package service

import (
	"errors"
	"fmt"
	"regexp"
	"strings"

	"affiliate_dash/internal/model"

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

var merchantCodePattern = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{2,63}$`)

type MerchantService struct {
	db     *gorm.DB
	codec  *SecretCodec
	tenant *TenantService
}

func NewMerchantService(db *gorm.DB, codec *SecretCodec, tenant *TenantService) *MerchantService {
	return &MerchantService{db: db, codec: codec, tenant: tenant}
}

type CreateMerchantInput struct {
	Code           string
	Name           string
	ContactName    string
	ContactInfo    string
	OwnerUserID    uint
	OwnerUsername  string
	OwnerPassword  string
	OwnerNickname  string
	Features       string
	FeeType        string
	FeeRateBP      int64
	FeeFixedAmount int64
}

func (s *MerchantService) CreateMerchant(in CreateMerchantInput, actorUserID uint) (*model.Merchant, error) {
	in.Code = strings.ToLower(strings.TrimSpace(in.Code))
	in.Name = strings.TrimSpace(in.Name)
	in.Features = NormalizeMerchantFeatures(in.Features)
	if !merchantCodePattern.MatchString(in.Code) {
		return nil, errors.New("商户编码需为 3-64 位小写字母、数字或连字符")
	}
	if in.Name == "" {
		return nil, errors.New("商户名称不能为空")
	}
	if in.OwnerUserID == 0 && strings.TrimSpace(in.OwnerUsername) == "" {
		return nil, errors.New("商户负责人不能为空")
	}
	if in.FeeRateBP < 0 || in.FeeRateBP > 10000 {
		return nil, errors.New("手续费比例需在 0-10000 BP 之间")
	}
	if in.FeeFixedAmount < 0 {
		return nil, errors.New("固定手续费不能小于零")
	}
	feeType := in.FeeType
	if feeType == "" {
		feeType = model.FeeTypeRate
	}
	if feeType != model.FeeTypeRate && feeType != model.FeeTypeFixed {
		return nil, errors.New("手续费类型仅支持 rate 或 fixed")
	}
	merchant := &model.Merchant{
		Code:           in.Code,
		Name:           in.Name,
		Status:         model.MerchantStatusActive,
		ContactName:    in.ContactName,
		ContactInfo:    in.ContactInfo,
		Features:       in.Features,
		FeeType:        feeType,
		FeeRateBP:      in.FeeRateBP,
		FeeFixedAmount: in.FeeFixedAmount,
	}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		owner, err := s.resolveOrCreateOwner(tx, in)
		if err != nil {
			return err
		}
		if owner.Status != 1 {
			return errors.New("商户负责人已禁用")
		}
		if err := tx.Create(merchant).Error; err != nil {
			return err
		}
		if err := tx.Create(&model.WalletAccount{MerchantID: merchant.ID, Currency: "POINT"}).Error; err != nil {
			return err
		}
		if err := tx.Create(&model.MerchantMember{
			MerchantID: merchant.ID,
			UserID:     owner.ID,
			Role:       model.MemberRoleOwner,
			Status:     1,
			IsDefault:  true,
		}).Error; err != nil {
			return err
		}
		if err := copyDefaultProducts(tx, merchant.ID); err != nil {
			return err
		}
		return writeAudit(tx, &merchant.ID, &actorUserID, nil, "merchant.create", "merchant", fmt.Sprint(merchant.ID), map[string]string{"code": merchant.Code})
	})
	if err != nil {
		return nil, err
	}
	return merchant, nil
}

func (s *MerchantService) resolveOrCreateOwner(tx *gorm.DB, in CreateMerchantInput) (*model.User, error) {
	if in.OwnerUserID != 0 {
		var owner model.User
		if err := tx.First(&owner, in.OwnerUserID).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return nil, errors.New("商户负责人不存在")
			}
			return nil, err
		}
		return &owner, nil
	}
	username := strings.TrimSpace(in.OwnerUsername)
	password := strings.TrimSpace(in.OwnerPassword)
	nickname := strings.TrimSpace(in.OwnerNickname)
	if username == "" || len(username) < 3 {
		return nil, errors.New("负责人用户名至少 3 位")
	}
	if len(password) < 6 {
		return nil, errors.New("负责人密码至少 6 位")
	}
	if nickname == "" {
		nickname = username
	}
	var count int64
	if err := tx.Model(&model.User{}).Where("username = ?", username).Count(&count).Error; err != nil {
		return nil, err
	}
	if count > 0 {
		return nil, errors.New("负责人用户名已存在")
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return nil, err
	}
	owner := &model.User{
		Username:     username,
		PasswordHash: string(hash),
		Nickname:     nickname,
		Role:         model.RoleMerchant,
		Status:       1,
	}
	if err := tx.Create(owner).Error; err != nil {
		return nil, err
	}
	return owner, nil
}

type UpdateMerchantSettingsInput struct {
	Name           *string
	Status         *string
	ContactName    *string
	ContactInfo    *string
	Features       *string
	FeeType        *string
	FeeRateBP      *int64
	FeeFixedAmount *int64
}

func (s *MerchantService) UpdateMerchantSettings(merchantID uint, in UpdateMerchantSettingsInput, actorUserID uint) error {
	updates := map[string]interface{}{}
	if in.Name != nil {
		name := strings.TrimSpace(*in.Name)
		if name == "" {
			return errors.New("商户名称不能为空")
		}
		updates["name"] = name
	}
	if in.Status != nil {
		if *in.Status != model.MerchantStatusActive && *in.Status != model.MerchantStatusDisabled {
			return errors.New("无效的商户状态")
		}
		updates["status"] = *in.Status
	}
	if in.ContactName != nil {
		updates["contact_name"] = strings.TrimSpace(*in.ContactName)
	}
	if in.ContactInfo != nil {
		updates["contact_info"] = strings.TrimSpace(*in.ContactInfo)
	}
	if in.Features != nil {
		updates["features"] = NormalizeMerchantFeatures(*in.Features)
	}
	if in.FeeRateBP != nil {
		if *in.FeeRateBP < 0 || *in.FeeRateBP > 10000 {
			return errors.New("手续费比例需在 0-10000 BP 之间")
		}
		updates["fee_rate_bp"] = *in.FeeRateBP
	}
	if in.FeeFixedAmount != nil {
		if *in.FeeFixedAmount < 0 {
			return errors.New("固定手续费不能小于零")
		}
		updates["fee_fixed_amount"] = *in.FeeFixedAmount
	}
	if in.FeeType != nil {
		if *in.FeeType != model.FeeTypeRate && *in.FeeType != model.FeeTypeFixed {
			return errors.New("手续费类型仅支持 rate 或 fixed")
		}
		updates["fee_type"] = *in.FeeType
	}
	if len(updates) == 0 {
		return errors.New("没有可更新字段")
	}
	return s.db.Transaction(func(tx *gorm.DB) error {
		result := tx.Model(&model.Merchant{}).Where("id = ?", merchantID).Updates(updates)
		if result.Error != nil {
			return result.Error
		}
		if result.RowsAffected == 0 {
			return errors.New("商户不存在")
		}
		return writeAudit(tx, &merchantID, &actorUserID, nil, "merchant.settings.update", "merchant", fmt.Sprint(merchantID), updates)
	})
}

func (s *MerchantService) ListMerchants(page, size int) ([]model.Merchant, int64, error) {
	page, size = normalizePage(page, size)
	tx := s.db.Model(&model.Merchant{})
	var total int64
	if err := tx.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var merchants []model.Merchant
	err := tx.Order("id DESC").Offset((page - 1) * size).Limit(size).Find(&merchants).Error
	return merchants, total, err
}

func (s *MerchantService) GetMerchant(merchantID uint) (*model.Merchant, error) {
	var merchant model.Merchant
	if err := s.db.First(&merchant, merchantID).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("商户不存在")
		}
		return nil, err
	}
	return &merchant, nil
}