#include "GLScaler.hh"

#include "GLContext.hh"
#include "gl_vec.hh"

#include "narrow.hh"
#include "strCat.hh"
#include "xrange.hh"

using namespace gl;

namespace openmsx {

GLScaler::GLScaler(const std::string& progName)
{
	for (auto i : xrange(2)) {
		auto header = tmpStrCat("#define SUPERIMPOSE ", char('0' + i), '\n');
		VertexShader   vShader(header, progName + ".vert");
		FragmentShader fShader(header, progName + ".frag");
		program[i].attach(vShader);
		program[i].attach(fShader);
		program[i].bindAttribLocation(0, "a_position");
		program[i].bindAttribLocation(1, "a_texCoord");
		program[i].link();
		program[i].activate();
		glUniform1i(program[i].getUniformLocation("tex"), 0);
		if (i == 1) {
			glUniform1i(program[i].getUniformLocation("videoTex"), 1);
		}
		unifTexSize[i] = program[i].getUniformLocation("texSize");
		unifMvpMatrix[i] = program[i].getUniformLocation("u_mvpMatrix");
	}
}

void GLScaler::uploadBlock(
	unsigned /*srcStartY*/, unsigned /*srcEndY*/,
	unsigned /*lineWidth*/, FrameSource& /*paintFrame*/)
{
}

void GLScaler::setup(bool superImpose)
{
	int i = superImpose ? 1 : 0;
	program[i].activate();

	glUniformMatrix4fv(unifMvpMatrix[i], 1, GL_FALSE, gl::context->pixelMvp.data());
}

void GLScaler::execute(
	const ColorTexture& src, const ColorTexture* superImpose,
	unsigned srcStartY, unsigned srcEndY, unsigned srcWidth,
	unsigned dstStartY, unsigned dstEndY, unsigned dstWidth,
	unsigned logSrcHeight, bool textureFromZero)
{
	auto srcStartYF = narrow<float>(srcStartY);
	auto srcEndYF = narrow<float>(srcEndY);
	auto dstStartYF = narrow<float>(dstStartY);
	auto dstEndYF = narrow<float>(dstEndY);
	auto dstWidthF = narrow<float>(dstWidth);
	auto srcWidthF = narrow<float>(srcWidth);
	auto srcHeightF = narrow<float>(src.getHeight());
	auto logSrcHeightF = narrow<float>(logSrcHeight);

	if (superImpose) {
		glActiveTexture(GL_TEXTURE1);
		superImpose->bind();
		glActiveTexture(GL_TEXTURE0);
	}
	int i = superImpose ? 1 : 0;
	glUniform3f(unifTexSize[i], srcWidthF, srcHeightF, logSrcHeightF);

	src.bind();
	// Note: hShift is pre-divided by srcWidth, while vShift will be divided
	//       by srcHeight later on.
	// Note: The coordinate is put just past zero, to avoid fract() in the
	//       fragment shader to wrap around on rounding errors.
	static constexpr float BIAS = 0.001f;
	float samplePos = (textureFromZero ? 0.5f : 0.0f) + BIAS;
	float hShift = samplePos / dstWidthF;
	float yRatio = (srcEndYF - srcStartYF) / (dstEndYF - dstStartYF);
	float vShift = samplePos * yRatio;

	// vertex positions
	std::array pos = {
		vec2(     0.0f, dstStartYF),
		vec2(dstWidthF, dstStartYF),
		vec2(dstWidthF, dstEndYF  ),
		vec2(     0.0f, dstEndYF  ),
	};
	// texture coordinates, X-coord shared, Y-coord separate for tex0 and tex1
	float tex0StartY = (srcStartYF + vShift) / srcHeightF;
	float tex0EndY   = (srcEndYF   + vShift) / srcHeightF;
	float tex1StartY = (srcStartYF + vShift) / logSrcHeightF;
	float tex1EndY   = (srcEndYF   + vShift) / logSrcHeightF;
	std::array tex = {
		vec3(0.0f + hShift, tex0StartY, tex1StartY),
		vec3(1.0f + hShift, tex0StartY, tex1StartY),
		vec3(1.0f + hShift, tex0EndY  , tex1EndY  ),
		vec3(0.0f + hShift, tex0EndY  , tex1EndY  ),
	};

	glBindBuffer(GL_ARRAY_BUFFER, vbo[0].get());
	glBufferData(GL_ARRAY_BUFFER, sizeof(pos), pos.data(), GL_STREAM_DRAW);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, nullptr);

	glBindBuffer(GL_ARRAY_BUFFER, vbo[1].get());
	glBufferData(GL_ARRAY_BUFFER, sizeof(tex), tex.data(), GL_STREAM_DRAW);
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

	glEnableVertexAttribArray(0);
	glEnableVertexAttribArray(1);

	glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

	glDisableVertexAttribArray(1);
	glDisableVertexAttribArray(0);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
}

} // namespace openmsx