/*

 * Copyright (c) 2005, 2018, 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.model;

import java.util.Collections;

import java.util.HashSet;

import java.util.LinkedHashSet;

import java.util.Map;

import java.util.Set;

import java.util.stream.Collectors;

import javax.lang.model.AnnotatedConstruct;

import javax.lang.model.SourceVersion;

import javax.lang.model.element.*;

import javax.lang.model.type.DeclaredType;

import javax.lang.model.util.Elements;

import javax.tools.JavaFileObject;

import static javax.lang.model.util.ElementFilter.methodsIn;

import com.sun.source.util.JavacTask;

import com.sun.tools.javac.api.JavacTaskImpl;

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

import com.sun.tools.javac.code.Attribute.Compound;

import com.sun.tools.javac.code.Directive.ExportsDirective;

import com.sun.tools.javac.code.Directive.ExportsFlag;

import com.sun.tools.javac.code.Directive.OpensDirective;

import com.sun.tools.javac.code.Directive.OpensFlag;

import com.sun.tools.javac.code.Directive.RequiresDirective;

import com.sun.tools.javac.code.Directive.RequiresFlag;

import com.sun.tools.javac.code.Scope.WriteableScope;

import com.sun.tools.javac.code.Source.Feature;

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

import com.sun.tools.javac.comp.AttrContext;

import com.sun.tools.javac.comp.Enter;

import com.sun.tools.javac.comp.Env;

import com.sun.tools.javac.main.JavaCompiler;

import com.sun.tools.javac.processing.PrintingProcessor;

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

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

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

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

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

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

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

import static com.sun.tools.javac.code.Kinds.Kind.*;

import static com.sun.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;

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

import com.sun.tools.javac.comp.Modules;

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

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

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

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

/**

 * Utility methods for operating on program elements.

 *

 * <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></p>

 */

public class JavacElements implements Elements {

    private final JavaCompiler javaCompiler;

    private final Symtab syms;

    private final Modules modules;

    private final Names names;

    private final Types types;

    private final Enter enter;

    private final Resolve resolve;

    private final JavacTaskImpl javacTaskImpl;

    private final Log log;

    private final boolean allowModules;

    public static JavacElements instance(Context context) {

        JavacElements instance = context.get(JavacElements.class);

        if (instance == null)

            instance = new JavacElements(context);

        return instance;

    }

    protected JavacElements(Context context) {

        context.put(JavacElements.class, this);

        javaCompiler = JavaCompiler.instance(context);

        syms = Symtab.instance(context);

        modules = Modules.instance(context);

        names = Names.instance(context);

        types = Types.instance(context);

        enter = Enter.instance(context);

        resolve = Resolve.instance(context);

        JavacTask t = context.get(JavacTask.class);

        javacTaskImpl = t instanceof JavacTaskImpl ? (JavacTaskImpl) t : null;

        log = Log.instance(context);

        Source source = Source.instance(context);

        allowModules = Feature.MODULES.allowedInSource(source);

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public Set<? extends ModuleElement> getAllModuleElements() {

        if (allowModules)

            return Collections.unmodifiableSet(modules.allModules());

        else

            return Collections.emptySet();

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public ModuleSymbol getModuleElement(CharSequence name) {

        ensureEntered("getModuleElement");

        if (modules.getDefaultModule() == syms.noModule)

            return null;

        String strName = name.toString();

        if (strName.equals(""))

            return syms.unnamedModule;

        return modules.getObservableModule(names.fromString(strName));

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public PackageSymbol getPackageElement(CharSequence name) {

        return doGetPackageElement(null, name);

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public PackageSymbol getPackageElement(ModuleElement module, CharSequence name) {

        module.getClass();

        return doGetPackageElement(module, name);

    }

    private PackageSymbol doGetPackageElement(ModuleElement module, CharSequence name) {

        ensureEntered("getPackageElement");

        return doGetElement(module, "getPackageElement", name, PackageSymbol.class);

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public ClassSymbol getTypeElement(CharSequence name) {

        return doGetTypeElement(null, name);

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public ClassSymbol getTypeElement(ModuleElement module, CharSequence name) {

        module.getClass();

        return doGetTypeElement(module, name);

    }

    private ClassSymbol doGetTypeElement(ModuleElement module, CharSequence name) {

        ensureEntered("getTypeElement");

        return doGetElement(module, "getTypeElement", name, ClassSymbol.class);

    }

    private <S extends Symbol> S doGetElement(ModuleElement module, String methodName,

                                              CharSequence name, Class<S> clazz) {

        String strName = name.toString();

        if (!SourceVersion.isName(strName) && (!strName.isEmpty() || clazz == ClassSymbol.class)) {

            return null;

        }

        if (module == null) {

            return unboundNameToSymbol(methodName, strName, clazz);

        } else {

            return nameToSymbol((ModuleSymbol) module, strName, clazz);

        }

    }

    private final Set<String> alreadyWarnedDuplicates = new HashSet<>();

    private <S extends Symbol> S unboundNameToSymbol(String methodName,

                                                     String nameStr,

                                                     Class<S> clazz) {

        if (modules.getDefaultModule() == syms.noModule) { //not a modular mode:

            return nameToSymbol(syms.noModule, nameStr, clazz);

        }

        Set<S> found = new LinkedHashSet<>();

        for (ModuleSymbol msym : modules.allModules()) {

            S sym = nameToSymbol(msym, nameStr, clazz);

            if (sym == null)

                continue;

            if (clazz == ClassSymbol.class) {

                // Always include classes

                found.add(sym);

            } else if (clazz == PackageSymbol.class) {

                // In module mode, ignore the "spurious" empty packages that "enclose" module-specific packages.

                // For example, if a module contains classes or package info in package p.q.r, it will also appear

                // to have additional packages p.q and p, even though these packages have no content other

                // than the subpackage.  We don't want those empty packages showing up in searches for p or p.q.

                if (!sym.members().isEmpty() || ((PackageSymbol) sym).package_info != null) {

                    found.add(sym);

                }

            }

        }

        if (found.size() == 1) {

            return found.iterator().next();

        } else if (found.size() > 1) {

            //more than one element found, produce a note:

            if (alreadyWarnedDuplicates.add(methodName + ":" + nameStr)) {

                String moduleNames = found.stream()

                                          .map(s -> s.packge().modle)

                                          .map(m -> m.toString())

                                          .collect(Collectors.joining(", "));

                log.note(Notes.MultipleElements(methodName, nameStr, moduleNames));

            }

            return null;

        } else {

            //not found, or more than one element found:

            return null;

        }

    }

    /**

     * Returns a symbol given the type's or package's canonical name,

     * or null if the name isn't found.

     */

    private <S extends Symbol> S nameToSymbol(ModuleSymbol module, String nameStr, Class<S> clazz) {

        Name name = names.fromString(nameStr);

        // First check cache.

        Symbol sym = (clazz == ClassSymbol.class)

                    ? syms.getClass(module, name)

                    : syms.lookupPackage(module, name);

        try {

            if (sym == null)

                sym = javaCompiler.resolveIdent(module, nameStr);

            sym.complete();

            return (sym.kind != ERR &&

                    sym.exists() &&

                    clazz.isInstance(sym) &&

                    name.equals(sym.getQualifiedName()))

                ? clazz.cast(sym)

                : null;

            return null;

        }

    }

    /**

     * Returns the tree for an annotation given the annotated element

     * and the element's own tree.  Returns null if the tree cannot be found.

     */

    private JCTree matchAnnoToTree(AnnotationMirror findme,

                                   Element e, JCTree tree) {

        Symbol sym = cast(Symbol.class, e);

        class Vis extends JCTree.Visitor {

            List<JCAnnotation> result = null;

            public void visitPackageDef(JCPackageDecl tree) {

                result = tree.annotations;

            }

            public void visitClassDef(JCClassDecl tree) {

                result = tree.mods.annotations;

            }

            public void visitMethodDef(JCMethodDecl tree) {

                result = tree.mods.annotations;

            }

            public void visitVarDef(JCVariableDecl tree) {

                result = tree.mods.annotations;

            }

            @Override

            public void visitTypeParameter(JCTypeParameter tree) {

                result = tree.annotations;

            }

        }

        Vis vis = new Vis();

        tree.accept(vis);

        if (vis.result == null)

            return null;

        List<Attribute.Compound> annos = sym.getAnnotationMirrors();

        return matchAnnoToTree(cast(Attribute.Compound.class, findme),

                               annos,

                               vis.result);

    }

    /**

     * Returns the tree for an annotation given a list of annotations

     * in which to search (recursively) and their corresponding trees.

     * Returns null if the tree cannot be found.

     */

    private JCTree matchAnnoToTree(Attribute.Compound findme,

                                   List<Attribute.Compound> annos,

                                   List<JCAnnotation> trees) {

        for (Attribute.Compound anno : annos) {

            for (JCAnnotation tree : trees) {

                if (tree.type.tsym != anno.type.tsym)

                    continue;

                JCTree match = matchAttributeToTree(findme, anno, tree);

                if (match != null)

                    return match;

            }

        }

        return null;

    }

    /**

     * Returns the tree for an attribute given an enclosing attribute to

     * search (recursively) and the enclosing attribute's corresponding tree.

     * Returns null if the tree cannot be found.

     */

    private JCTree matchAttributeToTree(final Attribute findme,

                                        final Attribute attr,

                                        final JCTree tree) {

        if (attr == findme)

            return tree;

        class Vis implements Attribute.Visitor {

            JCTree result = null;

            public void visitConstant(Attribute.Constant value) {

            }

            public void visitClass(Attribute.Class clazz) {

            }

            public void visitCompound(Attribute.Compound anno) {

                for (Pair<MethodSymbol, Attribute> pair : anno.values) {

                    JCExpression expr = scanForAssign(pair.fst, tree);

                    if (expr != null) {

                        JCTree match = matchAttributeToTree(findme, pair.snd, expr);

                        if (match != null) {

                            result = match;

                            return;

                        }

                    }

                }

            }

            public void visitArray(Attribute.Array array) {

                if (tree.hasTag(NEWARRAY)) {

                    List<JCExpression> elems = ((JCNewArray)tree).elems;

                    for (Attribute value : array.values) {

                        JCTree match = matchAttributeToTree(findme, value, elems.head);

                        if (match != null) {

                            result = match;

                            return;

                        }

                        elems = elems.tail;

                    }

                } else if (array.values.length == 1) {

                    // the tree may not be a NEWARRAY for single-element array initializers

                    result = matchAttributeToTree(findme, array.values[0], tree);

                }

            }

            public void visitEnum(Attribute.Enum e) {

            }

            public void visitError(Attribute.Error e) {

            }

        }

        Vis vis = new Vis();

        attr.accept(vis);

        return vis.result;

    }

    /**

     * Scans for a JCAssign node with a LHS matching a given

     * symbol, and returns its RHS.  Does not scan nested JCAnnotations.

     */

    private JCExpression scanForAssign(final MethodSymbol sym,

                                       final JCTree tree) {

        class TS extends TreeScanner {

            JCExpression result = null;

            public void scan(JCTree t) {

                if (t != null && result == null)

                    t.accept(this);

            }

            public void visitAnnotation(JCAnnotation t) {

                if (t == tree)

                    scan(t.args);

            }

            public void visitAssign(JCAssign t) {

                if (t.lhs.hasTag(IDENT)) {

                    JCIdent ident = (JCIdent) t.lhs;

                    if (ident.sym == sym)

                        result = t.rhs;

                }

            }

        }

        TS scanner = new TS();

        tree.accept(scanner);

        return scanner.result;

    }

    /**

     * Returns the tree node corresponding to this element, or null

     * if none can be found.

     */

    public JCTree getTree(Element e) {

        Pair<JCTree, ?> treeTop = getTreeAndTopLevel(e);

        return (treeTop != null) ? treeTop.fst : null;

    }

    @DefinedBy(Api.LANGUAGE_MODEL)

    public String getDocComment(Element e) {

        // Our doc comment is contained in a map in our toplevel,

        // indexed by our tree.  Find our enter environment, which gives

        // us our toplevel.  It also gives us a tree that contains our

        // tree:  walk it to find our tree.  This is painful.

        Pair<JCTree, JCCompilationUnit> treeTop = getTreeAndTopLevel(e);

        if (treeTop == null)

            return null;

        JCTree tree = treeTop.fst;

        JCCompilationUnit toplevel = treeTop.snd;

        if (toplevel.docComments == null)

            return null;

        return toplevel.docComments.getCommentText(tree);

    }

    @DefinedBy(Api.LANGUAGE_MODEL)

    public PackageElement getPackageOf(Element e) {

        return cast(Symbol.class, e).packge();

    }

    @DefinedBy(Api.LANGUAGE_MODEL)

    public ModuleElement getModuleOf(Element e) {

        Symbol sym = cast(Symbol.class, e);

        if (modules.getDefaultModule() == syms.noModule)

            return null;

        return (sym.kind == MDL) ? ((ModuleElement) e) : sym.packge().modle;

    }

    @DefinedBy(Api.LANGUAGE_MODEL)

    public boolean isDeprecated(Element e) {

        Symbol sym = cast(Symbol.class, e);

        return sym.isDeprecated();

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public Origin getOrigin(Element e) {

        Symbol sym = cast(Symbol.class, e);

        if ((sym.flags() & Flags.GENERATEDCONSTR) != 0)

            return Origin.MANDATED;

        //TypeElement.getEnclosedElements does not return synthetic elements,

        //and most synthetic elements are not read from the classfile anyway:

        return Origin.EXPLICIT;

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public Origin getOrigin(AnnotatedConstruct c, AnnotationMirror a) {

        Compound ac = cast(Compound.class, a);

        if (ac.isSynthesized())

            return Origin.MANDATED;

        return Origin.EXPLICIT;

    }

    @Override @DefinedBy(Api.LANGUAGE_MODEL)

    public Origin getOrigin(ModuleElement m, ModuleElement.Directive directive) {

        switch (directive.getKind()) {

            case REQUIRES:

                RequiresDirective rd = cast(RequiresDirective.class, directive);

                if (rd.flags.contains(RequiresFlag.MANDATED))

                    return Origin.MANDATED;

                if (rd.flags.contains(RequiresFlag.SYNTHETIC))

                    return Origin.SYNTHETIC;

                return Origin.EXPLICIT;

            case EXPORTS:

                ExportsDirective ed = cast(ExportsDirective.class, directive);

                if (ed.flags.contains(ExportsFlag.MANDATED))

                    return Origin.MANDATED;

                if (ed.flags.contains(ExportsFlag.SYNTHETIC))

                    return Origin.SYNTHETIC;

                return Origin.EXPLICIT;

            case OPENS:

                OpensDirective od = cast(OpensDirective.class, directive);

                if (od.flags.contains(OpensFlag.MANDATED))

                    return Origin.MANDATED;

                if (od.flags.contains(OpensFlag.SYNTHETIC))

                    return Origin.SYNTHETIC;

                return Origin.EXPLICIT;

        }

        return Origin.EXPLICIT;

    }

    @DefinedBy(Api.LANGUAGE_MODEL)

    public Name getBinaryName(TypeElement type) {

        return cast(TypeSymbol.class, type).flatName();

    }