/*******************************************************************************
*
* Copyright (c) 2015 Intel Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
*    http://www.eclipse.org/legal/epl-v10.html
* The Eclipse Distribution License is available at
*    http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
*    David Navarro, Intel Corporation - initial API and implementation
*    Christian Renz - Please refer to git log
*    Christian Manal - Ported to RIOT OS
*
*******************************************************************************/

/*
 * Copyright (C) 2018 Beduino Master Projekt - University of Bremen
 * Copyright (C) 2019 HAW Hamburg
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */

/**
 * @{
 * @ingroup     lwm2m_client
 *
 * @file
 * @brief       Connection handle for LwM2M client implementation using Wakaama
 *
 * @author      Christian Manal <manal@uni-bremen.de>
 * @author      Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
 * @}
 */

#include <stddef.h>
#include <inttypes.h>
#include "kernel_defines.h"
#include "net/netif.h"
#include "uri_parser.h"

#include "liblwm2m.h"
#include "net/sock/udp.h"

#if IS_USED(MODULE_WAKAAMA_CLIENT_DTLS)
#include "net/sock/dtls.h"
#endif

#include "lwm2m_client.h"
#include "lwm2m_client_config.h"
#include "lwm2m_client_connection.h"
#include "objects/common.h"

#define ENABLE_DEBUG 0
#include "debug.h"

#define MAX_URI_LENGTH 256

/**
 * @brief Creates a new connection object based on the security instance
 *        represented by @p instance_id.
 *
 * @param[in] instance_id ID number of the instance of security object
 * @param[in, out] client_data LwM2M client data
 *
 * @return Pointer to the new connection
 */
static lwm2m_client_connection_t *_connection_create(uint16_t sec_obj_inst_id,
                                                     lwm2m_client_data_t *client_data);

/**
 * @brief Sends data with a specified connection @p conn
 *
 * @param[in] conn connection to use to send data
 * @param[in] buffer data to send
 * @param[in] buffer_size size of @p buffer
 * @param[in] client_data LwM2M client data
 *
 * @return 0 on success
 * @return -1 otherwise
 */
static int _connection_send(lwm2m_client_connection_t *conn, uint8_t *buffer,
                            size_t buffer_size,
                            lwm2m_client_data_t *client_data);

/**
 * @brief Tries to find an interface by interface string. If not, it will check
 *        if there only exists one interface, and will use it
 * @param[in]  iface         interface string
 * @param[in]  iface_len     interface string length
 *
 * @return  pointer to the interface to use on success
 * @retval  NULL on error
 */
static netif_t *_get_interface(const char *iface, size_t len);

void *lwm2m_connect_server(uint16_t sec_obj_inst_id, void *user_data)
{
    lwm2m_client_data_t *client_data = (lwm2m_client_data_t *)user_data;
    lwm2m_client_connection_t *new_conn;

    DEBUG("[lwm2m_connect_server] Connecting to server in security instance %" PRIu16 "\n", sec_obj_inst_id);

    new_conn = _connection_create(sec_obj_inst_id, client_data);
    if (new_conn) {
        DEBUG("[lwm2m_connect_server] Connection created\n");
        /* if the connections list is empty this is the first node, if not
         * attach to the last one */
        if (!client_data->conn_list) {
            client_data->conn_list = new_conn;
        }
        else {
            lwm2m_client_connection_t *last = client_data->conn_list;
            while (last->next != NULL) {
                last = last->next;
            }
            last->next = new_conn;
        }
    }

    return new_conn;
}

void lwm2m_close_connection(void *sessionH, void *user_data)
{
    lwm2m_client_connection_t *conn = (lwm2m_client_connection_t *) sessionH;
    lwm2m_client_data_t *client_data = (lwm2m_client_data_t *) user_data;

    if (conn == client_data->conn_list) {
        client_data->conn_list = conn->next;
    }
    else {
        lwm2m_client_connection_t *prev = client_data->conn_list;

        while (prev != NULL && prev->next != conn) {
            prev = prev->next;
        }
        if (prev != NULL) {
            prev->next = conn->next;
            lwm2m_free(conn);
        }
    }
}

bool lwm2m_session_is_equal(void *session1, void *session2, void *user_data)
{
    (void)user_data;
    lwm2m_client_connection_t *conn_1 = (lwm2m_client_connection_t *)session1;
    lwm2m_client_connection_t *conn_2 = (lwm2m_client_connection_t *)session2;

    return ((conn_1->remote.port == conn_2->remote.port) &&
            ipv6_addr_equal((ipv6_addr_t *)&(conn_1->remote.addr.ipv6),
                            (ipv6_addr_t *)&(conn_2->remote.addr.ipv6)));
}

uint8_t lwm2m_buffer_send(void *sessionH, uint8_t *buffer, size_t length,
                          void *userdata)
{
    lwm2m_client_data_t *client_data = (lwm2m_client_data_t *)userdata;
    lwm2m_client_connection_t *conn = (lwm2m_client_connection_t *)sessionH;

    if (!conn) {
        DEBUG("[lwm2m_buffer_send] Failed to send, missing connection\n");
        return COAP_500_INTERNAL_SERVER_ERROR;
    }

    if (_connection_send(conn, buffer, length, client_data)) {
        DEBUG("[lwm2m_buffer_send] Failed to send\n");
        return COAP_500_INTERNAL_SERVER_ERROR;
    }

    return COAP_NO_ERROR;
}

lwm2m_client_connection_t *lwm2m_client_connection_find(lwm2m_client_connection_t *conn_list,
                                                        const sock_udp_ep_t *remote,
                                                        lwm2m_client_connection_type_t type)
{
    lwm2m_client_connection_t *conn = conn_list;

    char ip[128];
    uint8_t ip_len = 128;

    ipv6_addr_to_str(ip, (ipv6_addr_t *)&remote->addr.ipv6, ip_len);
    DEBUG("Looking for connection from [%s]:%" PRIu16 "\n", ip, remote->port);

    if (conn_list == NULL) {
        DEBUG("Conn list is null!");
    }

    while (conn != NULL) {
        ipv6_addr_to_str(ip, (ipv6_addr_t *)&conn->remote.addr.ipv6, ip_len);
        DEBUG("Comparing to [%s]:%" PRIu16 "\n", ip, conn->remote.port);
        if ((conn->remote.port == remote->port) && conn->type == type &&
            ipv6_addr_equal((ipv6_addr_t *)&(conn->remote.addr.ipv6),
                            (ipv6_addr_t *)&(remote->addr.ipv6))) {
            break;
        }
        conn = conn->next;
    }
    return conn;
}

int lwm2m_connection_handle_packet(lwm2m_client_connection_t *conn, uint8_t *buffer,
                                   size_t num_bytes, lwm2m_client_data_t *client_data)
{
    lwm2m_handle_packet(client_data->lwm2m_ctx, buffer, num_bytes, conn);
    return 0;
}

static int _connection_send(lwm2m_client_connection_t *conn, uint8_t *buffer,
                            size_t buffer_size,
                            lwm2m_client_data_t *client_data)
{
    DEBUG("[_connection_send] trying to send %" PRIiSIZE " bytes\n", buffer_size);
    if (conn->type == LWM2M_CLIENT_CONN_UDP) {
        ssize_t sent_bytes = sock_udp_send(&(client_data->sock), buffer,
                                        buffer_size, &(conn->remote));
        if (sent_bytes <= 0) {
            DEBUG("[_connection_send] Could not send UDP packet: %i\n", (int)sent_bytes);
            return -1;
        }
    }
#if IS_USED(MODULE_WAKAAMA_CLIENT_DTLS)
    else {
        ssize_t sent_bytes = sock_dtls_send(&client_data->dtls_sock, &conn->session, buffer,
                                            buffer_size, SOCK_NO_TIMEOUT);
        if (sent_bytes <= 0) {
            DEBUG("[_connection_send] Could not send DTLS packet: %i\n", (int)sent_bytes);
            return -1;
        }
    }
#endif /* MODULE_WAKAAMA_CLIENT_DTLS */

    conn->last_send = lwm2m_gettime();
    return 0;
}

static netif_t *_get_interface(const char *iface, size_t iface_len)
{
    netif_t *netif = NULL;

    if (!iface || !iface_len) {
        DEBUG("[lwm2m:client] no interface defined in host\n");
        /* get the number of net interfaces */
        unsigned netif_numof = 0;
        while ((netif = netif_iter(netif)) != NULL) {
                netif_numof++;
        }
        /* if we only have one interface use that one */
        if (netif_numof == 1) {
            netif = netif_iter(NULL);
        }
        else {
            DEBUG("[_connection_create] No iface for link-local address\n");
        }
    }
    else {
        DEBUG("[lwm2m:client] getting interface by name %.*s\n", (unsigned)iface_len, iface);
        netif = netif_get_by_name_buffer(iface, iface_len);
    }

    return netif;
}

static lwm2m_client_connection_t *_connection_create(uint16_t sec_obj_inst_id,
                                                     lwm2m_client_data_t *client_data)
{
    lwm2m_client_connection_t *conn = NULL;
    char uri[MAX_URI_LENGTH] = { 0 };
    size_t uri_len = ARRAY_SIZE(uri);
    uint16_t port;
    bool is_bootstrap;

    DEBUG("Creating connection\n");

    /* prepare Server URI query */
    lwm2m_uri_t resource_uri = {
        .objectId = LWM2M_SECURITY_URI_ID,
        .instanceId = sec_obj_inst_id,
        .resourceId = LWM2M_SECURITY_URI_ID,
        .flag = LWM2M_URI_FLAG_OBJECT_ID | LWM2M_URI_FLAG_INSTANCE_ID | LWM2M_URI_FLAG_RESOURCE_ID
    };

    int res = lwm2m_get_string(client_data, &resource_uri, uri, &uri_len);
    if (res < 0) {
        DEBUG("[_connection_create] Could not get security instance URI\n");
        goto out;
    }

    uri_parser_result_t parsed_uri;
    res = uri_parser_process_string(&parsed_uri, uri);

    if (0 != res || !parsed_uri.host) {
        DEBUG("[_connection_create] Could not parse URI schema\n");
        goto out;
    }

    resource_uri.resourceId = LWM2M_SECURITY_BOOTSTRAP_ID;
    res = lwm2m_get_bool(client_data, &resource_uri, &is_bootstrap);
    if (res < 0) {
        DEBUG("[_connection_create] Could verify if the server is bootstrap\n");
        goto out;
    }

    /* if no port specified, use the default server or BS-server ports */
    if (parsed_uri.port == 0) {
        if (is_bootstrap) {
            port = atoi(CONFIG_LWM2M_BSSERVER_PORT);
        }
        else {
            port = atoi(CONFIG_LWM2M_STANDARD_PORT);
        }
    }
    else {
        port = parsed_uri.port;
    }

    DEBUG("[_connection_create] Creating connection to Host: %.*s, Port: %" PRIu16 "\n",
          parsed_uri.ipv6addr_len, parsed_uri.ipv6addr, port);

    /* allocate new connection */
    conn = lwm2m_malloc(sizeof(lwm2m_client_connection_t));
    if (!conn) {
        DEBUG("[_connection_create] Could not allocate new connection\n");
        goto out;
    }
    conn->next = client_data->conn_list;

    /* configure to any IPv6 */
    conn->remote.family = AF_INET6;
    conn->remote.netif = SOCK_ADDR_ANY_NETIF;
    conn->remote.port = port;

    if (!ipv6_addr_from_buf((ipv6_addr_t *)&conn->remote.addr.ipv6, parsed_uri.ipv6addr,
                            parsed_uri.ipv6addr_len)) {
        DEBUG("[_connection_create] IPv6 address malformed\n");
        goto free_out;
    }

    if (ipv6_addr_is_unspecified((const ipv6_addr_t *)&conn->remote.addr.ipv6)) {
        DEBUG("[_connection_create] Invalid server address ([::])\n");
        goto free_out;
    }

    /* If the address is a link-local one first check if interface is specified,
     * if not, check the number of interfaces and default to the first if there
     * is only one defined. */
    if (ipv6_addr_is_link_local((ipv6_addr_t *)&conn->remote.addr.ipv6)) {
        netif_t *netif = _get_interface(parsed_uri.zoneid, parsed_uri.zoneid_len);

        if (netif == NULL) {
            DEBUG("[lwm2m:client] could not determine an interface to use\n");
            goto free_out;
        }
        else {
            int16_t netif_id = netif_get_id(netif);
            if (netif_id < 0) {
                goto free_out;
            }
            conn->remote.netif = netif_id;
        }
    }

#if IS_USED(MODULE_WAKAAMA_CLIENT_DTLS)
    uint8_t buf[DTLS_HANDSHAKE_BUFSIZE];
    int64_t val;
    resource_uri.resourceId = LWM2M_SECURITY_SECURITY_ID;
    res = lwm2m_get_int(client_data, &resource_uri, &val);
    if (res < 0) {
        DEBUG("[lwm2m:client] could not get security instance mode\n");
        goto free_out;
    }

    if (val == LWM2M_SECURITY_MODE_PRE_SHARED_KEY || val == LWM2M_SECURITY_MODE_RAW_PUBLIC_KEY) {
        conn->type = LWM2M_CLIENT_CONN_DTLS;
        DEBUG("[lwm2m:client] DTLS session init\n");
        res = sock_dtls_session_init(&client_data->dtls_sock, &conn->remote, &conn->session);
        if (res <= 0) {
            DEBUG("[lwm2m:client] could not initiate DTLS session\n");
            goto free_out;
        }

        DEBUG("[lwm2m:client] receiving DTLS handshake\n");
        res = sock_dtls_recv(&client_data->dtls_sock, &conn->session, buf, sizeof(buf), US_PER_SEC);
        if (res != -SOCK_DTLS_HANDSHAKE) {
            DEBUG("[lwm2m:client] error creating session: %i\n", res);
            goto free_out;
        }
        DEBUG("[lwm2m:client] connection to server successful\n");
    }
    else {
        conn->type = LWM2M_CLIENT_CONN_UDP;
    }
#else
    conn->type = LWM2M_CLIENT_CONN_UDP;
#endif /* MODULE_WAKAAMA_CLIENT_DTLS */

    conn->last_send = lwm2m_gettime();
    goto out;

free_out:
    lwm2m_free(conn);
    conn = NULL;
out:
    return conn;
}