#include <GL/freeglut_std.h>
#include <GL/gl.h>
#include <float.h>
#include <stdarg.h>
#include <GL/freeglut.h>
#include <memory.h>
#include <stdio.h>
#include <math.h>
#include <sys/param.h>

#include "gragl.h"

#define SUBWINDOWS 64

static Plot2dGroup * target = NULL;
static struct {
	int last_x;
	int last_y;
	int state;
} mouse;

static int subwindows[SUBWINDOWS];

static void enable_multi_sample() {
	glEnable(GL_MULTISAMPLE);
	glHint(GL_MULTISAMPLE_FILTER_HINT_NV, GL_NICEST);
}

static void draw_function(double x, double y, double size, double step, Function * function) {
	glColor3fv(function->color);
	glLineWidth(function->width);
	glBegin(GL_LINES);

	for (double i = 0; i < size; i += step) {
		Scalar current = function->func(i - x);
		Scalar next = function->func(i + step - x);

		if (current.valid) {
			glVertex2f(i, current.v + y);
			glVertex2f(i + step, next.v + y);
		}
	}

	glEnd();
}

void draw_axis(double x, double y) {
	glColor3fv(COLOR_WHITE);
	glLineWidth(2);
	glBegin(GL_LINES);

	glVertex2f(x, y);
	glVertex2f(x + 1, y);
	glVertex2f(x, y);
	glVertex2f(x, y + 1);

	glVertex2f(x + 1, y);
	glVertex2f(x + 0.9, y + 0.1);
	glVertex2f(x + 1, y + 0);
	glVertex2f(x + 0.9, y - 0.1);

	glVertex2f(x, y + 1);
	glVertex2f(x + 0.1, y + 0.9);
	glVertex2f(x, y + 1);
	glVertex2f(x - 0.1, y + 0.9);

	glEnd();
}

void draw_grid(double x, double y, double size) {
	glColor3f(0.2, 0.2, 0.2);

	glLineWidth(2);
	glBegin(GL_LINES);

	for (double i = 0; i < size; ++i) {
		double xpos = fmod(x + i, size);
		if (xpos < 0) xpos += size;
		glVertex2f(xpos, -size / 2);
		glVertex2f(xpos, size / 2);
	}

	for (double i = 0; i < size; ++i) {
		double ypos = fmod(y + i, size);
		if (ypos < 0) ypos += size;
		glVertex2f(0, ypos - size / 2);
		glVertex2f(size, ypos - size / 2);
	}

	glEnd();

	glColor3f(0.5, 0.5, 0.5);
	glBegin(GL_LINES);
	glVertex2f(0, y);
	glVertex2f(size, y);

	glVertex2f(x, -size / 2);
	glVertex2f(x, size / 2);
	glEnd();

	glColor3f(0.7, 0.7, 0.7);
	glBegin(GL_LINE_LOOP);
	glVertex2f(0, -size / 2);
	glVertex2f(size, -size / 2);
	glVertex2f(size, size / 2);
	glVertex2f(0, size / 2);
	glEnd();
}

static void update() {
	glClearColor(COLOR_BLACK[0], COLOR_BLACK[1], COLOR_BLACK[2], COLOR_BLACK[3]);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	int window = glutGetWindow();
	int plot_id = 0;

	while (subwindows[plot_id] != window) ++plot_id;

	Plot2d * plot = &(target->plots[plot_id]);
	plot->width = glutGet(GLUT_WINDOW_WIDTH);
	plot->height = glutGet(GLUT_WINDOW_HEIGHT);

	double translate = -(plot->rsize / 2);
	double zoom = 2 / (plot->rsize);

	glScalef(zoom, zoom, zoom);
	glTranslatef(translate, 0, 0);

	draw_grid(plot->x, plot->y, plot->rsize);
	draw_axis(plot->x, plot->y);

	for (Function *f = plot->function; f < plot->function + plot->nfuncs; ++f) {
		draw_function(plot->x, plot->y, plot->rsize, plot->step, f);
	}

	glTranslatef(-translate, 0, 0);
	glScalef(1/zoom, 1/zoom, 1/zoom);

	glutSwapBuffers();
}

static void parent_update() {
	glClearColor(COLOR_DARKER[0], COLOR_DARKER[1], COLOR_DARKER[2], COLOR_DARKER[3]);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glutSwapBuffers();

	int width = glutGet(GLUT_WINDOW_WIDTH);
	int height = glutGet(GLUT_WINDOW_HEIGHT);
	int min = width > height ? height : width;

	unsigned n_plots = ((unsigned)sqrt(target->n));

	int plot_dim = min / (int)n_plots - (int)target->padding / 4;
	int padding_x = (width - plot_dim * n_plots) / 2;
	int padding_y = (height - plot_dim * n_plots) / 2;

	plot_dim = plot < 0 ? 1 : plot_dim;

	for (unsigned i = 0; i < SUBWINDOWS && subwindows[i] > 0; ++i) {
		glutSetWindow(subwindows[i]);
		glutReshapeWindow(
				plot_dim - target->padding / 2,
				plot_dim - target->padding / 2
		);
		glutPositionWindow(
				padding_x + (i % n_plots) * plot_dim + target->padding / 2,
				padding_y + (i / n_plots) * plot_dim + target->padding / 2
		);
	}
}


static void mouse_wheel(int wheel, int direction, int x, int y) {
	int window = glutGetWindow();
	int plot_id = 0;
	while (subwindows[plot_id] != window) ++plot_id;
	Plot2d *plot = target->plots + plot_id;


	plot->rsize += direction * MAX(log(plot->rsize), 0.00001);

	glutPostRedisplay();
}


static void mouse_move(int x, int y) {
	int window = glutGetWindow();
	int plot_id = 0;
	while (subwindows[plot_id] != window) ++plot_id;
	Plot2d *plot = target->plots + plot_id;

	double delta_x = x - mouse.last_x;
	double delta_y = y - mouse.last_y;

	plot->x += delta_x / plot->width * plot->rsize;
	plot->y -= delta_y / plot->width * plot->rsize;

	mouse.last_x = x;
	mouse.last_y = y;

	glutPostRedisplay();
}


static void mouse_button(int button, int state, int x, int y) {
	mouse.state = state;
	mouse.last_x = x;
	mouse.last_y = y;

	if (state) {
		glutSetCursor(GLUT_CURSOR_INHERIT);
	} else {
		glutSetCursor(GLUT_CURSOR_INFO);
	}
}


static void resize(int width, int height) {
	glutReshapeWindow(MAX(width, 10), MAX(width, 10));
}


void plot(Plot2dGroup * group) {
	target = group;

	char * arg[1] = { "" };
	int argc = 1;

	glutInit(&argc, arg);
	glutInitWindowSize(500, 500);
	glutSetOption(GLUT_MULTISAMPLE, 8);
	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH | GLUT_MULTISAMPLE);
	int parent = glutCreateWindow("GRAGL");

	for (int i = 0; i < group->n; ++i) {
		int id = glutCreateSubWindow(parent, 1, 1, 1, 1);
		subwindows[i] = id;
		glutSetWindow(id);
		glutDisplayFunc(update);
		glutMouseFunc(mouse_button);
		glutMotionFunc(mouse_move);
		glutMouseWheelFunc(mouse_wheel);
	}

	glutSetWindow(parent);
	glutDisplayFunc(parent_update);
	glutReshapeFunc(resize);

	enable_multi_sample();

	glutMainLoop();
}

Plot2dGroup * create_plot2d_group(int num_args, ...) {
	Plot2dGroup * group = (Plot2dGroup*)malloc(sizeof(Plot2dGroup));
	group->plots = (Plot2d*)malloc(sizeof(Plot2d) * num_args);

	group->n = num_args;
	group->padding = 20;

	va_list ap;
	va_start(ap, num_args);

	for (int i = 0; i < num_args; ++i) {
		group->plots[i] = va_arg(ap, Plot2d);
	}
	va_end(ap);

	return group;
}

void free_plot2d_group(Plot2dGroup * group) {
	free(group->plots);
	free(group);
}