/**
 * 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 <iostream>
#include <iomanip>
#include <string>
#include <memory>
#include <functional>
#include <sstream>
#include <vector>

#include "x11.h"
#include "opengl.h"
#include "EPoll.h"
#include "Logger.h"
#include "MappedFile.h"
#include "ImageLoader.h"
#include "Texture.h"
#include "Shader.h"
#include "Program.h"
#include "FileMonitor.h"
#include "XAttrs.h"

#include "Shark.h"

class Shark::Impl {
public:

	struct {
		GLint aVertexXYZ = -2;
		GLint aTextureXY = -2;

		GLint fColor = -2;

		GLint uModel = -2;
		GLint uView = -2;
		GLint uProjection = -2;
		GLint uTexture = -2;
	} ProgAttr;

	struct {
		float yaw = -90.f;
		float pitch = 0.f;
		float roll = 0.f;
		float fov = 45.0f;
		glm::vec3 cameraPos = glm::vec3(0.0f, 0.0f, 3.0f);
		glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f);
		glm::vec3 cameraUp = glm::vec3(0.0f, 1.0f, 0.0f);

		void adjustFov(float diff) {
			fov += diff;
			if (fov < 1.0f) fov = 1.0f;
			else if (fov > 120.0f) fov = 120.0f;
			std::cerr << "field of view: " << fov << " °" << std::endl;
		}

		void moveForward(const float cameraSpeed) {
			cameraPos += cameraSpeed * cameraFront;
		}

		void moveBackward(const float cameraSpeed) {
			cameraPos -= cameraSpeed * cameraFront;
		}

		void moveLeft(const float cameraSpeed) {
			cameraPos -= glm::normalize(
					glm::cross(cameraFront, cameraUp)) * cameraSpeed;
		}

		void moveRight(const float cameraSpeed) {
			cameraPos += glm::normalize(
					glm::cross(cameraFront, cameraUp)) * cameraSpeed;
		}

		void moveUp(const float cameraSpeed) {
			cameraPos += cameraSpeed * glm::normalize(cameraUp);
		}

		void moveDown(const float cameraSpeed) {
			cameraPos -= cameraSpeed * glm::normalize(cameraUp);
		}

		void updateCameraFrontAndUp() {
			std::cerr << "--- updateCameraFrontAndUp() --------" << std::endl;
			dump("pitch, yaw, roll", glm::vec3(pitch, yaw, roll));
			dump("cameraPos", cameraPos);
			dump("cameraFront", cameraFront);
			const auto pitchR = glm::radians(pitch); // around X axis
			const auto yawR = glm::radians(yaw); //     around Y axis
			const auto rollR = glm::radians(roll); //   around Z axis

			cameraFront.x = cos(pitchR) * cos(yawR);
			cameraFront.y = sin(pitchR);
			cameraFront.z = cos(pitchR) * sin(yawR);
			cameraFront = glm::normalize(cameraFront);
			dump("cameraFront", cameraFront);
			dump("cameraUp", cameraUp);

			// TODO: review ROLL rotation and default angle
			glm::mat4 rollMatrix = glm::rotate(
					glm::mat4(1.0f), rollR, cameraFront);
			cameraUp = glm::mat3(rollMatrix) * glm::vec3(0., 1., 0.);
			dump("cameraUp", cameraUp);
			std::cerr << "-------------------------------------" << std::endl;
		}

		void limitPitch() {
			if (pitch > +89.0f) pitch = +89.0f;
			if (pitch < -89.0f) pitch = -89.0f;
		}

		void turnLeft(const float angleSpeed) {
			yaw -= angleSpeed;
			updateCameraFrontAndUp();
		}

		void turnRight(const float angleSpeed) {
			yaw += angleSpeed;
			updateCameraFrontAndUp();
		}

		void turnUp(const float angleSpeed) {
			pitch += angleSpeed;
			limitPitch();
			updateCameraFrontAndUp();
		}

		void turnDown(const float angleSpeed) {
			pitch -= angleSpeed;
			limitPitch();
			updateCameraFrontAndUp();
		}

		void rollLeft(const float angleSpeed) {
			roll += angleSpeed;
			updateCameraFrontAndUp();
		}

		void rollRight(const float angleSpeed) {
			roll -= angleSpeed;
			updateCameraFrontAndUp();
		}

	} initialCtx, ctx;

	Display* dpy;
	Window win;
	XVisualInfo* vi;
	GLXContext glc;

	FileMonitor fileMonitor;
	std::vector<WatchedFile> watchedFiles;
	ImageLoader imageLoader;
	std::vector<std::shared_ptr<Shader>> shaders;
	std::shared_ptr<Program> shaderProgram;
	std::vector<std::shared_ptr<Texture>> textures;

	Configuration cfg;
	std::ostream& logOutput = std::cerr;

	Impl(Configuration cfg) : cfg(cfg) {
	}

	void run();
	void clear();
	void runShaders();
	Window getRootWindow(Window defaultValue);
	void log(LogLevel level, std::string message);
	int setNonBlocking(int fd);
	void loadVertices();
	bool reloadTexture(const std::string& fileName);
	void loadTextures();
	std::shared_ptr<Program> loadShaders();
	bool reloadShader(const std::string& fileName);
	void setTitle(const std::string& suffix = "");
	static const std::string getDefaultFile(const std::string& relativePath);

};

Shark::Shark(const Configuration& configuration) :
impl(new Impl(configuration)) {
}

Shark::~Shark() {
	impl->textures.clear();
	impl->shaders.clear();
	impl->shaderProgram = nullptr;
	XFree(impl->vi);
	glXMakeCurrent(impl->dpy, None, NULL);
	glXDestroyContext(impl->dpy, impl->glc);
	XDestroyWindow(impl->dpy, impl->win);
	XCloseDisplay(impl->dpy);
	delete impl;
	// std::cerr << "~Shark()" << std::endl;
}

void Shark::Impl::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() {
	impl->run();
}

void Shark::Impl::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);

	glEnable(GL_DEPTH_TEST);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	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;
				}
process_x11_event:
				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;
				}
				if (XPending(dpy)) goto process_x11_event;
			} 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::Impl::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::Impl::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::Impl::log(LogLevel level, std::string message) {
	::log(logOutput, level, message);
}

int Shark::Impl::setNonBlocking(int fd) {
	int flags = fcntl(fd, F_GETFL, 0);
	fcntl(fd, F_SETFL, flags | O_NONBLOCK);
	return fd;
}

void Shark::Impl::loadVertices() {
	for (int i = 0; i < textures.size(); i++) {
		std::shared_ptr<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
	}
}

const std::string
Shark::Impl::getDefaultFile(const std::string& relativePath) {
	const char* envName = "SHADER_SHARK_DATA_DIR";
	const char* envValue = ::getenv(envName);
	if (envValue) {
		return std::string(envValue) + "/" + relativePath;
	} else {
		throw std::invalid_argument(std::string("Configure $") + envName
				+ " in order to use defaults"
				" or specify textures and shaders as parameters");
	}
}

void Shark::Impl::loadTextures() {
	// Load default texture if there is no configured:
	if (cfg.textures.empty())
		cfg.textures.push_back({getDefaultFile("textures/default.png")});

	for (const Configuration::Texture& tex : cfg.textures) {
		std::shared_ptr<ImageLoader::ImageBuffer>
				img(imageLoader.loadImage(MappedFile(tex.fileName)));
		textures.push_back(std::make_shared<Texture>(
				img->width, img->height, *img, tex.fileName));
		// static const uint32_t watchMask = IN_CLOSE_WRITE | IN_ATTRIB;
		// watchedFiles.push_back(fileMonitor.watch(tex.fileName, watchMask));
		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::Impl::reloadTexture(const std::string& fileName) {
	for (std::shared_ptr<Texture> tex : textures) {
		if (tex->getFileName() == fileName) {
			std::shared_ptr<ImageLoader::ImageBuffer>
					img(imageLoader.loadImage(MappedFile(fileName)));
			tex->update(img->width, img->height, *img);
			loadVertices();
			return true;
		}
	}
	return false;
}

std::shared_ptr<Program> Shark::Impl::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);

		{
			// Load default shaders if there are no configured:
			int vc = 0;
			int fc = 0;
			auto& ss = cfg.shaders;
			for (const auto& s : ss) if (s.type == "vertex") vc++;
			for (const auto& s : ss) if (s.type == "fragment") fc++;
			auto& d = getDefaultFile;
			if (vc == 0) ss.push_back({d("shaders/default.vert"), "vertex"});
			if (fc == 0) ss.push_back({d("shaders/default.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::Impl::reloadShader(const std::string& fileName) {
	for (auto shader : shaders) {
		if (shader->getFileName() == fileName) {
			shader->update(MappedFile(fileName));
			shaderProgram->link();
			return true;
		}
	}
	return false;
}