// Package model holds Housecarl's data: the firewall configuration
// (State), users and tokens, the history of changes and the audit log.
package model

import (
	"encoding/json"
	"sort"
	"strings"
)

// State is the whole firewall configuration. It is small and changed as a
// whole (internal/engine); the ruleset is rendered from it
// (internal/render).
type State struct {
	Settings  Settings       `json:"settings"`
	Zones     []*Zone        `json:"zones"`
	Sets      []*AddressSet  `json:"sets"`
	Services  []*Service     `json:"services"`
	Rules     []*Rule        `json:"rules"`
	Forwards  []*PortForward `json:"forwards"`
	SNATs     []*SourceNAT   `json:"snats"`
	Redirects []*Redirect    `json:"redirects"`
	BanLists  []*BanList     `json:"ban_lists"`
}

// Object kinds, for changes and the history.
const (
	KindSettings = "settings"
	KindZone     = "zone"
	KindSet      = "set"
	KindService  = "service"
	KindRule     = "rule"
	KindForward  = "forward"
	KindSNAT     = "snat"
	KindRedirect = "redirect"
	KindBanList  = "banlist"
)

// Kinds lists the object kinds (not settings) in display order.
var Kinds = []string{KindZone, KindSet, KindService, KindRule, KindForward, KindSNAT, KindRedirect, KindBanList}

// Object is anything in the State with an ID.
type Object interface {
	GetID() int64
	Label() string
}

// NewState is an empty configuration with the default settings.
func NewState() *State {
	st := &State{Settings: DefaultSettings()}
	st.Fill()
	return st
}

// Fill replaces nil lists with empty ones (for JSON and comparisons).
func (st *State) Fill() {
	if st.Zones == nil {
		st.Zones = []*Zone{}
	}
	if st.Sets == nil {
		st.Sets = []*AddressSet{}
	}
	if st.Services == nil {
		st.Services = []*Service{}
	}
	if st.Rules == nil {
		st.Rules = []*Rule{}
	}
	if st.Forwards == nil {
		st.Forwards = []*PortForward{}
	}
	if st.SNATs == nil {
		st.SNATs = []*SourceNAT{}
	}
	if st.Redirects == nil {
		st.Redirects = []*Redirect{}
	}
	if st.BanLists == nil {
		st.BanLists = []*BanList{}
	}
}

// Objects returns the objects of a kind.
func (st *State) Objects(kind string) []Object {
	var out []Object
	switch kind {
	case KindZone:
		for _, o := range st.Zones {
			out = append(out, o)
		}
	case KindSet:
		for _, o := range st.Sets {
			out = append(out, o)
		}
	case KindService:
		for _, o := range st.Services {
			out = append(out, o)
		}
	case KindRule:
		for _, o := range st.Rules {
			out = append(out, o)
		}
	case KindForward:
		for _, o := range st.Forwards {
			out = append(out, o)
		}
	case KindSNAT:
		for _, o := range st.SNATs {
			out = append(out, o)
		}
	case KindRedirect:
		for _, o := range st.Redirects {
			out = append(out, o)
		}
	case KindBanList:
		for _, o := range st.BanLists {
			out = append(out, o)
		}
	}
	return out
}

// Put replaces (or adds, or with data nil deletes) the object of a kind
// with an ID, from its JSON.
// Empty reports whether nothing has been configured: no objects of any
// kind. housecarld applies no ruleset for an empty configuration, so
// installing and starting it doesn't close the machine.
func (st *State) Empty() bool {
	for _, k := range Kinds {
		if len(st.Objects(k)) > 0 {
			return false
		}
	}
	return true
}

func (st *State) Put(kind string, id int64, data json.RawMessage) error {
	switch kind {
	case KindZone:
		return put(&st.Zones, id, data)
	case KindSet:
		return put(&st.Sets, id, data)
	case KindService:
		return put(&st.Services, id, data)
	case KindRule:
		return put(&st.Rules, id, data)
	case KindForward:
		return put(&st.Forwards, id, data)
	case KindSNAT:
		return put(&st.SNATs, id, data)
	case KindRedirect:
		return put(&st.Redirects, id, data)
	case KindBanList:
		return put(&st.BanLists, id, data)
	}
	return &unknownKind{kind}
}

type unknownKind struct{ kind string }

func (e *unknownKind) Error() string { return "unknown kind " + e.kind }

func put[T Object](list *[]T, id int64, data json.RawMessage) error {
	keep := (*list)[:0:0]
	for _, o := range *list {
		if o.GetID() != id {
			keep = append(keep, o)
		}
	}
	if data != nil {
		var o T
		if err := json.Unmarshal(data, &o); err != nil {
			return err
		}
		keep = append(keep, o)
	}
	*list = keep
	return nil
}

// Clone returns a deep copy.
func (st *State) Clone() *State {
	b, err := json.Marshal(st)
	if err != nil {
		panic(err)
	}
	var out State
	if err := json.Unmarshal(b, &out); err != nil {
		panic(err)
	}
	out.Fill()
	return &out
}

// Sort puts the objects in display order: named objects by name, rules by
// chain and position, NAT rules by position.
func (st *State) Sort() {
	sort.SliceStable(st.Zones, func(i, j int) bool { return st.Zones[i].Name < st.Zones[j].Name })
	sort.SliceStable(st.Sets, func(i, j int) bool { return st.Sets[i].Name < st.Sets[j].Name })
	sort.SliceStable(st.Services, func(i, j int) bool { return st.Services[i].Name < st.Services[j].Name })
	sort.SliceStable(st.BanLists, func(i, j int) bool { return st.BanLists[i].Name < st.BanLists[j].Name })
	sort.SliceStable(st.Rules, func(i, j int) bool {
		a, b := st.Rules[i], st.Rules[j]
		if a.Chain != b.Chain {
			return ChainOrder(a.Chain) < ChainOrder(b.Chain)
		}
		return a.Position < b.Position
	})
	sort.SliceStable(st.Forwards, func(i, j int) bool { return st.Forwards[i].Position < st.Forwards[j].Position })
	sort.SliceStable(st.SNATs, func(i, j int) bool { return st.SNATs[i].Position < st.SNATs[j].Position })
	sort.SliceStable(st.Redirects, func(i, j int) bool { return st.Redirects[i].Position < st.Redirects[j].Position })
}

// Renumber gives the rules of each chain, and the NAT rules of each kind,
// positions 1, 2, 3, … in their current order (after an insertion at a
// fractional position, or a deletion).
func (st *State) Renumber() {
	st.Sort()
	n := map[string]float64{}
	for _, r := range st.Rules {
		n[r.Chain]++
		r.Position = n[r.Chain]
	}
	for i, f := range st.Forwards {
		f.Position = float64(i + 1)
	}
	for i, s := range st.SNATs {
		s.Position = float64(i + 1)
	}
	for i, r := range st.Redirects {
		r.Position = float64(i + 1)
	}
}

// Zone finds a zone by name.
func (st *State) Zone(name string) *Zone {
	for _, z := range st.Zones {
		if strings.EqualFold(z.Name, name) {
			return z
		}
	}
	return nil
}

// Set finds an address set by name.
func (st *State) Set(name string) *AddressSet {
	for _, s := range st.Sets {
		if strings.EqualFold(s.Name, name) {
			return s
		}
	}
	return nil
}

// Service finds a service by name: the configuration's, else the built-in
// catalog's.
func (st *State) Service(name string) *Service {
	for _, s := range st.Services {
		if strings.EqualFold(s.Name, name) {
			return s
		}
	}
	return BuiltinService(name)
}

// ByID finds an object of a kind by ID (nil if there is none).
func (st *State) ByID(kind string, id int64) Object {
	for _, o := range st.Objects(kind) {
		if o.GetID() == id {
			return o
		}
	}
	return nil
}

// Find finds an object of a kind by ID or name (zones, sets, services,
// port forwards, ban lists) or by ID alone (rules, source NAT, redirects).
func (st *State) Find(kind, ref string) Object {
	for _, o := range st.Objects(kind) {
		if itoa(o.GetID()) == ref {
			return o
		}
	}
	switch kind {
	case KindZone:
		if z := st.Zone(ref); z != nil {
			return z
		}
	case KindSet:
		if s := st.Set(ref); s != nil {
			return s
		}
	case KindService:
		for _, s := range st.Services {
			if strings.EqualFold(s.Name, ref) {
				return s
			}
		}
	case KindForward:
		for _, f := range st.Forwards {
			if f.Name != "" && strings.EqualFold(f.Name, ref) {
				return f
			}
		}
	case KindBanList:
		if b := st.BanList(ref); b != nil {
			return b
		}
	}
	return nil
}

// BanList finds a ban list by name.
func (st *State) BanList(name string) *BanList {
	for _, b := range st.BanLists {
		if strings.EqualFold(b.Name, name) {
			return b
		}
	}
	return nil
}

func itoa(n int64) string {
	b, _ := json.Marshal(n)
	return string(b)
}

// ExternalInterfaces lists the interfaces of the external zones.
func (st *State) ExternalInterfaces() []string {
	return st.zoneInterfaces(func(z *Zone) bool { return z.External })
}

// InternalInterfaces lists the interfaces of the internal zones.
func (st *State) InternalInterfaces() []string {
	return st.zoneInterfaces(func(z *Zone) bool { return !z.External })
}

func (st *State) zoneInterfaces(keep func(*Zone) bool) []string {
	seen := map[string]bool{}
	var out []string
	for _, z := range st.Zones {
		if !keep(z) {
			continue
		}
		for _, i := range z.Interfaces {
			if !seen[i] {
				seen[i] = true
				out = append(out, i)
			}
		}
	}
	sort.Strings(out)
	return out
}