/*
 * Copyright (c) 2015, 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 jdk.jshell;

import com.sun.tools.javac.code.Source;
import com.sun.tools.javac.parser.Scanner;
import com.sun.tools.javac.parser.ScannerFactory;
import com.sun.tools.javac.parser.Tokens.Token;
import com.sun.tools.javac.parser.Tokens.TokenKind;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.DiagnosticSource;
import com.sun.tools.javac.util.JCDiagnostic;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticFlag;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
import com.sun.tools.javac.util.JCDiagnostic.Error;
import com.sun.tools.javac.util.Log;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.EnumMap;
import java.util.Iterator;
import jdk.jshell.SourceCodeAnalysis.Completeness;
import com.sun.source.tree.Tree;
import static jdk.jshell.CompletenessAnalyzer.TK.*;
import jdk.jshell.TaskFactory.ParseTask;
import jdk.jshell.TaskFactory.Worker;
import java.util.List;
import java.util.function.Function;
import java.util.function.Supplier;

Low level scanner to determine completeness of input.
Author:
Robert Field/**
 * Low level scanner to determine completeness of input.
 * @author Robert Field
 */
class CompletenessAnalyzer {

    private final ScannerFactory scannerFactory;
    private final JShell proc;

    private static Completeness error() {
        return Completeness.UNKNOWN;  // For breakpointing
    }

    static class CaInfo {

        CaInfo(Completeness status, int unitEndPos) {
            this.status = status;
            this.unitEndPos = unitEndPos;
        }
        final int unitEndPos;
        final Completeness status;
    }

    CompletenessAnalyzer(JShell proc) {
        this.proc = proc;
        Context context = new Context();
        Log log = CaLog.createLog(context);
        context.put(Log.class, log);
        context.put(Source.class, Source.JDK9);
        scannerFactory = ScannerFactory.instance(context);
    }

    CaInfo scan(String s) {
        try {
            Parser parser = new Parser(
                    () -> new Matched(scannerFactory.newScanner(s, false)),
                    worker -> proc.taskFactory.parse(s, worker));
            Completeness stat = parser.parseUnit();
            int endPos = stat == Completeness.UNKNOWN
                    ? s.length()
                    : parser.endPos();
            return new CaInfo(stat, endPos);
        } catch (SyntaxException ex) {
            return new CaInfo(error(), s.length());
        }
    }

    @SuppressWarnings("serial")             // serialVersionUID intentionally omitted
    private static class SyntaxException extends RuntimeException {
    }

    private static void die() {
        throw new SyntaxException();
    }

    
Subclass of Log used by compiler API to die on error and ignore
other messages
/**
     * Subclass of Log used by compiler API to die on error and ignore
     * other messages
     */
    private static class CaLog extends Log {

        private static CaLog createLog(Context context) {
            PrintWriter pw = new PrintWriter(new StringWriter());
            CaLog log = new CaLog(context, pw);
            context.put(logKey, log);
            return log;
        }

        private CaLog(Context context, PrintWriter pw) {
            super(context, pw);
            this.source = DiagnosticSource.NO_SOURCE;
        }

        @Override
        public void error(String key, Object... args) {
            die();
        }

        @Override
        public void error(int pos, Error errorKey) {
            die();
        }

        @Override
        public void error(int pos, String key, Object... args) {
            die();
        }

        @Override
        public void report(JCDiagnostic diagnostic) {
            // Ignore
        }
    }

    // Location position kinds -- a token is ...
    private static final int XEXPR         = 0b1;                       // OK in expression (not first)
    private static final int XDECL         = 0b10;                      // OK in declaration (not first)
    private static final int XSTMT         = 0b100;                     // OK in statement framework (not first)
    private static final int XEXPR1o       = 0b1000;                    // OK first in expression
    private static final int XDECL1o       = 0b10000;                   // OK first in declaration
    private static final int XSTMT1o       = 0b100000;                  // OK first or only in statement framework
    private static final int XEXPR1        = XEXPR1o | XEXPR;           // OK in expression (anywhere)
    private static final int XDECL1        = XDECL1o | XDECL;           // OK in declaration (anywhere)
    private static final int XSTMT1        = XSTMT1o | XSTMT;           // OK in statement framework (anywhere)
    private static final int XANY1         = XEXPR1o | XDECL1o | XSTMT1o;  // Mask: first in statement, declaration, or expression
    private static final int XTERM         = 0b100000000;               // Can terminate (last before EOF)
    private static final int XSTART        = 0b1000000000;              // Boundary, must be XTERM before
    private static final int XERRO         = 0b10000000000;             // Is an error
    private static final int XBRACESNEEDED = 0b100000000000;            // Expect {ANY} LBRACE

    
An extension of the compiler's TokenKind which adds our combined/processed
kinds. Also associates each TK with a union of acceptable kinds of code
position it can occupy.  For example: IDENTIFER is XEXPR1|XDECL1|XTERM,
meaning it can occur in expressions or declarations (but not in the
framework of a statement and that can be the final (terminating) token
in a snippet.

There must be a TK defined for each compiler TokenKind, an exception
will
be thrown if a TokenKind is defined and a corresponding TK is not. Add a
new TK in the appropriate category. If it is like an existing category
(e.g. a new modifier or type this may be all that is needed.  If it
is bracketing or modifies the acceptable positions of other tokens,
please closely examine the needed changes to this scanner.
/**
     * An extension of the compiler's TokenKind which adds our combined/processed
     * kinds. Also associates each TK with a union of acceptable kinds of code
     * position it can occupy.  For example: IDENTIFER is XEXPR1|XDECL1|XTERM,
     * meaning it can occur in expressions or declarations (but not in the
     * framework of a statement and that can be the final (terminating) token
     * in a snippet.
     * <P>
     * There must be a TK defined for each compiler TokenKind, an exception
     * will
     * be thrown if a TokenKind is defined and a corresponding TK is not. Add a
     * new TK in the appropriate category. If it is like an existing category
     * (e.g. a new modifier or type this may be all that is needed.  If it
     * is bracketing or modifies the acceptable positions of other tokens,
     * please closely examine the needed changes to this scanner.
     */
    static enum TK {

        // Special
        EOF(TokenKind.EOF, 0),  //
        ERROR(TokenKind.ERROR, XERRO),  //
        IDENTIFIER(TokenKind.IDENTIFIER, XEXPR1|XDECL1|XTERM),  //
        UNDERSCORE(TokenKind.UNDERSCORE, XERRO),  //  _
        CLASS(TokenKind.CLASS, XEXPR|XDECL1|XBRACESNEEDED),  //  class decl (MAPPED: DOTCLASS)
        MONKEYS_AT(TokenKind.MONKEYS_AT, XEXPR|XDECL1),  //  @
        IMPORT(TokenKind.IMPORT, XDECL1|XSTART),  //  import -- consider declaration
        SEMI(TokenKind.SEMI, XSTMT1|XTERM|XSTART),  //  ;

        // Shouldn't see -- error
        PACKAGE(TokenKind.PACKAGE, XERRO),  //  package
        CONST(TokenKind.CONST, XERRO),  //  reserved keyword -- const
        GOTO(TokenKind.GOTO, XERRO),  //  reserved keyword -- goto
        CUSTOM(TokenKind.CUSTOM, XERRO),  // No uses

        // Declarations
        ENUM(TokenKind.ENUM, XDECL1|XBRACESNEEDED),  //  enum
        IMPLEMENTS(TokenKind.IMPLEMENTS, XDECL),  //  implements
        INTERFACE(TokenKind.INTERFACE, XDECL1|XBRACESNEEDED),  //  interface
        THROWS(TokenKind.THROWS, XDECL|XBRACESNEEDED),  //  throws

        // Primarive type names
        BOOLEAN(TokenKind.BOOLEAN, XEXPR1|XDECL1),  //  boolean
        BYTE(TokenKind.BYTE, XEXPR1|XDECL1),  //  byte
        CHAR(TokenKind.CHAR, XEXPR1|XDECL1),  //  char
        DOUBLE(TokenKind.DOUBLE, XEXPR1|XDECL1),  //  double
        FLOAT(TokenKind.FLOAT, XEXPR1|XDECL1),  //  float
        INT(TokenKind.INT, XEXPR1|XDECL1),  //  int
        LONG(TokenKind.LONG, XEXPR1|XDECL1),  //  long
        SHORT(TokenKind.SHORT, XEXPR1|XDECL1),  //  short
        VOID(TokenKind.VOID, XEXPR1|XDECL1),  //  void

        // Modifiers keywords
        ABSTRACT(TokenKind.ABSTRACT, XDECL1),  //  abstract
        FINAL(TokenKind.FINAL, XDECL1),  //  final
        NATIVE(TokenKind.NATIVE, XDECL1),  //  native
        STATIC(TokenKind.STATIC, XDECL1),  //  static
        STRICTFP(TokenKind.STRICTFP, XDECL1),  //  strictfp
        PRIVATE(TokenKind.PRIVATE, XDECL1),  //  private
        PROTECTED(TokenKind.PROTECTED, XDECL1),  //  protected
        PUBLIC(TokenKind.PUBLIC, XDECL1),  //  public
        TRANSIENT(TokenKind.TRANSIENT, XDECL1),  //  transient
        VOLATILE(TokenKind.VOLATILE, XDECL1),  //  volatile

        // Declarations and type parameters (thus expressions)
        EXTENDS(TokenKind.EXTENDS, XEXPR|XDECL),  //  extends
        COMMA(TokenKind.COMMA, XEXPR|XDECL),  //  ,
        AMP(TokenKind.AMP, XEXPR|XDECL, true),  //  &
        GT(TokenKind.GT, XEXPR|XDECL, true),  //  >
        LT(TokenKind.LT, XEXPR|XDECL1, true),  //  <
        LTLT(TokenKind.LTLT, XEXPR|XDECL1, true),  //  <<
        GTGT(TokenKind.GTGT, XEXPR|XDECL, true),  //  >>
        GTGTGT(TokenKind.GTGTGT, XEXPR|XDECL, true),  //  >>>
        QUES(TokenKind.QUES, XEXPR|XDECL, true),  //  ?
        DOT(TokenKind.DOT, XEXPR|XDECL),  //  .
        STAR(TokenKind.STAR, XEXPR, true),  //  * (MAPPED: DOTSTAR)

        // Statement keywords
        ASSERT(TokenKind.ASSERT, XSTMT1|XSTART),  //  assert
        BREAK(TokenKind.BREAK, XSTMT1|XTERM|XSTART),  //  break
        CATCH(TokenKind.CATCH, XSTMT1|XSTART),  //  catch
        CONTINUE(TokenKind.CONTINUE, XSTMT1|XTERM|XSTART),  //  continue
        DO(TokenKind.DO, XSTMT1|XSTART),  //  do
        ELSE(TokenKind.ELSE, XSTMT1|XTERM|XSTART),  //  else
        FINALLY(TokenKind.FINALLY, XSTMT1|XSTART),  //  finally
        FOR(TokenKind.FOR, XSTMT1|XSTART),  //  for
        IF(TokenKind.IF, XSTMT1|XSTART),  //  if
        RETURN(TokenKind.RETURN, XSTMT1|XTERM|XSTART),  //  return
        SWITCH(TokenKind.SWITCH, XSTMT1|XEXPR1),  //  switch
        SYNCHRONIZED(TokenKind.SYNCHRONIZED, XSTMT1|XDECL),  //  synchronized
        THROW(TokenKind.THROW, XSTMT1|XSTART),  //  throw
        TRY(TokenKind.TRY, XSTMT1|XSTART),  //  try
        WHILE(TokenKind.WHILE, XSTMT1|XSTART),  //  while

        // Statement keywords that we shouldn't see -- inside braces
        CASE(TokenKind.CASE, XSTMT|XSTART),  //  case
        DEFAULT(TokenKind.DEFAULT, XSTMT|XSTART),  //  default method, default case -- neither we should see

        // Expressions (can terminate)
        INTLITERAL(TokenKind.INTLITERAL, XEXPR1|XTERM),  //
        LONGLITERAL(TokenKind.LONGLITERAL, XEXPR1|XTERM),  //
        FLOATLITERAL(TokenKind.FLOATLITERAL, XEXPR1|XTERM),  //
        DOUBLELITERAL(TokenKind.DOUBLELITERAL, XEXPR1|XTERM),  //
        CHARLITERAL(TokenKind.CHARLITERAL, XEXPR1|XTERM),  //
        STRINGLITERAL(TokenKind.STRINGLITERAL, XEXPR1|XTERM),  //
        TRUE(TokenKind.TRUE, XEXPR1|XTERM),  //  true
        FALSE(TokenKind.FALSE, XEXPR1|XTERM),  //  false
        NULL(TokenKind.NULL, XEXPR1|XTERM),  //  null
        THIS(TokenKind.THIS, XEXPR1|XTERM),  //  this  -- shouldn't see

        // Expressions maybe terminate  //TODO handle these case separately
        PLUSPLUS(TokenKind.PLUSPLUS, XEXPR1|XTERM),  //  ++
        SUBSUB(TokenKind.SUBSUB, XEXPR1|XTERM),  //  --

        // Expressions cannot terminate
        INSTANCEOF(TokenKind.INSTANCEOF, XEXPR, true),  //  instanceof
        NEW(TokenKind.NEW, XEXPR1),  //  new (MAPPED: COLCOLNEW)
        SUPER(TokenKind.SUPER, XEXPR1|XDECL),  //  super -- shouldn't see as rec. But in type parameters
        ARROW(TokenKind.ARROW, XEXPR),  //  ->
        COLCOL(TokenKind.COLCOL, XEXPR),  //  ::
        LPAREN(TokenKind.LPAREN, XEXPR),  //  (
        RPAREN(TokenKind.RPAREN, XEXPR),  //  )
        LBRACE(TokenKind.LBRACE, XEXPR),  //  {
        RBRACE(TokenKind.RBRACE, XEXPR),  //  }
        LBRACKET(TokenKind.LBRACKET, XEXPR),  //  [
        RBRACKET(TokenKind.RBRACKET, XEXPR),  //  ]
        ELLIPSIS(TokenKind.ELLIPSIS, XEXPR),  //  ...
        EQ(TokenKind.EQ, XEXPR),  //  =
        BANG(TokenKind.BANG, XEXPR1),  //  !
        TILDE(TokenKind.TILDE, XEXPR1),  //  ~
        COLON(TokenKind.COLON, XEXPR|XTERM),  //  :
        EQEQ(TokenKind.EQEQ, XEXPR, true),  //  ==
        LTEQ(TokenKind.LTEQ, XEXPR, true),  //  <=
        GTEQ(TokenKind.GTEQ, XEXPR, true),  //  >=
        BANGEQ(TokenKind.BANGEQ, XEXPR, true),  //  !=
        AMPAMP(TokenKind.AMPAMP, XEXPR, true),  //  &&
        BARBAR(TokenKind.BARBAR, XEXPR, true),  //  ||
        PLUS(TokenKind.PLUS, XEXPR1, true),  //  +
        SUB(TokenKind.SUB, XEXPR1, true),  //  -
        SLASH(TokenKind.SLASH, XEXPR, true),  //  /
        BAR(TokenKind.BAR, XEXPR, true),  //  |
        CARET(TokenKind.CARET, XEXPR, true),  //  ^
        PERCENT(TokenKind.PERCENT, XEXPR, true),  //  %
        PLUSEQ(TokenKind.PLUSEQ, XEXPR),  //  +=
        SUBEQ(TokenKind.SUBEQ, XEXPR),  //  -=
        STAREQ(TokenKind.STAREQ, XEXPR),  //  *=
        SLASHEQ(TokenKind.SLASHEQ, XEXPR),  //  /=
        AMPEQ(TokenKind.AMPEQ, XEXPR),  //  &=
        BAREQ(TokenKind.BAREQ, XEXPR),  //  |=
        CARETEQ(TokenKind.CARETEQ, XEXPR),  //  ^=
        PERCENTEQ(TokenKind.PERCENTEQ, XEXPR),  //  %=
        LTLTEQ(TokenKind.LTLTEQ, XEXPR),  //  <<=
        GTGTEQ(TokenKind.GTGTEQ, XEXPR),  //  >>=
        GTGTGTEQ(TokenKind.GTGTGTEQ, XEXPR),  //  >>>=

        // combined/processed kinds
        UNMATCHED(XERRO),
        PARENS(XEXPR1|XDECL|XSTMT|XTERM),
        BRACKETS(XEXPR|XDECL|XTERM),
        BRACES(XSTMT1|XEXPR|XTERM),
        DOTSTAR(XDECL|XTERM),  // import foo.*
        COLCOLNEW(XEXPR|XTERM),  //  :: new
        DOTCLASS(XEXPR|XTERM),  //  class decl and .class
        ;

        static final EnumMap<TokenKind,TK> tokenKindToTKMap = new EnumMap<>(TokenKind.class);

        final TokenKind tokenKind;
        final int belongs;
        final boolean valueOp;
        Function<TK,TK> mapping;

        TK(int b) {
            this(null, b);
        }

        TK(TokenKind tokenKind, int b) {
            this(tokenKind, b, false);
        }

        TK(TokenKind tokenKind, int b, boolean valueOp) {
            this.tokenKind = tokenKind;
            this.belongs = b;
            this.valueOp = valueOp;
            this.mapping = null;
        }

        private static TK tokenKindToTK(TK prev, TokenKind kind) {
            TK tk = tokenKindToTKMap.get(kind);
            if (tk == null) {
                System.err.printf("No corresponding %s for %s: %s\n",
                        TK.class.getCanonicalName(),
                        TokenKind.class.getCanonicalName(),
                        kind);
                throw new InternalError("No corresponding TK for TokenKind: " + kind);
            }
            return tk.mapping != null
                    ? tk.mapping.apply(prev)
                    : tk;
        }

        boolean isOkToTerminate() {
            return (belongs & XTERM) != 0;
        }

        boolean isExpression() {
            return (belongs & XEXPR) != 0;
        }

        boolean isDeclaration() {
            return (belongs & XDECL) != 0;
        }

        boolean isError() {
            return (belongs & XERRO) != 0;
        }

        boolean isStart() {
            return (belongs & XSTART) != 0;
        }

        boolean isBracesNeeded() {
            return (belongs & XBRACESNEEDED) != 0;
        }

        
After construction, check that all compiler TokenKind values have
corresponding TK values.
/**
         * After construction, check that all compiler TokenKind values have
         * corresponding TK values.
         */
        static {
            for (TK tk : TK.values()) {
                if (tk.tokenKind != null) {
                    tokenKindToTKMap.put(tk.tokenKind, tk);
                }
            }
            for (TokenKind kind : TokenKind.values()) {
                tokenKindToTK(null, kind); // assure they can be retrieved without error
            }
            // Mappings of disambiguated contexts
            STAR.mapping  = prev -> prev == DOT ? DOTSTAR : STAR;
            NEW.mapping   = prev -> prev == COLCOL ? COLCOLNEW : NEW;
            CLASS.mapping = prev -> prev == DOT ? DOTCLASS : CLASS;
        }
    }

    
A completeness scanner token.
/**
     * A completeness scanner token.
     */
    private static class CT {

        
The token kind /** The token kind */
        public final TK kind;

        
The end position of this token /** The end position of this token */
        public final int endPos;

        
The error message /** The error message **/
        public final String message;

        private CT(TK tk, Token tok, String msg) {
            this.kind = tk;
            this.endPos = tok.endPos;
            this.message = msg;
            //throw new InternalError(msg); /* for debugging */
        }

        private CT(TK tk, Token tok) {
            this.kind = tk;
            this.endPos = tok.endPos;
            this.message = null;
        }

        private CT(TK tk, int endPos) {
            this.kind = tk;
            this.endPos = endPos;
            this.message = null;
        }
    }

    
Look for matching tokens (like parens) and other special cases, like "new"
/**
     * Look for matching tokens (like parens) and other special cases, like "new"
     */
    private static class Matched implements Iterator<CT> {

        private final Scanner scanner;
        private Token current;
        private CT prevCT;
        private CT currentCT;
        private final Deque<Token> stack = new ArrayDeque<>();

        Matched(Scanner scanner) {
            this.scanner = scanner;
            advance();
            prevCT = currentCT = new CT(SEMI, 0); // So is valid for testing
        }

        @Override
        public boolean hasNext() {
            return currentCT.kind != EOF;
        }

        private Token advance() {
            Token prev = current;
            scanner.nextToken();
            current = scanner.token();
            return prev;
        }

        @Override
        public CT next() {
            prevCT = currentCT;
            currentCT = nextCT();
            return currentCT;
        }

        private CT match(TK tk, TokenKind open) {
            Token tok = advance();
            db("match desired-tk=%s, open=%s, seen-tok=%s", tk, open, tok.kind);
            if (stack.isEmpty()) {
                return new CT(ERROR, tok, "Encountered '" + tok + "' with no opening '" + open + "'");
            }
            Token p = stack.pop();
            if (p.kind != open) {
                return new CT(ERROR, tok, "No match for '" + p + "' instead encountered '" + tok + "'");
            }
            return new CT(tk, tok);
        }

        private void db(String format, Object ... args) {
//            System.err.printf(format, args);
//            System.err.printf(" -- stack(");
//            if (stack.isEmpty()) {
//
//            } else {
//                for (Token tok : stack) {
//                    System.err.printf("%s ", tok.kind);
//                }
//            }
//            System.err.printf(") current=%s / currentCT=%s\n", current.kind, currentCT.kind);
        }

        
Returns:
the next scanner token/**
         * @return the next scanner token
         */
        private CT nextCT() {
            // TODO Annotations?
            TK prevTK = currentCT.kind;
            while (true) {
                db("nextCT");
                CT ct;
                switch (current.kind) {
                    case EOF:
                        db("eof");
                        if (stack.isEmpty()) {
                            ct = new CT(EOF, current);
                        } else {
                            TokenKind unmatched = stack.pop().kind;
                            stack.clear(); // So we will get EOF next time
                            ct = new CT(UNMATCHED, current, "Unmatched " + unmatched);
                        }
                        break;
                    case LPAREN:
                    case LBRACE:
                    case LBRACKET:
                        stack.push(advance());
                        prevTK = SEMI; // new start
                        continue;
                    case RPAREN:
                        ct = match(PARENS, TokenKind.LPAREN);
                        break;
                    case RBRACE:
                        ct = match(BRACES, TokenKind.LBRACE);
                        break;
                    case RBRACKET:
                        ct = match(BRACKETS, TokenKind.LBRACKET);
                        break;
                    default:
                        ct = new CT(TK.tokenKindToTK(prevTK, current.kind), advance());
                        break;
                }
                // Detect an error if we are at starting position and the last
                // token wasn't a terminating one.  Special case: within braces,
                // comma can proceed semicolon, e.g. the values list in enum
                if (ct.kind.isStart() && !prevTK.isOkToTerminate() && prevTK != COMMA) {
                    return new CT(ERROR, current, "No '" + prevTK + "' before '" + ct.kind + "'");
                }
                if (stack.isEmpty() || ct.kind.isError()) {
                    return ct;
                }
                prevTK = ct.kind;
            }
        }
    }

    
Fuzzy parser based on token kinds
/**
     * Fuzzy parser based on token kinds
     */
    private static class Parser {

        private final Supplier<Matched> matchedFactory;
        private final Function<Worker<ParseTask, Completeness>, Completeness> parseFactory;
        private Matched in;
        private CT token;
        private Completeness checkResult;

        Parser(Supplier<Matched> matchedFactory,
               Function<Worker<ParseTask, Completeness>, Completeness> parseFactory) {
            this.matchedFactory = matchedFactory;
            this.parseFactory = parseFactory;
            resetInput();
        }

        final void resetInput() {
            this.in = matchedFactory.get();
            nextToken();
        }

        final void nextToken() {
            in.next();
            token = in.currentCT;
        }

        boolean shouldAbort(TK tk) {
            if (token.kind == tk) {
                nextToken();
                return false;
            }
            switch (token.kind) {
                case EOF:
                    checkResult = ((tk == SEMI) && in.prevCT.kind.isOkToTerminate())
                            ? Completeness.COMPLETE_WITH_SEMI
                            : Completeness.DEFINITELY_INCOMPLETE;
                    return true;
                case UNMATCHED:
                    checkResult = Completeness.DEFINITELY_INCOMPLETE;
                    return true;
                default:
                    checkResult = error();
                    return true;

            }
        }

        Completeness lastly(TK tk) {
            if (shouldAbort(tk))  return checkResult;
            return Completeness.COMPLETE;
        }

        Completeness optionalFinalSemi() {
            if (!shouldAbort(SEMI)) return Completeness.COMPLETE;
            if (checkResult == Completeness.COMPLETE_WITH_SEMI) return Completeness.COMPLETE;
            return checkResult;
        }

        boolean shouldAbort(Completeness flags) {
            checkResult = flags;
            return flags != Completeness.COMPLETE;
        }

        public int endPos() {
            return in.prevCT.endPos;
        }

        public Completeness parseUnit() {
            //System.err.printf("%s:  belongs %o  XANY1 %o\n", token.kind, token.kind.belongs, token.kind.belongs & XANY1);
            switch (token.kind.belongs & XANY1) {
                case XEXPR1o:
                    return parseExpressionOptionalSemi();
                case XSTMT1o: {
                    Completeness stat = parseSimpleStatement();
                    return stat==null? error() : stat;
                }
                case XDECL1o:
                    return parseDeclaration();
                case XSTMT1o | XDECL1o:
                case XEXPR1o | XDECL1o:
                    return disambiguateDeclarationVsExpression();
                case 0:
                    if ((token.kind.belongs & XERRO) != 0) {
                        return parseExpressionStatement(); // Let this gen the status
                    }
                    return error();
                case XSTMT1o | XEXPR1o:
                    return disambiguateStatementVsExpression();
                default:
                    throw new InternalError("Case not covered " + token.kind.belongs + " in " + token.kind);
            }
        }

        public Completeness parseDeclaration() {
            boolean isImport = token.kind == IMPORT;
            boolean isBracesNeeded = false;
            while (token.kind.isDeclaration()) {
                isBracesNeeded |= token.kind.isBracesNeeded();
                nextToken();
            }
            switch (token.kind) {
                case EQ:
                    nextToken();
                    return parseExpressionStatement();
                case BRACES:
                case SEMI:
                    nextToken();
                    return Completeness.COMPLETE;
                case UNMATCHED:
                    nextToken();
                    return Completeness.DEFINITELY_INCOMPLETE;
                case EOF:
                    switch (in.prevCT.kind) {
                        case BRACES:
                        case SEMI:
                            return Completeness.COMPLETE;
                        case IDENTIFIER:
                            return isBracesNeeded
                                    ? Completeness.DEFINITELY_INCOMPLETE
                                    : Completeness.COMPLETE_WITH_SEMI;
                        case BRACKETS:
                            return Completeness.COMPLETE_WITH_SEMI;
                        case DOTSTAR:
                            if (isImport) {
                                return Completeness.COMPLETE_WITH_SEMI;
                            } else {
                                return Completeness.UNKNOWN;
                            }
                        default:
                            return Completeness.DEFINITELY_INCOMPLETE;
                    }
                default:
                    return error();
            }
        }

        public Completeness disambiguateStatementVsExpression() {
            if (token.kind == SWITCH) {
                nextToken();
                switch (token.kind) {
                    case PARENS:
                        nextToken();
                        break;
                    case UNMATCHED:
                        nextToken();
                        return Completeness.DEFINITELY_INCOMPLETE;
                    case EOF:
                        return Completeness.DEFINITELY_INCOMPLETE;
                    default:
                        return error();
                }
                switch (token.kind) {
                    case BRACES:
                        nextToken();
                        break;
                    case UNMATCHED:
                        nextToken();
                        return Completeness.DEFINITELY_INCOMPLETE;
                    case EOF:
                        return Completeness.DEFINITELY_INCOMPLETE;
                    default:
                        return error();
                }
                if (token.kind.valueOp) {
                    return parseExpressionOptionalSemi();
                } else {
                    return Completeness.COMPLETE;
                }
            } else {
                throw new InternalError("Unexpected statement/expression not covered " + token.kind.belongs + " in " + token.kind);
            }
        }


        public Completeness disambiguateDeclarationVsExpression() {
            // String folding messes up position information.
            return parseFactory.apply(pt -> {
                List<? extends Tree> units = pt.units();
                if (units.isEmpty()) {
                    return error();
                }
                Tree unitTree = units.get(0);
                switch (unitTree.getKind()) {
                    case EXPRESSION_STATEMENT:
                        return parseExpressionOptionalSemi();
                    case LABELED_STATEMENT:
                        if (shouldAbort(IDENTIFIER))  return checkResult;
                        if (shouldAbort(COLON))  return checkResult;
                        return parseStatement();
                    case VARIABLE:
                    case IMPORT:
                    case CLASS:
                    case ENUM:
                    case ANNOTATION_TYPE:
                    case INTERFACE:
                    case METHOD:
                        return parseDeclaration();
                    default:
                        return error();
                }
            });
        }

        public Completeness parseExpressionStatement() {
            if (shouldAbort(parseExpression()))  return checkResult;
            return lastly(SEMI);
        }

        public Completeness parseExpressionOptionalSemi() {
            if (shouldAbort(parseExpression())) return checkResult;
            return optionalFinalSemi();
        }

        public Completeness parseExpression() {
            while (token.kind.isExpression())
                nextToken();
            return Completeness.COMPLETE;
        }

        public Completeness parseStatement() {
            Completeness stat = parseSimpleStatement();
            if (stat == null) {
                return parseExpressionStatement();
            }
            return stat;
        }

        
Statement = Block | IF ParExpression Statement [ELSE Statement] | FOR
"(" ForInitOpt ";" [Expression] ";" ForUpdateOpt ")" Statement | FOR
"(" FormalParameter : Expression ")" Statement | WHILE ParExpression
Statement | DO Statement WHILE ParExpression ";" | TRY Block (
Catches | [Catches] FinallyPart ) | TRY "(" ResourceSpecification
";"opt ")" Block [Catches] [FinallyPart] | SWITCH ParExpression "{"
SwitchBlockStatementGroups "}" | SYNCHRONIZED ParExpression Block |
RETURN [Expression] ";" | THROW Expression ";" | BREAK [Ident] ";" |
CONTINUE [Ident] ";" | ASSERT Expression [ ":" Expression ] ";" | ";"
/**
         * Statement = Block | IF ParExpression Statement [ELSE Statement] | FOR
         * "(" ForInitOpt ";" [Expression] ";" ForUpdateOpt ")" Statement | FOR
         * "(" FormalParameter : Expression ")" Statement | WHILE ParExpression
         * Statement | DO Statement WHILE ParExpression ";" | TRY Block (
         * Catches | [Catches] FinallyPart ) | TRY "(" ResourceSpecification
         * ";"opt ")" Block [Catches] [FinallyPart] | SWITCH ParExpression "{"
         * SwitchBlockStatementGroups "}" | SYNCHRONIZED ParExpression Block |
         * RETURN [Expression] ";" | THROW Expression ";" | BREAK [Ident] ";" |
         * CONTINUE [Ident] ";" | ASSERT Expression [ ":" Expression ] ";" | ";"
         */
        public Completeness parseSimpleStatement() {
            switch (token.kind) {
                case BRACES:
                    return lastly(BRACES);
                case IF: {
                    nextToken();
                    if (shouldAbort(PARENS))  return checkResult;
                    Completeness thenpart = parseStatement();
                    if (shouldAbort(thenpart)) return thenpart;
                    if (token.kind == ELSE) {
                        nextToken();
                        return parseStatement();
                    }
                    return thenpart;

                }
                case FOR: {
                    nextToken();
                    if (shouldAbort(PARENS))  return checkResult;
                    if (shouldAbort(parseStatement()))  return checkResult;
                    return Completeness.COMPLETE;
                }
                case WHILE: {
                    nextToken();
                    if (shouldAbort(PARENS))  return error();
                    return parseStatement();
                }
                case DO: {
                    nextToken();
                    switch (parseStatement()) {
                        case DEFINITELY_INCOMPLETE:
                        case CONSIDERED_INCOMPLETE:
                        case COMPLETE_WITH_SEMI:
                            return Completeness.DEFINITELY_INCOMPLETE;
                        case UNKNOWN:
                            return error();
                        case COMPLETE:
                            break;
                    }
                    if (shouldAbort(WHILE))  return checkResult;
                    if (shouldAbort(PARENS)) return checkResult;
                    return lastly(SEMI);
                }
                case TRY: {
                    boolean hasResources = false;
                    nextToken();
                    if (token.kind == PARENS) {
                        nextToken();
                        hasResources = true;
                    }
                    if (shouldAbort(BRACES))  return checkResult;
                    if (token.kind == CATCH || token.kind == FINALLY) {
                        while (token.kind == CATCH) {
                            if (shouldAbort(CATCH))  return checkResult;
                            if (shouldAbort(PARENS)) return checkResult;
                            if (shouldAbort(BRACES)) return checkResult;
                        }
                        if (token.kind == FINALLY) {
                            if (shouldAbort(FINALLY))  return checkResult;
                            if (shouldAbort(BRACES)) return checkResult;
                        }
                    } else if (!hasResources) {
                        if (token.kind == EOF) {
                            return Completeness.DEFINITELY_INCOMPLETE;
                        } else {
                            return error();
                        }
                    }
                    return Completeness.COMPLETE;
                }
                case SWITCH: {
                    nextToken();
                    if (shouldAbort(PARENS))  return checkResult;
                    return lastly(BRACES);
                }
                case SYNCHRONIZED: {
                    nextToken();
                    if (shouldAbort(PARENS))  return checkResult;
                    return lastly(BRACES);
                }
                case THROW: {
                    nextToken();
                    if (shouldAbort(parseExpression()))  return checkResult;
                    return lastly(SEMI);
                }
                case SEMI:
                    return lastly(SEMI);
                case ASSERT:
                    nextToken();
                    // Crude expression parsing just happily eats the optional colon
                    return parseExpressionStatement();
                case RETURN:
                case BREAK:
                case CONTINUE:
                    nextToken();
                    return parseExpressionStatement();
                // What are these doing here?
                case ELSE:
                case FINALLY:
                case CATCH:
                    return error();
                case EOF:
                    return Completeness.CONSIDERED_INCOMPLETE;
                default:
                    return null;
            }
        }
    }
}