/*
 * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
 */

#include <cstdlib>
#include <cstdio>
#include <cassert>
#include <algorithm>
#include <uavcan/internal/debug.hpp>
#include <uavcan/internal/transport/transfer_receiver.hpp>

namespace uavcan
{

const uint32_t TransferReceiver::DEFAULT_TRANSFER_INTERVAL;
const uint32_t TransferReceiver::MIN_TRANSFER_INTERVAL;
const uint32_t TransferReceiver::MAX_TRANSFER_INTERVAL;

void TransferReceiver::cleanup()
{
    if (bufmgr_ != NULL && !bufmgr_key_.isEmpty())
        bufmgr_->remove(bufmgr_key_);
}

TransferReceiver::TidRelation TransferReceiver::getTidRelation(const RxFrame& frame) const
{
    const int distance = tid_.forwardDistance(frame.transfer_id);
    if (distance == 0)
        return TID_SAME;
    if (distance < ((1 << TransferID::BITLEN) / 2))
        return TID_FUTURE;
    return TID_REPEAT;
}

void TransferReceiver::updateTransferTimings()
{
    assert(this_transfer_ts_monotonic_ > 0);

    const uint64_t prev_prev_ts = prev_transfer_ts_monotonic_;
    prev_transfer_ts_monotonic_ = this_transfer_ts_monotonic_;

    if ((prev_prev_ts != 0) &&
        (prev_transfer_ts_monotonic_ != 0) &&
        (prev_transfer_ts_monotonic_ >= prev_prev_ts))
    {
        uint64_t interval = prev_transfer_ts_monotonic_ - prev_prev_ts;
        interval = std::max(std::min(interval, uint64_t(MAX_TRANSFER_INTERVAL)), uint64_t(MIN_TRANSFER_INTERVAL));
        transfer_interval_ = static_cast<uint32_t>((uint64_t(transfer_interval_) * 7 + interval) / 8);
    }
}

void TransferReceiver::prepareForNextTransfer()
{
    tid_.increment();
    next_frame_index_ = 0;
}

bool TransferReceiver::validate(const RxFrame& frame) const
{
    if (iface_index_ != frame.iface_index)
        return false;

    if (frame.source_node_id == 0)
    {
        UAVCAN_TRACE("TransferReceiver", "Invalid frame NID, %s", frame.toString().c_str());
        return false;
    }

    if (frame.frame_index != next_frame_index_)
    {
        UAVCAN_TRACE("TransferReceiver", "Unexpected frame index, %s", frame.toString().c_str());
        return false;
    }

    if (!frame.last_frame && frame.payload_len != Frame::PAYLOAD_LEN_MAX)
    {
        UAVCAN_TRACE("TransferReceiver", "Unexpected payload len, %s", frame.toString().c_str());
        return false;
    }

    if (!frame.last_frame && frame.frame_index == Frame::FRAME_INDEX_MAX)
    {
        UAVCAN_TRACE("TransferReceiver", "Expected end of transfer, %s", frame.toString().c_str());
        return false;
    }

    if (getTidRelation(frame) != TID_SAME)
    {
        UAVCAN_TRACE("TransferReceiver", "Unexpected TID, %s", frame.toString().c_str());
        return false;
    }
    return true;
}

TransferReceiver::ResultCode TransferReceiver::receive(const RxFrame& frame)
{
    if (frame.frame_index == 0)
    {
        this_transfer_ts_monotonic_ = frame.ts_monotonic;
        first_frame_ts_utc_ = frame.ts_utc;
    }

    if ((frame.frame_index == 0) && frame.last_frame)  // Single-frame transfer
    {
        bufmgr_->remove(bufmgr_key_);
        updateTransferTimings();
        prepareForNextTransfer();
        return RESULT_SINGLE_FRAME;
    }

    TransferBufferBase* buf = bufmgr_->access(bufmgr_key_);
    if (buf == NULL)
        buf = bufmgr_->create(bufmgr_key_);
    if (buf == NULL)
    {
        UAVCAN_TRACE("TransferReceiver", "Failed to access the buffer, %s", frame.toString().c_str());
        prepareForNextTransfer();
        return RESULT_NOT_COMPLETE;
    }

    const int res = buf->write(Frame::PAYLOAD_LEN_MAX * frame.frame_index, frame.payload, frame.payload_len);
    if (res != frame.payload_len)
    {
        UAVCAN_TRACE("TransferReceiver", "Buffer write failure [%i], %s", res, frame.toString().c_str());
        bufmgr_->remove(bufmgr_key_);
        prepareForNextTransfer();
        return RESULT_NOT_COMPLETE;
    }
    next_frame_index_++;

    if (frame.last_frame)
    {
        updateTransferTimings();
        prepareForNextTransfer();
        return RESULT_COMPLETE;
    }
    return RESULT_NOT_COMPLETE;
}

bool TransferReceiver::isTimedOut(uint64_t timestamp) const
{
    static const uint64_t INTERVAL_MULT = (1 << TransferID::BITLEN) / 2 - 1;
    const uint64_t ts = this_transfer_ts_monotonic_;
    if (timestamp <= ts)
        return false;
    return (timestamp - ts) > (uint64_t(transfer_interval_) * INTERVAL_MULT);
}

TransferReceiver::ResultCode TransferReceiver::addFrame(const RxFrame& frame)
{
    assert(bufmgr_);
    assert(bufmgr_key_.getNodeID() == frame.source_node_id);
    assert(bufmgr_key_.getTransferType() == frame.transfer_type);

    if ((frame.ts_monotonic == 0) ||
        (frame.ts_monotonic < prev_transfer_ts_monotonic_) ||
        (frame.ts_monotonic < this_transfer_ts_monotonic_))
    {
        return RESULT_NOT_COMPLETE;
    }

    const bool not_initialized = !isInitialized();
    const bool iface_timed_out = (frame.ts_monotonic - this_transfer_ts_monotonic_) > (uint64_t(transfer_interval_) * 2);
    const bool receiver_timed_out = isTimedOut(frame.ts_monotonic);
    const bool same_iface = frame.iface_index == iface_index_;
    const bool first_fame = frame.frame_index == 0;
    const TidRelation tid_rel = getTidRelation(frame);

    const bool need_restart = // FSM, the hard way
        (not_initialized) ||
        (receiver_timed_out) ||
        (same_iface && first_fame && (tid_rel == TID_FUTURE)) ||
        (iface_timed_out && first_fame && (tid_rel == TID_FUTURE));

    if (need_restart)
    {
        UAVCAN_TRACE("TransferReceiver",
            "Restart [not_inited=%i, iface_timeout=%i, recv_timeout=%i, same_iface=%i, first_frame=%i, tid_rel=%i], %s",
            int(not_initialized), int(iface_timed_out), int(receiver_timed_out), int(same_iface), int(first_fame),
            int(tid_rel), frame.toString().c_str());
        bufmgr_->remove(bufmgr_key_);
        iface_index_ = frame.iface_index;
        tid_ = frame.transfer_id;
        next_frame_index_ = 0;
        if (!first_fame)
        {
            tid_.increment();
            return RESULT_NOT_COMPLETE;
        }
    }

    if (!validate(frame))
        return RESULT_NOT_COMPLETE;

    return receive(frame);
}

}