//
//  TextureTarget.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 07/02/2016.
//  Copyright 2016 Thomas Harte. All rights reserved.
//

#include "TextureTarget.hpp"

#include <algorithm>
#include <stdexcept>

using namespace Outputs::Display::OpenGL;

TextureTarget::TextureTarget(
	const API api,
	const GLsizei width,
	const GLsizei height,
	const GLenum texture_unit,
	const GLint mag_filter,
	const bool has_stencil_buffer
) :
	api_(api),
	width_(width),
	height_(height),
	texture_unit_(texture_unit)
{
	// Generate and bind a frame buffer.
	test_gl([&]{ glGenFramebuffers(1, &framebuffer_); });
	test_gl([&]{ glBindFramebuffer(GL_FRAMEBUFFER, framebuffer_); });

	// Generate a texture and bind it to the nominated texture unit.
	test_gl([&]{ glGenTextures(1, &texture_); });
	bind_texture();

	// Set dimensions and set the user-supplied magnification filter.
	test_gl([&]{ 
		glTexImage2D(
			GL_TEXTURE_2D,
			0,
			GL_RGBA,
			GLsizei(width_),
			GLsizei(height_),
			0,
			GL_RGBA,
			GL_UNSIGNED_BYTE,
			nullptr
		);
	});
	test_gl([&]{ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, mag_filter); });
	test_gl([&]{ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); });

	// Set the texture as colour attachment 0 on the frame buffer.
	test_gl([&]{ glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture_, 0); });

	// Also add a stencil buffer if requested.
	if(has_stencil_buffer) {
		test_gl([&]{ glGenRenderbuffers(1, &renderbuffer_); });
		test_gl([&]{ glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer_); });
		test_gl([&]{ glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, width_, height_); });
		test_gl([&]{
			glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, renderbuffer_);
		});
	}

	// Check for successful construction.
	const auto framebuffer_status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
	if(framebuffer_status != GL_FRAMEBUFFER_COMPLETE) {
		switch(framebuffer_status) {
			case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
				throw std::runtime_error("GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT");
			case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER:
				throw std::runtime_error("GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER");
			case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER:
				throw std::runtime_error("GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER");
			case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
				throw std::runtime_error("GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT");
			case GL_FRAMEBUFFER_UNSUPPORTED:
				throw std::runtime_error("GL_FRAMEBUFFER_UNSUPPORTED");
			default:
				throw std::runtime_error("Framebuffer status incomplete: " + std::to_string(framebuffer_status));

			case 0:
				test_gl_error();
			break;
		}
	}

	// Clear the framebuffer.
	test_gl([&]{ glClear(GL_COLOR_BUFFER_BIT); });
}

TextureTarget::~TextureTarget() {
	glDeleteFramebuffers(1, &framebuffer_);
	glDeleteTextures(1, &texture_);
	glDeleteRenderbuffers(1, &renderbuffer_);
	glDeleteVertexArrays(1, &drawing_vertex_array_);
	glDeleteBuffers(1, &drawing_array_buffer_);
}

TextureTarget::TextureTarget(TextureTarget &&rhs) {
	*this = std::move(rhs);
}

TextureTarget &TextureTarget::operator =(TextureTarget &&rhs) {
	api_ = rhs.api_;
	std::swap(framebuffer_, rhs.framebuffer_);
	std::swap(texture_, rhs.texture_);
	std::swap(renderbuffer_, rhs.renderbuffer_);
	std::swap(width_, rhs.width_);
	std::swap(height_, rhs.height_);
	std::swap(texture_unit_, rhs.texture_unit_);

	// Other fields in the TextureTarget relate to the `draw` functionality below, which I intend to
	// eliminate. Therefore just let them be.

	return *this;
}

void TextureTarget::bind_framebuffer() {
	test_gl([&]{ glBindFramebuffer(GL_FRAMEBUFFER, framebuffer_); });
	test_gl([&]{ glViewport(0, 0, width_, height_); });
}

void TextureTarget::bind_texture() const {
	test_gl([&]{ glActiveTexture(texture_unit_); });
	test_gl([&]{ glBindTexture(GL_TEXTURE_2D, texture_); });
}

// TODO: eliminate below, plus relevant local storage.
void TextureTarget::draw(const float aspect_ratio, const float colour_threshold) const {
	if(!pixel_shader_) {
		const char *const vertex_shader =
			R"glsl(
				in vec2 texCoord;
				in vec2 position;

				out vec2 texCoordVarying;

				void main(void) {
					texCoordVarying = texCoord;
					gl_Position = vec4(position, 0.0, 1.0);
				}
			)glsl";
		const char *const fragment_shader =
			R"glsl(
				in vec2 texCoordVarying;

				uniform sampler2D texID;
				uniform float threshold;

				out vec4 fragColour;

				void main(void) {
					fragColour = clamp(texture(texID, texCoordVarying), threshold, 1.0);
				}
			)glsl";
		pixel_shader_ = std::make_unique<Shader>(api_, vertex_shader, fragment_shader);
		pixel_shader_->bind();

		test_gl([&]{ glGenVertexArrays(1, &drawing_vertex_array_); });
		test_gl([&]{ glGenBuffers(1, &drawing_array_buffer_); });

		test_gl([&]{ glBindVertexArray(drawing_vertex_array_); });
		test_gl([&]{ glBindBuffer(GL_ARRAY_BUFFER, drawing_array_buffer_); });

		const GLint position_attribute	= pixel_shader_->get_attrib_location("position");
		const GLint tex_coord_attribute	= pixel_shader_->get_attrib_location("texCoord");

		test_gl([&]{ glEnableVertexAttribArray(GLuint(position_attribute)); });
		test_gl([&]{ glEnableVertexAttribArray(GLuint(tex_coord_attribute)); });

		const GLsizei vertex_stride = 4 * sizeof(GLfloat);
		test_gl([&]{ 
			glVertexAttribPointer(
				GLuint(position_attribute),
				2,
				GL_FLOAT,
				GL_FALSE,
				vertex_stride,
				(void *)0
			);
		});
		test_gl([&]{
			glVertexAttribPointer(
				GLuint(tex_coord_attribute),
				2,
				GL_FLOAT,
				GL_FALSE,
				vertex_stride,
				(void *)(2 * sizeof(GLfloat))
			);
		});

		const GLint texIDUniform = pixel_shader_->get_uniform_location("texID");
		test_gl([&]{ glUniform1i(texIDUniform, GLint(texture_unit_ - GL_TEXTURE0));  });

		threshold_uniform_ = pixel_shader_->get_uniform_location("threshold");
	}

	if(set_aspect_ratio_ != aspect_ratio) {
		set_aspect_ratio_ = aspect_ratio;
		float buffer[4*4];

		// establish texture coordinates
		buffer[2] = 0.0f;
		buffer[3] = 0.0f;
		buffer[6] = 0.0f;
		buffer[7] = 1.0f;//float(height_) / float(expanded_height_);
		buffer[10] = 1.0f;//float(width_) / float(expanded_width_);
		buffer[11] = 0.0f;
		buffer[14] = buffer[10];
		buffer[15] = buffer[7];

		// determine positions; rule is to keep the same height and centre
		const float internal_aspect_ratio = float(width_) / float(height_);
		const float aspect_ratio_ratio = internal_aspect_ratio / aspect_ratio;

		buffer[0] = -aspect_ratio_ratio;	buffer[1] = -1.0f;
		buffer[4] = -aspect_ratio_ratio;	buffer[5] = 1.0f;
		buffer[8] = aspect_ratio_ratio;		buffer[9] = -1.0f;
		buffer[12] = aspect_ratio_ratio;	buffer[13] = 1.0f;

		// upload buffer
		test_gl([&]{ glBindBuffer(GL_ARRAY_BUFFER, drawing_array_buffer_); });
		test_gl([&]{ glBufferData(GL_ARRAY_BUFFER, sizeof(buffer), buffer, GL_STATIC_DRAW); });
	}

	pixel_shader_->bind();
	test_gl([&]{ glUniform1f(threshold_uniform_, colour_threshold); });

	test_gl([&]{ glBindVertexArray(drawing_vertex_array_); });
	test_gl([&]{ glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); });
}