#include <stdint.h>

const uint8_t bits[8] = {
	0x80,
	0x40,
	0x20,
	0x10,
	0x08,
	0x04,
	0x02,
	0x01
};

int maxcol = 80;
int scr_str = 0;
int scr_row = 0;
int scr_col = 0;
uint8_t bitabl[16];

uint8_t bitpos(unsigned int row, uint8_t *mask) {
	uint8_t bit = row & 7;
	*mask = bits[bit];
	return row >> 3;

}

uint8_t getbit(unsigned int row, unsigned int offset) {
	uint8_t mask;
	uint8_t byte = bitpos(row+offset, &mask);
	return (bitabl[byte] & mask);
}

void setbit(unsigned int row) {
	uint8_t mask;
	uint8_t byte = bitpos(row, &mask);
	bitabl[byte] |= mask;
}

void clrbit(unsigned int row) {
	uint8_t mask;
	uint8_t byte = bitpos(row, &mask);
	bitabl[byte] &= ~mask;
}

int find_end(char *str, int start) {
	int i;
	for (i = start; str[i]; i++);
	return i;
}

void shift_line(char *str, int cursor, int left) {
	/*int cursor = ((scr_row+scr_str)*maxcol)+scr_col;*/
	int end = find_end(str, cursor);
	if (left) {
		int i = end-1;
		int j = end;
		for (; i >= cursor; i--, j--) {
			if (i < 0) {
				i = 0;
				str[i] = 0;
				break;
			}
			str[j] = str[i];
			str[i] = 0;

		}
		/*str[i+1] = (!str[i+1]) ? ' ' : str[i+1];*/
		end = find_end(str, i+2);
		/*str[i+1] = (str[i+1] == ' ') ? 0 : str[i+1];*/
		if ((end/maxcol) > scr_row) {
			setbit(end/maxcol);
		}
	} else {
		int i = cursor;
		int j = cursor-1;
		for (; str[i]; i++, j++) {
			str[j] = str[i];
			str[i] = 0;
		}
		end = find_end(str, i);
		if (((end-1) % maxcol) == 0 && ((end-1)/maxcol) > scr_row) {
			clrbit(end/maxcol);
		}
	}
}