/*-
 * Copyright (c) 2014 Luiz Otavio O Souza <loos@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/queue.h>
#include <sys/sysctl.h>

#include <bsnmp/snmpmod.h>

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

#include "lm75_oid.h"
#include "lm75_tree.h"

#ifndef LM75BUF
#define LM75BUF         64
#endif
#define TZ_ZEROC        2732
#define UPDATE_INTERVAL 500     /* update interval in ticks */

static struct lmodule *module;

static const struct asn_oid oid_lm75 = OIDX_begemotLm75;

/* the Object Resource registration index */
static u_int lm75_index = 0;

/* Number of available sensors in the system. */
static int lm75_sensors;

/*
 * Structure that describes single sensor.
 */
struct lm75_snmp_sensor {
        TAILQ_ENTRY(lm75_snmp_sensor) link;
        int32_t         index;
        int32_t         sysctlidx;
        int32_t         temp;
        char            desc[LM75BUF];
        char            location[LM75BUF];
        char            parent[LM75BUF];
        char            pnpinfo[LM75BUF];
};

static TAILQ_HEAD(, lm75_snmp_sensor) sensors =
    TAILQ_HEAD_INITIALIZER(sensors);

/* Ticks of the last sensors reading. */
static uint64_t last_sensors_update;

static void free_sensors(void);
static int lm75_fini(void);
static int lm75_init(struct lmodule *mod, int argc, char *argv[]);
static void lm75_start(void);
static int update_sensors(void);

const struct snmp_module config = {
    .comment   =
        "This module implements the BEGEMOT MIB for reading LM75 sensors data.",
    .init      = lm75_init,
    .start     = lm75_start,
    .fini      = lm75_fini,
    .tree      = lm75_ctree,
    .tree_size = lm75_CTREE_SIZE,
};

static int
lm75_init(struct lmodule *mod, int argc __unused, char *argv[] __unused)
{

        module = mod;

        lm75_sensors = 0;

        return(0);
}

static void
lm75_start(void)
{

        lm75_index = or_register(&oid_lm75,
            "The MIB module for reading lm75 sensors data.", module);
}

static int
lm75_fini(void)
{

        or_unregister(lm75_index);
        free_sensors();
        closelog();

        return (0);
}

static void
free_sensors(void)
{
        struct lm75_snmp_sensor *sensor;

        while ((sensor = TAILQ_FIRST(&sensors)) != NULL) {
                TAILQ_REMOVE(&sensors, sensor, link);
                free(sensor);
        }
}

static int
sysctlname(int *oid, int nlen, char *name, size_t len)
{
        int mib[12];

        if (nlen > (int)(sizeof(mib) / sizeof(int) - 2))
                return (-1);

        mib[0] = 0;
        mib[1] = 1;
        memcpy(mib + 2, oid, nlen * sizeof(int));

        if (sysctl(mib, nlen + 2, name, &len, 0, 0) == -1)
                return (-1);

        return (0);
}

static int
sysctlgetnext(int *oid, int nlen, int *next, size_t *nextlen)
{
        int mib[12];

        if (nlen > (int)(sizeof(mib) / sizeof(int) - 2))
                return (-1);

        mib[0] = 0;
        mib[1] = 2;
        memcpy(mib + 2, oid, nlen * sizeof(int));

        if (sysctl(mib, nlen + 2, next, nextlen, 0, 0) == -1)
                return (-1);

        return (0);
}

static int
update_sensor_sysctl(void *obuf, size_t *obuflen, int idx, const char *name)
{
        char buf[LM75BUF];
        int mib[5];
        size_t len;

        /* Fill out the mib information. */
        snprintf(buf, sizeof(buf) - 1, "dev.lm75.%d.%s", idx, name);
        len = sizeof(mib) / sizeof(int);
        if (sysctlnametomib(buf, mib, &len) == -1)
                return (-1);

        if (len != 4)
                return (-1);

        /* Read the sysctl data. */
        if (sysctl(mib, len, obuf, obuflen, NULL, 0) == -1)
                return (-1);

        return (0);
}

static void
update_sensor(struct lm75_snmp_sensor *sensor, int idx)
{
        size_t len;

        len = sizeof(sensor->desc);
        update_sensor_sysctl(sensor->desc, &len, idx, "%desc");

        len = sizeof(sensor->location);
        update_sensor_sysctl(sensor->location, &len, idx, "%location");

        len = sizeof(sensor->pnpinfo);
        update_sensor_sysctl(sensor->pnpinfo, &len, idx, "%pnpinfo");

        len = sizeof(sensor->parent);
        update_sensor_sysctl(sensor->parent, &len, idx, "%parent");
}

static int
add_sensor(char *buf)
{
        int idx, temp;
        size_t len;
        struct lm75_snmp_sensor *sensor;

        if (sscanf(buf, "dev.lm75.%d.temperature", &idx) != 1)
                return (-1);

        /* Read the sensor temperature. */
        len = sizeof(temp);
        if (update_sensor_sysctl(&temp, &len, idx, "temperature") != 0)
                return (-1);

        /* Add the sensor data to the table. */
        sensor = calloc(1, sizeof(*sensor));
        if (sensor == NULL) {
                syslog(LOG_ERR, "Unable to allocate %zu bytes for resource",
                    sizeof(*sensor));
                return (-1);
        }
        sensor->index = ++lm75_sensors;
        sensor->sysctlidx = idx;
        sensor->temp = (temp - TZ_ZEROC) / 10;
        TAILQ_INSERT_TAIL(&sensors, sensor, link);

        update_sensor(sensor, idx);

        return (0);
}

static int
update_sensors(void)
{
        char buf[LM75BUF];
        int i, root[5], *next, *oid;
        size_t len, nextlen, rootlen;
        static uint64_t now;

        now = get_ticks();
        if (now - last_sensors_update < UPDATE_INTERVAL)
                return (0);

        last_sensors_update = now;

        /* Reset the sensor data. */
        free_sensors();
        lm75_sensors = 0;

        /* Start from the lm75 default root node. */
        rootlen = 2;
        if (sysctlnametomib("dev.lm75", root, &rootlen) == -1)
                return (0);

        oid = (int *)malloc(sizeof(int) * rootlen);
        if (oid == NULL) {
                perror("malloc");
                return (-1);
        }
        memcpy(oid, root, rootlen * sizeof(int));
        len = rootlen;

        /* Traverse the sysctl(3) interface and find the active sensors. */
        for (;;) {

                /* Find the size of the next mib. */
                nextlen = 0;
                if (sysctlgetnext(oid, len, NULL, &nextlen) == -1) {
                        free(oid);
                        return (0);
                }
                /* Allocate and read the next mib. */
                next = (int *)malloc(nextlen);
                if (next == NULL) {
                        syslog(LOG_ERR,
                            "Unable to allocate %zu bytes for resource",
                            nextlen);
                        free(oid);
                        return (-1);
                }
                if (sysctlgetnext(oid, len, next, &nextlen) == -1) {
                        free(oid);
                        free(next);
                        return (0);
                }
                free(oid);
                /* Check if we care about the next mib. */
                for (i = 0; i < (int)rootlen; i++)
                        if (next[i] != root[i]) {
                                free(next);
                                return (0);
                        }
                oid = (int *)malloc(nextlen);
                if (oid == NULL) {
                        syslog(LOG_ERR,
                            "Unable to allocate %zu bytes for resource",
                            nextlen);
                        free(next);
                        return (-1);
                }
                memcpy(oid, next, nextlen);
                free(next);
                len = nextlen / sizeof(int);

                /* Find the mib name. */
                if (sysctlname(oid, len, buf, sizeof(buf)) != 0)
                        continue;

                if (strstr(buf, "temperature"))
                        if (add_sensor(buf) != 0) {
                                free(oid);
                                return (-1);
                        }
        }

        return (0);
}

int
op_lm75Sensors(struct snmp_context *context __unused, struct snmp_value *value,
    u_int sub, u_int iidx __unused, enum snmp_op op)
{
        asn_subid_t which;

        if (update_sensors() == -1)
                return (SNMP_ERR_RES_UNAVAIL);

        which = value->var.subs[sub - 1];

        switch (op) {
        case SNMP_OP_GET:
                switch (which) {
                case LEAF_lm75Sensors:
                        value->v.integer = lm75_sensors;
                        break;
                default:
                        return (SNMP_ERR_RES_UNAVAIL);
                }
                break;
        case SNMP_OP_SET:
                return (SNMP_ERR_NOT_WRITEABLE);
        case SNMP_OP_GETNEXT:
        case SNMP_OP_ROLLBACK:
        case SNMP_OP_COMMIT:
                return (SNMP_ERR_NOERROR);
        default:
                return (SNMP_ERR_RES_UNAVAIL);
        }

        return (SNMP_ERR_NOERROR);
}

int
op_lm75SensorTable(struct snmp_context *context __unused,
    struct snmp_value *value, u_int sub, u_int iidx __unused, enum snmp_op op)
{
        struct lm75_snmp_sensor *sensor;
        asn_subid_t which;
        int ret;

        if (update_sensors() == -1)
                return (SNMP_ERR_RES_UNAVAIL);

        which = value->var.subs[sub - 1];

        switch (op) {
        case SNMP_OP_GETNEXT:
                sensor = NEXT_OBJECT_INT(&sensors, &value->var, sub);
                if (sensor == NULL)
                        return (SNMP_ERR_NOSUCHNAME);
                value->var.len = sub + 1;
                value->var.subs[sub] = sensor->index;
                break;
        case SNMP_OP_GET:
                if (value->var.len - sub != 1)
                        return (SNMP_ERR_NOSUCHNAME);
                sensor = FIND_OBJECT_INT(&sensors, &value->var, sub);
                if (sensor == NULL)
                        return (SNMP_ERR_NOSUCHNAME);
                break;
        case SNMP_OP_SET:
                return (SNMP_ERR_NOT_WRITEABLE);
        case SNMP_OP_ROLLBACK:
        case SNMP_OP_COMMIT:
                return (SNMP_ERR_NOERROR);
        default:
                return (SNMP_ERR_RES_UNAVAIL);
        }

        ret = SNMP_ERR_NOERROR;

        switch (which) {
        case LEAF_lm75SensorIndex:
                value->v.integer = sensor->index;
                break;
        case LEAF_lm75SensorSysctlIndex:
                value->v.integer = sensor->sysctlidx;
                break;
        case LEAF_lm75SensorDesc:
                ret = string_get(value, sensor->desc, -1);
                break;
        case LEAF_lm75SensorLocation:
                ret = string_get(value, sensor->location, -1);
                break;
        case LEAF_lm75SensorPnpInfo:
                ret = string_get(value, sensor->pnpinfo, -1);
                break;
        case LEAF_lm75SensorParent:
                ret = string_get(value, sensor->parent, -1);
                break;
        case LEAF_lm75SensorTemperature:
                value->v.integer = sensor->temp;
                break;
        default:
                ret = SNMP_ERR_RES_UNAVAIL;
                break;
        }

        return (ret);
}