package fingerprint

import (
	"fmt"
	"log"
	"net"

	"github.com/hashicorp/nomad/client/config"
	"github.com/hashicorp/nomad/nomad/structs"
)

const (
	// defaultNetworkSpeed is the speed set if the network link speed could not
	// be detected.
	defaultNetworkSpeed = 1000

	// networkDisallowLinkLocalOption/Default are used to allow the operator to
	// decide how the fingerprinter handles an interface that only contains link
	// local addresses.
	networkDisallowLinkLocalOption  = "fingerprint.network.disallow_link_local"
	networkDisallowLinkLocalDefault = false
)

// NetworkFingerprint is used to fingerprint the Network capabilities of a node
type NetworkFingerprint struct {
	StaticFingerprinter
	logger            *log.Logger
	interfaceDetector NetworkInterfaceDetector
}

// An interface to isolate calls to various api in net package
// This facilitates testing where we can implement
// fake interfaces and addresses to test varios code paths
type NetworkInterfaceDetector interface {
	Interfaces() ([]net.Interface, error)
	InterfaceByName(name string) (*net.Interface, error)
	Addrs(intf *net.Interface) ([]net.Addr, error)
}

// Implements the interface detector which calls net directly
type DefaultNetworkInterfaceDetector struct {
}

func (b *DefaultNetworkInterfaceDetector) Interfaces() ([]net.Interface, error) {
	return net.Interfaces()
}

func (b *DefaultNetworkInterfaceDetector) InterfaceByName(name string) (*net.Interface, error) {
	return net.InterfaceByName(name)
}

func (b *DefaultNetworkInterfaceDetector) Addrs(intf *net.Interface) ([]net.Addr, error) {
	return intf.Addrs()
}

// NewNetworkFingerprint returns a new NetworkFingerprinter with the given
// logger
func NewNetworkFingerprint(logger *log.Logger) Fingerprint {
	f := &NetworkFingerprint{logger: logger, interfaceDetector: &DefaultNetworkInterfaceDetector{}}
	return f
}

func (f *NetworkFingerprint) Fingerprint(cfg *config.Config, node *structs.Node) (bool, error) {
	if node.Resources == nil {
		node.Resources = &structs.Resources{}
	}

	// Find the named interface
	intf, err := f.findInterface(cfg.NetworkInterface)
	switch {
	case err != nil:
		return false, fmt.Errorf("Error while detecting network interface during fingerprinting: %v", err)
	case intf == nil:
		// No interface could be found
		return false, nil
	}

	// Record the throughput of the interface
	var mbits int
	throughput := f.linkSpeed(intf.Name)
	if cfg.NetworkSpeed != 0 {
		mbits = cfg.NetworkSpeed
		f.logger.Printf("[DEBUG] fingerprint.network: setting link speed to user configured speed: %d", mbits)
	} else if throughput != 0 {
		mbits = throughput
		f.logger.Printf("[DEBUG] fingerprint.network: link speed for %v set to %v", intf.Name, mbits)
	} else {
		mbits = defaultNetworkSpeed
		f.logger.Printf("[DEBUG] fingerprint.network: link speed could not be detected and no speed specified by user. Defaulting to %d", defaultNetworkSpeed)
	}

	// Create the network resources from the interface
	disallowLinkLocal := cfg.ReadBoolDefault(networkDisallowLinkLocalOption, networkDisallowLinkLocalDefault)
	nwResources, err := f.createNetworkResources(mbits, intf, disallowLinkLocal)
	if err != nil {
		return false, err
	}

	// Add the network resources to the node
	node.Resources.Networks = nwResources
	for _, nwResource := range nwResources {
		f.logger.Printf("[DEBUG] fingerprint.network: Detected interface %v with IP: %v", intf.Name, nwResource.IP)
	}

	// Deprecated, setting the first IP as unique IP for the node
	if len(nwResources) > 0 {
		node.Attributes["unique.network.ip-address"] = nwResources[0].IP
	}

	// return true, because we have a network connection
	return true, nil
}

// createNetworkResources creates network resources for every IP
func (f *NetworkFingerprint) createNetworkResources(throughput int, intf *net.Interface, disallowLinkLocal bool) ([]*structs.NetworkResource, error) {
	// Find the interface with the name
	addrs, err := f.interfaceDetector.Addrs(intf)
	if err != nil {
		return nil, err
	}

	nwResources := make([]*structs.NetworkResource, 0)
	linkLocals := make([]*structs.NetworkResource, 0)

	for _, addr := range addrs {
		// Create a new network resource
		newNetwork := &structs.NetworkResource{
			Device: intf.Name,
			MBits:  throughput,
		}

		// Find the IP Addr and the CIDR from the Address
		var ip net.IP
		switch v := (addr).(type) {
		case *net.IPNet:
			ip = v.IP
		case *net.IPAddr:
			ip = v.IP
		}

		newNetwork.IP = ip.String()
		if ip.To4() != nil {
			newNetwork.CIDR = newNetwork.IP + "/32"
		} else {
			newNetwork.CIDR = newNetwork.IP + "/128"
		}

		// If the ip is link-local then we ignore it unless the user allows it
		// and we detect nothing else
		if ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast() {
			linkLocals = append(linkLocals, newNetwork)
			continue
		}

		nwResources = append(nwResources, newNetwork)
	}

	if len(nwResources) == 0 && len(linkLocals) != 0 {
		if disallowLinkLocal {
			f.logger.Printf("[DEBUG] fingerprint.network: ignoring detected link-local address on interface %v", intf.Name)
			return nwResources, nil
		}

		return linkLocals, nil
	}

	return nwResources, nil
}

// Checks if the device is marked UP by the operator
func (f *NetworkFingerprint) isDeviceEnabled(intf *net.Interface) bool {
	return intf.Flags&net.FlagUp != 0
}

// Checks if the device has any IP address configured
func (f *NetworkFingerprint) deviceHasIpAddress(intf *net.Interface) bool {
	addrs, err := f.interfaceDetector.Addrs(intf)
	return err == nil && len(addrs) != 0
}

func (n *NetworkFingerprint) isDeviceLoopBackOrPointToPoint(intf *net.Interface) bool {
	return intf.Flags&(net.FlagLoopback|net.FlagPointToPoint) != 0
}

// Returns the interface with the name passed by user
// If the name is blank then it iterates through all the devices
// and finds one which is routable and marked as UP
// It excludes PPP and lo devices unless they are specifically asked
func (f *NetworkFingerprint) findInterface(deviceName string) (*net.Interface, error) {
	var interfaces []net.Interface
	var err error

	if deviceName != "" {
		return f.interfaceDetector.InterfaceByName(deviceName)
	}

	var intfs []net.Interface

	if intfs, err = f.interfaceDetector.Interfaces(); err != nil {
		return nil, err
	}

	for _, intf := range intfs {
		if f.isDeviceEnabled(&intf) && !f.isDeviceLoopBackOrPointToPoint(&intf) && f.deviceHasIpAddress(&intf) {
			interfaces = append(interfaces, intf)
		}
	}

	if len(interfaces) == 0 {
		return nil, nil
	}
	return &interfaces[0], nil
}