#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <errno.h>

#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>

#include "configfile.h"
#include "event.h"
#include "linebuffer.h"
#include "list.h"
#include "logging.h"
#include "rrdtool.h"

#define MAX_PORT_VALUES		8
#define MAX_RRD_DEFINE_SIZE	512
#define MAX_RRD_RESULT_SIZE	128

struct sw_porttype {
	struct list_head	list;				// global list of sw_porttype(s)
	const char		*name;				// "es2024port"

	const char		*oid_base[MAX_PORT_VALUES];	// "IF-MIB::IfInOctets"
	int			value_count;			// number of snmp values
	struct lbuf		*rrd_definition;		// rrd/rra definition
};

struct sw_port {
	struct list_head	list;				// per sw_hosttype list of sw_port(s)
	const char		*name;				// "port01"

	struct sw_porttype	*porttype;
	const char		*oid_ext;			// "1"
};

struct sw_hosttype {
	struct list_head	list;				// global list of sw_hosttype(s)
	const char		*name;				// "es2024"

	struct list_head	ports;				// list of sw_port(s)
	int			port_count;			// number of ports
};

struct sw_host {
	struct list_head	list;				// global list of sw_host(s)
	const char		*name;				// "router01"

	struct sw_hosttype	*hosttype;

	int			active;
	struct sw_port		*current_port;			// current port
	int			current_value;			// current value/oid

	struct lbuf		*result;

	struct snmp_session	*session;			// snmp private data
};


static int snmp_interval;

static LIST_HEAD(porttype_list);
static LIST_HEAD(hosttype_list);
static LIST_HEAD(host_list);

static void log_snmp_error(struct snmp_session *session, const char *prefix)
{
//	char *snmp_error_str = NULL;
//	snmp_perror("read_objid");
//	snmp_error(session, &errno, &snmp_errno, &snmp_error_str);
	log_print(LOG_INFO, "%s: '%s'", prefix, snmp_api_errstring(snmp_errno));
	snmp_errno = 0;
}

int snmp_pre_select_cb(int *maxfd, void *readfds, void *writefds, struct timeval *timeout, void *privdata)
{
	int block = 1;

	snmp_select_info(maxfd, (fd_set *)readfds, timeout, &block);
	return 0;
}

int snmp_post_select_cb(int retval, void *readfds, void *writefds, void *privdata)
{
	if (retval != 0) {
		snmp_read((fd_set *)readfds);

	} else {
		snmp_timeout();
	}

	return 0;
}

static int add_portvalue_cb(const char *parameter, void *privdata)
{
	struct sw_porttype *porttype = (struct sw_porttype *)privdata;

	struct strtoken *tokens = strtokenize(parameter, ",", 2);
	if (tokens == NULL) {
		log_print(LOG_ERROR, "add_portvalue_cb(): out of memory(1)");
		return 1;
	}

	if (tokens->count != 2) {
		log_print(LOG_ERROR, "add_portvalue_cb(): invalid value line");
		free(tokens);
		return 1;
	}

	if (porttype->value_count < MAX_PORT_VALUES -1) {
		porttype->oid_base[porttype->value_count++] = strdup(tokens->field[0]);

	} else {
		log_print(LOG_WARN, "add_portvalue_cb(): too many oids for %s", porttype->name);
		free(tokens);
		return 1;
	}

	if (lbuf_printf(porttype->rrd_definition, "%s ", tokens->field[1]) < 0) {
		log_print(LOG_WARN, "add_portvalue_cb(): truncated rrd definition for %s", porttype->name);
		free(tokens);
		return 1;
	}

	free(tokens);
	return 0;
}

static int add_portdef_cb(const char *parameter, void *privdata)
{
	struct sw_porttype *porttype = (struct sw_porttype *)privdata;

	if (lbuf_printf(porttype->rrd_definition, "%s ", parameter) < 0) {
		log_print(LOG_WARN, "add_portdef_cb(): truncated rrd definition for %s", porttype->name);
		return 1;
	}

	return 0;
}

static int add_porttype_cb(const char *parameter, void *privdata)
{
	struct sw_porttype *porttype = malloc(sizeof(struct sw_porttype));
	if (porttype == NULL) {
		log_print(LOG_WARN, "add_porttype_cb(): out of memory");
		return 1;
	}

	memset(porttype, 0, sizeof(struct sw_porttype));
	porttype->name = strdup(parameter);
	porttype->rrd_definition = lbuf_create(MAX_RRD_DEFINE_SIZE);

	char section[32];
	snprintf(section, sizeof(section), "porttype_%s", parameter);
	config_get_strings(section, "value", add_portvalue_cb, (void *)porttype);

	config_get_strings(section, "rra", add_portdef_cb, (void *)porttype);

	if (porttype->value_count > 0) {
		list_add_tail(&porttype->list, &porttype_list);
		log_print(LOG_INFO, "adding porttype '%s' with %d snmp values", porttype->name, porttype->value_count);

	} else {
		lbuf_free(porttype->rrd_definition);
		free((char *)porttype->name);
		free(porttype);
	}

	return 0;
}

static struct sw_porttype * find_porttype_by_name(const char *name)
{
	struct sw_porttype *porttype;

	list_for_each_entry(porttype, &porttype_list, list) {
		if (strcmp(porttype->name, name) == 0)
			return porttype;
	}

	return NULL;
}

static int add_port_cb(const char *parameter, void *privdata)
{
	struct sw_hosttype *hosttype = (struct sw_hosttype *)privdata;

	struct strtoken *tokens = strtokenize(parameter, ",", 3);
	if (tokens == NULL) {
		log_print(LOG_ERROR, "add_port_cb(): out of memory(1)");
		return 1;
	}

	if (tokens->count != 3) {
		log_print(LOG_ERROR, "add_port_cb(): invalid port line");
		free(tokens);
		return 1;
	}

	struct sw_port *port = malloc(sizeof(struct sw_port));
	if (port == NULL) {
		log_print(LOG_WARN, "add_port_cb(): out of memory(2)");
		free(tokens);
		return 1;
	}

	port->porttype = find_porttype_by_name(tokens->field[1]);
	if (port->porttype == NULL) {
		log_print(LOG_WARN, "add_port_cb(): invalid porttype '%s'", tokens->field[1]);
		free(port);
		free(tokens);
		return 1;
	}

	port->name = strdup(tokens->field[0]);
	port->oid_ext = strdup(tokens->field[2]);

	list_add_tail(&port->list, &hosttype->ports);
	hosttype->port_count++;

	free(tokens);
	return 0;
}

static int add_hosttype_cb(const char *parameter, void *privdata)
{
	struct sw_hosttype *hosttype = malloc(sizeof(struct sw_hosttype));
	if (hosttype == NULL) {
		log_print(LOG_WARN, "add_hosttype_cb(): out of memory");
		return 1;
	}

	memset(hosttype, 0, sizeof(struct sw_hosttype));
	hosttype->name = strdup(parameter);
	INIT_LIST_HEAD(&hosttype->ports);

	char section[32];
	snprintf(section, sizeof(section), "hosttype_%s", parameter);
	config_get_strings(section, "port", add_port_cb, (void *)hosttype);

	if (hosttype->port_count > 0) {
		list_add_tail(&hosttype->list, &hosttype_list);
		log_print(LOG_INFO, "adding hosttype '%s' with %d ports", hosttype->name, hosttype->port_count);

	} else {
		free((char *)hosttype->name);
		free(hosttype);
	}

	return 0;
}

static struct sw_hosttype * find_hosttype_by_name(const char *name)
{
	struct sw_hosttype *hosttype;

	list_for_each_entry(hosttype, &hosttype_list, list) {
		if (strcmp(hosttype->name, name) == 0)
			return hosttype;
	}

	return NULL;
}

static int snmp_async_cb(int operation, struct snmp_session *sp, int reqid, struct snmp_pdu *pdu, void *magic);

static int add_host_cb(const char *parameter, void *privdata)
{
	struct strtoken *tokens = strtokenize(parameter, ",", 4);
	if (tokens == NULL) {
		log_print(LOG_ERROR, "add_host_cb(): out of memory(1)");
		return 1;
	}

	if (tokens->count != 4) {
		log_print(LOG_ERROR, "add_host_cb(): invalid host line");
		return 1;
	}

	struct sw_host *host = malloc(sizeof(struct sw_host));
	if (host == NULL) {
		log_print(LOG_ERROR, "add_host_cb(): out of memory(2)");
		free(tokens);
		return 1;
	}

	host->hosttype = find_hosttype_by_name(tokens->field[1]);
	if (host->hosttype == NULL) {
		log_print(LOG_ERROR, "add_host_cb(): invalid hosttype '%s'", tokens->field[1]);
		free(host);
		free(tokens);
		return 1;
	}

	host->result = lbuf_create(MAX_RRD_RESULT_SIZE);
	if (host->result == NULL) {
		log_print(LOG_ERROR, "add_host_cb(): out of memory(3)");
		free(host);
		free(tokens);
		return 1;
	}

	host->name = strdup(tokens->field[0]);

	struct snmp_session sess;
	snmp_sess_init(&sess);
	sess.version		= SNMP_VERSION_2c;
	sess.peername		= strdup(tokens->field[2]);
	sess.community		= (unsigned char *)strdup(tokens->field[3]);
	sess.community_len	= strlen((char *)sess.community);
	sess.callback		= snmp_async_cb;
	sess.callback_magic	= host;

	if ((host->session = snmp_open(&sess)) == NULL) {
		log_snmp_error(&sess, "add_host_cb(): snmp_open()");
		free((char *)sess.community);
		free((char *)host->name);
		lbuf_free(host->result);
		free(host->hosttype);
		free(host);
		free(tokens);
		return 1;
	}

	host->active = 0;
	host->current_port = NULL;
	host->current_value = 0;

	log_print(LOG_INFO, "adding host %s", host->session->peername);
	list_add_tail(&host->list, &host_list);

	free((char *)sess.community);
	return 0;
}

static int do_snmp_poll(void *privdata);

int snmp_init(void)
{
	init_snmp("snmp2rrd");
	errno = 0;

	config_get_strings("global", "porttype", add_porttype_cb, NULL);
	config_get_strings("global", "hosttype", add_hosttype_cb, NULL);
	config_get_strings("global", "host", add_host_cb, NULL);

	config_get_int("global", "interval", &snmp_interval, 60);

	struct timeval tv_interval = {
		.tv_sec = snmp_interval,
		.tv_usec = 0,
	};

	event_add_timeout(&tv_interval, do_snmp_poll, NULL);
	do_snmp_poll(NULL);

	return 0;
}

static int send_next_request(struct sw_host *host)
{
	/* first port */
	if (host->current_port == NULL) {
		host->current_port = list_entry(host->hosttype->ports.next, struct sw_port, list);
		host->current_value = 0;

		// use "Now" as timespec in RRD commit
		lbuf_clear(host->result);
		lbuf_printf(host->result, "N");

	} else {
		host->current_value++;
		if (host->current_value >= host->current_port->porttype->value_count) {

			char filename[64];
			snprintf(filename, sizeof(filename), "%s/%s.rrd", host->name, host->current_port->name);
			char *rrd_definition = lbuf_getdata(host->current_port->porttype->rrd_definition, NULL);
			char *result = lbuf_getdata(host->result, NULL);
			rrd_submit(filename, rrd_definition, snmp_interval, result);
//			log_print(LOG_INFO, "%s %s %d %s", filename, rrd_definition, snmp_interval, result);

			// check if this is the last port
			if (host->current_port->list.next == &host->hosttype->ports) {
				host->current_port = NULL;
				host->active = 0;
				return -1;
			}

			// get next port
			host->current_port = list_entry(host->current_port->list.next, struct sw_port, list);
			host->current_value = 0;

			// use "Now" as timespec in RRD commit
			lbuf_clear(host->result);
			lbuf_printf(host->result, "N");
		}
	}

	char buf[128];
	snprintf(buf, sizeof(buf), "%s.%s", host->current_port->porttype->oid_base[host->current_value], host->current_port->oid_ext);

//	log_print(LOG_INFO, "polling: %-10s %-6s %2d => %s", host->name, host->current_port->name, host->current_value, buf);

	oid oidx[MAX_OID_LEN];
	size_t oid_len = MAX_OID_LEN;

	if (!read_objid(buf, oidx, &oid_len)) {
		log_snmp_error(host->session, "send_next_request(): read_objid()");
		return -1;
	}

	struct snmp_pdu *req = snmp_pdu_create(SNMP_MSG_GET);
	snmp_add_null_var(req, oidx, oid_len);

	if (!snmp_send(host->session, req)) {
		log_snmp_error(host->session, "send_next_request(): read_objid()");
		snmp_free_pdu(req);
		return -1;
	}

	return 0;
}

static const char * snmp_get_op_str(int operation)
{
	switch (operation) {
		case NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE:	return "OP_RECEIVED_MESSAGE";
		case NETSNMP_CALLBACK_OP_TIMED_OUT:		return "OP_TIMED_OUT";
		case NETSNMP_CALLBACK_OP_SEND_FAILED:		return "OP_SEND_FAILED";
		case NETSNMP_CALLBACK_OP_CONNECT:		return "OP_CONNECT";
		case NETSNMP_CALLBACK_OP_DISCONNECT:		return "OP_DISCONNECT";
		default:					return "<unknown>";
	}
}

static int snmp_async_cb(int operation, struct snmp_session *sp, int reqid, struct snmp_pdu *pdu, void *magic)
{
	struct sw_host *host = (struct sw_host *)magic;

	if (operation == NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE) {

		struct variable_list *vp = pdu->variables;

		if (pdu->errstat == SNMP_ERR_NOERROR) {
//			print_variable(vp->name, vp->name_length, vp);

			switch (vp->type) {
				case ASN_GAUGE:
				case ASN_COUNTER:
					lbuf_printf(host->result, ":%d", *vp->val.integer);
					break;

				case ASN_COUNTER64:
					lbuf_printf(host->result, ":%lld", (uint64_t)vp->val.counter64->high * 0x100000000ULL + (uint64_t)vp->val.counter64->low);
					break;

				default:
					lbuf_printf(host->result, ":U");
					break;
			}

		} else {
			lbuf_printf(host->result, ":U");
		}

	} else if (operation == NETSNMP_CALLBACK_OP_TIMED_OUT) {
		log_print(LOG_WARN, "snmp_async_cb(%s): on host %s", snmp_get_op_str(operation), host->name);
		host->current_port = NULL;
		host->active = 0;

	} else {
		log_print(LOG_WARN, "snmp_async_cb(%s) on host %s", snmp_get_op_str(operation), host->name);
	}

	if (host->active)
		send_next_request(host);

	return 1;
}

static int do_snmp_poll(void *privdata)
{
	struct sw_host *host;

	list_for_each_entry(host, &host_list, list) {
		if (host->active) {
			log_print(LOG_WARN, "host '%s' still active", host->name);
			continue;
		}

		host->active = 1;
		send_next_request(host);
	}

	return 0;
}