package chain

import (
	"context"
	"errors"
	"fmt"
	"net"

	"github.com/go-gost/gost/pkg/common/util/udp"
	"github.com/go-gost/gost/pkg/connector"
	"github.com/go-gost/gost/pkg/logger"
)

var (
	ErrEmptyRoute = errors.New("empty route")
)

type route struct {
	nodes []*Node
}

func (r *route) AddNode(node *Node) {
	r.nodes = append(r.nodes, node)
}

func (r *route) connect(ctx context.Context) (conn net.Conn, err error) {
	if r.IsEmpty() {
		return nil, ErrEmptyRoute
	}

	node := r.nodes[0]
	cc, err := node.transport.Dial(ctx, r.nodes[0].Addr())
	if err != nil {
		node.Marker().Mark()
		return
	}

	cn, err := node.transport.Handshake(ctx, cc)
	if err != nil {
		cc.Close()
		node.Marker().Mark()
		return
	}
	node.Marker().Reset()

	preNode := node
	for _, node := range r.nodes[1:] {
		cc, err = preNode.transport.Connect(ctx, cn, "tcp", node.Addr())
		if err != nil {
			cn.Close()
			node.Marker().Mark()
			return
		}
		cc, err = node.transport.Handshake(ctx, cc)
		if err != nil {
			cn.Close()
			node.Marker().Mark()
			return
		}
		node.Marker().Reset()

		cn = cc
		preNode = node
	}

	conn = cn
	return
}

func (r *route) Dial(ctx context.Context, network, address string) (net.Conn, error) {
	if r.IsEmpty() {
		return r.dialDirect(ctx, network, address)
	}

	conn, err := r.connect(ctx)
	if err != nil {
		return nil, err
	}

	cc, err := r.Last().transport.Connect(ctx, conn, network, address)
	if err != nil {
		conn.Close()
		return nil, err
	}
	return cc, nil
}

func (r *route) dialDirect(ctx context.Context, network, address string) (net.Conn, error) {
	switch network {
	case "udp", "udp4", "udp6":
		if address == "" {
			return net.ListenUDP(network, nil)
		}
	default:
	}

	d := net.Dialer{}
	return d.DialContext(ctx, network, address)
}

func (r *route) Bind(ctx context.Context, network, address string, opts ...connector.BindOption) (net.Listener, error) {
	if r.IsEmpty() {
		return r.bindLocal(ctx, network, address, opts...)
	}

	conn, err := r.connect(ctx)
	if err != nil {
		return nil, err
	}

	ln, err := r.Last().transport.Bind(ctx, conn, network, address, opts...)
	if err != nil {
		conn.Close()
		return nil, err
	}

	return ln, nil
}

func (r *route) IsEmpty() bool {
	return r == nil || len(r.nodes) == 0
}

func (r *route) Last() *Node {
	if r.IsEmpty() {
		return nil
	}
	return r.nodes[len(r.nodes)-1]
}

func (r *route) Path() (path []*Node) {
	if r == nil || len(r.nodes) == 0 {
		return nil
	}

	for _, node := range r.nodes {
		if node.transport != nil && node.transport.route != nil {
			path = append(path, node.transport.route.Path()...)
		}
		path = append(path, node)
	}
	return
}

func (r *route) bindLocal(ctx context.Context, network, address string, opts ...connector.BindOption) (net.Listener, error) {
	options := connector.BindOptions{}
	for _, opt := range opts {
		opt(&options)
	}

	switch network {
	case "tcp", "tcp4", "tcp6":
		addr, err := net.ResolveTCPAddr(network, address)
		if err != nil {
			return nil, err
		}
		return net.ListenTCP(network, addr)
	case "udp", "udp4", "udp6":
		addr, err := net.ResolveUDPAddr(network, address)
		if err != nil {
			return nil, err
		}
		conn, err := net.ListenUDP(network, addr)
		if err != nil {
			return nil, err
		}
		logger := logger.Default().WithFields(map[string]interface{}{
			"network": network,
			"address": address,
		})
		ln := udp.NewListener(conn, addr,
			options.Backlog, options.UDPDataQueueSize, options.UDPDataBufferSize,
			options.UDPConnTTL, logger)
		return ln, err
	default:
		err := fmt.Errorf("network %s unsupported", network)
		return nil, err
	}
}