/*******************************************************************************
 *
 * 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 v2.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v20.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
 *
 *******************************************************************************/

/**
 * @license
 * Copyright (c) 2019 CANDY LINE INC.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v20.html
 * The Eclipse Distribution License is available at
 *    http://www.eclipse.org/org/documents/edl-v10.php.
 */

#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "dtlsconnection.h"
#include "commandline.h"
#include "lwm2mclient.h"
#include "internals.h"

#define COAP_PORT "5683"
#define COAPS_PORT "5684"
#define URI_LENGTH 256

dtls_context_t * dtlsContext;

/********************* Security Obj Helpers **********************/
char * security_get_uri(lwm2m_object_t * obj, int instanceId, char * uriBuffer, int bufferSize){
    int size = 1;
    lwm2m_data_t * dataP = lwm2m_data_new(size);
    dataP->id = 0; // security server uri

    obj->readFunc(instanceId, &size, &dataP, obj);
    if (dataP != NULL &&
            (dataP->type == LWM2M_TYPE_STRING || dataP->type == LWM2M_TYPE_OPAQUE) &&
            dataP->value.asBuffer.length > 0)
    {
        if (bufferSize > dataP->value.asBuffer.length){
            memset(uriBuffer,0,dataP->value.asBuffer.length+1);
            strncpy(uriBuffer,dataP->value.asBuffer.buffer,dataP->value.asBuffer.length);
            lwm2m_data_free(size, dataP);
            return uriBuffer;
        }
    }
    lwm2m_data_free(size, dataP);
    return NULL;
}

int64_t security_get_mode(lwm2m_object_t * obj, int instanceId){
    int64_t mode;
    int size = 1;
    lwm2m_data_t * dataP = lwm2m_data_new(size);
    dataP->id = 2; // security mode

    obj->readFunc(instanceId, &size, &dataP, obj);
    if (0 != lwm2m_data_decode_int(dataP,&mode))
    {
        lwm2m_data_free(size, dataP);
        return mode;
    }

    lwm2m_data_free(size, dataP);
    fprintf(stderr, "Unable to get security mode : use not secure mode");
    return LWM2M_SECURITY_MODE_NONE;
}

char * security_get_public_id(lwm2m_object_t * obj, int instanceId, int * length){
    int size = 1;
    lwm2m_data_t * dataP = lwm2m_data_new(size);
    dataP->id = 3; // public key or id

    obj->readFunc(instanceId, &size, &dataP, obj);
    if (dataP != NULL &&
        dataP->type == LWM2M_TYPE_OPAQUE)
    {
        char * buff;

        buff = (char*)lwm2m_malloc(dataP->value.asBuffer.length);
        if (buff != 0)
        {
            memcpy(buff, dataP->value.asBuffer.buffer, dataP->value.asBuffer.length);
            *length = dataP->value.asBuffer.length;
        }
        lwm2m_data_free(size, dataP);

        return buff;
    } else {
        return NULL;
    }
}


char * security_get_secret_key(lwm2m_object_t * obj, int instanceId, int * length){
    int size = 1;
    lwm2m_data_t * dataP = lwm2m_data_new(size);
    dataP->id = 5; // secret key

    obj->readFunc(instanceId, &size, &dataP, obj);
    if (dataP != NULL &&
        dataP->type == LWM2M_TYPE_OPAQUE)
    {
        char * buff;

        buff = (char*)lwm2m_malloc(dataP->value.asBuffer.length);
        if (buff != 0)
        {
            memcpy(buff, dataP->value.asBuffer.buffer, dataP->value.asBuffer.length);
            *length = dataP->value.asBuffer.length;
        }
        lwm2m_data_free(size, dataP);

        return buff;
    } else {
        return NULL;
    }
}

/********************* Security Obj Helpers Ends **********************/

/* Returns the number sent, or -1 for errors */
static int send_data(dtls_connection_t *connP,
                    uint8_t * buffer,
                    size_t length)
{
    int nbSent;
    size_t offset;
    client_data_t * clientData;
    clientData = (client_data_t *) connP->lwm2mH->userData;

    in_port_t port;
    char s[INET6_ADDRSTRLEN];

    if (clientData->showMessageDump) {
        s[0] = 0;

        if (AF_INET == connP->addr.sin6_family)
        {
            struct sockaddr_in *saddr = (struct sockaddr_in *)&connP->addr;
            inet_ntop(saddr->sin_family, &saddr->sin_addr, s, INET6_ADDRSTRLEN);
            port = saddr->sin_port;
        }
        else if (AF_INET6 == connP->addr.sin6_family)
        {
            struct sockaddr_in6 *saddr = (struct sockaddr_in6 *)&connP->addr;
            inet_ntop(saddr->sin6_family, &saddr->sin6_addr, s, INET6_ADDRSTRLEN);
            port = saddr->sin6_port;
        }
    }
    fprintf(stderr, "Sending %d bytes to [%s]:%hu\r\n", length, s, ntohs(port));
    if (clientData->showMessageDump) {
        output_buffer(stderr, buffer, length, 0);
    }

    offset = 0;
    while (offset != length)
    {
        nbSent = sendto(connP->sock, buffer + offset, length - offset, 0, (struct sockaddr *)&(connP->addr), connP->addrLen);
        if (nbSent == -1) return -1;
        offset += nbSent;
    }
    connP->lastSend = lwm2m_gettime();
    return offset;
}

/**************************  TinyDTLS Callbacks  ************************/

/* This function is the "key store" for tinyDTLS. It is called to
 * retrieve a key for the given identity within this particular
 * session. */
static int get_psk_info(struct dtls_context_t *ctx,
        const session_t *session,
        dtls_credentials_type_t type,
        const unsigned char *id, size_t id_len,
        unsigned char *result, size_t result_length) {

    // find connection
    dtls_connection_t* cnx = connection_find((dtls_connection_t *) ctx->app, &(session->addr.st),session->size);
    if (cnx == NULL)
    {
        fprintf(stderr, "GET PSK session not found\n");
        return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
    }

    switch (type) {
        case DTLS_PSK_IDENTITY:
        {
            int idLen;
            char * id;
            id = security_get_public_id(cnx->securityObj, cnx->securityInstId, &idLen);
            if (result_length < idLen)
            {
                fprintf(stderr, "cannot set psk_identity -- buffer too small\n");
                return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
            }

            memcpy(result, id,idLen);
            lwm2m_free(id);
            return idLen;
        }
        case DTLS_PSK_KEY:
        {
            int keyLen;
            char * key;
            key = security_get_secret_key(cnx->securityObj, cnx->securityInstId, &keyLen);

            if (result_length < keyLen)
            {
                fprintf(stderr, "cannot set psk -- buffer too small\n");
                return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
            }

            memcpy(result, key,keyLen);
            lwm2m_free(key);
            return keyLen;
        }
        case DTLS_PSK_HINT:
        {
            // PSK_HINT is optional and can be empty.
            return 0;
        }
        default:
            fprintf(stderr, "unsupported request type: %d\n", type);
    }

    return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
}

/* The callback function must return the number of bytes
 * that were sent, or a value less than zero to indicate an
 * error. */
static int send_to_peer(struct dtls_context_t *ctx,
        session_t *session, uint8 *data, size_t len) {

    LOG("send_to_peer callabck");
    // find connection
    dtls_connection_t * connP = (dtls_connection_t *) ctx->app;
    dtls_connection_t * cnx = connection_find(connP, &(session->addr.st),session->size);
    if (cnx != NULL)
    {
        // send data to peer

        // TODO: nat expiration?
        int res = send_data(cnx,data,len);
        if (res < 0)
        {
            LOG("Nothing sent! send_data failed!");
            return -1;
        }
        return res;
    }
    LOG("Nothing sent! cnx is NULL");
    return -1;
}

static int read_from_peer(struct dtls_context_t *ctx,
          session_t *session, uint8 *data, size_t len) {

    // find connection
    dtls_connection_t * connP = (dtls_connection_t *) ctx->app;
    dtls_connection_t * cnx = connection_find(connP, &(session->addr.st),session->size);
    if (cnx != NULL)
    {
        lwm2m_handle_packet(cnx->lwm2mH, (uint8_t*)data, len, (void*)cnx);
        return 0;
    }
    return -1;
}
/**************************   TinyDTLS Callbacks Ends ************************/

static dtls_handler_t cb = {
  .write = send_to_peer,
  .read  = read_from_peer,
  .event = NULL,
//#ifdef DTLS_PSK
  .get_psk_info = get_psk_info,
//#endif /* DTLS_PSK */
//#ifdef DTLS_ECC
//  .get_ecdsa_key = get_ecdsa_key,
//  .verify_ecdsa_key = verify_ecdsa_key
//#endif /* DTLS_ECC */
};

dtls_context_t * get_dtls_context(dtls_connection_t * connList) {
    if (dtlsContext == NULL) {
        dtls_init();
        dtlsContext = dtls_new_context(connList);
        if (dtlsContext == NULL)
            fprintf(stderr, "Failed to create the DTLS context\r\n");
        dtls_set_handler(dtlsContext, &cb);
    }else{
        dtlsContext->app = connList;
    }
    return dtlsContext;
}

int get_port(struct sockaddr *x)
{
   if (x->sa_family == AF_INET)
   {
       return ((struct sockaddr_in *)x)->sin_port;
   } else if (x->sa_family == AF_INET6) {
       return ((struct sockaddr_in6 *)x)->sin6_port;
   } else {
       fprintf(stderr, "non IPV4 or IPV6 address\n");
       return  -1;
   }
}

int sockaddr_cmp(struct sockaddr *x, struct sockaddr *y)
{
    int portX = get_port(x);
    int portY = get_port(y);

    // if the port is invalid of different
    if (portX == -1 || portX != portY)
    {
        return 0;
    }

    // IPV4?
    if (x->sa_family == AF_INET)
    {
        // is V4?
        if (y->sa_family == AF_INET)
        {
            // compare V4 with V4
            return ((struct sockaddr_in *)x)->sin_addr.s_addr == ((struct sockaddr_in *)y)->sin_addr.s_addr;
            // is V6 mapped V4?
        } else if (IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)y)->sin6_addr)) {
            struct in6_addr* addr6 = &((struct sockaddr_in6 *)y)->sin6_addr;
            uint32_t y6to4 = addr6->s6_addr[15] << 24 | addr6->s6_addr[14] << 16 | addr6->s6_addr[13] << 8 | addr6->s6_addr[12];
            return y6to4 == ((struct sockaddr_in *)x)->sin_addr.s_addr;
        } else {
            return 0;
        }
    } else if (x->sa_family == AF_INET6 && y->sa_family == AF_INET6) {
        // IPV6 with IPV6 compare
        return memcmp(((struct sockaddr_in6 *)x)->sin6_addr.s6_addr, ((struct sockaddr_in6 *)y)->sin6_addr.s6_addr, 16) == 0;
    } else {
        // unknown address type
        fprintf(stderr, "non IPV4 or IPV6 address\n");
        return 0;
    }
}

int create_socket(const char * portStr, int ai_family)
{
    int s = -1;
    struct addrinfo hints;
    struct addrinfo *res;
    struct addrinfo *p;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = ai_family;
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_flags = AI_PASSIVE;

    if (0 != getaddrinfo(NULL, portStr, &hints, &res))
    {
        return -1;
    }

    for(p = res ; p != NULL && s == -1 ; p = p->ai_next)
    {
        s = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (s >= 0)
        {
            if (-1 == bind(s, p->ai_addr, p->ai_addrlen))
            {
                close(s);
                s = -1;
            }
        }
    }

    freeaddrinfo(res);

    return s;
}

dtls_connection_t * connection_find(dtls_connection_t * connList,
                               const struct sockaddr_storage * addr,
                               size_t addrLen)
{
    dtls_connection_t * connP;

    connP = connList;
    while (connP != NULL)
    {

       if (sockaddr_cmp((struct sockaddr*) (&connP->addr),(struct sockaddr*) addr)) {
            return connP;
       }

       connP = connP->next;
    }

    return connP;
}

dtls_connection_t * connection_new_incoming(dtls_connection_t * connList,
                                       int sock,
                                       const struct sockaddr * addr,
                                       size_t addrLen)
{
    dtls_connection_t * connP;

    connP = (dtls_connection_t *)lwm2m_malloc(sizeof(dtls_connection_t));
    if (connP != NULL)
    {
        memset(connP, 0, sizeof(dtls_connection_t));
        connP->sock = sock;
        memcpy(&(connP->addr), addr, addrLen);
        connP->addrLen = addrLen;
        connP->next = connList;

        connP->dtlsSession = (session_t *)lwm2m_malloc(sizeof(session_t));
        memset(connP->dtlsSession, 0, sizeof(session_t));
        connP->dtlsSession->addr.sin6 = connP->addr;
        connP->dtlsSession->size = connP->addrLen;
        connP->lastSend = lwm2m_gettime();
    }

    return connP;
}

dtls_connection_t * connection_create(dtls_connection_t * connList,
                                 int sock,
                                 lwm2m_object_t * securityObj,
                                 int instanceId,
                                 lwm2m_context_t * lwm2mH,
                                 int addressFamily)
{
    struct addrinfo hints;
    struct addrinfo *servinfo = NULL;
    struct addrinfo *p;
    int s;
    struct sockaddr *sa;
    socklen_t sl;
    dtls_connection_t * connP = NULL;
    char uriBuf[URI_LENGTH];
    char * uri;
    char * host;
    char * port;

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = addressFamily;
    hints.ai_socktype = SOCK_DGRAM;

    uri = security_get_uri(securityObj, instanceId, uriBuf, URI_LENGTH);
    if (uri == NULL) return NULL;

    // parse uri in the form "coaps://[host]:[port]"
    char * defaultport;
    if (0 == strncmp(uri, "coaps://", strlen("coaps://")))
    {
        host = uri+strlen("coaps://");
        defaultport = COAPS_PORT;
    }
    else if (0 == strncmp(uri, "coap://", strlen("coap://")))
    {
        host = uri+strlen("coap://");
        defaultport = COAP_PORT;
    }
    else
    {
        return NULL;
    }
    port = strrchr(host, ':');
    if (port == NULL)
    {
        port = defaultport;
    }
    else
    {
        // remove brackets
        if (host[0] == '[')
        {
            host++;
            if (*(port - 1) == ']')
            {
                *(port - 1) = 0;
            }
            else
            {
                return NULL;
            }
        }
        // split strings
        *port = 0;
        port++;
    }

    if (0 != getaddrinfo(host, port, &hints, &servinfo) || servinfo == NULL) return NULL;

    // we test the various addresses
    s = -1;
    for(p = servinfo ; p != NULL && s == -1 ; p = p->ai_next)
    {
        s = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (s >= 0)
        {
            sa = p->ai_addr;
            sl = p->ai_addrlen;
            if (-1 == connect(s, p->ai_addr, p->ai_addrlen))
            {
                close(s);
                s = -1;
            }
        }
    }
    if (s >= 0)
    {
        connP = connection_new_incoming(connList, sock, sa, sl);
        close(s);

        // do we need to start tinydtls?
        if (connP != NULL)
        {
            connP->securityObj = securityObj;
            connP->securityInstId = instanceId;
            connP->lwm2mH = lwm2mH;

            if (security_get_mode(connP->securityObj,connP->securityInstId)
                     != LWM2M_SECURITY_MODE_NONE)
            {
                connP->dtlsContext = get_dtls_context(connP);
                // Ensure peer is refreshed
                dtls_peer_t * peer = dtls_get_peer(connP->dtlsContext, connP->dtlsSession);
                if (peer != NULL)
                {
                    peer->state =  DTLS_STATE_CLOSED;
                    dtls_reset_peer(connP->dtlsContext, peer);
                }
            }
            else
            {
                // no dtls session
                connP->dtlsSession = NULL;
            }
        }
    }

    if (NULL != servinfo) freeaddrinfo(servinfo);

    return connP;
}

void connection_free(dtls_connection_t * connList)
{
    dtls_free_context(dtlsContext);
    dtlsContext = NULL;
    while (connList != NULL)
    {
        dtls_connection_t * nextP;

        nextP = connList->next;
        lwm2m_free(connList);

        connList = nextP;
    }
}

int connection_send(dtls_connection_t *connP, uint8_t * buffer, size_t length){
    if (connP->dtlsSession == NULL) {
        // no security
        if ( 0 != send_data(connP, buffer, length)) {
            return -1 ;
        }
    } else {
        if (DTLS_NAT_TIMEOUT > 0 && (lwm2m_gettime() - connP->lastSend) > DTLS_NAT_TIMEOUT)
        {
            // we need to rehandhake because our source IP/port probably changed for the server
            if ( connection_rehandshake(connP, false) != 0 )
            {
                fprintf(stderr, "can't send due to rehandshake error\n");
                return -1;
            }
        }
        LOG("perform dtls_write");
        if (-1 == dtls_write(connP->dtlsContext, connP->dtlsSession, buffer, length)) {
            return -1;
        }
    }

    return 0;
}

int connection_handle_packet(dtls_connection_t *connP, uint8_t * buffer, size_t numBytes){

    if (connP->dtlsSession != NULL)
    {
        // Let liblwm2m respond to the query depending on the context
        int result = dtls_handle_message(connP->dtlsContext, connP->dtlsSession, buffer, numBytes);
        if (result !=0) {
             fprintf(stderr, "error dtls handling message %d\n",result);
        }
        return result;
    } else {
        // no security, just give the plaintext buffer to liblwm2m
        lwm2m_handle_packet(connP->lwm2mH, buffer, numBytes, (void*)connP);
        return 0;
    }
}

int connection_rehandshake(dtls_connection_t *connP, bool sendCloseNotify) {

    // if not a dtls connection we do nothing
    if (connP->dtlsSession == NULL) {
        return 0;
    }

    // reset current session
    dtls_peer_t * peer = dtls_get_peer(connP->dtlsContext, connP->dtlsSession);
    if (peer != NULL)
    {
        if (!sendCloseNotify)
        {
            peer->state =  DTLS_STATE_CLOSED;
        }
        dtls_reset_peer(connP->dtlsContext, peer);
    }

    // start a fresh handshake
    int result = dtls_connect(connP->dtlsContext, connP->dtlsSession);
    if (result !=0) {
         fprintf(stderr, "error dtls reconnection %d\n",result);
    }
    return result;
}

uint8_t lwm2m_buffer_send(void * sessionH,
                          uint8_t * buffer,
                          size_t length,
                          void * userdata)
{
    dtls_connection_t * connP = (dtls_connection_t*) sessionH;
    LOG_ARG("Entering lwm2m_buffer_send (connP:%p)", connP);

    if (connP == NULL)
    {
        fprintf(stderr, "#> failed sending %lu bytes, missing connection\r\n", length);
        return COAP_500_INTERNAL_SERVER_ERROR ;
    }

    if (-1 == connection_send(connP, buffer, length))
    {
        fprintf(stderr, "#> failed sending %lu bytes\r\n", length);
        return COAP_500_INTERNAL_SERVER_ERROR ;
    }

    return COAP_NO_ERROR;
}

bool lwm2m_session_is_equal(void * session1,
                            void * session2,
                            void * userData)
{
    return (session1 == session2);
}