#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>

/* Name of news Server */
#define SERVER "miner.mathematik.uni-ulm.de"
/* Port of news Server */
#define PORT   "8080"
/* Name of group to examine */
#define GROUP  "miner.local.softss02"
/* Number of post to  look up */
#define NR     5

/* Skip rest of line until we find the \r\n sequence. This works for
 * lines of arbitrary length and also handles things like eof and \r\r\r\n 
 * correctly.
 */
void skipline (FILE * in ) {
	int c, gotr;
	gotr = 0;
	while (1) {
		c = fgetc (in);
		if (c < 0)
			break;
		if (gotr && (c == '\n'))
			break;
		gotr = (c == '\r');
	}
}

/* This function reads a line starting with a integer return code 
 * from the file in. The return code is converted to an integer and
 * returned, the rest of the line is discared. Note that this
 * function works for lines of arbitrary length.
 */
int codeline (FILE * in)
{
	int code;
	if (fscanf (in, "%d", &code) != 1)
		return -1;
	skipline (in);
	return code;
}

/* Print the Subject, From and Date Line of the header to stdout. */
void summary (FILE * in)
{
	char line[100];
	int header = 1, print;
	
	while (1) {
		fgets (line, 100, in);
		/* End of file? */
		if (feof (in))
			break;
		/* End of text for this article ? */
		if (strcmp (line, ".\r\n") == 0)
			break;
		/* End of Message header? */
		if (strcmp (line, "\r\n") == 0)
			header = 0;
		/* Subject, From or Date line? */
		if (!header)
			continue;
		print = 0;
		if ((strncmp (line, "Subject: ", 9) == 0) ||
		    (strncmp (line, "From: ", 6) == 0) ||
		    (strncmp (line, "Date: ", 6) == 0)) {
		    	printf ("%s", line);
			print = 1;
		}
		/* Skip/Print rest of line */
		while (1) {
			if (strstr (line, "\r\n"))
				break;
			fgets (line, 100, in);
			if (feof (in))
				break;
			if (print)
				printf ("%s", line);
		}
	}
	printf ("\n");
}


int main ()
{
	int p1[2], p2[2], pid, min, max, code, pos, found, cnt;
	FILE * out, * in;  /* Buffered file-Descriptors for parent */
	char line[100];

	/* Create two pipes for stdin and stdout */
	if (pipe (p1) < 0) {
		perror ("pipe");
		exit (1);
	}
	if (pipe (p2) < 0) {
		perror ("pipe");
		exit (1);
	}
	/* Create Child-Process for network kommunication */
	pid = fork ();
	if (pid < 0) {
		perror ("fork");
		exit (1);
	}
	if (pid == 0) {   /* Child Process */
		/* Make pipe p1 our stdinput */
		close (p1[1]);
		close (0);
		dup (p1[0]);
		close (p1[0]);
		/* Make pipe p2 out stdoutput */
		close (p2[0]);
		close (1);
		dup (p2[1]);
		close (p2[1]);
		/* Start nc Process */
		execlp ("nc", "nc", SERVER, PORT, NULL);
		/* Exec failed. Try netcat instead */
		perror ("execlp");
		execlp ("netcat", "netcat", SERVER, PORT, NULL);
		perror ("execlp");
		exit (1);
	}  /* End of child */
	/* Parent */
	/* Close pipe ends that we don't need */
	close (p1[0]);
	out = fdopen (p1[1], "w");
	close (p2[1]);
	in = fdopen (p2[0], "r");
	/* Handle the NNTP dialog */
	/* Wait for welcome message from server */
	code = codeline (in);
	if ((code != 200) && (code != 201)) {
		fprintf (stderr, "No connection to server (code %d)\n", code);
		exit (1);
	}
	/* Select newsgroup */
	fprintf (out, "group %s\r\n", GROUP);
	fflush (out);
	cnt = fscanf (in, "%d %*d %d %d", &code, &min, &max);
	/* The server must send at least a return code. */
	if (cnt < 1) {
		fprintf (stderr, "Bad response from server while selecting group\n");
		exit (1);
	}
	/* If the code is not 211 group selection failed. */ 
	if (code != 211) {
		fprintf (stderr, "Error selecting group (code %d)\n", code);
		exit (1);
	}
	/* If the code is 211 the server must send meaningful min and max
	 * values. */
	if (cnt != 3) {
		fprintf (stderr, "Bad response from server while selecting group\n");
		exit (1);
	}
	/* Group selection successful. Skip rest of group selection line. */
	skipline (in);
	/* Retrieve at most 5 article headers and From and Subject lines. */
	pos = max; found = 0;
	while ((pos >= min) && (pos <= max) && (found < 5)) {
		/* Try to get header of posting at current position. */
		fprintf (out, "head %d\r\n", pos);
		fflush (out);
		code = codeline (in);
		switch (code) {
		case 220: /* Head and body follows */
		case 221: /* Head follows */
			/* Print message summary to stdout. */
			summary (in);
			found++;
			break;
		case 222: /* Only body follows */
		case 223: /* No text follows. */
			fprintf (stderr, "Server won't send requested header (code %d)\n", code);
			exit (1);
			break;
		case 412: /* Server says: No newsgroup selected */
		case 420: /* Server says: No current article selected */
			fprintf (stderr, "Server is in strange state (code %d)\n", code);
			exit (1);
			break;
		case 423: /* No such article number */
		case 430: /* No such article */
			/* Just skip this article number and try the next. */
			break;
		default: /* Unexpected Error message */
			fprintf (stderr, "Server sent unexpected error message (code %d)\n", code);
			break;
		}
		pos--;
	}
	/* Terminate connection */
	fprintf (out, "quit\r\n");
	fflush (out);
	fclose (out);
	/* Do not just close the pipe, wait for end of file! The child
	 * process may still write data to the pipe. */
	while (1) {
		fgets (line, 100, in);
		if (feof (in))
			break;
	}
	/* Wait for termination of child. */
	wait (NULL);
	return 0;
}