/*

 * Copyright (c) 1999, 2011, 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.parser;

import java.nio.*;

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

import com.sun.tools.javac.file.JavacFileManager;

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

import static com.sun.tools.javac.parser.Token.*;

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

/** The lexical analyzer maps an input stream consisting of

 *  ASCII characters and Unicode escapes into a token sequence.

 *

 *  <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 Scanner implements Lexer {

    private static boolean scannerDebug = false;

    /* Output variables; set by nextToken():

     */

    /** The token, set by nextToken().

     */

    private Token token;

    /** Allow hex floating-point literals.

     */

    private boolean allowHexFloats;

    /** Allow binary literals.

     */

    private boolean allowBinaryLiterals;

    /** Allow underscores in literals.

     */

    private boolean allowUnderscoresInLiterals;

    /** The source language setting.

     */

    private Source source;

    /** The token's position, 0-based offset from beginning of text.

     */

    private int pos;

    /** Character position just after the last character of the token.

     */

    private int endPos;

    /** The last character position of the previous token.

     */

    private int prevEndPos;

    /** The position where a lexical error occurred;

     */

    private int errPos = Position.NOPOS;

    /** The name of an identifier or token:

     */

    private Name name;

    /** The radix of a numeric literal token.

     */

    private int radix;

    /** Has a @deprecated been encountered in last doc comment?

     *  this needs to be reset by client.

     */

    protected boolean deprecatedFlag = false;

    /** A character buffer for literals.

     */

    private char[] sbuf = new char[128];

    private int sp;

    /** The input buffer, index of next chacter to be read,

     *  index of one past last character in buffer.

     */

    private char[] buf;

    private int bp;

    private int buflen;

    private int eofPos;

    /** The current character.

     */

    private char ch;

    /** The buffer index of the last converted unicode character

     */

    private int unicodeConversionBp = -1;

    /** The log to be used for error reporting.

     */

    private final Log log;

    /** The name table. */

    private final Names names;

    /** The keyword table. */

    private final Keywords keywords;

    /** Common code for constructors. */

    private Scanner(ScannerFactory fac) {

        log = fac.log;

        names = fac.names;

        keywords = fac.keywords;

        source = fac.source;

        allowBinaryLiterals = source.allowBinaryLiterals();

        allowHexFloats = source.allowHexFloats();

    }

    private static final boolean hexFloatsWork = hexFloatsWork();

    private static boolean hexFloatsWork() {

        try {

            Float.valueOf("0x1.0p1");

            return true;

        } catch (NumberFormatException ex) {

            return false;

        }

    }

    /** Create a scanner from the input buffer.  buffer must implement

     *  array() and compact(), and remaining() must be less than limit().

     */

    protected Scanner(ScannerFactory fac, CharBuffer buffer) {

        this(fac, JavacFileManager.toArray(buffer), buffer.limit());

    }

    /**

     * Create a scanner from the input array.  This method might

     * modify the array.  To avoid copying the input array, ensure

     * that {@code inputLength < input.length} or

     * {@code input[input.length -1]} is a white space character.

     *

     * @param fac the factory which created this Scanner

     * @param input the input, might be modified

     * @param inputLength the size of the input.

     * Must be positive and less than or equal to input.length.

     */

    protected Scanner(ScannerFactory fac, char[] input, int inputLength) {

        this(fac);

        eofPos = inputLength;

        if (inputLength == input.length) {

            if (input.length > 0 && Character.isWhitespace(input[input.length - 1])) {

                inputLength--;

            } else {

                char[] newInput = new char[inputLength + 1];

                System.arraycopy(input, 0, newInput, 0, input.length);

                input = newInput;

            }

        }

        buf = input;

        buflen = inputLength;

        buf[buflen] = EOI;

        bp = -1;

        scanChar();

    }

    /** Report an error at the given position using the provided arguments.

     */

    private void lexError(int pos, String key, Object... args) {

        log.error(pos, key, args);

        token = ERROR;

        errPos = pos;

    }

    /** Report an error at the current token position using the provided

     *  arguments.

     */

    private void lexError(String key, Object... args) {

        lexError(pos, key, args);

    }

    /** Convert an ASCII digit from its base (8, 10, or 16)

     *  to its value.

     */

    private int digit(int base) {

        char c = ch;

        int result = Character.digit(c, base);

        if (result >= 0 && c > 0x7f) {

            lexError(pos+1, "illegal.nonascii.digit");

            ch = "0123456789abcdef".charAt(result);

        }

        return result;

    }

    /** Convert unicode escape; bp points to initial '\' character

     *  (Spec 3.3).

     */

    private void convertUnicode() {

        if (ch == '\\' && unicodeConversionBp != bp) {

            bp++; ch = buf[bp];

            if (ch == 'u') {

                do {

                    bp++; ch = buf[bp];

                } while (ch == 'u');

                int limit = bp + 3;

                if (limit < buflen) {

                    int d = digit(16);

                    int code = d;

                    while (bp < limit && d >= 0) {

                        bp++; ch = buf[bp];

                        d = digit(16);

                        code = (code << 4) + d;

                    }

                    if (d >= 0) {

                        ch = (char)code;

                        unicodeConversionBp = bp;

                        return;

                    }

                }

                lexError(bp, "illegal.unicode.esc");

            } else {

                bp--;

                ch = '\\';

            }

        }

    }

    /** Read next character.

     */

    private void scanChar() {

        ch = buf[++bp];

        if (ch == '\\') {

            convertUnicode();

        }

    }

    /** Read next character in comment, skipping over double '\' characters.

     */

    private void scanCommentChar() {

        scanChar();

        if (ch == '\\') {

            if (buf[bp+1] == '\\' && unicodeConversionBp != bp) {

                bp++;

            } else {

                convertUnicode();

            }

        }

    }

    /** Append a character to sbuf.

     */

    private void putChar(char ch) {

        if (sp == sbuf.length) {

            char[] newsbuf = new char[sbuf.length * 2];

            System.arraycopy(sbuf, 0, newsbuf, 0, sbuf.length);

            sbuf = newsbuf;

        }

        sbuf[sp++] = ch;

    }

    /** For debugging purposes: print character.

     */

    private void dch() {

        System.err.print(ch); System.out.flush();

    }

    /** Read next character in character or string literal and copy into sbuf.

     */

    private void scanLitChar() {

        if (ch == '\\') {

            if (buf[bp+1] == '\\' && unicodeConversionBp != bp) {

                bp++;

                putChar('\\');

                scanChar();

            } else {

                scanChar();

                switch (ch) {

                case '0': case '1': case '2': case '3':

                case '4': case '5': case '6': case '7':

                    char leadch = ch;

                    int oct = digit(8);

                    scanChar();

                    if ('0' <= ch && ch <= '7') {

                        oct = oct * 8 + digit(8);

                        scanChar();

                        if (leadch <= '3' && '0' <= ch && ch <= '7') {

                            oct = oct * 8 + digit(8);

                            scanChar();

                        }

                    }

                    putChar((char)oct);

                    break;

                case 'b':

                    putChar('\b'); scanChar(); break;

                case 't':

                    putChar('\t'); scanChar(); break;

                case 'n':

                    putChar('\n'); scanChar(); break;

                case 'f':

                    putChar('\f'); scanChar(); break;

                case 'r':

                    putChar('\r'); scanChar(); break;

                case '\'':

                    putChar('\''); scanChar(); break;

                case '\"':

                    putChar('\"'); scanChar(); break;

                case '\\':

                    putChar('\\'); scanChar(); break;

                default:

                    lexError(bp, "illegal.esc.char");

                }

            }

        } else if (bp != buflen) {

            putChar(ch); scanChar();

        }

    }

    private void scanDigits(int digitRadix) {

        char saveCh;

        int savePos;

        do {

            if (ch != '_') {

                putChar(ch);

            } else {

                if (!allowUnderscoresInLiterals) {

                    lexError("unsupported.underscore.lit", source.name);

                    allowUnderscoresInLiterals = true;

                }

            }

            saveCh = ch;

            savePos = bp;

            scanChar();

        } while (digit(digitRadix) >= 0 || ch == '_');

        if (saveCh == '_')

            lexError(savePos, "illegal.underscore");

    }

    /** Read fractional part of hexadecimal floating point number.

     */

    private void scanHexExponentAndSuffix() {

        if (ch == 'p' || ch == 'P') {

            putChar(ch);

            scanChar();

            skipIllegalUnderscores();

            if (ch == '+' || ch == '-') {

                putChar(ch);

                scanChar();

            }

            skipIllegalUnderscores();

            if ('0' <= ch && ch <= '9') {

                scanDigits(10);

                if (!allowHexFloats) {

                    lexError("unsupported.fp.lit", source.name);

                    allowHexFloats = true;

                }

                else if (!hexFloatsWork)

                    lexError("unsupported.cross.fp.lit");

            } else

                lexError("malformed.fp.lit");

        } else {

            lexError("malformed.fp.lit");

        }

        if (ch == 'f' || ch == 'F') {

            putChar(ch);

            scanChar();

            token = FLOATLITERAL;

        } else {

            if (ch == 'd' || ch == 'D') {

                putChar(ch);

                scanChar();

            }

            token = DOUBLELITERAL;

        }

    }

    /** Read fractional part of floating point number.

     */

    private void scanFraction() {

        skipIllegalUnderscores();

        if ('0' <= ch && ch <= '9') {

            scanDigits(10);

        }

        int sp1 = sp;

        if (ch == 'e' || ch == 'E') {

            putChar(ch);

            scanChar();

            skipIllegalUnderscores();

            if (ch == '+' || ch == '-') {

                putChar(ch);

                scanChar();

            }

            skipIllegalUnderscores();

            if ('0' <= ch && ch <= '9') {

                scanDigits(10);

                return;

            }

            lexError("malformed.fp.lit");

            sp = sp1;

        }

    }

    /** Read fractional part and 'd' or 'f' suffix of floating point number.

     */

    private void scanFractionAndSuffix() {

        this.radix = 10;

        scanFraction();

        if (ch == 'f' || ch == 'F') {

            putChar(ch);

            scanChar();

            token = FLOATLITERAL;

        } else {

            if (ch == 'd' || ch == 'D') {

                putChar(ch);

                scanChar();

            }

            token = DOUBLELITERAL;

        }

    }

    /** Read fractional part and 'd' or 'f' suffix of floating point number.

     */

    private void scanHexFractionAndSuffix(boolean seendigit) {

        this.radix = 16;

        Assert.check(ch == '.');

        putChar(ch);

        scanChar();

        skipIllegalUnderscores();

        if (digit(16) >= 0) {

            seendigit = true;

            scanDigits(16);

        }

        if (!seendigit)

            lexError("invalid.hex.number");

        else

            scanHexExponentAndSuffix();

    }

    private void skipIllegalUnderscores() {

        if (ch == '_') {

            lexError(bp, "illegal.underscore");

            while (ch == '_')

                scanChar();

        }

    }

    /** Read a number.

     *  @param radix  The radix of the number; one of 2, j8, 10, 16.

     */

    private void scanNumber(int radix) {

        this.radix = radix;

        // for octal, allow base-10 digit in case it's a float literal

        int digitRadix = (radix == 8 ? 10 : radix);

        boolean seendigit = false;

        if (digit(digitRadix) >= 0) {

            seendigit = true;

            scanDigits(digitRadix);

        }

        if (radix == 16 && ch == '.') {

            scanHexFractionAndSuffix(seendigit);

        } else if (seendigit && radix == 16 && (ch == 'p' || ch == 'P')) {

            scanHexExponentAndSuffix();

        } else if (digitRadix == 10 && ch == '.') {

            putChar(ch);

            scanChar();

            scanFractionAndSuffix();

        } else if (digitRadix == 10 &&

                   (ch == 'e' || ch == 'E' ||

                    ch == 'f' || ch == 'F' ||

                    ch == 'd' || ch == 'D')) {

            scanFractionAndSuffix();

        } else {

            if (ch == 'l' || ch == 'L') {

                scanChar();

                token = LONGLITERAL;

            } else {

                token = INTLITERAL;

            }

        }

    }

    /** Read an identifier.

     */

    private void scanIdent() {

        boolean isJavaIdentifierPart;

        char high;

        do {

            if (sp == sbuf.length) putChar(ch); else sbuf[sp++] = ch;

            // optimization, was: putChar(ch);

            scanChar();

            switch (ch) {

            case 'A': case 'B': case 'C': case 'D': case 'E':

            case 'F': case 'G': case 'H': case 'I': case 'J':

            case 'K': case 'L': case 'M': case 'N': case 'O':

            case 'P': case 'Q': case 'R': case 'S': case 'T':