#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *progname;
int charmode = 0;
int linemode = 0;
char *word = NULL;
int xflag = 0;

struct node {
	struct node *next;
	char *val;
};

void
usage(void)
{
	fprintf(stderr, "Usage: %s [-c] [-l] [-s WORD [-x]] [FILE...]\n",
			progname);
	exit(1);
}

/*
** returns line in new memory
*/
char *
readlongline(FILE *fp)
{
	char *bufp;
	int size = 8;
	char *cp;
	int offset = 0;

	if (!(bufp = malloc(size))) {
		fprintf(stderr, "Out of mem\n");
		exit(1);
	}
	*bufp = '\0';
	cp = bufp;
	while (fgets(cp, size-offset, fp)) {
		cp += strlen(cp) - 1;
		if (*cp == '\n') {
			*cp = '\0';
			return bufp;
		}
		size *= 2;
		if (!(bufp = realloc(bufp, size))) {
			fprintf(stderr, "Out of mem\n");
			exit(1);
		}
		offset = strlen(bufp);
		cp = bufp + offset;
	}
	return (*bufp) ? bufp : NULL;  /* possibly incomplete last line */
}

void
rev_line(char *line)
{
	char *cp = line;
	char *ep = line + strlen(line) - 1;
	char tmp;

	while (cp < ep) {
		tmp = *cp; *cp = *ep; *ep = tmp;
		cp++; ep--;
	}
}

void
processfile(FILE *fp)
{
	char *line;
	struct node *stack = NULL;
	struct node *np;
	int revline;
	int hasword = word ? 0 : 1;

	while ((line = readlongline(fp))) {
		revline = word ? 0 : 1;
		if (word && strstr(line, word)) {
			hasword = 1;
			revline = 1;
		}
		if (charmode && (xflag != revline)) {
			rev_line(line);
		}
		if (linemode) {
			if (!(np = malloc(sizeof(struct node)))) {
				fprintf(stderr, "Out of mem");
				exit(1);
			}
			np->val = line;
			/* push */
			np->next = stack;
			stack = np;
		} else {
			printf("%s\n", line);
			free(line);
		}
	}
	if (linemode) {
		if (hasword == xflag) {
			struct node *temp = NULL;

			/* reverse order of stack, i.e. restore normal order */
			while ((np = stack)) {
				stack = np->next;
				np->next = temp;
				temp = np;
			}
			stack = temp;
		}
		while ((np = stack)) {
			stack = stack->next;  /* pop */
			printf("%s\n", np->val);
			free(np->val);
			free(np);
		}
	}
}

int
main(int argc, char *argv[])
{
	char *cp;
	FILE *fp;

	progname = argv[0];
	argc--; argv++;  /* remove program name */

	if (strcmp(progname, "lreverse")==0
			|| strcmp(progname, "./lreverse")==0) {
		linemode = 1;
	}

	for (; *argv && **argv=='-'; argc--,argv++) {
		cp = *argv + 1;
		if (!*cp) {
			/* ``-'' is no option but use stdin as first file */
			break;
		}
		switch (*cp) {
		case 'c':
			charmode = 1;
			break;
		case 'l':
			linemode = 1;
			break;
		case 'x':
			if (cp[1]) {
				fprintf(stderr, "Unknown option `-%s'\n", cp);
				usage();
			}
			xflag = 1;
			break;
		case 's':
			if (cp[1]) {
				word = cp + 1;
			} else if (*++argv) {
				word = *argv;
				argc--;
			} else {
				usage();
			}
			break;
		default:
			usage();
		}
	}
	if (!linemode && !charmode) {
		charmode = 1;
	}

	if (!*argv) {
		processfile(stdin);
		return 0;
	}
	for (; *argv; argv++,argc--) {
		if (strcmp(*argv, "-") == 0) {
			processfile(stdin);
		} else {
			if (!(fp = fopen(*argv, "r"))) {
				fprintf(stderr,"Could not open `%s'\n", *argv);
				continue;
			}
			processfile(fp);
			fclose(fp);
		}
	}

	return 0;
}