/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt Creator.
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
****************************************************************************/

#include "qmljslexer_p.h"
#include "qmljsengine_p.h"
#include "qmljsmemorypool_p.h"
#include "qmljskeywords_p.h"

#include <QtCore/qcoreapplication.h>
#include <QtCore/qvarlengtharray.h>
#include <QtCore/qdebug.h>
#include <QtCore/QScopedValueRollback>

QT_BEGIN_NAMESPACE
Q_CORE_EXPORT double qstrtod(const char *s00, char const **se, bool *ok);
QT_END_NAMESPACE

using namespace QmlJS;

static inline int regExpFlagFromChar(const QChar &ch)
{
    switch (ch.unicode()) {
    case 'g': return Lexer::RegExp_Global;
    case 'i': return Lexer::RegExp_IgnoreCase;
    case 'm': return Lexer::RegExp_Multiline;
    case 'u': return Lexer::RegExp_Unicode;
    case 'y': return Lexer::RegExp_Sticky;
    }
    return 0;
}

static inline unsigned char convertHex(ushort c)
{
    if (c >= '0' && c <= '9')
        return (c - '0');
    else if (c >= 'a' && c <= 'f')
        return (c - 'a' + 10);
    else
        return (c - 'A' + 10);
}

static inline QChar convertHex(QChar c1, QChar c2)
{
    return QChar((convertHex(c1.unicode()) << 4) + convertHex(c2.unicode()));
}

Lexer::Lexer(Engine *engine)
    : _engine(engine)
    , _codePtr(nullptr)
    , _endPtr(nullptr)
    , _tokenStartPtr(nullptr)
    , _char(QLatin1Char('\n'))
    , _errorCode(NoError)
    , _currentLineNumber(0)
    , _currentColumnNumber(0)
    , _tokenValue(0)
    , _parenthesesState(IgnoreParentheses)
    , _parenthesesCount(0)
    , _stackToken(-1)
    , _patternFlags(0)
    , _tokenKind(0)
    , _tokenLength(0)
    , _tokenLine(0)
    , _tokenColumn(0)
    , _validTokenText(false)
    , _prohibitAutomaticSemicolon(false)
    , _restrictedKeyword(false)
    , _terminator(false)
    , _followsClosingBrace(false)
    , _delimited(true)
    , _qmlMode(true)
{
    if (engine)
        engine->setLexer(this);
}

bool Lexer::qmlMode() const
{
    return _qmlMode;
}

QString Lexer::code() const
{
    return _code;
}

void Lexer::setCode(const QString &code, int lineno, bool qmlMode)
{
    if (_engine)
        _engine->setCode(code);

    _qmlMode = qmlMode;
    _code = code;
    _tokenText.clear();
    _tokenText.reserve(1024);
    _errorMessage.clear();
    _tokenSpell = QStringRef();
    _rawString = QStringRef();

    _codePtr = code.unicode();
    _endPtr = _codePtr + code.length();
    _tokenStartPtr = _codePtr;

    _char = QLatin1Char('\n');
    _errorCode = NoError;

    _currentLineNumber = lineno;
    _currentColumnNumber = 0;
    _tokenValue = 0;

    // parentheses state
    _parenthesesState = IgnoreParentheses;
    _parenthesesCount = 0;

    _stackToken = -1;

    _patternFlags = 0;
    _tokenLength = 0;
    _tokenLine = lineno;
    _tokenColumn = 0;

    _validTokenText = false;
    _prohibitAutomaticSemicolon = false;
    _restrictedKeyword = false;
    _terminator = false;
    _followsClosingBrace = false;
    _delimited = true;
}

void Lexer::scanChar()
{
    if (_skipLinefeed) {
        Q_ASSERT(*_codePtr == QLatin1Char('\n'));
        ++_codePtr;
        _skipLinefeed = false;
    }
    _char = *_codePtr++;
    ++_currentColumnNumber;

    if (isLineTerminator()) {
        if (_char == QLatin1Char('\r')) {
            if (_codePtr < _endPtr && *_codePtr == QLatin1Char('\n'))
                _skipLinefeed = true;
            _char = QLatin1Char('\n');
        }
        ++_currentLineNumber;
        _currentColumnNumber = 0;
    }
}

namespace {
inline bool isBinop(int tok)
{
    switch (tok) {
    case Lexer::T_AND:
    case Lexer::T_AND_AND:
    case Lexer::T_AND_EQ:
    case Lexer::T_DIVIDE_:
    case Lexer::T_DIVIDE_EQ:
    case Lexer::T_EQ:
    case Lexer::T_EQ_EQ:
    case Lexer::T_EQ_EQ_EQ:
    case Lexer::T_GE:
    case Lexer::T_GT:
    case Lexer::T_GT_GT:
    case Lexer::T_GT_GT_EQ:
    case Lexer::T_GT_GT_GT:
    case Lexer::T_GT_GT_GT_EQ:
    case Lexer::T_LE:
    case Lexer::T_LT:
    case Lexer::T_LT_LT:
    case Lexer::T_LT_LT_EQ:
    case Lexer::T_MINUS:
    case Lexer::T_MINUS_EQ:
    case Lexer::T_NOT_EQ:
    case Lexer::T_NOT_EQ_EQ:
    case Lexer::T_OR:
    case Lexer::T_OR_EQ:
    case Lexer::T_OR_OR:
    case Lexer::T_PLUS:
    case Lexer::T_PLUS_EQ:
    case Lexer::T_REMAINDER:
    case Lexer::T_REMAINDER_EQ:
    case Lexer::T_RETURN:
    case Lexer::T_STAR:
    case Lexer::T_STAR_EQ:
    case Lexer::T_XOR:
    case Lexer::T_XOR_EQ:
        return true;

    default:
        return false;
    }
}

int hexDigit(QChar c)
{
    if (c >= QLatin1Char('0') && c <= QLatin1Char('9'))
        return c.unicode() - '0';
    if (c >= QLatin1Char('a') && c <= QLatin1Char('f'))
        return c.unicode() - 'a' + 10;
    if (c >= QLatin1Char('A') && c <= QLatin1Char('F'))
        return c.unicode() - 'A' + 10;
    return -1;
}

int octalDigit(QChar c)
{
    if (c >= QLatin1Char('0') && c <= QLatin1Char('7'))
        return c.unicode() - '0';
    return -1;
}

} // anonymous namespace

int Lexer::lex()
{
    const int previousTokenKind = _tokenKind;

  again:
    _tokenSpell = QStringRef();
    _rawString = QStringRef();
    _tokenKind = scanToken();
    _tokenLength = _codePtr - _tokenStartPtr - 1;

    _delimited = false;
    _restrictedKeyword = false;
    _followsClosingBrace = (previousTokenKind == T_RBRACE);

    // update the flags
    switch (_tokenKind) {
    case T_LBRACE:
        if (_bracesCount > 0)
            ++_bracesCount;
        Q_FALLTHROUGH();
    case T_SEMICOLON:
        _importState = ImportState::NoQmlImport;
        Q_FALLTHROUGH();
    case T_QUESTION:
    case T_COLON:
    case T_TILDE:
        _delimited = true;
        break;
    case T_AUTOMATIC_SEMICOLON:
    case T_AS:
        _importState = ImportState::NoQmlImport;
        Q_FALLTHROUGH();
    default:
        if (isBinop(_tokenKind))
            _delimited = true;
        break;

    case T_IMPORT:
        if (qmlMode() || (_handlingDirectives && previousTokenKind == T_DOT))
            _importState = ImportState::SawImport;
        if (isBinop(_tokenKind))
            _delimited = true;
        break;

    case T_IF:
    case T_FOR:
    case T_WHILE:
    case T_WITH:
        _parenthesesState = CountParentheses;
        _parenthesesCount = 0;
        break;

    case T_ELSE:
    case T_DO:
        _parenthesesState = BalancedParentheses;
        break;

    case T_CONTINUE:
    case T_BREAK:
    case T_RETURN:
    case T_YIELD:
    case T_THROW:
        _restrictedKeyword = true;
        break;
    case T_RBRACE:
        if (_bracesCount > 0)
            --_bracesCount;
        if (_bracesCount == 0)
            goto again;
    } // switch

    // update the parentheses state
    switch (_parenthesesState) {
    case IgnoreParentheses:
        break;

    case CountParentheses:
        if (_tokenKind == T_RPAREN) {
            --_parenthesesCount;
            if (_parenthesesCount == 0)
                _parenthesesState = BalancedParentheses;
        } else if (_tokenKind == T_LPAREN) {
            ++_parenthesesCount;
        }
        break;

    case BalancedParentheses:
        if (_tokenKind != T_DO && _tokenKind != T_ELSE)
            _parenthesesState = IgnoreParentheses;
        break;
    } // switch

    return _tokenKind;
}

uint Lexer::decodeUnicodeEscapeCharacter(bool *ok)
{
    Q_ASSERT(_char == QLatin1Char('u'));
    scanChar(); // skip u
    if (_codePtr + 4 <= _endPtr && isHexDigit(_char)) {
        uint codePoint = 0;
        for (int i = 0; i < 4; ++i) {
            int digit = hexDigit(_char);
            if (digit < 0)
                goto error;
            codePoint *= 16;
            codePoint += digit;
            scanChar();
        }

        *ok = true;
        return codePoint;
    } else if (_codePtr < _endPtr && _char == QLatin1Char('{')) {
        scanChar(); // skip '{'
        uint codePoint = 0;
        if (!isHexDigit(_char))
            // need at least one hex digit
            goto error;

        while (_codePtr <= _endPtr) {
            int digit = hexDigit(_char);
            if (digit < 0)
                break;
            codePoint *= 16;
            codePoint += digit;
            if (codePoint > 0x10ffff)
                goto error;
            scanChar();
        }

        if (_char != QLatin1Char('}'))
            goto error;

        scanChar(); // skip '}'


        *ok = true;
        return codePoint;
    }

  error:
    _errorCode = IllegalUnicodeEscapeSequence;
    _errorMessage = QCoreApplication::translate("QmlParser", "Illegal unicode escape sequence");

    *ok = false;
    return 0;
}

QChar Lexer::decodeHexEscapeCharacter(bool *ok)
{
    if (isHexDigit(_codePtr[0]) && isHexDigit(_codePtr[1])) {
        scanChar();

        const QChar c1 = _char;
        scanChar();

        const QChar c2 = _char;
        scanChar();

        if (ok)
            *ok = true;

        return convertHex(c1, c2);
    }

    *ok = false;
    return QChar();
}

static inline bool isIdentifierStart(uint ch)
{
    // fast path for ascii
    if ((ch >= 'a' && ch <= 'z') ||
        (ch >= 'A' && ch <= 'Z') ||
        ch == '$' || ch == '_')
        return true;

    switch (QChar::category(ch)) {
    case QChar::Number_Letter:
    case QChar::Letter_Uppercase:
    case QChar::Letter_Lowercase:
    case QChar::Letter_Titlecase:
    case QChar::Letter_Modifier:
    case QChar::Letter_Other:
        return true;
    default:
        break;
    }
    return false;
}

static bool isIdentifierPart(uint ch)
{
    // fast path for ascii
    if ((ch >= 'a' && ch <= 'z') ||
        (ch >= 'A' && ch <= 'Z') ||
        (ch >= '0' && ch <= '9') ||
        ch == '$' || ch == '_' ||
        ch == 0x200c /* ZWNJ */ || ch == 0x200d /* ZWJ */)
        return true;

    switch (QChar::category(ch)) {
    case QChar::Mark_NonSpacing:
    case QChar::Mark_SpacingCombining:

    case QChar::Number_DecimalDigit:
    case QChar::Number_Letter:

    case QChar::Letter_Uppercase:
    case QChar::Letter_Lowercase:
    case QChar::Letter_Titlecase:
    case QChar::Letter_Modifier:
    case QChar::Letter_Other:

    case QChar::Punctuation_Connector:
        return true;
    default:
        break;
    }
    return false;
}

int Lexer::scanToken()
{
    if (_stackToken != -1) {
        int tk = _stackToken;
        _stackToken = -1;
        return tk;
    }

    if (_bracesCount == 0) {
        // we're inside a Template string
        return scanString(TemplateContinuation);
    }


    _terminator = false;

again:
    _validTokenText = false;

    // handle comment can be called after a '/' has been read
    // and returns true if it actually encountered a comment
    auto handleComment = [this](){
        if (_char == QLatin1Char('*')) {
            scanChar();
            while (_codePtr <= _endPtr) {
                if (_char == QLatin1Char('*')) {
                    scanChar();
                    if (_char == QLatin1Char('/')) {
                        scanChar();

                        if (_engine) {
                            _engine->addComment(tokenOffset() + 2, _codePtr - _tokenStartPtr - 1 - 4,
                                                tokenStartLine(), tokenStartColumn() + 2);
                        }

                        return true;
                    }
                } else {
                    scanChar();
                }
            }
        } else if (_char == QLatin1Char('/')) {
            while (_codePtr <= _endPtr && !isLineTerminator()) {
                scanChar();
            }
            if (_engine) {
                _engine->addComment(tokenOffset() + 2, _codePtr - _tokenStartPtr - 1 - 2,
                                    tokenStartLine(), tokenStartColumn() + 2);
            }
            return true;
        }
        return false;
    };


    while (_char.isSpace()) {
        if (isLineTerminator()) {
            if (_restrictedKeyword) {
                // automatic semicolon insertion
                _tokenLine = _currentLineNumber;
                _tokenColumn = _currentColumnNumber;
                _tokenStartPtr = _codePtr - 1;
                return T_SEMICOLON;
            } else {
                _terminator = true;
                syncProhibitAutomaticSemicolon();
            }
        }

        scanChar();
    }

    _tokenStartPtr = _codePtr - 1;
    _tokenLine = _currentLineNumber;
    _tokenColumn = _currentColumnNumber;

    if (_codePtr > _endPtr)
        return EOF_SYMBOL;

    const QChar ch = _char;
    scanChar();

    switch (ch.unicode()) {
    case '~': return T_TILDE;
    case '}': return T_RBRACE;

    case '|':
        if (_char == QLatin1Char('|')) {
            scanChar();
            return T_OR_OR;
        } else if (_char == QLatin1Char('=')) {
            scanChar();
            return T_OR_EQ;
        }
        return T_OR;

    case '{': return T_LBRACE;

    case '^':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_XOR_EQ;
        }
        return T_XOR;

    case ']': return T_RBRACKET;
    case '[': return T_LBRACKET;
    case '?': return T_QUESTION;

    case '>':
        if (_char == QLatin1Char('>')) {
            scanChar();
            if (_char == QLatin1Char('>')) {
                scanChar();
                if (_char == QLatin1Char('=')) {
                    scanChar();
                    return T_GT_GT_GT_EQ;
                }
                return T_GT_GT_GT;
            } else if (_char == QLatin1Char('=')) {
                scanChar();
                return T_GT_GT_EQ;
            }
            return T_GT_GT;
        } else if (_char == QLatin1Char('=')) {
            scanChar();
            return T_GE;
        }
        return T_GT;

    case '=':
        if (_char == QLatin1Char('=')) {
            scanChar();
            if (_char == QLatin1Char('=')) {
                scanChar();
                return T_EQ_EQ_EQ;
            }
            return T_EQ_EQ;
        } else if (_char == QLatin1Char('>')) {
            scanChar();
            return T_ARROW;
        }
        return T_EQ;

    case '<':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_LE;
        } else if (_char == QLatin1Char('<')) {
            scanChar();
            if (_char == QLatin1Char('=')) {
                scanChar();
                return T_LT_LT_EQ;
            }
            return T_LT_LT;
        }
        return T_LT;

    case ';': return T_SEMICOLON;
    case ':': return T_COLON;

    case '/':
        if (handleComment())
            goto again;
        else if (_char == QLatin1Char('=')) {
            scanChar();
            return T_DIVIDE_EQ;
        }
        return T_DIVIDE_;

    case '.':
        if (_importState == ImportState::SawImport)
            return T_DOT;
        if (isDecimalDigit(_char.unicode()))
            return scanNumber(ch);
        if (_char == QLatin1Char('.')) {
            scanChar();
            if (_char == QLatin1Char('.')) {
                scanChar();
                return T_ELLIPSIS;
            } else {
                _errorCode = IllegalCharacter;
                _errorMessage = QCoreApplication::translate("QmlParser", "Unexpected token '.'");
                return T_ERROR;
            }
        }
        return T_DOT;

    case '-':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_MINUS_EQ;
        } else if (_char == QLatin1Char('-')) {
            scanChar();

            if (_terminator && !_delimited && !_prohibitAutomaticSemicolon && _tokenKind != T_LPAREN) {
                _stackToken = T_MINUS_MINUS;
                return T_SEMICOLON;
            }

            return T_MINUS_MINUS;
        }
        return T_MINUS;

    case ',': return T_COMMA;

    case '+':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_PLUS_EQ;
        } else if (_char == QLatin1Char('+')) {
            scanChar();

            if (_terminator && !_delimited && !_prohibitAutomaticSemicolon && _tokenKind != T_LPAREN) {
                _stackToken = T_PLUS_PLUS;
                return T_SEMICOLON;
            }

            return T_PLUS_PLUS;
        }
        return T_PLUS;

    case '*':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_STAR_EQ;
        } else if (_char == QLatin1Char('*')) {
            scanChar();
            if (_char == QLatin1Char('=')) {
                scanChar();
                return T_STAR_STAR_EQ;
            }
            return T_STAR_STAR;
        }
        return T_STAR;

    case ')': return T_RPAREN;
    case '(': return T_LPAREN;

    case '&':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_AND_EQ;
        } else if (_char == QLatin1Char('&')) {
            scanChar();
            return T_AND_AND;
        }
        return T_AND;

    case '%':
        if (_char == QLatin1Char('=')) {
            scanChar();
            return T_REMAINDER_EQ;
        }
        return T_REMAINDER;

    case '!':
        if (_char == QLatin1Char('=')) {
            scanChar();
            if (_char == QLatin1Char('=')) {
                scanChar();
                return T_NOT_EQ_EQ;
            }
            return T_NOT_EQ;
        }
        return T_NOT;

    case '`':
        _outerTemplateBraceCount.push(_bracesCount);
        Q_FALLTHROUGH();
    case '\'':
    case '"':
        return scanString(ScanStringMode(ch.unicode()));
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
        if (_importState == ImportState::SawImport)
            return scanVersionNumber(ch);
        else
            return scanNumber(ch);

    default: {
        uint c = ch.unicode();
        bool identifierWithEscapeChars = false;
        if (QChar::isHighSurrogate(c) && QChar::isLowSurrogate(_char.unicode())) {
            c = QChar::surrogateToUcs4(ushort(c), _char.unicode());
            scanChar();
        } else if (c == '\\' && _char == QLatin1Char('u')) {
            identifierWithEscapeChars = true;
            bool ok = false;
            c = decodeUnicodeEscapeCharacter(&ok);
            if (!ok)
                return T_ERROR;
        }
        if (isIdentifierStart(c)) {
            if (identifierWithEscapeChars) {
                _tokenText.resize(0);
                if (QChar::requiresSurrogates(c)) {
                    _tokenText += QChar(QChar::highSurrogate(c));
                    _tokenText += QChar(QChar::lowSurrogate(c));
                } else {
                    _tokenText += QChar(c);
                }
                _validTokenText = true;
            }
            while (_codePtr <= _endPtr) {
                c = _char.unicode();
                if (QChar::isHighSurrogate(c) && QChar::isLowSurrogate(_codePtr->unicode())) {
                    scanChar();
                    c = QChar::surrogateToUcs4(ushort(c), _char.unicode());
                } else if (_char == QLatin1Char('\\') && _codePtr[0] == QLatin1Char('u')) {
                    if (!identifierWithEscapeChars) {
                        identifierWithEscapeChars = true;
                        _tokenText.resize(0);
                        _tokenText.insert(0, _tokenStartPtr, _codePtr - _tokenStartPtr - 1);
                        _validTokenText = true;
                    }

                    scanChar(); // skip '\\'
                    bool ok = false;
                    c = decodeUnicodeEscapeCharacter(&ok);
                    if (!ok)
                        return T_ERROR;

                    if (!isIdentifierPart(c))
                        break;

                    if (identifierWithEscapeChars) {
                        if (QChar::requiresSurrogates(c)) {
                            _tokenText += QChar(QChar::highSurrogate(c));
                            _tokenText += QChar(QChar::lowSurrogate(c));
                        } else {
                            _tokenText += QChar(c);
                        }
                    }
                    continue;
                }

                if (!isIdentifierPart(c))
                    break;

                if (identifierWithEscapeChars) {
                    if (QChar::requiresSurrogates(c)) {
                        _tokenText += QChar(QChar::highSurrogate(c));
                        _tokenText += QChar(QChar::lowSurrogate(c));
                    } else {
                        _tokenText += QChar(c);
                    }
                }
                scanChar();
            }

            _tokenLength = _codePtr - _tokenStartPtr - 1;

            int kind = T_IDENTIFIER;

            if (!identifierWithEscapeChars)
                kind = classify(_tokenStartPtr, _tokenLength, parseModeFlags());

            if (kind == T_FUNCTION) {
                continue_skipping:
                while (_codePtr < _endPtr && _char.isSpace())
                    scanChar();
                if (_char == QLatin1Char('*')) {
                    _tokenLength = _codePtr - _tokenStartPtr - 1;
                    kind = T_FUNCTION_STAR;
                    scanChar();
                } else if (_char == QLatin1Char('/')) {
                    scanChar();
                    if (handleComment())
                        goto continue_skipping;
                }
            }

            if (_engine) {
                if (kind == T_IDENTIFIER && identifierWithEscapeChars)
                    _tokenSpell = _engine->newStringRef(_tokenText);
                else
                    _tokenSpell = _engine->midRef(_tokenStartPtr - _code.unicode(), _tokenLength);
            }

            return kind;
        }
        }

        break;
    }

    return T_ERROR;
}

int Lexer::scanString(ScanStringMode mode)
{
    QChar quote = (mode == TemplateContinuation) ? QChar(TemplateHead) : QChar(mode);
    bool multilineStringLiteral = false;

    const QChar *startCode = _codePtr - 1;
    // in case we just parsed a \r, we need to reset this flag to get things working
    // correctly in the loop below and afterwards
    _skipLinefeed = false;

    if (_engine) {
        while (_codePtr <= _endPtr) {
            if (isLineTerminator()) {
                if ((quote == QLatin1Char('`') || qmlMode()))
                    break;
                _errorCode = IllegalCharacter;
                _errorMessage = QCoreApplication::translate("QmlParser", "Stray newline in string literal");
                return T_ERROR;
            } else if (_char == QLatin1Char('\\')) {
                break;
            } else if (_char == '$' && quote == QLatin1Char('`')) {
                break;
            } else if (_char == quote) {
                _tokenSpell = _engine->midRef(startCode - _code.unicode(), _codePtr - startCode - 1);
                _rawString = _tokenSpell;
                scanChar();

                if (quote == QLatin1Char('`'))
                    _bracesCount = _outerTemplateBraceCount.pop();

                if (mode == TemplateHead)
                    return T_NO_SUBSTITUTION_TEMPLATE;
                else if (mode == TemplateContinuation)
                    return T_TEMPLATE_TAIL;
                else
                    return T_STRING_LITERAL;
            }
            // don't use scanChar() here, that would transform \r sequences and the midRef() call would create the wrong result
            _char = *_codePtr++;
            ++_currentColumnNumber;
        }
    }

    // rewind by one char, so things gets scanned correctly
    --_codePtr;

    _validTokenText = true;
    _tokenText = QString(startCode, _codePtr - startCode);

    auto setRawString = [&](const QChar *end) {
        QString raw(startCode, end - startCode - 1);
        raw.replace(QLatin1String("\r\n"), QLatin1String("\n"));
        raw.replace(QLatin1Char('\r'), QLatin1Char('\n'));
        _rawString = _engine->newStringRef(raw);
    };

    scanChar();

    while (_codePtr <= _endPtr) {
        if (_char == quote) {
            scanChar();

            if (_engine) {
                _tokenSpell = _engine->newStringRef(_tokenText);
                if (quote == QLatin1Char('`'))
                    setRawString(_codePtr - 1);
            }

            if (quote == QLatin1Char('`'))
                _bracesCount = _outerTemplateBraceCount.pop();

            if (mode == TemplateContinuation)
                return T_TEMPLATE_TAIL;
            else if (mode == TemplateHead)
                return T_NO_SUBSTITUTION_TEMPLATE;

            return multilineStringLiteral ? T_MULTILINE_STRING_LITERAL : T_STRING_LITERAL;
        } else if (quote == QLatin1Char('`') && _char == QLatin1Char('$') && *_codePtr == '{') {
            scanChar();
            scanChar();
            _bracesCount = 1;
            if (_engine) {
                _tokenSpell = _engine->newStringRef(_tokenText);
                setRawString(_codePtr - 2);
            }

            return (mode == TemplateHead ? T_TEMPLATE_HEAD : T_TEMPLATE_MIDDLE);
        } else if (_char == QLatin1Char('\\')) {
            scanChar();
            if (_codePtr > _endPtr) {
                _errorCode = IllegalEscapeSequence;
                _errorMessage = QCoreApplication::translate("QmlParser", "End of file reached at escape sequence");
                return T_ERROR;
            }

            QChar u;

            switch (_char.unicode()) {
            // unicode escape sequence
            case 'u': {
                bool ok = false;
                uint codePoint = decodeUnicodeEscapeCharacter(&ok);
                if (!ok)
                    return T_ERROR;
                if (QChar::requiresSurrogates(codePoint)) {
                    // need to use a surrogate pair
                    _tokenText += QChar(QChar::highSurrogate(codePoint));
                    u = QChar::lowSurrogate(codePoint);
                } else {
                    u = codePoint;
                }
            } break;

            // hex escape sequence
            case 'x': {
                bool ok = false;
                u = decodeHexEscapeCharacter(&ok);
                if (!ok) {
                    _errorCode = IllegalHexadecimalEscapeSequence;
                    _errorMessage = QCoreApplication::translate("QmlParser", "Illegal hexadecimal escape sequence");
                    return T_ERROR;
                }
            } break;

            // single character escape sequence
            case '\\': u = QLatin1Char('\\'); scanChar(); break;
            case '\'': u = QLatin1Char('\''); scanChar(); break;
            case '\"': u = QLatin1Char('\"'); scanChar(); break;
            case 'b':  u = QLatin1Char('\b'); scanChar(); break;
            case 'f':  u = QLatin1Char('\f'); scanChar(); break;
            case 'n':  u = QLatin1Char('\n'); scanChar(); break;
            case 'r':  u = QLatin1Char('\r'); scanChar(); break;
            case 't':  u = QLatin1Char('\t'); scanChar(); break;
            case 'v':  u = QLatin1Char('\v'); scanChar(); break;

            case '0':
                if (! _codePtr->isDigit()) {
                    scanChar();
                    u = QLatin1Char('\0');
                    break;
                }
                Q_FALLTHROUGH();
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                _errorCode = IllegalEscapeSequence;
                _errorMessage = QCoreApplication::translate("QmlParser", "Octal escape sequences are not allowed");
                return T_ERROR;

            case '\r':
            case '\n':
            case 0x2028u:
            case 0x2029u:
                scanChar();
                continue;

            default:
                // non escape character
                u = _char;
                scanChar();
            }

            _tokenText += u;
        } else {
            _tokenText += _char;
            scanChar();
        }
    }

    _errorCode = UnclosedStringLiteral;
    _errorMessage = QCoreApplication::translate("QmlParser", "Unclosed string at end of line");
    return T_ERROR;
}

int Lexer::scanNumber(QChar ch)
{
    if (ch == QLatin1Char('0')) {
        if (_char == QLatin1Char('x') || _char == QLatin1Char('X')) {
            ch = _char; // remember the x or X to use it in the error message below.

            // parse hex integer literal
            scanChar(); // consume 'x'

            if (!isHexDigit(_char)) {
                _errorCode = IllegalNumber;
                _errorMessage = QCoreApplication::translate("QmlParser", "At least one hexadecimal digit is required after '0%1'").arg(ch);
                return T_ERROR;
            }

            double d = 0.;
            while (1) {
                int digit = ::hexDigit(_char);
                if (digit < 0)
                    break;
                d *= 16;
                d += digit;
                scanChar();
            }

            _tokenValue = d;
            return T_NUMERIC_LITERAL;
        } else if (_char == QLatin1Char('o') || _char == QLatin1Char('O')) {
            ch = _char; // remember the o or O to use it in the error message below.

            // parse octal integer literal
            scanChar(); // consume 'o'

            if (!isOctalDigit(_char.unicode())) {
                _errorCode = IllegalNumber;
                _errorMessage = QCoreApplication::translate("QmlParser", "At least one octal digit is required after '0%1'").arg(ch);
                return T_ERROR;
            }

            double d = 0.;
            while (1) {
                int digit = ::octalDigit(_char);
                if (digit < 0)
                    break;
                d *= 8;
                d += digit;
                scanChar();
            }

            _tokenValue = d;
            return T_NUMERIC_LITERAL;
        } else if (_char == QLatin1Char('b') || _char == QLatin1Char('B')) {
            ch = _char; // remember the b or B to use it in the error message below.

            // parse binary integer literal
            scanChar(); // consume 'b'

            if (_char.unicode() != '0' && _char.unicode() != '1') {
                _errorCode = IllegalNumber;
                _errorMessage = QCoreApplication::translate("QmlParser", "At least one binary digit is required after '0%1'").arg(ch);
                return T_ERROR;
            }

            double d = 0.;
            while (1) {
                int digit = 0;
                if (_char.unicode() == '1')
                    digit = 1;
                else if (_char.unicode() != '0')
                    break;
                d *= 2;
                d += digit;
                scanChar();
            }

            _tokenValue = d;
            return T_NUMERIC_LITERAL;
        } else if (_char.isDigit() && !qmlMode()) {
            _errorCode = IllegalCharacter;
            _errorMessage = QCoreApplication::translate("QmlParser", "Decimal numbers can't start with '0'");
            return T_ERROR;
        }
    }

    // decimal integer literal
    QVarLengthArray<char,32> chars;
    chars.append(ch.unicode());

    if (ch != QLatin1Char('.')) {
        while (_char.isDigit()) {
            chars.append(_char.unicode());
            scanChar(); // consume the digit
        }

        if (_char == QLatin1Char('.')) {
            chars.append(_char.unicode());
            scanChar(); // consume `.'
        }
    }

    while (_char.isDigit()) {
        chars.append(_char.unicode());
        scanChar();
    }

    if (_char == QLatin1Char('e') || _char == QLatin1Char('E')) {
        if (_codePtr[0].isDigit() || ((_codePtr[0] == QLatin1Char('+') || _codePtr[0] == QLatin1Char('-')) &&
                                      _codePtr[1].isDigit())) {

            chars.append(_char.unicode());
            scanChar(); // consume `e'

            if (_char == QLatin1Char('+') || _char == QLatin1Char('-')) {
                chars.append(_char.unicode());
                scanChar(); // consume the sign
            }

            while (_char.isDigit()) {
                chars.append(_char.unicode());
                scanChar();
            }
        }
    }

    chars.append('\0');

    const char *begin = chars.constData();
    const char *end = nullptr;
    bool ok = false;

    _tokenValue = qstrtod(begin, &end, &ok);

    if (end - begin != chars.size() - 1) {
        _errorCode = IllegalExponentIndicator;
        _errorMessage = QCoreApplication::translate("QmlParser", "Illegal syntax for exponential number");
        return T_ERROR;
    }

    return T_NUMERIC_LITERAL;
}

int Lexer::scanVersionNumber(QChar ch)
{
    if (ch == QLatin1Char('0')) {
        _tokenValue = 0;
        return T_VERSION_NUMBER;
    }

    int acc = 0;
    acc += ch.digitValue();

    while (_char.isDigit()) {
        acc *= 10;
        acc += _char.digitValue();
        scanChar(); // consume the digit
    }

    _tokenValue = acc;
    return T_VERSION_NUMBER;
}

bool Lexer::scanRegExp(RegExpBodyPrefix prefix)
{
    _tokenText.resize(0);
    _validTokenText = true;
    _patternFlags = 0;

    if (prefix == EqualPrefix)
        _tokenText += QLatin1Char('=');

    while (true) {
        switch (_char.unicode()) {
        case '/':
            scanChar();

            // scan the flags
            _patternFlags = 0;
            while (isIdentLetter(_char)) {
                int flag = regExpFlagFromChar(_char);
                if (flag == 0 || _patternFlags & flag) {
                    _errorMessage = QCoreApplication::translate("QmlParser", "Invalid regular expression flag '%0'")
                             .arg(QChar(_char));
                    return false;
                }
                _patternFlags |= flag;
                scanChar();
            }

            _tokenLength = _codePtr - _tokenStartPtr - 1;
            return true;

        case '\\':
            // regular expression backslash sequence
            _tokenText += _char;
            scanChar();

            if (_codePtr > _endPtr || isLineTerminator()) {
                _errorMessage = QCoreApplication::translate("QmlParser", "Unterminated regular expression backslash sequence");
                return false;
            }

            _tokenText += _char;
            scanChar();
            break;

        case '[':
            // regular expression class
            _tokenText += _char;
            scanChar();

            while (_codePtr <= _endPtr && ! isLineTerminator()) {
                if (_char == QLatin1Char(']'))
                    break;
                else if (_char == QLatin1Char('\\')) {
                    // regular expression backslash sequence
                    _tokenText += _char;
                    scanChar();

                    if (_codePtr > _endPtr || isLineTerminator()) {
                        _errorMessage = QCoreApplication::translate("QmlParser", "Unterminated regular expression backslash sequence");
                        return false;
                    }

                    _tokenText += _char;
                    scanChar();
                } else {
                    _tokenText += _char;
                    scanChar();
                }
            }

            if (_char != QLatin1Char(']')) {
                _errorMessage = QCoreApplication::translate("QmlParser", "Unterminated regular expression class");
                return false;
            }

            _tokenText += _char;
            scanChar(); // skip ]
            break;

        default:
            if (_codePtr > _endPtr || isLineTerminator()) {
                _errorMessage = QCoreApplication::translate("QmlParser", "Unterminated regular expression literal");
                return false;
            } else {
                _tokenText += _char;
                scanChar();
            }
        } // switch
    } // while

    return false;
}

bool Lexer::isLineTerminator() const
{
    const ushort unicode = _char.unicode();
    return unicode == 0x000Au
            || unicode == 0x000Du
            || unicode == 0x2028u
            || unicode == 0x2029u;
}

unsigned Lexer::isLineTerminatorSequence() const
{
    switch (_char.unicode()) {
    case 0x000Au:
    case 0x2028u:
    case 0x2029u:
        return 1;
    case 0x000Du:
        if (_codePtr->unicode() == 0x000Au)
            return 2;
        else
            return 1;
    default:
        return 0;
    }
}

bool Lexer::isIdentLetter(QChar ch)
{
    // ASCII-biased, since all reserved words are ASCII, aand hence the
    // bulk of content to be parsed.
    if ((ch >= QLatin1Char('a') && ch <= QLatin1Char('z'))
            || (ch >= QLatin1Char('A') && ch <= QLatin1Char('Z'))
            || ch == QLatin1Char('$')
            || ch == QLatin1Char('_'))
        return true;
    if (ch.unicode() < 128)
        return false;
    return ch.isLetterOrNumber();
}

bool Lexer::isDecimalDigit(ushort c)
{
    return (c >= '0' && c <= '9');
}

bool Lexer::isHexDigit(QChar c)
{
    return ((c >= QLatin1Char('0') && c <= QLatin1Char('9'))
            || (c >= QLatin1Char('a') && c <= QLatin1Char('f'))
            || (c >= QLatin1Char('A') && c <= QLatin1Char('F')));
}

bool Lexer::isOctalDigit(ushort c)
{
    return (c >= '0' && c <= '7');
}

QString Lexer::tokenText() const
{
    if (_validTokenText)
        return _tokenText;

    if (_tokenKind == T_STRING_LITERAL)
        return QString(_tokenStartPtr + 1, _tokenLength - 2);

    return QString(_tokenStartPtr, _tokenLength);
}

Lexer::Error Lexer::errorCode() const
{
    return _errorCode;
}

QString Lexer::errorMessage() const
{
    return _errorMessage;
}

void Lexer::syncProhibitAutomaticSemicolon()
{
    if (_parenthesesState == BalancedParentheses) {
        // we have seen something like "if (foo)", which means we should
        // never insert an automatic semicolon at this point, since it would
        // then be expanded into an empty statement (ECMA-262 7.9.1)
        _prohibitAutomaticSemicolon = true;
        _parenthesesState = IgnoreParentheses;
    } else {
        _prohibitAutomaticSemicolon = false;
    }
}

bool Lexer::prevTerminator() const
{
    return _terminator;
}

bool Lexer::followsClosingBrace() const
{
    return _followsClosingBrace;
}

bool Lexer::canInsertAutomaticSemicolon(int token) const
{
    return token == T_RBRACE
            || token == EOF_SYMBOL
            || _terminator
            || _followsClosingBrace;
}

static const int uriTokens[] = {
    QmlJSGrammar::T_IDENTIFIER,
    QmlJSGrammar::T_PROPERTY,
    QmlJSGrammar::T_SIGNAL,
    QmlJSGrammar::T_READONLY,
    QmlJSGrammar::T_ON,
    QmlJSGrammar::T_BREAK,
    QmlJSGrammar::T_CASE,
    QmlJSGrammar::T_CATCH,
    QmlJSGrammar::T_CONTINUE,
    QmlJSGrammar::T_DEFAULT,
    QmlJSGrammar::T_DELETE,
    QmlJSGrammar::T_DO,
    QmlJSGrammar::T_ELSE,
    QmlJSGrammar::T_FALSE,
    QmlJSGrammar::T_FINALLY,
    QmlJSGrammar::T_FOR,
    QmlJSGrammar::T_FUNCTION,
    QmlJSGrammar::T_FUNCTION_STAR,
    QmlJSGrammar::T_IF,
    QmlJSGrammar::T_IN,
    QmlJSGrammar::T_OF,
    QmlJSGrammar::T_INSTANCEOF,
    QmlJSGrammar::T_NEW,
    QmlJSGrammar::T_NULL,
    QmlJSGrammar::T_RETURN,
    QmlJSGrammar::T_SWITCH,
    QmlJSGrammar::T_THIS,
    QmlJSGrammar::T_THROW,
    QmlJSGrammar::T_TRUE,
    QmlJSGrammar::T_TRY,
    QmlJSGrammar::T_TYPEOF,
    QmlJSGrammar::T_VAR,
    QmlJSGrammar::T_VOID,
    QmlJSGrammar::T_WHILE,
    QmlJSGrammar::T_CONST,
    QmlJSGrammar::T_DEBUGGER,
    QmlJSGrammar::T_RESERVED_WORD,
    QmlJSGrammar::T_WITH,

    QmlJSGrammar::EOF_SYMBOL
};
static inline bool isUriToken(int token)
{
    const int *current = uriTokens;
    while (*current != QmlJSGrammar::EOF_SYMBOL) {
        if (*current == token)
            return true;
        ++current;
    }
    return false;
}

bool Lexer::scanDirectives(Directives *directives, DiagnosticMessage *error)
{
    auto setError = [error, this](QString message) {
        error->message = std::move(message);
        error->loc.startLine = tokenStartLine();
        error->loc.startColumn = tokenStartColumn();
    };

    QScopedValueRollback<bool> directivesGuard(_handlingDirectives, true);
    Q_ASSERT(!_qmlMode);

    lex(); // fetch the first token

    if (_tokenKind != T_DOT)
        return true;

    do {
        const int lineNumber = tokenStartLine();
        const int column = tokenStartColumn();

        lex(); // skip T_DOT

        if (! (_tokenKind == T_IDENTIFIER || _tokenKind == T_IMPORT))
            return true; // expected a valid QML/JS directive

        const QString directiveName = tokenText();

        if (! (directiveName == QLatin1String("pragma") ||
               directiveName == QLatin1String("import"))) {
            setError(QCoreApplication::translate("QmlParser", "Syntax error"));
            return false; // not a valid directive name
        }

        // it must be a pragma or an import directive.
        if (directiveName == QLatin1String("pragma")) {
            // .pragma library
            if (! (lex() == T_IDENTIFIER && tokenText() == QLatin1String("library"))) {
                setError(QCoreApplication::translate("QmlParser", "Syntax error"));
                return false; // expected `library
            }

            // we found a .pragma library directive
            directives->pragmaLibrary();

        } else {
            Q_ASSERT(directiveName == QLatin1String("import"));
            lex(); // skip .import

            QString pathOrUri;
            QString version;
            bool fileImport = false; // file or uri import

            if (_tokenKind == T_STRING_LITERAL) {
                // .import T_STRING_LITERAL as T_IDENTIFIER

                fileImport = true;
                pathOrUri = tokenText();

                if (!pathOrUri.endsWith(QLatin1String("js"))) {
                    setError(QCoreApplication::translate("QmlParser","Imported file must be a script"));
                    return false;
                }

            } else if (_tokenKind == T_IDENTIFIER) {
                // .import T_IDENTIFIER (. T_IDENTIFIER)* T_VERSION_NUMBER . T_VERSION_NUMBER as T_IDENTIFIER
                while (true) {
                    if (!isUriToken(_tokenKind)) {
                        setError(QCoreApplication::translate("QmlParser","Invalid module URI"));
                        return false;
                    }

                    pathOrUri.append(tokenText());

                    lex();
                    if (tokenStartLine() != lineNumber) {
                        setError(QCoreApplication::translate("QmlParser","Invalid module URI"));
                        return false;
                    }
                    if (_tokenKind != QmlJSGrammar::T_DOT)
                        break;

                    pathOrUri.append(QLatin1Char('.'));

                    lex();
                    if (tokenStartLine() != lineNumber) {
                        setError(QCoreApplication::translate("QmlParser","Invalid module URI"));
                        return false;
                    }
                }

                if (_tokenKind != T_VERSION_NUMBER) {
                    setError(QCoreApplication::translate("QmlParser","Module import requires a version"));
                    return false; // expected the module version number
                }

                version = tokenText();
                lex();
                if (_tokenKind != T_DOT) {
                    setError(QCoreApplication::translate( "QmlParser", "Module import requires a minor version (missing dot)"));
                    return false; // expected the module version number
                }
                version += QLatin1Char('.');

                lex();
                if (_tokenKind != T_VERSION_NUMBER) {
                    setError(QCoreApplication::translate( "QmlParser", "Module import requires a minor version (missing number)"));
                    return false; // expected the module version number
                }
                version += tokenText();
            }

            //
            // recognize the mandatory `as' followed by the module name
            //
            if (! (lex() == T_AS && tokenStartLine() == lineNumber)) {
                if (fileImport)
                    setError(QCoreApplication::translate("QmlParser", "File import requires a qualifier"));
                else
                    setError(QCoreApplication::translate("QmlParser", "Module import requires a qualifier"));
                if (tokenStartLine() != lineNumber) {
                    error->loc.startLine = lineNumber;
                    error->loc.startColumn = column;
                }
                return false; // expected `as'
            }

            if (lex() != T_IDENTIFIER || tokenStartLine() != lineNumber) {
                if (fileImport)
                    setError(QCoreApplication::translate("QmlParser", "File import requires a qualifier"));
                else
                    setError(QCoreApplication::translate("QmlParser", "Module import requires a qualifier"));
                return false; // expected module name
            }

            const QString module = tokenText();
            if (!module.at(0).isUpper()) {
                setError(QCoreApplication::translate("QmlParser","Invalid import qualifier"));
                return false;
            }

            if (fileImport)
                directives->importFile(pathOrUri, module, lineNumber, column);
            else
                directives->importModule(pathOrUri, version, module, lineNumber, column);
        }

        if (tokenStartLine() != lineNumber) {
            setError(QCoreApplication::translate("QmlParser", "Syntax error"));
            return false; // the directives cannot span over multiple lines
        }

        // fetch the first token after the .pragma/.import directive
        lex();
    } while (_tokenKind == T_DOT);

    return true;
}
