#include "tcp_connection.hh"

#include <iostream>

// Dummy implementation of a TCP connection

// For Lab 4, please replace with a real implementation that passes the
// automated checks run by `make check`.

template <typename... Targs>
void DUMMY_CODE(Targs &&.../* unused */) {}

using namespace std;

size_t TCPConnection::remaining_outbound_capacity() const { return _sender.stream_in().remaining_capacity(); }

size_t TCPConnection::bytes_in_flight() const { return _sender.bytes_in_flight(); }

size_t TCPConnection::unassembled_bytes() const { return _receiver.unassembled_bytes(); }

size_t TCPConnection::time_since_last_segment_received() const { return _time_last_segment_received; }

void TCPConnection::segment_received(const TCPSegment &seg) {
    // god knows whether it should be active or not initially
    _time_last_segment_received = 0;
    if (seg.header().rst) {
        _set_rst();
        return;
    }
    _receiver.segment_received(seg);
    if (seg.header().ack && _receiver.ackno().has_value()) {
        // filter out acks before syn
        _sender.ack_received(seg.header().ackno, seg.header().win);
        // _sender.fill_window(); !! This should be done in ack_received
    }
    // if the inbound seg has len it should be responded
    //  except that ack_received() has send a seg, so no more is needed
    // Keep-alive is suggested in RFC1122, but it is optional, though implemented here
    if ((seg.length_in_sequence_space() ||
         (_receiver.ackno().has_value() && seg.header().seqno == _receiver.ackno().value() - 1)) &&
        _sender.segments_out().empty()) {
        _sender.fill_window();  // it is necessary to repond to SYN with a SYNACK
        if (_sender.segments_out().empty()) {
            _sender.send_empty_segment();
        }
    }
    _send_all();
    // recver in FIN_RECV
    // sender in SYN_ACKED
    if (_receiver.stream_out().input_ended() &&
        (!_sender.stream_in().eof() || _sender.next_seqno_absolute() < _sender.stream_in().bytes_written() + 2)) {
        _linger_after_streams_finish = false;
    }
}

bool TCPConnection::active() const { return _active; }

size_t TCPConnection::write(const string &data) {
    auto &stream_in = _sender.stream_in();
    auto wr_sz = stream_in.write(data);
    _sender.fill_window();
    _send_all();
    return wr_sz;
}

//! \param[in] ms_since_last_tick number of milliseconds since the last call to this method
void TCPConnection::tick(const size_t ms_since_last_tick) {
    _time_last_segment_received += ms_since_last_tick;
    _sender.tick(ms_since_last_tick);
    if (_sender.consecutive_retransmissions() > TCPConfig::MAX_RETX_ATTEMPTS) {
        _send_rst();
        _set_rst();
        return;
    }
    _send_all();
    // actually, this long if could be represented by TCP states
    // for sender, it is the FIN_ACKED state
    // for recver, it is the FIN_RECV state
    // and plus linger
    if ((!_sender.bytes_in_flight() && _sender.stream_in().eof() &&
         _sender.next_seqno_absolute() == _sender.stream_in().bytes_written() + 2) &&
        (_receiver.stream_out().input_ended()) &&
        (!_linger_after_streams_finish || _time_last_segment_received >= 10 * _cfg.rt_timeout)) {
        _active = false;
    }
}

void TCPConnection::end_input_stream() {
    _sender.stream_in().end_input();
    _sender.fill_window();
    _send_all();
}

void TCPConnection::connect() {
    _sender.fill_window();
    _send_all();
}

TCPConnection::~TCPConnection() {
    try {
        if (active()) {
            cerr << "Warning: Unclean shutdown of TCPConnection\n";
            _send_rst();
            _set_rst();
            // Your code here: need to send a RST segment to the peer
        }
    } catch (const exception &e) {
        std::cerr << "Exception destructing TCP FSM: " << e.what() << std::endl;
    }
}