/**
 * Gets the i/o for a shell script and outputs it.
 * 
 * Usage:
 * replay_shell [-r] [-f filename] pid
 *
 * -r: Realtime. Wait for the correct times.
 * -f: Specify a shell replay file to take input from, rather than retrieving
 *     it from the database.
 * 
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

int main (int argc, char * argv[]) {
	FILE * pd;                         // Process to read data from.
	char   c                  = 0;     // For handling input args.
	char   cmd [256];                  // Buffer to hold command string.
	char   buf [32738];                // Buffer to hold input stream.
	char * filename;                   // Name of the file to read data from.
	int    len;                        // Amount of data read from stream.
	int    i;                          // Counter.
	int    realtime           = 0;     // Should we display in realtime, or not?
	int    from_file          = 0;     // Are we reading from a file, or not?
	int interval              = -1;    // Amount of time to wait before printing current i/o data.
	unsigned long long last_timestamp; // Time of last i/o event.
	
	while (c != -1) {
		c = getopt (argc, argv, "rf:");
		switch (c) {
		case -1:
			break;
		case 'r':
			realtime = 1;
			break;
		case 'f':
			from_file = 1;
			filename = optarg;
			break;
		default:
			printf ("Usage: replay_shell [-r] [-f filename] pid\n");
			return 1;
		}
	}
	
	if (argc == 1) {
		printf ("Usage: replay_shell [-r] [-f filename] pid\n");
		return 1;
	}

	// Open the file (or process).
	if (from_file) {
		snprintf (cmd, 256, "cat %s", filename);
		pd = popen (cmd, "r");
		if (!pd) {
			perror ("Unable to open file");
			return 1;
		}
	} else {
		snprintf (cmd, 256, "./get_io 2> /dev/null %s", argv[optind]);
		pd = popen (cmd, "r");
		if (!pd) {
			perror ("Unable to execute command");
			return 1;
		}
	}
	
	// Get the data.
	while (1) {
		unsigned long long timestamp;
		unsigned long long data_len;
		
		// Get the timestamp
		i = 0;
		while ( 1 ) {
			len = fread (&buf[i], 1, 1, pd);
			if (len == 0) goto done;
			if (buf[i] == '\t') break;
			i++;
		}
		timestamp = strtoull (buf, NULL, 10);
		
		// Get the data length.
		i = 0;
		while (1) {
			len = fread (&buf[i], 1, 1, pd);
			if (len == 0) goto done;
			if (buf[i] == '\t')
				break;
			i++;
		}
		data_len = strtoull (buf, NULL, 10);
		
		// Get the data. Due to character-escaping, data_len may not
		// match the *actual* length, so read 'til we hit a '\t'.
		i = fread (buf, 1, data_len, pd);

		if (realtime) {
			if (interval == -1) {
				interval = 0;
			} else {
				interval = timestamp - last_timestamp;
			}
			usleep(interval);
		}
		
		write (fileno(stdout), buf, i); 
		
		last_timestamp = timestamp;		
		
	}
	
 done:
	pclose (pd);
	return 0;
}