#include "xmlencodinghandler.h"

bool XmlEncodingHandler::hasDeclaration ( const std::string& utf8 )
{
    size_t len = utf8.size();
    if ( len < 6 ||
            utf8[0] != '<' ||
            utf8[1] != '?' ||
            utf8[2] != 'x' ||
            utf8[3] != 'm' ||
            utf8[4] != 'l' )
        return false;
    return true;
}

std::string XmlEncodingHandler::get (
        const std::string& utf8 )
{
    if ( !hasDeclaration ( utf8 ) )
        return "UTF-8";

    size_t len = utf8.size();
    std::string s;
    for ( size_t i = 0; i < len; ++i )
    {
        s += utf8[i];
        if ( utf8[i] == '>' )
            break;
    }

    if ( s.find ( ">" ) == std::string::npos )
        return "";

    s = CaseHandler::lowerCase ( s );

    if ( s.find ( "encoding=" ) == std::string::npos ||
            s.find ( "utf-8" ) != std::string::npos )
        return "UTF-8";
    else if ( s.find ( "utf-16le" ) != std::string::npos )
        return "UTF-16LE";
    else if ( s.find ( "utf-16be" ) != std::string::npos )
        return "UTF-16BE";
    else if ( s.find ( "utf-16" ) != std::string::npos )
        return "UTF-16";
    else if ( s.find ( "iso-8859-1" ) != std::string::npos )
        return "ISO-8859-1";
    else if ( s.find ( "us-ascii" ) != std::string::npos )
        return "US-ASCII";
    else
        return "";
}

bool XmlEncodingHandler::setUtf8 ( std::string& utf8, bool ignoreCurrentEncoding )
{
    if ( !hasDeclaration ( utf8 ) )
        return true;

    if ( get ( utf8 ).empty() && !ignoreCurrentEncoding )
            return false;

    std::pair<int, int> p = getEncodingValueLimits ( utf8 );
    if ( p.first == -1 || p.second == -1 )
        return true; // attribute missing

    utf8.replace ( p.first, p.second, "UTF-8" );

    return true;
}

bool XmlEncodingHandler::set ( std::string& buffer, std::string& encoding )
{
    std::pair<int, int> p = getEncodingValueLimits ( buffer );
    if ( p.first == -1 || p.second == -1 )
        return false; // attribute missing
    buffer.replace ( p.first, p.second, encoding.c_str() );
    return true;
}

std::pair<int, int>
XmlEncodingHandler::getEncodingValueLimits ( const std::string& utf8 )
{
    if ( !hasDeclaration ( utf8 ) )
        return make_pair ( -1, -1 );
    char *buffer, *start, *end;
    char delimit;
    char anchor[] = "encoding=";
    buffer = ( char * ) utf8.c_str();
    start = strstr ( buffer, anchor );
    if ( !start )
        return make_pair ( -1, -1 );
    start = start + strlen ( anchor );
    if ( *start != '\'' && *start != '\"' )
        return make_pair ( -1, -1 );
    delimit = *start;
    if ( strlen ( start ) < 2 )
        return make_pair ( -1, -1 );
    ++start;
    for ( end = start; *end && *end != delimit; ++end )
    {
        if (
            *end == '?' || *end == '>' || *end == '<' ||
            *end == ' ' || *end == '\t' || *end == '\n' )
        {
            return make_pair ( -1, -1 );
        }
    }
    if ( !*end )
        return make_pair ( -1, -1 );
    return make_pair ( start - buffer, end - start );
}