package service

import (
	"database/sql"
	"errors"
	"fmt"
	"strings"
	"time"

	"cmautobuy/admin/model"
	"cmautobuy/admin/repository"
)

const maxShopNameLength = 500

type ShopListResult struct {
	Items               []model.Shop
	UnlinkedShopeeCount int
}

func ListShops(db *sql.DB, actor *model.User) (ShopListResult, error) {
	if actor == nil || !actor.IsAdmin() {
		return ShopListResult{}, ErrAdminRequired
	}
	items, err := repository.ListShops(db)
	if err != nil {
		return ShopListResult{}, err
	}
	unlinked, err := repository.CountUnlinkedShopeeShops(db)
	if err != nil {
		return ShopListResult{}, err
	}
	return ShopListResult{Items: items, UnlinkedShopeeCount: unlinked}, nil
}

func CreateShop(db *sql.DB, actor *model.User, shopName string, now time.Time) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	shopName, err := validateShopName(shopName)
	if err != nil {
		return err
	}
	shopID, err := randomID("SHOP-", 16)
	if err != nil {
		return fmt.Errorf("生成店铺编号失败: %w", err)
	}
	at := now.UTC().Format(model.TimeLayout)
	tx, err := db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	if err := repository.InsertShop(tx, model.Shop{ShopID: shopID, DisplayName: shopName,
		NormalizedName: shopName, Enabled: true, CreatedByUserID: actor.UserID, CreatedAt: at, UpdatedAt: at}); err != nil {
		return shopValidationError(err)
	}
	if err := insertShopAlias(tx, shopID, "syb", shopName, true, at); err != nil {
		return shopValidationError(err)
	}
	if err := insertShopAlias(tx, shopID, "shopee", shopName, true, at); err != nil {
		return shopValidationError(err)
	}
	if err := repository.RebuildShopAssociations(tx, shopID); err != nil {
		return err
	}
	return tx.Commit()
}

func UpdateShop(db *sql.DB, actor *model.User, shopID, shopName string, now time.Time) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	shopID = strings.TrimSpace(shopID)
	if shopID == "" {
		return &validationError{field: "shop_id", message: "店铺编号不能为空"}
	}
	shopName, err := validateShopName(shopName)
	if err != nil {
		return err
	}
	at := now.UTC().Format(model.TimeLayout)
	tx, err := db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	shop, found, err := repository.GetShop(tx, shopID)
	if err != nil {
		return err
	} else if !found {
		return &validationError{field: "shop_id", message: "店铺不存在，请刷新页面后重试"}
	}
	if _, err := repository.UpdateShopName(tx, shopID, shopName, shopName, at); err != nil {
		return shopValidationError(err)
	}
	if err := replaceShopAlias(tx, shopID, "syb", shopName, shop.Enabled, at); err != nil {
		return shopValidationError(err)
	}
	if err := replaceShopAlias(tx, shopID, "shopee", shopName, shop.Enabled, at); err != nil {
		return shopValidationError(err)
	}
	if err := repository.RebuildShopAssociations(tx, shopID); err != nil {
		return err
	}
	return tx.Commit()
}

func SetShopEnabled(db *sql.DB, actor *model.User, shopID string, enabled bool, now time.Time) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	shopID = strings.TrimSpace(shopID)
	at := now.UTC().Format(model.TimeLayout)
	tx, err := db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	found, err := repository.SetShopEnabled(tx, shopID, enabled, at)
	if err != nil {
		return err
	}
	if !found {
		return &validationError{field: "shop_id", message: "店铺不存在，请刷新页面后重试"}
	}
	if err := repository.SetShopCompatibilityAliasesEnabled(tx, shopID, enabled, at); err != nil {
		return err
	}
	return tx.Commit()
}

func DeleteShop(db *sql.DB, actor *model.User, shopID string) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	deleted, err := repository.DeleteDisabledShop(db, strings.TrimSpace(shopID))
	if errors.Is(err, repository.ErrShopHasReferences) {
		return &validationError{field: "shop_id", message: "店铺仍有关联数据，只能保留为停用状态"}
	}
	if err != nil {
		return err
	}
	if !deleted {
		return &validationError{field: "shop_id", message: "店铺不存在或仍在启用，请先停用"}
	}
	return nil
}

func validateShopName(shopName string) (string, error) {
	shopName = strings.TrimSpace(shopName)
	if shopName == "" {
		return "", &validationError{field: "shop_name", message: "店铺名称不能为空"}
	}
	if len([]rune(shopName)) > maxShopNameLength {
		return "", &validationError{field: "shop_name", message: "店铺名称最多 500 个字符"}
	}
	return shopName, nil
}

func insertShopAlias(q repository.Execer, shopID, channel, alias string, enabled bool, at string) error {
	if alias == "" {
		return nil
	}
	aliasID, err := randomID("ALIAS-", 16)
	if err != nil {
		return err
	}
	return repository.InsertShopAlias(q, model.ShopChannelAlias{AliasID: aliasID, ShopID: shopID,
		Channel: channel, AliasName: alias, NormalizedAlias: alias, Enabled: enabled, CreatedAt: at, UpdatedAt: at})
}

func replaceShopAlias(q repository.Execer, shopID, channel, alias string, enabled bool, at string) error {
	aliasID, err := randomID("ALIAS-", 16)
	if err != nil {
		return err
	}
	return repository.ReplaceShopAlias(q, aliasID, shopID, channel, alias, at, enabled)
}

func shopValidationError(err error) error {
	switch {
	case errors.Is(err, repository.ErrShopNameExists):
		return &validationError{field: "shop_name", message: "店铺名称已经存在"}
	case errors.Is(err, repository.ErrShopAliasExists):
		return &validationError{field: "shop_name", message: "店铺名称已经存在"}
	default:
		return err
	}
}