/*-
 * 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 "engine.h"
#include "../util.h"
#include "ui/ui.h"
#include "../util/list.h"

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

#define RANGE_GL 2.0f

static float xstep;
static float ystep;
static int width;
static int height;

static list_t *lines = NULL;

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

typedef struct Engine {
	UI *ui;
	void (*draw_frame)();
} Engine;

static Engine *engine;

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

void (*dispatch_ui_event)(int);
void (*on_mouse_pressed)();

void
engine_init(int w, int h)
{
	engine = malloc(sizeof(Engine));
	if (engine == NULL) {
		log_error("Error allocating memory for engine");
		exit(EXIT_FAILURE);
	}

	width = w;
	height = h;
	engine->ui = ui_init(w, h);

	xstep = RANGE_GL / (float) w;
	ystep = RANGE_GL / (float) h;

	lines = list_create();
}

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

	return line;
}

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

static void
engine_calculate_fps()
{
	frames ++;

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

static void
render_line(Line *line)
{
	float _x1 = line->x1 * xstep - 1; float _y1 = (height - line->y1) * ystep - 1;
	float _x2 = line->x2 * xstep - 1; float _y2 = (height - line->y2) * ystep - 1;

	glVertex2f(_x1, _y1);
	glVertex2f(_x2, _y2);
}

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

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

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

	glEnd();
}

static void
draw_frames()
{
	glClearColor(0.0f, 0.0f, 0.2f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT);
	glEnable(GL_LINE_SMOOTH);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	draw_lines();

	engine_calculate_fps();
}

void
engine_loop(void)
{
	ui_set_loop_listener(draw_frames);

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

	ui_loop();
}

void
engine_on_mouse_pressed(void (*event)())
{
	on_mouse_pressed = event;
}

static void
engine_dispatch_ui_events(int type)
{
	int event_type = 0;
	switch (type) {
#ifdef X11
		case ButtonPress:
			event_type = ENGINE_MOUSE_PRESSED;
			if (on_mouse_pressed != NULL) {
				on_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;
}