/*
  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 <assert.h>
}

#include <AddrList.h>
#include <PolledTimeout.h>

#define PBUF_ALIGNER_ADJUST 4
#define PBUF_ALIGNER(x) ((void*)((((intptr_t)(x))+3)&~3))
#define PBUF_HELPER_FLAG 0xff // lwIP pbuf flag: u8_t

class UdpContext
{
public:

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

    UdpContext()
    : _pcb(0)
    , _rx_buf(0)
    , _first_buf_taken(false)
    , _rx_buf_offset(0)
    , _rx_buf_size(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;
            _rx_buf_size = 0;
        }
    }

    void ref()
    {
        ++_refcnt;
    }

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

    bool connect(const IPAddress& addr, uint16_t port)
    {
        _pcb->remote_ip = addr;
        _pcb->remote_port = port;
#if LWIP_IPV6
        // Set zone so that link local addresses use the default interface
        if (IP_IS_V6(&_pcb->remote_ip) && ip6_addr_lacks_zone(ip_2_ip6(&_pcb->remote_ip), IP6_UNKNOWN)) {
            ip6_addr_assign_zone(ip_2_ip6(&_pcb->remote_ip), IP6_UNKNOWN, netif_default);
        }
#endif
        return true;
    }

    bool listen(const IPAddress& 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);
    }

#if LWIP_IPV6

    void setMulticastInterface(IPAddress addr)
    {
        // Per 'udp_set_multicast_netif_addr()' signature and comments
        // in lwIP sources:
        // An IPv4 address designating a specific interface must be used.
        // When an IPv6 address is given, the matching IPv4 in the same
        // interface must be selected.

        if (!addr.isV4())
        {
            for (auto a: addrList)
                if (a.addr() == addr)
                {
                    // found the IPv6 address,
                    // redirect parameter to IPv4 address in this interface
                    addr = a.ipv4();
                    break;
                }
            assert(addr.isV4());
        }
        udp_set_multicast_netif_addr(_pcb, ip_2_ip4((const ip_addr_t*)addr));
    }

#else // !LWIP_IPV6

    void setMulticastInterface(const IPAddress& addr)
    {
        udp_set_multicast_netif_addr(_pcb, ip_2_ip4((const ip_addr_t*)addr));
    }

#endif // !LWIP_IPV6

    /*
     * Add a netif (by its index) as the multicast interface
     */
    void setMulticastInterface(netif* p_pNetIf)
    {
        udp_set_multicast_netif_index(_pcb, (p_pNetIf ? netif_get_index(p_pNetIf) : NETIF_NO_INDEX));
    }

    /*
     * Allow access to pcb to change eg. options
     */
    udp_pcb* pcb(void)
    {
        return _pcb;
    }

    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;
    }

#ifdef DEBUG_ESP_CORE
    // this helper is ready to be used when debugging UDP
    void printChain (const pbuf* pb, const char* msg, size_t n) const
    {
        // printf the pb pbuf chain, bufferred and all at once
        char buf[128];
        int l = snprintf(buf, sizeof(buf), "UDP: %s %u: ", msg, n);
        while (pb)
        {
            l += snprintf(&buf[l], sizeof(buf) -l, "%p(H=%d,%d<=%d)-",
                pb, pb->flags == PBUF_HELPER_FLAG, pb->len, pb->tot_len);
            pb = pb->next;
        }
        l += snprintf(&buf[l], sizeof(buf) - l, "(end)");
        DEBUGV("%s\n", buf);
    }
#else
    void printChain (const pbuf* pb, const char* msg) const
    {
        (void)pb;
        (void)msg;
    }
#endif

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

        return _rx_buf_size - _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_size);
    }

    netif* getInputNetif() const
    {
        return _currentAddr.input_netif;
    }

    const IPAddress& getRemoteAddress() const
    {
        return _currentAddr.srcaddr;
    }

    uint16_t getRemotePort() const
    {
        return _currentAddr.srcport;
    }

    const IPAddress& getDestAddress() const
    {
        return _currentAddr.dstaddr;
    }

    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;
        }

        // We have interleaved informations on addresses within received pbuf chain:
        // (before ipv6 code we had: (data-pbuf) -> (data-pbuf) -> (data-pbuf) -> ... in the receiving order)
        // Now:         (address-info-pbuf -> chained-data-pbuf [-> chained-data-pbuf...]) ->
        //      (chained-address-info-pbuf -> chained-data-pbuf [-> chained...]) -> ...
        // _rx_buf is currently adressing a data pbuf,
        // in this function it is going to be discarded.

        auto deleteme = _rx_buf;

        // forward in the chain until next address-info pbuf or end of chain
        while(_rx_buf && _rx_buf->flags != PBUF_HELPER_FLAG)
            _rx_buf = _rx_buf->next;

        if (_rx_buf)
        {
            assert(_rx_buf->flags == PBUF_HELPER_FLAG);

            // copy address helper to "current address"
            auto helper = (AddrHelper*)PBUF_ALIGNER(_rx_buf->payload);
            _currentAddr = *helper;

            // destroy the helper in the about-to-be-released pbuf
            helper->~AddrHelper();

            // forward in rx_buf list, next one is effective data
            // current (not ref'ed) one will be pbuf_free'd
            // with the 'deleteme' pointer above
            _rx_buf = _rx_buf->next;

            // this rx_buf is not nullptr by construction,
            assert(_rx_buf);
            // ref'ing it to prevent release from the below pbuf_free(deleteme)
            // (ref counter prevents release and will be decreased by pbuf_free)
            pbuf_ref(_rx_buf);
        }

        // release in chain previous data, and if any:
        // current helper, but not start of current data
        pbuf_free(deleteme);

        _rx_buf_offset = 0;
        _rx_buf_size = _processSize(_rx_buf);
        return _rx_buf != nullptr;
    }

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

        char c = pbuf_get_at(_rx_buf, _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_size - _rx_buf_offset;
        size = (size < max_size) ? size : max_size;
        DEBUGV(":urd %d, %d, %d\r\n", size, _rx_buf_size, _rx_buf_offset);

        void* buf = pbuf_get_contiguous(_rx_buf, dst, size, size, _rx_buf_offset);
        if(!buf)
            return 0;

        if(buf != dst)
            memcpy(dst, buf, size);

        _consume(size);

        return size;
    }

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

        return pbuf_get_at(_rx_buf, _rx_buf_offset);
    }

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

        _consume(_rx_buf_size - _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;
    }

    void cancelBuffer ()
    {
        if (_tx_buf_head)
            pbuf_free(_tx_buf_head);
        _tx_buf_head = 0;
        _tx_buf_cur = 0;
        _tx_buf_offset = 0;
    }

    bool send(const ip_addr_t* addr = 0, uint16_t port = 0)
    {
        return trySend(addr, port, /* don't keep buffer */false) == ERR_OK;
    }

    bool sendTimeout(const ip_addr_t* addr, uint16_t port,
                     esp8266::polledTimeout::oneShotFastMs::timeType timeoutMs)
    {
        err_t err;
        esp8266::polledTimeout::oneShotFastMs timeout(timeoutMs);
        while (((err = trySend(addr, port, /* keep buffer on error */true)) != ERR_OK) && !timeout)
            delay(0);
        if (err != ERR_OK)
            cancelBuffer(); // get rid of buffer kept on error after timeout
        return err == ERR_OK;
    }

private:

    err_t trySend(const ip_addr_t* addr, uint16_t port, bool keepBufferOnError)
    {
        size_t data_size = _tx_buf_offset;
        pbuf* tx_copy = pbuf_alloc(PBUF_TRANSPORT, data_size, PBUF_RAM);
        if (tx_copy) {
            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 (!keepBufferOnError)
            cancelBuffer();

        if (!tx_copy){
            DEBUGV("failed pbuf_alloc");
            return ERR_MEM;
        }

        if (!addr) {
            addr = &_pcb->remote_ip;
            port = _pcb->remote_port;
        }

        err_t err = udp_sendto(_pcb, tx_copy, addr, port);
        if (err != ERR_OK) {
            DEBUGV(":ust rc=%d\r\n", (int) err);
        }

        pbuf_free(tx_copy);

        if (err == ERR_OK)
            cancelBuffer(); // no error: get rid of buffer

        return err;
    }

    size_t _processSize (const pbuf* pb)
    {
        size_t ret = 0;
        for (; pb && pb->flags != PBUF_HELPER_FLAG; pb = pb->next)
            ret += pb->len;
        return ret;
    }

    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_size) {
            _rx_buf_offset = _rx_buf_size;
        }
    }

    void _recv(udp_pcb *upcb, pbuf *pb,
            const ip_addr_t *srcaddr, u16_t srcport)
    {
        (void) upcb;
        // check receive pbuf chain depth
        // optimization path: cache the pbuf chain length
        {
            pbuf* p;
            int count = 0;
            for (p = _rx_buf; p && ++count < rxBufMaxDepth*2; p = p->next);
            if (p)
            {
                // pbuf chain too deep, dropping
                pbuf_free(pb);
                DEBUGV(":udr\r\n");
                return;
            }
        }

        // chain this helper pbuf first
        if (_rx_buf)
        {
            // there is some unread data
            // chain pbuf

            // Addresses/ports are stored from this callback because lwIP's
            // macro are valid only now.
            //
            // When peeking data from before payload start (like it was done
            // before IPv6), there's no easy way to safely guess whether
            // packet is from v4 or v6.
            //
            // Now storing data in an intermediate chained pbuf containing
            // AddrHelper

            // allocate new pbuf to store addresses/ports
            pbuf* pb_helper = pbuf_alloc(PBUF_RAW, sizeof(AddrHelper) + PBUF_ALIGNER_ADJUST, PBUF_RAM);
            if (!pb_helper)
            {
                // memory issue - discard received data
                pbuf_free(pb);
                return;
            }
            // construct in place
            new(PBUF_ALIGNER(pb_helper->payload)) AddrHelper(srcaddr, ip_current_dest_addr(), srcport, ip_current_input_netif());
            pb_helper->flags = PBUF_HELPER_FLAG; // mark helper pbuf
            // chain it
            pbuf_cat(_rx_buf, pb_helper);

            // now chain the new data pbuf
            DEBUGV(":urch %d, %d\r\n", _rx_buf->tot_len, pb->tot_len);
            pbuf_cat(_rx_buf, pb);
        }
        else
        {
            _currentAddr.srcaddr = srcaddr;
            _currentAddr.dstaddr = ip_current_dest_addr();
            _currentAddr.srcport = srcport;
            _currentAddr.input_netif = ip_current_input_netif();

            DEBUGV(":urn %d\r\n", pb->tot_len);
            _first_buf_taken = false;
            _rx_buf = pb;
            _rx_buf_offset = 0;
            _rx_buf_size = pb->tot_len;
        }

        if (_on_rx) {
            _on_rx();
        }

    }

    static void _s_recv(void *arg,
            udp_pcb *upcb, pbuf *p,
            const ip_addr_t *srcaddr, u16_t srcport)
    {
        reinterpret_cast<UdpContext*>(arg)->_recv(upcb, p, srcaddr, srcport);
    }

private:
    udp_pcb* _pcb;
    pbuf* _rx_buf;
    bool _first_buf_taken;
    size_t _rx_buf_offset;
    size_t _rx_buf_size;
    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
    struct AddrHelper
    {
        IPAddress srcaddr, dstaddr;
        int16_t srcport;
        netif* input_netif;

        AddrHelper() { }
        AddrHelper(const ip_addr_t* src, const ip_addr_t* dst, uint16_t srcport, netif* input_netif):
            srcaddr(src), dstaddr(dst), srcport(srcport), input_netif(input_netif) { }
    };
    AddrHelper _currentAddr;

    // rx pbuf depth barrier (counter of buffered UDP received packets)
    // keep it small
    static constexpr int rxBufMaxDepth = 4;
};



#endif//UDPCONTEXT_H
