/**
 * xrdp: A Remote Desktop Protocol server.
 *
 * Copyright (C) Jay Sorg 2006-2013
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * channel layer
 */

#if defined(HAVE_CONFIG_H)
#include <config_ac.h>
#endif

#include "libxrdp.h"

/* todo, move these to constants.h */
//#define CHANNEL_CHUNK_LENGTH 1600 /* todo, why is this so small? */
#define CHANNEL_CHUNK_LENGTH 8192
#define CHANNEL_FLAG_FIRST 0x01
#define CHANNEL_FLAG_LAST 0x02
#define CHANNEL_FLAG_SHOW_PROTOCOL 0x10

/*****************************************************************************/
/* returns pointer or nil on error */
static struct mcs_channel_item *
xrdp_channel_get_item(struct xrdp_channel *self, int channel_id)
{
    struct mcs_channel_item *channel;

    if (self->mcs_layer->channel_list == NULL)
    {
        g_writeln("xrdp_channel_get_item - No channel initialized");
        return NULL ;
    }

    channel = (struct mcs_channel_item *)
              list_get_item(self->mcs_layer->channel_list, channel_id);
    return channel;
}

/*****************************************************************************/
struct xrdp_channel *
xrdp_channel_create(struct xrdp_sec *owner, struct xrdp_mcs *mcs_layer)
{
    struct xrdp_channel *self;

    self = (struct xrdp_channel *)g_malloc(sizeof(struct xrdp_channel), 1);
    self->sec_layer = owner;
    self->mcs_layer = mcs_layer;
    return self;
}

/*****************************************************************************/
/* returns error */
void
xrdp_channel_delete(struct xrdp_channel *self)
{
    if (self == 0)
    {
        return;
    }

    g_memset(self, 0, sizeof(struct xrdp_channel));
    g_free(self);
}

/*****************************************************************************/
/* returns error */
int
xrdp_channel_init(struct xrdp_channel *self, struct stream *s)
{
    if (xrdp_sec_init(self->sec_layer, s) != 0)
    {
        return 1;
    }

    s_push_layer(s, channel_hdr, 8);
    return 0;
}

/*****************************************************************************/
/* returns error */
/* This sends data out to the secure layer. */
int
xrdp_channel_send(struct xrdp_channel *self, struct stream *s, int channel_id,
                  int total_data_len, int flags)
{
    struct mcs_channel_item *channel;

    channel = xrdp_channel_get_item(self, channel_id);

    if (channel == NULL)
    {
        g_writeln("xrdp_channel_send - no such channel");
        return 1;
    }

    s_pop_layer(s, channel_hdr);
    out_uint32_le(s, total_data_len);

    /*
     * According to 2.2.1.3.4.1 Channel Definition Structure (CHANNEL_DEF):
     * CHANNEL_OPTION_SHOW_PROTOCOL 0x00200000
     *  The value of this flag MUST be ignored by the server. The
     *  visibility of the Channel PDU Header (section 2.2.6.1.1) is
     *  determined by the CHANNEL_FLAG_SHOW_PROTOCOL
     *  (0x00000010) flag as defined in the flags field (section
     *  2.2.6.1.1).
     *
     *   That's flag makes MSTSC crash when using RAIL channel.
     */
//    if (channel->flags & XR_CHANNEL_OPTION_SHOW_PROTOCOL)
//    {
//        flags |= CHANNEL_FLAG_SHOW_PROTOCOL;
//    }

    out_uint32_le(s, flags);

    if (xrdp_sec_send(self->sec_layer, s, channel->chanid) != 0)
    {
        g_writeln("xrdp_channel_send - failure sending data");
        return 1;
    }

    return 0;
}

/*****************************************************************************/
/* returns error */
/* this will inform the callback, whatever it is that some channel data is
   ready.  the default for this is a call to xrdp_wm.c. */
static int
xrdp_channel_call_callback(struct xrdp_channel *self, struct stream *s,
                           int channel_id,
                           int total_data_len, int flags)
{
    struct xrdp_session *session;
    int rv;
    int size;

    rv = 0;
    session = self->sec_layer->rdp_layer->session;

    if (session != 0)
    {
        if (session->callback != 0)
        {
            size = (int)(s->end - s->p);
            /* in xrdp_wm.c */
            rv = session->callback(session->id, 0x5555,
                                   MAKELONG(channel_id, flags),
                                   size, (tbus)(s->p), total_data_len);
        }
        else
        {
            g_writeln("in xrdp_channel_call_callback, session->callback is nil");
        }
    }
    else
    {
        g_writeln("in xrdp_channel_call_callback, session is nil");
    }

    return rv;
}

/*****************************************************************************/
/* returns error */
/* This is called from the secure layer to process an incoming non global
   channel packet.
   'chanid' passed in here is the mcs channel id so it MCS_GLOBAL_CHANNEL
   plus something. */
int
xrdp_channel_process(struct xrdp_channel *self, struct stream *s,
                     int chanid)
{
    int length;
    int flags;
    int rv;
    int channel_id;
    struct mcs_channel_item *channel;


    /* this assumes that the channels are in order of chanid(mcs channel id)
       but they should be, see xrdp_sec_process_mcs_data_channels
       the first channel should be MCS_GLOBAL_CHANNEL + 1, second
       one should be MCS_GLOBAL_CHANNEL + 2, and so on */
    channel_id = (chanid - MCS_GLOBAL_CHANNEL) - 1;
    channel = xrdp_channel_get_item(self, channel_id);

    if (channel == NULL)
    {
        g_writeln("xrdp_channel_process, channel not found");
        return 1;
    }

    rv = 0;
    in_uint32_le(s, length);
    in_uint32_le(s, flags);
    rv = xrdp_channel_call_callback(self, s, channel_id, length, flags);
    return rv;
}