package cabana

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"
	"unicode/utf8"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/phrasebook"
	"gorm.io/gorm"
)

// usersAdmin is the Administrators screen (summercms.cabana.users), the
// WinterCMS Backend\Controllers\Users controller over backend_users. Every
// route needs backend.manage_users. screens gives access to the activating
// app and the compiled registry at request time.
type usersAdmin struct {
	screens *backendScreens
}

var (
	_ pact.AdminController         = usersAdmin{}
	_ pact.AdminPermissioned       = usersAdmin{}
	_ pact.AdminRecordSource       = usersAdmin{}
	_ pact.FormRecordTitle         = usersAdmin{}
	_ FieldRelationProvider        = usersAdmin{}
	_ pact.ListExtendQuery         = usersAdmin{}
	_ pact.FormExtendQuery         = usersAdmin{}
	_ pact.FormVirtualFields       = usersAdmin{}
	_ pact.FormRules               = usersAdmin{}
	_ pact.FilterOptions           = usersAdmin{}
	_ pact.FormBeforeCreate        = usersAdmin{}
	_ pact.FormBeforeUpdate        = usersAdmin{}
	_ pact.FormAfterUpdate         = usersAdmin{}
	_ RelationLockProvider         = usersAdmin{}
	_ PermissionEditorProvider     = usersAdmin{}
	_ PermissionRecordLockProvider = usersAdmin{}
	_ recordDataExtender           = usersAdmin{}
	_ schemaFieldHider             = usersAdmin{}
	_ pact.ListRowStates           = usersAdmin{}
	_ pact.FormBeforeDelete        = usersAdmin{}
	_ pact.FormAfterDelete         = usersAdmin{}
	_ pact.HasAdminRecordActions   = usersAdmin{}
	_ pact.HasAdminBulkActions     = usersAdmin{}
	_ pact.AdminPartialData        = usersAdmin{}
)

func (usersAdmin) ID() string { return AdministratorsControllerID }

func (usersAdmin) ModelName() string { return BackendUserMorphType }

func (usersAdmin) ConfigDir() string { return "controllers/users" }

func (usersAdmin) RequiredPermissions() []string { return []string{PermissionManageUsers} }

func (usersAdmin) NewRecord() any { return &BackendUser{} }

// application is the activating app, or nil.
func (c usersAdmin) application() *backpack.App { return c.screens.application() }

// registry is the compiled registry, or nil before compilation finished.
func (c usersAdmin) registry() *Registry { return c.screens.registry() }

// FormRecordTitle names an administrator "First Last" when either name is
// set, otherwise by the login.
func (usersAdmin) FormRecordTitle(_ context.Context, _ *gorm.DB, record any) (string, error) {
	user, ok := record.(*BackendUser)
	if !ok || user == nil {
		return "", errors.New("cabana: administrators: record is not a backend user")
	}
	if name := strings.TrimSpace(strings.TrimSpace(user.FirstName) + " " + strings.TrimSpace(user.LastName)); name != "" {
		return name, nil
	}
	return user.Login, nil
}

// AdminFieldRelations binds the role picker. role_id is a protected column,
// so the contract opts in to writing it through this one field; the
// submitted id is still checked against the options and the role locks.
func (usersAdmin) AdminFieldRelations() []FieldRelationContract {
	return []FieldRelationContract{{
		Field:              "role",
		Kind:               "belongsTo",
		NewRelated:         func() any { return &BackendUserRole{} },
		ForeignKey:         "role_id",
		LabelColumn:        "name",
		WritableForeignKey: true,
	}}
}

// usersLang prefixes the phrase keys of the Administrators screen.
const usersLang = "backend::lang.user."

// The Administrators form's protected fields.
const (
	usersRoleField        = "role"
	usersPermissionsField = "permissions"
	usersSuperuserField   = "is_superuser"
)

// db is the application pool, or nil without one.
func (c usersAdmin) db() *gorm.DB {
	app := c.application()
	if app == nil {
		return nil
	}
	gdb, ok := app.Lookup[*gorm.DB]()
	if !ok {
		return nil
	}
	return gdb
}

// requestDB is the write transaction on ctx, else the application pool.
func (c usersAdmin) requestDB(ctx context.Context) *gorm.DB {
	if tx, ok := TxFromContext(ctx); ok {
		return tx
	}
	return c.db()
}

// translator is the application's translator, or nil.
func (c usersAdmin) translator() *phrasebook.Translator {
	app := c.application()
	if app == nil {
		return nil
	}
	tr, _ := app.Lookup[*phrasebook.Translator]()
	return tr
}

// asBackendUser asserts a hook's model.
func asBackendUser(model any) (*BackendUser, error) {
	user, ok := model.(*BackendUser)
	if !ok || user == nil {
		return nil, errors.New("cabana: administrators: record is not a backend user")
	}
	return user, nil
}

// ListExtendQuery includes deleted administrators (WinterCMS's
// withTrashed), so they are listed with their row state and can be
// restored, and hides superusers from an administrator who does not act as
// a superuser (D-03): they are never listed, and a bulk selection never
// resolves to one.
func (usersAdmin) ListExtendQuery(ctx context.Context, db *gorm.DB) *gorm.DB {
	return scopeAdministrators(ctx, db)
}

// FormExtendQuery applies the same scope to every record lookup, so a
// deleted administrator opens and a superuser's id is not found (404) for
// anyone else: show, the preview partial, update, delete and record actions.
func (usersAdmin) FormExtendQuery(ctx context.Context, db *gorm.DB) *gorm.DB {
	return scopeAdministrators(ctx, db)
}

func scopeAdministrators(ctx context.Context, db *gorm.DB) *gorm.DB {
	if db == nil {
		return db
	}
	db = db.Unscoped()
	principal, _ := bouncer.User(ctx)
	if actsAsSuperuser(principal) {
		return db
	}
	return db.Where("backend_users.is_superuser = ?", false)
}

// ListRowStates marks a deleted administrator deleted and a deactivated one
// disabled; a row may carry both.
func (usersAdmin) ListRowStates(_ context.Context, _ *gorm.DB, records []any) ([][]pact.RowState, error) {
	out := make([][]pact.RowState, len(records))
	for i, record := range records {
		user, err := asBackendUser(record)
		if err != nil {
			return nil, err
		}
		if user.DeletedAt.Valid {
			out[i] = append(out[i], pact.RowStateDeleted)
		}
		if !user.IsActivated {
			out[i] = append(out[i], pact.RowStateDisabled)
		}
	}
	return out, nil
}

// FormBeforeDelete refuses deleting yourself (D-08), an administrator who
// outranks the editor (D-19) and the last active superuser (D-09). The
// framework calls it for the form's delete and once per row inside the bulk
// delete's transaction, so one refused row rolls the whole selection back.
func (c usersAdmin) FormBeforeDelete(ctx context.Context, model any) error {
	user, err := asBackendUser(model)
	if err != nil {
		return err
	}
	principal, _ := bouncer.User(ctx)
	if principal != nil && principal.ID == user.ID {
		return &ForbiddenError{Message: usersLang + "self_delete"}
	}
	if err := guardOutranked(ctx, c.registry(), principal, user); err != nil {
		return err
	}
	return guardLastSuperuser(ctx, user)
}

// FormAfterDelete ends the deleted administrator's sessions (D-12). The
// delete itself stays the framework's soft delete through deleted_at: a
// backend user is never hard-deleted, so tokens, linked_by references and
// attachments keep valid foreign keys (D-10). Personal API tokens stop
// because the guard refuses a deleted administrator.
func (c usersAdmin) FormAfterDelete(ctx context.Context, model any) error {
	user, err := asBackendUser(model)
	if err != nil {
		return err
	}
	tx, ok := TxFromContext(ctx)
	if !ok {
		return errors.New("cabana: administrators: a delete needs its transaction")
	}
	cutoff := revocationCutoff()
	if err := tx.Session(&gorm.Session{NewDB: true}).WithContext(ctx).Unscoped().
		Model(&BackendUser{}).Where("id = ?", user.ID).
		Update("tokens_valid_after", cutoff).Error; err != nil {
		return err
	}
	fireSubjectChanged(ctx, c.application(), pact.MCPSubjectDeleted, user.ID)
	return nil
}

// usersLifecycle is one lifecycle action of the Administrators screen,
// shared by its record and bulk forms.
type usersLifecycle struct {
	name string
	// applies is the action's Applies for a record; self is true on the
	// editor's own record.
	applies func(user *BackendUser, self bool) bool
	// run checks and writes one administrator through the action's
	// transaction.
	run func(ctx context.Context, c usersAdmin, db *gorm.DB, editor *bouncer.Principal, user *BackendUser) error
}

func (c usersAdmin) lifecycles() []usersLifecycle {
	return []usersLifecycle{
		{
			name: "activate",
			applies: func(user *BackendUser, _ bool) bool {
				return !user.DeletedAt.Valid && !user.IsActivated
			},
			run: func(ctx context.Context, c usersAdmin, db *gorm.DB, editor *bouncer.Principal, user *BackendUser) error {
				if err := guardOutranked(ctx, c.registry(), editor, user); err != nil {
					return err
				}
				now := time.Now().UTC()
				return db.Model(&BackendUser{}).Where("id = ?", user.ID).
					Updates(map[string]any{"is_activated": true, "activated_at": now}).Error
			},
		},
		{
			name: "deactivate",
			// Deactivate is not offered on your own record; the run still
			// refuses it (a bulk selection may hold it).
			applies: func(user *BackendUser, self bool) bool {
				return !user.DeletedAt.Valid && user.IsActivated && !self
			},
			run: func(ctx context.Context, c usersAdmin, db *gorm.DB, editor *bouncer.Principal, user *BackendUser) error {
				if editor != nil && editor.ID == user.ID {
					return &ForbiddenError{Message: usersLang + "self_deactivate"}
				}
				if err := guardOutranked(ctx, c.registry(), editor, user); err != nil {
					return err
				}
				if err := guardLastSuperuser(ctx, user); err != nil {
					return err
				}
				if err := db.Model(&BackendUser{}).Where("id = ?", user.ID).
					Updates(map[string]any{"is_activated": false, "tokens_valid_after": revocationCutoff()}).Error; err != nil {
					return err
				}
				// A deactivated administrator can no longer act anywhere,
				// an MCP session included.
				fireSubjectChanged(ctx, c.application(), pact.MCPSubjectDeleted, user.ID)
				return nil
			},
		},
		{
			name: "restore",
			applies: func(user *BackendUser, _ bool) bool {
				return user.DeletedAt.Valid
			},
			run: func(ctx context.Context, c usersAdmin, db *gorm.DB, editor *bouncer.Principal, user *BackendUser) error {
				if err := guardOutranked(ctx, c.registry(), editor, user); err != nil {
					return err
				}
				return db.Model(&BackendUser{}).Where("id = ?", user.ID).
					Update("deleted_at", nil).Error
			},
		},
	}
}

// actionDB is the action's write transaction as a fresh, unscoped session
// that every query starts from anew. The final Session matters: Unscoped
// returns an instance whose conditions accumulate, so a bulk action's
// second "id = ?" update would otherwise match no row.
func actionDB(ctx context.Context) (*gorm.DB, error) {
	tx, ok := TxFromContext(ctx)
	if !ok {
		return nil, errors.New("cabana: administrators: an action needs its transaction")
	}
	return tx.Session(&gorm.Session{NewDB: true}).WithContext(ctx).Unscoped().Session(&gorm.Session{}), nil
}

// AdminRecordActions are Activate, Deactivate and Restore on the preview
// (D-10), each offered only while it applies; at most one applies at a time.
// Every refusal is a ForbiddenError with a message (the admin's toast shows
// only the message).
func (c usersAdmin) AdminRecordActions() []pact.AdminRecordAction {
	lifecycles := c.lifecycles()
	out := make([]pact.AdminRecordAction, 0, len(lifecycles))
	for _, lifecycle := range lifecycles {
		lifecycle := lifecycle
		out = append(out, pact.AdminRecordAction{
			Name:        lifecycle.name,
			Label:       usersLang + lifecycle.name,
			Confirm:     usersLang + lifecycle.name + "_confirm",
			Permissions: []string{PermissionManageUsers},
			Applies: func(ctx context.Context, record any) (bool, error) {
				user, err := asBackendUser(record)
				if err != nil {
					return false, err
				}
				principal, _ := bouncer.User(ctx)
				return lifecycle.applies(user, principal != nil && principal.ID == user.ID), nil
			},
			Run: func(ctx context.Context, in pact.AdminRecordActionInput) (pact.AdminRecordActionResult, error) {
				user, err := asBackendUser(in.Record)
				if err != nil {
					return pact.AdminRecordActionResult{}, err
				}
				db, err := actionDB(ctx)
				if err != nil {
					return pact.AdminRecordActionResult{}, err
				}
				principal, _ := bouncer.User(ctx)
				if err := lifecycle.run(ctx, c, db, principal, user); err != nil {
					return pact.AdminRecordActionResult{}, err
				}
				return pact.AdminRecordActionResult{Message: usersLang + lifecycle.name + "d"}, nil
			},
		})
	}
	return out
}

// AdminBulkActions are Activate, Deactivate and Restore on the selected
// rows. A row the action does not apply to is skipped and not counted, the
// editor's own row refuses a deactivate, and one refused row rolls the
// whole selection back.
func (c usersAdmin) AdminBulkActions() []pact.AdminBulkAction {
	lifecycles := c.lifecycles()
	out := make([]pact.AdminBulkAction, 0, len(lifecycles))
	for _, lifecycle := range lifecycles {
		lifecycle := lifecycle
		out = append(out, pact.AdminBulkAction{
			Name:        lifecycle.name,
			Label:       usersLang + lifecycle.name,
			Confirm:     usersLang + lifecycle.name + "_selected_confirm",
			Permissions: []string{PermissionManageUsers},
			Run: func(ctx context.Context, in pact.AdminBulkActionInput) (pact.AdminBulkActionResult, error) {
				db, err := actionDB(ctx)
				if err != nil {
					return pact.AdminBulkActionResult{}, err
				}
				principal, _ := bouncer.User(ctx)
				affected := 0
				for _, record := range in.Records {
					user, err := asBackendUser(record)
					if err != nil {
						return pact.AdminBulkActionResult{}, err
					}
					// The editor's own row is checked by run, not skipped,
					// so a deactivate that selects it is refused.
					if !lifecycle.applies(user, false) {
						continue
					}
					if err := lifecycle.run(ctx, c, db, principal, user); err != nil {
						return pact.AdminBulkActionResult{}, err
					}
					affected++
				}
				result := pact.AdminBulkActionResult{Affected: affected}
				if affected == len(in.Records) {
					result.Message = usersLang + lifecycle.name + "d_selected"
				}
				return result, nil
			},
		})
	}
	return out
}

// usersHintView is the view model of controllers/users/_hint.htm, the status
// callout above the preview: the callout kind (danger or warning) and the
// phrase keys of its title and text. It is empty when no state applies, and
// the template then renders nothing.
type usersHintView struct {
	Kind  string
	Title string
	Text  string
}

// PartialData serves the preview header partial hint: one callout by
// precedence deleted, deactivated, the editor's own account.
func (usersAdmin) PartialData(ctx context.Context, name string, record any) (any, error) {
	if name != "hint" {
		return nil, fmt.Errorf("cabana: administrators: unknown partial %q", name)
	}
	user, ok := record.(*BackendUser)
	if !ok || user == nil {
		return usersHintView{}, nil
	}
	principal, _ := bouncer.User(ctx)
	switch {
	case user.DeletedAt.Valid:
		return usersHintView{Kind: "danger", Title: usersLang + "trashed_hint_title", Text: usersLang + "trashed_hint_desc"}, nil
	case !user.IsActivated:
		return usersHintView{Kind: "warning", Title: usersLang + "deactivated_hint_title", Text: usersLang + "deactivated_hint_desc"}, nil
	case principal != nil && principal.ID == user.ID:
		return usersHintView{Kind: "warning", Title: usersLang + "self_hint_title", Text: usersLang + "self_hint_desc"}, nil
	}
	return usersHintView{}, nil
}

// extendRecordData sends the stored superuser flag to a superuser. The
// is_superuser switch is a virtual field (the column is protected), and the
// admin sends every field on save: without its stored value an untouched
// save would demote a superuser.
func (usersAdmin) extendRecordData(ctx context.Context, record any, data map[string]any) {
	user, ok := record.(*BackendUser)
	if !ok || user == nil {
		return
	}
	if principal, _ := bouncer.User(ctx); actsAsSuperuser(principal) {
		data[usersSuperuserField] = user.IsSuperuser
	}
}

// hiddenSchemaFields removes the superuser field, column and filter for an
// administrator who does not act as a superuser (D-03).
func (usersAdmin) hiddenSchemaFields(ctx context.Context) map[string]bool {
	if principal, _ := bouncer.User(ctx); actsAsSuperuser(principal) {
		return nil
	}
	return map[string]bool{usersSuperuserField: true}
}

// FormVirtualFields are the password, its confirmation and the superuser
// switch: none is filled into the model; the Form hooks write them after
// their checks.
func (usersAdmin) FormVirtualFields() []string {
	return []string{"password", "password_confirmation", usersSuperuserField}
}

// FormRules require a confirmed password of at least 4 characters on create
// and take one on update only when it is typed (D-11). Login and email
// uniqueness is checked by checkIdentity, deleted administrators included.
func (usersAdmin) FormRules(_ context.Context, op string) map[string]string {
	password := "nullable|min:4|confirmed"
	if op == "create" {
		password = "required|min:4|confirmed"
	}
	return map[string]string{
		"login":    "required|max:255",
		"email":    "required|email|max:255",
		"password": password,
	}
}

// FilterOptions serves the role filter's choices, every role by name, and
// the deleted filter's two choices.
func (c usersAdmin) FilterOptions(scope string) []pact.Option {
	if scope == filterTrashed {
		return []pact.Option{
			{Value: trashedHide, Label: usersLang + "filter_deleted_hide"},
			{Value: trashedOnly, Label: usersLang + "filter_deleted_only"},
		}
	}
	if scope != filterByRole {
		return nil
	}
	db := c.db()
	if db == nil {
		return nil
	}
	var roles []BackendUserRole
	if err := db.Session(&gorm.Session{NewDB: true}).Order("name ASC, id ASC").Find(&roles).Error; err != nil {
		return nil
	}
	out := make([]pact.Option, 0, len(roles))
	for _, role := range roles {
		out = append(out, pact.Option{Value: strconv.FormatUint(uint64(role.ID), 10), Label: role.Name})
	}
	return out
}

// AdminRelationLocks locks, for an administrator who does not act as a
// superuser, every role whose grants (stored and code-declared) the
// administrator does not hold themselves (D-07): it cannot be assigned, and
// an administrator who holds one keeps it unchanged.
func (c usersAdmin) AdminRelationLocks(ctx context.Context, field string) (RelationLock, error) {
	if field != usersRoleField {
		return RelationLock{}, nil
	}
	principal, _ := bouncer.User(ctx)
	if actsAsSuperuser(principal) {
		return RelationLock{}, nil
	}
	db := c.requestDB(ctx)
	if db == nil {
		return RelationLock{}, errors.New("cabana: administrators: database handle is missing")
	}
	var roles []BackendUserRole
	if err := db.Session(&gorm.Session{NewDB: true}).WithContext(ctx).Order("id ASC").Find(&roles).Error; err != nil {
		return RelationLock{}, err
	}
	var held map[string]bool
	if principal != nil {
		held = principal.PermissionGrants
	}
	var ids []uint
	for _, role := range roles {
		if !grantsCovered(held, roleGrantSet(c.registry(), role)) {
			ids = append(ids, role.ID)
		}
	}
	return RelationLock{IDs: ids, Message: usersLang + "role_ceiling"}, nil
}

// permissionComments are the editor comments of the admin's own permissions.
var permissionComments = map[string]string{
	PermissionManageUsers: "backend::lang.permissions.manage_users_comment",
	PermissionManageRoles: "backend::lang.permissions.manage_roles_comment",
}

// catalogOptions lists the permission catalog in registration order; a
// code the administrator on ctx may not grant is locked (D-07).
func catalogOptions(ctx context.Context, reg *Registry) []PermissionOption {
	principal, _ := bouncer.User(ctx)
	superuser := actsAsSuperuser(principal)
	var held map[string]bool
	if principal != nil {
		held = principal.PermissionGrants
	}
	if reg == nil {
		return nil
	}
	out := make([]PermissionOption, 0, len(reg.permissionOrder))
	for _, code := range reg.permissionOrder {
		permission := reg.permissions[code]
		label := permission.Label
		if label == "" {
			label = code
		}
		out = append(out, PermissionOption{
			Code:    code,
			Label:   label,
			Tab:     permission.Tab,
			Comment: permissionComments[code],
			Locked:  !superuser && !granted(held, code),
		})
	}
	return out
}

// AdminPermissionOptions offers the whole permission catalog on the
// per-administrator override editor (mode radio).
func (c usersAdmin) AdminPermissionOptions(ctx context.Context, field string) ([]PermissionOption, error) {
	if field != usersPermissionsField {
		return nil, fmt.Errorf("cabana: administrators: unknown permission field %q", field)
	}
	return catalogOptions(ctx, c.registry()), nil
}

// AdminPermissionValues decodes the administrator's stored overrides: 1
// (allow) and -1 (deny); any other stored value is left out.
func (usersAdmin) AdminPermissionValues(_ context.Context, field string, record any) (map[string]int, error) {
	user, ok := record.(*BackendUser)
	if field != usersPermissionsField || !ok || user == nil {
		return nil, fmt.Errorf("cabana: administrators: cannot read permission field %q", field)
	}
	return decodePermissionValues(user.Permissions, true), nil
}

// AdminPermissionRecordLocks locks every offered permission on the
// editor's own record, shown with its stored override (1, -1, or 0 for
// inherit) and the locked_self note (D-08); other records have none.
// AdminSetPermissionValues still refuses a change on the own record.
func (c usersAdmin) AdminPermissionRecordLocks(ctx context.Context, field string, record any) ([]PermissionRecordLock, error) {
	user, ok := record.(*BackendUser)
	if field != usersPermissionsField || !ok || user == nil {
		return nil, fmt.Errorf("cabana: administrators: cannot read permission field %q", field)
	}
	principal, _ := bouncer.User(ctx)
	if principal == nil || user.ID == 0 || principal.ID != user.ID {
		return nil, nil
	}
	stored := decodePermissionValues(user.Permissions, true)
	options := catalogOptions(ctx, c.registry())
	out := make([]PermissionRecordLock, 0, len(options))
	for _, option := range options {
		out = append(out, PermissionRecordLock{Code: option.Code, Value: stored[option.Code], Note: permissionLockedSelfKey})
	}
	return out, nil
}

// permissionLockedSelfKey is the note of every permission on the editor's
// own Administrators record.
const permissionLockedSelfKey = "backend::lang.permissioneditor.locked_self"

// AdminSetPermissionValues stores the override set on the record; the save
// writes the row. On the editor's own record any change is refused (D-08).
func (usersAdmin) AdminSetPermissionValues(ctx context.Context, field string, record any, values map[string]int) error {
	user, ok := record.(*BackendUser)
	if field != usersPermissionsField || !ok || user == nil {
		return fmt.Errorf("cabana: administrators: cannot write permission field %q", field)
	}
	if principal, _ := bouncer.User(ctx); principal != nil && user.ID != 0 && principal.ID == user.ID {
		if !samePermissionValues(decodePermissionValues(user.Permissions, true), values) {
			return &ForbiddenError{Message: usersLang + "self_privileged", Details: map[string]any{usersPermissionsField: []string{usersLang + "self_privileged"}}}
		}
	}
	encoded, err := encodePermissionValues(values)
	if err != nil {
		return err
	}
	user.Permissions = encoded
	return nil
}

// decodePermissionValues reads a stored permissions JSON object into code
// to value: 1 for a grant and, when deny is set, -1 for a deny. Malformed
// JSON and any other value read as absent.
func decodePermissionValues(raw string, deny bool) map[string]int {
	out := map[string]int{}
	raw = strings.TrimSpace(raw)
	if raw == "" || raw == "null" {
		return out
	}
	var decoded map[string]any
	if err := json.Unmarshal([]byte(raw), &decoded); err != nil {
		return out
	}
	for code, value := range decoded {
		switch {
		case truthyGrant(value):
			out[code] = 1
		case deny && denyGrant(value):
			out[code] = -1
		}
	}
	return out
}

// denyGrant reports a stored -1.
func denyGrant(value any) bool {
	switch v := value.(type) {
	case float64:
		return v == -1
	case string:
		return strings.TrimSpace(v) == "-1"
	case json.Number:
		return v.String() == "-1"
	}
	return false
}

func samePermissionValues(a, b map[string]int) bool {
	count := 0
	for code, n := range b {
		if n == 0 {
			continue
		}
		if a[code] != n {
			return false
		}
		count++
	}
	return count == len(a)
}

// encodePermissionValues is the compact JSON object of the non-zero values,
// "{}" when there are none.
func encodePermissionValues(values map[string]int) (string, error) {
	out := make(map[string]int, len(values))
	for code, n := range values {
		if n != 0 {
			out[code] = n
		}
	}
	raw, err := json.Marshal(out)
	if err != nil {
		return "", err
	}
	return string(raw), nil
}

// toggleOn reads a switch value as the admin sends it.
func toggleOn(value any) bool {
	switch v := value.(type) {
	case bool:
		return v
	case string:
		return v == "1" || strings.EqualFold(v, "true")
	case json.Number:
		return v.String() == "1"
	case float64:
		return v == 1
	}
	return false
}

// FormBeforeCreate checks and writes the protected values of a new
// administrator: only a superuser may send the superuser switch, whatever
// its value (D-05); the account starts activated, as admin:create creates
// it; the password is hashed at admin.password.bcrypt_cost (D-11); and the
// login and email must be free. No mail is sent (D-13).
func (c usersAdmin) FormBeforeCreate(ctx context.Context, model any) error {
	user, err := asBackendUser(model)
	if err != nil {
		return err
	}
	principal, _ := bouncer.User(ctx)
	values, _ := VirtualFieldsFromContext(ctx)
	if value, sent := values[usersSuperuserField]; sent {
		if !actsAsSuperuser(principal) {
			return &ForbiddenError{Message: usersLang + "superuser_forbidden", Details: map[string]any{usersSuperuserField: []string{usersLang + "superuser_forbidden"}}}
		}
		user.IsSuperuser = toggleOn(value)
	} else {
		user.IsSuperuser = false
	}
	now := time.Now().UTC()
	user.IsActivated = true
	user.ActivatedAt = &now
	if _, err := c.storePassword(ctx, user); err != nil {
		return err
	}
	return c.checkIdentity(ctx, user)
}

// FormBeforeUpdate runs before the submitted role and permissions are
// applied, while the model still holds the stored role, flag and overrides
// (protected columns are never filled). It snapshots the role for
// FormAfterUpdate, refuses a change to an administrator who outranks the
// editor (D-19), checks the superuser switch (D-05, D-08, D-09), hashes a
// typed password for another administrator and ends their sessions (D-11,
// D-12; their own password is changed in My account, D-20), and checks the
// login and email.
func (c usersAdmin) FormBeforeUpdate(ctx context.Context, model any) error {
	user, err := asBackendUser(model)
	if err != nil {
		return err
	}
	principal, _ := bouncer.User(ctx)
	self := principal != nil && principal.ID == user.ID
	if user.RoleID != nil {
		prior := *user.RoleID
		user.priorRoleID = &prior
	} else {
		user.priorRoleID = nil
	}
	user.priorPermissions = user.Permissions
	user.priorSuperuser = user.IsSuperuser
	user.priorLoaded = true
	if !self {
		if err := guardOutranked(ctx, c.registry(), principal, user); err != nil {
			return err
		}
	}
	values, _ := VirtualFieldsFromContext(ctx)
	if value, sent := values[usersSuperuserField]; sent {
		superuserDetails := func(key string) map[string]any {
			return map[string]any{usersSuperuserField: []string{key}}
		}
		if !actsAsSuperuser(principal) {
			return &ForbiddenError{Message: usersLang + "superuser_forbidden", Details: superuserDetails(usersLang + "superuser_forbidden")}
		}
		want := toggleOn(value)
		if self && want != user.IsSuperuser {
			return &ForbiddenError{Message: usersLang + "self_privileged", Details: superuserDetails(usersLang + "self_privileged")}
		}
		if user.IsSuperuser && !want {
			if err := guardLastSuperuser(ctx, user); err != nil {
				var refused *ForbiddenError
				if errors.As(err, &refused) {
					return &ForbiddenError{Message: refused.Message, Details: superuserDetails(refused.Message)}
				}
				return err
			}
		}
		user.IsSuperuser = want
	}
	if plain := submittedPassword(ctx); plain != "" && self {
		return &ForbiddenError{Message: usersLang + "own_password", Details: map[string]any{"password": []string{usersLang + "own_password"}}}
	}
	changed, err := c.storePassword(ctx, user)
	if err != nil {
		return err
	}
	if changed {
		cutoff := revocationCutoff()
		user.TokensValidAfter = &cutoff
	}
	return c.checkIdentity(ctx, user)
}

// FormAfterUpdate refuses a change of the editor's own role (D-08). The
// submitted role is assigned after FormBeforeUpdate, so it is compared here,
// with the row written: the refusal rolls the save back. A save that changed
// the administrator's role, own permissions or superuser flag then fires
// pact.MCPSubjectChanged (permissions) for them.
func (c usersAdmin) FormAfterUpdate(ctx context.Context, model any) error {
	user, err := asBackendUser(model)
	if err != nil {
		return err
	}
	if !user.priorLoaded {
		return nil
	}
	principal, _ := bouncer.User(ctx)
	if principal != nil && principal.ID == user.ID && !sameRoleID(user.priorRoleID, user.RoleID) {
		return &ForbiddenError{Message: usersLang + "self_privileged", Details: map[string]any{usersRoleField: []string{usersLang + "self_privileged"}}}
	}
	if !sameRoleID(user.priorRoleID, user.RoleID) || user.priorPermissions != user.Permissions || user.priorSuperuser != user.IsSuperuser {
		fireSubjectChanged(ctx, c.application(), pact.MCPSubjectPermissions, user.ID)
	}
	return nil
}

func sameRoleID(a, b *uint) bool {
	switch {
	case a == nil || *a == 0:
		return b == nil || *b == 0
	case b == nil:
		return false
	}
	return *a == *b
}

// submittedPassword is the password typed on the form, "" when none.
func submittedPassword(ctx context.Context) string {
	values, _ := VirtualFieldsFromContext(ctx)
	plain, _ := values["password"].(string)
	return plain
}

// adminPasswordMinChars is the shortest password the Administrators form
// accepts, in characters (D-11).
const adminPasswordMinChars = 4

// storePassword hashes a typed password onto user and reports whether one
// was typed. A password under adminPasswordMinChars characters or over
// bcrypt's 72-byte limit is a 422 on the field. The length is checked here
// because the form's min:4 rule is a string rule, which the model validator
// does not apply.
func (c usersAdmin) storePassword(ctx context.Context, user *BackendUser) (bool, error) {
	plain := submittedPassword(ctx)
	if plain == "" {
		return false, nil
	}
	if utf8.RuneCountInString(plain) < adminPasswordMinChars {
		message := accountMessage(ctx, c.translator(), "min.string", "password", map[string]string{"min": strconv.Itoa(adminPasswordMinChars)})
		return false, &ValidationError{Details: map[string]any{"password": []string{message}}}
	}
	if len(plain) > passwordMaxBytes {
		message := accountMessage(ctx, c.translator(), "max.string", "password", map[string]string{"max": strconv.Itoa(passwordMaxBytes)})
		return false, &ValidationError{Details: map[string]any{"password": []string{message}}}
	}
	hash, err := bouncer.HashPassword(adminBcryptCost(c.application()), plain)
	if err != nil {
		return false, err
	}
	user.Password = hash
	return true, nil
}

// checkIdentity refuses a login or email another administrator already
// uses, in either field and ignoring case, deleted administrators included
// (the database keeps their values unique), as admin:create does. A value
// only a deleted administrator holds says so, so the editor can restore
// that account instead.
func (c usersAdmin) checkIdentity(ctx context.Context, user *BackendUser) error {
	db := c.requestDB(ctx)
	if db == nil {
		return errors.New("cabana: administrators: database handle is missing")
	}
	login := strings.ToLower(strings.TrimSpace(user.Login))
	email := strings.ToLower(strings.TrimSpace(user.Email))
	var holders []BackendUser
	err := db.Session(&gorm.Session{NewDB: true}).WithContext(ctx).Unscoped().
		Select("id", "login", "email", "deleted_at").
		Where("(lower(login) IN (?, ?) OR lower(email) IN (?, ?)) AND id <> ?", login, email, login, email, user.ID).
		Find(&holders).Error
	if err != nil {
		return err
	}
	details := map[string]any{}
	for _, field := range []struct{ name, value string }{{"login", login}, {"email", email}} {
		if field.value == "" {
			continue
		}
		held, active := false, false
		for _, holder := range holders {
			if strings.ToLower(holder.Login) == field.value || strings.ToLower(holder.Email) == field.value {
				held = true
				active = active || !holder.DeletedAt.Valid
			}
		}
		switch {
		case !held:
		case active:
			details[field.name] = []string{usersLang + field.name + "_taken"}
		default:
			details[field.name] = []string{usersLang + field.name + "_taken_deleted"}
		}
	}
	if len(details) > 0 {
		return &ValidationError{Details: details}
	}
	return nil
}