path: root/src/main/engine/engine.c

/*-
 * Copyright (C) 2025  Alessandro Iezzi <aiezzi AT alessandroiezzi PERIOD it>
 *
 * This file is part of Tris Game.
 *
 * Tris Game 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Tris Game 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 Tris Game.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <GL/gl.h>
#include <math.h>
#include <log.h>
#include "engine.h"
#include "ui/ui.h"
#include "../util/list.h"
#include "shape/circle.h"

#ifdef X11
#include <X11/Xlib.h>
#endif

#define RANGE_GL 2.0f

static Log *_log = NULL;

static void
init_log(void)
{
	if (_log != NULL) return;
	_log = log_create("Engine");
}

typedef struct Line {
	float x1, y1, x2, y2;
} Line;

static Engine *engine;

/* FPS */
static time_t start;
static int frames;
static time_t end;

void (*dispatch_ui_event)(int);

typedef struct MouseButtonEvent {
	void (*on_mouse_button_pressed)(float x, float y, void *data);
	void *data;
} MouseButtonEvent;

MouseButtonEvent *mouse_button_event;

Engine *
engine_new(int w, int h)
{
	init_log();

	engine = malloc(sizeof(Engine));
	if (engine == NULL) {
		log_error(_log, "Error allocating memory for engine");
		exit(EXIT_FAILURE);
	}
	engine->lines = list_create();
	engine->ui = ui_new(w, h);

	engine_set_rendering_background(engine, 0.0f, 0.0f, 0.2f, 1.0f);

	return engine;
}

void
engine_set_window_title(Engine *engine, const char *title)
{
	ui_set_title(engine->ui, title);
}

static Line *
engine_new_line(float x1, float y1, float x2, float y2)
{
	Line *line = malloc(sizeof(Line));
	line->x1 = x1;
	line->y1 = y1;
	line->x2 = x2;
	line->y2 = y2;

	return line;
}

void
engine_draw_line(float x1, float y1, float x2, float y2)
{
	if (engine->lines != NULL) {
		Line *line = engine_new_line(x1, y1, x2, y2);
		list_add(engine->lines, line);
	}
}

static void
engine_calculate_fps()
{
	frames ++;

	end = time(NULL);
	if (end - start >= 1.0) {
#ifdef FPS
		printf("FPS: %d\n", frames);
#endif
		frames = 0;
		start = time(NULL);
	}
}

static void
render_line(Line *line)
{
	glVertex2f(line->x1, line->y1);
	glVertex2f(line->x2, line->y2);
}

static void
draw_lines()
{
	if (engine->lines == NULL || engine->lines->size <= 0) return;

	glLineWidth(5.0f);
	glBegin(GL_LINES);
	glColor3f(1.0f, 1.0f, 0.0f); /* Yellow */

	list_node_t *current = engine->lines->head;
	do {
		render_line(current->data);
		current = current->next;
	} while (current != NULL);

	glEnd();
}

static void
draw_frames(void *data)
{
	if (data == NULL) return;

	Engine *engine = data;
	Color *bk = engine->rendering_background;

	glClearColor(bk->r, bk->g, bk->b, bk->a);
	glClear(GL_COLOR_BUFFER_BIT);
	glEnable(GL_LINE_SMOOTH);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	draw_lines();
	engine->draw_frame_listener->draw_frames(engine->draw_frame_listener->data);

	engine_calculate_fps();
}

static void
engine_set_ortho(float left, float right, float bottom, float top)
{
	engine->ortho_left   = left;
	engine->ortho_right  = right;
	engine->ortho_bottom = bottom;
	engine->ortho_top    = top;

	glOrtho(left, right, bottom, top, -1, 1);
}

static void
engine_on_ui_expose(UIEventResize *er)
{
	/* Set the viewport to the window size */
	glViewport(0, 0, er->width, er->height);

	/* Objects in the rendering area must maintain the proportions. So, let's enable Ortho */
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	float aspect;
	if (er->width >= er->height) {
		aspect = (float)er->width / (float)er->height;
		engine_set_ortho(-aspect, aspect, -1, 1);
	} else {
		aspect = (float)er->height / (float)er->width;
		engine_set_ortho(-1, 1, -aspect, aspect);
	}

	/* Returns to the model view */
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

void
engine_loop(void)
{
	ui_set_resize_listener(engine_on_ui_expose);
	ui_set_loop_listener(engine->ui, draw_frames, engine);

	/* FPS calculation */
	start = time(NULL);
	frames = 0;

	ui_loop(engine->ui);
}

void
mouse_button_press_event(UIMouseButtonPressed *mbp)
{
	float oglX = engine->ortho_left + ((float) mbp->x / engine->ui->width) * (engine->ortho_right - engine->ortho_left);
	float oglY = engine->ortho_top - ((float) mbp->y / engine->ui->height) * (engine->ortho_top - engine->ortho_bottom);

	mouse_button_event->on_mouse_button_pressed(oglX, oglY, mouse_button_event->data);
}

void
engine_set_mouse_button_listener(void (*event)(float x, float y, void *data), void *data)
{
	init_log();

	mouse_button_event = malloc(sizeof(MouseButtonEvent));
	if (mouse_button_event == NULL) {
		log_error(_log, "Error allocating mouse button event");
		exit(EXIT_FAILURE);
	}

	mouse_button_event->on_mouse_button_pressed = event;
	mouse_button_event->data = data;

	ui_set_mouse_press_listener(mouse_button_press_event, mouse_button_event);
}

static void
engine_dispatch_ui_events(int type)
{
	int event_type = 0;
	switch (type) {
#ifdef X11
		case ButtonPress:
			event_type = ENGINE_MOUSE_PRESSED;
			break;
#endif
		default:
			event_type = 0;
			break;
	}
	dispatch_ui_event(event_type);
}

void
engine_input(void (*f_input)(int engine_input))
{
	ui_set_generic_listener(engine_dispatch_ui_events);
	dispatch_ui_event = f_input;
}

void
engine_set_rendering_background(Engine *engine, float r, float g, float b, float a)
{
	if (engine->rendering_background == NULL) {
		engine->rendering_background = color_new(r, g, b, a);
	} else {
		color_set_rgba(engine->rendering_background, r, g, b, a);
	}
}

void
engine_set_rendering_background_c(Engine *engine, Color *color)
{
	engine_set_rendering_background(engine, color->r, color->g, color->b, color->a);
}

void
engine_set_rendering_listener(Engine *engine, void (*draw_frames)(void *data), void *data)
{
	engine->draw_frame_listener = malloc(sizeof(DrawFrameListener));
	engine->draw_frame_listener->draw_frames = draw_frames;
	engine->draw_frame_listener->data = data;
}