package link

import (
	"encoding/json"
	"git.novox.be/novox/mesh-contracts/go/seats/nodeengine"
	sdkkeys "git.novox.be/novox/mesh-sdk/go/keys"
	"slices"
	"sort"
	"strings"
	"sync"
	"time"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
)

// The node's record (novox/hq ADR 0555 §3, issue 1126): what the machine observes of itself, written in its own have key
// `<node>.node` (nodeengine.HaveByNodeNodeValue.Record) with its facts, so every node and the parts that compose read it from the bus
// and hear its change as the key's. Each value is the one the controller took from this node's enrolment and reports
// until now (its profile's present capabilities and networks, its outward links, its health statement's contract, and
// the public halves of the keys it enrolled with), read here from the same sources, never from the controller.

// RecordKeys are the public halves the node holds and the certificate the mesh issued for its internal name, as read
// from its state directory at the time of a pass: the certificate arrives after enrolment, a rekey changes the tunnel key.
type RecordKeys struct {
	TunnelKey   string
	SealingKey  string
	ServingKey  string
	Certificate string
	// Authority is the mesh's own certificate as this machine last applied it (public).
	Authority string
	// Trusts is what this machine trusts a mesh signature from now (delivery.Trusts, ADR 0550 §2).
	Trusts []string
	// Stated is the capabilities its tool runner states of the calls it answers (CapabilitiesKey), which the record says
	// beside the machine's own: a module whose manifest asks for one is held off a machine whose runner does not state it.
	Stated []string
}

// buildReads are the words and forms this engine reads of a manifest (novox/hq ADR 0614 §4): the reader capabilities of
// the mesh-sdk it is built with, its seats left out. Computed once: they are the build's, and never change while it runs.
var buildReads = sync.OnceValue(func() []string {
	return slices.DeleteFunc(catalogue.ManifestReads(), func(r string) bool { return strings.HasPrefix(r, catalogue.ReadSeat) })
})

// readsNow is what this engine reads of a manifest now: its build's words and forms, and the seats of the seat list it
// holds now (catalogue.Seats, which the engine's reader of the list gives catalogue: bootstrapped or read; ADR 0636).
func readsNow() []string {
	set := map[string]bool{}
	for _, r := range buildReads() {
		set[r] = true
	}
	for _, seat := range catalogue.Seats() {
		set[catalogue.ReadSeat+seat.Name] = true
	}
	out := make([]string, 0, len(set))
	for r := range set {
		out = append(out, r)
	}
	sort.Strings(out)
	return out
}

// readsStatement is what this engine states it reads and since when (the verb manifest-reads, ADR 0618 §3): made at its
// first reading, and made again by Restate whenever the seat list it holds changes what it reads (ADR 0618 §4). The seat
// list is the process's, so the statement is too.
type readsStatement struct {
	mu    sync.Mutex
	reads []string
	at    time.Time
}

var stated readsStatement

// now is the statement, made at the first reading.
func (s *readsStatement) now() ([]string, time.Time) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.reads == nil {
		s.reads, s.at = readsNow(), time.Now().UTC()
	}
	return slices.Clone(s.reads), s.at
}

// restate makes the statement again from what the engine reads now, and says whether it changed.
func (s *readsStatement) restate() ([]string, bool) {
	cur := readsNow()
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.reads != nil && slices.Equal(cur, s.reads) {
		return slices.Clone(cur), false
	}
	s.reads, s.at = cur, time.Now().UTC()
	return slices.Clone(cur), true
}

// manifestReads is what this engine states it reads of a manifest now, which its record carries.
func manifestReads() []string {
	reads, _ := stated.now()
	return reads
}

// recordOf is the node's record from one facts report and its keys; nil for a report that carries no profile (one that
// says nothing of the machine, such as a rekey), so the record last written stands.
func recordOf(node string, r Report, keys RecordKeys) *nodeengine.NodeRecord {
	if r.Profile == nil {
		return nil
	}
	var p struct {
		Capabilities []struct {
			Name    string `json:"name"`
			Present bool   `json:"present"`
		} `json:"capabilities"`
		Machine *struct {
			Networks []catalogue.AttachedNetwork `json:"networks"`
		} `json:"machine"`
	}
	raw, err := json.Marshal(r.Profile)
	if err != nil || json.Unmarshal(raw, &p) != nil {
		return nil
	}
	rec := &nodeengine.NodeRecord{V: sdkkeys.Version, Node: node, TunnelKey: keys.TunnelKey, SealingKey: keys.SealingKey,
		ServingKey: keys.ServingKey, Certificate: keys.Certificate, Authority: keys.Authority, Trusts: keys.Trusts,
		ManifestReads: manifestReads()}
	for _, c := range p.Capabilities {
		if c.Present && c.Name != "" {
			rec.Capabilities = append(rec.Capabilities, c.Name)
		}
	}
	for _, c := range keys.Stated {
		if c != "" && !slices.Contains(rec.Capabilities, c) {
			rec.Capabilities = append(rec.Capabilities, c)
		}
	}
	sort.Strings(rec.Capabilities)
	if p.Machine != nil {
		rec.NetworksSaid = true
		for _, n := range p.Machine.Networks {
			rec.Networks = append(rec.Networks, nodeengine.AttachedNetwork{Link: n.Link, Network: n.Network})
		}
	}
	if len(r.Outward) > 0 {
		rec.OutwardLinks = append([]string(nil), r.Outward...)
	}
	if r.Health != nil {
		rec.Contract = int64(r.Health.Contract)
	}
	return rec
}