package api

import (
	"encoding/json"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"time"

	"geniusrun/backend/internal/auth"
	"geniusrun/backend/internal/garmin"
	applog "geniusrun/backend/internal/log"
)

// setupSession is a temporary, not-yet-persisted Garmin authentication
// attempt made during onboarding, before any users/profile row exists --
// keyed by OIDC subject (the only stable identifier available pre-account)
// rather than a user id. Closed (never promoted into Server.userClient) once
// /api/setup/complete actually creates the account -- its Client's
// garmin.Config.TokenStorePath is permanently pinned to the ephemeral
// setup/{hash} directory, so reusing the object after that directory is
// renamed to the permanent {userID} one would respawn against a stale path
// the next time anything closes and restarts its subprocess; a later
// garminFor(ctx, userID) call builds a fresh client with the correct path
// instead. Otherwise evicted lazily (the next setup-endpoint touch for that
// subject checks staleness first) once idle past SessionConfig.SetupTimeout.
type setupSession struct {
	Client          garmin.Client
	Email, Password string
	Status          garmin.AuthStatus
	Message         string
	LastUsed        time.Time
}

// handleSetupGarminLogin authenticates against Garmin using an ephemeral,
// not-yet-persisted session keyed by the OIDC subject -- no users/profile
// row exists yet at this point (see setupSession in server.go).
func (s *Server) handleSetupGarminLogin(w http.ResponseWriter, r *http.Request) {
	claims, ok := auth.ClaimsFromContext(r.Context())
	if !ok {
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}
	if _, found := userFromContext(r.Context()); found {
		writeError(w, http.StatusConflict, "profile already exists for this account")
		return
	}

	var body struct {
		GarminEmail    string `json:"garmin_email"`
		GarminPassword string `json:"garmin_password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if body.GarminEmail == "" || body.GarminPassword == "" {
		writeError(w, http.StatusBadRequest, "garmin_email and garmin_password are required")
		return
	}

	sess := s.replaceSetupSession(claims.Sub, body.GarminEmail, body.GarminPassword)
	res, err := sess.Client.Authenticate(r.Context())
	if err != nil {
		writeError(w, http.StatusBadGateway, err.Error())
		return
	}
	s.recordSetupAuthResult(claims.Sub, res)
	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(res.Status), Message: res.Message})
}

// handleSetupGarminMFA continues an in-progress ephemeral Garmin login
// (started by handleSetupGarminLogin) with an MFA code, on the same
// session/subprocess -- never replaces it.
func (s *Server) handleSetupGarminMFA(w http.ResponseWriter, r *http.Request) {
	claims, ok := auth.ClaimsFromContext(r.Context())
	if !ok {
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}

	var body struct {
		Code string `json:"code"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if body.Code == "" {
		writeError(w, http.StatusBadRequest, "code is required")
		return
	}

	sess, ok := s.setupSessionFor(claims.Sub)
	if !ok {
		writeError(w, http.StatusConflict, "no Garmin connection attempt in progress; connect again")
		return
	}
	res, err := sess.Client.CompleteMFA(r.Context(), body.Code)
	if err != nil {
		writeError(w, http.StatusBadGateway, err.Error())
		return
	}
	s.recordSetupAuthResult(claims.Sub, res)
	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(res.Status), Message: res.Message})
}

// handleSetupComplete is the single atomic commit point: only reachable
// once the ephemeral session for this subject last reported
// garmin.AuthSuccess. Provisions the account, persists the Garmin
// credentials, marks it connected, closes the ephemeral client, and
// renames its token-store directory into the permanent per-user path --
// the next real clientFor(ctx, userID) builds a fresh client from scratch
// against that now-permanent directory, whose subprocess's lazy
// startup-login resumes the just-renamed, still-valid session without
// needing to re-authenticate (a cheap local token-store resume, not a
// fresh Garmin login).
func (s *Server) handleSetupComplete(w http.ResponseWriter, r *http.Request) {
	claims, ok := auth.ClaimsFromContext(r.Context())
	if !ok {
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}
	if _, found := userFromContext(r.Context()); found {
		writeError(w, http.StatusConflict, "profile already exists for this account")
		return
	}

	var body struct {
		DisplayName string `json:"display_name"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if body.DisplayName == "" {
		writeError(w, http.StatusBadRequest, "display_name is required")
		return
	}

	sess, ok := s.setupSessionFor(claims.Sub)
	if !ok || sess.Status != garmin.AuthSuccess {
		writeError(w, http.StatusConflict, "Garmin isn't connected yet -- connect before completing setup")
		return
	}

	userID, err := s.DB.ProvisionUser(r.Context(), claims.Sub, body.DisplayName)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	profile, err := s.DB.GetProfile(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	profile.GarminEmail = sess.Email
	profile.GarminPassword = sess.Password
	if err := s.DB.UpdateProfile(r.Context(), userID, profile); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if err := s.DB.MarkGarminConnected(r.Context(), userID); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}

	// The ephemeral client's own garmin.Config.TokenStorePath was set once,
	// at construction time in replaceSetupSession, to the ephemeral
	// setup/{hash} directory being renamed below -- there's no setter to
	// correct it in place, so promoting this object into s.userGarmin would
	// leave a client whose subprocess respawns (e.g. on the very next
	// UpdateCredentials call from a Profile save) using that now-stale
	// path, recreating a setup/{hash} directory next to the real one.
	// Closing it here and leaving s.userGarmin empty for this user makes
	// the next garminFor(ctx, userID) call build a fresh client against the
	// correct, just-renamed {userID} directory instead -- its subprocess's
	// lazy startup-login resumes that session without a real Garmin
	// re-authentication.
	sess.Client.Close()

	s.mu.Lock()
	delete(s.setupSession, claims.Sub)
	s.userAuthStatus[userID] = sess.Status
	s.userAuthMessage[userID] = sess.Message
	s.mu.Unlock()

	if s.ClientConfig.TokenStorePath != "" {
		oldDir := setupTokenStoreDir(s.ClientConfig.TokenStorePath, claims.Sub)
		newDir := filepath.Join(s.ClientConfig.TokenStorePath, strconv.FormatInt(userID, 10))
		// A stale {userID} directory can survive from a previous account
		// with the same id -- pre-production the DB file is freely deleted
		// and recreated (ids restart at 1) while the token-store root lives
		// on, and os.Rename refuses to replace a non-empty directory. The
		// just-validated setup session must win, so clear the target first.
		if err := os.RemoveAll(newDir); err != nil {
			applog.App().Error("remove stale token store dir", "user_id", userID, "error", err)
		}
		if err := os.Rename(oldDir, newDir); err != nil && !os.IsNotExist(err) {
			applog.App().Error("rename setup token store dir", "user_id", userID, "error", err)
		}
	}

	writeJSON(w, http.StatusOK, map[string]any{"user_id": userID, "display_name": body.DisplayName})
}

// setupSessionFor returns sub's in-progress ephemeral Garmin session, if
// any and not stale. A stale session is closed and evicted first, so the
// caller always either gets a fresh, live session or none.
func (s *Server) setupSessionFor(sub string) (*setupSession, bool) {
	s.mu.Lock()
	defer s.mu.Unlock()
	sess, ok := s.setupSession[sub]
	if !ok {
		return nil, false
	}
	if time.Since(sess.LastUsed) > s.SessionConfig.SetupTimeout {
		sess.Client.Close()
		delete(s.setupSession, sub)
		if s.ClientConfig.TokenStorePath != "" {
			os.RemoveAll(setupTokenStoreDir(s.ClientConfig.TokenStorePath, sub))
		}
		return nil, false
	}
	return sess, true
}

// replaceSetupSession closes and replaces sub's ephemeral Garmin session
// (if any) with a freshly built one for the given credentials -- same
// "close old, spawn new" semantics as garmin.Client.UpdateCredentials.
func (s *Server) replaceSetupSession(sub, email, password string) *setupSession {
	s.mu.Lock()
	old, ok := s.setupSession[sub]
	s.mu.Unlock()
	if ok {
		old.Client.Close()
	}

	cfg := s.ClientConfig
	cfg.GarminEmail = email
	cfg.GarminPassword = password
	if cfg.TokenStorePath != "" {
		cfg.TokenStorePath = setupTokenStoreDir(s.ClientConfig.TokenStorePath, sub)
	}
	sess := &setupSession{Client: s.GarminFactory(cfg), Email: email, Password: password, LastUsed: time.Now()}

	s.mu.Lock()
	s.setupSession[sub] = sess
	s.mu.Unlock()
	return sess
}

// recordSetupAuthResult updates sub's ephemeral session after a login or
// MFA attempt. A no-op if the session is gone (e.g. evicted concurrently).
func (s *Server) recordSetupAuthResult(sub string, res garmin.AuthResult) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if sess, ok := s.setupSession[sub]; ok {
		sess.Status = res.Status
		sess.Message = res.Message
		sess.LastUsed = time.Now()
	}
}

// removeSetupSession closes and drops sub's ephemeral Garmin session, if
// any, and best-effort removes its token-store directory. Used when
// abandoning onboarding (logout). handleSetupComplete closes the client the
// same way but keeps (renames) the directory instead of removing it, since
// that's the real, now-permanent session.
func (s *Server) removeSetupSession(sub string) {
	s.mu.Lock()
	sess, ok := s.setupSession[sub]
	delete(s.setupSession, sub)
	s.mu.Unlock()
	if !ok {
		return
	}
	sess.Client.Close()
	if s.ClientConfig.TokenStorePath != "" {
		os.RemoveAll(setupTokenStoreDir(s.ClientConfig.TokenStorePath, sub))
	}
}