// Copyright (c) 2018-2019, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.

package network

import (
	"context"
	"fmt"
	"net"
	"os"
	"sort"
	"strconv"
	"strings"
	"time"

	"golang.org/x/sys/unix"

	"github.com/containernetworking/cni/libcni"
	"github.com/containernetworking/cni/pkg/types"
	cnitypes "github.com/containernetworking/cni/pkg/types/100"
	"github.com/containernetworking/plugins/plugins/ipam/host-local/backend/allocator"
	"github.com/hpcng/singularity/internal/pkg/util/env"
)

type netError string

func (e netError) Error() string { return string(e) }

const (
	// ErrNoCNIConfig corresponds to a missing CNI configuration path
	ErrNoCNIConfig = netError("no CNI configuration path provided")
	// ErrNoCNIPlugin corresponds to a missing CNI plugin path
	ErrNoCNIPlugin = netError("no CNI plugin path provided")
)

// CNIPath contains path to CNI configuration directory and path to executable
// CNI plugins directory
type CNIPath struct {
	Conf   string
	Plugin string
}

// Setup contains network installation setup
type Setup struct {
	networks        []string
	networkConfList []*libcni.NetworkConfigList
	runtimeConf     []*libcni.RuntimeConf
	result          []types.Result
	cniPath         *CNIPath
	containerID     string
	netNS           string
	envPath         string
}

// PortMapEntry describes a port mapping between host and container
type PortMapEntry struct {
	HostPort      int    `json:"hostPort"`
	ContainerPort int    `json:"containerPort"`
	Protocol      string `json:"protocol"`
	HostIP        string `json:"hostIP,omitempty"`
}

// GetAllNetworkConfigList lists configured networks in configuration path directory
// provided by cniPath
func GetAllNetworkConfigList(cniPath *CNIPath) ([]*libcni.NetworkConfigList, error) {
	networks := make([]*libcni.NetworkConfigList, 0)

	if cniPath == nil {
		return networks, ErrNoCNIConfig
	}
	if cniPath.Conf == "" {
		return networks, ErrNoCNIConfig
	}

	files, err := libcni.ConfFiles(cniPath.Conf, []string{".conf", ".json", ".conflist"})
	if err != nil {
		return nil, err
	} else if len(files) == 0 {
		return nil, libcni.NoConfigsFoundError{Dir: cniPath.Conf}
	}
	sort.Strings(files)

	for _, file := range files {
		if strings.HasSuffix(file, ".conflist") {
			conf, err := libcni.ConfListFromFile(file)
			if err != nil {
				return nil, fmt.Errorf("%s: %s", file, err)
			}
			networks = append(networks, conf)
		} else {
			conf, err := libcni.ConfFromFile(file)
			if err != nil {
				return nil, fmt.Errorf("%s: %s", file, err)
			}
			confList, err := libcni.ConfListFromConf(conf)
			if err != nil {
				return nil, fmt.Errorf("%s: %s", file, err)
			}
			networks = append(networks, confList)
		}
	}

	return networks, nil
}

// NewSetup creates and returns a network setup to configure, add and remove
// network interfaces in container
func NewSetup(networks []string, containerID string, netNS string, cniPath *CNIPath) (*Setup, error) {
	if cniPath == nil {
		return nil, ErrNoCNIConfig
	}
	if cniPath.Conf == "" {
		return nil, ErrNoCNIConfig
	}

	networkConfList := make([]*libcni.NetworkConfigList, len(networks))

	for i, network := range networks {
		var err error

		networkConfList[i], err = libcni.LoadConfList(cniPath.Conf, network)
		if err != nil {
			return nil, err
		}
	}

	return NewSetupFromConfig(networkConfList, containerID, netNS, cniPath)
}

// NewSetupFromConfig creates and returns network setup to configure from
// a network configuration list
func NewSetupFromConfig(networkConfList []*libcni.NetworkConfigList, containerID string, netNS string, cniPath *CNIPath) (*Setup, error) {
	id := containerID

	if id == "" {
		id = strconv.Itoa(os.Getpid())
	}

	if cniPath == nil {
		return nil, ErrNoCNIConfig
	}
	if cniPath.Conf == "" {
		return nil, ErrNoCNIConfig
	}
	if cniPath.Plugin == "" {
		return nil, ErrNoCNIPlugin
	}

	runtimeConf := make([]*libcni.RuntimeConf, len(networkConfList))
	networks := make([]string, len(networkConfList))

	ifIndex := 0
	for i, conf := range networkConfList {
		runtimeConf[i] = &libcni.RuntimeConf{
			ContainerID:    containerID,
			NetNS:          netNS,
			IfName:         fmt.Sprintf("eth%d", ifIndex),
			CapabilityArgs: make(map[string]interface{}),
			Args:           make([][2]string, 0),
		}

		networks[i] = conf.Name

		ifIndex++
	}

	return &Setup{
			networks:        networks,
			networkConfList: networkConfList,
			runtimeConf:     runtimeConf,
			cniPath:         cniPath,
			netNS:           netNS,
			containerID:     id,
		},
		nil
}

func parseArg(arg string) ([][2]string, error) {
	argList := make([][2]string, 0)

	pairs := strings.Split(arg, ";")
	for _, pair := range pairs {
		keyVal := strings.Split(pair, "=")
		if len(keyVal) != 2 {
			return nil, fmt.Errorf("invalid argument: %s", pair)
		}
		argList = append(argList, [2]string{keyVal[0], keyVal[1]})
	}
	return argList, nil
}

// SetCapability sets capability arguments for the corresponding network plugin
// uses by a configured network
func (m *Setup) SetCapability(network string, capName string, args interface{}) error {
	for i := range m.networks {
		if m.networks[i] == network {
			hasCap := false
			for _, plugin := range m.networkConfList[i].Plugins {
				if plugin.Network.Capabilities[capName] {
					hasCap = true
					break
				}
			}

			if !hasCap {
				return fmt.Errorf("%s network doesn't have %s capability", network, capName)
			}

			switch args := args.(type) {
			case PortMapEntry:
				if m.runtimeConf[i].CapabilityArgs[capName] == nil {
					m.runtimeConf[i].CapabilityArgs[capName] = make([]PortMapEntry, 0)
				}
				m.runtimeConf[i].CapabilityArgs[capName] = append(
					m.runtimeConf[i].CapabilityArgs[capName].([]PortMapEntry),
					args,
				)
			case []allocator.Range:
				if m.runtimeConf[i].CapabilityArgs[capName] == nil {
					m.runtimeConf[i].CapabilityArgs[capName] = []allocator.RangeSet{args}
				}
			}
		}
	}
	return nil
}

// SetArgs affects arguments to corresponding network plugins
func (m *Setup) SetArgs(args []string) error {
	if len(m.networks) < 1 {
		return fmt.Errorf("there is no configured network in list")
	}

	// Force plugins to ignore extra CNI_ARGS that they don't consume.
	// If we don't do this we get an error when e.g. passing IP= to a
	// bridge+ipam config,  as bridge now handles args from v1.0.1, but
	// doesn't consume IP.
	for i := range m.networks {
		m.runtimeConf[i].Args = append(m.runtimeConf[i].Args, [2]string{"IgnoreUnknown", "1"})
	}

	for _, arg := range args {
		var splitted []string
		networkName := ""

		if strings.IndexByte(arg, ':') > strings.IndexByte(arg, '=') {
			splitted = []string{m.networks[0], arg}
		} else {
			splitted = strings.SplitN(arg, ":", 2)
		}
		if len(splitted) < 1 && len(splitted) > 2 {
			return fmt.Errorf("argument must be of form '<network>:KEY1=value1;KEY2=value1' or 'KEY1=value1;KEY2=value1'")
		}
		n := len(splitted) - 1
		if n == 0 {
			networkName = m.networks[0]
		} else {
			networkName = splitted[0]
		}
		hasNetwork := false
		for _, network := range m.networks {
			if network == networkName {
				hasNetwork = true
				break
			}
		}
		if !hasNetwork {
			return fmt.Errorf("network %s wasn't specified in --network option", networkName)
		}
		argList, err := parseArg(splitted[n])
		if err != nil {
			return err
		}
		for _, kv := range argList {
			key := kv[0]
			value := kv[1]
			if key == "portmap" {
				pm := &PortMapEntry{}

				splittedPort := strings.SplitN(value, "/", 2)
				if len(splittedPort) != 2 {
					return fmt.Errorf("badly formatted portmap argument '%s', must be of form portmap=hostPort:containerPort/protocol", value)
				}
				pm.Protocol = splittedPort[1]
				if pm.Protocol != "tcp" && pm.Protocol != "udp" {
					return fmt.Errorf("only tcp and udp protocol can be specified")
				}
				ports := strings.Split(splittedPort[0], ":")
				if len(ports) != 1 && len(ports) != 2 {
					return fmt.Errorf("portmap port argument is badly formatted")
				}
				if n, err := strconv.ParseUint(ports[0], 0, 16); err == nil {
					pm.HostPort = int(n)
					if pm.HostPort <= 0 || pm.HostPort > 65535 {
						return fmt.Errorf("host port must be greater than 0 and less than 65535")
					}
				} else {
					return fmt.Errorf("can't convert host port '%s': %s", ports[0], err)
				}
				if len(ports) == 2 {
					if n, err := strconv.ParseUint(ports[1], 0, 16); err == nil {
						pm.ContainerPort = int(n)
						if pm.ContainerPort <= 0 || pm.ContainerPort > 65535 {
							return fmt.Errorf("container port must be greater than 0 and less than 65535")
						}
					} else {
						return fmt.Errorf("can't convert container port '%s': %s", ports[1], err)
					}
				} else {
					pm.ContainerPort = pm.HostPort
				}
				if err := m.SetCapability(networkName, "portMappings", *pm); err != nil {
					return err
				}
			} else if key == "ipRange" {
				ipRange := make([]allocator.Range, 1)
				_, subnet, err := net.ParseCIDR(value)
				if err != nil {
					return err
				}
				ipRange[0].Subnet = types.IPNet(*subnet)
				if err := m.SetCapability(networkName, "ipRanges", ipRange); err != nil {
					return err
				}
			} else {
				for i := range m.networks {
					if m.networks[i] == networkName {
						m.runtimeConf[i].Args = append(m.runtimeConf[i].Args, kv)
					}
				}
			}
		}
	}
	return nil
}

// GetNetworkIP returns IP associated with a configured network, if network
// is empty, the function returns IP for the first configured network
func (m *Setup) GetNetworkIP(network string, version string) (net.IP, error) {
	n := network
	if n == "" && len(m.networkConfList) > 0 {
		n = m.networkConfList[0].Name
	}

	for i := 0; i < len(m.networkConfList); i++ {
		if m.networkConfList[i].Name == n {
			res, err := cnitypes.NewResultFromResult(m.result[i])
			if err != nil {
				return nil, fmt.Errorf("could not convert result: %v", err)
			}
			for _, ipResult := range res.IPs {
				is4 := ipResult.Address.IP.To4() != nil
				if (is4 && version == "4") || version == "6" {
					return ipResult.Address.IP, nil
				}
			}
			break
		}
	}

	return nil, fmt.Errorf("no IP found for network %s", network)
}

// GetNetworkInterface returns container network interface associated
// with a network, if network is empty, the function returns interface
// for the first configured network
func (m *Setup) GetNetworkInterface(network string) (string, error) {
	if network == "" && len(m.runtimeConf) > 0 {
		return m.runtimeConf[0].IfName, nil
	}

	for i := 0; i < len(m.networkConfList); i++ {
		if m.networkConfList[i].Name == network {
			return m.runtimeConf[i].IfName, nil
		}
	}

	return "", fmt.Errorf("no interface found for network %s", network)
}

// SetPortProtection provides a basic mechanism to prevent port hijacking
func (m *Setup) SetPortProtection(network string, lowPort int) error {
	idx := -1
	for i := 0; i < len(m.networkConfList); i++ {
		if m.networkConfList[i].Name == network {
			idx = i
			break
		}
	}
	if idx < 0 {
		return fmt.Errorf("no configuration found for network %s", network)
	}

	entries, ok := m.runtimeConf[idx].CapabilityArgs["portMappings"].([]PortMapEntry)
	if !ok {
		return nil
	}
	for _, e := range entries {
		sockProt := unix.IPPROTO_TCP
		sockType := unix.SOCK_STREAM

		if e.HostPort <= lowPort {
			return fmt.Errorf("not authorized to map port under %d", lowPort)
		}
		if e.Protocol == "udp" {
			sockProt = unix.IPPROTO_UDP
			sockType = unix.SOCK_DGRAM
		}
		fd, err := unix.Socket(unix.AF_INET, sockType, sockProt)
		if err != nil {
			return fmt.Errorf("failed to create %s socket on port %d: %s", e.Protocol, e.HostPort, err)
		}
		err = unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
		if err != nil {
			return fmt.Errorf("failed to set reuseport for %s socket on port %d: %s", e.Protocol, e.HostPort, err)
		}
		sockAddr := &unix.SockaddrInet4{
			Port: e.HostPort,
		}
		err = unix.Bind(fd, sockAddr)
		if err != nil {
			return fmt.Errorf("failed to bind %s socket on port %d: %s", e.Protocol, e.HostPort, err)
		}
		if sockType == unix.SOCK_STREAM {
			err = unix.Listen(fd, 1)
			if err != nil {
				return fmt.Errorf("failed to listen on %s socket port %d: %s", e.Protocol, e.HostPort, err)
			}
		}
	}
	return nil
}

// SetEnvPath allows to define custom paths for PATH environment
// variables used during CNI plugin execution
func (m *Setup) SetEnvPath(envPath string) {
	m.envPath = envPath
}

// AddNetworks brings up networks interface in container
func (m *Setup) AddNetworks(ctx context.Context) error {
	return m.command(ctx, "ADD")
}

// DelNetworks tears down networks interface in container
func (m *Setup) DelNetworks(ctx context.Context) error {
	return m.command(ctx, "DEL")
}

func (m *Setup) command(ctx context.Context, command string) error {
	if m.envPath != "" {
		backupEnv := os.Environ()
		os.Clearenv()
		os.Setenv("PATH", m.envPath)
		defer env.SetFromList(backupEnv)
	}

	config := &libcni.CNIConfig{Path: []string{m.cniPath.Plugin}}

	// set a timeout context for the execution of the CNI plugin
	// to interrupt its execution if it takes more than 5 seconds
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	if command == "ADD" {
		m.result = make([]types.Result, len(m.networkConfList))
		for i := 0; i < len(m.networkConfList); i++ {
			var err error
			if m.result[i], err = config.AddNetworkList(ctx, m.networkConfList[i], m.runtimeConf[i]); err != nil {
				for j := i - 1; j >= 0; j-- {
					if err := config.DelNetworkList(ctx, m.networkConfList[j], m.runtimeConf[j]); err != nil {
						return err
					}
				}
				return err
			}
		}
	} else if command == "DEL" {
		for i := 0; i < len(m.networkConfList); i++ {
			if err := config.DelNetworkList(ctx, m.networkConfList[i], m.runtimeConf[i]); err != nil {
				return err
			}
		}
	}
	return nil
}
