeferredType dt = (DeferredType) t;

                        return new DeferredType(treeCopier.copy(dt.tree), dt.env);

                    }

                    return t;

                }

            };

    }

    /** shared tree for stuck expressions */

    final JCTree stuckTree;

    /**

     * This type represents a deferred type. A deferred type starts off with

     * no information on the underlying expression type. Such info needs to be

     * discovered through type-checking the deferred type against a target-type.

     * Every deferred type keeps a pointer to the AST node from which it originated.

     */

    public class DeferredType extends Type {

        public JCExpression tree;

        Env<AttrContext> env;

        AttrMode mode;

        Set<Symbol> notPertinentToApplicability = new HashSet<>();

        SpeculativeCache speculativeCache;

        DeferredType(JCExpression tree, Env<AttrContext> env) {

            super(null, TypeMetadata.EMPTY);

            this.tree = tree;

            this.env = attr.copyEnv(env);

            this.speculativeCache = new SpeculativeCache();

        }

        @Override

        public DeferredType cloneWithMetadata(TypeMetadata md) {

            throw new AssertionError("Cannot add metadata to a deferred type");

        }

        @Override

        public TypeTag getTag() {

            return DEFERRED;

        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)

        public String toString() {

            return "DeferredType";

        }

        /**

         * A speculative cache is used to keep track of all overload resolution rounds

         * that triggered speculative attribution on a given deferred type. Each entry

         * stores a pointer to the speculative tree and the resolution phase in which the entry

         * has been added.

         */

        class SpeculativeCache {

            private Map<Symbol, List<Entry>> cache = new WeakHashMap<>();

            class Entry {

                JCTree speculativeTree;

                ResultInfo resultInfo;

                public Entry(JCTree speculativeTree, ResultInfo resultInfo) {

                    this.speculativeTree = speculativeTree;

                    this.resultInfo = resultInfo;

                }

                boolean matches(MethodResolutionPhase phase) {

                    return resultInfo.checkContext.deferredAttrContext().phase == phase;

                }

            }

            /**

             * Retrieve a speculative cache entry corresponding to given symbol

             * and resolution phase

             */

            Entry get(Symbol msym, MethodResolutionPhase phase) {

                List<Entry> entries = cache.get(msym);

                if (entries == null) return null;

                for (Entry e : entries) {

                    if (e.matches(phase)) return e;

                }

                return null;

            }

            /**

             * Stores a speculative cache entry corresponding to given symbol

             * and resolution phase

             */

            void put(JCTree speculativeTree, ResultInfo resultInfo) {

                Symbol msym = resultInfo.checkContext.deferredAttrContext().msym;

                List<Entry> entries = cache.get(msym);

                if (entries == null) {

                    entries = List.nil();

                }

                cache.put(msym, entries.prepend(new Entry(speculativeTree, resultInfo)));

            }

        }

        /**

         * Get the type that has been computed during a speculative attribution round

         */

        Type speculativeType(Symbol msym, MethodResolutionPhase phase) {

            SpeculativeCache.Entry e = speculativeCache.get(msym, phase);

            return e != null ? e.speculativeTree.type : Type.noType;

        }

        JCTree speculativeTree(DeferredAttrContext deferredAttrContext) {

            DeferredType.SpeculativeCache.Entry e = speculativeCache.get(deferredAttrContext.msym, deferredAttrContext.phase);

            return e != null ? e.speculativeTree : stuckTree;

        }

        DeferredTypeCompleter completer() {

            return basicCompleter;

        }

        /**

         * Check a deferred type against a potential target-type. Depending on

         * the current attribution mode, a normal vs. speculative attribution

         * round is performed on the underlying AST node. There can be only one

         * speculative round for a given target method symbol; moreover, a normal

         * attribution round must follow one or more speculative rounds.

         */

        Type check(ResultInfo resultInfo) {

            DeferredStuckPolicy deferredStuckPolicy;

            if (resultInfo.pt.hasTag(NONE) || resultInfo.pt.isErroneous()) {

                deferredStuckPolicy = dummyStuckPolicy;

            } else if (resultInfo.checkContext.deferredAttrContext().mode == AttrMode.SPECULATIVE ||

                    resultInfo.checkContext.deferredAttrContext().insideOverloadPhase()) {

                deferredStuckPolicy = new OverloadStuckPolicy(resultInfo, this);

            } else {

                deferredStuckPolicy = new CheckStuckPolicy(resultInfo, this);

            }

            return check(resultInfo, deferredStuckPolicy, completer());

        }

        private Type check(ResultInfo resultInfo, DeferredStuckPolicy deferredStuckPolicy,

                DeferredTypeCompleter deferredTypeCompleter) {

            DeferredAttrContext deferredAttrContext =

                    resultInfo.checkContext.deferredAttrContext();

            Assert.check(deferredAttrContext != emptyDeferredAttrContext);

            if (deferredStuckPolicy.isStuck()) {

                notPertinentToApplicability.add(deferredAttrContext.msym);

                deferredAttrContext.addDeferredAttrNode(this, resultInfo, deferredStuckPolicy);

                return Type.noType;

            } else {

                try {

                    return deferredTypeCompleter.complete(this, resultInfo, deferredAttrContext);

                } finally {

                    mode = deferredAttrContext.mode;

                }

            }

        }

    }

    /**

     * A completer for deferred types. Defines an entry point for type-checking

     * a deferred type.

     */

    interface DeferredTypeCompleter {

        /**

         * Entry point for type-checking a deferred type. Depending on the

         * circumstances, type-checking could amount to full attribution

         * or partial structural check (aka potential applicability).

         */

        Type complete(DeferredType dt, ResultInfo resultInfo, DeferredAttrContext deferredAttrContext);

    }

    /**

     * A basic completer for deferred types. This completer type-checks a deferred type

     * using attribution; depending on the attribution mode, this could be either standard

     * or speculative attribution.

     */

    DeferredTypeCompleter basicCompleter = new DeferredTypeCompleter() {

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

            switch (deferredAttrContext.mode) {

                case SPECULATIVE:

                    //Note: if a symbol is imported twice we might do two identical

                    //speculative rounds...

                    Assert.check(dt.mode == null || dt.mode == AttrMode.SPECULATIVE);

                    JCTree speculativeTree = attribSpeculative(dt.tree, dt.env, resultInfo);

                    dt.speculativeCache.put(speculativeTree, resultInfo);

                    return speculativeTree.type;

                case CHECK:

                    Assert.check(dt.mode != null);

                    return attr.attribTree(dt.tree, dt.env, resultInfo);

            }

            Assert.error();

            return null;

        }

    };

    /**

     * Policy for detecting stuck expressions. Different criteria might cause

     * an expression to be judged as stuck, depending on whether the check

     * is performed during overload resolution or after most specific.

     */

    interface DeferredStuckPolicy {

        /**

         * Has the policy detected that a given expression should be considered stuck?

         */

        boolean isStuck();

        /**

         * Get the set of inference variables a given expression depends upon.

         */

        Set<Type> stuckVars();

        /**

         * Get the set of inference variables which might get new constraints

         * if a given expression is being type-checked.

         */

        Set<Type> depVars();

    }

    /**

     * Basic stuck policy; an expression is never considered to be stuck.

     */

    DeferredStuckPolicy dummyStuckPolicy = new DeferredStuckPolicy() {

        @Override

        public boolean isStuck() {

            return false;

        }

        @Override

        public Set<Type> stuckVars() {

            return Collections.emptySet();

        }

        @Override

        public Set<Type> depVars() {

            return Collections.emptySet();

        }

    };

    /**

     * The 'mode' in which the deferred type is to be type-checked

     */

    public enum AttrMode {

        /**

         * A speculative type-checking round is used during overload resolution

         * mainly to generate constraints on inference variables. Side-effects

         * arising from type-checking the expression associated with the deferred

         * type are reversed after the speculative round finishes. This means the

         * expression tree will be left in a blank state.

         */

        SPECULATIVE,

        /**

         * This is the plain type-checking mode. Produces side-effects on the underlying AST node

         */

        CHECK

    }

    /**

     * Performs speculative attribution of a lambda body and returns the speculative lambda tree,

     * in the absence of a target-type. Since {@link Attr#visitLambda(JCLambda)} cannot type-check

     * lambda bodies w/o a suitable target-type, this routine 'unrolls' the lambda by turning it

     * into a regular block, speculatively type-checks the block and then puts back the pieces.

     */

    JCLambda attribSpeculativeLambda(JCLambda that, Env<AttrContext> env, ResultInfo resultInfo) {

        ListBuffer<JCStatement> stats = new ListBuffer<>();

        stats.addAll(that.params);

        if (that.getBodyKind() == JCLambda.BodyKind.EXPRESSION) {

            stats.add(make.Return((JCExpression)that.body));

        } else {

            stats.add((JCBlock)that.body);

        }

        JCBlock lambdaBlock = make.at(that.pos).Block(0, stats.toList());

        Env<AttrContext> localEnv = attr.lambdaEnv(that, env);

        try {

            localEnv.info.returnResult = resultInfo;

            JCBlock speculativeTree = (JCBlock)attribSpeculative(lambdaBlock, localEnv, resultInfo);

            List<JCVariableDecl> args = speculativeTree.getStatements().stream()

                    .filter(s -> s.hasTag(Tag.VARDEF))

                    .map(t -> (JCVariableDecl)t)

                    .collect(List.collector());

            JCTree lambdaBody = speculativeTree.getStatements().last();

            if (lambdaBody.hasTag(Tag.RETURN)) {

                lambdaBody = ((JCReturn)lambdaBody).expr;

            }

            JCLambda speculativeLambda = make.Lambda(args, lambdaBody);

            attr.preFlow(speculativeLambda);

            flow.analyzeLambda(env, speculativeLambda, make, false);

            return speculativeLambda;

        } finally {

            localEnv.info.scope.leave();

        }

    }

    /**

     * Routine that performs speculative type-checking; the input AST node is

     * cloned (to avoid side-effects cause by Attr) and compiler state is

     * restored after type-checking. All diagnostics (but critical ones) are

     * disabled during speculative type-checking.

     */

    JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo) {

        return attribSpeculative(tree, env, resultInfo, treeCopier,

                (newTree)->new DeferredAttrDiagHandler(log, newTree), null);

    }

    JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo, LocalCacheContext localCache) {

        return attribSpeculative(tree, env, resultInfo, treeCopier,

                (newTree)->new DeferredAttrDiagHandler(log, newTree), localCache);

    }

    <Z> JCTree attribSpeculative(JCTree tree, Env<AttrContext> env, ResultInfo resultInfo, TreeCopier<Z> deferredCopier,

                                 Function<JCTree, DeferredDiagnosticHandler> diagHandlerCreator,

                                 LocalCacheContext localCache) {

        final JCTree newTree = deferredCopier.copy(tree);

        Env<AttrContext> speculativeEnv = env.dup(newTree, env.info.dup(env.info.scope.dupUnshared(env.info.scope.owner)));

        speculativeEnv.info.isSpeculative = true;

        Log.DeferredDiagnosticHandler deferredDiagnosticHandler = diagHandlerCreator.apply(newTree);

        try {

            attr.attribTree(newTree, speculativeEnv, resultInfo);

            return newTree;

        } finally {