package internet

import (
	"context"
	"syscall"
	"time"

	"v2ray.com/core/common/net"
	"v2ray.com/core/common/session"
)

var (
	effectiveSystemDialer SystemDialer = &DefaultSystemDialer{}
)

type SystemDialer interface {
	Dial(ctx context.Context, source net.Address, destination net.Destination, sockopt *SocketConfig) (net.Conn, error)
}

type DefaultSystemDialer struct {
	controllers []controller
}

func (d *DefaultSystemDialer) Dial(ctx context.Context, src net.Address, dest net.Destination, sockopt *SocketConfig) (net.Conn, error) {
	dialer := &net.Dialer{
		Timeout:   time.Second * 60,
		DualStack: true,
	}

	if sockopt != nil || len(d.controllers) > 0 {
		dialer.Control = func(network, address string, c syscall.RawConn) error {
			return c.Control(func(fd uintptr) {
				if sockopt != nil {
					if err := applyOutboundSocketOptions(network, address, fd, sockopt); err != nil {
						newError("failed to apply socket options").Base(err).WriteToLog(session.ExportIDToError(ctx))
					}
					if dest.Network == net.Network_UDP && len(sockopt.BindAddress) > 0 && sockopt.BindPort > 0 {
						if err := bindAddr(fd, sockopt.BindAddress, sockopt.BindPort); err != nil {
							newError("failed to bind source address to ", sockopt.BindAddress).Base(err).WriteToLog(session.ExportIDToError(ctx))
						}
					}
				}

				for _, ctl := range d.controllers {
					if err := ctl(network, address, fd); err != nil {
						newError("failed to apply external controller").Base(err).WriteToLog(session.ExportIDToError(ctx))
					}
				}
			})
		}
	}

	if src != nil && src != net.AnyIP {
		var addr net.Addr
		if dest.Network == net.Network_TCP {
			addr = &net.TCPAddr{
				IP:   src.IP(),
				Port: 0,
			}
		} else {
			addr = &net.UDPAddr{
				IP:   src.IP(),
				Port: 0,
			}
		}
		dialer.LocalAddr = addr
	}
	return dialer.DialContext(ctx, dest.Network.SystemString(), dest.NetAddr())
}

type SystemDialerAdapter interface {
	Dial(network string, address string) (net.Conn, error)
}

type SimpleSystemDialer struct {
	adapter SystemDialerAdapter
}

func WithAdapter(dialer SystemDialerAdapter) SystemDialer {
	return &SimpleSystemDialer{
		adapter: dialer,
	}
}

func (v *SimpleSystemDialer) Dial(ctx context.Context, src net.Address, dest net.Destination, sockopt *SocketConfig) (net.Conn, error) {
	return v.adapter.Dial(dest.Network.SystemString(), dest.NetAddr())
}

// UseAlternativeSystemDialer replaces the current system dialer with a given one.
// Caller must ensure there is no race condition.
//
// v2ray:api:stable
func UseAlternativeSystemDialer(dialer SystemDialer) {
	if dialer == nil {
		effectiveSystemDialer = &DefaultSystemDialer{}
	}
	effectiveSystemDialer = dialer
}

// RegisterDialerController adds a controller to the effective system dialer.
// The controller can be used to operate on file descriptors before they are put into use.
// It only works when effective dialer is the default dialer.
//
// v2ray:api:beta
func RegisterDialerController(ctl func(network, address string, fd uintptr) error) error {
	if ctl == nil {
		return newError("nil listener controller")
	}

	dialer, ok := effectiveSystemDialer.(*DefaultSystemDialer)
	if !ok {
		return newError("RegisterListenerController not supported in custom dialer")
	}

	dialer.controllers = append(dialer.controllers, ctl)
	return nil
}