// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2024-2026 Quad4.io

package controlapi

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"quad4/reticulum-go/pkg/common"
	"quad4/reticulum-go/pkg/debug"
	"quad4/reticulum-go/pkg/identity"
	"quad4/reticulum-go/pkg/transport"
)

// Lifecycle coordinates network sleep/wake recovery for the control API.
type Lifecycle interface {
	OnNetworkAvailable() error
	OnNetworkLost() error
	RefreshPaths(dests ...[]byte) error
}

// Server is a localhost JSON control API bound to one Reticulum-Go
// transport. See the package doc comment for the wire protocol.
type Server struct {
	transport *transport.Transport
	lifecycle Lifecycle
	host      string
	port      int
	unixPath  string
	authKey   []byte
	startedAt time.Time

	httpServer   *http.Server
	listener     net.Listener
	unixListener net.Listener

	mu       sync.RWMutex
	sessions map[string]*session

	announceMu   sync.RWMutex
	announceSubs map[*wsClient]struct{}
}

// New builds a control API server bound to t, using cfg.RPCKey as the
// bearer auth token and cfg.ControlAPIHost/Port for the listen address.
// Callers are expected to only call New when cfg.EnableControlAPI is true.
// common.ReticulumConfig.Validate rejects that combination when RPCKey is
// empty.
func New(t *transport.Transport, lifecycle Lifecycle, cfg *common.ReticulumConfig) (*Server, error) {
	if t == nil {
		return nil, errors.New("controlapi: transport is required")
	}
	if cfg == nil || len(cfg.RPCKey) == 0 {
		return nil, errors.New("controlapi: rpc_key must be set")
	}

	host := cfg.ControlAPIHost
	if host == "" {
		host = common.DefaultControlAPIHost
	}
	port := cfg.ControlAPIPort
	if port == 0 {
		port = common.DefaultControlAPIPort
	}

	s := &Server{
		transport:    t,
		lifecycle:    lifecycle,
		host:         host,
		port:         port,
		unixPath:     strings.TrimSpace(cfg.ControlAPISocket),
		authKey:      cfg.RPCKey,
		startedAt:    time.Now(),
		sessions:     make(map[string]*session),
		announceSubs: make(map[*wsClient]struct{}),
	}

	mux := http.NewServeMux()
	s.registerRoutes(mux)
	s.httpServer = &http.Server{
		Handler:           s.authMiddleware(mux),
		ReadHeaderTimeout: 10 * time.Second,
	}

	t.RegisterAnnounceHandler(&announceBridge{server: s})

	return s, nil
}

// Listen binds the configured TCP address. Call before sandbox.Apply on
// platforms where CapEnter or pledge would block a later listen.
func (s *Server) Listen() error {
	if s == nil {
		return errors.New("controlapi: nil server")
	}
	if s.listener != nil {
		return nil
	}
	addr := net.JoinHostPort(s.host, strconv.Itoa(s.port))
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return fmt.Errorf("controlapi: listen on %s: %w", addr, common.WrapListenError(err))
	}
	s.listener = ln
	debug.Log(debug.DebugInfo, "Control API listening", "addr", addr)
	if err := s.listenUnix(); err != nil {
		_ = ln.Close()
		s.listener = nil
		return err
	}
	return nil
}

func (s *Server) listenUnix() error {
	if s.unixPath == "" {
		return nil
	}
	if err := os.Remove(s.unixPath); err != nil && !errors.Is(err, os.ErrNotExist) {
		return fmt.Errorf("controlapi: remove unix socket: %w", err)
	}
	if dir := filepath.Dir(s.unixPath); dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0o700); err != nil {
			return fmt.Errorf("controlapi: unix socket dir: %w", err)
		}
	}
	ln, err := net.Listen("unix", s.unixPath)
	if err != nil {
		return fmt.Errorf("controlapi: listen on unix %s: %w", s.unixPath, common.WrapListenError(err))
	}
	if err := os.Chmod(s.unixPath, 0o600); err != nil {
		_ = ln.Close()
		return fmt.Errorf("controlapi: chmod unix socket: %w", err)
	}
	s.unixListener = ln
	debug.Log(debug.DebugInfo, "Control API unix listening", "path", s.unixPath)
	return nil
}

// Serve serves HTTP on the bound listener. If Listen was not called yet,
// it binds first. Blocks until Close is called. Run it in its own goroutine.
func (s *Server) Serve() error {
	if s.listener == nil {
		if err := s.Listen(); err != nil {
			return err
		}
	}
	if s.unixListener != nil {
		go func() {
			err := s.httpServer.Serve(s.unixListener)
			if err != nil && !errors.Is(err, http.ErrServerClosed) {
				debug.Log(debug.DebugError, "Control API unix serve", "error", err)
			}
		}()
	}
	err := s.httpServer.Serve(s.listener)
	if errors.Is(err, http.ErrServerClosed) {
		return nil
	}
	return err
}

// Close disconnects every session's WebSocket clients and shuts down the
// HTTP listener.
func (s *Server) Close() error {
	s.mu.Lock()
	sessions := make([]*session, 0, len(s.sessions))
	for _, sess := range s.sessions {
		sessions = append(sessions, sess)
	}
	s.sessions = make(map[string]*session)
	s.mu.Unlock()

	for _, sess := range sessions {
		sess.close()
	}

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	return s.httpServer.Shutdown(ctx)
}

func (s *Server) registerRoutes(mux *http.ServeMux) {
	mux.HandleFunc("GET /v1/health", s.handleHealth)
	mux.HandleFunc("GET /v1/status", s.handleStatus)
	mux.HandleFunc("GET /v1/paths", s.handlePaths)
	mux.HandleFunc("POST /v1/sessions", s.handleCreateSession)
	mux.HandleFunc("DELETE /v1/sessions/{id}", s.handleDeleteSession)
	mux.HandleFunc("POST /v1/sessions/{id}/destinations", s.handleRegisterDestination)
	mux.HandleFunc("POST /v1/sessions/{id}/destinations/{hash}/announce", s.handleAnnounce)
	mux.HandleFunc("POST /v1/sessions/{id}/destinations/{hash}/requests", s.handleRegisterRequestHandler)
	mux.HandleFunc("DELETE /v1/sessions/{id}/destinations/{hash}/requests", s.handleDeregisterRequestHandler)
	mux.HandleFunc("POST /v1/sessions/{id}/path/request", s.handlePathRequest)
	mux.HandleFunc("GET /v1/sessions/{id}/events", s.handleEvents)
	mux.HandleFunc("POST /v1/lifecycle/resume", s.handleLifecycleResume)
	mux.HandleFunc("POST /v1/lifecycle/pause", s.handleLifecyclePause)
	mux.HandleFunc("POST /v1/lifecycle/refresh-paths", s.handleLifecycleRefreshPaths)
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, healthResponse{
		Status:          "ok",
		TransportID:     hex.EncodeToString(s.transport.TransportIdentityHash()),
		TransportUptime: time.Since(s.startedAt).Seconds(),
	})
}

func (s *Server) handleStatus(w http.ResponseWriter, r *http.Request) {
	stats := s.transport.GetInterfaceStatsRPC()
	resp := statusResponse{
		TransportID: hex.EncodeToString(stats.TransportID),
		Interfaces:  make([]interfaceStatJSON, 0, len(stats.Interfaces)),
	}
	for _, ifc := range stats.Interfaces {
		resp.Interfaces = append(resp.Interfaces, interfaceStatJSON{
			Name:                  ifc.Name,
			Type:                  ifc.Type,
			Status:                ifc.Status,
			RXBytes:               ifc.RXB,
			TXBytes:               ifc.TXB,
			Bitrate:               ifc.Bitrate,
			Clients:               ifc.Clients,
			BlockedIPs:            ifc.BlockedIPs,
			BlockedIPList:         ifc.BlockedIPList,
			I2PConnectable:        ifc.I2PConnectable,
			I2PB32:                ifc.I2PB32,
			TunnelState:           ifc.TunnelState,
			I2PLastError:          ifc.I2PLastError,
			IFACFail:              ifc.IFACFail,
			HMACFail:              ifc.HMACFail,
			AnnounceSigFail:       ifc.AnnounceSigFail,
			UnpackFail:            ifc.UnpackFail,
			AnnounceDup:           ifc.AnnounceDup,
			PathRespSuppressed:    ifc.PathRespSuppressed,
			PathReqDup:            ifc.PathReqDup,
			PathReqNoCache:        ifc.PathReqNoCache,
			PathRespQueuedSkip:    ifc.PathRespQueuedSkip,
			LinkRelayUnknownIface: ifc.LinkRelayUnknownIface,
			IntegrityFailRate:     ifc.IntegrityFailRate,
			StaleCloses:           ifc.StaleCloses,
			LinkStaleClose:        ifc.LinkStaleClose,
			KeepaliveTimeout:      ifc.KeepaliveTimeout,
		})
	}
	ps := stats.Protect
	resp.Protect.Mode = ps.Mode
	resp.Protect.Phase = ps.Phase
	resp.Protect.Enforcement = ps.Enforcement
	resp.Protect.Fingerprint = ps.Fingerprint
	resp.Protect.SheddingMemory = ps.SheddingMemory
	resp.Protect.TripCounts.PPS = ps.TripCounts.PPS
	resp.Protect.TripCounts.BPS = ps.TripCounts.BPS
	resp.Protect.TripCounts.Handler = ps.TripCounts.Handler
	resp.Protect.TripCounts.Conn = ps.TripCounts.Conn
	resp.Protect.TripCounts.Resource = ps.TripCounts.Resource
	resp.Protect.TripCounts.Memory = ps.TripCounts.Memory
	resp.Protect.TripCounts.Crypto = ps.TripCounts.Crypto
	resp.Protect.TripCounts.Handshake = ps.TripCounts.Handshake
	resp.Protect.TripCounts.CoolDown = ps.TripCounts.CoolDown
	writeJSON(w, http.StatusOK, resp)
}

func (s *Server) handlePaths(w http.ResponseWriter, r *http.Request) {
	entries := s.transport.GetPathTable(nil)
	out := make([]pathTableEntryJSON, 0, len(entries))
	for _, e := range entries {
		out = append(out, pathTableEntryJSON{
			Hash:      hex.EncodeToString(e.Hash),
			Via:       hex.EncodeToString(e.Via),
			Hops:      e.Hops,
			Expires:   e.Expires,
			Interface: e.Interface,
		})
	}
	writeJSON(w, http.StatusOK, out)
}

func (s *Server) handleCreateSession(w http.ResponseWriter, r *http.Request) {
	var req createSessionRequest
	if r.Body != nil {
		if err := decodeJSONBody(w, r, &req); err != nil && !errors.Is(err, io.EOF) {
			if isBodyTooLarge(err) {
				return
			}
			writeError(w, http.StatusBadRequest, "invalid request body")
			return
		}
	}

	ident, err := loadOrCreateIdentity(req.IdentityPath)
	if err != nil {
		writeError(w, http.StatusInternalServerError, fmt.Sprintf("identity: %v", err))
		return
	}

	sessionID, err := randomID()
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to allocate session id")
		return
	}

	sess := newSession(sessionID, ident)
	s.mu.Lock()
	s.sessions[sessionID] = sess
	s.mu.Unlock()

	writeJSON(w, http.StatusCreated, createSessionResponse{
		SessionID:    sessionID,
		IdentityHash: ident.GetHexHash(),
	})
}

// loadOrCreateIdentity loads the identity at path, creates and persists a
// new one there if path is set but does not exist yet, or generates an
// ephemeral in-memory identity when path is empty.
func loadOrCreateIdentity(path string) (*identity.Identity, error) {
	if path == "" {
		return identity.NewIdentity()
	}
	if _, err := os.Stat(path); err == nil {
		return identity.LoadIdentityFile(path, nil)
	}
	ident, err := identity.NewIdentity()
	if err != nil {
		return nil, err
	}
	if err := ident.ToFile(path); err != nil {
		return nil, err
	}
	return ident, nil
}

func (s *Server) handleDeleteSession(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	s.mu.Lock()
	sess, ok := s.sessions[id]
	if ok {
		delete(s.sessions, id)
	}
	s.mu.Unlock()

	if !ok {
		writeError(w, http.StatusNotFound, "session not found")
		return
	}
	sess.close()
	w.WriteHeader(http.StatusNoContent)
}

func (s *Server) handlePathRequest(w http.ResponseWriter, r *http.Request) {
	if _, ok := s.session(r.PathValue("id")); !ok {
		writeError(w, http.StatusNotFound, "session not found")
		return
	}

	var req pathRequestRequest
	if err := decodeJSONBody(w, r, &req); err != nil {
		if isBodyTooLarge(err) {
			return
		}
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	destHash, err := hex.DecodeString(req.DestinationHash)
	if err != nil || len(destHash) != 16 {
		writeError(w, http.StatusBadRequest, "destination_hash must be 16 hex-encoded bytes")
		return
	}

	if err := s.transport.RequestPath(destHash, "", nil, false); err != nil {
		writeError(w, http.StatusInternalServerError, fmt.Sprintf("path request: %v", err))
		return
	}
	w.WriteHeader(http.StatusAccepted)
}

func (s *Server) handleEvents(w http.ResponseWriter, r *http.Request) {
	sess, ok := s.session(r.PathValue("id"))
	if !ok {
		writeError(w, http.StatusNotFound, "session not found")
		return
	}
	if !strings.EqualFold(r.Header.Get("Upgrade"), "websocket") || r.Header.Get("Sec-WebSocket-Key") == "" {
		writeError(w, http.StatusBadRequest, "expected websocket upgrade request")
		return
	}

	pending, err := beginWebSocketUpgrade(w, r)
	if err != nil {
		debug.Log(debug.DebugError, "controlapi: websocket upgrade failed", "error", err)
		return
	}

	// Register and start the writer before flushing 101 so a peer that
	// races ahead and triggers a broadcast cannot miss the event: the
	// session already has a client, and writeLoop is already scheduled
	// (gated until enableWrites so frames cannot precede the 101).
	client := newWSClient(s, sess, pending.Conn())
	if !sess.addClient(client) {
		_ = pending.Conn().close()
		return
	}
	client.startWriter()

	if err := pending.Flush(); err != nil {
		debug.Log(debug.DebugError, "controlapi: websocket handshake flush failed", "error", err)
		client.close()
		return
	}

	client.enableWrites()
	client.run()
}

func (s *Server) session(id string) (*session, bool) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	sess, ok := s.sessions[id]
	return sess, ok
}

func (s *Server) subscribeAnnounces(c *wsClient) {
	s.announceMu.Lock()
	defer s.announceMu.Unlock()
	s.announceSubs[c] = struct{}{}
}

func (s *Server) unsubscribeAnnounces(c *wsClient) {
	s.announceMu.Lock()
	defer s.announceMu.Unlock()
	delete(s.announceSubs, c)
}

func (s *Server) broadcastAnnounce(evt announceEvent) {
	s.announceMu.RLock()
	defer s.announceMu.RUnlock()
	for c := range s.announceSubs {
		if c.matchesAnnounceFilter(evt.DestinationHash) {
			c.send(evt)
		}
	}
}

func randomID() (string, error) {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return hex.EncodeToString(b), nil
}