/*  -*- c++ -*-
    parser/lexer.cpp

    This file is part of KSieve,
    the KDE internet mail/usenet news message filtering library.
    SPDX-FileCopyrightText: 2002-2003 Marc Mutz <mutz@kde.org>

    SPDX-License-Identifier: GPL-2.0-only
*/

#include "lexer_p.h"
using namespace Qt::Literals::StringLiterals;

#include "error.h"
#include "utf8validator.h"

#include <QString>
#include <QStringList>

#include <memory> // std::unique_ptr

#include <QStringDecoder>
#include <cassert>
#include <cctype> // isdigit

#ifdef STR_DIM
#undef STR_DIM
#endif
#define STR_DIM(x) (sizeof(x) - 1)

namespace KSieve
{
//
//
// Lexer Bridge implementation
//
//

Lexer::Lexer(const char *scursor, const char *send, int options)
    : i(new Impl(scursor, send, options))
{
}

Lexer::~Lexer()
{
    delete i;
    i = nullptr;
}

bool Lexer::ignoreComments() const
{
    assert(i);
    return i->ignoreComments();
}

const Error &Lexer::error() const
{
    assert(i);
    return i->error();
}

bool Lexer::atEnd() const
{
    assert(i);
    return i->atEnd();
}

int Lexer::column() const
{
    assert(i);
    return i->column();
}

int Lexer::line() const
{
    assert(i);
    return i->line();
}

void Lexer::save()
{
    assert(i);
    i->save();
}

void Lexer::restore()
{
    assert(i);
    i->restore();
}

Lexer::Token Lexer::nextToken(QString &result)
{
    assert(i);
    return i->nextToken(result);
}
} // namespace KSieve

// none except a-zA-Z0-9_
static const unsigned char iTextMap[16] = {
    0x00,
    0x00,
    0x00,
    0x00, // CTLs:        none
    0x00,
    0x00,
    0xFF,
    0xC0, // SP ... '?':  0-9
    0x7F,
    0xFF,
    0xFF,
    0xE1, // '@' ... '_': A-Z_
    0x7F,
    0xFF,
    0xFF,
    0xE0 // '`' ... DEL: a-z
};

// SP, HT, CR, LF, {}[]();,#/
// ### exclude '['? Why would one want to write identifier["foo"]?
static const unsigned char delimMap[16] = {
    0x00,
    0x64,
    0x00,
    0x00, // CTLs:        CR, HT, LF
    0x90,
    0xC9,
    0x00,
    0x10, // SP ... '?':  SP, #(),;
    0x00,
    0x00,
    0x00,
    0x16, // '@' ... '_': []
    0x00,
    0x00,
    0x00,
    0x16 // '`' ... DEL: {}
};

// All except iText, delim, "*:
static const unsigned char illegalMap[16] = {0xFF, 0x9B, 0xFF, 0xFF, 0x4F, 0x16, 0x00, 0x0F, 0x80, 0x00, 0x00, 0x0A, 0x80, 0x00, 0x00, 0x0A};

static inline bool isOfSet(const unsigned char map[16], unsigned char ch)
{
    assert(ch < 128);
    return map[ch / 8] & 0x80 >> ch % 8;
}

static inline bool isIText(unsigned char ch)
{
    return ch <= 'z' && isOfSet(iTextMap, ch);
}

static inline bool isDelim(unsigned char ch)
{
    return ch <= '}' && isOfSet(delimMap, ch);
}

static inline bool isIllegal(unsigned char ch)
{
    return ch >= '~' || isOfSet(illegalMap, ch);
}

static inline bool is8Bit(signed char ch)
{
    return ch < 0;
}

static QString removeCRLF(const QString &s)
{
    const bool CRLF = s.endsWith(QLatin1StringView("\r\n"));
    const bool LF = !CRLF && s.endsWith(u'\n');

    const int e = CRLF ? 2 : LF ? 1 : 0; // what to chop off at the end

    return s.left(s.length() - e);
}

static QString removeDotStuff(const QString &s)
{
    return s.startsWith(QLatin1StringView("..")) ? s.mid(1) : s;
}

namespace KSieve
{
//
//
// Lexer Implementation
//
//

Lexer::Impl::Impl(const char *scursor, const char *send, int options)
    : mState(scursor ? scursor : send)
    , mEnd(send ? send : scursor)
    , mIgnoreComments(options & IgnoreComments)
    , mIgnoreLF(options & IgnoreLineFeeds)
{
    if (!scursor || !send) {
        assert(atEnd());
    }
}

Lexer::Token Lexer::Impl::nextToken(QString &result)
{
    assert(!atEnd());
    result.clear();
    // clearErrors();

    const int oldLine = line();

    const bool eatingWSSucceeded = ignoreComments() ? eatCWS() : eatWS();

    if (!ignoreLineFeeds() && oldLine != line()) {
        result.setNum(line() - oldLine); // return number of linefeeds encountered
        return LineFeeds;
    }

    if (!eatingWSSucceeded) {
        return None;
    }

    if (atEnd()) {
        return None;
    }

    switch (*mState.cursor) {
    case '#': // HashComment
        assert(!ignoreComments());
        ++mState.cursor;
        if (!atEnd()) {
            parseHashComment(result, true);
        }
        return HashComment;
    case '/': // BracketComment
        assert(!ignoreComments());
        ++mState.cursor; // eat slash
        if (atEnd() || *mState.cursor != '*') {
            makeError(Error::SlashWithoutAsterisk);
            return BracketComment;
        }
        ++mState.cursor; // eat asterisk
        if (atEnd()) {
            makeError(Error::UnfinishedBracketComment);
            return BracketComment;
        }
        parseBracketComment(result, true);
        return BracketComment;
    case ':': // Tag
        ++mState.cursor;
        if (atEnd()) {
            makeError(Error::UnexpectedCharacter, line(), column() - 1);
            return Tag;
        }
        if (!isIText(*mState.cursor)) {
            makeIllegalCharError(*mState.cursor);
            return Tag;
        }
        parseTag(result);
        return Tag;
    case '"': // QuotedString
        ++mState.cursor;
        parseQuotedString(result);
        return QuotedString;
    case '{':
    case '}':
    case '[':
    case ']':
    case '(':
    case ')':
    case ';':
    case ',': // Special
        result = QLatin1Char(*mState.cursor++);
        return Special;
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9': // Number
        parseNumber(result);
        return Number;
    case 't': // maybe MultiLineString, else Identifier
        if (_strnicmp(mState.cursor, "text:", STR_DIM("text:")) == 0) {
            // MultiLineString
            mState.cursor += STR_DIM("text:");
            parseMultiLine(result);
            // ### FIXME: There can be a hash-comment between "text:"
            // and CRLF! That should be preserved somehow...
            return MultiLineString;
        }
        [[fallthrough]];
    default: // Identifier (first must not be 0-9, and can't (caught by Number above))
        if (!isIText(*mState.cursor)) {
            makeError(Error::IllegalCharacter);
            return None;
        }
        parseIdentifier(result);
        return Identifier;
    }
}

bool Lexer::Impl::eatWS()
{
    while (!atEnd()) {
        switch (*mState.cursor) {
        case '\r':
        case '\n':
            if (!eatCRLF()) {
                return false;
            }
            break;
        case ' ':
        case '\t':
            ++mState.cursor;
            break;
        default:
            return true;
        }
    }

    // at end:
    return true;
}

bool Lexer::Impl::eatCRLF()
{
    assert(!atEnd());
    assert(*mState.cursor == '\n' || *mState.cursor == '\r');

    if (*mState.cursor == '\r') {
        ++mState.cursor;
        if (atEnd() || *mState.cursor != '\n') {
            // CR w/o LF -> error
            makeError(Error::CRWithoutLF);
            return false;
        } else {
            // good CRLF
            newLine();
            return true;
        }
    } else { /* *mState.cursor == '\n' */
        // good, LF only
        newLine();
        return true;
    }
}

bool Lexer::Impl::parseHashComment(QString &result, bool reallySave)
{
    // hash-comment := "#" *CHAR-NOT-CRLF CRLF

    // check that the caller plays by the rules:
    assert(*(mState.cursor - 1) == '#');

    const char *const commentStart = mState.cursor;

    // find next CRLF:
    while (!atEnd()) {
        if (*mState.cursor == '\n' || *mState.cursor == '\r') {
            break;
        }
        ++mState.cursor;
    }
    const char *const commentEnd = mState.cursor - 1;

    // Laurent it creates a problem when we have just "#F" => it doesn't see it as a comment
    //    if (commentEnd == commentStart) {
    //        return true;    // # was last char in script...
    //    }

    if (atEnd() || eatCRLF()) {
        const int commentLength = commentEnd - commentStart + 1;
        if (commentLength > 0) {
            if (!isValidUtf8(commentStart, commentLength)) {
                makeError(Error::InvalidUTF8);
                return false;
            }
            if (reallySave) {
                result += QString::fromUtf8(commentStart, commentLength);
                // In comment < or > breaks parsing => convert them to double quote
                // See src/ksieveui/scriptsparsing/tests/failed/script1.siv
                result.replace(u'<', u'"');
                result.replace(u'>', u'"');
            }
        }
        return true;
    }

    return false;
}

bool Lexer::Impl::parseBracketComment(QString &result, bool reallySave)
{
    // bracket-comment := "/*" *(CHAR-NOT-STAR / ("*" CHAR-NOT-SLASH )) "*/"

    // check that caller plays by the rules:
    assert(*(mState.cursor - 2) == '/');
    assert(*(mState.cursor - 1) == '*');

    const char *const commentStart = mState.cursor;
    const int commentCol = column() - 2;
    const int commentLine = line();

    // find next asterisk:
    do {
        if (!skipTo('*')) {
            if (!error()) {
                makeError(Error::UnfinishedBracketComment, commentLine, commentCol);
            }
            return false;
        }
    } while (!atEnd() && *++mState.cursor != '/');

    if (atEnd()) {
        makeError(Error::UnfinishedBracketComment, commentLine, commentCol);
        return false;
    }

    assert(*mState.cursor == '/');

    const int commentLength = mState.cursor - commentStart - 1;
    if (commentLength > 0) {
        if (!isValidUtf8(commentStart, commentLength)) {
            makeError(Error::InvalidUTF8);
            return false;
        }
        if (reallySave) {
            QString tmp = QString::fromUtf8(commentStart, commentLength);
            result += tmp.remove(u'\r'); // get rid of CR in CRLF pairs
        }
    }

    ++mState.cursor; // eat '/'
    return true;
}

bool Lexer::Impl::parseComment(QString &result, bool reallySave)
{
    // comment := hash-comment / bracket-comment

    switch (*mState.cursor) {
    case '#':
        ++mState.cursor;
        return parseHashComment(result, reallySave);
    case '/':
        if (charsLeft() < 2 || mState.cursor[1] != '*') {
            makeError(Error::IllegalCharacter);
            return false;
        } else {
            mState.cursor += 2; // eat "/*"
            return parseBracketComment(result, reallySave);
        }
    default:
        return false; // don't set an error here - there was no comment
    }
}

bool Lexer::Impl::eatCWS()
{
    // white-space := 1*(SP / CRLF / HTAB / comment )

    while (!atEnd()) {
        switch (*mState.cursor) {
        case ' ':
        case '\t': // SP / HTAB
            ++mState.cursor;
            break;
        case '\n':
        case '\r': // CRLF
            if (!eatCRLF()) {
                return false;
            }
            break;
        case '#':
        case '/': { // comments
            QString dummy;
            if (!parseComment(dummy)) {
                return false;
            }
            break;
        }
        default:
            return true;
        }
    }
    return true;
}

bool Lexer::Impl::parseIdentifier(QString &result)
{
    // identifier := (ALPHA / "_") *(ALPHA DIGIT "_")

    assert(isIText(*mState.cursor));

    const char *const identifierStart = mState.cursor;

    // first char:
    if (isdigit(*mState.cursor)) { // no digits for the first
        makeError(Error::NoLeadingDigits);
        return false;
    }

    // rest of identifier chars ( now digits are allowed ):
    for (++mState.cursor; !atEnd() && isIText(*mState.cursor); ++mState.cursor) { }

    const int identifierLength = mState.cursor - identifierStart;

    // Can use the fast fromLatin1 here, since identifiers are always
    // in the us-ascii subset:
    result += QString::fromLatin1(identifierStart, identifierLength);

    if (atEnd() || isDelim(*mState.cursor)) {
        return true;
    }

    makeIllegalCharError(*mState.cursor);
    return false;
}

bool Lexer::Impl::parseTag(QString &result)
{
    // tag := ":" identifier

    // check that the caller plays by the rules:
    assert(*(mState.cursor - 1) == ':');
    assert(!atEnd());
    assert(isIText(*mState.cursor));

    return parseIdentifier(result);
}

bool Lexer::Impl::parseNumber(QString &result)
{
    // number     := 1*DIGIT [QUANTIFIER]
    // QUANTIFIER := "K" / "M" / "G"

    assert(isdigit(*mState.cursor));

    while (!atEnd() && isdigit(*mState.cursor)) {
        result += QLatin1Char(*mState.cursor++);
    }

    if (atEnd() || isDelim(*mState.cursor)) {
        return true;
    }

    switch (*mState.cursor) {
    case 'G':
    case 'g':
    case 'M':
    case 'm':
    case 'K':
    case 'k':
        result += QLatin1Char(*mState.cursor++);
        break;
    default:
        makeIllegalCharError();
        return false;
    }

    // quantifier found. Check for delimiter:
    if (atEnd() || isDelim(*mState.cursor)) {
        return true;
    }
    makeIllegalCharError();
    return false;
}

bool Lexer::Impl::parseMultiLine(QString &result)
{
    // multi-line          := "text:" *(SP / HTAB) (hash-comment / CRLF)
    //                        *(multi-line-literal / multi-line-dotstuff)
    //                        "." CRLF
    // multi-line-literal  := [CHAR-NOT-DOT *CHAR-NOT-CRLF] CRLF
    // multi-line-dotstuff := "." 1*CHAR-NOT-CRLF CRLF
    //         ;; A line containing only "." ends the multi-line.
    //         ;; Remove a leading '.' if followed by another '.'.

    assert(_strnicmp(mState.cursor - 5, "text:", STR_DIM("text:")) == 0);

    const int mlBeginLine = line();
    const int mlBeginCol = column() - 5;

    while (!atEnd()) {
        switch (*mState.cursor) {
        case ' ':
        case '\t':
            ++mState.cursor;
            break;
        case '#': {
            ++mState.cursor;
            QString dummy;
            if (!parseHashComment(dummy)) {
                return false;
            }
            goto MultiLineStart; // break from switch _and_ while
        }
        case '\n':
        case '\r':
            if (!eatCRLF()) {
                return false;
            }
            goto MultiLineStart; // break from switch _and_ while
        default:
            makeError(Error::NonCWSAfterTextColon);
            return false;
        }
    }

MultiLineStart:
    if (atEnd()) {
        makeError(Error::PrematureEndOfMultiLine, mlBeginLine, mlBeginCol);
        return false;
    }

    // Now, collect the single lines until one with only a single dot is found:
    QStringList lines;
    while (!atEnd()) {
        const char *const oldBeginOfLine = beginOfLine();
        if (!skipToCRLF()) {
            return false;
        }
        const int lineLength = mState.cursor - oldBeginOfLine;
        if (lineLength > 0) {
            if (!isValidUtf8(oldBeginOfLine, lineLength)) {
                makeError(Error::InvalidUTF8);
                return false;
            }
            const QString line = removeCRLF(QString::fromUtf8(oldBeginOfLine, lineLength));
            lines.push_back(removeDotStuff(line));
            if (line == u'.') {
                break;
            }
        } else {
            lines.push_back(QString());
        }
    }

    if (lines.back() != QLatin1StringView(".")) {
        makeError(Error::PrematureEndOfMultiLine, mlBeginLine, mlBeginCol);
        return false;
    }

    assert(!lines.empty());
    lines.erase(--lines.end()); // don't include the lone dot.
    result = lines.join(u'\n');
    return true;
}

bool Lexer::Impl::parseQuotedString(QString &result)
{
    // quoted-string := DQUOTE *CHAR DQUOTE

    // check that caller plays by the rules:
    assert(*(mState.cursor - 1) == '"');

    const int qsBeginCol = column() - 1;
    const int qsBeginLine = line();

    QStringDecoder dec(QStringDecoder::Utf8);
    while (!atEnd()) {
        switch (*mState.cursor) {
        case '"':
            ++mState.cursor;
            return true;
        case '\r':
        case '\n':
            if (!eatCRLF()) {
                return false;
            }
            result += u'\n';
            break;
        case '\\':
            ++mState.cursor;
            if (atEnd()) {
                break;
            }
            [[fallthrough]];
        default:
            if (!is8Bit(*mState.cursor)) {
                result += QLatin1Char(*mState.cursor++);
            } else { // probably UTF-8
                const char *const eightBitBegin = mState.cursor;
                skipTo8BitEnd();
                const int eightBitLen = mState.cursor - eightBitBegin;
                assert(eightBitLen > 0);
                if (isValidUtf8(eightBitBegin, eightBitLen)) {
                    result += dec.decode(QByteArrayView(eightBitBegin, eightBitLen));
                } else {
                    assert(column() >= eightBitLen);
                    makeError(Error::InvalidUTF8, line(), column() - eightBitLen);
                    return false;
                }
            }
        }
    }

    makeError(Error::PrematureEndOfQuotedString, qsBeginLine, qsBeginCol);
    return false;
}

void Lexer::Impl::makeIllegalCharError(char ch)
{
    makeError(isIllegal(ch) ? Error::IllegalCharacter : Error::UnexpectedCharacter);
}
} // namespace KSieve
