package util

import (
	"errors"
	"fmt"
	"net"

	"github.com/containers/podman/v3/libpod/network/types"
	"github.com/containers/podman/v3/pkg/util"
	"github.com/sirupsen/logrus"
)

// GetBridgeInterfaceNames returns all bridge interface names
// already used by network configs
func GetBridgeInterfaceNames(n NetUtil) []string {
	names := make([]string, 0, n.Len())
	n.ForEach(func(net types.Network) {
		if net.Driver == types.BridgeNetworkDriver {
			names = append(names, net.NetworkInterface)
		}
	})
	return names
}

// GetUsedNetworkNames returns all network names already used
// by network configs
func GetUsedNetworkNames(n NetUtil) []string {
	names := make([]string, 0, n.Len())
	n.ForEach(func(net types.Network) {
		if net.Driver == types.BridgeNetworkDriver {
			names = append(names, net.NetworkInterface)
		}
	})
	return names
}

// GetFreeDeviceName returns a free device name which can
// be used for new configs as name and bridge interface name.
// The base name is suffixed by a number
func GetFreeDeviceName(n NetUtil) (string, error) {
	bridgeNames := GetBridgeInterfaceNames(n)
	netNames := GetUsedNetworkNames(n)
	liveInterfaces, err := GetLiveNetworkNames()
	if err != nil {
		return "", nil
	}
	names := make([]string, 0, len(bridgeNames)+len(netNames)+len(liveInterfaces))
	names = append(names, bridgeNames...)
	names = append(names, netNames...)
	names = append(names, liveInterfaces...)
	// FIXME: Is a limit fine?
	// Start by 1, 0 is reserved for the default network
	for i := 1; i < 1000000; i++ {
		deviceName := fmt.Sprintf("%s%d", n.DefaultInterfaceName(), i)
		if !util.StringInSlice(deviceName, names) {
			logrus.Debugf("found free device name %s", deviceName)
			return deviceName, nil
		}
	}
	return "", errors.New("could not find free device name, to many iterations")
}

// GetUsedSubnets returns a list of all used subnets by network
// configs and interfaces on the host.
func GetUsedSubnets(n NetUtil) ([]*net.IPNet, error) {
	// first, load all used subnets from network configs
	subnets := make([]*net.IPNet, 0, n.Len())
	n.ForEach(func(n types.Network) {
		for i := range n.Subnets {
			subnets = append(subnets, &n.Subnets[i].Subnet.IPNet)
		}
	})
	// second, load networks from the current system
	liveSubnets, err := getLiveNetworkSubnets()
	if err != nil {
		return nil, err
	}
	return append(subnets, liveSubnets...), nil
}

// GetFreeIPv6NetworkSubnet returns a unused ipv4 subnet
func GetFreeIPv4NetworkSubnet(usedNetworks []*net.IPNet) (*types.Subnet, error) {
	// the default podman network is 10.88.0.0/16
	// start locking for free /24 networks
	network := &net.IPNet{
		IP:   net.IP{10, 89, 0, 0},
		Mask: net.IPMask{255, 255, 255, 0},
	}

	// TODO: make sure to not use public subnets
	for {
		if intersectsConfig := NetworkIntersectsWithNetworks(network, usedNetworks); !intersectsConfig {
			logrus.Debugf("found free ipv4 network subnet %s", network.String())
			return &types.Subnet{
				Subnet: types.IPNet{IPNet: *network},
			}, nil
		}
		var err error
		network, err = NextSubnet(network)
		if err != nil {
			return nil, err
		}
	}
}

// GetFreeIPv6NetworkSubnet returns a unused ipv6 subnet
func GetFreeIPv6NetworkSubnet(usedNetworks []*net.IPNet) (*types.Subnet, error) {
	// FIXME: Is 10000 fine as limit? We should prevent an endless loop.
	for i := 0; i < 10000; i++ {
		// RFC4193: Choose the ipv6 subnet random and NOT sequentially.
		network, err := getRandomIPv6Subnet()
		if err != nil {
			return nil, err
		}
		if intersectsConfig := NetworkIntersectsWithNetworks(&network, usedNetworks); !intersectsConfig {
			logrus.Debugf("found free ipv6 network subnet %s", network.String())
			return &types.Subnet{
				Subnet: types.IPNet{IPNet: network},
			}, nil
		}
	}
	return nil, errors.New("failed to get random ipv6 subnet")
}