/*
  UdpContext.h - UDP connection handling on top of lwIP

  Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
  This file is part of the esp8266 core for Arduino environment.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
#ifndef UDPCONTEXT_H
#define UDPCONTEXT_H

class UdpContext;

extern "C" {
void esp_yield();
void esp_schedule();
#include "lwip/init.h" // LWIP_VERSION_
#include <assert.h>
}

#define GET_UDP_HDR(pb) (reinterpret_cast<udp_hdr*>(((uint8_t*)((pb)->payload)) - UDP_HLEN))

class UdpContext
{
public:

    typedef std::function<void(void)> rxhandler_t;

    UdpContext()
    : _pcb(0)
    , _rx_buf(0)
    , _first_buf_taken(false)
    , _rx_buf_offset(0)
    , _refcnt(0)
    , _tx_buf_head(0)
    , _tx_buf_cur(0)
    , _tx_buf_offset(0)
    {
        _pcb = udp_new();
#ifdef LWIP_MAYBE_XCC
        _mcast_ttl = 1;
#endif
    }

    ~UdpContext()
    {
        udp_remove(_pcb);
        _pcb = 0;
        if (_tx_buf_head)
        {
            pbuf_free(_tx_buf_head);
            _tx_buf_head = 0;
            _tx_buf_cur = 0;
            _tx_buf_offset = 0;
        }
        if (_rx_buf)
        {
            pbuf_free(_rx_buf);
            _rx_buf = 0;
            _rx_buf_offset = 0;
        }
    }

    void ref()
    {
        ++_refcnt;
    }

    void unref()
    {
        if(this != 0) {
            DEBUGV(":ur %d\r\n", _refcnt);
            if(--_refcnt == 0) {
                delete this;
            }
        }
    }

    bool connect(const ip_addr_t* addr, uint16_t port)
    {
        _pcb->remote_ip = *addr;
        _pcb->remote_port = port;
        return true;
    }

    bool listen(CONST ip_addr_t* addr, uint16_t port)
    {
        udp_recv(_pcb, &_s_recv, (void *) this);
        err_t err = udp_bind(_pcb, addr, port);
        return err == ERR_OK;
    }

    void disconnect()
    {
        udp_disconnect(_pcb);
    }

    void setMulticastInterface(const IPAddress& addr)
    {
#if LWIP_VERSION_MAJOR == 1
        udp_set_multicast_netif_addr(_pcb, (ip_addr_t)addr);
#else
        udp_set_multicast_netif_addr(_pcb, ip_2_ip4((const ip_addr_t*)addr));
#endif
    }

    void setMulticastTTL(int ttl)
    {
#ifdef LWIP_MAYBE_XCC
        _mcast_ttl = ttl;
#else
        udp_set_multicast_ttl(_pcb, ttl);
#endif
    }

    // warning: handler is called from tcp stack context
    // esp_yield and non-reentrant functions which depend on it will fail
    void onRx(rxhandler_t handler) {
        _on_rx = handler;
    }

    size_t getSize() const
    {
        if (!_rx_buf)
            return 0;

        return _rx_buf->len - _rx_buf_offset;
    }

    size_t tell() const
    {
        return _rx_buf_offset;
    }

    void seek(const size_t pos)
    {
        assert(isValidOffset(pos));
        _rx_buf_offset = pos;
    }

    bool isValidOffset(const size_t pos) const {
        return (pos <= _rx_buf->len);
    }

    CONST IPAddress& getRemoteAddress() CONST
    {
        return _src_addr;
    }

    uint16_t getRemotePort() const
    {
        if (!_rx_buf)
            return 0;

        udp_hdr* udphdr = GET_UDP_HDR(_rx_buf);
        return lwip_ntohs(udphdr->src);
    }

    const IPAddress& getDestAddress() const
    {
        return _dst_addr;
    }

    uint16_t getLocalPort() const
    {
        if (!_pcb)
            return 0;
        return _pcb->local_port;
    }

    bool next()
    {
        if (!_rx_buf)
            return false;

        if (!_first_buf_taken)
        {
            _first_buf_taken = true;
            return true;
        }

        auto head = _rx_buf;
        _rx_buf = _rx_buf->next;
        _rx_buf_offset = 0;

        if (_rx_buf)
        {
            pbuf_ref(_rx_buf);
        }
        pbuf_free(head);
        return _rx_buf != 0;
    }

    int read()
    {
        if (!_rx_buf || _rx_buf_offset >= _rx_buf->len)
            return -1;

        char c = reinterpret_cast<char*>(_rx_buf->payload)[_rx_buf_offset];
        _consume(1);
        return c;
    }

    size_t read(char* dst, size_t size)
    {
        if (!_rx_buf)
            return 0;

        size_t max_size = _rx_buf->len - _rx_buf_offset;
        size = (size < max_size) ? size : max_size;
        DEBUGV(":urd %d, %d, %d\r\n", size, _rx_buf->len, _rx_buf_offset);

        memcpy(dst, reinterpret_cast<char*>(_rx_buf->payload) + _rx_buf_offset, size);
        _consume(size);

        return size;
    }

    int peek() const
    {
        if (!_rx_buf || _rx_buf_offset == _rx_buf->len)
            return -1;

        return reinterpret_cast<char*>(_rx_buf->payload)[_rx_buf_offset];
    }

    void flush()
    {
        //XXX this does not follow Arduino's flush definition
        if (!_rx_buf)
            return;

        _consume(_rx_buf->len - _rx_buf_offset);
    }

    size_t append(const char* data, size_t size)
    {
        if (!_tx_buf_head || _tx_buf_head->tot_len < _tx_buf_offset + size)
        {
            _reserve(_tx_buf_offset + size);
        }
        if (!_tx_buf_head || _tx_buf_head->tot_len < _tx_buf_offset + size)
        {
            DEBUGV("failed _reserve");
            return 0;
        }

        size_t left_to_copy = size;
        while(left_to_copy)
        {
            // size already used in current pbuf
            size_t used_cur = _tx_buf_offset - (_tx_buf_head->tot_len - _tx_buf_cur->tot_len);
            size_t free_cur = _tx_buf_cur->len - used_cur;
            if (free_cur == 0)
            {
                _tx_buf_cur = _tx_buf_cur->next;
                continue;
            }
            size_t will_copy = (left_to_copy < free_cur) ? left_to_copy : free_cur;
            memcpy(reinterpret_cast<char*>(_tx_buf_cur->payload) + used_cur, data, will_copy);
            _tx_buf_offset += will_copy;
            left_to_copy -= will_copy;
            data += will_copy;
        }
        return size;
    }

    bool send(CONST ip_addr_t* addr = 0, uint16_t port = 0)
    {
        size_t data_size = _tx_buf_offset;
        pbuf* tx_copy = pbuf_alloc(PBUF_TRANSPORT, data_size, PBUF_RAM);
        if(!tx_copy){
            DEBUGV("failed pbuf_alloc");
        }
        else{
            uint8_t* dst = reinterpret_cast<uint8_t*>(tx_copy->payload);
            for (pbuf* p = _tx_buf_head; p; p = p->next) {
                size_t will_copy = (data_size < p->len) ? data_size : p->len;
                memcpy(dst, p->payload, will_copy);
                dst += will_copy;
                data_size -= will_copy;
            }
        }
        if (_tx_buf_head)
            pbuf_free(_tx_buf_head);
        _tx_buf_head = 0;
        _tx_buf_cur = 0;
        _tx_buf_offset = 0;
        if(!tx_copy){
            return false;
        }


        if (!addr) {
            addr = &_pcb->remote_ip;
            port = _pcb->remote_port;
        }
#ifdef LWIP_MAYBE_XCC
        uint16_t old_ttl = _pcb->ttl;
        if (ip_addr_ismulticast(addr)) {
            _pcb->ttl = _mcast_ttl;
        }
#endif
        err_t err = udp_sendto(_pcb, tx_copy, addr, port);
        if (err != ERR_OK) {
            DEBUGV(":ust rc=%d\r\n", (int) err);
        }
#ifdef LWIP_MAYBE_XCC
        _pcb->ttl = old_ttl;
#endif
        pbuf_free(tx_copy);
        return err == ERR_OK;
    }

private:

    void _reserve(size_t size)
    {
        const size_t pbuf_unit_size = 128;
        if (!_tx_buf_head)
        {
            _tx_buf_head = pbuf_alloc(PBUF_TRANSPORT, pbuf_unit_size, PBUF_RAM);
            if (!_tx_buf_head)
            {
                return;
            }
            _tx_buf_cur = _tx_buf_head;
            _tx_buf_offset = 0;
        }

        size_t cur_size = _tx_buf_head->tot_len;
        if (size < cur_size)
            return;

        size_t grow_size = size - cur_size;

        while(grow_size)
        {
            pbuf* pb = pbuf_alloc(PBUF_TRANSPORT, pbuf_unit_size, PBUF_RAM);
            if (!pb)
            {
                return;
            }
            pbuf_cat(_tx_buf_head, pb);
            if (grow_size < pbuf_unit_size)
                return;
            grow_size -= pbuf_unit_size;
        }
    }

    void _consume(size_t size)
    {
        _rx_buf_offset += size;
        if (_rx_buf_offset > _rx_buf->len) {
            _rx_buf_offset = _rx_buf->len;
        }
    }

    void _recv(udp_pcb *upcb, pbuf *pb,
            const ip_addr_t *addr, u16_t port)
    {
        (void) upcb;
        (void) addr;
        (void) port;
        if (_rx_buf)
        {
            // there is some unread data
            // chain the new pbuf to the existing one
            DEBUGV(":urch %d, %d\r\n", _rx_buf->tot_len, pb->tot_len);
            pbuf_cat(_rx_buf, pb);
        }
        else
        {
            DEBUGV(":urn %d\r\n", pb->tot_len);
            _first_buf_taken = false;
            _rx_buf = pb;
            _rx_buf_offset = 0;
        }

        // --> Arduino's UDP is a stream but UDP is not <--
        // When IPv6 is enabled, we store addresses from here
        // because lwIP's macro are valid only in this callback
        // (there's no easy way to safely guess whether packet
        //  is from v4 or v6 when we have only access to payload)
        // Because of this stream-ed way this is inacurate when
        // user does not swallow data quickly enough (the former
        // IPv4-only way suffers from the exact same issue.

#if LWIP_VERSION_MAJOR == 1
        _src_addr = current_iphdr_src;
        _dst_addr = current_iphdr_dest;
#else
        _src_addr = ip_data.current_iphdr_src;
        _dst_addr = ip_data.current_iphdr_dest;
#endif

        if (_on_rx) {
            _on_rx();
        }
    }


    static void _s_recv(void *arg,
            udp_pcb *upcb, pbuf *p,
            CONST ip_addr_t *addr, u16_t port)
    {
        reinterpret_cast<UdpContext*>(arg)->_recv(upcb, p, addr, port);
    }

private:
    udp_pcb* _pcb;
    pbuf* _rx_buf;
    bool _first_buf_taken;
    size_t _rx_buf_offset;
    int _refcnt;
    pbuf* _tx_buf_head;
    pbuf* _tx_buf_cur;
    size_t _tx_buf_offset;
    rxhandler_t _on_rx;
#ifdef LWIP_MAYBE_XCC
    uint16_t _mcast_ttl;
#endif
    IPAddress _src_addr, _dst_addr;
};



#endif//UDPCONTEXT_H