/**
 * 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 == 4) ctx.adjustFov(-1.0);
					else if (xev.xbutton.button == 5) ctx.adjustFov(+1.0);
					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;
}