// Command playground is an all-in-one, web-based sandbox for the unibus message
// bus. A single `go run ./playground` launches the entire stack embedded:
//
//   - an embedded NATS server with JetStream (the data plane),
//   - the membership control plane (rooms, members, sealed keys, rekey) over an
//     internal HTTP server,
//   - the media blob store, and
//   - a browser-facing web UI on :7700.
//
// The browser never speaks NATS. The Go server is the actual bus peer: it holds
// one unibus client per named peer, subscribes to rooms on the peer's behalf,
// and streams received messages to the browser over Server-Sent Events. The
// browser drives everything with plain fetch() + EventSource() — no build step,
// no JS framework, no external libraries.
//
// This is a playground (see .claude/rules/playgrounds.md): it lives inside the
// unibus app, reuses the parent module (no new go.mod), is not indexed, and
// stores ephemeral state under playground/local_files/.
package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"sync"
	"syscall"
	"time"

	_ "embed"

	"github.com/enmanuel/unibus/pkg/blobstore"
	"github.com/enmanuel/unibus/pkg/client"
	"github.com/enmanuel/unibus/pkg/embeddednats"
	"github.com/enmanuel/unibus/pkg/frame"
	"github.com/enmanuel/unibus/pkg/membership"
	"github.com/enmanuel/unibus/pkg/room"
)

// Fixed ports (verified free before assignment — do not change without reason).
const (
	webAddr   = "127.0.0.1:7700" // browser-facing web UI
	ctrlAddr  = "127.0.0.1:8480" // internal membership control plane
	ctrlURL   = "http://" + ctrlAddr
	natsPort  = 4260 // internal embedded NATS
	natsURL   = "nats://127.0.0.1:4260"
	localFiles = "playground/local_files"
)

//go:embed index.html
var indexHTML []byte

// ---------------------------------------------------------------------------
// Event: a message received by a peer on one of its subscribed rooms. Fanned
// out to every SSE listener attached to that peer.
// ---------------------------------------------------------------------------

type Event struct {
	RoomID    string `json:"room_id"`
	Subject   string `json:"subject"`
	Sender    string `json:"sender"`
	Text      string `json:"text"`
	Encrypted bool   `json:"encrypted"`
	TS        int64  `json:"ts"` // unix millis
}

// roomInfo caches the per-room metadata a peer needs to label incoming frames.
type roomInfo struct {
	subject string
	encrypt bool
}

// peerState holds everything about one named peer: its bus client, its public
// endpoint, its live subscriptions, the rooms it knows, and the set of SSE
// listener channels currently attached to it.
type peerState struct {
	name     string
	client   *client.Client
	endpoint client.Endpoint

	mu        sync.Mutex
	subs      map[string]*client.Sub  // roomID -> subscription
	rooms     map[string]roomInfo     // roomID -> subject/encrypt
	listeners map[chan Event]struct{} // attached SSE channels
}

// emit fans an event out to all attached listeners without blocking on a slow
// or disconnected consumer.
func (p *peerState) emit(ev Event) {
	p.mu.Lock()
	defer p.mu.Unlock()
	for ch := range p.listeners {
		select {
		case ch <- ev:
		default: // listener buffer full: drop rather than block the NATS callback
		}
	}
}

func (p *peerState) addListener(ch chan Event) {
	p.mu.Lock()
	p.listeners[ch] = struct{}{}
	p.mu.Unlock()
}

func (p *peerState) removeListener(ch chan Event) {
	p.mu.Lock()
	delete(p.listeners, ch)
	p.mu.Unlock()
}

func (p *peerState) setRoom(roomID string, info roomInfo) {
	p.mu.Lock()
	p.rooms[roomID] = info
	p.mu.Unlock()
}

// ---------------------------------------------------------------------------
// Hub: the registry of peers, protected by a single mutex.
// ---------------------------------------------------------------------------

type Hub struct {
	mu    sync.Mutex
	peers map[string]*peerState
}

func newHub() *Hub { return &Hub{peers: map[string]*peerState{}} }

// getOrCreate returns the peer for name, creating its identity + bus client on
// first use. Identities persist to playground/local_files/<name>.id so a peer
// keeps the same endpoint across restarts.
func (h *Hub) getOrCreate(name string) (*peerState, error) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if p, ok := h.peers[name]; ok {
		return p, nil
	}
	idPath := filepath.Join(localFiles, name+".id")
	id, err := client.LoadOrCreateIdentity(idPath)
	if err != nil {
		return nil, fmt.Errorf("identity for %q: %w", name, err)
	}
	c, err := client.New(natsURL, ctrlURL, id)
	if err != nil {
		return nil, fmt.Errorf("client for %q: %w", name, err)
	}
	p := &peerState{
		name:      name,
		client:    c,
		endpoint:  c.Endpoint(),
		subs:      map[string]*client.Sub{},
		rooms:     map[string]roomInfo{},
		listeners: map[chan Event]struct{}{},
	}
	h.peers[name] = p
	return p, nil
}

// lookup returns an already-created peer or false.
func (h *Hub) lookup(name string) (*peerState, bool) {
	h.mu.Lock()
	defer h.mu.Unlock()
	p, ok := h.peers[name]
	return p, ok
}

// list returns a snapshot of all peers (name + endpoint id).
func (h *Hub) list() []map[string]string {
	h.mu.Lock()
	defer h.mu.Unlock()
	out := make([]map[string]string, 0, len(h.peers))
	for name, p := range h.peers {
		out = append(out, map[string]string{"name": name, "endpoint_id": p.endpoint.ID})
	}
	return out
}

func (h *Hub) closeAll() {
	h.mu.Lock()
	defer h.mu.Unlock()
	for _, p := range h.peers {
		p.mu.Lock()
		for _, sub := range p.subs {
			_ = sub.Unsubscribe()
		}
		p.mu.Unlock()
		_ = p.client.Close()
	}
}

// subscribeRoom subscribes the peer to a room (idempotent) and wires the frame
// handler to fan incoming messages out as Events. info labels each event with
// the room's subject and encryption flag.
func (p *peerState) subscribeRoom(roomID string, info roomInfo) error {
	p.mu.Lock()
	if _, already := p.subs[roomID]; already {
		p.mu.Unlock()
		return nil
	}
	p.mu.Unlock()

	sub, err := p.client.Subscribe(roomID, func(f frame.Frame, plaintext []byte) {
		p.emit(Event{
			RoomID:    roomID,
			Subject:   info.subject,
			Sender:    f.Sender,
			Text:      string(plaintext),
			Encrypted: info.encrypt,
			TS:        time.Now().UnixMilli(),
		})
	})
	if err != nil {
		return fmt.Errorf("subscribe room %s: %w", roomID, err)
	}
	p.mu.Lock()
	p.subs[roomID] = sub
	p.mu.Unlock()
	p.setRoom(roomID, info)
	return nil
}

// ---------------------------------------------------------------------------
// Control-plane helper: fetch a room's subject + policy from membershipd. The
// client package keeps fetchRoom private, so the playground talks to the
// control plane directly (read endpoints are unauthenticated by design).
// ---------------------------------------------------------------------------

type ctrlRoomResp struct {
	Subject string `json:"subject"`
	Epoch   int    `json:"epoch"`
	Policy  struct {
		Encrypt  bool `json:"encrypt"`
		Persist  bool `json:"persist"`
		SignMsgs bool `json:"sign_msgs"`
	} `json:"policy"`
}

func fetchRoomInfo(roomID string) (roomInfo, error) {
	resp, err := http.Get(ctrlURL + "/rooms/" + roomID)
	if err != nil {
		return roomInfo{}, fmt.Errorf("fetch room %s: %w", roomID, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		return roomInfo{}, fmt.Errorf("room %s not found (status %d)", roomID, resp.StatusCode)
	}
	var r ctrlRoomResp
	if err := json.NewDecoder(resp.Body).Decode(&r); err != nil {
		return roomInfo{}, fmt.Errorf("decode room %s: %w", roomID, err)
	}
	return roomInfo{subject: r.Subject, encrypt: r.Policy.Encrypt}, nil
}

// ---------------------------------------------------------------------------
// HTTP handlers (web UI on :7700).
// ---------------------------------------------------------------------------

func writeJSON(w http.ResponseWriter, code int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(v)
}

func writeErr(w http.ResponseWriter, code int, msg string) {
	writeJSON(w, code, map[string]string{"error": msg})
}

func decodeBody(r *http.Request, out any) error {
	defer r.Body.Close()
	return json.NewDecoder(r.Body).Decode(out)
}

func (h *Hub) handleIndex(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_, _ = w.Write(indexHTML)
}

func (h *Hub) handlePeer(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Name string `json:"name"`
	}
	if err := decodeBody(r, &req); err != nil || req.Name == "" {
		writeErr(w, http.StatusBadRequest, "name required")
		return
	}
	p, err := h.getOrCreate(req.Name)
	if err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"name": p.name, "endpoint_id": p.endpoint.ID})
}

func (h *Hub) handlePeers(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, h.list())
}

func (h *Hub) handleRoom(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Peer    string `json:"peer"`
		Subject string `json:"subject"`
		Encrypt bool   `json:"encrypt"`
		Persist bool   `json:"persist"`
	}
	if err := decodeBody(r, &req); err != nil || req.Peer == "" || req.Subject == "" {
		writeErr(w, http.StatusBadRequest, "peer and subject required")
		return
	}
	p, ok := h.lookup(req.Peer)
	if !ok {
		writeErr(w, http.StatusBadRequest, "unknown peer "+req.Peer)
		return
	}
	// The two checkboxes map to an explicit per-room policy. encrypt drives both
	// encryption and per-message signing; persist (default false) independently
	// toggles durable JetStream history. persist=false keeps plain ephemeral NATS.
	policy := room.Policy{Encrypt: req.Encrypt, Persist: req.Persist, SignMsgs: req.Encrypt}
	roomID, err := p.client.CreateRoom(req.Subject, policy)
	if err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	info := roomInfo{subject: req.Subject, encrypt: req.Encrypt}
	if err := p.subscribeRoom(roomID, info); err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"room_id": roomID, "subject": req.Subject, "encrypt": req.Encrypt, "persist": req.Persist,
	})
}

func (h *Hub) handleJoin(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Peer   string `json:"peer"`
		RoomID string `json:"room_id"`
	}
	if err := decodeBody(r, &req); err != nil || req.Peer == "" || req.RoomID == "" {
		writeErr(w, http.StatusBadRequest, "peer and room_id required")
		return
	}
	p, ok := h.lookup(req.Peer)
	if !ok {
		writeErr(w, http.StatusBadRequest, "unknown peer "+req.Peer)
		return
	}
	if err := p.client.Join(req.RoomID); err != nil {
		writeErr(w, http.StatusBadRequest, "join failed: "+err.Error())
		return
	}
	info, err := fetchRoomInfo(req.RoomID)
	if err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	if err := p.subscribeRoom(req.RoomID, info); err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"subject": info.subject, "encrypt": info.encrypt})
}

func (h *Hub) handleInvite(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Peer   string `json:"peer"`
		RoomID string `json:"room_id"`
		Target string `json:"target"`
	}
	if err := decodeBody(r, &req); err != nil || req.Peer == "" || req.RoomID == "" || req.Target == "" {
		writeErr(w, http.StatusBadRequest, "peer, room_id and target required")
		return
	}
	p, ok := h.lookup(req.Peer)
	if !ok {
		writeErr(w, http.StatusBadRequest, "unknown peer "+req.Peer)
		return
	}
	target, ok := h.lookup(req.Target)
	if !ok {
		writeErr(w, http.StatusBadRequest, "target peer "+req.Target+" does not exist; connect it first")
		return
	}
	if err := p.client.Invite(req.RoomID, target.endpoint); err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "invited", "target": req.Target})
}

func (h *Hub) handlePublish(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Peer   string `json:"peer"`
		RoomID string `json:"room_id"`
		Text   string `json:"text"`
	}
	if err := decodeBody(r, &req); err != nil || req.Peer == "" || req.RoomID == "" {
		writeErr(w, http.StatusBadRequest, "peer and room_id required")
		return
	}
	p, ok := h.lookup(req.Peer)
	if !ok {
		writeErr(w, http.StatusBadRequest, "unknown peer "+req.Peer)
		return
	}
	if err := p.client.Publish(req.RoomID, []byte(req.Text)); err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "published"})
}

func (h *Hub) handleKick(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Peer   string `json:"peer"`
		RoomID string `json:"room_id"`
		Target string `json:"target"`
	}
	if err := decodeBody(r, &req); err != nil || req.Peer == "" || req.RoomID == "" || req.Target == "" {
		writeErr(w, http.StatusBadRequest, "peer, room_id and target required")
		return
	}
	p, ok := h.lookup(req.Peer)
	if !ok {
		writeErr(w, http.StatusBadRequest, "unknown peer "+req.Peer)
		return
	}
	target, ok := h.lookup(req.Target)
	if !ok {
		writeErr(w, http.StatusBadRequest, "target peer "+req.Target+" does not exist")
		return
	}
	if err := p.client.Kick(req.RoomID, target.endpoint.ID); err != nil {
		writeErr(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "kicked", "target": req.Target})
}

// handleStream is the SSE endpoint. The browser opens one EventSource per peer;
// each received Event is emitted as a `data: <json>\n\n` block. The listener is
// cleaned up when the HTTP request context is cancelled (tab closed / reload).
func (h *Hub) handleStream(w http.ResponseWriter, r *http.Request) {
	name := r.URL.Query().Get("peer")
	if name == "" {
		writeErr(w, http.StatusBadRequest, "peer query param required")
		return
	}
	p, ok := h.lookup(name)
	if !ok {
		writeErr(w, http.StatusBadRequest, "unknown peer "+name)
		return
	}
	flusher, ok := w.(http.Flusher)
	if !ok {
		writeErr(w, http.StatusInternalServerError, "streaming unsupported")
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")

	ch := make(chan Event, 64)
	p.addListener(ch)
	defer p.removeListener(ch)

	// Initial comment so the browser marks the stream open immediately.
	fmt.Fprintf(w, ": connected to %s\n\n", name)
	flusher.Flush()

	ctx := r.Context()
	ping := time.NewTicker(20 * time.Second)
	defer ping.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ping.C:
			fmt.Fprintf(w, ": ping\n\n")
			flusher.Flush()
		case ev := <-ch:
			b, err := json.Marshal(ev)
			if err != nil {
				continue
			}
			fmt.Fprintf(w, "data: %s\n\n", b)
			flusher.Flush()
		}
	}
}

// ---------------------------------------------------------------------------
// main: bring up NATS, control plane, and the web server; tear them all down
// cleanly on signal.
// ---------------------------------------------------------------------------

func main() {
	log.SetFlags(log.LstdFlags | log.Lmsgprefix)
	log.SetPrefix("[playground] ")

	if err := os.MkdirAll(localFiles, 0o755); err != nil {
		log.Fatalf("mkdir %s: %v", localFiles, err)
	}

	// 1. Data plane: embedded NATS + JetStream on the fixed internal port.
	ns, err := embeddednats.Start(filepath.Join(localFiles, "js"), natsPort)
	if err != nil {
		log.Fatalf("start embedded nats: %v", err)
	}
	log.Printf("embedded NATS (JetStream) ready: %s", embeddednats.ClientURL(ns))

	// 2. Control plane: membership store + blob store + internal HTTP server.
	store, err := membership.Open(filepath.Join(localFiles, "play.db"))
	if err != nil {
		ns.Shutdown()
		log.Fatalf("open membership store: %v", err)
	}
	blobs, err := blobstore.New(filepath.Join(localFiles, "blobs"))
	if err != nil {
		store.Close()
		ns.Shutdown()
		log.Fatalf("open blob store: %v", err)
	}
	ctrlSrv := &http.Server{Addr: ctrlAddr, Handler: membership.NewServer(store, blobs)}
	go func() {
		if err := ctrlSrv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			log.Fatalf("control plane: %v", err)
		}
	}()
	if err := waitHealthy(ctrlURL+"/healthz", 5*time.Second); err != nil {
		log.Fatalf("control plane not healthy: %v", err)
	}
	log.Printf("control plane ready: %s", ctrlURL)

	// 3. Web UI on :7700.
	hub := newHub()
	mux := http.NewServeMux()
	mux.HandleFunc("/", hub.handleIndex)
	mux.HandleFunc("POST /api/peer", hub.handlePeer)
	mux.HandleFunc("GET /api/peers", hub.handlePeers)
	mux.HandleFunc("POST /api/room", hub.handleRoom)
	mux.HandleFunc("POST /api/join", hub.handleJoin)
	mux.HandleFunc("POST /api/invite", hub.handleInvite)
	mux.HandleFunc("POST /api/publish", hub.handlePublish)
	mux.HandleFunc("POST /api/kick", hub.handleKick)
	mux.HandleFunc("GET /api/stream", hub.handleStream)
	webSrv := &http.Server{Addr: webAddr, Handler: mux}
	go func() {
		if err := webSrv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			log.Fatalf("web server: %v", err)
		}
	}()
	log.Printf("web UI ready: http://%s", webAddr)
	log.Printf("open http://localhost:7700 in two browser tabs to try the bus")

	// 4. Graceful shutdown.
	stop := make(chan os.Signal, 1)
	signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
	<-stop
	log.Printf("shutting down...")

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	_ = webSrv.Shutdown(ctx)
	hub.closeAll()
	_ = ctrlSrv.Shutdown(ctx)
	store.Close()
	ns.Shutdown()
	ns.WaitForShutdown()
	log.Printf("bye")
}

// waitHealthy polls url until it returns a 2xx/3xx or the deadline elapses.
func waitHealthy(url string, timeout time.Duration) error {
	deadline := time.Now().Add(timeout)
	c := &http.Client{Timeout: 500 * time.Millisecond}
	for time.Now().Before(deadline) {
		resp, err := c.Get(url)
		if err == nil {
			resp.Body.Close()
			if resp.StatusCode < 400 {
				return nil
			}
		}
		time.Sleep(100 * time.Millisecond)
	}
	return fmt.Errorf("timeout waiting for %s", url)
}