/* 
   SSSD

   Service monitor

   Copyright (C) Simo Sorce			2008

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <time.h>
#include "../events/events.h"
#include "util/util.h"
#include "service.h"
#include "confdb/confdb.h"
#include "monitor.h"
#include "dbus/dbus.h"
#include "sbus/sssd_dbus.h"
#include "sbus_interfaces.h"

/* ping time cannot be less then once every few seconds or the
 * monitor will get crazy hammering children with messages */
#define MONITOR_MIN_PING_TIME 2

struct mt_conn {
    struct sbus_conn_ctx *conn_ctx;
    struct mt_svc *svc_ptr;
};

struct mt_svc {
    struct mt_svc *prev;
    struct mt_svc *next;

    struct mt_conn *mt_conn;
    struct mt_ctx *mt_ctx;

    const char *name;
    pid_t pid;

    int restarts;
    time_t last_restart;
    time_t last_pong;
};

struct mt_ctx {
    struct event_context *ev;
    struct confdb_ctx *cdb;
    char **services;
    struct mt_svc *svc_list;

    int service_id_timeout;
    int service_ping_time;
};

static int dbus_service_init(struct sbus_conn_ctx *conn_ctx, void *data);
static void identity_check(DBusPendingCall *pending, void *data);

static int service_send_ping(struct mt_svc *svc);
static void ping_check(DBusPendingCall *pending, void *data);

static int service_check_alive(struct mt_svc *svc);

static void set_tasks_checker(struct mt_svc *srv);

/* dbus_get_monitor_version
 * Return the monitor version over D-BUS */
static int dbus_get_monitor_version(DBusMessage *message,
                                    void *data,
                                    DBusMessage **r)
{
    const char *version = MONITOR_VERSION;
    DBusMessage *reply;
    dbus_bool_t ret;

    reply = dbus_message_new_method_return(message);
    ret = dbus_message_append_args(reply, DBUS_TYPE_STRING,
                                   &version, DBUS_TYPE_INVALID);

    if (!ret) {
        return EIO;
    }

    *r = reply;
    return EOK;
}

struct sbus_method monitor_methods[] = {
    { MONITOR_METHOD_VERSION, dbus_get_monitor_version},
    {NULL, NULL}
};

/* monitor_dbus_init
 * Set up the monitor service as a D-BUS Server */
static int monitor_dbus_init(struct mt_ctx *ctx)
{
    struct sbus_method_ctx *sd_ctx;
    char *sbus_address;
    int ret;

    ret = confdb_get_string(ctx->cdb, ctx,
                            "config/services/monitor", "sbusAddress",
                            DEFAULT_SBUS_ADDRESS, &sbus_address);
    if (ret != EOK) {
        return ret;
    }

    sd_ctx = talloc_zero(ctx, struct sbus_method_ctx);
    if (!sd_ctx) {
        talloc_free(sbus_address);
        return ENOMEM;
    }

    /* Set up globally-available D-BUS methods */
    sd_ctx->interface = talloc_strdup(sd_ctx, MONITOR_DBUS_INTERFACE);
    if (!sd_ctx->interface) {
        talloc_free(sbus_address);
        talloc_free(sd_ctx);
        return ENOMEM;
    }
    sd_ctx->path = talloc_strdup(sd_ctx, MONITOR_DBUS_PATH);
    if (!sd_ctx->path) {
        talloc_free(sbus_address);
        talloc_free(sd_ctx);
        return ENOMEM;
    }
    sd_ctx->methods = monitor_methods;
    sd_ctx->message_handler = NULL; /* Use the default message_handler */

    ret = sbus_new_server(ctx->ev, sd_ctx, sbus_address, dbus_service_init, ctx);

    return ret;
}

static void tasks_check_handler(struct event_context *ev,
                                struct timed_event *te,
                                struct timeval t, void *ptr)
{
    struct mt_svc *svc = talloc_get_type(ptr, struct mt_svc);
    time_t now = time(NULL);
    bool process_alive = true;
    int ret;

    ret = service_check_alive(svc);
    switch (ret) {
    case EOK:
        /* all fine */
        break;

    case ECHILD:
        DEBUG(1,("Process is stopped!\n"));
        process_alive = false;
        break;

    default:
        /* TODO: should we tear down it ? */
        DEBUG(1,("Checking for service process failed!!\n"));
        break;
    }

    if (process_alive) {
        ret = service_send_ping(svc);
        switch (ret) {
        case EOK:
            /* all fine */
            break;

        case ENXIO:
            DEBUG(1,("Connection with child not available! (yet)\n"));
            break;

        default:
            /* TODO: should we tear it down ? */
            DEBUG(1,("Sending a message to the service failed!!\n"));
            break;
        }

        if (svc->last_pong != 0) {
            if ((now - svc->last_pong) > 30) { /* TODO: get val from config */
                /* too long since we last heard of this process */
                ret = kill(svc->pid, SIGUSR1);
                if (ret != EOK) {
                    DEBUG(0,("Sending signal to child failed! Ignore and pretend child is dead.\n"));
                }
                process_alive = false;
            }
        }

    }

    if (!process_alive) {
        if (svc->last_restart != 0) {
            if ((now - svc->last_restart) > 30) { /* TODO: get val from config */
                /* it was long ago reset restart threshold */
                svc->restarts = 0;
            }
        }

        /* restart the process */
        if (svc->restarts > 3) { /* TODO: get val from config */
            DEBUG(0, ("Process [%s], definitely stopped!\n", svc->name));
            talloc_free(svc);
            return;
        }

        ret = server_service_init(svc->name, svc->mt_ctx->ev, &svc->pid);
        if (ret != EOK) {
            DEBUG(0,("Failed to restart service '%s'\n", svc->name));
            talloc_free(svc);
            return;
        }

        svc->restarts++;
        svc->last_restart = now;
        svc->last_pong = 0;
    }

    /* all fine, set up the task checker again */
    set_tasks_checker(svc);
}

static void set_tasks_checker(struct mt_svc *svc)
{
    struct timed_event *te = NULL;
    struct timeval tv;

    gettimeofday(&tv, NULL);
    tv.tv_sec += svc->mt_ctx->service_ping_time;
    tv.tv_usec = 0;
    te = event_add_timed(svc->mt_ctx->ev, svc, tv, tasks_check_handler, svc);
    if (te == NULL) {
        DEBUG(0, ("failed to add event, monitor offline for [%s]!\n",
                  svc->name));
        /* FIXME: shutdown ? */
    }
}

int get_monitor_config(struct mt_ctx *ctx)
{
    int ret;

    ret = confdb_get_int(ctx->cdb, ctx,
                         "config/services/monitor", "sbusTimeout",
                         -1, &ctx->service_id_timeout);
    if (ret != EOK) {
        return ret;
    }

    ret = confdb_get_int(ctx->cdb, ctx,
                         "config/services/monitor", "servicePingTime",
                         MONITOR_MIN_PING_TIME, &ctx->service_ping_time);
    if (ret != EOK) {
        return ret;
    }
    if (ctx->service_ping_time < MONITOR_MIN_PING_TIME)
        ctx->service_ping_time = MONITOR_MIN_PING_TIME;

    ret = confdb_get_param(ctx->cdb, ctx,
                           "config/services", "activeServices",
                           &ctx->services);

    if (ctx->services[0] == NULL) {
        DEBUG(0, ("No services configured!\n"));
        return EINVAL;
    }

    return EOK;
}

int start_monitor(TALLOC_CTX *mem_ctx,
                  struct event_context *event_ctx,
                  struct confdb_ctx *cdb)
{
    struct mt_ctx *ctx;
    struct mt_svc *svc;
    int ret, i;

    ctx = talloc_zero(mem_ctx, struct mt_ctx);
    if (!ctx) {
        DEBUG(0, ("fatal error initializing monitor!\n"));
        return ENOMEM;
    }
    ctx->ev = event_ctx;
    ctx->cdb = cdb;

    ret = get_monitor_config(ctx);
    if (ret != EOK)
        return ret;

    for (i = 0; ctx->services[i]; i++) {

        svc = talloc_zero(ctx, struct mt_svc);
        if (!svc) {
            talloc_free(ctx);
            return ENOMEM;
        }
        svc->name = ctx->services[i];
        svc->mt_ctx = ctx;

        ret = server_service_init(svc->name, event_ctx, &svc->pid);
        if (ret != EOK) {
            DEBUG(0,("Failed to start service '%s'\n", svc->name));
            talloc_free(svc);
            continue;
        }

        DLIST_ADD(ctx->svc_list, svc);

        set_tasks_checker(svc);
    }

    /* Initialize D-BUS Server
     * The monitor will act as a D-BUS server for all
     * SSSD processes */
    ret = monitor_dbus_init(ctx);
    if (ret != EOK) {
        return ret;
    }

    return EOK;
}

static int mt_conn_destructor(void *ptr)
{
    struct mt_conn *mt_conn;
    struct mt_svc *svc;

    mt_conn = talloc_get_type(ptr, struct mt_conn);
    svc = mt_conn->svc_ptr;

    /* now clear up so that the rest of the code will know there
     * is no connection attached to the service anymore */
    svc->mt_conn = NULL;

    return 0;
}

/*
 * dbus_service_init
 * This function should initiate a query to the newly connected
 * service to discover the service's identity (invoke the getIdentity
 * method on the new client). The reply callback for this request
 * should set the connection destructor appropriately.
 */
static int dbus_service_init(struct sbus_conn_ctx *conn_ctx, void *data) {
    struct mt_ctx *ctx;
    struct mt_svc *svc;
    struct mt_conn *mt_conn;
    DBusMessage *msg;
    DBusPendingCall *pending_reply;
    DBusConnection *conn;
    DBusError dbus_error;
    dbus_bool_t dbret;

    DEBUG(3, ("Initializing D-BUS Service\n"));

    ctx = talloc_get_type(data, struct mt_ctx);
    conn = sbus_get_connection(conn_ctx);
    dbus_error_init(&dbus_error);

    /* hang off this memory to the connection so that when the connection
     * is freed we can call a destructor to clear up the structure and
     * have a way to know we need to restart the service */
    mt_conn = talloc(conn_ctx, struct mt_conn);
    if (!mt_conn) {
        DEBUG(0,("Out of memory?!\n"));
        talloc_free(conn_ctx);
        return ENOMEM;
    }
    mt_conn->conn_ctx = conn_ctx;

    /* at this stage we still do not know what service is this
     * we will know only after we get its identity, so we make
     * up a temporary fake service and complete the operation
     * when we receive the reply */
    svc = talloc_zero(mt_conn, struct mt_svc);
    if (!svc) {
        talloc_free(conn_ctx);
        return ENOMEM;
    }
    svc->mt_ctx = ctx;
    svc->mt_conn = mt_conn;

    mt_conn->svc_ptr = svc;
    talloc_set_destructor((TALLOC_CTX *)mt_conn, mt_conn_destructor);

    /*
     * Set up identity request
     * This should be a well-known path and method
     * for all services
     */
    msg = dbus_message_new_method_call(NULL,
                                       SERVICE_PATH,
                                       SERVICE_INTERFACE,
                                       SERVICE_METHOD_IDENTITY);
    if (msg == NULL) {
        DEBUG(0,("Out of memory?!\n"));
        talloc_free(conn_ctx);
        return ENOMEM;
    }
    dbret = dbus_connection_send_with_reply(conn, msg, &pending_reply,
                                            ctx->service_id_timeout);
    if (!dbret) {
        /*
         * Critical Failure
         * We can't communicate on this connection
         * We'll drop it using the default destructor.
         */
        DEBUG(0, ("D-BUS send failed.\n"));
        talloc_free(conn_ctx);
        return EIO;
    }

    /* Set up the reply handler */
    dbus_pending_call_set_notify(pending_reply, identity_check, svc, NULL);
    dbus_message_unref(msg);

    return EOK;
}

static void identity_check(DBusPendingCall *pending, void *data)
{
    struct mt_svc *fake_svc;
    struct mt_svc *svc;
    struct sbus_conn_ctx *conn_ctx;
    DBusMessage *reply;
    DBusError dbus_error;
    dbus_uint16_t svc_ver;
    char *svc_name;
    dbus_bool_t ret;
    int type;

    fake_svc = talloc_get_type(data, struct mt_svc);
    conn_ctx = fake_svc->mt_conn->conn_ctx;
    dbus_error_init(&dbus_error);

    reply = dbus_pending_call_steal_reply(pending);
    if (!reply) {
        /* reply should never be null. This function shouldn't be called
         * until reply is valid or timeout has occurred. If reply is NULL
         * here, something is seriously wrong and we should bail out.
         */
        DEBUG(0, ("Serious error. A reply callback was called but no reply was received and no timeout occurred\n"));

        /* Destroy this connection */
        sbus_disconnect(conn_ctx);
        return;
    }

    type = dbus_message_get_type(reply);
    switch (type) {
    case DBUS_MESSAGE_TYPE_METHOD_RETURN:
        ret = dbus_message_get_args(reply, &dbus_error,
                                    DBUS_TYPE_STRING, &svc_name,
                                    DBUS_TYPE_UINT16, &svc_ver,
                                    DBUS_TYPE_INVALID);
        if (!ret) {
            DEBUG(1,("Failed, to parse message, killing connection\n"));
            sbus_disconnect(conn_ctx);
            return;
        }

        /* search this service in the list */
        svc = fake_svc->mt_ctx->svc_list;
        while (svc) {
            ret = strcasecmp(svc->name, svc_name);
            if (ret == 0) {
                break;
            }
            svc = svc->next;
        }
        if (!svc) {
            DEBUG(0,("Unable to find peer in list of services, killing connection!\n"));
            sbus_disconnect(conn_ctx);
            return;
        }

        /* transfer all from the fake service and get rid of it */
        fake_svc->mt_conn->svc_ptr = svc;
        svc->mt_conn = fake_svc->mt_conn;
        talloc_free(fake_svc);

        /* Set up the destructor for this service */
        break;

    case DBUS_MESSAGE_TYPE_ERROR:
        DEBUG(0,("getIdentity returned an error [%s], closing connection.\n",
                 dbus_message_get_error_name(reply)));
        /* Falling through to default intentionally*/
    default:
        /*
         * Timeout or other error occurred or something
         * unexpected happened.
         * It doesn't matter which, because either way we
         * know that this connection isn't trustworthy.
         * We'll destroy it now.
         */
        sbus_disconnect(conn_ctx);
        return;
    }
}

/* service_send_ping
 * this function send a dbus ping to a service.
 * It returns EOK if all is fine or ENXIO if the connection is
 * not available (either not yet set up or teared down).
 * Returns e generic error in other cases.
 */
static int service_send_ping(struct mt_svc *svc)
{
    DBusMessage *msg;
    DBusPendingCall *pending_reply;
    DBusConnection *conn;
    DBusError dbus_error;
    dbus_bool_t dbret;

    if (!svc->mt_conn) {
        return ENXIO;
    }

    conn = sbus_get_connection(svc->mt_conn->conn_ctx);
    dbus_error_init(&dbus_error);

    /*
     * Set up identity request
     * This should be a well-known path and method
     * for all services
     */
    msg = dbus_message_new_method_call(NULL,
                                       SERVICE_PATH,
                                       SERVICE_INTERFACE,
                                       SERVICE_METHOD_PING);
    if (!msg) {
        DEBUG(0,("Out of memory?!\n"));
        talloc_free(svc->mt_conn->conn_ctx);
        return ENOMEM;
    }

    dbret = dbus_connection_send_with_reply(conn, msg, &pending_reply,
                                            svc->mt_ctx->service_id_timeout);
    if (!dbret) {
        /*
         * Critical Failure
         * We can't communicate on this connection
         * We'll drop it using the default destructor.
         */
        DEBUG(0, ("D-BUS send failed.\n"));
        talloc_free(svc->mt_conn->conn_ctx);
        return EIO;
    }

    /* Set up the reply handler */
    dbus_pending_call_set_notify(pending_reply, ping_check, svc, NULL);
    dbus_message_unref(msg);

    return EOK;
}

static void ping_check(DBusPendingCall *pending, void *data)
{
    struct mt_svc *svc;
    struct sbus_conn_ctx *conn_ctx;
    DBusMessage *reply;
    DBusError dbus_error;
    const char *dbus_error_name;
    int type;

    svc = talloc_get_type(data, struct mt_svc);
    conn_ctx = svc->mt_conn->conn_ctx;
    dbus_error_init(&dbus_error);

    reply = dbus_pending_call_steal_reply(pending);
    if (!reply) {
        /* reply should never be null. This function shouldn't be called
         * until reply is valid or timeout has occurred. If reply is NULL
         * here, something is seriously wrong and we should bail out.
         */
        DEBUG(0, ("A reply callback was called but no reply was received"
                  " and no timeout occurred\n"));

        /* Destroy this connection */
        sbus_disconnect(conn_ctx);
        return;
    }

    type = dbus_message_get_type(reply);
    switch (type) {
    case DBUS_MESSAGE_TYPE_METHOD_RETURN:
        /* ok peer replied,
         * set the reply timestamp into the service structure */

        svc->last_pong = time(NULL);
        break;

    case DBUS_MESSAGE_TYPE_ERROR:

        dbus_error_name = dbus_message_get_error_name(reply);

        /* timeouts are handled in the main service check function */
        if (strcmp(dbus_error_name, DBUS_ERROR_TIMEOUT) == 0)
            break;

        DEBUG(0,("A service PING returned an error [%s], closing connection.\n",
                 dbus_error_name));
        /* Falling through to default intentionally*/
    default:
        /*
         * Timeout or other error occurred or something
         * unexpected happened.
         * It doesn't matter which, because either way we
         * know that this connection isn't trustworthy.
         * We'll destroy it now.
         */
        sbus_disconnect(conn_ctx);
        return;
    }
}

/* service_check_alive
 * This function checks if the service child is still alive
 */
static int service_check_alive(struct mt_svc *svc)
{
    int status;
    pid_t pid;

    pid = waitpid(svc->pid, &status, WNOHANG);
    if (pid == 0) {
        return EOK;
    }

    if (pid != svc->pid) {
        DEBUG(1, ("bad return (%d) from waitpid() waiting for %d\n",
                  pid, svc->pid));
        /* TODO: what do we do now ? */
        return EINVAL;
    }

    if (WIFEXITED(status)) { /* children exited on it's own */
        /* TODO: check configuration to see if it was removed
         * from the list of process to run */
        DEBUG(0,("Process [%s] exited\n", svc->name));
    }

    return ECHILD;
}