/* Framework for infoscreens */

#include <fcntl.h>
#include <linux/i2c-dev.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <lcd.h>
#include <fontrender.h>
#include <infoscreens.h>

#ifdef DMALLOC
#include <dmalloc.h>
#endif

#define I2C_ADDRESS 0x20

static int i2cdev = 0;
static unsigned char screen[LCD_H][LCD_W];

void i2c_get_position(int *position, int *direction, int *backlight) {
	static int lpos = 0;
	static int ppos = 0;
	unsigned char buf;
	const int overflow_margin = 10;
	const int max_count = 127;
	
	ioctl(i2cdev, I2C_SLAVE, I2C_ADDRESS);
	if (read(i2cdev, &buf, 1) != 1)
		perror("pos_read");
	
	if (buf & 0x80)
		*backlight = 1;
	else
		*backlight = 0;
	
	buf &= 0x7F;
	
	if (buf < overflow_margin && ppos > max_count - overflow_margin) {
		// Overflow
		lpos += max_count - ppos + buf;
		*direction = 1;
	} else if (buf > max_count - overflow_margin && ppos < overflow_margin) {
		// Underflow
		lpos -= max_count - buf + ppos;
		*direction = 0;
	} else {
		lpos += buf - ppos;
		*direction = (buf > ppos) ? 1 : 0;
	}
	
	
	lpos = lpos % IS_COUNT;
	if (lpos < 0)
		lpos += IS_COUNT;
	*position = lpos;
	
	ppos = buf;
}

int is_render(int screenno, unsigned char buf[LCD_H][LCD_W]) {
	fr_title(is_list[screenno].title, screenno + 1, IS_COUNT, buf[0]);
	return is_list[screenno].render(buf);
}

void is_renderdisabled(unsigned char buf[LCD_H][LCD_W]) {
	memset(buf, 0, LCD_BYTES);
	fr_malign("LCD Display", buf[2], LCD_W);
	fr_malign("disabled", buf[3], LCD_W);
}

int is_initdisplay(int screenno) {
	int r;
	memset(screen, 0, LCD_BYTES);
	r = is_render(screenno, screen);
	lcd_update(screen);
	
	return r;
}

/* Public functions */

void is_initialize() {
	i2cdev = open("/dev/i2c/0", O_RDWR);
	is_initdisplay(0);
}

void is_upkeep() {
	static int screenno = 0;
	static int render_disabled = 0;
	static int next_update = 0;
	
	int newpos, direction, backlight;
	i2c_get_position(&newpos, &direction, &backlight);
	
	if (render_disabled) {
		if (backlight) {
			render_disabled = 0;
			screenno = newpos;
			is_initdisplay(screenno);
		}
		return;
	} else {
		if (!backlight) {
#ifdef DMALLOC
			fprintf(stderr, "Shutting down (debug build)\n");
			exit(1);
#endif
			
			is_renderdisabled(screen);
			lcd_update(screen);
			render_disabled = 1;
			return;
		}
	}
	
	if (render_disabled)
		return;
	
	if (newpos == screenno) {
		if (next_update <= time(NULL))
			next_update = is_initdisplay(screenno);
		
		return;
	}
	
	unsigned char newscreen[LCD_H][LCD_W] = {{0}};
	next_update = is_render(newpos, newscreen);
	
	if (direction)
		lcd_scroll(screen, newscreen, 1);
	else
		lcd_scroll(newscreen, screen, 0);
	
	memcpy(screen, newscreen, LCD_BYTES);
	screenno = newpos;
}