package controllers

import (
	"context"
	"errors"
	"fmt"
	"regexp"

	"git.golem15.com/golem15/sm-user-plugin/classes"
	"git.golem15.com/golem15/sm-user-plugin/models"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"gorm.io/gorm"
)

// PermissionAccessGroups is the backend permission of the User Groups
// screen, the PHP UserGroups::$requiredPermissions.
const PermissionAccessGroups = "golem15.users.access_groups"

// groupsLang prefixes the phrase keys of the User Groups screen.
const groupsLang = "golem15.user::lang.groups."

// groupCodePattern is the PHP UserGroup code rule
// regex:/^[a-zA-Z0-9_\-]+$/. lagoon.Validate has no regex token, so the
// Form before-hooks check it.
var groupCodePattern = regexp.MustCompile(`^[a-zA-Z0-9_-]+$`)

// usergroupsAdminController is the Winter UserGroups backend controller: the
// list with the member count and the form with the frontend permissions of
// the group. The screen and every write need golem15.users.access_groups.
//
// A group's code decides whether its members are privileged
// (golem15.user.privileged_groups), so three writes additionally need
// golem15.users.manage_privileged_groups: creating a group with a privileged
// code, changing a code to or from a privileged one, and deleting a
// privileged group. Everything else on a privileged group (its name,
// description and frontend permissions) needs only the screen's permission.
//
// The screen never writes a membership: users_groups changes only through
// the user form's groups field, and loses the rows of a deleted group.
type usergroupsAdminController struct {
	app appAccess
}

func (usergroupsAdminController) ID() string { return "golem15.user.usergroups" }

func (usergroupsAdminController) ModelName() string { return `Golem15\User\Models\UserGroup` }

func (usergroupsAdminController) ConfigDir() string { return "controllers/usergroups" }

func (usergroupsAdminController) RequiredPermissions() []string {
	return []string{PermissionAccessGroups}
}

func (usergroupsAdminController) NewRecord() any { return &models.UserGroup{} }

// ListExtendQuery adds the member count of every group on the page, the PHP
// users_count relation column, in the list's own query. The two select
// arguments keep the list's count query a plain COUNT(*).
func (usergroupsAdminController) ListExtendQuery(_ context.Context, db *gorm.DB) *gorm.DB {
	if db == nil {
		return db
	}
	return db.Select("user_groups.*",
		"(SELECT COUNT(*) FROM users_groups WHERE users_groups.user_group_id = user_groups.id) AS users_count")
}

// FormBeforeCreate checks the code's format and refuses a privileged code
// without golem15.users.manage_privileged_groups.
func (c usergroupsAdminController) FormBeforeCreate(ctx context.Context, model any) error {
	group, ok := model.(*models.UserGroup)
	if !ok || group == nil {
		return errors.New("user groups admin: form model is not a user group")
	}
	if err := c.requireCodeFormat(ctx, group); err != nil {
		return err
	}
	if !classes.IsPrivilegedCode(classes.PrivilegedGroupCodes(c.app.config()), group.Code) {
		return nil
	}
	return c.requirePrivilegedPermission(ctx)
}

// FormBeforeUpdate checks the code's format and refuses a code change to or
// from a privileged code without golem15.users.manage_privileged_groups. The
// stored code is read through the write's transaction; a save that leaves
// the code as it is passes, whatever the code.
func (c usergroupsAdminController) FormBeforeUpdate(ctx context.Context, model any) error {
	group, ok := model.(*models.UserGroup)
	if !ok || group == nil {
		return errors.New("user groups admin: form model is not a user group")
	}
	if err := c.requireCodeFormat(ctx, group); err != nil {
		return err
	}
	db := requestDB(ctx, c.app.db)
	if db == nil {
		return errors.New("user groups admin: gorm handle is missing")
	}
	var stored []struct{ Code *string }
	err := db.Session(&gorm.Session{NewDB: true}).WithContext(ctx).
		Table("user_groups").Select("code").Where("id = ?", group.ID).Scan(&stored).Error
	if err != nil {
		return err
	}
	if len(stored) != 1 {
		return errors.New("user groups admin: the group being updated was not found")
	}
	if sameCode(stored[0].Code, group.Code) {
		return nil
	}
	codes := classes.PrivilegedGroupCodes(c.app.config())
	if !classes.IsPrivilegedCode(codes, stored[0].Code) && !classes.IsPrivilegedCode(codes, group.Code) {
		return nil
	}
	return c.requirePrivilegedPermission(ctx)
}

// FormBeforeDelete refuses the delete of a privileged group without
// golem15.users.manage_privileged_groups: it would take the privilege from
// every member. The record is the stored row, loaded in the delete's
// transaction.
func (c usergroupsAdminController) FormBeforeDelete(ctx context.Context, model any) error {
	group, ok := model.(*models.UserGroup)
	if !ok || group == nil {
		return errors.New("user groups admin: form model is not a user group")
	}
	if !classes.IsPrivilegedCode(classes.PrivilegedGroupCodes(c.app.config()), group.Code) {
		return nil
	}
	return c.requirePrivilegedPermission(ctx)
}

// FormAfterDelete removes the memberships of the deleted group in the same
// transaction: users_groups has no foreign key that would do it. The member
// users stay.
func (usergroupsAdminController) FormAfterDelete(ctx context.Context, model any) error {
	group, ok := model.(*models.UserGroup)
	if !ok || group == nil {
		return errors.New("user groups admin: form model is not a user group")
	}
	tx, ok := cabana.TxFromContext(ctx)
	if !ok {
		return errors.New("user groups admin: a delete needs its transaction")
	}
	return tx.Session(&gorm.Session{NewDB: true}).WithContext(ctx).
		Where("user_group_id = ?", group.ID).Delete(&models.UsersGroup{}).Error
}

// requirePrivilegedPermission answers nil when the administrator on ctx
// holds golem15.users.manage_privileged_groups, else the 403 of the screen.
// A context without a principal is refused.
func (usergroupsAdminController) requirePrivilegedPermission(ctx context.Context) error {
	principal, _ := bouncer.User(ctx)
	if cabana.Allows(principal, []string{classes.PermissionManagePrivilegedGroups}) {
		return nil
	}
	const message = groupsLang + "privileged_forbidden"
	return &cabana.ForbiddenError{Message: message, Details: map[string]any{"code": []string{message}}}
}

// requireCodeFormat answers 422 on code when it holds anything but letters,
// digits, underscore and hyphen. An empty code is left to the required rule.
func (c usergroupsAdminController) requireCodeFormat(ctx context.Context, group *models.UserGroup) error {
	if group.Code == nil || *group.Code == "" || groupCodePattern.MatchString(*group.Code) {
		return nil
	}
	message := "The code may only contain letters, numbers, dashes and underscores."
	if tr := c.app.translator(); tr != nil {
		const key = "golem15.user::lang.group.code_invalid"
		if text := tr.Get(ctx, key, nil); text != "" && text != key {
			message = text
		}
	}
	return &cabana.ValidationError{Details: map[string]any{"code": []string{message}}}
}

// sameCode compares two nullable group codes, case-sensitively.
func sameCode(a, b *string) bool {
	if a == nil || b == nil {
		return a == nil && b == nil
	}
	return *a == *b
}

// AdminPermissionOptions offers the rows of
// golem15_user_frontend_permissions, by tab and code. None is locked.
func (c usergroupsAdminController) AdminPermissionOptions(ctx context.Context, field string) ([]cabana.PermissionOption, error) {
	if field != permissionsField {
		return nil, fmt.Errorf("user groups admin: unknown permission field %q", field)
	}
	db := requestDB(ctx, c.app.db)
	if db == nil {
		return nil, errors.New("user groups admin: gorm handle is missing")
	}
	rows, err := classes.FrontendPermissionOptions(ctx, db)
	if err != nil {
		return nil, err
	}
	options := make([]cabana.PermissionOption, 0, len(rows))
	for _, row := range rows {
		option := cabana.PermissionOption{Code: row.Code, Label: row.Label, Tab: row.Tab}
		if row.Comment != nil {
			option.Comment = *row.Comment
		}
		options = append(options, option)
	}
	return options, nil
}

// AdminPermissionValues returns the group's stored permissions, read with
// the tolerance of models.ParsePermissionSet.
func (usergroupsAdminController) AdminPermissionValues(_ context.Context, field string, record any) (map[string]int, error) {
	group, ok := record.(*models.UserGroup)
	if field != permissionsField || !ok || group == nil {
		return nil, fmt.Errorf("user groups admin: cannot read permission field %q", field)
	}
	if group.Permissions == nil {
		return map[string]int{}, nil
	}
	set, err := models.ParsePermissionSet([]byte(*group.Permissions))
	if err != nil {
		return nil, err
	}
	values := make(map[string]int, len(set))
	for code, value := range set {
		values[code] = value
	}
	return values, nil
}

// AdminSetPermissionValues writes the validated set back as the JSON object
// PHP stores (checkbox mode: 1 per allowed code), or NULL for an empty set.
// The save writes the row.
func (usergroupsAdminController) AdminSetPermissionValues(_ context.Context, field string, record any, values map[string]int) error {
	group, ok := record.(*models.UserGroup)
	if field != permissionsField || !ok || group == nil {
		return fmt.Errorf("user groups admin: cannot write permission field %q", field)
	}
	set := make(models.PermissionSet, len(values))
	for code, value := range values {
		set[code] = value
	}
	group.Permissions = set.Text()
	return nil
}