/**  msi.c
 *
 *   Copyright (C) 2013-2015 Tox project All Rights Reserved.
 *
 *   This file is part of Tox.
 *
 *   Tox 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.
 *
 *   Tox 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 Tox. If not, see <http://www.gnu.org/licenses/>.
 *
 */


#ifdef HAVE_CONFIG_H
#include "config.h"
#endif /* HAVE_CONFIG_H */

#include "../toxcore/logger.h"
#include "../toxcore/util.h"

#include "msi.h"

#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

#define MSI_MAXMSG_SIZE 256

/**
 * Protocol:
 *
 * |id [1 byte]| |size [1 byte]| |data [$size bytes]| |...{repeat}| |0 {end byte}|
 */

typedef enum {
    IDRequest = 1,
    IDError,
    IDCapabilities,
    IDVFPSZ,

} MSIHeaderID;


typedef enum {
    requ_push,
    requ_pop,
} MSIRequest;


#define GENERIC_HEADER(header, val_type) \
typedef struct { \
    val_type value; \
    bool exists; \
} MSIHeader##header


GENERIC_HEADER ( Request, MSIRequest );
GENERIC_HEADER ( Error, MSIError );
GENERIC_HEADER ( Capabilities, uint8_t );
GENERIC_HEADER ( VFPSZ, uint16_t );


typedef struct {
    MSIHeaderRequest      request;
    MSIHeaderError        error;
    MSIHeaderCapabilities capabilities;
    MSIHeaderVFPSZ        vfpsz; /* Video frame piece size. NOTE: Value must be in network b-order */
} MSIMessage;


void msg_init (MSIMessage *dest, MSIRequest request);
int msg_parse_in ( MSIMessage *dest, const uint8_t *data, uint16_t length );
uint8_t *msg_parse_header_out ( MSIHeaderID id, uint8_t *dest, const void *value, uint8_t value_len, uint16_t *length );
int send_message ( Messenger* m, uint32_t friend_id, const MSIMessage *msg );
int send_error ( Messenger* m, uint32_t friend_id, MSIError error );
static int invoke_callback(MSICall* call, MSICallbackID cb);
static MSICall *get_call ( MSISession *session, uint32_t friend_id );
MSICall *new_call ( MSISession *session, uint32_t friend_id );
void kill_call ( MSICall *call );
void on_peer_status(Messenger *m, int friend_id, uint8_t status, void *data);
void handle_push ( MSICall *call, const MSIMessage *msg );
void handle_pop ( MSICall *call, const MSIMessage *msg );
void handle_msi_packet ( Messenger *m, int friend_id, const uint8_t *data, uint16_t length, void *object );


/**
 * Public functions
 */
void msi_register_callback ( MSISession *session, MSICallbackType callback, MSICallbackID id)
{
    pthread_mutex_lock(session->mutex);
    session->callbacks[id] = callback;
    pthread_mutex_unlock(session->mutex);
}
MSISession *msi_new ( Messenger *messenger )
{
    if (messenger == NULL) {
        LOGGER_ERROR("Could not init session on empty messenger!");
        return NULL;
    }
    
    MSISession *retu = calloc ( sizeof ( MSISession ), 1 );
    
    if (retu == NULL) {
        LOGGER_ERROR("Allocation failed! Program might misbehave!");
        return NULL;
    }
    
    if (create_recursive_mutex(retu->mutex) != 0) {
        LOGGER_ERROR("Failed to init mutex! Program might misbehave");
        free(retu);
        return NULL;
    }
    
    retu->messenger = messenger;
    
    m_callback_msi_packet(messenger, handle_msi_packet, retu );
    
    /* This is called when remote terminates session */
    m_callback_connectionstatus_internal_av(messenger, on_peer_status, retu);
    
    LOGGER_DEBUG("New msi session: %p ", retu);
    return retu;
}
int msi_kill ( MSISession *session )
{
    if (session == NULL) {
        LOGGER_ERROR("Tried to terminate non-existing session");
        return -1;
    }
    
    m_callback_msi_packet((struct Messenger *) session->messenger, NULL, NULL);
    pthread_mutex_lock(session->mutex);
    
    if (session->calls) {
        MSIMessage msg;
        msg_init(&msg, requ_pop);
        
        MSICall* it = get_call(session, session->calls_head);
        for (; it; it = it->next) {
            send_message(session->messenger, it->friend_id, &msg);
            kill_call(it); /* This will eventually free session->calls */
        }
    }
    
    pthread_mutex_unlock(session->mutex);
    pthread_mutex_destroy(session->mutex);
    
    LOGGER_DEBUG("Terminated session: %p", session);
    free ( session );
    return 0;
}
int msi_invite ( MSISession *session, MSICall **call, uint32_t friend_id, uint8_t capabilities )
{
    LOGGER_DEBUG("Session: %p Inviting friend: %u", session, friend_id);
    
    pthread_mutex_lock(session->mutex);
    if (get_call(session, friend_id) != NULL) {
        LOGGER_ERROR("Already in a call");
        pthread_mutex_unlock(session->mutex);
        return -1;
    }
    
    (*call) = new_call ( session, friend_id );
    
    if ( *call == NULL ) {
        pthread_mutex_unlock(session->mutex);
        return -1;
    }
    
    (*call)->self_capabilities = capabilities;
    
    MSIMessage msg;
    msg_init(&msg, requ_push);
    
    msg.capabilities.exists = true;
    msg.capabilities.value = capabilities;
    
    msg.vfpsz.exists = true;
    msg.vfpsz.value = htons(VIDEOFRAME_PIECE_SIZE);
    
    send_message ( (*call)->session->messenger, (*call)->friend_id, &msg );
    
    (*call)->state = msi_CallRequesting;
    
    LOGGER_DEBUG("Invite sent");
    pthread_mutex_unlock(session->mutex);
    return 0;
}
int msi_hangup ( MSICall* call )
{
    LOGGER_DEBUG("Session: %p Hanging up call with friend: %u", call->session, call->friend_id);
    
    MSISession* session = call->session;
    pthread_mutex_lock(session->mutex);
    
    MSIMessage msg;
    msg_init(&msg, requ_pop);
    
    send_message ( session->messenger, call->friend_id, &msg );
    
    kill_call(call);
    pthread_mutex_unlock(session->mutex);
    return 0;
}
int msi_answer ( MSICall* call, uint8_t capabilities )
{
    LOGGER_DEBUG("Session: %p Answering call from: %u", call->session, call->friend_id);
    
    MSISession* session = call->session;
    pthread_mutex_lock(session->mutex);
    
    if ( call->state != msi_CallRequested ) {
        /* Though sending in invalid state will not cause anything wierd 
         * Its better to not do it like a maniac */
        LOGGER_ERROR("Call is in invalid state!");
        pthread_mutex_unlock(session->mutex);
        return -1;
    }
    
    call->self_capabilities = capabilities;
    
    MSIMessage msg;
    msg_init(&msg, requ_push);
    
    msg.capabilities.exists = true;
    msg.capabilities.value = capabilities;
    
    msg.vfpsz.exists = true;
    msg.vfpsz.value = htons(VIDEOFRAME_PIECE_SIZE);
    
    send_message ( session->messenger, call->friend_id, &msg );
    
    call->state = msi_CallActive;
    pthread_mutex_unlock(session->mutex);
    
    return 0;
}
int msi_change_capabilities( MSICall* call, uint8_t capabilities )
{
    LOGGER_DEBUG("Session: %p Trying to change capabilities to friend %u", call->session, call->friend_id);
    
    MSISession* session = call->session;
    pthread_mutex_lock(session->mutex);
    
    if ( call->state != msi_CallActive ) {
        /* Sending capabilities change can cause error on other side if 
         * the call is not active since we don't send header 'vfpsz'.
         * If we were to send 'vfpsz' while call is active it would be
         * ignored. However, if call is not active peer will expect
         * the said header on 'push' so that it could handle the call
         * like new. TODO: explain this better
         */
        LOGGER_ERROR("Call is in invalid state!");
        pthread_mutex_unlock(session->mutex);
        return -1;
    }
    
    call->self_capabilities = capabilities;
    
    MSIMessage msg;
    msg_init(&msg, requ_push);
    
    msg.capabilities.exists = true;
    msg.capabilities.value = capabilities;
    
    send_message ( call->session->messenger, call->friend_id, &msg );
    
    pthread_mutex_unlock(session->mutex);
    return 0;
}


/**
 * Private functions
 */
void msg_init(MSIMessage* dest, MSIRequest request)
{
    memset(dest, 0, sizeof(*dest));
    dest->request.exists = true;
    dest->request.value = request;
}
int msg_parse_in ( MSIMessage *dest, const uint8_t *data, uint16_t length )
{
    /* Parse raw data received from socket into MSIMessage struct */
    
#define CHECK_SIZE(bytes, constraint, size) \
    if ((constraint -= (2 + size)) < 1) { LOGGER_ERROR("Read over length!"); return -1; } \
    if ( bytes[1] != size ) { LOGGER_ERROR("Invalid data size!"); return -1; }
    
#define CHECK_ENUM_HIGH(bytes, enum_high) /* Assumes size == 1 */ \
    if ( bytes[2] > enum_high ) { LOGGER_ERROR("Failed enum high limit!"); return -1; }
    
#define SET_UINT8(bytes, header) do { \
        header.value = bytes[2]; \
        header.exists = true; \
        bytes += 3; \
    } while(0)

#define SET_UINT16(bytes, header) do { \
        memcpy(&header.value, bytes + 2, 2);\
        header.exists = true; \
        bytes += 4; \
    } while(0)
    
    
    assert(dest);

    if ( length == 0 || data[length - 1] ) { /* End byte must have value 0 */
        LOGGER_ERROR("Invalid end byte");
        return -1;
    }
    
    memset(dest, 0, sizeof(*dest));
    
    const uint8_t *it = data;
    int size_constraint = length;

    while ( *it ) {/* until end byte is hit */
        switch (*it) {
            case IDRequest:
                CHECK_SIZE(it, size_constraint, 1);
                CHECK_ENUM_HIGH(it, requ_pop);
                SET_UINT8(it, dest->request);
                break;
                
            case IDError:
                CHECK_SIZE(it, size_constraint, 1);
                CHECK_ENUM_HIGH(it, msi_EUndisclosed);
                SET_UINT8(it, dest->error);
                break;
                
            case IDCapabilities:
                CHECK_SIZE(it, size_constraint, 1);
                SET_UINT8(it, dest->capabilities);
                break;
            
            case IDVFPSZ:
                CHECK_SIZE(it, size_constraint, 2);
                SET_UINT16(it, dest->vfpsz);
                break;
                
            default:
                LOGGER_ERROR("Invalid id byte");
                return -1;
                break;
        }
    }

    if (dest->request.exists == false) {
        LOGGER_ERROR("Invalid request field!");
        return -1;
    }
    
    return 0;

#undef CHECK_SIZE
#undef CHECK_ENUM_HIGH
#undef SET_UINT8
#undef SET_UINT16
}
uint8_t *msg_parse_header_out ( MSIHeaderID id, uint8_t *dest, const void *value, uint8_t value_len, uint16_t *length )
{
    /* Parse a single header for sending */
    assert(dest);
    assert(value);
    assert(value_len);
    
    *dest = id;
    dest ++;
    *dest = value_len;
    dest ++;

    memcpy(dest, value, value_len);

    *length += (2 + value_len);

    return dest + value_len; /* Set to next position ready to be written */
}
int send_message ( Messenger* m, uint32_t friend_id, const MSIMessage *msg )
{
    /* Parse and send message */
    assert(m);
    
    uint8_t parsed [MSI_MAXMSG_SIZE];

    uint8_t *it = parsed;
    uint16_t size = 0;
    
    if (msg->request.exists) {
        uint8_t cast = msg->request.value;
        it = msg_parse_header_out(IDRequest, it, &cast, 
                                  sizeof(cast), &size);
    } else {
        LOGGER_DEBUG("Must have request field");
        return -1;
    }
    
    if (msg->error.exists) {
        uint8_t cast = msg->error.value;
        it = msg_parse_header_out(IDError, it, &cast, 
                                  sizeof(cast), &size);
    }
    
    if (msg->capabilities.exists) {
        it = msg_parse_header_out(IDCapabilities, it, &msg->capabilities.value, 
                                  sizeof(msg->capabilities.value), &size);
    }
    
    if (msg->vfpsz.exists) {
        it = msg_parse_header_out(IDVFPSZ, it, &msg->vfpsz.value,
                                  sizeof(msg->vfpsz.value), &size);
    }
    
    if ( it == parsed ) {
        LOGGER_WARNING("Parsing message failed; empty message");
        return -1;
    }
    
    *it = 0;
    size ++;
    
    if ( m_msi_packet(m, friend_id, parsed, size) ) {
        LOGGER_DEBUG("Sent message");
        return 0;
    }

    return -1;
}
int send_error ( Messenger* m, uint32_t friend_id, MSIError error )
{
    /* Send error message */
    assert(m);
    
    LOGGER_DEBUG("Sending error: %d to friend: %d", error, friend_id);

    MSIMessage msg;
    msg_init(&msg, requ_pop);
    
    msg.error.exists = true;
    msg.error.value = error;
    
    send_message ( m, friend_id, &msg );
    return 0;
}
int invoke_callback(MSICall* call, MSICallbackID cb)
{
    assert(call);
    
    if ( call->session->callbacks[cb] ) {
        LOGGER_DEBUG("Invoking callback function: %d", cb);
        if ( call->session->callbacks[cb] ( call->session->av, call ) != 0 ) {
            LOGGER_WARNING("Callback state handling failed, sending error");
            goto FAILURE;
        }
        
        return 0;
    }
    
FAILURE:
    /* If no callback present or error happened while handling,
     * an error message will be sent to friend
     */
    
    if (call->error == msi_ENone)
        call->error = msi_EHandle;
    return -1;
}
static MSICall *get_call ( MSISession *session, uint32_t friend_id )
{
    assert(session);
    
    if (session->calls == NULL || session->calls_tail < friend_id)
        return NULL;
    
    return session->calls[friend_id];
}
MSICall *new_call ( MSISession *session, uint32_t friend_id )
{
    assert(session);
    
    MSICall *rc = calloc(sizeof(MSICall), 1);
    
    if (rc == NULL)
        return NULL;
    
    rc->session = session;
    rc->friend_id = friend_id;
    
    if (session->calls == NULL) { /* Creating */
        session->calls = calloc (sizeof(MSICall*), friend_id + 1);
        
        if (session->calls == NULL) {
            free(rc);
            return NULL;
        }
        
        session->calls_tail = session->calls_head = friend_id;
        
    } else if (session->calls_tail < friend_id) { /* Appending */
        void* tmp = realloc(session->calls, sizeof(MSICall*) * friend_id + 1);
        
        if (tmp == NULL) {
            free(rc);
            return NULL;
        }
        
        session->calls = tmp;
        
        /* Set fields in between to null */
        int32_t i = session->calls_tail;
        for (; i < friend_id; i ++)
            session->calls[i] = NULL;
        
        rc->prev = session->calls[session->calls_tail];
        session->calls[session->calls_tail]->next = rc;
        
        session->calls_tail = friend_id;
        
    } else if (session->calls_head > friend_id) { /* Inserting at front */
        rc->next = session->calls[session->calls_head];
        session->calls[session->calls_head]->prev = rc;
        session->calls_head = friend_id;
    }
    
    session->calls[friend_id] = rc;
    return rc;
}
void kill_call ( MSICall *call )
{
    /* Assume that session mutex is locked */
    if ( call == NULL )
        return;
    
    LOGGER_DEBUG("Killing call: %p", call);
    
    MSISession* session = call->session;
    
    MSICall* prev = call->prev;
    MSICall* next = call->next;
    
    if (prev)
        prev->next = next;
    else if (next)
        session->calls_head = next->friend_id;
    else goto CLEAR_CONTAINER;
    
    if (next)
        next->prev = prev;
    else if (prev)
        session->calls_tail = prev->friend_id;
    else goto CLEAR_CONTAINER;
    
    session->calls[call->friend_id] = NULL;
    free(call);
    return;
    
CLEAR_CONTAINER:
    session->calls_head = session->calls_tail = 0;
    free(session->calls);
    free(call);
    session->calls = NULL;
}
void on_peer_status(Messenger *m, int friend_id, uint8_t status, void *data)
{
    (void)m;
    MSISession *session = data;

    switch ( status ) {
        case 0: { /* Friend is now offline */
            LOGGER_DEBUG("Friend %d is now offline", friend_id);
            
            pthread_mutex_lock(session->mutex);
            MSICall* call = get_call(session, friend_id);
            
            if (call == NULL) {
                pthread_mutex_unlock(session->mutex);
                return;
            }
            
            invoke_callback(call, msi_OnPeerTimeout); /* Failure is ignored */
            kill_call(call);
            pthread_mutex_unlock(session->mutex);
        }
        break;

        default:
            break;
    }
}
void handle_push ( MSICall *call, const MSIMessage *msg )
{
    assert(call);
    
    MSISession* session = call->session;
    
    LOGGER_DEBUG("Session: %p Handling 'push' friend: %d", call->session, call->friend_id);

    if (!msg->capabilities.exists) {
        LOGGER_WARNING("Session: %p Invalid capabilities on 'push'");
        call->error = msi_EInvalidMessage;
        goto FAILURE;
    }
    
    if (call->state != msi_CallActive) {
        if (!msg->vfpsz.exists) {
            LOGGER_WARNING("Session: %p Invalid vfpsz on 'push'");
            call->error = msi_EInvalidMessage;
            goto FAILURE;
        }
        
        call->peer_vfpsz = ntohs(msg->vfpsz.value);
    }
    
    
    switch (call->state) {
        case msi_CallInactive: {
            LOGGER_INFO("Friend is calling us");
            
            /* Call requested */
            call->peer_capabilities = msg->capabilities.value;
            call->state = msi_CallRequested;
            
            if ( invoke_callback(call, msi_OnInvite) == -1 )
                goto FAILURE;
            
        } break;
        
        case msi_CallActive: {
            if (msg->vfpsz.exists) {
                /* If peer sended video frame piece size 
                 * while the call is already active it's probable
                 * that he is trying to re-call us while the call
                 * is not terminated on our side. We can assume that
                 * in this case we can automatically answer the re-call.
                 */
                if (call->peer_vfpsz != ntohs(msg->vfpsz.value)) {
                    LOGGER_WARNING("Friend sent invalid parameters for re-call");
                    call->error = msi_EInvalidParam;
                    invoke_callback(call, msi_OnError);
                    goto FAILURE;
                }
                
                LOGGER_INFO("Friend is recalling us");
                
                MSIMessage msg;
                msg_init(&msg, requ_push);
                
                msg.capabilities.exists = true;
                msg.capabilities.value = call->self_capabilities;
                
                msg.vfpsz.exists = true;
                msg.vfpsz.value = htons(VIDEOFRAME_PIECE_SIZE);
                
                send_message ( call->session->messenger, call->friend_id, &msg );
                
                /* If peer changed capabilities during re-call they will 
                 * be handled accordingly during the next step
                 */
            }
            
            /* Only act if capabilities changed */
            if ( call->peer_capabilities != msg->capabilities.value) {
                LOGGER_INFO("Friend is changing capabilities");
                
                call->peer_capabilities = msg->capabilities.value;
                if ( invoke_callback(call, msi_OnCapabilities) == -1 )
                    goto FAILURE;
            }
        } break;
        
        case msi_CallRequesting: {
            LOGGER_INFO("Friend answered our call");
            
            /* Call started */
            call->peer_capabilities = msg->capabilities.value;
            call->state = msi_CallActive;
            
            if ( invoke_callback(call, msi_OnStart) == -1 )
                goto FAILURE;
            
        } break;
        
        case msi_CallRequested: {
            /* Consecutive pushes during initialization state are ignored */
            LOGGER_WARNING("Consecutive push");
        } break;
    }
    
    return;
    
FAILURE:
    send_error(call->session->messenger, call->friend_id, call->error);
    kill_call(call);
}
void handle_pop ( MSICall *call, const MSIMessage *msg )
{
    assert(call);
    
    LOGGER_DEBUG("Session: %p Handling 'pop', friend id: %d", call->session, call->friend_id);
    
    /* callback errors are ignored */
    
    if (msg->error.exists) {
        LOGGER_WARNING("Friend detected an error: %d", msg->error.value);
        call->error = msg->error.value;
        invoke_callback(call, msi_OnError);
        
    } else switch (call->state) {
        case msi_CallInactive: {
            LOGGER_ERROR("Handling what should be impossible case");
            abort();
        } break;
        
        case msi_CallActive: {
            /* Hangup */
            LOGGER_INFO("Friend hung up on us");
            invoke_callback(call, msi_OnEnd);
        } break;
        
        case msi_CallRequesting: {
            /* Reject */
            LOGGER_INFO("Friend rejected our call");
            invoke_callback(call, msi_OnEnd);
        } break;
        
        case msi_CallRequested: {
            /* Cancel */
            LOGGER_INFO("Friend canceled call invite");
            invoke_callback(call, msi_OnEnd);
        } break;
    }
    
    kill_call ( call );
}
void handle_msi_packet ( Messenger *m, int friend_id, const uint8_t *data, uint16_t length, void *object )
{
    LOGGER_DEBUG("Got msi message");
    
    MSISession *session = object;
    MSIMessage msg;
    
    if ( msg_parse_in ( &msg, data, length ) == -1 ) {
        LOGGER_WARNING("Error parsing message");
        send_error(m, friend_id, msi_EInvalidMessage);
        return;
    } else {
        LOGGER_DEBUG("Successfully parsed message");
    }
    
    pthread_mutex_lock(session->mutex);
    MSICall *call = get_call(session, friend_id);
    
    if (call == NULL) {
        if (msg.request.value != requ_push) {
            send_error(m, friend_id, msi_EStrayMessage);
            pthread_mutex_unlock(session->mutex);
            return;
        }
        
        call = new_call(session, friend_id);
        if (call == NULL) {
            send_error(m, friend_id, msi_ESystem);
            pthread_mutex_unlock(session->mutex);
            return;
        }
    }
    
    if (msg.request.value == requ_push)
        handle_push(call, &msg);
    else
        handle_pop(call, &msg); /* always kills the call */
    
    pthread_mutex_unlock(session->mutex);
}