#include <stdio.h>
#include <ncurses.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <stdbool.h>

typedef struct Buffer_struct Buffer;
struct Buffer_struct {
	char* text;
	char* start;
	char* end;
	int size;
	int gap_size;
};

Buffer* new_buffer(int size) {
	Buffer* buffer = malloc(sizeof(Buffer));
	buffer->size = size;
	buffer->text = malloc(buffer->size);

	buffer->gap_size = size;
	buffer->start = buffer->text;
	buffer->end = buffer->start + buffer->gap_size;
	return buffer;
}

void buffer_grow(Buffer* buffer) {
	int start_offset = buffer->start - buffer->text;
	buffer->size *= 2;
	buffer->text = realloc(buffer->text,buffer->size);
	buffer->start = buffer->text + start_offset;

	buffer->gap_size = 10;
	for (int i=strlen(buffer->text)-1; i > (buffer->start - buffer->text); i--) {
		*(buffer->text + i + buffer->gap_size) = *(buffer->start + i);
		*(buffer->start + i) = 0;
	}

	buffer->end = buffer->start + buffer->gap_size;
}

void buffer_insert(char ch, Buffer* buffer) {
	*(buffer->start) = ch;
	buffer->start++;
	buffer->gap_size--;
	if (buffer->gap_size == 0) {
		buffer_grow(buffer);
	}
}

void buffer_right(Buffer* buffer) {
	buffer->start++;
	buffer->end--;
}

void buffer_left(Buffer* buffer) {
	buffer->start--;
	buffer->end--;
	

}

void init_curses() {
	initscr();
	noecho();
	keypad(stdscr,TRUE);
	cbreak();
}

void sigint_handler(int dummy) {
	endwin();
	exit(130);
}

int main() {
	signal(SIGINT,sigint_handler);

	Buffer* buffer = new_buffer(10);
	init_curses();
	int ch;
	while (true) {
		clear();

		int i=0;
		if (buffer->start != buffer->text) {  /* We don't want to print the string, if the 
							gap starts at the first index of the string */

	                while (i < strlen(buffer->text)) {
	                        addch(*(buffer->text + i));
				i++;
	                        if ((buffer->start - buffer->text) == i) {  /* If we have encountered 
										the start of the gap */
	                                i += buffer->gap_size;
				}
	                }
		}

		ch = getch();

		switch(ch) {
			case KEY_BACKSPACE:
				if (buffer->start != buffer->text) {
					buffer->start--;
					buffer->gap_size++;
				}
				goto continue_while_loop;
			default:
		}
		buffer_insert(ch,buffer);

		continue_while_loop:

	}
	endwin();
}