#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <stdio.h>
#include <wait.h>
#include <ctype.h>


char *defmanpath = "/usr/local/share/man:/usr/share/man:/usr/man";
char *defsections = "1:n:l:8:3:2:3posix:3pm:3perl:5:4:9:6:7";


void
die(char *str)
{
	perror(str);
	exit(1);
}


/*
** Render the specified man page and invoke a pager on it.
** Will only return if there's no such page.
*/
int
display(char *path, char *sec, char *name)
{
	char buf[BUFSIZ];
	struct stat sb;
	char *catprog;
	int pd1[2], pd2[2], pd3[2];
	pid_t pid;

	snprintf(buf, sizeof buf, "%s/man%s/%s.%s", path, sec, name, sec);
	if (stat(buf, &sb) != -1) {
		catprog = "cat";
		goto displ;
	}
	snprintf(buf, sizeof buf, "%s/man%s/%s.%s.gz", path, sec, name, sec);
	if (stat(buf, &sb) != -1) {
		catprog = "zcat";
		goto displ;
	}
	return 0;

displ:
	/* Have zombies burried automatically */
	signal(SIGCHLD, SIG_IGN);

	if (pipe(pd1) == -1) {
		die("pipe");
	}
	if ((pid = fork()) == -1) {
		die("fork");
	} else if (!pid) {
		/* child */
		close(1); dup(pd1[1]); close(pd1[1]);
		close(pd1[0]);
		execlp(catprog, catprog, buf, NULL);
		die("exec");
	}
	/* parent */
	close(pd1[1]);

	if (pipe(pd2) == -1) {
		die("pipe");
	}
	if ((pid = fork()) == -1) {
		die("fork");
	} else if (!pid) {
		/* child */
		close(0); dup(pd1[0]); close(pd1[0]);
		close(1); dup(pd2[1]); close(pd2[1]);
		close(pd2[0]);
		execlp("nroff", "nroff", "-Tlp", "-man", NULL);
		die("exec");
	}
	/* parent */
	close(pd2[1]);

	if (pipe(pd3) == -1) {
		die("pipe");
	}
	if ((pid = fork()) == -1) {
		die("fork");
	} else if (!pid) {
		/* child */
		close(0); dup(pd2[0]); close(pd2[0]);
		close(1); dup(pd3[1]); close(pd3[1]);
		close(pd3[0]);
		execlp("col", "col", "-x", NULL);
		die("exec");
	}
	/* parent */
	close(pd3[1]);

	/* parent */
	close(0); dup(pd3[0]); close(pd3[0]);
	execlp("less", "less", "-is", NULL);
	die("exec");
	return 0;
}


/*
** Search `manpath' for man page `name' in section `sec'.
*/
int
process(char *name, char *sec, char *manpath)
{
	pid_t pid;
	char *str, *tok;
	int status;

	if (!(manpath = strdup(manpath))) {
		die("strdup");
	}

	if ((pid = fork()) == -1) {
		perror("fork");
		exit(1);
	} else if (pid == 0) {
		/* child to try to display the man page */
		for (str=manpath; ; str=NULL) {
			if (!(tok = strtok(str, ":"))) {
				break;
			}
			display(tok, sec, name);  /* returns only on failure */
		}
		/* not found */
		exit(1);
	}
	free(manpath);
	wait(&status);
	return (WIFEXITED(status) && WEXITSTATUS(status)==0);
}


int
main(int argc, char *argv[])
{
	char *sec = NULL;
	char *manpath, *str, *tok, *sections;
	int first = 1;

	if (!(manpath = getenv("MANPATH"))) {
		manpath = defmanpath;
	}
	if (!(sections = getenv("MANSECTIONS"))) {
		sections = defsections;
	}

	if (argc < 2) {
		fprintf(stderr, "Usage: %s [SECTION] NAME...\n", argv[0]);
		exit(1);
	}
	argv++; argc--;

	/* check if first arg is a section number */
	if (isdigit(*argv[0])) {
		sec = argv[0];
		argv++; argc--;

	}

	for (; *argv; argv++) {
		int success = 0;

		if (!first) {
			fprintf(stderr, "\nNEXT man page `%s'  --  \\n to display, "
					"^D to skip, ^C to quit\n", *argv);
			if (getchar() == EOF) {
				argv++;
			}
		}
		first = 0;

		if (sec) {
			success = process(*argv, sec, manpath);
		} else {
			char *cp;

			if (!(cp = strdup(sections))) {
				die("strdup");
			}
			for (str=cp; ; str=NULL) {
				if (!(tok = strtok(str, ":"))) {
					break;
				}
				if (process(*argv, tok, manpath)) {
					success = 1;
					break;
				}
			}
			free(cp);
		}
		if (!success) {
			fprintf(stderr, "No man page  for `%s' found.\n", *argv);
		}
	}

	return 1;
}