#include <string.h> /* for strlen(3), memcpy(3) */
#include <stdio.h> /* for printf(3) */
#include <stdlib.h> /* for realloc(3) */
#include <unistd.h> /* for read(2) */
#include "inotify_helpers.h"



struct strbuf {
	char *str; 
	size_t len;
	size_t cap;
};

static
void
strbufcat(struct strbuf *a, const char *b) {
	size_t blen = strlen(b);
	while (a->cap <= (a->len + blen)) {
		a->cap += 256;
		a->str = realloc(a->str, a->cap);
	}
	memcpy(&(a->str[a->len]), b, blen+1);
	a->len += blen;
}



static
const char *in_mask_bits[] = {
	/* main */
	"IN_ACCESS",		// 0
	"IN_MODIFY",		// 1
	"IN_ATTRIB",		// 2
	"IN_CLOSE_WRITE",	// 3
	"IN_CLOSE_NOWRITE",	// 4
	"IN_OPEN",		// 5
	"IN_MOVED_FROM",	// 6
	"IN_MOVED_TO",		// 7
	"IN_CREATE",		// 8
	"IN_DELETE",		// 9
	"IN_DELETE_SELF",	// 10
	"IN_MOVE_SELF", 	// 11
	/* gap */
	"<invalid-12>", 	// 12
	/* events sent by the kernel */
	"IN_UNMOUNT",		// 13
	"IN_Q_OVERFLOW",	// 14
	"IN_IGNORED",		// 15
	/* gap */
	"<invalid-16>", 	// 16
	"<invalid-17>", 	// 17
	"<invalid-18>", 	// 18
	"<invalid-19>", 	// 19
	"<invalid-20>", 	// 20
	"<invalid-21>", 	// 21
	"<invalid-22>", 	// 22
	"<invalid-23>", 	// 23
	/* special flags */
	"IN_ONLYDIR",		// 24
	"IN_DONT_FOLLOW",	// 25
	"IN_EXCL_UNLINK",	// 26
	"<invalid-27>", 	// 27
	"<invalid-28>", 	// 28
	"IN_MASK_ADD",		// 29
	"IN_ISDIR",		// 30
	"IN_ONESHOT",		// 31
};

char *
inotify_mask2str(uint32_t mask) {
	struct strbuf out = { 0 };
	for (size_t i = 0;
	     i < sizeof(in_mask_bits)/sizeof(in_mask_bits[0]);
	     i++) {
		if (mask & (1 << i)) {
			if (out.len > 0)
				strbufcat(&out, " | ");
			strbufcat(&out, in_mask_bits[i]);
		}
	}
	return out.str;
}



int
inotify_print_event(struct inotify_event *event) {
	char *mask = inotify_mask2str(event->mask);
	int ret = printf("{\t.wd=%d;\n"
	                 "\t.mask=%s;\n"
	                 "\t.cookie=%u;\n"
	                 "\t.len=%u;\n"
	                 "\t.name=\"%s\"; }\n",
	                 event->wd,
	                 mask,
	                 event->cookie,
	                 event->len,
	                 event->len > 0 ? event->name : "");
	free(mask);
	return ret;
}



#define	EVENT_PTR(BUF)	((struct inotify_event *)&((BUF)->dat[(BUF)->pos]))
#define	EVENT_SIZE(BUF)	(sizeof(struct inotify_event) + EVENT_PTR(BUF)->len)

struct inotify_event *
inotify_next_event_r(int fd, struct inotify_buffer *buf) {
	if (((ssize_t)(buf->len - buf->pos - sizeof(struct inotify_event)) > 0)
	 && ((ssize_t)(buf->len - buf->pos - EVENT_SIZE(buf))              > 0)) {
		buf->pos += EVENT_SIZE(buf);
	} else {
		do {
			buf->len = read(fd, buf->dat, sizeof(buf->dat));
		} while (buf->len == 0);
		buf->pos = 0;
		if (buf->len < 0) {
			return NULL;
		}
	}
	return EVENT_PTR(buf);
}

struct inotify_event *
inotify_next_event(int fd) {
	static struct inotify_buffer buf = { 0 };
	return inotify_next_event_r(fd, &buf);
}