/*
  Copyright 2004 The Kube-router Authors.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
*/

package ipset

import (
	"bytes"
	// nolint:gosec // we don't use this hash in a sensitive capacity, so we don't care that its weak
	"crypto/sha1"
	"encoding/base32"
	"errors"
	"fmt"
	"os/exec"
	"sort"
	"strings"
)

var (
	// Error returned when ipset binary is not found.
	errIpsetNotFound = errors.New("ipset utility not found")
)

const (
	// FamillyInet IPV4.
	FamillyInet = "inet"
	// FamillyInet6 IPV6.
	FamillyInet6 = "inet6"

	// DefaultMaxElem Default OptionMaxElem value.
	DefaultMaxElem = "65536"
	// DefaultHasSize Defaul OptionHashSize value.
	DefaultHasSize = "1024"

	// TypeHashIP The hash:ip set type uses a hash to store IP host addresses (default) or network addresses. Zero
	// valued IP address cannot be stored in a hash:ip type of set.
	TypeHashIP = "hash:ip"
	// TypeHashMac The hash:mac set type uses a hash to store MAC addresses. Zero valued MAC addresses cannot be stored
	// in a hash:mac type of set.
	TypeHashMac = "hash:mac"
	// TypeHashNet The hash:net set type uses a hash to store different sized IP network addresses. Network address with
	// zero prefix size cannot be stored in this type of sets.
	TypeHashNet = "hash:net"
	// TypeHashNetNet The hash:net,net set type uses a hash to store pairs of different sized IP network addresses. Bear
	// in mind that the first parameter has precedence over the second, so a nomatch entry could be potentially be
	// ineffective if a more specific first parameter existed with a suitable second parameter. Network address with
	// zero prefix size cannot be stored in this type of set.
	TypeHashNetNet = "hash:net,net"
	// TypeHashIPPort The hash:ip,port set type uses a hash to store IP address and port number pairs. The port number
	// is interpreted together with a protocol (default TCP) and zero protocol number cannot be used.
	TypeHashIPPort = "hash:ip,port"
	// TypeHashNetPort The hash:net,port set type uses a hash to store different sized IP network address and port
	// pairs. The port number is interpreted together with a protocol (default TCP) and zero protocol number cannot be
	// used. Network address with zero prefix size is not accepted either.
	TypeHashNetPort = "hash:net,port"
	// TypeHashIPPortIP The hash:ip,port,ip set type uses a hash to store IP address, port number and a second IP
	// address triples. The port number is interpreted together with a protocol (default TCP) and zero protocol number
	// cannot be used.
	TypeHashIPPortIP = "hash:ip,port,ip"
	// TypeHashIPPortNet The hash:ip,port,net set type uses a hash to store IP address, port number and IP network
	// address triples. The port number is interpreted together with a protocol (default TCP) and zero protocol number
	// cannot be used. Network address with zero prefix size cannot be stored either.
	TypeHashIPPortNet = "hash:ip,port,net"
	// TypeHashIPMark The hash:ip,mark set type uses a hash to store IP address and packet mark pairs.
	TypeHashIPMark = "hash:ip,mark"
	// TypeHashIPNetPortNet The hash:net,port,net set type behaves similarly to hash:ip,port,net but accepts a cidr
	// value for both the first and last parameter. Either subnet is permitted to be a /0 should you wish to match port
	// between all destinations.
	TypeHashIPNetPortNet = "hash:net,port,net"
	// TypeHashNetIface The hash:net,iface set type uses a hash to store different sized IP network address and
	// interface name pairs.
	TypeHashNetIface = "hash:net,iface"
	// TypeListSet The list:set type uses a simple list in which you can store set names.
	TypeListSet = "list:set"

	// OptionTimeout All set types supports the optional timeout parameter when creating a set and adding entries. The
	// value of the timeout parameter for the create command means the default timeout value (in seconds) for new
	// entries. If a set is created with timeout support, then the same timeout option can be used to specify
	// non-default timeout values when adding entries. Zero timeout value means the entry is added permanent to the
	// set. The timeout value of already added elements can be changed by readding the element using the -exist option.
	// When listing the set, the number of entries printed in the header might be larger than the listed number of
	// entries for sets with the timeout extensions: the number of entries in the set is updated when elements
	// added/deleted to the set and periodically when the garbage colletor evicts the timed out entries.
	OptionTimeout = "timeout"
	// OptionCounters All set types support the optional counters option when creating a set. If the option is specified
	// then the set is created with packet and byte counters per element support. The packet and byte counters are
	// initialized to zero when the elements are (re-)added to the set, unless the packet and byte counter values are
	// explicitly specified by the packets and bytes options. An example when an element is added to a set with non-zero
	// counter values.
	OptionCounters = "counters"
	// OptionPackets All set types support the optional counters option when creating a set. If the option is specified
	// then the set is created with packet and byte counters per element support. The packet and byte counters are
	// initialized to zero when the elements are (re-)added to the set, unless the packet and byte counter values are
	// explicitly specified by the packets and bytes options. An example when an element is added to a set with non-zero
	// counter values.
	OptionPackets = "packets"
	// OptionBytes All set types support the optional counters option when creating a set. If the option is specified
	// then the set is created with packet and byte counters per element support. The packet and byte counters are
	// initialized to zero when the elements are (re-)added to the set, unless the packet and byte counter values are
	// explicitly specified by the packets and bytes options. An example when an element is added to a set with non-zero
	// counter values.
	OptionBytes = "bytes"
	// OptionComment All set types support the optional comment extension. Enabling this extension on an ipset enables
	// you to annotate an ipset entry with an arbitrary string. This string is completely ignored by both the kernel and
	// ipset itself and is purely for providing a convenient means to document the reason for an entry's existence.
	// Comments must not contain any quotation marks and the usual escape character (\) has no meaning.
	OptionComment = "comment"
	// OptionSkbinfo All set types support the optional skbinfo extension. This extension allow to store the metainfo
	// (firewall mark, tc class and hardware queue) with every entry and map it to packets by usage of SET netfilter
	// target with --map-set option. skbmark option format: MARK or MARK/MASK, where MARK and MASK are 32bit hex numbers
	// with 0x prefix. If only mark is specified mask 0xffffffff are used. skbprio option has tc class format:
	// MAJOR:MINOR, where major and minor numbers are hex without 0x prefix. skbqueue option is just decimal number.
	OptionSkbinfo = "skbinfo"
	// OptionSkbmark All set types support the optional skbinfo extension. This extension allow to store the metainfo
	// (firewall mark, tc class and hardware queue) with every entry and map it to packets by usage of SET netfilter
	// target with --map-set option. skbmark option format: MARK or MARK/MASK, where MARK and MASK are 32bit hex numbers
	// with 0x prefix. If only mark is specified mask 0xffffffff are used. skbprio option has tc class format:
	//MAJOR:MINOR, where major and minor numbers are hex without 0x prefix. skbqueue option is just decimal number.
	OptionSkbmark = "skbmark"
	// OptionSkbprio All set types support the optional skbinfo extension. This extension allow to store the metainfo
	// (firewall mark, tc class and hardware queue) with every entry and map it to packets by usage of SET netfilter
	// target with --map-set option. skbmark option format: MARK or MARK/MASK, where MARK and MASK are 32bit hex numbers
	// with 0x prefix. If only mark is specified mask 0xffffffff are used. skbprio option has tc class format:
	// MAJOR:MINOR, where major and minor numbers are hex without 0x prefix. skbqueue option is just decimal number.
	OptionSkbprio = "skbprio"
	// OptionSkbqueue All set types support the optional skbinfo extension. This extension allow to store the metainfo
	// (firewall mark, tc class and hardware queue) with every entry and map it to packets by usage of SET netfilter
	// target with --map-set option. skbmark option format: MARK or MARK/MASK, where MARK and MASK are 32bit hex numbers
	// with 0x prefix. If only mark is specified mask 0xffffffff are used. skbprio option has tc class format:
	// MAJOR:MINOR, where major and minor numbers are hex without 0x prefix. skbqueue option is just decimal number.
	OptionSkbqueue = "skbqueue"
	// OptionHashSize This parameter is valid for the create command of all hash type sets. It defines the initial hash
	// size for the set, default is 1024. The hash size must be a power of two, the kernel automatically rounds up non
	// power of two hash sizes to the first correct value.
	OptionHashSize = "hashsize"
	// OptionMaxElem This parameter is valid for the create command of all hash type sets. It does define the maximal
	// number of elements which can be stored in the set, default 65536.
	OptionMaxElem = "maxelem"
	// OptionFamilly This parameter is valid for the create command of all hash type sets except for hash:mac. It
	// defines the protocol family of the IP addresses to be stored in the set. The default is inet, i.e IPv4.
	OptionFamilly = "family"
	// OptionNoMatch The hash set types which can store net type of data (i.e. hash:*net*) support the optional nomatch
	// option when adding entries. When matching elements in the set, entries marked as nomatch are skipped as if those
	// were not added to the set, which makes possible to build up sets with exceptions. See the example at hash type
	// hash:net below. When elements are tested by ipset, the nomatch flags are taken into account. If one wants to test
	// the existence of an element marked with nomatch in a set, then the flag must be specified too.
	OptionNoMatch = "nomatch"
	// OptionForceAdd All hash set types support the optional forceadd parameter when creating a set. When sets created
	// with this option become full the next addition to the set may succeed and evict a random entry from the set.
	OptionForceAdd = "forceadd"

	// tmpIPSetPrefix Is the prefix added to temporary ipset names used in the atomic swap operations during ipset
	// restore. You should never see these on your system because they only exist during the restore.
	tmpIPSetPrefix = "TMP-"
)

// IPSet represent ipset sets managed by.
type IPSet struct {
	ipSetPath *string
	Sets      map[string]*Set
	isIpv6    bool
}

// Set represent a ipset set entry.
type Set struct {
	Parent  *IPSet
	Name    string
	Entries []*Entry
	Options []string
}

// Entry of ipset Set.
type Entry struct {
	Set     *Set
	Options []string
}

// Get ipset binary path or return an error.
func getIPSetPath() (*string, error) {
	path, err := exec.LookPath("ipset")
	if err != nil {
		return nil, errIpsetNotFound
	}
	return &path, nil
}

// Used to run ipset binary with args and return stdout.
func (ipset *IPSet) run(args ...string) (string, error) {
	var stderr bytes.Buffer
	var stdout bytes.Buffer
	cmd := exec.Cmd{
		Path:   *ipset.ipSetPath,
		Args:   append([]string{*ipset.ipSetPath}, args...),
		Stderr: &stderr,
		Stdout: &stdout,
	}

	if err := cmd.Run(); err != nil {
		return "", errors.New(stderr.String())
	}

	return stdout.String(), nil
}

// Used to run ipset binary with arg and inject stdin buffer and return stdout.
func (ipset *IPSet) runWithStdin(stdin *bytes.Buffer, args ...string) error {
	var stderr bytes.Buffer
	var stdout bytes.Buffer
	cmd := exec.Cmd{
		Path:   *ipset.ipSetPath,
		Args:   append([]string{*ipset.ipSetPath}, args...),
		Stderr: &stderr,
		Stdout: &stdout,
		Stdin:  stdin,
	}

	if err := cmd.Run(); err != nil {
		return errors.New(stderr.String())
	}

	return nil
}

// NewIPSet create a new IPSet with ipSetPath initialized.
func NewIPSet(isIpv6 bool) (*IPSet, error) {
	ipSetPath, err := getIPSetPath()
	if err != nil {
		return nil, err
	}
	ipSet := &IPSet{
		ipSetPath: ipSetPath,
		Sets:      make(map[string]*Set),
		isIpv6:    isIpv6,
	}
	return ipSet, nil
}

// Create a set identified with setname and specified type. The type may
// require type specific options. Does not create set on the system if it
// already exists by the same name.
func (ipset *IPSet) Create(setName string, createOptions ...string) (*Set, error) {
	// Populate Set map if needed
	if ipset.Get(setName) == nil {
		ipset.Sets[setName] = &Set{
			Name:    setName,
			Options: createOptions,
			Parent:  ipset,
		}
	}

	// Determine if set with the same name is already active on the system
	setIsActive, err := ipset.Sets[setName].IsActive()
	if err != nil {
		return nil, fmt.Errorf("failed to determine if ipset set %s exists: %s",
			setName, err)
	}

	// Create set if missing from the system
	if !setIsActive {
		if ipset.isIpv6 {
			// Add "family inet6" option and a "inet6:" prefix for IPv6 sets.
			args := []string{"create", "-exist", ipset.Sets[setName].name()}
			args = append(args, createOptions...)
			args = append(args, "family", "inet6")
			if _, err := ipset.run(args...); err != nil {
				return nil, fmt.Errorf("failed to create ipset set on system: %s", err)
			}
		} else {
			_, err := ipset.run(append([]string{"create", "-exist", setName},
				createOptions...)...)
			if err != nil {
				return nil, fmt.Errorf("failed to create ipset set on system: %s", err)
			}
		}
	}
	return ipset.Sets[setName], nil
}

// Add a given Set to an IPSet
func (ipset *IPSet) Add(set *Set) error {
	_, err := ipset.Create(set.Name, set.Options...)
	if err != nil {
		return err
	}

	options := make([][]string, len(set.Entries))
	for index, entry := range set.Entries {
		options[index] = entry.Options
	}

	err = ipset.Get(set.Name).BatchAdd(options)
	if err != nil {
		return err
	}

	return nil
}

// RefreshSet add/update internal Sets with a Set of entries but does not run restore command
func (ipset *IPSet) RefreshSet(setName string, entriesWithOptions [][]string, setType string) {
	if ipset.Get(setName) == nil {
		ipset.Sets[setName] = &Set{
			Name:    setName,
			Options: []string{setType, OptionTimeout, "0"},
			Parent:  ipset,
		}
	}
	entries := make([]*Entry, len(entriesWithOptions))
	for i, entry := range entriesWithOptions {
		entries[i] = &Entry{Set: ipset.Sets[setName], Options: entry}
	}
	ipset.Get(setName).Entries = entries
}

// Add a given entry to the set. If the -exist option is specified, ipset
// ignores if the entry already added to the set.
// Note: if you need to add multiple entries (e.g., in a loop), use BatchAdd instead,
// as it’s much more performant.
func (set *Set) Add(addOptions ...string) (*Entry, error) {
	entry := &Entry{
		Set:     set,
		Options: addOptions,
	}
	set.Entries = append(set.Entries, entry)
	_, err := set.Parent.run(append([]string{"add", "-exist", entry.Set.name()}, addOptions...)...)
	if err != nil {
		return nil, err
	}
	return entry, nil
}

// BatchAdd given entries (with their options) to the set.
// For multiple items, this is much faster than Add().
func (set *Set) BatchAdd(addOptions [][]string) error {
	newEntries := make([]*Entry, len(addOptions))
	for index, options := range addOptions {
		entry := &Entry{
			Set:     set,
			Options: options,
		}
		newEntries[index] = entry
	}
	set.Entries = append(set.Entries, newEntries...)

	// Build the `restore` command contents
	var builder strings.Builder
	for _, options := range addOptions {
		line := strings.Join(append([]string{"add", "-exist", set.name()}, options...), " ")
		builder.WriteString(line + "\n")
	}
	restoreContents := builder.String()

	// Invoke the command
	err := set.Parent.runWithStdin(bytes.NewBufferString(restoreContents), "restore")
	if err != nil {
		return err
	}
	return nil
}

// Del an entry from a set. If the -exist option is specified and the entry is
// not in the set (maybe already expired), then the command is ignored.
func (entry *Entry) Del() error {
	_, err := entry.Set.Parent.run(append([]string{"del", entry.Set.name()}, entry.Options...)...)
	if err != nil {
		return err
	}
	err = entry.Set.Parent.Save()
	if err != nil {
		return err
	}
	return nil
}

// Test whether an entry is in a set or not. Exit status number is zero if the
// tested entry is in the set and nonzero if it is missing from the set.
func (set *Set) Test(testOptions ...string) (bool, error) {
	_, err := set.Parent.run(append([]string{"test", set.name()}, testOptions...)...)
	if err != nil {
		return false, err
	}
	return true, nil
}

// Destroy the specified set or all the sets if none is given. If the set has
// got reference(s), nothing is done and no set destroyed.
func (set *Set) Destroy() error {
	_, err := set.Parent.run("destroy", set.name())
	if err != nil {
		return err
	}

	delete(set.Parent.Sets, set.Name)
	return nil
}

// Destroy the specified set by name. If the set has got reference(s), nothing
// is done and no set destroyed. If the IPSet does not contain the named set
// then Destroy is a no-op.
func (ipset *IPSet) Destroy(setName string) error {
	set := ipset.Get(setName)
	if set == nil {
		return nil
	}

	err := set.Destroy()
	if err != nil {
		return err
	}

	return nil
}

// DestroyAllWithin destroys all sets contained within the IPSet's Sets.
func (ipset *IPSet) DestroyAllWithin() error {
	for _, v := range ipset.Sets {
		err := v.Destroy()
		if err != nil {
			return err
		}
	}

	return nil
}

// IsActive checks if a set exists on the system with the same name.
func (set *Set) IsActive() (bool, error) {
	_, err := set.Parent.run("list", set.name())
	if err != nil {
		if strings.Contains(err.Error(), "name does not exist") {
			return false, nil
		}
		return false, err
	}
	return true, nil
}

func (set *Set) name() string {
	if set.Parent.isIpv6 {
		return "inet6:" + set.Name
	}
	return set.Name
}

func (set *Set) GetNameWithProtocol() string {
	return set.name()
}

// Parse ipset save stdout.
// ex:
// create KUBE-DST-3YNVZWWGX3UQQ4VQ hash:ip family inet hashsize 1024 maxelem 65536 timeout 0
// add KUBE-DST-3YNVZWWGX3UQQ4VQ 100.96.1.6 timeout 0
func parseIPSetSave(ipset *IPSet, result string) map[string]*Set {
	sets := make(map[string]*Set)
	// Save is always in order
	lines := strings.Split(result, "\n")
	for _, line := range lines {
		content := strings.Split(line, " ")
		if content[0] == "create" {
			sets[content[1]] = &Set{
				Parent:  ipset,
				Name:    content[1],
				Options: content[2:],
			}
		} else if content[0] == "add" {
			set := sets[content[1]]
			set.Entries = append(set.Entries, &Entry{
				Set:     set,
				Options: content[2:],
			})
		}
	}

	return sets
}

// Build ipset restore input
// ex:
// create KUBE-DST-3YNVZWWGX3UQQ4VQ hash:ip family inet hashsize 1024 maxelem 65536 timeout 0
// add KUBE-DST-3YNVZWWGX3UQQ4VQ 100.96.1.6 timeout 0
func buildIPSetRestore(ipset *IPSet) string {
	setNames := make([]string, 0, len(ipset.Sets))
	for setName := range ipset.Sets {
		// we need setNames in some consistent order so that we can unit-test this method has a predictable output:
		setNames = append(setNames, setName)
	}

	sort.Strings(setNames)

	tmpSets := map[string]string{}
	ipSetRestore := &strings.Builder{}
	for _, setName := range setNames {
		set := ipset.Sets[setName]
		setOptions := strings.Join(set.Options, " ")

		tmpSetName := tmpSets[setOptions]
		if tmpSetName == "" {
			// create a temporary set per unique set-options:
			// nolint:gosec // we don't use this hash in a sensitive capacity, so we don't care that its weak
			hash := sha1.Sum([]byte("tmp:" + setOptions))
			tmpSetName = tmpIPSetPrefix + base32.StdEncoding.EncodeToString(hash[:10])
			ipSetRestore.WriteString(fmt.Sprintf("create %s %s\n", tmpSetName, setOptions))
			// just in case we are starting up after a crash, we should flush the TMP ipset to be safe if it
			// already existed, so we do not pollute other ipsets:
			ipSetRestore.WriteString(fmt.Sprintf("flush %s\n", tmpSetName))
			tmpSets[setOptions] = tmpSetName
		}

		for _, entry := range set.Entries {
			// add entries to the tmp set:
			ipSetRestore.WriteString(fmt.Sprintf("add %s %s\n", tmpSetName, strings.Join(entry.Options, " ")))
		}

		// now create the actual IPSet (this is a noop if it already exists, because we run with -exists):
		ipSetRestore.WriteString(fmt.Sprintf("create %s %s\n", set.Name, setOptions))

		// now that both exist, we can swap them:
		ipSetRestore.WriteString(fmt.Sprintf("swap %s %s\n", tmpSetName, set.Name))

		// empty the tmp set (which is actually the old one now):
		ipSetRestore.WriteString(fmt.Sprintf("flush %s\n", tmpSetName))
	}

	setsToDestroy := make([]string, 0, len(tmpSets))
	for _, tmpSetName := range tmpSets {
		setsToDestroy = append(setsToDestroy, tmpSetName)
	}
	// need to destroy the sets in a predictable order for unit test!
	sort.Strings(setsToDestroy)
	for _, tmpSetName := range setsToDestroy {
		// finally, destroy the tmp sets.
		ipSetRestore.WriteString(fmt.Sprintf("destroy %s\n", tmpSetName))
	}

	return ipSetRestore.String()
}

// Save the given set, or all sets if none is given to stdout in a format that
// restore can read. The option -file can be used to specify a filename instead
// of stdout.
// save "ipset save" command output to ipset.sets.
func (ipset *IPSet) Save() error {
	stdout, err := ipset.run("save")
	if err != nil {
		return err
	}
	ipset.Sets = parseIPSetSave(ipset, stdout)
	return nil
}

// Restore a saved session generated by save. The saved session can be fed from
// stdin or the option -file can be used to specify a filename instead of
// stdin. Please note, existing sets and elements are not erased by restore
// unless specified so in the restore file. All commands are allowed in restore
// mode except list, help, version, interactive mode and restore itself.
// Send formatted ipset.sets into stdin of "ipset restore" command.
func (ipset *IPSet) Restore() error {
	stdin := bytes.NewBufferString(buildIPSetRestore(ipset))
	err := ipset.runWithStdin(stdin, "restore", "-exist")
	if err != nil {
		return err
	}
	return nil
}

// Flush all entries from the specified set or flush all sets if none is given.
func (set *Set) Flush() error {
	_, err := set.Parent.run("flush", set.Name)
	if err != nil {
		return err
	}
	return nil
}

// Flush all entries from the specified set or flush all sets if none is given.
func (ipset *IPSet) Flush() error {
	_, err := ipset.run("flush")
	if err != nil {
		return err
	}
	return nil
}

// Get Set by Name.
func (ipset *IPSet) Get(setName string) *Set {
	set, ok := ipset.Sets[setName]
	if !ok {
		return nil
	}

	return set
}

// Rename a set. Set identified by SETNAME-TO must not exist.
func (set *Set) Rename(newName string) error {
	if set.Parent.isIpv6 {
		newName = "ipv6:" + newName
	}
	_, err := set.Parent.run("rename", set.name(), newName)
	if err != nil {
		return err
	}
	return nil
}

// Swap the content of two sets, or in another words, exchange the name of two
// sets. The referred sets must exist and compatible type of sets can be
// swapped only.
func (set *Set) Swap(setTo *Set) error {
	_, err := set.Parent.run("swap", set.name(), setTo.name())
	if err != nil {
		return err
	}
	return nil
}

// Refresh a Set with new entries.
func (set *Set) Refresh(entries []string, extraOptions ...string) error {
	entriesWithOptions := make([][]string, len(entries))

	for index, entry := range entries {
		entriesWithOptions[index] = append([]string{entry}, extraOptions...)
	}

	return set.RefreshWithBuiltinOptions(entriesWithOptions)
}

// RefreshWithBuiltinOptions refresh a Set with new entries with built-in options.
func (set *Set) RefreshWithBuiltinOptions(entries [][]string) error {
	var err error

	// The set-name must be < 32 characters!
	tempName := set.Name + "-"

	newSet := &Set{
		Parent:  set.Parent,
		Name:    tempName,
		Options: set.Options,
	}

	err = set.Parent.Add(newSet)
	if err != nil {
		return err
	}

	err = newSet.BatchAdd(entries)
	if err != nil {
		return err
	}

	err = set.Swap(newSet)
	if err != nil {
		return err
	}

	err = set.Parent.Destroy(tempName)
	if err != nil {
		return err
	}

	return nil
}
