/*
 * Copyright (c) 2014, 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
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package com.sun.tools.javac.comp;

import com.sun.source.tree.LambdaExpressionTree;
import com.sun.tools.javac.code.Source;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Types;
import com.sun.tools.javac.comp.ArgumentAttr.LocalCacheContext;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCBlock;
import com.sun.tools.javac.tree.JCTree.JCClassDecl;
import com.sun.tools.javac.tree.JCTree.JCDoWhileLoop;
import com.sun.tools.javac.tree.JCTree.JCEnhancedForLoop;
import com.sun.tools.javac.tree.JCTree.JCForLoop;
import com.sun.tools.javac.tree.JCTree.JCIf;
import com.sun.tools.javac.tree.JCTree.JCLambda;
import com.sun.tools.javac.tree.JCTree.JCLambda.ParameterKind;
import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
import com.sun.tools.javac.tree.JCTree.JCMethodInvocation;
import com.sun.tools.javac.tree.JCTree.JCNewClass;
import com.sun.tools.javac.tree.JCTree.JCStatement;
import com.sun.tools.javac.tree.JCTree.JCSwitch;
import com.sun.tools.javac.tree.JCTree.JCTypeApply;
import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
import com.sun.tools.javac.tree.JCTree.JCWhileLoop;
import com.sun.tools.javac.tree.JCTree.Tag;
import com.sun.tools.javac.tree.TreeCopier;
import com.sun.tools.javac.tree.TreeInfo;
import com.sun.tools.javac.tree.TreeMaker;
import com.sun.tools.javac.tree.TreeScanner;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.DefinedBy;
import com.sun.tools.javac.util.DefinedBy.Api;
import com.sun.tools.javac.util.JCDiagnostic;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticType;
import com.sun.tools.javac.util.List;
import com.sun.tools.javac.util.ListBuffer;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.Names;
import com.sun.tools.javac.util.Options;

import java.util.EnumSet;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Predicate;

import static com.sun.tools.javac.code.Flags.GENERATEDCONSTR;
import static com.sun.tools.javac.code.Flags.SYNTHETIC;
import static com.sun.tools.javac.code.TypeTag.CLASS;
import static com.sun.tools.javac.tree.JCTree.Tag.APPLY;
import static com.sun.tools.javac.tree.JCTree.Tag.METHODDEF;
import static com.sun.tools.javac.tree.JCTree.Tag.NEWCLASS;
import static com.sun.tools.javac.tree.JCTree.Tag.TYPEAPPLY;

Helper class for defining custom code analysis, such as finding instance creation expression
that can benefit from diamond syntax.
/**
 * Helper class for defining custom code analysis, such as finding instance creation expression
 * that can benefit from diamond syntax.
 */
public class Analyzer {
    protected static final Context.Key<Analyzer> analyzerKey = new Context.Key<>();

    final Types types;
    final Log log;
    final Attr attr;
    final DeferredAttr deferredAttr;
    final ArgumentAttr argumentAttr;
    final TreeMaker make;
    final Names names;
    private final boolean allowDiamondWithAnonymousClassCreation;

    final EnumSet<AnalyzerMode> analyzerModes;

    public static Analyzer instance(Context context) {
        Analyzer instance = context.get(analyzerKey);
        if (instance == null)
            instance = new Analyzer(context);
        return instance;
    }

    protected Analyzer(Context context) {
        context.put(analyzerKey, this);
        types = Types.instance(context);
        log = Log.instance(context);
        attr = Attr.instance(context);
        deferredAttr = DeferredAttr.instance(context);
        argumentAttr = ArgumentAttr.instance(context);
        make = TreeMaker.instance(context);
        names = Names.instance(context);
        Options options = Options.instance(context);
        String findOpt = options.get("find");
        //parse modes
        Source source = Source.instance(context);
        allowDiamondWithAnonymousClassCreation = source.allowDiamondWithAnonymousClassCreation();
        analyzerModes = AnalyzerMode.getAnalyzerModes(findOpt, source);
    }

    
This enum defines supported analyzer modes, as well as defining the logic for decoding the -XDfind option. /**
     * This enum defines supported analyzer modes, as well as defining the logic for decoding
     * the {@code -XDfind} option.
     */
    enum AnalyzerMode {
        DIAMOND("diamond", Source::allowDiamond),
        LAMBDA("lambda", Source::allowLambda),
        METHOD("method", Source::allowGraphInference);

        final String opt;
        final Predicate<Source> sourceFilter;

        AnalyzerMode(String opt, Predicate<Source> sourceFilter) {
            this.opt = opt;
            this.sourceFilter = sourceFilter;
        }

        
This method is used to parse the find option. Possible modes are separated by colon; a mode can be excluded by prepending '-' to its name. Finally, the special mode 'all' can be used to add all modes to the resulting enum. /**
         * This method is used to parse the {@code find} option.
         * Possible modes are separated by colon; a mode can be excluded by
         * prepending '-' to its name. Finally, the special mode 'all' can be used to
         * add all modes to the resulting enum.
         */
        static EnumSet<AnalyzerMode> getAnalyzerModes(String opt, Source source) {
            if (opt == null) {
                return EnumSet.noneOf(AnalyzerMode.class);
            }
            List<String> modes = List.from(opt.split(","));
            EnumSet<AnalyzerMode> res = EnumSet.noneOf(AnalyzerMode.class);
            if (modes.contains("all")) {
                res = EnumSet.allOf(AnalyzerMode.class);
            }
            for (AnalyzerMode mode : values()) {
                if (modes.contains(mode.opt)) {
                    res.add(mode);
                } else if (modes.contains("-" + mode.opt) || !mode.sourceFilter.test(source)) {
                    res.remove(mode);
                }
            }
            return res;
        }
    }

    
A statement analyzer is a work-unit that matches certain AST nodes (of given type S), rewrites them to different AST nodes (of type T) and then generates some meaningful messages in case the analysis has been successful. /**
     * A statement analyzer is a work-unit that matches certain AST nodes (of given type {@code S}),
     * rewrites them to different AST nodes (of type {@code T}) and then generates some meaningful
     * messages in case the analysis has been successful.
     */
    abstract class StatementAnalyzer<S extends JCTree, T extends JCTree> {

        AnalyzerMode mode;
        JCTree.Tag tag;

        StatementAnalyzer(AnalyzerMode mode, Tag tag) {
            this.mode = mode;
            this.tag = tag;
        }

        
Is this analyzer allowed to run?
/**
         * Is this analyzer allowed to run?
         */
        boolean isEnabled() {
            return analyzerModes.contains(mode);
        }

        
Should this analyzer be rewriting the given tree?
/**
         * Should this analyzer be rewriting the given tree?
         */
        abstract boolean match(S tree);

        
Rewrite a given AST node into a new one
/**
         * Rewrite a given AST node into a new one
         */
        abstract T map(S oldTree, S newTree);

        
Entry-point for comparing results and generating diagnostics.
/**
         * Entry-point for comparing results and generating diagnostics.
         */
        abstract void process(S oldTree, T newTree, boolean hasErrors);

    }

    
This analyzer checks if generic instance creation expression can use diamond syntax.
/**
     * This analyzer checks if generic instance creation expression can use diamond syntax.
     */
    class DiamondInitializer extends StatementAnalyzer<JCNewClass, JCNewClass> {

        DiamondInitializer() {
            super(AnalyzerMode.DIAMOND, NEWCLASS);
        }

        @Override
        boolean match(JCNewClass tree) {
            return tree.clazz.hasTag(TYPEAPPLY) &&
                    !TreeInfo.isDiamond(tree) &&
                    (tree.def == null || allowDiamondWithAnonymousClassCreation);
        }

        @Override
        JCNewClass map(JCNewClass oldTree, JCNewClass newTree) {
            if (newTree.clazz.hasTag(TYPEAPPLY)) {
                ((JCTypeApply)newTree.clazz).arguments = List.nil();
            }
            return newTree;
        }

        @Override
        void process(JCNewClass oldTree, JCNewClass newTree, boolean hasErrors) {
            if (!hasErrors) {
                List<Type> inferredArgs, explicitArgs;
                if (oldTree.def != null) {
                    inferredArgs = newTree.def.implementing.nonEmpty()
                                      ? newTree.def.implementing.get(0).type.getTypeArguments()
                                      : newTree.def.extending.type.getTypeArguments();
                    explicitArgs = oldTree.def.implementing.nonEmpty()
                                      ? oldTree.def.implementing.get(0).type.getTypeArguments()
                                      : oldTree.def.extending.type.getTypeArguments();
                } else {
                    inferredArgs = newTree.type.getTypeArguments();
                    explicitArgs = oldTree.type.getTypeArguments();
                }
                for (Type t : inferredArgs) {
                    if (!types.isSameType(t, explicitArgs.head)) {
                        return;
                    }
                    explicitArgs = explicitArgs.tail;
                }
                //exact match
                log.warning(oldTree.clazz, "diamond.redundant.args");
            }
        }
    }

    
This analyzer checks if anonymous instance creation expression can replaced by lambda.
/**
     * This analyzer checks if anonymous instance creation expression can replaced by lambda.
     */
    class LambdaAnalyzer extends StatementAnalyzer<JCNewClass, JCLambda> {

        LambdaAnalyzer() {
            super(AnalyzerMode.LAMBDA, NEWCLASS);
        }

        @Override
        boolean match (JCNewClass tree){
            Type clazztype = tree.clazz.type;
            return tree.def != null &&
                    clazztype.hasTag(CLASS) &&
                    types.isFunctionalInterface(clazztype.tsym) &&
                    decls(tree.def).length() == 1;
        }
        //where
            private List<JCTree> decls(JCClassDecl decl) {
                ListBuffer<JCTree> decls = new ListBuffer<>();
                for (JCTree t : decl.defs) {
                    if (t.hasTag(METHODDEF)) {
                        JCMethodDecl md = (JCMethodDecl)t;
                        if ((md.getModifiers().flags & GENERATEDCONSTR) == 0) {
                            decls.add(md);
                        }
                    } else {
                        decls.add(t);
                    }
                }
                return decls.toList();
            }

        @Override
        JCLambda map (JCNewClass oldTree, JCNewClass newTree){
            JCMethodDecl md = (JCMethodDecl)decls(newTree.def).head;
            List<JCVariableDecl> params = md.params;
            JCBlock body = md.body;
            return make.Lambda(params, body);
        }
        @Override
        void process (JCNewClass oldTree, JCLambda newTree, boolean hasErrors){
            if (!hasErrors) {
                log.warning(oldTree.def, "potential.lambda.found");
            }
        }
    }

    
This analyzer checks if generic method call has redundant type arguments.
/**
     * This analyzer checks if generic method call has redundant type arguments.
     */
    class RedundantTypeArgAnalyzer extends StatementAnalyzer<JCMethodInvocation, JCMethodInvocation> {

        RedundantTypeArgAnalyzer() {
            super(AnalyzerMode.METHOD, APPLY);
        }

        @Override
        boolean match (JCMethodInvocation tree){
            return tree.typeargs != null &&
                    tree.typeargs.nonEmpty();
        }
        @Override
        JCMethodInvocation map (JCMethodInvocation oldTree, JCMethodInvocation newTree){
            newTree.typeargs = List.nil();
            return newTree;
        }
        @Override
        void process (JCMethodInvocation oldTree, JCMethodInvocation newTree, boolean hasErrors){
            if (!hasErrors) {
                //exact match
                log.warning(oldTree, "method.redundant.typeargs");
            }
        }
    }

    @SuppressWarnings({"unchecked", "rawtypes"})
    StatementAnalyzer<JCTree, JCTree>[] analyzers = new StatementAnalyzer[] {
            new DiamondInitializer(),
            new LambdaAnalyzer(),
            new RedundantTypeArgAnalyzer()
    };

    
Analyze an AST node if needed.
/**
     * Analyze an AST node if needed.
     */
    void analyzeIfNeeded(JCTree tree, Env<AttrContext> env) {
        if (!analyzerModes.isEmpty() &&
                !env.info.isSpeculative &&
                TreeInfo.isStatement(tree)) {
            JCStatement stmt = (JCStatement)tree;
            analyze(stmt, env);
        }
    }

    
Analyze an AST node; this involves collecting a list of all the nodes that needs rewriting,
and speculatively type-check the rewritten code to compare results against previously attributed code.
/**
     * Analyze an AST node; this involves collecting a list of all the nodes that needs rewriting,
     * and speculatively type-check the rewritten code to compare results against previously attributed code.
     */
    void analyze(JCStatement statement, Env<AttrContext> env) {
        AnalysisContext context = new AnalysisContext();
        StatementScanner statementScanner = new StatementScanner(context);
        statementScanner.scan(statement);

        if (!context.treesToAnalyzer.isEmpty()) {

            //add a block to hoist potential dangling variable declarations
            JCBlock fakeBlock = make.Block(SYNTHETIC, List.of(statement));

            TreeMapper treeMapper = new TreeMapper(context);
            //TODO: to further refine the analysis, try all rewriting combinations
            deferredAttr.attribSpeculative(fakeBlock, env, attr.statInfo, treeMapper,
                    t -> new AnalyzeDeferredDiagHandler(context),
                    argumentAttr.withLocalCacheContext());
            context.treeMap.entrySet().forEach(e -> {
                context.treesToAnalyzer.get(e.getKey())
                        .process(e.getKey(), e.getValue(), context.errors.nonEmpty());
            });
        }
    }

    
Simple deferred diagnostic handler which filters out all messages and keep track of errors.
/**
     * Simple deferred diagnostic handler which filters out all messages and keep track of errors.
     */
    class AnalyzeDeferredDiagHandler extends Log.DeferredDiagnosticHandler {
        AnalysisContext context;

        public AnalyzeDeferredDiagHandler(AnalysisContext context) {
            super(log, d -> {
                if (d.getType() == DiagnosticType.ERROR) {
                    context.errors.add(d);
                }
                return true;
            });
            this.context = context;
        }
    }

    
This class is used to pass around contextual information bewteen analyzer classes, such as
trees to be rewritten, errors occurred during the speculative attribution step, etc.
/**
     * This class is used to pass around contextual information bewteen analyzer classes, such as
     * trees to be rewritten, errors occurred during the speculative attribution step, etc.
     */
    class AnalysisContext {
        
Map from trees to analyzers. /** Map from trees to analyzers. */
        Map<JCTree, StatementAnalyzer<JCTree, JCTree>> treesToAnalyzer = new HashMap<>();

        
Map from original AST nodes to rewritten AST nodes /** Map from original AST nodes to rewritten AST nodes */
        Map<JCTree, JCTree> treeMap = new HashMap<>();

        
Errors in rewritten tree /** Errors in rewritten tree */
        ListBuffer<JCDiagnostic> errors = new ListBuffer<>();
    }

    
Subclass of TreeScanner which visit AST-nodes w/o crossing statement boundaries. /**
     * Subclass of {@link com.sun.tools.javac.tree.TreeScanner} which visit AST-nodes w/o crossing
     * statement boundaries.
     */
    class StatementScanner extends TreeScanner {

        
context /** context */
        AnalysisContext context;

        StatementScanner(AnalysisContext context) {
            this.context = context;
        }

        @Override
        @SuppressWarnings("unchecked")
        public void scan(JCTree tree) {
            if (tree != null) {
                for (StatementAnalyzer<JCTree, JCTree> analyzer : analyzers) {
                    if (analyzer.isEnabled() &&
                            tree.hasTag(analyzer.tag) &&
                            analyzer.match(tree)) {
                        context.treesToAnalyzer.put(tree, analyzer);
                        break; //TODO: cover cases where multiple matching analyzers are found
                    }
                }
            }
            super.scan(tree);
        }

        @Override
        public void visitClassDef(JCClassDecl tree) {
            //do nothing (prevents seeing same stuff twice
        }

        @Override
        public void visitMethodDef(JCMethodDecl tree) {
            //do nothing (prevents seeing same stuff twice
        }

        @Override
        public void visitBlock(JCBlock tree) {
            //do nothing (prevents seeing same stuff twice
        }

        @Override
        public void visitSwitch(JCSwitch tree) {
            scan(tree.getExpression());
        }

        @Override
        public void visitForLoop(JCForLoop tree) {
            scan(tree.getInitializer());
            scan(tree.getCondition());
            scan(tree.getUpdate());
        }

        @Override
        public void visitForeachLoop(JCEnhancedForLoop tree) {
            scan(tree.getExpression());
        }

        @Override
        public void visitWhileLoop(JCWhileLoop tree) {
            scan(tree.getCondition());
        }

        @Override
        public void visitDoLoop(JCDoWhileLoop tree) {
            scan(tree.getCondition());
        }

        @Override
        public void visitIf(JCIf tree) {
            scan(tree.getCondition());
        }
    }

    
Subclass of TreeCopier that maps nodes matched by analyzers onto new AST nodes.
/**
     * Subclass of TreeCopier that maps nodes matched by analyzers onto new AST nodes.
     */
    class TreeMapper extends TreeCopier<Void> {

        AnalysisContext context;

        TreeMapper(AnalysisContext context) {
            super(make);
            this.context = context;
        }

        @Override
        @SuppressWarnings("unchecked")
        public <Z extends JCTree> Z copy(Z tree, Void _unused) {
            Z newTree = super.copy(tree, _unused);
            StatementAnalyzer<JCTree, JCTree> analyzer = context.treesToAnalyzer.get(tree);
            if (analyzer != null) {
                newTree = (Z)analyzer.map(tree, newTree);
                context.treeMap.put(tree, newTree);
            }
            return newTree;
        }

        @Override @DefinedBy(Api.COMPILER_TREE)
        public JCTree visitLambdaExpression(LambdaExpressionTree node, Void _unused) {
            JCLambda oldLambda = (JCLambda)node;
            JCLambda newLambda = (JCLambda)super.visitLambdaExpression(node, _unused);
            if (oldLambda.paramKind == ParameterKind.IMPLICIT) {
                //reset implicit lambda parameters (whose type might have been set during attr)
                newLambda.paramKind = ParameterKind.IMPLICIT;
                newLambda.params.forEach(p -> p.vartype = null);
            }
            return newLambda;
        }
    }
}