// Package model holds the fleet control-plane domain types and the
// shorewall-style source/dest element grammar shared by the API and compiler.
package model

import (
	"fmt"
	"strings"
	"time"
)

// DeviceClass is either a routed-core member or a zone-boundary firewall.
type DeviceClass string

const (
	ClassRouter   DeviceClass = "router"
	ClassFirewall DeviceClass = "firewall"
)

// AddressGroupType selects how an address group's nftables set is populated.
type AddressGroupType string

const (
	GroupStatic AddressGroupType = "static" // explicit CIDRs, populated by the API
	GroupDNS    AddressGroupType = "dns"    // FQDNs, resolved on-device
	GroupASN    AddressGroupType = "asn"    // ASNs, expanded centrally via iplocate
)

// Settings holds fleet-wide defaults. Individual devices may override a subset
// via their per-device settings.
type Settings struct {
	AddressFamily   string   `json:"address_family"`
	LogLevel        string   `json:"log_level"`
	IPForwarding    bool     `json:"ip_forwarding"`
	TableName       string   `json:"table_name"`
	DefaultResolver []string `json:"default_resolver"`
}

// PortGroup is a reusable proto+ports combo referenced by rules.
type PortGroup struct {
	Name  string   `json:"name"`
	Proto string   `json:"proto"`
	Ports []string `json:"ports"`
}

// Fabric is a routing domain. EnforceOnRouters toggles defense-in-depth (every
// router carries the intent) vs transparent transit (only boundary firewalls do).
type Fabric struct {
	Name             string `json:"name"`
	EnforceOnRouters bool   `json:"enforce_on_routers"`
	Description      string `json:"description,omitempty"`
}

// Policy is a fleet-global default zone-to-zone posture. Lower priority evaluates
// first (first match wins).
type Policy struct {
	ID       int64  `json:"id"`
	Priority int    `json:"priority"`
	Source   string `json:"source"`
	Dest     string `json:"dest"`
	Action   string `json:"action"`
	Log      string `json:"log,omitempty"`
}

// Zone is a fleet-global network segment.
type Zone struct {
	Name    string   `json:"name" yaml:"-"`
	Type    string   `json:"type" yaml:"type"`
	Subnets []string `json:"subnets" yaml:"-"`
	Parent  string   `json:"parent,omitempty" yaml:"parents,omitempty"`
}

// AddressGroup materializes an nftables named set.
type AddressGroup struct {
	Name        string           `json:"name"`
	Type        AddressGroupType `json:"type"`
	Members     []string         `json:"members"`
	Refresh     string           `json:"refresh,omitempty"`
	Description string           `json:"description,omitempty"`

	// Resolved holds concrete CIDRs the ASN expander last produced (asn groups
	// only); ResolvedAt timestamps that expansion. Both are server-managed.
	Resolved   []string   `json:"resolved,omitempty"`
	ResolvedAt *time.Time `json:"resolved_at,omitempty"`
}

// SetName returns the nftables set name for this group. ASN groups get the
// reserved asn_ prefix; others use their bare name.
func (g AddressGroup) SetName() string {
	if g.Type == GroupASN && !strings.HasPrefix(g.Name, "asn_") {
		return "asn_" + g.Name
	}
	return g.Name
}

// Device is a fleet member.
type Device struct {
	Name     string            `json:"name"`
	Class    DeviceClass       `json:"class"`
	Fabric   string            `json:"fabric,omitempty"`
	Resolver []string          `json:"resolver,omitempty"`
	Settings map[string]string `json:"settings,omitempty"`

	// ReachablePrefixes is the device's FIB as last reported by its agent
	// (server-managed). The compiler uses it to scope router enforcement.
	ReachablePrefixes []string `json:"reachable_prefixes,omitempty"`
}

// Binding maps a global zone to one device's local interface(s).
type Binding struct {
	Device     string   `json:"device"`
	Zone       string   `json:"zone"`
	Interfaces []string `json:"interfaces"`
}

// Rule is a fleet-global intent. Source and Dest are element lists (OR'd).
type Rule struct {
	ID        int64    `json:"id"`
	Priority  int      `json:"priority"`
	Action    string   `json:"action"`
	Source    []string `json:"source"`
	Dest      []string `json:"dest"`
	Proto     string   `json:"proto,omitempty"`
	PortGroup string   `json:"portgroup,omitempty"`
	Ports     []string `json:"ports,omitempty"`
	Log       string   `json:"log,omitempty"`
	Comment   string   `json:"comment,omitempty"`
}

// Selector kinds within a source/dest element.
type SelectorKind string

const (
	SelIPSet SelectorKind = "ipset" // +name
	SelFQDN  SelectorKind = "fqdn"  // &name
	SelNone  SelectorKind = ""      // bare zone
)

// Element is one comma-separated token of a source/dest list. A zone is always
// present; the selector, when set, narrows within that zone (an AND).
type Element struct {
	Zone     string
	Selector SelectorKind
	Ref      string // the ipset/fqdn-group name when Selector != SelNone
}

// ParseElement parses a single shorewall-style element:
//
//	loc                     -> bare zone
//	net:+asn_cloudflare     -> zone gated by an ipset
//	dmz:&api.partner        -> zone gated by an fqdn group
//
// A bare selector (no zone) is rejected: every selector must be paired with a zone.
func ParseElement(s string) (Element, error) {
	s = strings.TrimSpace(s)
	if s == "" {
		return Element{}, fmt.Errorf("empty element")
	}

	// Reject a leading selector sigil: bare selectors are not allowed.
	if s[0] == '+' || s[0] == '&' {
		return Element{}, fmt.Errorf("selector %q must be paired with a zone (write zone:%s)", s, s)
	}

	zone, sel, hasSel := strings.Cut(s, ":")
	zone = strings.TrimSpace(zone)
	if zone == "" {
		return Element{}, fmt.Errorf("element %q has an empty zone", s)
	}
	e := Element{Zone: zone, Selector: SelNone}
	if !hasSel {
		return e, nil
	}

	sel = strings.TrimSpace(sel)
	if sel == "" {
		return Element{}, fmt.Errorf("element %q has a trailing colon with no selector", s)
	}
	switch sel[0] {
	case '+':
		e.Selector, e.Ref = SelIPSet, sel[1:]
	case '&':
		e.Selector, e.Ref = SelFQDN, sel[1:]
	default:
		return Element{}, fmt.Errorf("selector %q must start with + (ipset) or & (fqdn)", sel)
	}
	if e.Ref == "" {
		return Element{}, fmt.Errorf("element %q has an empty selector reference", s)
	}
	return e, nil
}

// ParseElements parses and validates a full source/dest element list.
func ParseElements(list []string) ([]Element, error) {
	out := make([]Element, 0, len(list))
	for _, s := range list {
		e, err := ParseElement(s)
		if err != nil {
			return nil, err
		}
		out = append(out, e)
	}
	return out, nil
}