reddit client

reddit.c

#include<u.h>
#include<libc.h>
#include<json.h>
#include<bio.h>
#include<String.h>

const char url[] = "http://www.reddit.com/.json?feed=ffffffffffffffffffffffffffffffffffffffff&user=jbedo";

/* Does the webfs query */
String *
fetch(void)
{
	int ctlfd;
	Biobuf *body;
	char buf[1024];
	int c, id, n;
	String *json;
	
	if((ctlfd = open("/mnt/web/clone", ORDWR)) < 0)
		sysfatal("fetch: cannot clone: %r");
	
	if((n = read(ctlfd, buf, sizeof buf-1)) < 0)
		sysfatal("fetch: cannot clone: %r");
	buf[n] = '\0';
	id = atoi(buf);
	if(id < 0)
		sysfatal("fetch: invalid id: %d", id);
	
	n = snprint(buf, sizeof buf-1, "url %s", url);
	if(write(ctlfd, buf, n) != n)
		sysfatal("fetch: unable to set url: %r");

	json = s_new();
	snprint(buf, sizeof buf-1, "/mnt/web/%d/body", id);
	if((body = Bopen(buf, OREAD)) == nil)
		sysfatal("fetch: cannot fetch url: %r");
	
	while((c = Bgetc(body)) > 0)
		s_putc(json, c);
	s_terminate(json);

	Bterm(body);
	close(ctlfd);
	return json;
}

/* Reddit parser */

void
childdata(Jparser *p, int root)
{
	int tok;
	
	if(p->tokens[root].type != JObj)
		sysfatal("child: expecting obj");
		
	if((tok = Jfind(p, root, "title")) < 0 ||
		p->tokens[tok].type != JStr)
		sysfatal("childdata: couldn't parse title");
	print("%s\n", Jtokstr(&p->tokens[tok]));
	if((tok = Jfind(p, root, "url")) < 0 ||
		p->tokens[tok].type != JStr)
		sysfatal("childdata: couldn't parse url");
	print("\t%s", Jtokstr(&p->tokens[tok]));
	if((tok = Jfind(p, root, "subreddit")) < 0 ||
		p->tokens[tok].type != JStr)
		sysfatal("childdata: couldn't parse subreddit");
	print("\t%s\n", Jtokstr(&p->tokens[tok]));
}

void
child(Jparser *p, int root)
{
	int tok;
	
	if(p->tokens[root].type != JObj ||
		(tok = Jfind(p, root, "kind")) < 0 ||
		strcmp(Jtokstr(&p->tokens[tok]), "t3") != 0)
		return;
	
	if((tok = Jfind(p, root, "data")) < 0)
		sysfatal("child: couldn't parse data");
	childdata(p, tok);
}

void
data(Jparser *p, int root)
{
	int i, tok, children;
	
	if(p->tokens[root].type != JObj)
		sysfatal("data: expecting data object");
		
	if((children = Jfind(p, root, "children")) < 0)
		sysfatal("data: cannot find children");
	
	for(i = 0, tok = children+1; i < p->tokens[children].nsub; i++, tok = Jnext(p, tok)){
		print("%d/\t", i+1);
		child(p, tok);
	}
}

void
top(Jparser *p)
{
	int tok;
	
	if(p->tokens[0].type != JObj ||
		(tok = Jfind(p, 0, "kind")) < 0 ||
		strcmp(Jtokstr(&p->tokens[tok]), "Listing") != 0)
		sysfatal("top: expecting listing");
	
	if((tok = Jfind(p, 0, "data")) < 0)
		sysfatal("top: cannot find data attribute");
	data(p, tok);
}

void
usage(void)
{
	fprint(2, "No arguments accepted\n");
	exits("usage");
}

void
main(int argc, char *argv[])
{
	String *json;
	Jparser p;
	
	ARGBEGIN{
	case 'h':
		usage();
	}ARGEND;
	
	if(argc != 0)
		usage();
		
	json = fetch();
	Jinit(&p);
	if(Jtokenise(&p, s_to_c(json)) < 0)
		sysfatal("JSON tokenisation error: %r");
	
	top(&p);

	exits(0);
}