/*
 * server.c - Each SiriDB database has at least one server.
 */
#include <assert.h>
#include <logger/logger.h>
#include <procinfo/procinfo.h>
#include <siri/db/query.h>
#include <siri/db/server.h>
#include <siri/db/servers.h>
#include <siri/db/fifo.h>
#include <siri/db/tee.h>
#include <siri/err.h>
#include <siri/net/promise.h>
#include <siri/net/stream.h>
#include <siri/net/tcp.h>
#include <siri/siri.h>
#include <siri/version.h>
#include <xstr/xstr.h>
#include <string.h>

#define SIRIDB_SERVERS_FN "servers.dat"
#define SIRIDB_SERVERS_SCHEMA 1
#define SIRIDB_SERVER_FLAGS_TIMEOUT 5000        /* 5 seconds    */
#define SIRIDB_SERVER_PROMISES_QUEUE_SIZE 250   /* max concurrent promises  */
#define FMT_AS_IPV6(addr) (strchr(addr, ':') != NULL)

static int SERVER_update_name(siridb_server_t * server);
static void SERVER_timeout_pkg(uv_timer_t * handle);
static void SERVER_write_cb(uv_write_t * req, int status);
static void SERVER_on_auth_response(
        sirinet_promise_t * promise,
        sirinet_pkg_t * pkg,
        int status);
static void SERVER_on_flags_update_response(
        sirinet_promise_t * promise,
        sirinet_pkg_t * pkg,
        int status);
static void SERVER_on_connect(uv_connect_t * req, int status);
static void SERVER_on_resolved(
        uv_getaddrinfo_t * resolver,
        int status,
        struct addrinfo * res);
static int SERVER_resolve_dns(
        siridb_server_t * server,
        int ai_family,
        uv_getaddrinfo_cb getaddrinfo_cb);
static void SERVER_on_data(sirinet_stream_t * client, sirinet_pkg_t * pkg);
static void SERVER_cancel_promise(sirinet_promise_t * promise);
static void SERVER_upd_flag_queue_full(siridb_server_t * server);

/*
 * In case of an error the return value is NULL and a SIGNAL is raised.
 */
siridb_server_t * siridb_server_new(
        const char * uuid,
        const char * address,
        size_t address_len,
        uint16_t port,
        uint16_t pool)
{
    siridb_server_t * server = malloc(sizeof(siridb_server_t));
    if (server == NULL)
    {
        ERR_ALLOC
        return NULL;
    }
    /* copy uuid */
    memcpy(server->uuid, uuid, 16);

    /* initialize with NULL, SERVER_update_name() sets the correct name */
    server->name = NULL;

    /* copy address */
    server->address = strndup(address, address_len);
    if (server->address == NULL)
    {
        ERR_ALLOC
        free(server);
        return NULL;
    }

    server->port = port;
    server->pool = pool;
    server->flags = 0;
    server->id = 255;
    server->ref = 0;
    server->pid = 0;
    server->version = NULL;
    server->ip_support = 255; /* unknown */
    server->retry_attempts = 0;
    server->libuv = NULL;
    server->dbpath = NULL;
    server->buffer_path = NULL;
    server->buffer_size = 0;
    server->startup_time = 0;

    /* we set the promises later because we don't need one for self */
    server->promises = NULL;
    server->client = NULL;

    /* sets address:port to name property */
    if (SERVER_update_name(server))
    {
        ERR_ALLOC
        siridb__server_free(server);
        server = NULL;
    }

    return server;
}

/*
 * This function can return -1 and raise a SIGNAL which means the 'cb'
 * function will NOT be called. Usually this function should return 0 which
 * means that we try to send the package and the 'cb' function can be checked
 * for the result.
 *
 * Note that 'pkg->pid' will be overwritten with a new package id.
 *
 * (default timeout PROMISE_DEFAULT_TIMEOUT is used when timeout 0 is set)
 *
 */
int siridb_server_send_pkg(
        siridb_server_t * server,
        sirinet_pkg_t * pkg,
        uint64_t timeout,
        sirinet_promise_cb cb,
        void * data,
        int flags)
{
    assert (server->client != NULL);
    assert (server->promises != NULL);
    assert (cb != NULL);
    int rc;
    uint8_t n = 0;
    sirinet_promise_t * promise = malloc(sizeof(sirinet_promise_t));
    if (promise == NULL)
    {
        ERR_ALLOC
        return -1;
    }

    promise->timer = malloc(sizeof(uv_timer_t));
    if (promise->timer == NULL)
    {
        ERR_ALLOC
        free(promise);
        return -1;
    }
    promise->timer->data = promise;
    promise->cb = cb;
    promise->pkg = (flags & FLAG_KEEP_PKG) ? NULL : pkg;
    promise->ref = 2;
    /*
     * we do not need to increment the server reference counter since promises
     * will be destroyed before the server is destroyed.
     */
    promise->server = server;
    promise->data = data;

    uv_write_t * req = malloc(sizeof(uv_write_t));
    if (req == NULL)
    {
        ERR_ALLOC
        free(promise->timer);
        free(promise);
        return -1;
    }

    while (++n)
    {
        /*
         * Usually the first attempt is fine but in some rare case the pid
         * might still be in use and we should try another pid.
         */
        promise->pid = server->pid++;
        rc = omap_add(server->promises, promise->pid, promise);

        if (rc == OMAP_SUCCESS)
        {
            SERVER_upd_flag_queue_full(server);
            break;
        }

        if (rc == OMAP_ERR_ALLOC)
        {
            /* memory allocation error */
            free(promise->timer);
            free(promise);
            free(req);
            ERR_ALLOC
            return -1;
        }

        /* rc == OMAP_ERR_EXIST, pid in use, try next pid */
    }

    if (!n)
    {
        /*
         * The queue cannot contain more than SIRIDB_SERVER_PROMISES_QUEUE_SIZE
         * promises so we should always find a free pid and this code should
         * never be reached.
         */
        log_critical("Cannot add promise to queue for '%s'", server->name);
        ERR_C
        free(promise->timer);
        free(promise);
        free(req);
        return -1;
    }

    pkg->pid = promise->pid;

    uv_timer_init(siri.loop, promise->timer);
    uv_timer_start(
            promise->timer,
            SERVER_timeout_pkg,
            (timeout) ? timeout : PROMISE_DEFAULT_TIMEOUT,
            0);

    log_debug("Sending (pid: %" PRIu16 ", len: %" PRIu32 ", tp: %s) to '%s'",
            pkg->pid,
            pkg->len,
            sirinet_bproto_client_str(pkg->tp),
            server->name);

    req->data = promise;

    /* set the correct check bit */
    pkg->checkbit = pkg->tp ^ 255;

    uv_buf_t wrbuf = uv_buf_init(
            (char *) pkg,
            sizeof(sirinet_pkg_t) + pkg->len);

    uv_write(
            req,
            server->client->stream,
            &wrbuf,
            1,
            SERVER_write_cb);

    return 0;
}

/*
 * Register and return a new server from qpack data.
 * The qpack data should contain: [uuid, address, port, pool]
 *
 * In case of an error NULL is returned.
 * (a SIGNAL might be raised in case of allocation errors)
 */
siridb_server_t * siridb_server_register(
        siridb_t * siridb,
        unsigned char * data,
        size_t len)
{
    siridb_server_t * server = NULL;
    qp_unpacker_t unpacker;
    qp_unpacker_init(&unpacker, data, len);

    qp_obj_t qp_uuid;
    qp_obj_t qp_address;
    qp_obj_t qp_port;
    qp_obj_t qp_pool;

    if (qp_is_array(qp_next(&unpacker, NULL)) &&
        qp_next(&unpacker, &qp_uuid) == QP_RAW &&
        qp_next(&unpacker, &qp_address) == QP_RAW &&
        qp_next(&unpacker, &qp_port) == QP_INT64 &&
        qp_next(&unpacker, &qp_pool) == QP_INT64)
    {
        server = siridb_server_new(
                (const char *) qp_uuid.via.raw,
                (const char *) qp_address.via.raw,
                qp_address.len,
                qp_port.via.int64,
                qp_pool.via.int64);


        if (server != NULL)
        {
            if (    (server->promises = omap_create()) == NULL ||
                    siridb_servers_register(siridb, server))
            {
                siridb__server_free(server);
                server = NULL;
            }
        }
    }

    return server;
}

/*
 * This function can raise a SIGNAL.
 */
void siridb_server_send_flags(siridb_server_t * server)
{

    assert (server->client != NULL);
    assert (siridb_server_is_online(server));

    sirinet_stream_t * client = server->client;

    assert (client->siridb != NULL);

    int16_t n = client->siridb->server->flags;
    QP_PACK_INT16(buffer, n)

    sirinet_pkg_t * pkg = sirinet_pkg_new(0, 3, BPROTO_FLAGS_UPDATE, buffer);
    if (pkg != NULL && siridb_server_send_pkg(
            server,
            pkg,
            SIRIDB_SERVER_FLAGS_TIMEOUT,
            (sirinet_promise_cb) SERVER_on_flags_update_response,
            NULL,
            0))
    {
        free(pkg);
    }
}

/*
 * Returns 0 if successful or -1 in case of an error.
 * (a SIGNAL might be raises)
 *
 * This function only updates the address/port/name in case different from the
 * current values.
 */
int siridb_server_update_address(
        siridb_t * siridb,
        siridb_server_t * server,
        const char * address,
        uint16_t port)
{
    if (strcmp(server->address, address) || server->port != port)
    {
        char * tmp;
        tmp = strdup(address);
        if (tmp == NULL)
        {
            log_critical(
                    "Cannot set server address (memory allocation error)");
            return -1;
        }

        free(server->address);

        server->address = tmp;
        server->port = port;

        if FMT_AS_IPV6(server->address)
        {
            log_warning("Update server '%s' to '[%s]:%u'",
                    server->name,
                    server->address,
                    server->port);
        }
        else
        {
            log_warning("Update server '%s' to '%s:%u'",
                    server->name,
                    server->address,
                    server->port);
        }
        if (SERVER_update_name(server))
        {
            log_critical(
                    "Cannot rename server (memory allocation error)");
            return -1;
        }

        if (siridb_servers_save(siridb))
        {
            return -1;
        }

        return 1;
    }

    return 0;
}

/*
 * Connect to a SiriDB Server.
 */
void siridb_server_connect(siridb_t * siridb, siridb_server_t * server)
{
    /* server->socket must be NULL at this point */
    assert (server->client == NULL);

    ++server->retry_attempts;
    server->client = sirinet_stream_new(STREAM_TCP_SERVER, &SERVER_on_data);

    if (server->client != NULL)
    {
        struct in_addr sa;
        struct in6_addr sa6;
        server->client->origin = server;
        server->client->siridb = siridb;
        siridb_incref(siridb);
        siridb_server_incref(server);
        uv_tcp_init(siri.loop, (uv_tcp_t *) server->client->stream);

        if (inet_pton(AF_INET, server->address, &sa))
        {
            /* IPv4 */
            struct sockaddr_in dest;

            uv_connect_t * req = malloc(sizeof(uv_connect_t));
            if (req == NULL)
            {
                ERR_ALLOC
                sirinet_stream_decref(server->client);
            }
            else
            {
                log_debug("Trying to connect to '%s'...", server->name);
                uv_ip4_addr(server->address, server->port, &dest);
                uv_tcp_connect(
                        req,
                        (uv_tcp_t *) server->client->stream,
                        (const struct sockaddr *) &dest,
                        SERVER_on_connect);
            }
        }
        else if (inet_pton(AF_INET6, server->address, &sa6))
        {
            /* IPv6 */
            struct sockaddr_in6 dest6;

            uv_connect_t * req = malloc(sizeof(uv_connect_t));
            if (req == NULL)
            {
                ERR_ALLOC
                sirinet_stream_decref(server->client);
            }
            else
            {
                log_debug("Trying to connect to '%s'...", server->name);
                uv_ip6_addr(server->address, server->port, &dest6);
                uv_tcp_connect(
                        req,
                        (uv_tcp_t *) server->client->stream,
                        (const struct sockaddr *) &dest6,
                        SERVER_on_connect);
            }
        }
        else
        {
            /* Try DNS */
            if (SERVER_resolve_dns(
                    server,
                    dns_req_family_map(siri.cfg->ip_support),
                    SERVER_on_resolved))
            {
                sirinet_stream_decref(server->client);
            }
        }
    }
}

/*
 * Try to get an ip address from dns.
 *
 * The callback should be checked if resolving succeeded. This function should
 * return 0 when we can start an attempt. When the result is not zero, the
 * callback will not be called.
 */
static int SERVER_resolve_dns(
        siridb_server_t * server,
        int ai_family,
        uv_getaddrinfo_cb getaddrinfo_cb)
{

    struct addrinfo hints;
    hints.ai_family = ai_family;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_NUMERICSERV;

    uv_getaddrinfo_t * resolver = malloc(sizeof(uv_getaddrinfo_t));

    if (resolver == NULL)
    {
        ERR_ALLOC
        return -1;
    }

    int result;
    resolver->data = server;

    char port[6]= {'\0'};
    sprintf(port, "%u", server->port);

    result = uv_getaddrinfo(
            siri.loop,
            resolver,
            getaddrinfo_cb,
            server->address,
            port,
            &hints);

    if (result)
    {
        log_error("getaddrinfo call error %s", uv_err_name(result));
        free(resolver);
    }

    return result;
}

/*
 * Callback used to check if resolving an ip address was successful.
 */
static void SERVER_on_resolved(
        uv_getaddrinfo_t * resolver,
        int status,
        struct addrinfo * res)
{
    siridb_server_t * server = resolver->data;

    if (status < 0)
    {
        log_error("Cannot resolve ip address for server '%s' (error: %s)",
                server->name,
                uv_err_name(status));

        sirinet_stream_decref(server->client);
    }
    else
    {
        if (Logger.level == LOGGER_DEBUG)
        {
            char addr[47] = {'\0'};  /* enough for both ipv4 and ipv6 */

            switch (res->ai_family)
            {
            case AF_INET:
                uv_ip4_name((struct sockaddr_in *) res->ai_addr, addr, 16);
                break;

            case AF_INET6:
                uv_ip6_name((struct sockaddr_in6 *) res->ai_addr, addr, 46);
                break;

            default:
                sprintf(addr, "unsupported family");
            }

            log_debug(
                    "Resolved ip address '%s' for server '%s', "
                    "trying to connect...",
                    addr, server->name);

        }
        uv_connect_t * req = malloc(sizeof(uv_connect_t));
        if (req == NULL)
        {
            ERR_ALLOC
        }
        else
        {
            uv_tcp_connect(
                    req,
                    (uv_tcp_t *) server->client->stream,
                    (const struct sockaddr *) res->ai_addr,
                    SERVER_on_connect);
        }
    }

    uv_freeaddrinfo(res);
    free(resolver);
}

/*
 * Update SERVER_FLAG_QUEUE_FULL based on number of promises.
 */
static void SERVER_upd_flag_queue_full(siridb_server_t * server)
{
    if (server->promises->n >= SIRIDB_SERVER_PROMISES_QUEUE_SIZE)
    {
        server->flags |= SERVER_FLAG_QUEUE_FULL;
    }
    else
    {
        server->flags &= ~SERVER_FLAG_QUEUE_FULL;
    }
}

/*
 * Write call-back.
 */
static void SERVER_write_cb(uv_write_t * req, int status)
{
    sirinet_promise_t * promise = (sirinet_promise_t *) req->data;

    if (status)
    {
        log_error(
            "Socket write error to server '%s' (pid: %" PRIu16 ", error: %s)",
            promise->server->name,
            promise->pid,
            uv_strerror(status));

        if (omap_rm(promise->server->promises, promise->pid) == NULL)
        {
            log_critical(
                    "Got a socket error but the promise is not found. "
                    "(PID: %" PRIu16 ")",
                    promise->pid);
            return;
        }
        SERVER_upd_flag_queue_full(promise->server);

        uv_timer_stop(promise->timer);
        uv_close((uv_handle_t *) promise->timer, (uv_close_cb) free);

        promise->cb(promise, NULL, PROMISE_WRITE_ERROR);
    }

    free(promise->pkg); /* NULL when FLAG_KEEP_PKG is set */
    sirinet_promise_decref(promise);

    free(req);
}

/*
 * Timeout received.
 */
static void SERVER_timeout_pkg(uv_timer_t * handle)
{
    sirinet_promise_t * promise = handle->data;

    if (omap_rm(promise->server->promises, promise->pid) == NULL)
    {
        log_critical(
                "Timeout task is called on package (PID %" PRIu16
                ") for server '%s' "
                "but we cannot find this promise!!",
                promise->pid,
                promise->server->name);
        return;
    }
    else
    {
        SERVER_upd_flag_queue_full(promise->server);
        log_warning("Timeout on package (PID %" PRIu16 ") for server '%s'",
                promise->pid,
                promise->server->name);
    }
    /* the timer is stopped but we still need to close the timer */
    uv_close((uv_handle_t *) promise->timer, (uv_close_cb) free);

    promise->cb(promise, NULL, PROMISE_TIMEOUT_ERROR);
}

/*
 * This function can raise a SIGNAL.
 */
static void SERVER_on_connect(uv_connect_t * req, int status)
{
    sirinet_stream_t * client = req->handle->data;
    siridb_t * siridb = client->siridb;
    siridb_server_t * server = client->origin;

    if (status == 0)
    {
        log_debug(
                "Connection created to back-end server: '%s', "
                "sending authentication request", server->name);

        server->retry_attempts = 0;  /* reset connection attempts */

        uv_read_start(
                req->handle,
                sirinet_stream_alloc_buffer,
                sirinet_stream_on_data);

        sirinet_pkg_t * pkg;
        qp_packer_t * packer = sirinet_packer_new(512);

        if (packer == NULL)
        {
            ERR_ALLOC
        }
        else
        {
            if (qp_add_type(packer, QP_ARRAY_OPEN) ||
                qp_add_raw(packer, (const unsigned char *)
                        client->siridb->server->uuid, 16) ||
                qp_add_string_term(packer, siridb->dbname) ||
                qp_add_int64(packer, siridb->server->flags) ||
                qp_add_string_term(packer, SIRIDB_VERSION) ||
                qp_add_string_term(packer, SIRIDB_MINIMAL_VERSION) ||
                qp_add_int64(packer, (int64_t) siri.cfg->ip_support) ||
                qp_add_string_term(packer, uv_version_string()) ||
                qp_add_string_term(packer, siridb->dbpath) ||
                qp_add_string_term(packer, siridb->buffer->path) ||
                qp_add_int64(packer, (int64_t) siridb->buffer->size) ||
                qp_add_int64(packer, (int64_t) siri.startup_time) ||
                qp_add_string_term(packer, siridb->server->address) ||
                qp_add_int64(packer, (int64_t) siridb->server->port))
            {
                qp_packer_free(packer);
            }
            else
            {
                pkg = sirinet_packer2pkg(packer, 0, BPROTO_AUTH_REQUEST);

                if (siridb_server_send_pkg(
                        server,
                        pkg,
                        0,
                        (sirinet_promise_cb) SERVER_on_auth_response,
                        NULL,
                        0))
                {
                    free(pkg);
                }
            }
        }
    }
    else
    {
        log_error("Connecting to back-end server '%s' failed (error: %s)",
                server->name,
                uv_strerror(status));

        sirinet_stream_decref(client);
    }
    free(req);
}

/*
 * on-data call-back function.
 *In case the promise is found, promise->cb() will be called.
 */
static void SERVER_on_data(sirinet_stream_t * client, sirinet_pkg_t * pkg)
{
    siridb_server_t * server = client->origin;
    sirinet_promise_t * promise = omap_rm(server->promises, pkg->pid);

    log_debug(
            "Response received (pid: %" PRIu16
            ", len: %" PRIu32 ", tp: %s) from '%s'",
            pkg->pid,
            pkg->len,
            sirinet_bproto_server_str(pkg->tp),
            server->name);

    if (promise == NULL)
    {
        log_warning(
                "Received a package (PID %" PRIu16
                ") from server '%s' which has probably timed-out earlier.",
                pkg->pid,
                server->name);
    }
    else
    {
        SERVER_upd_flag_queue_full(promise->server);
        uv_timer_stop(promise->timer);
        uv_close((uv_handle_t *) promise->timer, (uv_close_cb) free);
        promise->cb(promise, pkg, PROMISE_SUCCESS);
    }
}

/*
 * Returns the current server status (flags) as string. the returned value
 * is created with malloc() so do not forget to free the result.
 *
 * NULL is returned in case malloc has failed.
 */
char * siridb_server_str_status(siridb_server_t * server)
{
    /* we must initialize the buffer according to the longest possible value */
    char buffer[128] = {};
    int n = 0;
    int i;

    for (i = 1; i < SERVER_FLAG_AUTHENTICATED; i *= 2)
    {
        if (server->flags & i)
        {
            switch (i)
            {
            case SERVER_FLAG_RUNNING:
                strcat(buffer, (!n) ? "running" : " | " "running");
                break;
            case SERVER_FLAG_SYNCHRONIZING:
                strcat(buffer, (!n) ? "synchronizing" : " | " "synchronizing");
                break;
            case SERVER_FLAG_REINDEXING:
                strcat(buffer, (!n) ? "re-indexing" : " | " "re-indexing");
                break;
            case SERVER_FLAG_BACKUP_MODE:
                strcat(buffer, (!n) ? "backup-mode" : " | " "backup-mode");
                break;
            case SERVER_FLAG_QUEUE_FULL:
                strcat(buffer, (!n) ? "queue-full" : " | " "queue-full");
                break;
            case SERVER_FLAG_UNAVAILABLE:
                strcat(buffer, (!n) ? "unavailable" : " | " "unavailable");
                break;
            }
            n = 1;
        }
    }
    return strdup((n) ? buffer : "offline");
}

/*
 * Returns server object by node or NULL if the server is not found.
 */
siridb_server_t * siridb_server_from_node(
        siridb_t * siridb,
        cleri_node_t * server_node,
        char * err_msg)
{
    siridb_server_t * server = NULL;

    switch (server_node->cl_obj->tp)
    {
    case CLERI_TP_CHOICE:  /* server name   */
        {
            char name[server_node->len - 1];
            xstr_extract_string(name, server_node->str, server_node->len);
            server = siridb_servers_by_name(siridb->servers, name);
        }
        break;

    case CLERI_TP_REGEX:  /* uuid   */
        {
            uuid_t uuid;
            char * str_uuid = strndup(server_node->str, server_node->len);
            server = (uuid_parse(str_uuid, uuid) == 0) ?
                    siridb_servers_by_uuid(siridb->servers, uuid) : NULL;
            free(str_uuid);
        }
        break;

    default:
        assert (0);
        break;
    }

    if (server == NULL && err_msg != NULL)
    {
        snprintf(
                err_msg,
                SIRIDB_MAX_SIZE_ERR_MSG,
                "Cannot find server: %.*s",
                (int) server_node->len,
                server_node->str);
    }

    return server;
}

/*
 * Returns 0 if successful or -1 and a SIGNAL is raised in case of an error.
 * (an error can only happen when we are not able to save the new servers file)
 */
int siridb_server_drop(siridb_t * siridb, siridb_server_t * server)
{
    int rc = 0;
    assert (siridb->server != server);
    siridb_pool_t * pool = siridb->pools->pool + server->pool;

    switch (server->id)
    {
    case 0:
        assert (pool->len == 2);
        pool->server[0] = pool->server[1];
        pool->server[0]->id = 0;
        /* FALLTHRU */
        /* fall through */
    case 1:
        pool->server[1] = NULL;
        pool->len = 1;
        break;
    default:
        assert (0);
        break;
    }

    if (server == siridb->replica)
    {
        if (siridb->replicate != NULL)
        {
            siridb_replicate_close(siridb->replicate);
            siridb_replicate_free(&siridb->replicate);
        }

        if (siridb->fifo != NULL)
        {
            siridb_fifo_free(siridb->fifo);
            siridb->fifo = NULL;
        }

        siridb->replica = NULL;

        if (siridb->server->flags & SERVER_FLAG_SYNCHRONIZING)
        {
            siridb->server->flags &= ~SERVER_FLAG_SYNCHRONIZING;
            siridb_servers_send_flags(siridb->servers);
        }
    }

    if ((siridb_server_t *) llist_remove(
            siridb->servers, NULL, server) == server)
    {
        siridb_server_decref(server);
        rc = siridb_servers_save(siridb);
    }
    else
    {
        /* can never be reached */
        assert (0);
    }
    return rc;
}

/*
 * Do not call this function but use siridb_server_decref.
 *
 * Free server. If the server has promises, each promise will be cancelled and
 * so each promise->cb() will be called.
 */
void siridb__server_free(siridb_server_t * server)
{
    /* we MUST first free the promises because each promise has a reference to
     * this server and the promise callback might depend on this.
     */
    if (server->promises != NULL)
    {
        omap_destroy(server->promises, (omap_destroy_cb) SERVER_cancel_promise);
    }
    free(server->name);
    free(server->address);
    free(server->version);
    free(server->libuv);
    free(server->dbpath);
    free(server->buffer_path);
    free(server);
}

/*
 * Returns true when the given property (CLERI keyword) needs a remote query
 */
int siridb_server_is_remote_prop(uint32_t prop)
{
    switch (prop)
    {
    /* these are the local props */
    case CLERI_GID_K_ADDRESS:
    case CLERI_GID_K_BUFFER_PATH:
    case CLERI_GID_K_BUFFER_SIZE:
    case CLERI_GID_K_DBPATH:
    case CLERI_GID_K_IP_SUPPORT:
    case CLERI_GID_K_LIBUV:
    case CLERI_GID_K_NAME:
    case CLERI_GID_K_ONLINE:
    case CLERI_GID_K_POOL:
    case CLERI_GID_K_PORT:
    case CLERI_GID_K_STARTUP_TIME:
    case CLERI_GID_K_STATUS:
    case CLERI_GID_K_UUID:
    case CLERI_GID_K_VERSION:
        return 0;
    }
    return 1;
}

int siridb_server_cexpr_cb(
        siridb_server_walker_t * wserver,
        cexpr_condition_t * cond)
{
    switch (cond->prop)
    {
    case CLERI_GID_K_ADDRESS:
        return cexpr_str_cmp(
                cond->operator,
                wserver->server->address,
                cond->str);

    case CLERI_GID_K_BUFFER_PATH:
        return cexpr_str_cmp(
                cond->operator,
                (wserver->siridb->server == wserver->server) ?
                        wserver->siridb->buffer->path :
                        (wserver->server->buffer_path != NULL) ?
                                wserver->server->buffer_path : "",
                cond->str);

    case CLERI_GID_K_BUFFER_SIZE:
        return cexpr_int_cmp(
                cond->operator,
                (wserver->siridb->server == wserver->server) ?
                        wserver->siridb->buffer->size :
                        wserver->server->buffer_size,
                cond->int64);

    case CLERI_GID_K_DBPATH:
        return cexpr_str_cmp(
                cond->operator,
                (wserver->siridb->server == wserver->server) ?
                        wserver->siridb->dbpath :
                        (wserver->server->dbpath != NULL) ?
                                wserver->server->dbpath : "",
                cond->str);

    case CLERI_GID_K_IP_SUPPORT:
        return cexpr_str_cmp(
                cond->operator,
                sirinet_tcp_ip_support_str(
                        (wserver->siridb->server == wserver->server) ?
                                siri.cfg->ip_support :
                                wserver->server->ip_support),
                cond->str);

    case CLERI_GID_K_LIBUV:
        return cexpr_str_cmp(
                cond->operator,
                (wserver->siridb->server == wserver->server) ?
                        uv_version_string() :
                        (wserver->server->libuv != NULL) ?
                                wserver->server->libuv : "",
                cond->str);

    case CLERI_GID_K_NAME:
        return cexpr_str_cmp(
                cond->operator,
                wserver->server->name,
                cond->str);

    case CLERI_GID_K_ONLINE:
        return cexpr_bool_cmp(
                cond->operator,
                (   wserver->siridb->server == wserver->server ||
                    wserver->server->client != NULL),
                cond->int64);

    case CLERI_GID_K_POOL:
        return cexpr_int_cmp(
                cond->operator,
                wserver->server->pool,
                cond->int64);

    case CLERI_GID_K_PORT:
        return cexpr_int_cmp(
                cond->operator,
                wserver->server->port,
                cond->int64);

    case CLERI_GID_K_STARTUP_TIME:
        return cexpr_int_cmp(
                cond->operator,
                (wserver->siridb->server == wserver->server) ?
                        siri.startup_time :
                        wserver->server->startup_time,
                cond->int64);

    case CLERI_GID_K_STATUS:
        {
            char * status = siridb_server_str_status(wserver->server);
            int rc = cexpr_str_cmp(cond->operator, status, cond->str);
            free(status);
            return rc;
        }

    case CLERI_GID_K_UUID:
        {
            char uuid[37];
            uuid_unparse_lower(wserver->server->uuid, uuid);
            return cexpr_str_cmp(cond->operator, uuid, cond->str);
        }

    case CLERI_GID_K_VERSION:
        return cexpr_str_cmp(
                cond->operator,
                (wserver->siridb->server == wserver->server) ?
                        SIRIDB_VERSION :
                        (wserver->server->version != NULL) ?
                                wserver->server->version : "",
                cond->str);

    /* all properties below are 'remote properties'. if a remote property
     * is detected we should perform the query on each server and only for
     * that specific server.
     */
    case CLERI_GID_K_LOG_LEVEL:
        return cexpr_int_cmp(
                cond->operator,
                Logger.level,
                cond->int64);

    case CLERI_GID_K_MAX_OPEN_FILES:
        return cexpr_int_cmp(
                cond->operator,
                siri.cfg->max_open_files,
                cond->int64);

    case CLERI_GID_K_MEM_USAGE:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) (procinfo_total_physical_memory() / 1024),
                cond->int64);

    case CLERI_GID_K_FIFO_FILES:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) siridb_fifo_size(wserver->siridb->fifo),
                cond->int64);

    case CLERI_GID_K_OPEN_FILES:
        return cexpr_int_cmp(
                cond->operator,
                siridb_open_files(wserver->siridb),
                cond->int64);

    case CLERI_GID_K_RECEIVED_POINTS:
        return cexpr_int_cmp(
                cond->operator,
                wserver->siridb->received_points,
                cond->int64);

    case CLERI_GID_K_SELECTED_POINTS:
        return cexpr_int_cmp(
                cond->operator,
                wserver->siridb->selected_points,
                cond->int64);

    case CLERI_GID_K_UPTIME:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) siridb_get_uptime(wserver->siridb),
                cond->int64);

    case CLERI_GID_K_ACTIVE_HANDLES:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) siri.loop->active_handles,
                cond->int64);

    case CLERI_GID_K_ACTIVE_TASKS:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) wserver->siridb->tasks.active,
                cond->int64);

    case CLERI_GID_K_IDLE_PERCENTAGE:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) siridb_get_idle_percentage(wserver->siridb),
                cond->int64);

    case CLERI_GID_K_IDLE_TIME:
        return cexpr_int_cmp(
                cond->operator,
                (int64_t) wserver->siridb->tasks.idle_time,
                cond->int64);

    case CLERI_GID_K_REINDEX_PROGRESS:
        return cexpr_str_cmp(
                cond->operator,
                siridb_reindex_progress(wserver->siridb),
                cond->str);

    case CLERI_GID_K_SYNC_PROGRESS:
        return cexpr_str_cmp(
                cond->operator,
                siridb_initsync_sync_progress(wserver->siridb),
                cond->str);
    }

    log_critical("Unexpected server property received: %d", cond->prop);
    assert (0);
    return -1;
}

/*
 * Cancel promise. The promise->cb will be called.
 */
static void SERVER_cancel_promise(sirinet_promise_t * promise)
{
    if (!uv_is_closing((uv_handle_t *) promise->timer))
    {
        uv_timer_stop(promise->timer);
        uv_close((uv_handle_t *) promise->timer, (uv_close_cb) free);
    }
    promise->cb(promise, NULL, PROMISE_CANCELLED_ERROR);
}


/*
 * Returns 0 if successful or -1 in case of an allocation error.
 * (server->name is unchanged in case of an error)
 */
static int SERVER_update_name(siridb_server_t * server)
{
    /* start len with 2, one for : and one for 0 terminator */
    size_t len = 2;
    uint16_t i = server->port;
    char * tmp;
    int fmt_as_ipv6 = 0;  /* false */

    assert (server->port > 0);

    /* append 'string' length for server->port */
    for (; i; i /= 10, len++);

    if FMT_AS_IPV6(server->address)
    {
        len += 2;
        fmt_as_ipv6 = 1;  /* true */
    }

    /* append 'address' length */
    len += strlen(server->address);

    assert (len > 0);

    /* allocate enough space */
    tmp = (char *) realloc(server->name, len);
    if (tmp == NULL)
    {
        return -1;
    }

    server->name = tmp;

    if (fmt_as_ipv6)
    {
        sprintf(server->name, "[%s]:%d", server->address, server->port);
    }
    else
    {
        sprintf(server->name, "%s:%d", server->address, server->port);
    }
    return 0;
}

static void SERVER_on_auth_response(
        sirinet_promise_t * promise,
        sirinet_pkg_t * pkg,
        int status)
{
    if (status)
    {
        /* we already have a log entry so this can be a debug log */
        log_debug(
                "Error while sending authentication request to '%s' (%s)",
                promise->server->name,
                sirinet_promise_strstatus(status));
    }
    else if (pkg->tp == BPROTO_AUTH_SUCCESS)
    {
        log_info("Successful authenticated to server '%s'",
                promise->server->name);

        promise->server->flags |= SERVER_FLAG_AUTHENTICATED;
    }
    else
    {
        log_error("Authentication with server '%s' failed, error code: %d",
                promise->server->name,
                pkg->tp);
    }

    if (    (status || pkg->tp != BPROTO_AUTH_SUCCESS) &&
            promise->server->client != NULL)
    {
        sirinet_stream_decref(promise->server->client);
    }

    /* we must free the promise */
    sirinet_promise_decref(promise);
}

static void SERVER_on_flags_update_response(
        sirinet_promise_t * promise,
        sirinet_pkg_t * pkg,
        int status)
{
    if (status)
    {
        /* we already have a log entry so this can be a debug log */
        log_debug(
                "Error while sending flags update to '%s' (%s)",
                promise->server->name,
                sirinet_promise_strstatus(status));

        if (promise->server->client != NULL)
        {
            siridb_t * siridb =  promise->server->client->siridb;
            siridb_server_t * replica = siridb_servers_by_replica(
                    siridb->servers,
                    promise->server);
            if (replica != NULL && (
                    replica == siridb->server ||
                    siridb_server_is_accessible(replica)))
            {
                /* we only set the status unavailable if we have an accessible
                 * replica or when we are the replica
                 */
                log_warning(
                        "Set status for server '%s' to unavailable. "
                        "(unavailable status will be removed after a new status "
                        "is received)", promise->server->name);
                promise->server->flags |= SERVER_FLAG_UNAVAILABLE;
            }
        }
    }
    else if (pkg->tp == BPROTO_ACK_FLAGS)
    {
        log_debug("Flags ACK received from '%s'", promise->server->name);
    }
    else
    {
        log_critical("Unexpected package type received from '%s' (type: %u)",
                promise->server->name,
                pkg->tp);
    }

    /* we must free the promise */
    sirinet_promise_decref(promise);
}
