// Package gateway implements the Cyrene v2 HTTP gateway: the only socket the
// single binary opens. It serves the versioned REST API (/api/v1), the realtime
// WebSocket hub (/ws/chat) and the RBAC-protected admin API (/api/v1/admin/*)
// all on one port (:8080).
//
// It is deliberately lean. All backend capability flows through injected
// dependencies (construction-time dependency injection) and the in-process bus,
// never through cross-process IPC, so the package never opens a listener of its
// own beyond the gateway port.
//
// Client contract (DevDocs/02-development-constraints.md §九, §十一):
//   - REST responses are {data} on success and {error:{code,message}} on error.
//   - Authentication is JWT bearer (internal/auth); authorization is the
//     owner>admin>viewer RBAC hierarchy (internal/auth).
//   - Admin writes are audited (who/what/when/result).
//   - Realtime events follow DevDocs/design/07 §3 (WS protocol).
package gateway

import (
	"context"
	"fmt"
	"io"
	"io/fs"
	"log/slog"
	"net"
	"net/http"
	"strconv"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/auth"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/bus"
	capreg "git.yeij.top/AskaEth/Cyrene_v2/internal/capability/registry"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/session"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/iot"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/loop"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
)

// source is the log provenance tag for every record this package emits.
const source = "gateway"

// Authenticator abstracts the credential + RBAC service. *auth.JWTService is the
// production implementation; it is an interface so tests substitute a mock.
type Authenticator interface {
	// Sign issues a token for sub with the given role and lifetime.
	Sign(sub string, role auth.Role, ttl time.Duration) (string, error)
	// Verify validates a token and returns its claims.
	Verify(token string) (*auth.Claims, error)
	// Authorize returns an HTTP middleware enforcing at least one required role.
	Authorize(required ...auth.Role) func(http.Handler) http.Handler
}

// CapabilityStore abstracts the global capability registry used to enumerate
// plugins and channels in the admin API. *capability.Registry is the production
// implementation.
type CapabilityStore interface {
	// List returns every capability whose Kind matches, or all when kind is
	// empty.
	List(kind capreg.Kind) []capreg.Capability
	// SetPolicy replaces the reachability markers for the named capability.
	SetPolicy(name string, p capreg.ToolPolicy) error
}

// Chatter runs a single agent turn. *loop.Loop is the production implementation.
type Chatter interface {
	// Run drives one turn for sessionID and returns the final answer.
	Run(ctx context.Context, sessionID string, messages []model.Message) (*loop.Result, error)
}

// SessionStore lists known channel sessions. The concrete session manager does
// not yet expose a list method, so production wiring may leave Sessions nil and
// the handlers return [].
type SessionStore interface {
	List(ctx context.Context) ([]session.Session, error)
}

// PersonaStore lists persona summaries. The concrete persona registry does not
// yet expose a list method, so production wiring may leave Personas nil.
type PersonaStore interface {
	List() []PersonaSummary
}

// MemoryStore lists memory entries. The concrete memory store does not yet
// expose a list method, so production wiring may leave Memories nil.
type MemoryStore interface {
	List(ctx context.Context) ([]MemorySummary, error)
}

// IoTStore lists IoT devices. *iot.Manager is the production implementation.
type IoTStore interface {
	List(ctx context.Context) ([]iot.Device, error)
}

// Deps carries the gateway's injected dependencies. Every field is nil-tolerant
// except Auth, which is required (authentication backs login and every RBAC
// decision). Registry/Loop are satisfied by the concrete *capability.Registry and
// *loop.Loop; Sessions/Personas/Memories remain nil until their managers expose a
// list method, in which case the handlers return [].
type Deps struct {
	// Log is the base logger. Nil uses a discard logger.
	Log *slog.Logger
	// Auth is the JWT/RBAC service. Required.
	Auth Authenticator
	// Bus is the in-process event bus the WS hub subscribes to. Optional.
	Bus bus.Bus
	// Registry enumerates capabilities/plugins/channels. Optional.
	Registry CapabilityStore
	// Loop runs chat turns. Optional (chat returns an error when unset).
	Loop Chatter
	// Session lists channel sessions. Optional.
	Session SessionStore
	// Personas lists personas. Optional.
	Personas PersonaStore
	// Memories lists memory entries. Optional.
	Memories MemoryStore
	// IoT lists IoT devices. Optional.
	IoT IoTStore
	// Frontend is the SPA filesystem served for all non-API, non-WS routes.
	// When nil the gateway serves no static assets (API and WS only). The
	// embedded dist (internal/webui) or an external dist directory is used.
	Frontend fs.FS
}

// Server is the gateway. It owns a ServeMux aggregating REST + WS + admin and a
// WebSocket hub. It is safe for concurrent use once constructed.
type Server struct {
	cfg      *config.Config
	auth     Authenticator
	bus      bus.Bus
	caps     CapabilityStore
	runner   Chatter
	sessions SessionStore
	personas PersonaStore
	memories MemoryStore
	iot      IoTStore
	frontend fs.FS
	log      *slog.Logger
	hub      *hub
}

// New validates cfg and deps and returns a ready Server. Auth is required; the
// WebSocket hub subscribes to deps.Bus immediately so events published before
// ListenAndServe are still relayed to clients.
func New(cfg *config.Config, deps Deps) (*Server, error) {
	if cfg == nil {
		return nil, fmt.Errorf("gateway: nil config")
	}
	if deps.Auth == nil {
		return nil, fmt.Errorf("gateway: auth dependency required")
	}
	s := &Server{
		cfg:      cfg,
		auth:     deps.Auth,
		bus:      deps.Bus,
		caps:     deps.Registry,
		runner:   deps.Loop,
		sessions: deps.Session,
		personas: deps.Personas,
		memories: deps.Memories,
		iot:      deps.IoT,
		frontend: deps.Frontend,
		log:      sourcedLog(deps.Log),
	}
	s.hub = newHub(s)
	s.hub.start()
	return s, nil
}

// Handler returns the fully assembled http.Handler: the ServeMux routing
// REST + WS + admin, wrapped in recovery, CORS and request logging.
func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()

	// Public, no auth.
	mux.HandleFunc("GET /api/v1/health", s.handleHealth)
	mux.HandleFunc("POST /api/v1/auth/login", s.handleLogin)

	// User side, authenticated. Chat is a write (owner/admin); reads accept any
	// authenticated role so a viewer can still list personas/sessions.
	mux.Handle("POST /api/v1/chat", s.auth.Authorize(auth.RoleOwner, auth.RoleAdmin)(http.HandlerFunc(s.handleChat)))
	readAuth := s.auth.Authorize()
	mux.Handle("GET /api/v1/sessions", readAuth(http.HandlerFunc(s.handleListSessions)))
	mux.Handle("GET /api/v1/personas", readAuth(http.HandlerFunc(s.handleListPersonas)))

	// Realtime.
	mux.HandleFunc("/ws/chat", s.handleWS)

	// Admin: reads require owner or admin; the audited policy write requires owner.
	adminAuth := s.auth.Authorize(auth.RoleOwner, auth.RoleAdmin)
	mux.Handle("GET /api/v1/admin/personas", adminAuth(http.HandlerFunc(s.adminListPersonas)))
	mux.Handle("GET /api/v1/admin/sessions", adminAuth(http.HandlerFunc(s.adminListSessions)))
	mux.Handle("GET /api/v1/admin/memories", adminAuth(http.HandlerFunc(s.adminListMemories)))
	mux.Handle("GET /api/v1/admin/plugins", adminAuth(http.HandlerFunc(s.adminListPlugins)))
	mux.Handle("GET /api/v1/admin/channels", adminAuth(http.HandlerFunc(s.adminListChannels)))
	mux.Handle("GET /api/v1/admin/iot", adminAuth(http.HandlerFunc(s.adminListIoT)))
	mux.Handle("POST /api/v1/admin/plugins/policy", s.auth.Authorize(auth.RoleOwner)(http.HandlerFunc(s.adminSetPolicy)))

	var h http.Handler = mux
	if s.frontend != nil {
		h = s.spa(h)
	}
	h = s.recover(h)
	h = s.cors(h)
	h = s.logging(h)
	return h
}

// Start launches the gateway in a goroutine, returning a channel that carries the
// ListenAndServe result. The server runs until ctx is canceled.
func (s *Server) Start(ctx context.Context) (<-chan error, error) {
	errCh := make(chan error, 1)
	go func() { errCh <- s.ListenAndServe(ctx) }()
	return errCh, nil
}

// ListenAndServe binds the configured host:port (default :8080) and blocks until
// ctx is canceled, then gracefully drains in-flight requests.
func (s *Server) ListenAndServe(ctx context.Context) error {
	if ctx == nil {
		ctx = context.Background()
	}
	addr := net.JoinHostPort(s.cfg.Server.Host, strconv.Itoa(s.cfg.Server.Port))
	httpSrv := &http.Server{Addr: addr, Handler: s.Handler()}

	done := make(chan struct{})
	go func() {
		<-ctx.Done()
		s.log.Info("gateway shutting down", "addr", addr)
		s.hub.close()
		shCtx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
		defer cancel()
		_ = httpSrv.Shutdown(shCtx)
		close(done)
	}()

	s.log.Info("gateway listening", "addr", addr)
	err := httpSrv.ListenAndServe()
	if err != nil && err != http.ErrServerClosed {
		return fmt.Errorf("gateway: listen: %w", err)
	}
	<-done
	return nil
}

// Close frees the hub's bus subscription and closes live connections.
func (s *Server) Close() { s.hub.close() }

// sourcedLog returns a logger tagged with source "gateway", substituting a
// discard logger for nil so Server can always log safely.
func sourcedLog(l *slog.Logger) *slog.Logger {
	if l == nil {
		l = slog.New(slog.NewTextHandler(io.Discard, nil))
	}
	return logger.WithSource(l, source)
}