package service

import (
	"errors"

	"affiliate_dash/internal/model"

	"golang.org/x/crypto/bcrypt"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

type UserService struct {
	db     *gorm.DB
	tenant *TenantService
}

func NewUserService(db *gorm.DB, tenant *TenantService) *UserService {
	return &UserService{db: db, tenant: tenant}
}

type UserListQuery struct {
	MerchantID uint
	Page       int
	Size       int
	Keyword    string
	Role       string
	Status     *int
}

// MerchantMemberGroup presents merchant accounts in their actual ownership
// hierarchy: one merchant and all of its employee accounts.
type MerchantMemberGroup struct {
	MerchantID uint                   `json:"merchant_id"`
	Merchant   *model.Merchant        `json:"merchant,omitempty"`
	Members    []model.MerchantMember `json:"members"`
}

func (s *UserService) List(q UserListQuery) ([]model.User, int64, error) {
	if q.Page < 1 {
		q.Page = 1
	}
	if q.Size < 1 || q.Size > 100 {
		q.Size = 20
	}
	tx := s.db.Model(&model.User{})
	if q.MerchantID != 0 {
		tx = tx.Joins("JOIN merchant_members ON merchant_members.user_id = users.id").
			Where("merchant_members.merchant_id = ?", q.MerchantID)
	}
	if q.Keyword != "" {
		like := "%" + q.Keyword + "%"
		tx = tx.Where("users.username LIKE ? OR users.nickname LIKE ?", like, like)
	}
	if q.Role != "" {
		tx = tx.Where("users.role = ?", q.Role)
	}
	if q.Status != nil {
		tx = tx.Where("users.status = ?", *q.Status)
	}
	var total int64
	if err := tx.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var list []model.User
	err := tx.Order("users.id DESC").Offset((q.Page - 1) * q.Size).Limit(q.Size).Find(&list).Error
	return list, total, err
}

func (s *UserService) Create(username, password, nickname, role string, merchantID uint) (*model.User, error) {
	var count int64
	s.db.Model(&model.User{}).Where("username = ?", username).Count(&count)
	if count > 0 {
		return nil, errors.New("用户名已存在")
	}
	if role == "" {
		role = model.RoleMerchant
	}
	if role != model.RoleAdmin && role != model.RoleMerchant {
		return nil, errors.New("无效的账号角色")
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return nil, err
	}
	user := &model.User{
		Username:     username,
		PasswordHash: string(hash),
		Nickname:     nickname,
		Role:         role,
		Status:       1,
	}
	if user.Nickname == "" {
		user.Nickname = username
	}
	err = s.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(user).Error; err != nil {
			return err
		}
		if role == model.RoleAdmin && s.tenant != nil {
			var selfMerchant model.Merchant
			if err := tx.Where("code = ?", model.MerchantCodeSelfOperated).First(&selfMerchant).Error; err != nil {
				return err
			}
			member := model.MerchantMember{MerchantID: selfMerchant.ID, UserID: user.ID, Role: model.MemberRoleOwner, Status: user.Status, IsDefault: true}
			if err := tx.Clauses(clause.OnConflict{
				Columns: []clause.Column{{Name: "merchant_id"}, {Name: "user_id"}},
				DoUpdates: clause.Assignments(map[string]interface{}{
					"role": model.MemberRoleOwner, "status": user.Status, "is_default": true,
				}),
			}).Create(&member).Error; err != nil {
				return err
			}
			return nil
		}
		if s.tenant != nil && merchantID != 0 {
			memberRole := model.MemberRoleOperator
			member := model.MerchantMember{
				MerchantID: merchantID,
				UserID:     user.ID,
				Role:       memberRole,
				Status:     user.Status,
				IsDefault:  false,
			}
			if err := tx.Create(&member).Error; err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	return user, nil
}

type UpdatePlatformAdminInput struct {
	Username string
	Nickname string
	Password string
	Status   int
}

func (s *UserService) ListPlatformAdmins(page, size int) ([]model.User, int64, error) {
	return s.List(UserListQuery{Page: page, Size: size, Role: model.RoleAdmin})
}

// ListMerchantAccountGroups returns merchant employee accounts grouped by
// merchant. Platform administrators are excluded from this independent view.
func (s *UserService) ListMerchantAccountGroups(page, size int) ([]MerchantMemberGroup, int64, error) {
	page, size = normalizePage(page, size)
	tx := s.db.Model(&model.MerchantMember{}).
		Joins("JOIN users ON users.id = merchant_members.user_id AND users.deleted_at IS NULL").
		Where("users.role = ?", model.RoleMerchant)

	var total int64
	if err := tx.Distinct("merchant_members.merchant_id").Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var merchantIDs []uint
	if err := tx.Distinct("merchant_members.merchant_id").
		Order("merchant_members.merchant_id ASC").
		Offset((page-1)*size).Limit(size).
		Pluck("merchant_members.merchant_id", &merchantIDs).Error; err != nil {
		return nil, 0, err
	}
	if len(merchantIDs) == 0 {
		return []MerchantMemberGroup{}, total, nil
	}

	var members []model.MerchantMember
	if err := s.db.Model(&model.MerchantMember{}).
		Joins("JOIN users ON users.id = merchant_members.user_id AND users.deleted_at IS NULL").
		Where("users.role = ? AND merchant_members.merchant_id IN ?", model.RoleMerchant, merchantIDs).
		Preload("Merchant").Preload("User").
		Order("merchant_members.merchant_id ASC, merchant_members.id ASC").
		Find(&members).Error; err != nil {
		return nil, 0, err
	}

	groups := make([]MerchantMemberGroup, 0, len(merchantIDs))
	byMerchantID := make(map[uint]*MerchantMemberGroup, len(merchantIDs))
	for _, merchantID := range merchantIDs {
		groups = append(groups, MerchantMemberGroup{MerchantID: merchantID, Members: []model.MerchantMember{}})
		byMerchantID[merchantID] = &groups[len(groups)-1]
	}
	for _, member := range members {
		group := byMerchantID[member.MerchantID]
		if group.Merchant == nil {
			group.Merchant = member.Merchant
		}
		group.Members = append(group.Members, member)
	}
	return groups, total, nil
}

// CreatePlatformAdmin creates an account with platform privileges and the
// hidden self-operated merchant context required by merchant-side routes.
func (s *UserService) CreatePlatformAdmin(username, password, nickname string) (*model.User, error) {
	return s.Create(username, password, nickname, model.RoleAdmin, 0)
}

func (s *UserService) UpdatePlatformAdmin(id uint, in UpdatePlatformAdminInput, actorUserID uint) (*model.User, error) {
	if id == 0 {
		return nil, errors.New("用户不存在")
	}
	if id == actorUserID {
		return nil, errors.New("当前账号请通过右上角账户菜单修改密码")
	}
	if in.Status != 0 && in.Status != 1 {
		return nil, errors.New("用户状态无效")
	}
	returnUser := &model.User{}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		var user model.User
		if err := tx.First(&user, id).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errors.New("用户不存在")
			}
			return err
		}
		if user.Role != model.RoleAdmin {
			return errors.New("只能管理平台管理员账号")
		}
		if user.Status == 1 && in.Status == 0 {
			var admins int64
			if err := tx.Model(&model.User{}).Where("role = ? AND status = ?", model.RoleAdmin, 1).Count(&admins).Error; err != nil {
				return err
			}
			if admins <= 1 {
				return errors.New("至少保留一个启用的平台管理员")
			}
		}
		if in.Username != user.Username {
			var count int64
			if err := tx.Model(&model.User{}).Where("username = ? AND id <> ?", in.Username, user.ID).Count(&count).Error; err != nil {
				return err
			}
			if count > 0 {
				return errors.New("用户名已存在")
			}
		}
		updates := map[string]interface{}{"username": in.Username, "nickname": in.Nickname, "status": in.Status}
		if in.Password != "" {
			hash, err := bcrypt.GenerateFromPassword([]byte(in.Password), bcrypt.DefaultCost)
			if err != nil {
				return err
			}
			updates["password_hash"] = string(hash)
		}
		if err := tx.Model(&user).Updates(updates).Error; err != nil {
			return err
		}
		return tx.First(returnUser, user.ID).Error
	})
	if err != nil {
		return nil, err
	}
	return returnUser, nil
}

func (s *UserService) UpdateStatus(id uint, status int) error {
	if status != 0 && status != 1 {
		return errors.New("用户状态无效")
	}
	return s.db.Transaction(func(tx *gorm.DB) error {
		var user model.User
		if err := tx.First(&user, id).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errors.New("用户不存在")
			}
			return err
		}
		if user.Role == model.RoleAdmin && user.Status == 1 && status == 0 {
			var admins int64
			if err := tx.Model(&model.User{}).Where("role = ? AND status = ?", model.RoleAdmin, 1).Count(&admins).Error; err != nil {
				return err
			}
			if admins <= 1 {
				return errors.New("至少保留一个启用的平台管理员")
			}
		}
		return tx.Model(&user).Update("status", status).Error
	})
}

// DeletePlatformAdmin removes a platform-only account. It protects the current
// account and the final enabled platform administrator so the platform cannot be locked out.
func (s *UserService) DeletePlatformAdmin(id, actorUserID uint) error {
	if id == 0 {
		return errors.New("用户不存在")
	}
	if id == actorUserID {
		return errors.New("不能删除当前登录账号")
	}
	return s.db.Transaction(func(tx *gorm.DB) error {
		var user model.User
		if err := tx.First(&user, id).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errors.New("用户不存在")
			}
			return err
		}
		if user.Role != model.RoleAdmin {
			return errors.New("只能删除平台管理员账号")
		}
		if user.Role == model.RoleAdmin && user.Status == 1 {
			var admins int64
			if err := tx.Model(&model.User{}).Where("role = ? AND status = ?", model.RoleAdmin, 1).Count(&admins).Error; err != nil {
				return err
			}
			if admins <= 1 {
				return errors.New("至少保留一个启用的平台管理员")
			}
		}
		return tx.Delete(&user).Error
	})
}

// DeleteMerchantAccount permanently removes a merchant login account and all
// of its merchant memberships. Platform administrators must be managed from
// the dedicated platform administrator view instead.
func (s *UserService) DeleteMerchantAccount(id, actorUserID uint) error {
	if id == 0 {
		return errors.New("用户不存在")
	}
	if id == actorUserID {
		return errors.New("不能删除当前登录账号")
	}
	return s.db.Transaction(func(tx *gorm.DB) error {
		var user model.User
		if err := tx.First(&user, id).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errors.New("用户不存在")
			}
			return err
		}
		if user.Role != model.RoleMerchant {
			return errors.New("平台管理员请在平台管理员列表中管理")
		}
		if err := tx.Where("user_id = ?", user.ID).Delete(&model.MerchantMember{}).Error; err != nil {
			return err
		}
		return tx.Delete(&user).Error
	})
}