package server

import (
	"errors"
	"net/http"
	"sort"
	"strings"
	"time"

	"cc.tiredsysadmin.keeporg/internal/secret"
	"cc.tiredsysadmin.keeporg/internal/store"
)

var errForbidden = errors.New("forbidden")

// Every administrative change in this file is a function of the state and the
// caller; the JSON handlers below and the HTML forms in webadmin.go are thin
// wrappers over them. The API and the web interface have to agree about who
// may do what, and the only durable way to make them agree is for both to
// call the same function.

// denyAuth answers a request that failed to re-prove its credentials. The
// cases stay distinct so a client knows to prompt for the factor it is
// missing rather than reporting a flat refusal.
func denyAuth(w http.ResponseWriter, err error) {
	if writeThrottled(w, err) {
		return
	}
	switch {
	case errors.Is(err, errNoDatabase):
		fail(w, http.StatusNotFound, "not_found", err.Error())
	case errors.Is(err, errTOTPRequired):
		fail(w, http.StatusUnauthorized, "totp_required", "your one-time code is required for this")
	case errors.Is(err, errReauth):
		fail(w, http.StatusUnauthorized, "bad_credentials", "your own account password is required for this")
	case errors.Is(err, errBadCredentials):
		fail(w, http.StatusUnauthorized, "bad_credentials",
			"your own account password or one-time code is wrong")
	default:
		deny(w, err)
	}
}

// deny maps a domain error onto a response.
func deny(w http.ResponseWriter, err error) {
	switch {
	case err == nil:
		return
	case errors.Is(err, errNoDatabase):
		fail(w, http.StatusNotFound, "not_found", err.Error())
	case errors.Is(err, errForbidden):
		fail(w, http.StatusForbidden, "forbidden", "you do not administer that object")
	default:
		fail(w, http.StatusBadRequest, "bad_request", err.Error())
	}
}

// ---- visibility ----

// resolveUser finds a user by id or by username, trying each reference in
// turn, so a caller may pass whichever of the two it has.
func resolveUser(st *store.State, refs ...string) *store.User {
	for _, ref := range refs {
		if ref == "" {
			continue
		}
		if u := st.Users[ref]; u != nil {
			return u
		}
		if u := st.UserByName(ref); u != nil {
			return u
		}
	}
	return nil
}

// visibleGroups is the set of groups the user may know about: the ones they
// administer, the ones whose grants reach them, and everything below a group
// they administer. A server administrator sees the whole tree.
func visibleGroups(st *store.State, u *store.User) map[string]bool {
	out := map[string]bool{}
	reach := st.EffectiveGroups(u.ID)
	for id := range st.Groups {
		if u.ServerAdmin || reach[id] || st.IsGroupAdmin(u.ID, id) {
			out[id] = true
			continue
		}
		for _, anc := range st.Ancestors(id) {
			if st.IsGroupAdmin(u.ID, anc) {
				out[id] = true
				break
			}
		}
	}
	return out
}

// sharesAdministeredGroup reports whether admin administers any group the
// target belongs to, which is what makes the target visible to them.
func sharesAdministeredGroup(st *store.State, adminID, targetID string) bool {
	for _, m := range st.Memberships {
		if m.UserID == targetID && st.IsGroupAdmin(adminID, m.GroupID) {
			return true
		}
	}
	return false
}

// visibleUsers lists the accounts the caller may see, by username.
func visibleUsers(st *store.State, u *store.User) []*store.User {
	out := []*store.User{}
	for id, target := range st.Users {
		if u.ServerAdmin || id == u.ID || sharesAdministeredGroup(st, u.ID, id) {
			out = append(out, target)
		}
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Username < out[j].Username })
	return out
}

// ---- groups and membership ----

func createGroup(st *store.State, u *store.User, name, parentID string) (*store.Group, error) {
	name = strings.TrimSpace(name)
	if name == "" {
		return nil, errors.New("name is required")
	}
	if parentID == "" {
		// A group with no parent is a new root, which reorganizes the whole
		// server, so only a server administrator may make one.
		if !u.ServerAdmin {
			return nil, errors.New("pick a parent group")
		}
	} else {
		if st.Groups[parentID] == nil {
			return nil, errors.New("unknown parent group")
		}
		if !st.IsGroupAdmin(u.ID, parentID) {
			return nil, errForbidden
		}
	}
	g := &store.Group{ID: secret.ID(), Name: name, ParentID: parentID, CreatedAt: time.Now()}
	st.Groups[g.ID] = g
	return g, nil
}

func deleteGroup(st *store.State, u *store.User, id string) error {
	if st.Groups[id] == nil {
		return errors.New("no such group")
	}
	if !st.IsGroupAdmin(u.ID, id) {
		return errForbidden
	}
	if len(st.Descendants(id)) > 1 {
		return errors.New("the group still has child groups")
	}
	for _, db := range st.Databases {
		if db.OwnerGroupID == id {
			return errors.New("the group still owns databases")
		}
	}
	for _, m := range st.Memberships {
		if m.GroupID == id {
			return errors.New("the group still has members")
		}
	}
	delete(st.Groups, id)
	st.Grants = filterGrants(st.Grants, func(gr store.Grant) bool { return gr.GroupID != id })
	return nil
}

// setMember adds a user to a group, or changes the role they already have.
func setMember(st *store.State, u *store.User, groupID string, role store.Role, refs ...string) error {
	if st.Groups[groupID] == nil {
		return errors.New("no such group")
	}
	if !st.IsGroupAdmin(u.ID, groupID) {
		return errForbidden
	}
	target := resolveUser(st, refs...)
	if target == nil {
		return errors.New("no such user")
	}
	if role == "" {
		role = store.RoleMember
	}
	if !role.Valid() {
		return errors.New("role must be member or admin")
	}
	for i := range st.Memberships {
		if st.Memberships[i].UserID == target.ID && st.Memberships[i].GroupID == groupID {
			st.Memberships[i].Role = role
			return nil
		}
	}
	st.Memberships = append(st.Memberships,
		store.Membership{UserID: target.ID, GroupID: groupID, Role: role})
	return nil
}

func removeMember(st *store.State, u *store.User, groupID string, refs ...string) error {
	if st.Groups[groupID] == nil {
		return errors.New("no such group")
	}
	if !st.IsGroupAdmin(u.ID, groupID) {
		return errForbidden
	}
	target := resolveUser(st, refs...)
	if target == nil {
		return errors.New("no such user")
	}
	out := st.Memberships[:0]
	for _, m := range st.Memberships {
		if m.UserID == target.ID && m.GroupID == groupID {
			continue
		}
		out = append(out, m)
	}
	st.Memberships = out
	return nil
}

// ---- grants ----

// adminsDatabase checks that u administers a database. One without any
// access cannot tell a database that is not theirs from one that does not
// exist; one who can see it is told it is not theirs to change.
func adminsDatabase(st *store.State, u *store.User, dbID string) error {
	perm := st.DatabasePerm(u.ID, dbID)
	switch {
	case st.Databases[dbID] == nil || perm == store.PermNone:
		return errNoDatabase
	case perm != store.PermAdmin:
		return errForbidden
	}
	return nil
}

func setGrant(st *store.State, u *store.User, groupID, dbID string, perm store.Perm) error {
	if err := adminsDatabase(st, u, dbID); err != nil {
		return err
	}
	if st.Groups[groupID] == nil {
		return errors.New("no such group")
	}
	if !perm.Valid() {
		return errors.New("perm must be read, write or admin")
	}
	for i := range st.Grants {
		if st.Grants[i].GroupID == groupID && st.Grants[i].DatabaseID == dbID {
			st.Grants[i].Perm = perm
			return nil
		}
	}
	st.Grants = append(st.Grants, store.Grant{GroupID: groupID, DatabaseID: dbID, Perm: perm})
	return nil
}

func removeGrant(st *store.State, u *store.User, groupID, dbID string) error {
	if err := adminsDatabase(st, u, dbID); err != nil {
		return err
	}
	st.Grants = filterGrants(st.Grants, func(g store.Grant) bool {
		return g.GroupID != groupID || g.DatabaseID != dbID
	})
	return nil
}

// ---- invites ----

// defaultInviteTTLHours is how long an invite lasts when nobody says.
const defaultInviteTTLHours = 168

func createInvite(st *store.State, u *store.User, groupID string, role store.Role,
	ttlHours, maxUses int) (*store.Invite, error) {
	if role == "" {
		role = store.RoleMember
	}
	if !role.Valid() {
		return nil, errors.New("role must be member or admin")
	}
	if groupID == "" {
		// An invite into no group creates an account with no access at all,
		// which is only ever useful to a server administrator.
		if !u.ServerAdmin {
			return nil, errors.New("pick the group the new account joins")
		}
	} else {
		if st.Groups[groupID] == nil {
			return nil, errors.New("unknown group")
		}
		if !st.IsGroupAdmin(u.ID, groupID) {
			return nil, errForbidden
		}
	}
	if ttlHours <= 0 {
		ttlHours = defaultInviteTTLHours
	}
	if maxUses == 0 {
		maxUses = 1
	}
	inv := &store.Invite{
		Token: secret.Token(), GroupID: groupID, Role: role, CreatedBy: u.ID,
		CreatedAt: time.Now(), MaxUses: maxUses,
		ExpiresAt: time.Now().Add(time.Duration(ttlHours) * time.Hour),
	}
	st.Invites[inv.Token] = inv
	return inv, nil
}

// mayManageInvite decides both who sees an invite and who may revoke it: the
// person who made it, an administrator of the group it leads into, and any
// server administrator.
func mayManageInvite(st *store.State, u *store.User, inv *store.Invite) bool {
	return u.ServerAdmin || inv.CreatedBy == u.ID ||
		(inv.GroupID != "" && st.IsGroupAdmin(u.ID, inv.GroupID))
}

func revokeInvite(st *store.State, u *store.User, token string) error {
	inv := st.Invites[token]
	if inv == nil {
		return errors.New("no such invite")
	}
	if !mayManageInvite(st, u, inv) {
		return errForbidden
	}
	delete(st.Invites, token)
	return nil
}

// ---- accounts ----

// accountAction is a change to an account rather than to its access.
type accountAction string

const (
	accountDisable   accountAction = "disable"
	accountEnable    accountAction = "enable"
	accountPromote   accountAction = "promote"
	accountDemote    accountAction = "demote"
	accountClearTOTP accountAction = "clear-totp"
	accountSignOut   accountAction = "sign-out"
	accountDelete    accountAction = "delete"
)

// adminAccount applies an account change. Only a server administrator may:
// a group administrator decides who reaches which vault, which is a matter
// of access, while disabling an account, clearing somebody's second factor
// or deleting them outright reaches beyond the group they happen to share.
//
// The caller's own account is protected from the three changes that would
// lock them out, because a server with no reachable administrator can only
// be repaired from a shell on the host.
func adminAccount(st *store.State, u *store.User, ref string, act accountAction) (*store.User, error) {
	if !u.ServerAdmin {
		return nil, errForbidden
	}
	target := resolveUser(st, ref)
	if target == nil {
		return nil, errors.New("no such user")
	}
	if target.ID == u.ID {
		switch act {
		case accountDisable, accountDemote, accountDelete:
			return nil, errors.New("that would lock you out, so it is refused on your own account")
		}
	}
	switch act {
	case accountDisable:
		target.Disabled = true
		revokeSessions(st, target.ID)
	case accountEnable:
		target.Disabled = false
	case accountPromote:
		target.ServerAdmin = true
	case accountDemote:
		target.ServerAdmin = false
	case accountClearTOTP:
		target.TOTPSecret, target.TOTPConfirmed = "", false
	case accountSignOut:
		// For a lost phone or laptop: every device must sign in again,
		// and the account stays usable.
		revokeSessions(st, target.ID)
	case accountDelete:
		delete(st.Users, target.ID)
		revokeSessions(st, target.ID)
		out := st.Memberships[:0]
		for _, m := range st.Memberships {
			if m.UserID != target.ID {
				out = append(out, m)
			}
		}
		st.Memberships = out
	default:
		return nil, errors.New("unknown action")
	}
	return target, nil
}

// revokeSessions drops every session a user holds, on any device.
func revokeSessions(st *store.State, userID string) {
	for token, sess := range st.Sessions {
		if sess.UserID == userID {
			delete(st.Sessions, token)
		}
	}
}

// ---- databases ----

func (s *Server) handleCreateDatabase(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		Name          string         `json:"name"`
		OwnerGroupID  string         `json:"owner_group_id"`
		MergeStrategy store.Strategy `json:"merge_strategy"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out dbView
	err := s.st.Update(func(st *store.State) error {
		if strings.TrimSpace(req.Name) == "" {
			return errors.New("name is required")
		}
		if st.Groups[req.OwnerGroupID] == nil {
			return errors.New("unknown owner group")
		}
		if !st.IsGroupAdmin(u.ID, req.OwnerGroupID) {
			return errForbidden
		}
		strategy := req.MergeStrategy
		if strategy == "" {
			strategy = store.StrategyServerWins
		}
		if !strategy.Valid() {
			return errors.New("unknown merge strategy")
		}
		db := &store.Database{ID: secret.ID(), Name: strings.TrimSpace(req.Name),
			OwnerGroupID: req.OwnerGroupID, MergeStrategy: strategy, UpdatedAt: time.Now()}
		st.Databases[db.ID] = db
		out = toView(db, store.PermAdmin)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.notifyList(out.ID)
	writeJSON(w, http.StatusCreated, out)
}

func (s *Server) handlePatchDatabase(w http.ResponseWriter, r *http.Request, u *store.User) {
	id := r.PathValue("id")
	var req struct {
		Name          *string         `json:"name"`
		MergeStrategy *store.Strategy `json:"merge_strategy"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out dbView
	err := s.st.Update(func(st *store.State) error {
		if err := adminsDatabase(st, u, id); err != nil {
			return err
		}
		db := st.Databases[id]
		if req.Name != nil {
			if strings.TrimSpace(*req.Name) == "" {
				return errors.New("name may not be empty")
			}
			db.Name = strings.TrimSpace(*req.Name)
		}
		if req.MergeStrategy != nil {
			if !req.MergeStrategy.Valid() {
				return errors.New("unknown merge strategy")
			}
			if req.MergeStrategy.NeedsKey() && db.WrappedKey == "" {
				return errors.New("merging needs the vault password: store it with " +
					"`keeporg db -id <id> -store-password` first")
			}
			db.MergeStrategy = *req.MergeStrategy
		}
		out = toView(db, store.PermAdmin)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.notifyList(id)
	writeJSON(w, http.StatusOK, out)
}

// errConfirmName is the answer when an account with no password of its own
// did not type the name of the thing it is about to destroy.
var errConfirmName = errors.New("type the name exactly to confirm")

// errNoDatabase is a database that does not exist or that the caller does
// not administer; the two are not told apart, so neither answer says that a
// database exists.
var errNoDatabase = errors.New("no such database")

// deleteDatabase removes a database, its grants and every stored version of
// the file. Clients keep whatever they already have on disk: the server can
// stop tracking a vault, but it has no business reaching into somebody's
// home directory.
//
// It re-proves who the caller is first. Holding a session is enough to read
// and write a vault; it is not enough to destroy every version of one,
// because a session is what an unlocked laptop leaves lying around. The
// password is checked like a sign-in — outside the store's lock and against
// the attempt limits — and only for a caller who administers the database,
// so it is not a password oracle for anyone else.
//
// An account that signs in only through an identity provider has no password
// to type. Refusing those accounts would mean a deployment where nobody can
// delete anything, so they confirm by typing the exact name instead. That is
// a weaker gate and it is deliberately the fallback, not the rule.
func (s *Server) deleteDatabase(r *http.Request, u *store.User, id, password, totpCode, typed string) (string, error) {
	var (
		name        string
		hasPassword bool
	)
	s.st.Read(func(st *store.State) {
		if db := st.Databases[id]; db != nil && st.DatabasePerm(u.ID, id) == store.PermAdmin {
			name = db.Name
		}
		if cur := st.Users[u.ID]; cur != nil {
			hasPassword = cur.PassHash != ""
		}
	})
	if name == "" {
		return "", errNoDatabase
	}
	var watchers []string
	remove := func(st *store.State, _ *store.User) error {
		db := st.Databases[id]
		if db == nil || st.DatabasePerm(u.ID, id) != store.PermAdmin {
			return errNoDatabase
		}
		name = db.Name
		// Taken before the delete: the people to tell are the ones who are
		// about to stop having access.
		watchers = st.Watchers(id)
		delete(st.Databases, id)
		st.Grants = filterGrants(st.Grants, func(g store.Grant) bool { return g.DatabaseID != id })
		return nil
	}
	var err error
	if !hasPassword {
		if strings.TrimSpace(typed) != name {
			return "", errConfirmName
		}
		err = s.st.Update(func(st *store.State) error { return remove(st, u) })
	} else {
		err = s.reconfirm(r, u, password, totpCode, remove)
	}
	if err != nil {
		return "", err
	}
	if ferr := s.blobs.Forget(id); ferr != nil {
		s.log.Printf("delete blobs for %s: %v", id, ferr)
	}
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: id})
	s.log.Printf("%s deleted database %q (%s) and every stored version", u.Username, name, id)
	return name, nil
}

func (s *Server) handleDeleteDatabase(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		Password string `json:"password"`
		TOTP     string `json:"totp"`
		Confirm  string `json:"confirm_name"`
	}
	if r.ContentLength > 0 && !readJSON(w, r, &req) {
		return
	}
	if _, err := s.deleteDatabase(r, u, r.PathValue("id"), req.Password, req.TOTP, req.Confirm); err != nil {
		denyAuth(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

// ---- groups and membership: API ----

type groupView struct {
	ID       string `json:"id"`
	Name     string `json:"name"`
	ParentID string `json:"parent_id,omitempty"`
	Admin    bool   `json:"admin"`
	Members  int    `json:"members"`
}

func (s *Server) handleListGroups(w http.ResponseWriter, r *http.Request, u *store.User) {
	out := []groupView{}
	s.st.Read(func(st *store.State) {
		counts := map[string]int{}
		for _, m := range st.Memberships {
			counts[m.GroupID]++
		}
		for id := range visibleGroups(st, u) {
			g := st.Groups[id]
			out = append(out, groupView{ID: id, Name: g.Name, ParentID: g.ParentID,
				Admin: st.IsGroupAdmin(u.ID, id), Members: counts[id]})
		}
	})
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	writeJSON(w, http.StatusOK, map[string]any{"groups": out})
}

func (s *Server) handleCreateGroup(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		Name     string `json:"name"`
		ParentID string `json:"parent_id"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out groupView
	err := s.st.Update(func(st *store.State) error {
		g, err := createGroup(st, u, req.Name, req.ParentID)
		if err != nil {
			return err
		}
		out = groupView{ID: g.ID, Name: g.Name, ParentID: g.ParentID, Admin: true}
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, out)
}

func (s *Server) handleDeleteGroup(w http.ResponseWriter, r *http.Request, u *store.User) {
	id := r.PathValue("id")
	if err := s.st.Update(func(st *store.State) error {
		return deleteGroup(st, u, id)
	}); err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

func (s *Server) handleSetMember(w http.ResponseWriter, r *http.Request, u *store.User) {
	groupID := r.PathValue("id")
	var req struct {
		Username string     `json:"username"`
		UserID   string     `json:"user_id"`
		Role     store.Role `json:"role"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	if err := s.st.Update(func(st *store.State) error {
		return setMember(st, u, groupID, req.Role, req.UserID, req.Username)
	}); err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) handleRemoveMember(w http.ResponseWriter, r *http.Request, u *store.User) {
	groupID, userRef := r.PathValue("id"), r.PathValue("user")
	if err := s.st.Update(func(st *store.State) error {
		return removeMember(st, u, groupID, userRef)
	}); err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "removed"})
}

// ---- grants: API ----

func (s *Server) handleSetGrant(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		GroupID    string     `json:"group_id"`
		DatabaseID string     `json:"database_id"`
		Perm       store.Perm `json:"perm"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var watchers []string
	err := s.st.Update(func(st *store.State) error {
		if err := setGrant(st, u, req.GroupID, req.DatabaseID, req.Perm); err != nil {
			return err
		}
		watchers = st.Watchers(req.DatabaseID)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: req.DatabaseID})
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) handleDeleteGrant(w http.ResponseWriter, r *http.Request, u *store.User) {
	groupID := r.URL.Query().Get("group_id")
	dbID := r.URL.Query().Get("database_id")
	var watchers []string
	err := s.st.Update(func(st *store.State) error {
		// The watcher list is taken before the grant goes, because the people
		// losing access are exactly the ones who must be told.
		watchers = st.Watchers(dbID)
		return removeGrant(st, u, groupID, dbID)
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: dbID})
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

// ---- invites: API ----

func (s *Server) handleCreateInvite(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		GroupID  string     `json:"group_id"`
		Role     store.Role `json:"role"`
		TTLHours int        `json:"ttl_hours"`
		MaxUses  int        `json:"max_uses"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var inv *store.Invite
	err := s.st.Update(func(st *store.State) error {
		var err error
		inv, err = createInvite(st, u, req.GroupID, req.Role, req.TTLHours, req.MaxUses)
		return err
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, map[string]any{
		"token":      inv.Token,
		"url":        s.inviteURL(inv.Token),
		"expires_at": inv.ExpiresAt,
		"max_uses":   inv.MaxUses,
		"group_id":   inv.GroupID,
		"role":       inv.Role,
	})
}

func (s *Server) handleListInvites(w http.ResponseWriter, r *http.Request, u *store.User) {
	type inviteView struct {
		Token     string     `json:"token"`
		URL       string     `json:"url"`
		GroupID   string     `json:"group_id,omitempty"`
		Role      store.Role `json:"role"`
		Uses      int        `json:"uses"`
		MaxUses   int        `json:"max_uses"`
		ExpiresAt time.Time  `json:"expires_at"`
	}
	out := []inviteView{}
	s.st.Read(func(st *store.State) {
		for _, inv := range st.Invites {
			if !mayManageInvite(st, u, inv) {
				continue
			}
			out = append(out, inviteView{Token: inv.Token, URL: s.inviteURL(inv.Token),
				GroupID: inv.GroupID, Role: inv.Role, Uses: inv.Uses, MaxUses: inv.MaxUses,
				ExpiresAt: inv.ExpiresAt})
		}
	})
	sort.Slice(out, func(i, j int) bool { return out[i].ExpiresAt.Before(out[j].ExpiresAt) })
	writeJSON(w, http.StatusOK, map[string]any{"invites": out})
}

func (s *Server) handleRevokeInvite(w http.ResponseWriter, r *http.Request, u *store.User) {
	if err := s.st.Update(func(st *store.State) error {
		return revokeInvite(st, u, r.PathValue("token"))
	}); err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "revoked"})
}

// inviteURL is the link an invited person follows.
func (s *Server) inviteURL(token string) string {
	return s.cfg.ExternalURL + "/invite/" + token
}

// ---- users: API ----

func (s *Server) handleListUsers(w http.ResponseWriter, r *http.Request, u *store.User) {
	out := []userView{}
	s.st.Read(func(st *store.State) {
		for _, target := range visibleUsers(st, u) {
			v := view(target)
			if !u.ServerAdmin && target.ID != u.ID {
				v.Email, v.TOTPEnabled, v.ServerAdmin = "", false, false
			}
			out = append(out, v)
		}
	})
	writeJSON(w, http.StatusOK, map[string]any{"users": out})
}

func (s *Server) handlePatchUser(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		Action accountAction `json:"action"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out userView
	err := s.st.Update(func(st *store.State) error {
		target, err := adminAccount(st, u, r.PathValue("id"), req.Action)
		if err != nil {
			return err
		}
		out = view(target)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, out)
}

// notifyList tells everyone with access that the database list changed.
func (s *Server) notifyList(dbID string) {
	var watchers []string
	s.st.Read(func(st *store.State) { watchers = st.Watchers(dbID) })
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: dbID})
}

func filterGrants(in []store.Grant, keep func(store.Grant) bool) []store.Grant {
	out := in[:0]
	for _, g := range in {
		if keep(g) {
			out = append(out, g)
		}
	}
	return out
}