/* See LICENSE file for copyright and license details. */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <curses.h>

void freefilebuf(char **buffer, ssize_t cnt)
{
	if (!buffer || !cnt)
		return;

	while (cnt)
		free(buffer[--cnt]);

	free(buffer);
}

int readfile(FILE *fp, char ***buffer, ssize_t *count, int ncols)
{
	char **buf, **tmp;
	char *line;
	int ret;
	size_t chunks, sz;
	ssize_t cnt, len, cuts, clen;
#define CHUNKS 128

	if (!fp)
		return -1;

	buf = malloc(sizeof(char *) * CHUNKS);
	if (buf == NULL) {
		perror(NULL);
		return -1;
	}

	ret = 0;
	cnt = 0;
	chunks = CHUNKS;

	for (cnt = 0; ; cnt++) {
		if (cnt == chunks-5) {
			chunks += CHUNKS;
			tmp = realloc(buf, chunks * sizeof(char *));
			if (tmp == NULL) {
				ret = -1;
				break;
			}
			buf = tmp;
		}
		line = NULL;
		sz = 0;
		if ((len = getdelim(&line, &sz, '\n', fp)) == -1) {
			if (ferror(fp))
				ret = -1;
			break;
		}
		line[--len] = '\0'; /* remove the newline */
		if (len > ncols) {
			char *p;
			cuts = 0;
			clen = len;
			p = line;
			while ((clen > 0) && (ret != -1)) {
				buf[cnt+cuts] = strndup(p, (clen > ncols) ? ncols - 1 : clen);
				p += ncols - 1;
				clen -= ncols - 1;
				cuts++;
				if (cnt+cuts == chunks-5) {
					chunks += CHUNKS;
					tmp = realloc(buf, chunks * sizeof(char *));
					if (tmp == NULL) {
						ret = -1;
						break;
					}
					buf = tmp;
				}
			}
			cnt += (cuts - 1);
			free(line);
			if (ret == -1)
				break;
		}
		else {
			buf[cnt] = line;
		}
	}

	if (ret == -1) {
		perror(NULL);
		freefilebuf(buf, cnt);
	}
	else {
		*buffer = buf;
		*count = cnt;
	}

	free(line);

	return ret;
}

void displayfile(FILE *fp, long fpos, int r, int c, int y, int x)
{
	WINDOW *win;
	char **lbuf;
	int i, ch, inc, loc;
	ssize_t n, ctop, start;

	if (fseek(fp, fpos, SEEK_SET) == -1) {
		perror(NULL);
		return;
	}

	if ((readfile(fp, &lbuf, &n, c) == -1) || (n <= r)) {
		freefilebuf(lbuf, n);
		return;
	}

	inc = 0;
	ctop = start = n - r;

	win = newwin(r, c, y, x);
	idlok(win, TRUE);
	scrollok(win, TRUE);
	wsetscrreg(win, 0, r-1);

	for (i = 0; i < r && i < n; i++)
		mvwaddnstr(win, i, 0, lbuf[ctop+i], c);
	wrefresh(win);

	while ((ch = getch()) != 'q') {
		if (n <=r)
			continue;
		switch (ch) {
			case 'f':
				if (ctop + r >= n)
					break;
				ctop += r;
				if (ctop > n - r)
					ctop = (n - r);
				break;
			case 'b':
				if (ctop == 0)
					break;
				ctop -= r;
				if (ctop < 0)
					ctop = 0;
				break;
			case 'j':
				if (ctop + r >= n)
					break;
				inc = 1;
				ctop++;
				break;
			case 'k':
				if (ctop == 0)
					break;
				inc = -1;
				ctop--;
				break;
			default:
				break;
		}
		if (start != ctop) {
			if (inc) {
				loc = (inc < 0) ? 0 : r - 1;
				wscrl(win, inc);
				mvwaddnstr(win, loc, 0, lbuf[ctop+loc], c);
				wrefresh(win);
				inc = 0;
			}
			else if (start != ctop) {
				wclear(win);
				for (i = 0; i < r; i++)
					mvwaddnstr(win, i, 0, lbuf[ctop+i], c);
				wrefresh(win);
			}
			start = ctop;
		}
	}

	freefilebuf(lbuf, n);
	delwin(win);
}