#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "debug.h"

/**
 * Read data from a slow device
 *
 * return 1 when a complete NULL terminated line has been read
 *
 * return 0 when a partial line has been read and appended to the
 *		 buffer at @offset
 *
 * return negative on error
 */
static int read_log_line(int infd, char *buf, size_t bufsize, int *offset)
{
	int ret;
	int i;

	ret = read(infd, buf + *offset, bufsize - *offset - 1);
	if (ret < 0) {
		pr_err("read: %m\n");
		return -1;
	}

	if (ret == 0) {
		pr_err("Read EOF, stopping\n");
		return -1;
	}
	buf[*offset + ret] = 0;

	for (i = 0; i < ret; i++) {
		if (buf[i + *offset] == '\n' ||
		    buf[i + *offset] == '\r') {
			/*
			 * Got a complete line when there is a newline
			 * at the end. Remove the newline and possible
			 * other junk, such as '\r'
			 */
			buf[i + *offset] = 0;
			*offset = 0;

			return 1;
		}

		/*
		 * Fixme! Nothing guarantees that there isn't actually
		 * more data (a part of a new log entry perhaps) after
		 * the newline. So in rare cases (we are prevented
		 * from reading the serial line in very long time) we
		 * might lose data from the stream..
		 */
	}

	*offset += ret;
	return 0;
}

int read_data(int infd, int outfd)
{
	struct epoll_event ev;
	time_t start_time = 0, cur_time;
	int epoll_fd;
	int ret;
	char buf[256];
	int offset = 0;

	epoll_fd = epoll_create(1);
	if (epoll_fd < 0) {
		pr_err("Failed to create epoll socket: %m\n");
		return -1;
	}

	ev.events = EPOLLIN;
	ev.data.fd = infd;
	if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, infd, &ev) == -1) {
		pr_err("epoll_ctl: %m\n");
		return 1;
	}

	while (1) {
		char str[320];
		int len;

		ret = epoll_wait(epoll_fd, &ev, 1, -1);
		if (ret == 0)
			continue;

		if (ret < 0) {
			pr_err("epoll: %m\n");
			return -1;
		}

		ret = read_log_line(infd, buf, sizeof(buf), &offset);
		if (ret < 0)
			return ret;

		if (ret == 0)
			continue;

		if (strlen(buf) < 5) {
			pr_debug("discarding truncated log entry\n");
			offset = 0;
			continue;
		}

		if (!start_time)
			start_time = time(NULL);

		cur_time = time(NULL);

		pr_info("%s\n", buf);

		if (!outfd)
			continue;

		len = snprintf(str, sizeof(str),
			"%ld;%s\n", cur_time - start_time, buf);

		ret = write(outfd, str, len);
		if (ret < 0) {
			pr_err("write: %m\n");
			break;
		}
	}

	return 0;
}