/* server.c -- server TCP program, adapted from Comer's book */

/* Usage:  srv [-d] [port] [amplcmd] */

#ifndef unix
#define WIN32
#include <windows.h>
#include <winsock.h>

#else
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <dirent.h>

#endif

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

FILE	*logfp	= stderr;
int	port	= 5194;		/* unlikely port */

char	*amplcmd[] = { "ampl", "-b", 0 };

#define	dfprintf  if (dbg) fprintf
int	dbg	= 1;

#define	eq(s1, s2) (strcmp(s1, s2) == 0)

int	inetd	= 0;	/* 1 => running from inetd */

#define	QLEN	5		/* input queue length */
struct	protoent *ptrp;		/* protocol table entry */
struct	sockaddr_in sad;	/* server adr */
struct	sockaddr_in cad;	/* client adr */

void	fatal(char *);
int	start(char **prog, int *fdw, int *fdr);
int	runsrv(int sd2);
int	runampl(int);

int main(int argc, char *argv[])
{
	int val, sd;

	if (argc > 1 && eq(argv[1], "-?")) {
		fprintf(stderr, "Usage:  srv [-d] [port] [amplcmd]\n");
		exit(0);
	}
	for ( ; argc > 1 && argv[1][0] == '-'; argc--, argv++) {
		if (eq(argv[1], "-d")) {
			dbg = 0;
		} else if (strcmp(argv[1], "-cd") == 0) {
			chdir(argv[2]);
			argc--; argv++;
		} else if (eq(argv[1], "-l")) {
			time_t now;
			time(&now);
			logfp = freopen(argv[2], "a", stderr);
			fprintf(logfp, "\n%s\n", ctime(&now));
			argc--; argv++;
		} else if (eq(argv[1], "-i")) { /* start from inetd */
			inetd++;
		}
	}

	memset((char *) &sad, 0, sizeof(sad));
	sad.sin_family = AF_INET;	/* internet */
	sad.sin_addr.s_addr = INADDR_ANY;	/* local IP address */

	if (argc > 1 && atoi(argv[1]) > 0)
		port = atoi(argv[1]);
	if (argc > 2)
		amplcmd[0] = argv[2];

	if (inetd) {
		fprintf(logfp, "srv: running from inetd\n");
		runsrv(0);
		exit(1);
	}

	if (port > 0)
		sad.sin_port = htons((u_short) port);
	if ((ptrp = getprotobyname("tcp")) == NULL) {
		fprintf(logfp, "srv: can't map TCP to protocol number\n");
		perror("");
		exit(1);
	}

	if ((sd = socket(PF_INET, SOCK_STREAM, ptrp->p_proto)) < 0) {
		fprintf(logfp, "srv: socket creation failed\n");
		perror("");
		exit(1);
	}
	if (bind(sd, (struct sockaddr *) &sad, sizeof(sad)) < 0) {
		fprintf(logfp, "srv: bind %d failed\n", port);
		perror("");
		exit(1);
	}
	val = 1;
	setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *) &val, sizeof(int));
	if (listen(sd, QLEN) < 0) {
		fprintf(logfp, "srv: listen failed\n");
		perror("");
		exit(1);
	}

	for (;;) {
		int alen = sizeof(cad), sd2;
		fprintf(logfp, "about to accept\n");

		if ((sd2 = accept(sd, (struct sockaddr *) &cad, &alen)) < 0) {
			fprintf(logfp, "srv: accept failed\n");
			perror("");
			exit(1);
		}
		fprintf(logfp, "srv: accepted\n");

		if (fork() == 0) {
			close(sd);	/* child does this */
			runsrv(sd2);
			exit(0);
		}
		close(sd2);	/* parent does this */
	}
}

void filenames(char *pat, char *buf) /* long list of filenames */
{
	DIR *dp;
	struct dirent *dirp;
	char *MODELDIR = ".";		/* for now */

	buf[0] = 0;
	if ((dp = opendir(MODELDIR)) == NULL) {
		strcat(buf, "\n");
		return;
	}
	for ( ; (dirp = readdir(dp)) != NULL; ) {
		if (eq(pat, dirp->d_name + strlen(dirp->d_name)-strlen(pat))) {
			strcat(buf, dirp->d_name);
			strcat(buf, "\n");
		}
	}
	closedir(dp);
}

int getline(int fd, char *buf) /* unbuffered input */
{
	char c;
	int i;

	for (i = c = 0; read(fd, &c, 1) > 0 && c != '\n'; i++)
		buf[i] = c;
	buf[i] = 0;
	return (c == '\n') ? i : -1;
}

int runsrv(int sd2)
{
	char cmd[100], opt[100], buf[2000], buf2[2000];

	for (; getline(sd2, buf) >= 0; ) {

/* weird botched protocol: rcv expects to see "type\nreal data" */
/* so files, get (and ultimately others) add this at front. */
		sscanf(buf, "%*s %s %s", cmd, opt); /* skip count */
		dfprintf(logfp, "srv got [%s] [%s] [%s]\n", buf, cmd, opt);
		if (eq(cmd, "files")) {	/* filenames */
			filenames(opt, buf2);	/* opt is .mod or .dat */
			sprintf(buf, "%d files\n%s", 6+strlen(buf2), buf2);
			write(sd2, buf, strlen(buf));
		} else if (eq(cmd, "cd")) {
			chdir(opt);
		} else if (eq(cmd, "echo")) {
			strcat(buf, "\n");
			sprintf(buf2, "%d %s", strlen(buf), buf);
			write(sd2, buf2, strlen(buf2));
		} else if (eq(cmd, "ampl")) {
			sprintf(buf, "%d %s", strlen("prompt1\n"), "prompt1\n");
			write(sd2, buf, strlen(buf));
			runampl(sd2);
		} else if (eq(cmd, "get")) {	/* content of file */
			int i, c;
			FILE *fin;
			fin = fopen(opt, "r");
			for (i = 0; (c = getc(fin)) != EOF; i++)
				buf2[i] = c;
			buf2[i] = 0;
			sprintf(buf, "%d get\n%s", 4+strlen(buf2), buf2);
			write(sd2, buf, strlen(buf));
		} else {
			sprintf(buf, "%d %s",
				strlen("srv cmd error\n"), "srv cmd error\n");
			write(sd2, buf, strlen(buf));
		}
		sprintf(buf, "%d %s", strlen("prompt1\n"), "prompt1\n");
		write(sd2, buf, strlen(buf));
	}
	return 0;
}

int runampl(int sd2)
{
	int fdr, fdw, i, n, done;
	pid_t apid;
	char buf[50000], buf2[50000];	/* SLEAZE! */

	if ((apid = start(amplcmd, &fdw, &fdr)) == 0) {
		fprintf(logfp, "srv: start %s failed\n", amplcmd[0]);
		perror("");
		exit(1);
	}
	fprintf(logfp, "started %s\n", amplcmd[0]);

	/* absorb initial output from ampl */
	for (i = n = 0; read(fdr, &buf[i], 1) > 0 && isdigit(buf[i]); i++)
		n = 10 * n + buf[i] - '0';
	read(fdr, buf, n);
	buf[n] = 0;
	dfprintf(logfp, "srv read initial ampl %d [%s]\n", n, buf);

	for (done = 0; done == 0; ) {
		dfprintf(logfp, "top of srv read loop\n");
		/* read 1 cmd from client */
		n = 0;
		for (i = 0; read(sd2, &buf[i], 1) > 0 && isdigit(buf[i]); i++)
			n = 10 * n + buf[i] - '0';
		read(sd2, buf, n);
		buf[n] = 0;
		dfprintf(logfp, "srv read %d [%s] from cli\n", n, buf);
		sprintf(buf2, "%d %s", n, buf);
		write(fdw, buf2, strlen(buf2));

		/* read replies from ampl until prompt: */
		while (done == 0) {
			n = 0;
			for (i = 0; read(fdr, &buf[i], 1) > 0 && isdigit(buf[i]); i++)
				n = 10 * n + buf[i] - '0';
				if (n <= 0) {
					fprintf(logfp, "ampl says %d\n", n);
					done = 1;
					break;
				}
			if (done)
				break;
			read(fdr, buf, n);
			buf[n] = 0;
			dfprintf(logfp, "srv read [%s] from ampl\n", buf);

			sprintf(buf2, "%d %s", n, buf);
			write(sd2, buf2, strlen(buf2));
			if (strncmp(buf, "prompt", 6) == 0)
				break;
			if (strncmp(buf, "exit\n", 5) == 0) {
				done = 1;
				break;
			}
		}
	}
	/* kill apid? */
	return 0;
}

int start(char **prog, int *fdw, int *fdr)
{
	int fd1[2], fd2[2];
	pid_t pid;

	if (pipe(fd1) < 0 || pipe(fd2) < 0)
		fatal("pipe error");
	if ((pid = fork()) < 0)
		fatal("forking error");
	if (pid == 0) {	/* child */
		close(fd1[1]);
		close(fd2[0]);
		if (fd1[0] != STDIN_FILENO) {
			if (dup2(fd1[0], STDIN_FILENO) != STDIN_FILENO)
				fatal("dup2 error to stdin");
			close(fd1[0]);
		}
		if (fd2[1] != STDOUT_FILENO) {
			if (dup2(fd2[1], STDOUT_FILENO) != STDOUT_FILENO)
				fatal("dup2 error to stdout");
			close(fd2[1]);
		}
		if (execvp(prog[0], prog) < 0)
			fatal("exec error");
		
	} else {	/* parent */
		close(fd1[0]);
		close(fd2[1]);
		*fdw = fd1[1];
		*fdr = fd2[0];
	}
	return pid;
}

void fatal(char *msg)
{
	fprintf(logfp, "srv: fatal: %s\n", msg);
	perror("");
	exit(1);
}