/********************************************************************************
 *                                                                              *
 * This file is part of IfcOpenShell.                                           *
 *                                                                              *
 * IfcOpenShell is free software: you can redistribute it and/or modify         *
 * it under the terms of the Lesser GNU General Public License as published by  *
 * the Free Software Foundation, either version 3.0 of the License, or          *
 * (at your option) any later version.                                          *
 *                                                                              *
 * IfcOpenShell 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                 *
 * Lesser GNU General Public License for more details.                          *
 *                                                                              *
 * You should have received a copy of the Lesser GNU General Public License     *
 * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
 *                                                                              *
 ********************************************************************************/

/********************************************************************************
 *                                                                              *
 * Please consider this a placeholder for an actual GlobalId generation         *
 * algorithm. A real implementation could for example be based on Boost::uuid   *
 *                                                                              *
 ********************************************************************************/

#include <time.h>
#include <stdlib.h>
#include <algorithm>

#include <boost/uuid/uuid.hpp>
#include <boost/uuid/uuid_generators.hpp>
#include <boost/uuid/uuid_io.hpp>

#include "../ifcparse/IfcWrite.h"
#include "../ifcparse/IfcException.h"

static const char* chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_$";

// Converts an unsigned integer into a base64 string of length l
std::string base64(unsigned v, int l) {
    std::string r;
    r.reserve(l);
    while ( v ) {
        r.push_back(chars[v%64]);
        v /= 64;
    }
    while ( r.size() != l ) r.push_back('0');
    std::reverse(r.begin(),r.end());
    return r;
}

// Converts a base64 string into an unsigned integer
unsigned from_base64(const std::string& s) {
    std::string::size_type zeros = s.find_first_not_of('0');
    unsigned r = 0;
    if ( zeros != std::string::npos )
        for ( std::string::const_iterator i = s.begin()+zeros; i != s.end(); ++ i ) {
            r *= 64;
            const char* c = strchr(chars,*i);
            if ( !c ) throw IfcParse::IfcException("Failed to decode GlobalId");
            r += (c-chars);
        }
    return r;
}

// Compresses the UUID byte array into a base64 representation
std::string compress(unsigned char* v) {
    std::string r;
    r.reserve(22);
    r += base64(v[0],2);
    for ( unsigned i = 1; i < 16; i += 3 ) {
        r += base64((v[i]<<16) + (v[i+1]<<8) + v[i+2],4);
    }
    return r;
}

// Expands the base64 representation into a UUID byte array
void expand(const std::string& s, std::vector<unsigned char>& v) {
    v.push_back(from_base64(s.substr(0,2)));
    for( unsigned i = 0; i < 5; ++i ) {
        unsigned d = from_base64(s.substr(2+4*i,4));
        for ( unsigned j = 0; j < 3; ++ j ) {
            v.push_back((d>>(8*(2-j))) % 256);
        }
    }
}

// A random number generator for the UUID
static boost::uuids::basic_random_generator<boost::mt19937> gen;

IfcWrite::IfcGuidHelper::IfcGuidHelper() {
    boost::uuids::uuid u = gen();
    std::vector<unsigned char> v(u.size());
    std::copy(u.begin(), u.end(), v.begin());
    data = compress(&v[0]);

    std::vector<unsigned char> v2;
    expand(data,v2);
    boost::uuids::uuid u2;
    std::copy(v2.begin(), v2.end(), u2.begin());
}
IfcWrite::IfcGuidHelper::operator std::string() const {
	return data;
}

bool IfcWrite::IfcGuidHelper::seeded = false;