package database

import (
	"RenewCMS/internal/domain/role"
	entity "RenewCMS/internal/infrastructure/persistence/models"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

const (
	usersTable         = "users"
	legacyRoleColumn   = "role"
	legacyOwnerValue   = "owner"
	legacyAdminValue   = "admin"
	legacyUnsetValue   = ""
	unassignedRoleCond = "(role_id IS NULL OR role_id = 0)"
)

func legacyRoleColumnExists(db *gorm.DB) bool {
	return db.Migrator().HasColumn(usersTable, legacyRoleColumn)
}

func requireBuiltInRoleID(tx *gorm.DB, name string) (uint32, error) {
	id, found, err := builtInRoleID(tx, name)
	if err != nil {
		return 0, err
	}
	if !found {
		return 0, role.ErrRoleNotFound
	}
	return id, nil
}

func BackfillLegacyUserRoles(db *gorm.DB) error {
	if !legacyRoleColumnExists(db) {
		return nil
	}
	return db.Transaction(func(tx *gorm.DB) error {
		done, err := markerApplied(tx, legacyUserRolesMarker)
		if err != nil || done {
			return err
		}
		ownerID, err := requireBuiltInRoleID(tx, role.OwnerName)
		if err != nil {
			return err
		}
		adminID, err := requireBuiltInRoleID(tx, role.AdminName)
		if err != nil {
			return err
		}
		writerID, err := requireBuiltInRoleID(tx, role.WriterName)
		if err != nil {
			return err
		}
		legacy := clause.Column{Name: legacyRoleColumn}
		assign := func(roleID uint32, condition string, args ...any) error {
			return tx.Table(usersTable).Where(unassignedRoleCond).Where(condition, args...).UpdateColumn("role_id", roleID).Error
		}
		var owners []uint32
		if err := tx.Table(usersTable).Where(unassignedRoleCond).Where("? = ?", legacy, legacyOwnerValue).Order("id asc").Pluck("id", &owners).Error; err != nil {
			return err
		}
		if len(owners) > 0 {
			if err := assign(ownerID, "id = ?", owners[0]); err != nil {
				return err
			}
		}
		if err := assign(adminID, "? = ?", legacy, legacyOwnerValue); err != nil {
			return err
		}
		if err := assign(adminID, "? = ?", legacy, legacyAdminValue); err != nil {
			return err
		}
		if len(owners) == 0 {
			var lowest []uint32
			if err := tx.Model(&entity.User{}).Order("id asc").Limit(1).Pluck("id", &lowest).Error; err != nil {
				return err
			}
			if len(lowest) > 0 {
				if err := assign(ownerID, "? = ? AND id = ?", legacy, legacyUnsetValue, lowest[0]); err != nil {
					return err
				}
			}
		}
		if err := assign(adminID, "? = ?", legacy, legacyUnsetValue); err != nil {
			return err
		}
		if err := assign(writerID, "1 = 1"); err != nil {
			return err
		}
		return applyMarker(tx, legacyUserRolesMarker)
	})
}