/*

 * Copyright (c) 1999, 2009, 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 java.util.*;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

/** This pass translates away some syntactic sugar: inner classes,

 *  class literals, assertions, foreach loops, etc.

 *

 *  <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 Lower extends TreeTranslator {

    protected static final Context.Key<Lower> lowerKey =

        new Context.Key<Lower>();

    public static Lower instance(Context context) {

        Lower instance = context.get(lowerKey);

        if (instance == null)

            instance = new Lower(context);

        return instance;

    }

    private Names names;

    private Log log;

    private Symtab syms;

    private Resolve rs;

    private Check chk;

    private Attr attr;

    private TreeMaker make;

    private DiagnosticPosition make_pos;

    private ClassWriter writer;

    private ClassReader reader;

    private ConstFold cfolder;

    private Target target;

    private Source source;

    private boolean allowEnums;

    private final Name dollarAssertionsDisabled;

    private final Name classDollar;

    private Types types;

    private boolean debugLower;

    protected Lower(Context context) {

        context.put(lowerKey, this);

        names = Names.instance(context);

        log = Log.instance(context);

        syms = Symtab.instance(context);

        rs = Resolve.instance(context);

        chk = Check.instance(context);

        attr = Attr.instance(context);

        make = TreeMaker.instance(context);

        writer = ClassWriter.instance(context);

        reader = ClassReader.instance(context);

        cfolder = ConstFold.instance(context);

        target = Target.instance(context);

        source = Source.instance(context);

        allowEnums = source.allowEnums();

        dollarAssertionsDisabled = names.

            fromString(target.syntheticNameChar() + "assertionsDisabled");

        classDollar = names.

            fromString("class" + target.syntheticNameChar());

        types = Types.instance(context);

        Options options = Options.instance(context);

        debugLower = options.get("debuglower") != null;

    }

    /** The currently enclosing class.

     */

    ClassSymbol currentClass;

    /** A queue of all translated classes.

     */

    ListBuffer<JCTree> translated;

    /** Environment for symbol lookup, set by translateTopLevelClass.

     */

    Env<AttrContext> attrEnv;

    /** A hash table mapping syntax trees to their ending source positions.

     */

    Map<JCTree, Integer> endPositions;

/**************************************************************************

 * Global mappings

 *************************************************************************/

    /** A hash table mapping local classes to their definitions.

     */

    Map<ClassSymbol, JCClassDecl> classdefs;

    /** A hash table mapping virtual accessed symbols in outer subclasses

     *  to the actually referred symbol in superclasses.

     */

    Map<Symbol,Symbol> actualSymbols;

    /** The current method definition.

     */

    JCMethodDecl currentMethodDef;

    /** The current method symbol.

     */

    MethodSymbol currentMethodSym;

    /** The currently enclosing outermost class definition.

     */

    JCClassDecl outermostClassDef;

    /** The currently enclosing outermost member definition.

     */

    JCTree outermostMemberDef;

    /** A navigator class for assembling a mapping from local class symbols

     *  to class definition trees.

     *  There is only one case; all other cases simply traverse down the tree.

     */

    class ClassMap extends TreeScanner {

        /** All encountered class defs are entered into classdefs table.

         */

        public void visitClassDef(JCClassDecl tree) {

            classdefs.put(tree.sym, tree);

            super.visitClassDef(tree);

        }

    }

    ClassMap classMap = new ClassMap();

    /** Map a class symbol to its definition.

     *  @param c    The class symbol of which we want to determine the definition.

     */

    JCClassDecl classDef(ClassSymbol c) {

        // First lookup the class in the classdefs table.

        JCClassDecl def = classdefs.get(c);

        if (def == null && outermostMemberDef != null) {

            // If this fails, traverse outermost member definition, entering all

            // local classes into classdefs, and try again.

            classMap.scan(outermostMemberDef);

            def = classdefs.get(c);

        }

        if (def == null) {

            // If this fails, traverse outermost class definition, entering all

            // local classes into classdefs, and try again.

            classMap.scan(outermostClassDef);

            def = classdefs.get(c);

        }

        return def;

    }

    /** A hash table mapping class symbols to lists of free variables.

     *  accessed by them. Only free variables of the method immediately containing

     *  a class are associated with that class.

     */

    Map<ClassSymbol,List<VarSymbol>> freevarCache;

    /** A navigator class for collecting the free variables accessed

     *  from a local class.

     *  There is only one case; all other cases simply traverse down the tree.

     */

    class FreeVarCollector extends TreeScanner {

        /** The owner of the local class.

         */

        Symbol owner;

        /** The local class.

         */

        ClassSymbol clazz;

        /** The list of owner's variables accessed from within the local class,

         *  without any duplicates.

         */

        List<VarSymbol> fvs;

        FreeVarCollector(ClassSymbol clazz) {

            this.clazz = clazz;

            this.owner = clazz.owner;

            this.fvs = List.nil();

        }

        /** Add free variable to fvs list unless it is already there.

         */

        private void addFreeVar(VarSymbol v) {

            for (List<VarSymbol> l = fvs; l.nonEmpty(); l = l.tail)

                if (l.head == v) return;

            fvs = fvs.prepend(v);

        }

        /** Add all free variables of class c to fvs list

         *  unless they are already there.

         */

        private void addFreeVars(ClassSymbol c) {

            List<VarSymbol> fvs = freevarCache.get(c);

            if (fvs != null) {

                for (List<VarSymbol> l = fvs; l.nonEmpty(); l = l.tail) {

                    addFreeVar(l.head);

                }

            }

        }

        /** If tree refers to a variable in owner of local class, add it to

         *  free variables list.

         */

        public void visitIdent(JCIdent tree) {

            result = tree;

            visitSymbol(tree.sym);

        }

        // where

        private void visitSymbol(Symbol _sym) {

            Symbol sym = _sym;

            if (sym.kind == VAR || sym.kind == MTH) {

                while (sym != null && sym.owner != owner)

                    sym = proxies.lookup(proxyName(sym.name)).sym;

                if (sym != null && sym.owner == owner) {

                    VarSymbol v = (VarSymbol)sym;

                    if (v.getConstValue() == null) {

                        addFreeVar(v);

                    }

                } else {

                    if (outerThisStack.head != null &&

                        outerThisStack.head != _sym)

                        visitSymbol(outerThisStack.head);

                }

            }

        }

        /** If tree refers to a class instance creation expression

         *  add all free variables of the freshly created class.

         */

        public void visitNewClass(JCNewClass tree) {

            ClassSymbol c = (ClassSymbol)tree.constructor.owner;

            addFreeVars(c);

            if (tree.encl == null &&

                c.hasOuterInstance() &&

                outerThisStack.head != null)

                visitSymbol(outerThisStack.head);

            super.visitNewClass(tree);

        }

        /** If tree refers to a qualified this or super expression

         *  for anything but the current class, add the outer this

         *  stack as a free variable.

         */

        public void visitSelect(JCFieldAccess tree) {

            if ((tree.name == names._this || tree.name == names._super) &&

                tree.selected.type.tsym != clazz &&

                outerThisStack.head != null)

                visitSymbol(outerThisStack.head);

            super.visitSelect(tree);

        }

        /** If tree refers to a superclass constructor call,

         *  add all free variables of the superclass.

         */

        public void visitApply(JCMethodInvocation tree) {

            if (TreeInfo.name(tree.meth) == names._super) {

                addFreeVars((ClassSymbol) TreeInfo.symbol(tree.meth).owner);

                Symbol constructor = TreeInfo.symbol(tree.meth);

                ClassSymbol c = (ClassSymbol)constructor.owner;

                if (c.hasOuterInstance() &&

                    tree.meth.getTag() != JCTree.SELECT &&

                    outerThisStack.head != null)

                    visitSymbol(outerThisStack.head);

            }

            super.visitApply(tree);

        }

    }

    /** Return the variables accessed from within a local class, which

     *  are declared in the local class' owner.

     *  (in reverse order of first access).

     */

    List<VarSymbol> freevars(ClassSymbol c)  {

        if ((c.owner.kind & (VAR | MTH)) != 0) {

            List<VarSymbol> fvs = freevarCache.get(c);

            if (fvs == null) {

                FreeVarCollector collector = new FreeVarCollector(c);

                collector.scan(classDef(c));

                fvs = collector.fvs;

                freevarCache.put(c, fvs);

            }

            return fvs;

        } else {

            return List.nil();

        }

    }

    Map<TypeSymbol,EnumMapping> enumSwitchMap = new LinkedHashMap<TypeSymbol,EnumMapping>();

    EnumMapping mapForEnum(DiagnosticPosition pos, TypeSymbol enumClass) {

        EnumMapping map = enumSwitchMap.get(enumClass);

        if (map == null)

            enumSwitchMap.put(enumClass, map = new EnumMapping(pos, enumClass));

        return map;

    }

    /** This map gives a translation table to be used for enum

     *  switches.

     *

     *  <p>For each enum that appears as the type of a switch

     *  expression, we maintain an EnumMapping to assist in the

     *  translation, as exemplified by the following example:

     *

     *  <p>we translate

     *  <pre>

     *          switch(colorExpression) {

     *          case red: stmt1;

     *          case green: stmt2;

     *          }

     *  </pre>

     *  into

     *  <pre>

     *          switch(Outer$0.$EnumMap$Color[colorExpression.ordinal()]) {

     *          case 1: stmt1;

     *          case 2: stmt2

     *          }

     *  </pre>

     *  with the auxiliary table initialized as follows:

     *  <pre>

     *          class Outer$0 {

     *              synthetic final int[] $EnumMap$Color = new int[Color.values().length];

     *              static {

     *                  try { $EnumMap$Color[red.ordinal()] = 1; } catch (NoSuchFieldError ex) {}

     *                  try { $EnumMap$Color[green.ordinal()] = 2; } catch (NoSuchFieldError ex) {}

     *              }

     *          }

     *  </pre>

     *  class EnumMapping provides mapping data and support methods for this translation.

     */

    class EnumMapping {

        EnumMapping(DiagnosticPosition pos, TypeSymbol forEnum) {

            this.forEnum = forEnum;

            this.values = new LinkedHashMap<VarSymbol,Integer>();

            this.pos = pos;

            Name varName = names

                .fromString(target.syntheticNameChar() +

                            "SwitchMap" +

                            target.syntheticNameChar() +

                            writer.xClassName(forEnum.type).toString()

                            .replace('/', '.')

                            .replace('.', target.syntheticNameChar()));

            ClassSymbol outerCacheClass = outerCacheClass();

            this.mapVar = new VarSymbol(STATIC | SYNTHETIC | FINAL,

                                        varName,

                                        new ArrayType(syms.intType, syms.arrayClass),

                                        outerCacheClass);

            enterSynthetic(pos, mapVar, outerCacheClass.members());

        }

        DiagnosticPosition pos = null;

        // the next value to use

        int next = 1; // 0 (unused map elements) go to the default label

        // the enum for which this is a map

        final TypeSymbol forEnum;

        // the field containing the map

        final VarSymbol mapVar;

        // the mapped values

        final Map<VarSymbol,Integer> values;

        JCLiteral forConstant(VarSymbol v) {

            Integer result = values.get(v);

            if (result == null)

                values.put(v, result = next++);

            return make.Literal(result);

        }

        // generate the field initializer for the map

        void translate() {

            make.at(pos.getStartPosition());

            JCClassDecl owner = classDef((ClassSymbol)mapVar.owner);

            // synthetic static final int[] $SwitchMap$Color = new int[Color.values().length];

            MethodSymbol valuesMethod = lookupMethod(pos,

                                                     names.values,

                                                     forEnum.type,

                                                     List.<Type>nil());

            JCExpression size = make // Color.values().length

                .Select(make.App(make.QualIdent(valuesMethod)),

                        syms.lengthVar);

            JCExpression mapVarInit = make

                .NewArray(make.Type(syms.intType), List.of(size), null)

                .setType(new ArrayType(syms.intType, syms.arrayClass));

            // try { $SwitchMap$Color[red.ordinal()] = 1; } catch (java.lang.NoSuchFieldError ex) {}

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

            Symbol ordinalMethod = lookupMethod(pos,

                                                names.ordinal,

                                                forEnum.type,

                                                List.<Type>nil());

            List<JCCatch> catcher = List.<JCCatch>nil()

                .prepend(make.Catch(make.VarDef(new VarSymbol(PARAMETER, names.ex,

                                                              syms.noSuchFieldErrorType,

                                                              syms.noSymbol),

                                                null),

                                    make.Block(0, List.<JCStatement>nil())));

            for (Map.Entry<VarSymbol,Integer> e : values.entrySet()) {

                VarSymbol enumerator = e.getKey();

                Integer mappedValue = e.getValue();

                JCExpression assign = make

                    .Assign(make.Indexed(mapVar,

                                         make.App(make.Select(make.QualIdent(enumerator),

                                                              ordinalMethod))),

                            make.Literal(mappedValue))

                    .setType(syms.intType);

                JCStatement exec = make.Exec(assign);

                JCStatement _try = make.Try(make.Block(0, List.of(exec)), catcher, null);

                stmts.append(_try);

            }

            owner.defs = owner.defs

                .prepend(make.Block(STATIC, stmts.toList()))

                .prepend(make.VarDef(mapVar, mapVarInit));

        }

    }

/**************************************************************************

 * Tree building blocks

 *************************************************************************/

    /** Equivalent to make.at(pos.getStartPosition()) with side effect of caching

     *  pos as make_pos, for use in diagnostics.

     **/

    TreeMaker make_at(DiagnosticPosition pos) {

        make_pos = pos;

        return make.at(pos);

    }

    /** Make an attributed tree representing a literal. This will be an

     *  Ident node in the case of boolean literals, a Literal node in all

     *  other cases.

     *  @param type       The literal's type.

     *  @param value      The literal's value.

     */

    JCExpression makeLit(Type type, Object value) {

        return make.Literal(type.tag, value).setType(type.constType(value));

    }

    /** Make an attributed tree representing null.

     */

    JCExpression makeNull() {

        return makeLit(syms.botType, null);

    }

    /** Make an attributed class instance creation expression.

     *  @param ctype    The class type.

     *  @param args     The constructor arguments.

     */

    JCNewClass makeNewClass(Type ctype, List<JCExpression> args) {

        JCNewClass tree = make.NewClass(null,

            null, make.QualIdent(ctype.tsym), args, null);

        tree.constructor = rs.resolveConstructor(

            make_pos, attrEnv, ctype, TreeInfo.types(args), null, false, false);

        tree.type = ctype;

        return tree;

    }

    /** Make an attributed unary expression.

     *  @param optag    The operators tree tag.

     *  @param arg      The operator's argument.

     */

    JCUnary makeUnary(int optag, JCExpression arg) {

        JCUnary tree = make.Unary(optag, arg);

        tree.operator = rs.resolveUnaryOperator(

            make_pos, optag, attrEnv, arg.type);

        tree.type = tree.operator.type.getReturnType();

        return tree;

    }

    /** Make an attributed binary expression.

     *  @param optag    The operators tree tag.

     *  @param lhs      The operator's left argument.

     *  @param rhs      The operator's right argument.

     */

    JCBinary makeBinary(int optag, JCExpression lhs, JCExpression rhs) {

        JCBinary tree = make.Binary(optag, lhs, rhs);

        tree.operator = rs.resolveBinaryOperator(

            make_pos, optag, attrEnv, lhs.type, rhs.type);

        tree.type = tree.operator.type.getReturnType();

        return tree;

    }