/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

#include "squid.h"
#include "Debug.h"
#include "http/one/Parser.h"
#include "http/one/Tokenizer.h"
#include "parser/Tokenizer.h"
#include "sbuf/Stream.h"

/// Extracts quoted-string after the caller removes the initial '"'.
/// \param http1p0 whether to prohibit \-escaped characters in quoted strings
/// \throws InsufficientInput when input can be a token _prefix_
/// \returns extracted quoted string (without quotes and with chars unescaped)
static SBuf
parseQuotedStringSuffix(Parser::Tokenizer &tok, const bool http1p0)
{
    /*
     * RFC 1945 - defines qdtext:
     *   inclusive of LWS (which includes CR and LF)
     *   exclusive of 0x80-0xFF
     *   includes 0x5C ('\') as just a regular character
     */
    static const CharacterSet qdtext1p0 = CharacterSet("qdtext (HTTP/1.0)", 0x23, 0x7E) +
                                          CharacterSet("", "!") +
                                          CharacterSet::CR + CharacterSet::LF + CharacterSet::HTAB + CharacterSet::SP;
    /*
     * RFC 7230 - defines qdtext:
     *   exclusive of CR and LF
     *   inclusive of 0x80-0xFF
     *   includes 0x5C ('\') but only when part of quoted-pair
     */
    static const CharacterSet qdtext1p1 = CharacterSet("qdtext (HTTP/1.1)", 0x23, 0x5B) +
                                          CharacterSet("", "!") +
                                          CharacterSet("", 0x5D, 0x7E) +
                                          CharacterSet::HTAB + CharacterSet::SP +
                                          CharacterSet::OBSTEXT;

    // best we can do is a conditional reference since http1p0 value may change per-client
    const CharacterSet &tokenChars = (http1p0 ? qdtext1p0 : qdtext1p1);

    SBuf parsedToken;

    while (!tok.atEnd()) {
        SBuf qdText;
        if (tok.prefix(qdText, tokenChars))
            parsedToken.append(qdText);

        if (!http1p0 && tok.skip('\\')) { // HTTP/1.1 allows quoted-pair, HTTP/1.0 does not
            if (tok.atEnd())
                break;

            /* RFC 7230 section 3.2.6
             *
             * The backslash octet ("\") can be used as a single-octet quoting
             * mechanism within quoted-string and comment constructs.  Recipients
             * that process the value of a quoted-string MUST handle a quoted-pair
             * as if it were replaced by the octet following the backslash.
             *
             *   quoted-pair    = "\" ( HTAB / SP / VCHAR / obs-text )
             */
            static const CharacterSet qPairChars = CharacterSet::HTAB + CharacterSet::SP + CharacterSet::VCHAR + CharacterSet::OBSTEXT;
            SBuf escaped;
            if (!tok.prefix(escaped, qPairChars, 1))
                throw TexcHere("invalid escaped character in quoted-pair");

            parsedToken.append(escaped);
            continue;
        }

        if (tok.skip('"'))
            return parsedToken; // may be empty

        if (tok.atEnd())
            break;

        throw TexcHere(ToSBuf("invalid bytes for set ", tokenChars.name));
    }

    throw Http::One::InsufficientInput();
}

SBuf
Http::One::tokenOrQuotedString(Parser::Tokenizer &tok, const bool http1p0)
{
    if (tok.skip('"'))
        return parseQuotedStringSuffix(tok, http1p0);

    if (tok.atEnd())
        throw InsufficientInput();

    SBuf parsedToken;
    if (!tok.prefix(parsedToken, CharacterSet::TCHAR))
        throw TexcHere("invalid input while expecting an HTTP token");

    if (tok.atEnd())
        throw InsufficientInput();

    // got the complete token
    return parsedToken;
}