/**

 * ShaderShark

 * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)

 *

 * 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, version 3 of the License.

 *

 * 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, see <http://www.gnu.org/licenses/>.

 */

#include <memory>

#include "Shark.h"

Shark::Shark(const Configuration& configuration) :

cfg(configuration) {

}

Shark::~Shark() {

	// TODO: more SBRM

	shaders.clear();

	shaderProgram = nullptr;

	XFree(vi);

	// for (auto page : pdfTextures) glDeleteTextures(1, &page.texture);

	glXMakeCurrent(dpy, None, NULL);

	glXDestroyContext(dpy, glc);

	XDestroyWindow(dpy, win);

	XCloseDisplay(dpy);

	// std::cerr << "~Shark()" << std::endl;

}

void Shark::setTitle(const std::string& suffix) {

	std::stringstream title;

	title << "ShaderShark";

	if (suffix.size()) title << ": " << suffix.c_str();

	XStoreName(dpy, win, title.str().c_str());

	XFlush(dpy);

}

void Shark::run() {

	dpy = XOpenDisplay(NULL);

	if (dpy == NULL) throw std::logic_error("Unable to connect to X server");

	GLint att[] = {GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, None};

	vi = glXChooseVisual(dpy, 0, att);

	Window root = DefaultRootWindow(dpy);

	Window parent = cfg.rootWindow ? cfg.rootWindow : root;

	XSetWindowAttributes swa;

	swa.colormap = XCreateColormap(dpy, parent, vi->visual, AllocNone);

	swa.event_mask = ExposureMask | KeyPressMask | PointerMotionMask

			| ButtonPressMask

			| StructureNotifyMask;

	bool full = false;

	unsigned int width = 1600;

	unsigned int height = 1200;

	if (parent != root) {

		XWindowAttributes parentAttr;

		XGetWindowAttributes(dpy, parent, &parentAttr);

		width = parentAttr.width;

		height = parentAttr.height;

	}

	win = XCreateWindow(

			dpy, parent, 0, 0, width, height, 0,

			vi->depth, InputOutput, vi->visual,

			CWColormap | CWEventMask, &swa);

	XMapWindow(dpy, win);

	setTitle();

	setX11PID(dpy, win);

	// XSetWindowBackground(dpy, win, 0) vs. glClearColor()

	glc = glXCreateContext(dpy, vi, NULL, GL_TRUE);

	glXMakeCurrent(dpy, win, glc);

	clear();

	glXSwapBuffers(dpy, win);

	// Load GLSL shaders:

	shaderProgram = loadShaders();

	loadTextures();

	loadVertices();

	auto toggleFullscreen = [&]() {

		full = setFullscreen(dpy, win, !full);

	};

	auto resetView = [&]() {

		ctx = initialCtx;

		ctx.updateCameraFrontAndUp();

	};

	// root can reize our window

	// or we can listen to root resize and then resize our window ourselves

	bool listenToRootResizes = true;

	if (listenToRootResizes) XSelectInput(dpy, parent, StructureNotifyMask);

	bool keepRunningX11 = true;

	int x11fd = XConnectionNumber(dpy);

	EPoll epoll;

	epoll.add(x11fd);

	epoll.add(fileMonitor.getFD());

	try {

		epoll.add(setNonBlocking(STDIN_FILENO));

	} catch (const EPoll::Exception& e) {

		logOutput << "Will not monitor events on STDIN: " << e.what() << "\n";

	}

	// rended the 3D scene even before the first event:

	runShaders();

	glXSwapBuffers(dpy, win);

	for (XEvent xev; keepRunningX11;) {

		int epollEventCount = epoll.wait();

		//std::cout << "trace: epoll.wait() = " << epollEventCount << std::endl;

		for (int epollEvent = 0; epollEvent < epollEventCount; epollEvent++) {

			bool redraw = false;

			if (epoll[epollEvent].data.fd == x11fd) {

				if (!XPending(dpy)) {

					// otherwise STDIN events are held until the first X11 event

					logOutput << "trace: no pending X11 event" << std::endl;

					break;

				}

				XWindowAttributes gwa;

				XNextEvent(dpy, &xev);

				if (xev.type == Expose) {

					std::cout << "XEvent: Expose" << std::endl;

					XGetWindowAttributes(dpy, win, &gwa);

					glViewport(0, 0, gwa.width, gwa.height);

					redraw = true;

				} else if (xev.type == KeyPress) {

					DecodedKey key = decodeKeycode(dpy, xev.xkey.keycode);

					std::cout << "XEvent: KeyPress:"

							<< " keycode=" << key.code

							<< " key=" << key.name

							<< std::endl;

					const float cSp = 0.05f; // camera speed

					const float aSp = 5.f; // angle speed

					if (key.matches(XK_q, XK_Escape)) keepRunningX11 = false;

					else if (key.matches(XK_Left, XK_s)) ctx.turnLeft(aSp);

					else if (key.matches(XK_Right, XK_f)) ctx.turnRight(aSp);

					else if (key.matches(XK_Up, XK_e)) ctx.moveForward(cSp);

					else if (key.matches(XK_Down, XK_d)) ctx.moveBackward(cSp);

					else if (key.matches(XK_w)) ctx.rollLeft(aSp);

					else if (key.matches(XK_r)) ctx.rollRight(aSp);

					else if (key.matches(XK_t)) ctx.turnUp(aSp);

					else if (key.matches(XK_g)) ctx.turnDown(aSp);

					else if (key.matches(XK_m)) ctx.moveLeft(cSp);

					else if (key.matches(XK_comma)) ctx.moveRight(cSp);

					else if (key.matches(XK_l)) ctx.moveUp(cSp);

					else if (key.matches(XK_period)) ctx.moveDown(cSp);

					else if (key.matches(XK_j)) ctx.moveLeft(cSp * 5);

					else if (key.matches(XK_k)) ctx.moveRight(cSp * 5);

					else if (key.matches(XK_u)) ctx.moveLeft(cSp * 10);

					else if (key.matches(XK_i)) ctx.moveRight(cSp * 10);

					else if (key.matches(XK_x)) resetView();

					else if (key.matches(XK_F11, XK_y)) toggleFullscreen();

					redraw = true;

				} else if (xev.type == ButtonPress) {

					std::cout << "XEvent: ButtonPress:"

							<< " button=" << xev.xbutton.button

							<< std::endl;

					if (xev.xbutton.button == 1);

					else if (xev.xbutton.button == 8) resetView();

					else if (xev.xbutton.button == 9) keepRunningX11 = false;

					redraw = true;

				} else if (xev.type == MotionNotify) {

					// printCursorInfo(xev.xmotion);

				} else if (xev.type == ConfigureNotify) {

					std::cout << "XEvent: ConfigureNotify:"

							<< " window=" << xev.xconfigure.window

							<< " height=" << xev.xconfigure.height

							<< " width=" << xev.xconfigure.width

							<< std::endl;

					if (listenToRootResizes

							&& xev.xconfigure.window == parent) {

						XResizeWindow(dpy, win,

								xev.xconfigure.width, xev.xconfigure.height);

					}

				} else if (xev.type == UnmapNotify) {

					std::cout << "XEvent: UnmapNotify" << std::endl;

				} else if (xev.type == DestroyNotify) {

					std::cout << "XEvent: DestroyNotify → finish" << std::endl;

					break;

				} else {

					std::cout << "XEvent: type=" << xev.type << std::endl;

				}

			} else if (epoll[epollEvent].data.fd == STDIN_FILENO) {

				int epollFD = epoll[epollEvent].data.fd;

				logOutput << "other event: fd=" << epollFD << " data=";

				for (char ch; read(epollFD, &ch, 1) > 0;) {

					std::stringstream msg;

					msg

							<< std::hex

							<< std::setfill('0')

							<< std::setw(2)

							<< (int) ch;

					logOutput << msg.str();

				}

				logOutput << std::endl;

			} else if (epoll[epollEvent].data.fd == fileMonitor.getFD()) {

				std::cout << "FileMonitor event:" << std::endl;

				for (FileEvent fe; fileMonitor.readEvent(fe);) {

					logOutput << "   "

							<< " file=" << fe.fileName

							<< " mask=" << fe.mask

							<< std::endl;

					try {

						redraw |= reloadTexture(fe.fileName);

						redraw |= reloadShader(fe.fileName);

						setTitle();

					} catch (const std::exception& e) {

						setTitle("[ERROR]");

						logOutput << "error while reloading '"

								<< fe.fileName.c_str()

								<< "': " << e.what() << std::endl;

					}

				}

			} else {

				logOutput

						<< "error: event on an unexpected FD: "

						<< epoll[epollEvent].data.fd

						<< std::endl;

			}

			if (redraw) {

				runShaders();

				glXSwapBuffers(dpy, win);

			}

		}

	}

}

void Shark::clear() {

	glClearColor(

			(cfg.backgroundColor >> 16 & 0xFF) / 256.,

			(cfg.backgroundColor >> 8 & 0xFF) / 256.,

			(cfg.backgroundColor & 0xFF) / 256.,

			1.0);

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

}

void Shark::runShaders() {

	shaderProgram->use();

	checkError(&std::cerr);

	clear();

	GLint viewport[4];

	glGetIntegerv(GL_VIEWPORT, viewport);

	GLfloat width = viewport[2];

	GLfloat height = viewport[3];

	glm::mat4 projection = glm::perspective(

			glm::radians(ctx.fov),

			width / height,

			0.1f, 100.0f);

	glUniformMatrix4fv(ProgAttr.uProjection, 1, GL_FALSE, &projection[0][0]);

	glm::mat4 view = glm::lookAt(

			ctx.cameraPos,

			ctx.cameraPos + ctx.cameraFront,

			ctx.cameraUp);

	glUniformMatrix4fv(ProgAttr.uView, 1, GL_FALSE, &view[0][0]);

	// glBindVertexArray(vao);

	glm::mat4 model = glm::mat4(1.0f); // identity matrix

	// model = glm::translate(model, glm::vec3(0., 0., 0.));

	// float angle = 20.0f;

	// glm::vec3 xxx = glm::vec3(1.0f, 0.3f, 0.5f);

	// model = glm::rotate(model, glm::radians(angle), xxx);

	glUniformMatrix4fv(ProgAttr.uModel, 1, GL_FALSE, &model[0][0]);

	glDrawArrays(GL_TRIANGLES, 0, 2 * 3); // viz loadVertices() kde plníme data

	std::cerr << "GLSL: glDrawArrays()" << std::endl;

}

void Shark::log(LogLevel level, std::string message) {

	::log(logOutput, level, message);

}

int Shark::setNonBlocking(int fd) {

	int flags = fcntl(fd, F_GETFL, 0);

	fcntl(fd, F_SETFL, flags | O_NONBLOCK);

	return fd;

}

void Shark::loadVertices() {

	for (int i = 0; i < textures.size(); i++) {

		const Texture& tex = textures[i];

		GLfloat ratio = tex.getRatio();

		const std::vector<GLfloat> vertices = {

			// Vertex XYZ                      Texture XY

			-0.80f * ratio, +0.80f, +0.0, /**/ 0.0, 0.0,

			+0.80f * ratio, +0.80f, +0.0, /**/ 1.0, 0.0,

			-0.80f * ratio, -0.80f, +0.0, /**/ 0.0, 1.0,

			-0.80f * ratio, -0.80f, +0.0, /**/ 0.0, 1.0,

			+0.80f * ratio, -0.80f, +0.0, /**/ 1.0, 1.0,

			+0.80f * ratio, +0.80f, +0.0, /**/ 1.0, 0.0,

			// viz glDrawArrays(), kde vybereme počátek a počet hodnot

		};

		// Vertex data:

		glVertexAttribPointer(ProgAttr.aVertexXYZ, 3, // vertex items

				GL_FLOAT, GL_FALSE, 5 * sizeof (float),

				(void*) 0);

		glEnableVertexAttribArray(ProgAttr.aVertexXYZ);

		// Texture positions:

		glVertexAttribPointer(ProgAttr.aTextureXY, 2, // texture items

				GL_FLOAT, GL_FALSE, 5 * sizeof (float),

				(void*) (3 * sizeof (float)));

		glEnableVertexAttribArray(ProgAttr.aTextureXY);

		glBufferData(GL_ARRAY_BUFFER,

				vertices.size() * sizeof (vertices[0]),

				vertices.data(),

				GL_STATIC_DRAW);

		// GL_STATIC_DRAW:

		//   The vertex data will be uploaded once

		//   and drawn many times(e.g. the world).

		// GL_DYNAMIC_DRAW:

		//   The vertex data will be created once, changed from

		// 	 time to time, but drawn many times more than that.

		// GL_STREAM_DRAW:

		//   The vertex data will be uploaded once and drawn once.

		// see also glBindBuffer(GL_ARRAY_BUFFER, vbo); where we set current VBO

	}

}

Shark::Texture Shark::loadTexture(const std::string& fileName) {

	Texture tex;

	tex.fileName = fileName;

	MappedFile file(tex.fileName);

	std::shared_ptr<ImageLoader::ImageBuffer> img(imageLoader.loadImage(file));

	tex.width = img->width;

	tex.height = img->height;

	glGenTextures(1, &tex.id);

	glBindTexture(GL_TEXTURE_2D, tex.id);

	auto GLT2D = GL_TEXTURE_2D;

	glTexImage2D(GLT2D, 0, GL_RGBA,

			tex.width, tex.height,

			0, GL_RGBA, GL_UNSIGNED_BYTE,

			img->getData());

	glTexParameteri(GLT2D, GL_TEXTURE_WRAP_S, GL_REPEAT);

	glTexParameteri(GLT2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

	glTexParameteri(GLT2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	glTexParameteri(GLT2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);

	glGenerateMipmap(GLT2D);

	std::cerr << "loadTexture(\"" << fileName.c_str() << "\", "

			<< tex.width << ", " << tex.height << ") = " << tex.id << std::endl;

	checkError(&std::cerr);

	return tex;

}

void Shark::loadTextures() {

	for (const Configuration::Texture& tex : cfg.textures) {

		textures.push_back(loadTexture(tex.fileName));

		watchedFiles.push_back(fileMonitor.watch(tex.fileName));

		// TODO: review texture loading and binding

		// works even without this - default texture

		// glUniform1i(ProgAttr.jazz, jazz);

		// checkError(&std::cerr);

	}

}

bool Shark::reloadTexture(const std::string& fileName) {

	for (const Configuration::Texture& tex : cfg.textures) {

		if (tex.fileName == fileName) {

			logOutput << "TODO: reload texture: " << fileName.c_str() << "\n";

			return true;

		}

	}

	return false;

}

std::shared_ptr<Program> Shark::loadShaders() {

	try {

		// Vertex Array Object (VAO)

		GLuint vao;

		glGenVertexArrays(1, &vao);

		glBindVertexArray(vao);

		// VAO - something like context for bound data/variables

		// We can switch multiple VAOs. VAO can contain multiple VBOs.

		// See also https://stackoverflow.com/questions/11821336/

		// what-are-vertex-array-objects

		// Vertex Buffer Object (VBO):

		GLuint vbo;

		glGenBuffers(1, &vbo);

		glBindBuffer(GL_ARRAY_BUFFER, vbo);

		if (cfg.shaders.empty()) {

			// TODO: configurable absolute path or embedded defaults

			cfg.shaders.push_back({"shaders/first.vert", "vertex"});

			cfg.shaders.push_back({"shaders/first.frag", "fragment"});

		}

		std::shared_ptr<Program> program = std::make_shared<Program>();

		// glBindFragDataLocation(program, 0, "outColor");

		// glBindAttribLocation(program, LOC.input, "vertices");

		for (const Configuration::Shader definition : cfg.shaders) {

			Shader::Type type;

			std::string fileName = definition.fileName;

			if (definition.type == "fragment") type = Shader::Type::FRAGMENT;

			else if (definition.type == "vertex") type = Shader::Type::VERTEX;

			else throw std::invalid_argument("unsupported shader type");

			MappedFile file(fileName);

			std::shared_ptr<Shader> shader = std::make_shared<Shader>(

					type, file, fileName);

			program->attachShader(*shader.get());

			shaders.push_back(shader);

			watchedFiles.push_back(fileMonitor.watch(fileName));

			std::cerr << "GLSL loaded: " << fileName.c_str() << std::endl;

			// We may detach and delete shaders,

			// but our shaders are small, so we keep them for later reloading.

		}

		// GLSL compiler does very efficient / aggressive optimization.

		// Attributes and uniforms that are not used in the shader are deleted.

		// And even if we e.g. read color from a texture and overwrite it,

		// the variable is still deleted and considered „inactive“.

		// Functions glGetAttribLocation() and glGetUniformLocation() return -1.

		program->link();

		ProgAttr.aVertexXYZ = program->getAttribLocation("aVertexXYZ");

		ProgAttr.aTextureXY = program->getAttribLocation("aTextureXY");

		ProgAttr.uModel = program->getUniformLocation("uModel");

		ProgAttr.uView = program->getUniformLocation("uView");

		ProgAttr.uProjection = program->getUniformLocation("uProjection");

		ProgAttr.uTexture = program->getUniformLocation("uTexture");

		ProgAttr.fColor = program->getFragDataLocation("fColor");

		program->bindFragDataLocation("fColor", ProgAttr.fColor);

		// listVariables(program);

		std::cerr << "GLSL shader count: " << shaders.size() << std::endl;

		return program;

	} catch (const std::exception& e) {

		std::cerr << "Error while loading shaders: " << e.what() << std::endl;

	} catch (...) {

		std::cerr << "Error while loading shaders: unknown" << std::endl;

	}

	throw std::logic_error("GLSL: loadShaders() failed");

}

bool Shark::reloadShader(const std::string& fileName) {

	for (auto shader : shaders) {

		if (shader->getFileName() == fileName) {

			shader->update(MappedFile(fileName));

			shaderProgram->link();

			return true;

		}

	}

	return false;

}