//
// Copyright 2017 Garrett D'Amore <garrett@damore.org>
//
// This software is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

#include <stdlib.h>
#include <string.h>

#include "core/nng_impl.h"

// Subscriber protocol.  The SUB protocol receives messages sent to
// it from publishers, and filters out those it is not interested in,
// only passing up ones that match known subscriptions.

typedef struct nni_sub_pipe  nni_sub_pipe;
typedef struct nni_sub_sock  nni_sub_sock;
typedef struct nni_sub_topic nni_sub_topic;

static void nni_sub_recv_cb(void *);
static void nni_sub_putq_cb(void *);
static void nni_sub_pipe_fini(void *);

struct nni_sub_topic {
	nni_list_node node;
	size_t        len;
	void *        buf;
};

// An nni_rep_sock is our per-socket protocol private structure.
struct nni_sub_sock {
	nni_sock *sock;
	nni_list  topics;
	nni_msgq *urq;
	int       raw;
};

// An nni_rep_pipe is our per-pipe protocol private structure.
struct nni_sub_pipe {
	nni_pipe *    pipe;
	nni_sub_sock *sub;
	nni_aio       aio_recv;
	nni_aio       aio_putq;
};

static int
nni_sub_sock_init(void **subp, nni_sock *sock)
{
	nni_sub_sock *sub;

	if ((sub = NNI_ALLOC_STRUCT(sub)) == NULL) {
		return (NNG_ENOMEM);
	}
	NNI_LIST_INIT(&sub->topics, nni_sub_topic, node);
	sub->sock = sock;
	sub->raw  = 0;

	sub->urq = nni_sock_recvq(sock);
	nni_sock_senderr(sock, NNG_ENOTSUP);
	*subp = sub;
	return (0);
}

static void
nni_sub_sock_fini(void *arg)
{
	nni_sub_sock * sub = arg;
	nni_sub_topic *topic;

	while ((topic = nni_list_first(&sub->topics)) != NULL) {
		nni_list_remove(&sub->topics, topic);
		nni_free(topic->buf, topic->len);
		NNI_FREE_STRUCT(topic);
	}
	NNI_FREE_STRUCT(sub);
}

static int
nni_sub_pipe_init(void **spp, nni_pipe *pipe, void *ssock)
{
	nni_sub_pipe *sp;
	int           rv;

	if ((sp = NNI_ALLOC_STRUCT(sp)) == NULL) {
		return (NNG_ENOMEM);
	}
	if (((rv = nni_aio_init(&sp->aio_putq, nni_sub_putq_cb, sp)) != 0) ||
	    ((rv = nni_aio_init(&sp->aio_recv, nni_sub_recv_cb, sp)) != 0)) {
		nni_sub_pipe_fini(sp);
		return (rv);
	}
	sp->pipe = pipe;
	sp->sub  = ssock;
	*spp     = sp;
	return (0);
}

static void
nni_sub_pipe_fini(void *arg)
{
	nni_sub_pipe *sp = arg;

	nni_aio_fini(&sp->aio_putq);
	nni_aio_fini(&sp->aio_recv);
	NNI_FREE_STRUCT(sp);
}

static int
nni_sub_pipe_start(void *arg)
{
	nni_sub_pipe *sp = arg;

	nni_pipe_recv(sp->pipe, &sp->aio_recv);
	return (0);
}

static void
nni_sub_pipe_stop(void *arg)
{
	nni_sub_pipe *sp = arg;

	nni_aio_stop(&sp->aio_putq);
	nni_aio_stop(&sp->aio_recv);
}

static void
nni_sub_recv_cb(void *arg)
{
	nni_sub_pipe *sp  = arg;
	nni_sub_sock *sub = sp->sub;
	nni_msgq *    urq = sub->urq;

	if (nni_aio_result(&sp->aio_recv) != 0) {
		nni_pipe_stop(sp->pipe);
		return;
	}

	sp->aio_putq.a_msg = sp->aio_recv.a_msg;
	sp->aio_recv.a_msg = NULL;
	nni_msgq_aio_put(sub->urq, &sp->aio_putq);
}

static void
nni_sub_putq_cb(void *arg)
{
	nni_sub_pipe *sp = arg;

	if (nni_aio_result(&sp->aio_putq) != 0) {
		nni_msg_free(sp->aio_putq.a_msg);
		sp->aio_putq.a_msg = NULL;
		nni_pipe_stop(sp->pipe);
		return;
	}

	nni_pipe_recv(sp->pipe, &sp->aio_recv);
}

// For now we maintain subscriptions on a sorted linked list.  As we do not
// expect to have huge numbers of subscriptions, and as the operation is
// really O(n), we think this is acceptable.  In the future we might decide
// to replace this with a patricia trie, like old nanomsg had.

static int
nni_sub_subscribe(nni_sub_sock *sub, const void *buf, size_t sz)
{
	nni_sub_topic *topic;
	nni_sub_topic *newtopic;

	NNI_LIST_FOREACH (&sub->topics, topic) {
		int rv;

		if (topic->len >= sz) {
			rv = memcmp(topic->buf, buf, sz);
		} else {
			rv = memcmp(topic->buf, buf, topic->len);
		}
		if (rv == 0) {
			if (topic->len == sz) {
				// Already inserted.
				return (0);
			}
			if (topic->len > sz) {
				break;
			}
		} else if (rv > 0) {
			break;
		}
	}

	if ((newtopic = NNI_ALLOC_STRUCT(newtopic)) == NULL) {
		return (NNG_ENOMEM);
	}
	if ((newtopic->buf = nni_alloc(sz)) == NULL) {
		return (NNG_ENOMEM);
	}
	NNI_LIST_NODE_INIT(&newtopic->node);
	newtopic->len = sz;
	memcpy(newtopic->buf, buf, sz);
	if (topic != NULL) {
		nni_list_insert_before(&sub->topics, newtopic, topic);
	} else {
		nni_list_append(&sub->topics, newtopic);
	}
	return (0);
}

static int
nni_sub_unsubscribe(nni_sub_sock *sub, const void *buf, size_t sz)
{
	nni_sub_topic *topic;
	int            rv;

	NNI_LIST_FOREACH (&sub->topics, topic) {
		if (topic->len >= sz) {
			rv = memcmp(topic->buf, buf, sz);
		} else {
			rv = memcmp(topic->buf, buf, topic->len);
		}
		if (rv == 0) {
			if (topic->len == sz) {
				nni_list_remove(&sub->topics, topic);
				nni_free(topic->buf, topic->len);
				NNI_FREE_STRUCT(topic);
				return (0);
			}
			if (topic->len > sz) {
				return (NNG_ENOENT);
			}
		}
		if (rv > 0) {
			return (NNG_ENOENT);
		}
	}
	return (NNG_ENOENT);
}

static int
nni_sub_sock_setopt(void *arg, int opt, const void *buf, size_t sz)
{
	nni_sub_sock *sub = arg;
	int           rv;

	switch (opt) {
	case NNG_OPT_RAW:
		rv = nni_setopt_int(&sub->raw, buf, sz, 0, 1);
		break;
	case NNG_OPT_SUBSCRIBE:
		rv = nni_sub_subscribe(sub, buf, sz);
		break;
	case NNG_OPT_UNSUBSCRIBE:
		rv = nni_sub_unsubscribe(sub, buf, sz);
		break;
	default:
		rv = NNG_ENOTSUP;
	}
	return (rv);
}

static int
nni_sub_sock_getopt(void *arg, int opt, void *buf, size_t *szp)
{
	nni_sub_sock *sub = arg;
	int           rv;

	switch (opt) {
	case NNG_OPT_RAW:
		rv = nni_getopt_int(&sub->raw, buf, szp);
		break;
	default:
		rv = NNG_ENOTSUP;
	}
	return (rv);
}

static nni_msg *
nni_sub_sock_rfilter(void *arg, nni_msg *msg)
{
	nni_sub_sock * sub = arg;
	nni_sub_topic *topic;
	char *         body;
	size_t         len;
	int            match;

	if (sub->raw) {
		return (msg);
	}

	body = nni_msg_body(msg);
	len  = nni_msg_len(msg);

	match = 0;
	// Check to see if the message matches one of our subscriptions.
	NNI_LIST_FOREACH (&sub->topics, topic) {
		if (len >= topic->len) {
			int rv = memcmp(topic->buf, body, topic->len);
			if (rv == 0) {
				// Matched!
				match = 1;
				break;
			}
			if (rv > 0) {
				match = 0;
				break;
			}
		} else if (memcmp(topic->buf, body, len) >= 0) {
			match = 0;
			break;
		}
	}
	if (!match) {
		nni_msg_free(msg);
		return (NULL);
	}
	return (msg);
}

// This is the global protocol structure -- our linkage to the core.
// This should be the only global non-static symbol in this file.
static nni_proto_pipe_ops nni_sub_pipe_ops = {
	.pipe_init  = nni_sub_pipe_init,
	.pipe_fini  = nni_sub_pipe_fini,
	.pipe_start = nni_sub_pipe_start,
	.pipe_stop  = nni_sub_pipe_stop,
};

static nni_proto_sock_ops nni_sub_sock_ops = {
	.sock_init    = nni_sub_sock_init,
	.sock_fini    = nni_sub_sock_fini,
	.sock_setopt  = nni_sub_sock_setopt,
	.sock_getopt  = nni_sub_sock_getopt,
	.sock_rfilter = nni_sub_sock_rfilter,
};

nni_proto nni_sub_proto = {
	.proto_self     = NNG_PROTO_SUB,
	.proto_peer     = NNG_PROTO_PUB,
	.proto_name     = "sub",
	.proto_flags    = NNI_PROTO_FLAG_RCV,
	.proto_sock_ops = &nni_sub_sock_ops,
	.proto_pipe_ops = &nni_sub_pipe_ops,
};