/**

 * 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() {

}

void Shark::run() {

	Display* 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};

	XVisualInfo* 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;

	}

	Window win = XCreateWindow(

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

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

			CWColormap | CWEventMask, &swa);

	XMapWindow(dpy, win);

	XStoreName(dpy, win, "ShaderShark");

	setX11PID(dpy, win);

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

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

	glXMakeCurrent(dpy, win, glc);

	// Load GLSL shaders:

	GLuint shaderProgram = loadShaders();

	loadTextures(shaderProgram);

	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);

	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(shaderProgram);

	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++) {

			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);

				bool redraw = false;

				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;

				}

				if (redraw) {

					runShaders(shaderProgram);

					glXSwapBuffers(dpy, win);

				}

			} 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 {

				logOutput

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

						<< epoll[epollEvent].data.fd

						<< std::endl;

			}

		}

	}

	XFree(vi);

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

	glXMakeCurrent(dpy, None, NULL);

	glXDestroyContext(dpy, glc);

	XDestroyWindow(dpy, win);

	XCloseDisplay(dpy);

}

void Shark::runShaders(GLuint program) {

	std::cerr << "GLSL: runShaders(" << program << ")" << std::endl;

	std::cerr << "background color: " << cfg.backgroundColor << std::endl;

	glUseProgram(program);

	checkError(&std::cerr);

	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);

	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);

	glm::mat4 view = glm::lookAt(

			ctx.cameraPos,

			ctx.cameraPos + ctx.cameraFront,

			ctx.cameraUp);

	// 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);

	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:

				GL_FLOAT, GL_FALSE, 5 * sizeof (float),

				(void*) 0);

		// Texture positions:

				GL_FLOAT, GL_FALSE, 5 * sizeof (float),

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

		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(GLuint shaderProgram) {

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

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

		// TODO: review texture loading and binding

		// works even without this - default texture

		// glUniform1i(ProgAttr.jazz, jazz);

		// checkError(&std::cerr);

	}

}

GLuint 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);

		std::vector<std::string> fileNames = {

			"shaders/first.vert",

			"shaders/first.frag",

		};

		std::vector<GLuint> shaders;

		GLuint program = glCreateProgram();

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

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

		for (const std::string& fileName : fileNames) {

			MappedFile file(fileName);

			GLuint shader = glCreateShader(toShaderType(fileName));

			auto fileData = file.getData();

			GLint fileSize = file.getSize();

			glShaderSource(shader, 1, &fileData, &fileSize);

			glCompileShader(shader);

			GLint compileStatus;

			glGetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);

			std::cerr << "GLSL shader compile status: "

					<< compileStatus

					<< (compileStatus == GL_TRUE ? " = OK" : " = ERROR")

					<< std::endl;

			if (compileStatus != GL_TRUE) {

				char error[512];

				glGetShaderInfoLog(shader, sizeof (error), NULL, error);

				std::cerr << "GLSL shader error: " << error;

				throw std::logic_error("GLSL: shader failed to compile");

			}

			glAttachShader(program, shader);

			shaders.push_back(shader);

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

		}

		// 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.

		glLinkProgram(program);

		// listVariables(program);

		GLint linkStatus;

		glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);

		if (linkStatus != GL_TRUE) {

			char error[512];

			glGetProgramInfoLog(program, sizeof (error), NULL, error);

			std::cerr << "GLSL program error: " << error;

			throw std::logic_error("GLSL: program failed to link");

		}

		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");

}