/*
 * UNG's Not GNU
 * 
 * Copyright (c) 2011, Jakob Kaivo <jakob@kaivo.net>
 * 
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#define _POSIX_C_SOURCE 200809L
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define K_BYTES			1024
#define M_BYTES			1048576

#define DEFAULT_BASE		"x"
#define DEFAULT_SUFFIX_LENGTH	2
#define DEFAULT_LINES		1000

static char *nextsuffix(size_t n, char s[])
{
	const char alphabet[] = "abcdefghijklmnopqrstuvwxyz";
	if (s[0] == '\0') {
		memset(s, alphabet[0], n);
		return s;
	}

	n--;
	for (;;) {
		s[n] = *(strchr(alphabet, s[n]) + 1);
		if (s[n] == '\0') {
			if (n == 0) {
				return NULL;
			}
			s[n--] = alphabet[0];
		} else {
			break;
		}
	}
	return s;
}

static int
split(const char *in, const char *base, size_t suffixlen, uintmax_t lines, uintmax_t bytes)
{
	char oname[FILENAME_MAX] = {0};
	char suffix[suffixlen + 2];
	FILE *o = NULL;
	FILE *f = stdin;
	uintmax_t count = 0;

	memset(suffix, '\0', suffixlen + 1);

	if (in != NULL && strcmp("-", in) != 0) {
		f = fopen(in, "r");
	}

	if (f == NULL) {
		perror("fopen");
		return 1;
	}

	if (in != NULL && base == NULL) {
		base = DEFAULT_BASE;
	}

	int c;
	while ((c = fgetc(f)) != EOF) {
		if (o == NULL) {
			char *s = nextsuffix(suffixlen, suffix);
			if (s == NULL) {
				fprintf(stderr, "too many chunks\n");
				return 1;
			}
			snprintf(oname, sizeof(oname), "%s%s", base, s);
			o = fopen(oname, "w");
			if (o == NULL) {
				perror("fopen");
				return 1;
			}
		}

		fputc(c, o);

		if (bytes != 0 || c == '\n') {
			count++;
		}

		if ((bytes != 0 && count == bytes) || count == lines) {
			fclose(o);
			o = NULL;
			count = 0;
		}
	}

	return 0;
}

int main(int argc, char **argv)
{
	uintmax_t lines = 0;
	uintmax_t bytes = 0;
	size_t suffix = DEFAULT_SUFFIX_LENGTH;
	char *end;

	int c;
	while ((c = getopt(argc, argv, "l:a:b:")) != -1) {
		switch (c) {
		case 'l':	/* line_count */
			bytes = 0;
			lines = strtoumax(optarg, &end, 10);
			if (*end != '\0') {
				return 1;
			}
			break;

		case 'a':	/* suffix_length */
			suffix = strtoul(optarg, &end, 10);
			if (end != NULL && strlen(end) > 0) {
				return 1;
			}
			break;

		case 'b':	/* bytes */
			lines = 0;
			bytes = strtoumax(optarg, &end, 10);
			if (*end != '\0') {
				if (!strcmp("k", end)) {
					bytes *= K_BYTES;
				} else if (!strcmp("m", end)) {
					bytes *= M_BYTES;
				} else {
					return 1;
				}
			}
			break;

		default:
			return 1;
		}
	}

	if (lines == 0 && bytes == 0) {
		lines = DEFAULT_LINES;
	}

	if (optind >= argc) {
		split(NULL, NULL, suffix, lines, bytes);
	} else if (optind == argc - 1) {
		split(argv[optind], NULL, suffix, lines, bytes);
	} else if (optind == argc - 2) {
		split(argv[optind], argv[optind + 1], suffix, lines, bytes);
	} else {
		return 1;
	}

	return 0;
}