package model

import "fmt"

// Chains rules are placed in.
const (
	// ChainEarly sees packets before connection tracking (prerouting,
	// priority raw): cheap drops, antispoofing.
	ChainEarly = "early"
	// ChainInput is traffic to the firewall itself.
	ChainInput = "input"
	// ChainForward is traffic through the firewall.
	ChainForward = "forward"
	// ChainOutput is traffic from the firewall itself.
	ChainOutput = "output"
)

// Chains lists the rule chains in display order.
var Chains = []string{ChainEarly, ChainInput, ChainForward, ChainOutput}

// ChainOrder is a chain's place in Chains.
func ChainOrder(c string) int {
	for i, x := range Chains {
		if x == c {
			return i
		}
	}
	return len(Chains)
}

// Rule actions.
const (
	ActionAccept = "accept"
	ActionDrop   = "drop"
	ActionReject = "reject"
	// ActionLog only logs (and counts); the packet goes on to the next
	// rule.
	ActionLog = "log"
)

// Actions lists the rule actions.
var Actions = []string{ActionAccept, ActionDrop, ActionReject, ActionLog}

// Families a rule can be limited to; "" is both.
const (
	FamilyIPv4 = "ipv4"
	FamilyIPv6 = "ipv6"
)

// Zone is a group of interfaces (wildcards such as "incus*" allowed).
// External zones face the internet: built-ins such as antispoofing and
// MSS clamping apply to them.
type Zone struct {
	ID         int64    `json:"id"`
	Name       string   `json:"name"`
	Interfaces []string `json:"interfaces"`
	External   bool     `json:"external,omitempty"`
	Comment    string   `json:"comment,omitempty"`
}

func (z *Zone) GetID() int64  { return z.ID }
func (z *Zone) Label() string { return z.Name }

// AddressSet is a named list of IPv4 and IPv6 addresses, prefixes and
// ranges. A dynamic set also takes entries at run time, each with a
// timeout, through its own API (a captive portal's signed-in clients).
type AddressSet struct {
	ID      int64    `json:"id"`
	Name    string   `json:"name"`
	Entries []string `json:"entries"`
	Dynamic bool     `json:"dynamic,omitempty"`
	// Timeout is a dynamic set's default entry lifetime in seconds (0:
	// entries stay until removed).
	Timeout int    `json:"timeout,omitempty"`
	Comment string `json:"comment,omitempty"`
}

func (s *AddressSet) GetID() int64  { return s.ID }
func (s *AddressSet) Label() string { return s.Name }

// Service is a named list of ports ("tcp/22", "udp/60000-61000") and ICMP
// types ("icmp/echo-request", "icmpv6/packet-too-big"). Rules name
// services, or give such entries directly.
type Service struct {
	ID      int64    `json:"id"`
	Name    string   `json:"name"`
	Entries []string `json:"entries"`
	Comment string   `json:"comment,omitempty"`
	// Builtin marks the catalog's services (never stored).
	Builtin bool `json:"builtin,omitempty"`
}

func (s *Service) GetID() int64  { return s.ID }
func (s *Service) Label() string { return s.Name }

// Match is what a rule, port forward, source NAT or redirect looks at.
// Lists are ORed; the fields together are ANDed.
type Match struct {
	// InZones and OutZones are zone names; with NotIn/NotOut, every zone
	// but those.
	InZones  []string `json:"in_zones,omitempty"`
	NotIn    bool     `json:"not_in,omitempty"`
	OutZones []string `json:"out_zones,omitempty"`
	NotOut   bool     `json:"not_out,omitempty"`
	// Sources and Destinations are set names or literal addresses,
	// prefixes and ranges, IPv4 or IPv6.
	Sources      []string `json:"sources,omitempty"`
	NotSources   bool     `json:"not_sources,omitempty"`
	Destinations []string `json:"destinations,omitempty"`
	NotDests     bool     `json:"not_destinations,omitempty"`
	// Services are service names or entries ("tcp/22", "icmp/echo-request").
	Services []string `json:"services,omitempty"`
	// Family limits the rule to ipv4 or ipv6 ("": what its addresses
	// and services allow).
	Family string `json:"family,omitempty"`
}

// Rule is one line of a chain, checked in order.
type Rule struct {
	ID       int64   `json:"id"`
	Chain    string  `json:"chain"`
	Position float64 `json:"position"`
	Match
	// CtState: new, established, related, invalid, untracked.
	CtState []string `json:"ct_state,omitempty"`
	// CtStatus: dnat, snat (a connection that was NATed).
	CtStatus []string `json:"ct_status,omitempty"`
	// Days ("Monday", …) and hours ("08:00"-"17:30") the rule applies.
	Days     []string `json:"days,omitempty"`
	HourFrom string   `json:"hour_from,omitempty"`
	HourTo   string   `json:"hour_to,omitempty"`
	// Limit, if set, makes the rule match only packets within (or with
	// LimitOver, beyond) a rate.
	Limit *Limit `json:"limit,omitempty"`
	// ConnLimit matches when a source already has more than this many
	// connections (per source address, grouped as GroupV4/GroupV6 say).
	ConnLimit int `json:"conn_limit,omitempty"`
	// Quota, if set, is an allowance of bytes: the rule matches once it
	// is used up (Over), or while it lasts.
	Quota *Quota `json:"quota,omitempty"`
	// GroupV4 and GroupV6 group addresses for the per-address limits,
	// connection limit and quota: by prefix length (0: the default, each
	// IPv4 address alone, IPv6 by /64, since one device has several).
	GroupV4 int `json:"group_v4,omitempty"`
	GroupV6 int `json:"group_v6,omitempty"`
	// EveryPacket checks the rule against every packet, before established
	// connections are accepted, so a drop or reject also stops connections
	// already open, not just new ones.
	EveryPacket bool   `json:"every_packet,omitempty"`
	Action      string `json:"action"`
	// RejectWith: "" (ICMP port/admin unreachable as fits) or tcp-reset.
	RejectWith string `json:"reject_with,omitempty"`
	Log        bool   `json:"log,omitempty"`
	LogPrefix  string `json:"log_prefix,omitempty"`
	// Raw, when set, is an nftables rule written by hand, used instead of
	// the fields above (the escape hatch for what Housecarl can't say).
	Raw      string `json:"raw,omitempty"`
	Comment  string `json:"comment,omitempty"`
	Disabled bool   `json:"disabled,omitempty"`
}

func (r *Rule) GetID() int64 { return r.ID }
func (r *Rule) Label() string {
	if r.Comment != "" {
		return fmt.Sprintf("%s #%d (%s)", r.Chain, r.ID, r.Comment)
	}
	return fmt.Sprintf("%s #%d", r.Chain, r.ID)
}

// Limit is a rate: Rate packets (or bytes, with Unit) per Per (second,
// minute, hour, day), with a burst.
type Limit struct {
	Rate int    `json:"rate"`
	Per  string `json:"per"`
	// Burst is in the rate's unit.
	Burst int `json:"burst,omitempty"`
	// Unit: "" for packets, or bytes, kbytes or mbytes for a byte rate
	// (bandwidth).
	Unit string `json:"unit,omitempty"`
	// Over matches packets beyond the rate instead of within it (to drop
	// floods).
	Over bool `json:"over,omitempty"`
	// PerSource counts each source address on its own (a meter), instead
	// of all traffic the rule sees together; PerDestination each
	// destination.
	PerSource      bool `json:"per_source,omitempty"`
	PerDestination bool `json:"per_destination,omitempty"`
}

// Byte units, as nftables writes them.
var ByteUnits = map[string]int64{"bytes": 1, "kbytes": 1 << 10, "mbytes": 1 << 20, "gbytes": 1 << 30}

// Quota is an allowance of bytes. nftables counts it; Housecarl keeps the
// count across changes and restarts, and resets it each period.
type Quota struct {
	Bytes int64 `json:"bytes"`
	// Over matches once the allowance is used up (to drop); otherwise the
	// rule matches while it lasts (to accept).
	Over bool `json:"over,omitempty"`
	// PerSource gives each source address (grouped as the rule's
	// GroupV4/GroupV6 say) its own allowance; PerDestination each
	// destination.
	PerSource      bool `json:"per_source,omitempty"`
	PerDestination bool `json:"per_destination,omitempty"`
	// Reset: "" (only by hand), daily, weekly (on Mondays) or monthly (on
	// Day, 1-31: a short month's last day when it has no such day), at
	// midnight.
	Reset string `json:"reset,omitempty"`
	Day   int    `json:"day,omitempty"`
}

// Quota resets.
var QuotaResets = []string{"daily", "weekly", "monthly"}

// PerAddress reports whether a quota (or limit) counts each address on its
// own, and which: "saddr", "daddr" or "".
func (q *Quota) PerAddress() string {
	switch {
	case q == nil:
		return ""
	case q.PerSource:
		return "saddr"
	case q.PerDestination:
		return "daddr"
	}
	return ""
}

// PerAddress: as Quota's.
func (l *Limit) PerAddress() string {
	switch {
	case l == nil:
		return ""
	case l.PerSource:
		return "saddr"
	case l.PerDestination:
		return "daddr"
	}
	return ""
}

// CountsTraffic reports whether a rule measures traffic (a quota or a byte
// rate): it must see every packet of a connection, so it is checked before
// the built-in that accepts established connections.
func (r *Rule) CountsTraffic() bool {
	if r.Raw != "" {
		return false
	}
	if r.Quota != nil {
		return true
	}
	if r.Limit == nil {
		return false
	}
	_, bytes := ByteUnits[r.Limit.Unit]
	return bytes
}

// ChecksEveryPacket reports whether a rule is checked before the built-in
// that accepts established connections: it counts traffic, or asks to.
func (r *Rule) ChecksEveryPacket() bool {
	return r.Raw == "" && (r.EveryPacket || r.CountsTraffic())
}

// Groups returns a rule's address grouping, defaults applied.
func (r *Rule) Groups() (v4, v6 int) {
	v4, v6 = r.GroupV4, r.GroupV6
	if v4 == 0 {
		v4 = 32
	}
	if v6 == 0 {
		v6 = 64
	}
	return v4, v6
}

// PortForward publishes a service on an inside host: incoming connections
// to a public address and port are sent on (DNAT) to To[:ToPort], let
// through the forward chain, and, with Hairpin, also work from inside.
// To6 also opens the port to an IPv6 host (a pinhole; no translation).
type PortForward struct {
	ID       int64   `json:"id"`
	Position float64 `json:"position"`
	Name     string  `json:"name,omitempty"`
	// Protocols: tcp, udp (default tcp).
	Protocols []string `json:"protocols"`
	// Ports is the public port or range ("8096", "7777-7780").
	Ports string `json:"ports"`
	// PublicAddresses are the IPv4 addresses (or set names) to match;
	// none means any address on the external zones' interfaces (and then
	// no hairpin).
	PublicAddresses []string `json:"public_addresses,omitempty"`
	// Sources limits who may connect (set names or addresses).
	Sources []string `json:"sources,omitempty"`
	To      string   `json:"to,omitempty"`
	// ToPort is the inside port ("" keeps the public one; for a range, the
	// first port of an equally long range).
	ToPort string `json:"to_port,omitempty"`
	To6    string `json:"to6,omitempty"`
	// Hairpin lets inside clients use the public address: their
	// connections are masqueraded so replies come back through the
	// firewall. HairpinSources limits that to some sources (none: all
	// inside traffic).
	Hairpin        bool     `json:"hairpin,omitempty"`
	HairpinSources []string `json:"hairpin_sources,omitempty"`
	Comment        string   `json:"comment,omitempty"`
	Disabled       bool     `json:"disabled,omitempty"`
}

func (f *PortForward) GetID() int64 { return f.ID }
func (f *PortForward) Label() string {
	if f.Name != "" {
		return f.Name
	}
	return fmt.Sprintf("port forward #%d (%s)", f.ID, f.Ports)
}

// SourceNAT rewrites the source address of outgoing traffic: masquerade
// (To empty: the outgoing interface's address) or SNAT to To.
type SourceNAT struct {
	ID       int64   `json:"id"`
	Position float64 `json:"position"`
	Match
	To       string `json:"to,omitempty"`
	Comment  string `json:"comment,omitempty"`
	Disabled bool   `json:"disabled,omitempty"`
}

func (s *SourceNAT) GetID() int64 { return s.ID }
func (s *SourceNAT) Label() string {
	if s.Comment != "" {
		return fmt.Sprintf("source NAT #%d (%s)", s.ID, s.Comment)
	}
	return fmt.Sprintf("source NAT #%d", s.ID)
}

// Redirect sends matching traffic to a port on the firewall itself (to
// make every client use its DNS server, say).
type Redirect struct {
	ID       int64   `json:"id"`
	Position float64 `json:"position"`
	Match
	// ToPort is the local port (the services' first port when empty).
	ToPort   string `json:"to_port,omitempty"`
	Comment  string `json:"comment,omitempty"`
	Disabled bool   `json:"disabled,omitempty"`
}

func (r *Redirect) GetID() int64 { return r.ID }
func (r *Redirect) Label() string {
	if r.Comment != "" {
		return fmt.Sprintf("redirect #%d (%s)", r.ID, r.Comment)
	}
	return fmt.Sprintf("redirect #%d", r.ID)
}