#include <qpdf/Pl_TIFFPredictor.hh>
#include <qpdf/QTC.hh>
#include <qpdf/BitStream.hh>
#include <qpdf/BitWriter.hh>
#include <stdexcept>
#include <vector>
#include <string.h>
#include <limits.h>

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),
    cur_row(0),
    pos(0)
{
    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");
    }
    this->bytes_per_row = bpr & UINT_MAX;
    this->cur_row = new unsigned char[this->bytes_per_row];
    memset(this->cur_row, 0, this->bytes_per_row);
}

Pl_TIFFPredictor::~Pl_TIFFPredictor()
{
    delete [] cur_row;
}

void
Pl_TIFFPredictor::write(unsigned char* data, size_t len)
{
    size_t left = this->bytes_per_row - this->pos;
    size_t offset = 0;
    while (len >= left)
    {
	// finish off current row
	memcpy(this->cur_row + this->pos, data + offset, left);
	offset += left;
	len -= left;

	processRow();

	// Prepare for next row
	memset(this->cur_row, 0, this->bytes_per_row);
	left = this->bytes_per_row;
	this->pos = 0;
    }
    if (len)
    {
	memcpy(this->cur_row + this->pos, data + offset, len);
    }
    this->pos += len;
}

void
Pl_TIFFPredictor::processRow()
{
    QTC::TC("libtests", "Pl_TIFFPredictor processRow",
            (action == a_decode ? 0 : 1));
    BitWriter bw(this->getNext());
    BitStream in(this->cur_row, this->bytes_per_row);
    std::vector<long long> prev;
    for (unsigned int i = 0; i < this->samples_per_pixel; ++i)
    {
        long long sample = in.getBitsSigned(this->bits_per_sample);
        bw.writeBitsSigned(sample, this->bits_per_sample);
        prev.push_back(sample);
    }
    for (unsigned int col = 1; col < this->columns; ++col)
    {
        for (unsigned int i = 0; i < this->samples_per_pixel; ++i)
        {
            long long sample = in.getBitsSigned(this->bits_per_sample);
            long long new_sample = sample;
            if (action == a_encode)
            {
                new_sample -= prev[i];
                prev[i] = sample;
            }
            else
            {
                new_sample += prev[i];
                prev[i] = new_sample;
            }
            bw.writeBitsSigned(new_sample, this->bits_per_sample);
        }
    }
    bw.flush();
}

void
Pl_TIFFPredictor::finish()
{
    if (this->pos)
    {
	// write partial row
	processRow();
    }
    this->pos = 0;
    memset(this->cur_row, 0, this->bytes_per_row);
    getNext()->finish();
}
