#include <qpdf/OffsetInputSource.hh>

#include <limits>

#include <sstream>

#include <stdexcept>

OffsetInputSource::OffsetInputSource(

    std::shared_ptr<InputSource> proxied, qpdf_offset_t global_offset) :

    proxied(proxied),

    global_offset(global_offset)

{

    if (global_offset < 0) {

        throw std::logic_error("OffsetInputSource constructed with negative offset");

    }

    this->max_safe_offset = std::numeric_limits<qpdf_offset_t>::max() - global_offset;

}

qpdf_offset_t

OffsetInputSource::findAndSkipNextEOL()

{

    return this->proxied->findAndSkipNextEOL() - this->global_offset;

}

std::string const&

OffsetInputSource::getName() const

{

    return this->proxied->getName();

}

qpdf_offset_t

OffsetInputSource::tell()

{

    return this->proxied->tell() - this->global_offset;

}

void

OffsetInputSource::seek(qpdf_offset_t offset, int whence)

{

    if (whence == SEEK_SET) {

        if (offset > this->max_safe_offset) {

            std::ostringstream msg;

            msg.imbue(std::locale::classic());

            msg << "seeking to " << offset << " offset by " << global_offset

                << " would cause an overflow of the offset type";

            throw std::range_error(msg.str());

        }

        this->proxied->seek(offset + global_offset, whence);

    } else {

        this->proxied->seek(offset, whence);

    }

    if (tell() < 0) {

        throw std::runtime_error("offset input source: seek before beginning of file");

    }

}

void

OffsetInputSource::rewind()

{

    seek(0, SEEK_SET);

}

size_t

OffsetInputSource::read(char* buffer, size_t length)

{

    size_t result = this->proxied->read(buffer, length);

    this->setLastOffset(this->proxied->getLastOffset() - global_offset);

    return result;

}

void

OffsetInputSource::unreadCh(char ch)

{

    this->proxied->unreadCh(ch);

}