#include <qpdf/Pl_TIFFPredictor.hh>

#include <qpdf/BitStream.hh>

#include <qpdf/BitWriter.hh>

#include <qpdf/QTC.hh>

#include <climits>

#include <stdexcept>

namespace

{

    unsigned long long memory_limit{0};

} // namespace

Pl_TIFFPredictor::Pl_TIFFPredictor(

    char const* identifier,

    Pipeline* next,

    action_e action,

    unsigned int columns,

    unsigned int samples_per_pixel,

    unsigned int bits_per_sample) :

    Pipeline(identifier, next),

    action(action),

    columns(columns),

    samples_per_pixel(samples_per_pixel),

    bits_per_sample(bits_per_sample)

{

    if (!next) {

        throw std::logic_error("Attempt to create Pl_TIFFPredictor with nullptr as next");

    }

    if (samples_per_pixel < 1) {

        throw std::runtime_error("TIFFPredictor created with invalid samples_per_pixel");

    }

    if ((bits_per_sample < 1) || (bits_per_sample > (8 * (sizeof(unsigned long long))))) {

        throw std::runtime_error("TIFFPredictor created with invalid bits_per_sample");

    }

    unsigned long long bpr = ((columns * bits_per_sample * samples_per_pixel) + 7) / 8;

    if ((bpr == 0) || (bpr > (UINT_MAX - 1))) {

        throw std::runtime_error("TIFFPredictor created with invalid columns value");

    }

    if (memory_limit > 0 && bpr > (memory_limit / 2U)) {

        throw std::runtime_error("TIFFPredictor memory limit exceeded");

    }

    this->bytes_per_row = bpr & UINT_MAX;

}

void

Pl_TIFFPredictor::setMemoryLimit(unsigned long long limit)

{

    memory_limit = limit;

}

void

Pl_TIFFPredictor::write(unsigned char const* data, size_t len)

{

    auto end = data + len;

    auto row_end = data + (bytes_per_row - cur_row.size());

    while (row_end <= end) {

        // finish off current row

        cur_row.insert(cur_row.end(), data, row_end);

        data = row_end;

        row_end += bytes_per_row;

        processRow();

        // Prepare for next row

        cur_row.clear();

    }

    cur_row.insert(cur_row.end(), data, end);

}

void

Pl_TIFFPredictor::processRow()

{

    QTC::TC("libtests", "Pl_TIFFPredictor processRow", (action == a_decode ? 0 : 1));

    previous.assign(samples_per_pixel, 0);

    if (bits_per_sample != 8) {

        BitWriter bw(next());

        BitStream in(cur_row.data(), cur_row.size());

        for (unsigned int col = 0; col < this->columns; ++col) {

            for (auto& prev: previous) {

                long long sample = in.getBitsSigned(this->bits_per_sample);

                long long new_sample = sample;

                if (action == a_encode) {

                    new_sample -= prev;

                    prev = sample;

                } else {

                    new_sample += prev;

                    prev = new_sample;

                }

                bw.writeBitsSigned(new_sample, this->bits_per_sample);

            }

        }

        bw.flush();

    } else {

        out.clear();

        auto next_it = cur_row.begin();

        auto cr_end = cur_row.end();

        auto pr_end = previous.end();

        while (next_it != cr_end) {

            for (auto prev = previous.begin(); prev != pr_end && next_it != cr_end;

                 ++prev, ++next_it) {

                long long sample = *next_it;

                long long new_sample = sample;

                if (action == a_encode) {

                    new_sample -= *prev;

                    *prev = sample;

                } else {

                    new_sample += *prev;

                    *prev = new_sample;

                }

                out.push_back(static_cast<unsigned char>(255U & new_sample));

            }

        }

        next()->write(out.data(), out.size());

    }

}

void

Pl_TIFFPredictor::finish()

{

    if (!cur_row.empty()) {

        // write partial row

        cur_row.insert(cur_row.end(), bytes_per_row - cur_row.size(), 0);

        processRow();

    }

    cur_row.clear();

    next()->finish();

}