package httpapi

import (
	"context"
	"database/sql"
	"encoding/json"
	"log/slog"
	"net/http"
	"sync"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/httprate"

	"commilitia.net/cdrop/internal/calls"
	"commilitia.net/cdrop/internal/clipboard"
	"commilitia.net/cdrop/internal/config"
	"commilitia.net/cdrop/internal/db"
	"commilitia.net/cdrop/internal/hub"
	"commilitia.net/cdrop/internal/jwtauth"
	"commilitia.net/cdrop/internal/push"
	"commilitia.net/cdrop/internal/relay"
	"commilitia.net/cdrop/internal/transfer"
	"commilitia.net/cdrop/internal/webui"
)

type Server struct {
	cfg       *config.Config
	db        *sql.DB
	queries   *db.Queries
	auth      *jwtauth.Authenticator
	hub       *hub.Hub
	transfers *transfer.Service
	relay     *relay.Manager
	calls     *calls.Provider    // optional; nil → STUN-only fallback
	clipboard *clipboard.Service // optional; nil → 503 on /api/clipboard
	push      *push.Sender       // inert when VAPID keys unset → push endpoints 503
	mux       *chi.Mux

	// sessionKey encrypts browser refresh_tokens at rest (web_sessions); nil when
	// CDROP_SESSION_SECRET is unset (dev), which disables passwordless re-login.
	// siteOrigin is the deployment's scheme://host, used for the CSRF Origin check.
	sessionKey []byte
	siteOrigin string

	// sessionTokenKey signs cdrop's self-signed session access tokens (scan-login;
	// AUTH.md §3.1), derived from SessionSecret in a separate domain from sessionKey.
	// nil when SessionSecret is unset → minting is unavailable (QR stays off).
	sessionTokenKey []byte

	// refreshLocks serialise concurrent refreshes of the same web session (all of
	// a user's browser tabs share one cookie → one refresh_token). Striped so the
	// lock set stays bounded; collisions just serialise unrelated sessions, which
	// is harmless. Prevents a multi-tab race from spending a one-time-use
	// refresh_token twice and logging the user out everywhere.
	refreshLocks [refreshLockStripes]sync.Mutex
}

func New(
	cfg *config.Config,
	dbConn *sql.DB,
	queries *db.Queries,
	auth *jwtauth.Authenticator,
	h *hub.Hub,
	transfers *transfer.Service,
	rm *relay.Manager,
	cp *calls.Provider,
	clip *clipboard.Service,
	pushSender *push.Sender,
) *Server {
	s := &Server{
		cfg:       cfg,
		db:        dbConn,
		queries:   queries,
		auth:      auth,
		hub:       h,
		transfers: transfers,
		relay:     rm,
		calls:     cp,
		clipboard: clip,
		push:      pushSender,
		mux:       chi.NewRouter(),

		sessionKey:      deriveSessionKey(cfg.SessionSecret),
		siteOrigin:      deriveSiteOrigin(cfg.OIDCRedirectURI),
		sessionTokenKey: jwtauth.DeriveSessionTokenKey(cfg.SessionSecret),
	}
	s.routes()
	return s
}

func (s *Server) Handler() http.Handler { return s.mux }

func (s *Server) routes() {
	s.mux.Use(middleware.RequestID)
	s.mux.Use(middleware.RealIP)
	s.mux.Use(middleware.Recoverer)

	s.mux.Get("/healthz", s.handleHealth)

	// Anything not matched below falls through to the embedded frontend bundle.
	// In Docker the binary serves the SPA itself; in local dev the embed FS is
	// empty and this 404s — vite dev on :5173 handles the UI instead.
	s.mux.NotFound(webui.Handler().ServeHTTP)

	s.mux.Route("/api", func(r chi.Router) {
		// Public OIDC PKCE plumbing — no auth required (it bootstraps it).
		r.Get("/auth/config", s.handleAuthConfig)
		// Rate-limit the credential-bearing OAuth endpoints (G4): they proxy to
		// the IdP, so without a cap cdrop is a brute-force / token-pivot relay.
		// Per-IP (RealIP is mounted above); 60/min is ample for real logins and
		// hourly refresh even behind a shared NAT, while choking a scripted flood.
		r.Group(func(r chi.Router) {
			r.Use(httprate.LimitByIP(60, time.Minute))
			r.Post("/auth/exchange", s.handleAuthExchange)
			r.Post("/auth/refresh", s.handleAuthRefresh)
			// Cookie-authenticated (no bearer): the HttpOnly session cookie is the
			// only credential. logout drops the server session; device persists
			// this browser's name into the session for PWA-eviction recovery.
			r.Post("/auth/logout", s.handleAuthLogout)
			r.Post("/auth/device", s.handleAuthDevice)
			// Scan-login: the new device opens a request and long-polls status.
			// Public (no bearer — the device isn't logged in yet); the private
			// poll_secret in the X-Poll-Secret header is the only credential.
			r.Post("/auth/qr/start", s.handleQRStart)
			r.Get("/auth/qr/status", s.handleQRStatus)
		})

		// Protected routes. gzip / compress is intentionally NOT mounted —
		// it would buffer the SSE stream.
		r.Group(func(r chi.Router) {
			r.Use(s.auth.Middleware)

			// Clipboard is the one capability a scoped shortcut token may reach
			// (iOS Shortcut sync) — it must carry the "clipboard" scope. Full
			// login sessions pass requireScope unconditionally.
			r.Group(func(r chi.Router) {
				r.Use(requireScope(shortcutScope))
				r.Get("/clipboard", s.handleClipboardGet)
				r.Put("/clipboard", s.handleClipboardPut)
				// Lightweight version probe — no content; lets pollers (iOS
				// Shortcut) detect change cheaply before fetching the full body.
				r.Get("/clipboard/version", s.handleClipboardVersion)
			})

			// Everything else requires a full login session; scoped shortcut
			// tokens are rejected, so a leaked token's blast radius stays the
			// clipboard and nothing more (including token self-management).
			r.Group(func(r chi.Router) {
				r.Use(rejectScoped)
				r.Get("/me", s.handleMe)
				r.Post("/me/disconnect", s.handleDisconnect)
				r.Get("/hub/events", s.handleEvents)
				r.Post("/hub/signal", s.handleSignal)
				r.Post("/message", s.handleMessage)
				r.Get("/devices", s.handleDevices)
				r.Get("/push/vapid-key", s.handlePushVAPIDKey)
				r.Post("/push/subscribe", s.handlePushSubscribe)
				r.Delete("/push/subscribe", s.handlePushUnsubscribe)
				r.Get("/calls/credentials", s.handleCallsCredentials)

				// Account-management surface: restricted guest (scan-login borrow)
				// sessions are rejected here too — they can transfer files but not
				// remove devices, nor mint / list / revoke long-lived shortcut
				// tokens. Full / OIDC / dev sessions pass (AUTH.md §3.2).
				r.Group(func(r chi.Router) {
					r.Use(requireFullSession)
					r.Delete("/devices/{name}", s.handleDeleteDevice)
					r.Post("/shortcut/issue", s.handleShortcutIssue)
					r.Get("/shortcut", s.handleShortcutList)
					r.Delete("/shortcut/{jti}", s.handleShortcutRevoke)
					// Scan-login approval side: the logged-in approver views and
					// authorises the new device. Guest sessions can't reach here, so a
					// borrowed device can't approve further devices.
					r.Get("/auth/qr/request", s.handleQRRequest)
					r.Post("/auth/qr/approve", s.handleQRApprove)
					r.Post("/auth/qr/deny", s.handleQRDeny)
					// Session management: list logins with their permission level,
					// really revoke one (logout), and the standalone step-up the
					// revoke flow re-uses. All under /api/auth so the session cookie
					// (Path=/api/auth) is available for step-up state.
					r.Post("/auth/stepup", s.handleStepUp)
					r.Get("/auth/sessions", s.handleSessionsList)
					r.Delete("/auth/sessions/{id}", s.handleSessionRevoke)
				})

				r.Route("/transfer", func(r chi.Router) {
					r.Post("/initiate", s.handleTransferInit)
					r.Post("/{id}/accept", s.transitionHandler(transfer.StateAccepted, ""))
					r.Post("/{id}/cancel", s.transitionHandler(transfer.StateCancelled, ""))
					r.Post("/{id}/p2p", s.transitionHandler(transfer.StateP2PActive, transfer.ModeP2P))
					r.Post("/{id}/fallback", s.transitionHandler(transfer.StateRelayActive, transfer.ModeRelay))
					r.Post("/{id}/done", s.transitionHandler(transfer.StateDone, ""))
					r.Post("/{id}/fail", s.transitionHandler(transfer.StateFailed, ""))
				})
				r.Route("/relay/{id}", func(r chi.Router) {
					r.Post("/chunk", s.handleRelayChunk)
					r.Get("/stream", s.handleRelayStream)
				})
			})
		})
	})
}

type healthResp struct {
	Status   string `json:"status"`
	AuthMode string `json:"auth_mode"`
	DBOK     bool   `json:"db_ok"`
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()

	resp := healthResp{Status: "ok", AuthMode: s.cfg.AuthMode, DBOK: true}
	if err := s.db.PingContext(ctx); err != nil {
		resp.Status = "degraded"
		resp.DBOK = false
		slog.Error("healthz db ping failed", "err", err)
	}
	writeJSON(w, http.StatusOK, resp)
}

type meResp struct {
	UserID     string   `json:"user_id"`
	Groups     []string `json:"groups"`
	DeviceName string   `json:"device_name"`
	// Scope is the session's capability level: "guest" (scan-login borrow,
	// capability-limited) or "full" (normal login). The UI hides account-management
	// affordances on guest sessions (AUTH.md §3.2).
	Scope string `json:"scope"`
}

func (s *Server) handleMe(w http.ResponseWriter, r *http.Request) {
	claims, ok := jwtauth.ClaimsFromContext(r.Context())
	if !ok {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "claims missing"})
		return
	}
	device, _ := jwtauth.DeviceNameFromContext(r.Context())
	scope := "full"
	if claims.Guest() {
		scope = "guest"
	}
	writeJSON(w, http.StatusOK, meResp{
		UserID:     claims.UserID,
		Groups:     claims.Groups,
		DeviceName: device,
		Scope:      scope,
	})
}

// handleDisconnect 是用户主动告知"本机要下线"的轻量信号（登出 / 关页前）。
// auth 中间件会先 UPSERT device 把 last_seen 更新，本 handler 再 Kick 关闭
// SSE + 立刻广播 presence，让对端不必等 30s 宽限期就看到本设备离线。
func (s *Server) handleDisconnect(w http.ResponseWriter, r *http.Request) {
	claims, _ := jwtauth.ClaimsFromContext(r.Context())
	deviceName, _ := jwtauth.DeviceNameFromContext(r.Context())
	if deviceName == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing device"})
		return
	}
	s.hub.Kick(claims.UserID, deviceName)
	s.hub.PublishPresence(r.Context(), claims.UserID)
	w.WriteHeader(http.StatusNoContent)
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}