/*
 * Copyright 2011, Blender Foundation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Contributor:
 *		Dalai Felinto
 */

#include "COM_DisplaceOperation.h"
#include "BLI_math.h"
#include "BLI_utildefines.h"

DisplaceOperation::DisplaceOperation() : NodeOperation()
{
	this->addInputSocket(COM_DT_COLOR);
	this->addInputSocket(COM_DT_VECTOR);
	this->addInputSocket(COM_DT_VALUE);
	this->addInputSocket(COM_DT_VALUE);
	this->addOutputSocket(COM_DT_COLOR);
	this->setComplex(true);

	this->m_inputColorProgram = NULL;
	this->m_inputVectorProgram = NULL;
	this->m_inputScaleXProgram = NULL;
	this->m_inputScaleYProgram = NULL;
}

void DisplaceOperation::initExecution()
{
	this->m_inputColorProgram = this->getInputSocketReader(0);
	this->m_inputVectorProgram = this->getInputSocketReader(1);
	this->m_inputScaleXProgram = this->getInputSocketReader(2);
	this->m_inputScaleYProgram = this->getInputSocketReader(3);

	this->m_width_x4 = this->getWidth() * 4;
	this->m_height_x4 = this->getHeight() * 4;
}

void DisplaceOperation::executePixelSampled(float output[4], float x, float y, PixelSampler /*sampler*/)
{
	float xy[2] = { x, y };
	float uv[2], deriv[2][2];

	pixelTransform(xy, uv, deriv);
	if (is_zero_v2(deriv[0]) && is_zero_v2(deriv[1])) {
		this->m_inputColorProgram->readSampled(output, uv[0], uv[1], COM_PS_BILINEAR);
	}
	else {
		/* EWA filtering (without nearest it gets blurry with NO distortion) */
		this->m_inputColorProgram->readFiltered(output, uv[0], uv[1], deriv[0], deriv[1]);
	}
}

bool DisplaceOperation::read_displacement(float x, float y, float xscale, float yscale, const float origin[2], float &r_u, float &r_v)
{
	float width = m_inputVectorProgram->getWidth();
	float height = m_inputVectorProgram->getHeight();
	if (x < 0.0f || x >= width || y < 0.0f || y >= height) {
		r_u = 0.0f;
		r_v = 0.0f;
		return false;
	}
	else {
		float col[4];
		m_inputVectorProgram->readSampled(col, x, y, COM_PS_BILINEAR);
		r_u = origin[0] - col[0] * xscale;
		r_v = origin[1] - col[1] * yscale;
		return true;
	}
}

void DisplaceOperation::pixelTransform(const float xy[2], float r_uv[2], float r_deriv[2][2])
{
	float col[4];
	float uv[2]; /* temporary variables for derivative estimation */
	int num;

	m_inputScaleXProgram->readSampled(col, xy[0], xy[1], COM_PS_NEAREST);
	float xs = col[0];
	m_inputScaleYProgram->readSampled(col, xy[0], xy[1], COM_PS_NEAREST);
	float ys = col[0];
	/* clamp x and y displacement to triple image resolution - 
	 * to prevent hangs from huge values mistakenly plugged in eg. z buffers */
	CLAMP(xs, -m_width_x4, m_width_x4);
	CLAMP(ys, -m_height_x4, m_height_x4);

	/* displaced pixel in uv coords, for image sampling */
	read_displacement(xy[0], xy[1], xs, ys, xy, r_uv[0], r_uv[1]);

	/* Estimate partial derivatives using 1-pixel offsets */
	const float epsilon[2] = { 1.0f, 1.0f };
	
	zero_v2(r_deriv[0]);
	zero_v2(r_deriv[1]);

	num = 0;
	if (read_displacement(xy[0] + epsilon[0], xy[1], xs, ys, xy, uv[0], uv[1])) {
		r_deriv[0][0] += uv[0] - r_uv[0];
		r_deriv[1][0] += uv[1] - r_uv[1];
		++num;
	}
	if (read_displacement(xy[0] - epsilon[0], xy[1], xs, ys, xy, uv[0], uv[1])) {
		r_deriv[0][0] += r_uv[0] - uv[0];
		r_deriv[1][0] += r_uv[1] - uv[1];
		++num;
	}
	if (num > 0) {
		float numinv = 1.0f / (float)num;
		r_deriv[0][0] *= numinv;
		r_deriv[1][0] *= numinv;
	}

	num = 0;
	if (read_displacement(xy[0], xy[1] + epsilon[1], xs, ys, xy, uv[0], uv[1])) {
		r_deriv[0][1] += uv[0] - r_uv[0];
		r_deriv[1][1] += uv[1] - r_uv[1];
		++num;
	}
	if (read_displacement(xy[0], xy[1] - epsilon[1], xs, ys, xy, uv[0], uv[1])) {
		r_deriv[0][1] += r_uv[0] - uv[0];
		r_deriv[1][1] += r_uv[1] - uv[1];
		++num;
	}
	if (num > 0) {
		float numinv = 1.0f / (float)num;
		r_deriv[0][1] *= numinv;
		r_deriv[1][1] *= numinv;
	}
}

void DisplaceOperation::deinitExecution()
{
	this->m_inputColorProgram = NULL;
	this->m_inputVectorProgram = NULL;
	this->m_inputScaleXProgram = NULL;
	this->m_inputScaleYProgram = NULL;
}

bool DisplaceOperation::determineDependingAreaOfInterest(rcti *input, ReadBufferOperation *readOperation, rcti *output)
{
	rcti colorInput;
	rcti vectorInput;
	NodeOperation *operation = NULL;

	/* the vector buffer only needs a 2x2 buffer. The image needs whole buffer */
	/* image */
	operation = getInputOperation(0);
	colorInput.xmax = operation->getWidth();
	colorInput.xmin = 0;
	colorInput.ymax = operation->getHeight();
	colorInput.ymin = 0;
	if (operation->determineDependingAreaOfInterest(&colorInput, readOperation, output)) {
		return true;
	}

	/* vector */
	operation = getInputOperation(1);
	vectorInput.xmax = input->xmax + 1;
	vectorInput.xmin = input->xmin - 1;
	vectorInput.ymax = input->ymax + 1;
	vectorInput.ymin = input->ymin - 1;
	if (operation->determineDependingAreaOfInterest(&vectorInput, readOperation, output)) {
		return true;
	}

	/* scale x */
	operation = getInputOperation(2);
	if (operation->determineDependingAreaOfInterest(input, readOperation, output) ) {
		return true;
	}

	/* scale y */
	operation = getInputOperation(3);
	if (operation->determineDependingAreaOfInterest(input, readOperation, output) ) {
		return true;
	}

	return false;
}

