package internet

import (
	"log/slog"
	"net"

	"github.com/soypat/lneto"
	"github.com/soypat/lneto/internal"
	"github.com/soypat/lneto/udp"
)

type StackUDPPort struct {
	h      node
	vld    lneto.Validator
	rmport uint16
	raddr  []byte
}

func (sudp *StackUDPPort) SetStackNode(node lneto.StackNode, raddr []byte, rmport uint16) {
	sudp.h = nodeFromStackNode(node, node.LocalPort(), node.Protocol(), raddr)
	sudp.rmport = rmport
	sudp.raddr = append(sudp.raddr[:0], raddr...)
}

func (sudp *StackUDPPort) Protocol() uint64 { return uint64(lneto.IPProtoUDP) }

func (sudp *StackUDPPort) LocalPort() uint16 { return sudp.h.lport }

func (sudp *StackUDPPort) ConnectionID() *uint64 { return sudp.h.connID }

func (sudp *StackUDPPort) Demux(carrierData []byte, frameOffset int) error {
	if sudp.h.IsInvalid() {
		sudp.h.destroy()
		return net.ErrClosed
	}
	ufrm, err := udp.NewFrame(carrierData[frameOffset:])
	if err != nil {
		return err
	}
	ufrm.ValidateSize(&sudp.vld)
	if sudp.vld.HasError() {
		return sudp.vld.ErrPop()
	}
	dst := ufrm.DestinationPort()
	if dst != sudp.h.lport {
		return lneto.ErrPacketDrop // Not meant for us.
	}
	if len(sudp.raddr) > 0 && !internal.IsMulticastIPAddr(sudp.raddr) {
		srcIP, _, _, _, err := internal.GetIPAddr(carrierData[:frameOffset])
		if err != nil {
			return err
		}
		if !internal.BytesEqual(srcIP, sudp.raddr) {
			return lneto.ErrPacketDrop
		}
	}

	src := ufrm.SourcePort()
	if sudp.rmport != 0 && src != sudp.rmport {
		return lneto.ErrPacketDrop // Not from our target remote port.
	}
	err = sudp.h.callbacks.Demux(carrierData, frameOffset+8)
	if err != nil {
		if checkNodeErr(&sudp.h, err) {
			sudp.h.destroy()
		}
		internal.LogAttrs(nil, slog.LevelError, "stackudp:demux", slog.String("err", err.Error()))
	}
	return err
}

func (sudp *StackUDPPort) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (int, error) {
	if sudp.h.IsInvalid() {
		sudp.h.destroy()
		return 0, net.ErrClosed
	}
	ufrm, err := udp.NewFrame(carrierData[offsetToFrame:])
	if err != nil {
		return 0, err
	}
	ufrm.SetSourcePort(sudp.h.lport)
	ufrm.SetDestinationPort(sudp.rmport)
	if len(sudp.raddr) > 0 && offsetToIP >= 0 {
		err = internal.SetIPAddrs(carrierData[offsetToIP:], 0, nil, sudp.raddr)
		if err != nil {
			return 0, err
		}
	}
	// Child payload starts 8 bytes after UDP header start.
	n, err := sudp.h.callbacks.Encapsulate(carrierData, offsetToIP, offsetToFrame+8)
	if n == 0 {
		if err != nil {
			internal.LogAttrs(nil, slog.LevelError, "stackudp:encapsulate", slog.String("err", err.Error()))
		}
		return 0, err
	}
	// UDP CRC and length left to IP layer.
	length := 8 + n
	return length, err
}