package service

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/google/uuid"
	"gorm.io/gorm"

	"github.com/wangjia/pay/config"
	"github.com/wangjia/pay/internal/channel"
	"github.com/wangjia/pay/internal/model"
	"github.com/wangjia/pay/internal/util"
)

var (
	ErrProductNotFound = errors.New("套餐不存在或已下架")
	ErrAmountMismatch  = errors.New("回调金额与订单金额不符")
)

type OrderService struct {
	db      *gorm.DB
	reg     *channel.Registry
	baseURL string
}

func NewOrderService(db *gorm.DB, reg *channel.Registry, baseURL string) *OrderService {
	return &OrderService{db: db, reg: reg, baseURL: baseURL}
}

// BizParams 业务对接下单参数（独立收款场景全空）。
type BizParams struct {
	System    string // 业务来源，如 jiu
	Ref       string // 业务引用，如 jiu 的 purchase_id
	ReturnURL string // 自定义付款后跳回地址（空则用 pay 默认结果页）
}

// prepare 校验套餐、取渠道、落库一张待支付订单（金额一律取服务端套餐价，不信任前端）。
func (s *OrderService) prepare(productID uint64, clientIP string, biz BizParams) (channel.Channel, *model.Merchant, *model.Order, error) {
	var p model.Product
	if err := s.db.First(&p, "id = ? AND active = ?", productID, true).Error; err != nil {
		return nil, nil, nil, ErrProductNotFound
	}
	ch, m, err := s.reg.ByMerchantID(p.MerchantID)
	if err != nil {
		return nil, nil, nil, err
	}
	order := &model.Order{
		OutTradeNo: util.NewOutTradeNo(m.Code),
		MerchantID: m.ID,
		Channel:    m.Channel,
		ProductID:  p.ID,
		Subject:    p.Name,
		Amount:     p.Price, // 权威金额
		Status:     model.OrderPending,
		ClientIP:   clientIP,
		BizSystem:  biz.System,
		BizRef:     biz.Ref,
	}
	if err := s.db.Create(order).Error; err != nil {
		return nil, nil, nil, fmt.Errorf("创建订单失败: %w", err)
	}
	return ch, m, order, nil
}

func (s *OrderService) notifyURL(channel string) string {
	return s.baseURL + "/api/v1/notify/" + channel
}

// returnURL 付款后同步跳转地址：业务方传了自定义地址就用它（拼上 out_trade_no），否则用 pay 默认结果页。
func (s *OrderService) returnURL(custom, outTradeNo string) string {
	if custom == "" {
		return s.baseURL + "/result?out_trade_no=" + outTradeNo
	}
	sep := "?"
	if strings.Contains(custom, "?") {
		sep = "&"
	}
	return custom + sep + "out_trade_no=" + outTradeNo
}

// Create 网页支付下单，返回收银台跳转 URL。isMobile=true 时支付宝走手机网站支付(拉起 App)。
func (s *OrderService) Create(ctx context.Context, productID uint64, clientIP string, isMobile bool, biz BizParams) (string, *model.Order, error) {
	ch, m, order, err := s.prepare(productID, clientIP, biz)
	if err != nil {
		return "", nil, err
	}
	payURL, err := ch.PagePay(ctx, channel.CreateReq{
		OutTradeNo: order.OutTradeNo,
		Subject:    order.Subject,
		Amount:     order.Amount,
		NotifyURL:  s.notifyURL(m.Channel),
		ReturnURL:  s.returnURL(biz.ReturnURL, order.OutTradeNo),
		IsMobile:   isMobile,
	})
	if err != nil {
		return "", nil, err
	}
	return payURL, order, nil
}

// CreateQR 扫码（当面付）下单，返回二维码码串供前端渲染。
func (s *OrderService) CreateQR(ctx context.Context, productID uint64, clientIP string) (string, *model.Order, error) {
	ch, m, order, err := s.prepare(productID, clientIP, BizParams{})
	if err != nil {
		return "", nil, err
	}
	qr, err := ch.PreCreate(ctx, channel.CreateReq{
		OutTradeNo: order.OutTradeNo,
		Subject:    order.Subject,
		Amount:     order.Amount,
		NotifyURL:  s.notifyURL(m.Channel),
	})
	if err != nil {
		return "", nil, err
	}
	return qr, order, nil
}

// HandleAlipayNotify 处理支付宝异步回调：反查商户 → 验签 → 核对金额 → 幂等更新。
// 返回 nil 表示已正确处理（调用方应给支付宝回 "success"）。
func (s *OrderService) HandleAlipayNotify(ctx context.Context, r *http.Request) error {
	if err := r.ParseForm(); err != nil {
		return fmt.Errorf("解析回调失败: %w", err)
	}
	appID := r.PostFormValue("app_id")
	outTradeNo := r.PostFormValue("out_trade_no")

	ch, m, err := s.reg.AlipayByAppID(appID)
	if err != nil {
		s.logNotify("alipay", outTradeNo, false, "not_found", r.Form.Encode())
		return err
	}

	res, err := ch.VerifyNotify(ctx, r)
	if err != nil {
		s.logNotify("alipay", outTradeNo, false, "verify_failed", r.Form.Encode())
		return err
	}

	result, err := s.applyPaid(m, res)
	s.logNotify("alipay", res.OutTradeNo, true, result, res.Raw)
	return err
}

// HandleWechatNotify 处理微信异步回调：解密验签 → 按 out_trade_no 定位订单/商户 → 核对金额 → 幂等更新。
// 微信回调正文加密且不含明文商户路由信息，故先用任一启用的微信商户凭证解密（同主体共用），
// 再按解密出的 out_trade_no 找到订单实际归属的商户入账。返回 nil 表示已正确处理。
func (s *OrderService) HandleWechatNotify(ctx context.Context, r *http.Request) error {
	ch, _, err := s.reg.FirstWechat()
	if err != nil {
		s.logNotify("wechat", "", false, "no_merchant", "")
		return err
	}

	res, err := ch.VerifyNotify(ctx, r)
	if err != nil {
		s.logNotify("wechat", "", false, "verify_failed", "")
		return err
	}

	var o model.Order
	if err := s.db.First(&o, "out_trade_no = ?", res.OutTradeNo).Error; err != nil {
		s.logNotify("wechat", res.OutTradeNo, true, "not_found", res.Raw)
		return fmt.Errorf("订单不存在: %s", res.OutTradeNo)
	}
	var m model.Merchant
	if err := s.db.First(&m, o.MerchantID).Error; err != nil {
		s.logNotify("wechat", res.OutTradeNo, true, "merchant_not_found", res.Raw)
		return fmt.Errorf("订单 %s 的商户不存在: %w", res.OutTradeNo, err)
	}

	result, err := s.applyPaid(&m, res)
	s.logNotify("wechat", res.OutTradeNo, true, result, res.Raw)
	return err
}

// applyPaid 在一个事务里完成「金额核对 + 幂等置为已支付」。返回处理结果标记。
func (s *OrderService) applyPaid(m *model.Merchant, res *channel.NotifyResult) (string, error) {
	if !res.Paid {
		return "ignored", nil // 非成功状态（如 WAIT_BUYER_PAY），确认收到即可
	}

	var resultTag string
	err := s.db.Transaction(func(tx *gorm.DB) error {
		var o model.Order
		if err := tx.First(&o, "out_trade_no = ? AND merchant_id = ?", res.OutTradeNo, m.ID).Error; err != nil {
			resultTag = "not_found"
			return fmt.Errorf("订单不存在: %s", res.OutTradeNo)
		}
		if o.Status == model.OrderPaid {
			resultTag = "duplicate" // 幂等：已处理过，直接成功返回
			return nil
		}
		if !util.AmountEqual(o.Amount, res.Amount) {
			resultTag = "amount_mismatch"
			return ErrAmountMismatch
		}
		now := time.Now()
		upd := tx.Model(&model.Order{}).
			Where("out_trade_no = ? AND status = ?", o.OutTradeNo, model.OrderPending).
			Updates(map[string]any{
				"status":         model.OrderPaid,
				"trade_no":       res.TradeNo,
				"buyer_logon_id": res.BuyerLogonID,
				"paid_at":        &now,
			})
		if upd.Error != nil {
			return upd.Error
		}
		if upd.RowsAffected == 0 {
			resultTag = "duplicate" // 并发下被另一路（如查单）先置位
			return nil
		}
		resultTag = "processed"
		log.Printf("[notify] 订单 %s 已支付 trade_no=%s amount=%s", o.OutTradeNo, res.TradeNo, res.Amount)
		return nil
	})
	// 新入账成功且属业务对接单：异步回调业务系统 webhook（失败由后台重试兜底，不阻塞支付回调响应）。
	if err == nil && resultTag == "processed" {
		go s.notifyBizByOutTradeNo(res.OutTradeNo)
	}
	return resultTag, err
}

func (s *OrderService) logNotify(ch, outTradeNo string, verified bool, result, raw string) {
	_ = s.db.Create(&model.NotifyLog{
		Channel:    ch,
		OutTradeNo: outTradeNo,
		Verified:   verified,
		Result:     result,
		Raw:        raw,
	}).Error
}

// GetByOutTradeNo 供前端结果页轮询。
func (s *OrderService) GetByOutTradeNo(outTradeNo string) (*model.Order, error) {
	var o model.Order
	if err := s.db.First(&o, "out_trade_no = ?", outTradeNo).Error; err != nil {
		return nil, err
	}
	return &o, nil
}

// SyncPending 兜底：把近期待支付订单拿去主动查单，命中已支付则补记（防回调丢失）。
func (s *OrderService) SyncPending(ctx context.Context, maxAge time.Duration) {
	// 后台循环调用；恢复 panic 防止拖垮整个进程。
	defer func() {
		if r := recover(); r != nil {
			log.Printf("[query_sync] 发生 panic 已恢复: %v", r)
		}
	}()

	var orders []model.Order
	cutoff := time.Now().Add(-maxAge)
	if err := s.db.Where("status = ? AND created_at > ?", model.OrderPending, cutoff).
		Limit(100).Find(&orders).Error; err != nil {
		log.Printf("[query_sync] 查询待支付订单失败: %v", err)
		return
	}
	for i := range orders {
		o := &orders[i]
		ch, m, err := s.reg.ByMerchantID(o.MerchantID)
		if err != nil {
			continue
		}
		qr, err := ch.Query(ctx, o.OutTradeNo)
		if err != nil || qr == nil || !qr.Found || !qr.Paid {
			continue
		}
		result, _ := s.applyPaid(m, &channel.NotifyResult{
			OutTradeNo: qr.OutTradeNo,
			TradeNo:    qr.TradeNo,
			Amount:     qr.Amount,
			Paid:       true,
		})
		if result == "processed" {
			log.Printf("[query_sync] 订单 %s 经主动查单补记为已支付", o.OutTradeNo)
		}
	}
}

// StartQuerySync 启动后台查单兜底循环。
func (s *OrderService) StartQuerySync(interval, maxAge time.Duration) {
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		for range ticker.C {
			s.SyncPending(context.Background(), maxAge)
		}
	}()
}

// notifyBizByOutTradeNo 向业务系统推送「支付成功」webhook（签名）。成功则置 BizNotified，失败留待重试。
func (s *OrderService) notifyBizByOutTradeNo(outTradeNo string) {
	// 该函数在 goroutine 中运行（applyPaid 异步触发 + 重试循环）；Go 中未恢复的 goroutine panic 会整进程崩溃。
	defer func() {
		if r := recover(); r != nil {
			log.Printf("[biz_notify] 订单 %s 回调发生 panic 已恢复: %v", outTradeNo, r)
		}
	}()

	var o model.Order
	if err := s.db.First(&o, "out_trade_no = ?", outTradeNo).Error; err != nil {
		return
	}
	if o.BizSystem == "" || o.BizNotified || o.Status != model.OrderPaid {
		return
	}
	cfg, ok := config.C.BizByName(o.BizSystem)
	if !ok {
		log.Printf("[biz_notify] 订单 %s 业务系统 %s 未配置回调，跳过", o.OutTradeNo, o.BizSystem)
		return
	}

	var p model.Product
	_ = s.db.First(&p, o.ProductID).Error // 取 biz_code；失败则为空

	paidAt := ""
	if o.PaidAt != nil {
		paidAt = o.PaidAt.Format(time.RFC3339)
	}
	body, _ := json.Marshal(map[string]any{
		"out_trade_no":     o.OutTradeNo,
		"biz_system":       o.BizSystem,
		"biz_ref":          o.BizRef,
		"product_biz_code": p.BizCode,
		"amount":           o.Amount,
		"trade_no":         o.TradeNo,
		"channel":          o.Channel,
		"paid_at":          paidAt,
	})

	ts := strconv.FormatInt(time.Now().Unix(), 10)
	nonce := uuid.NewString()
	sign := util.HMACSign(cfg.Secret, o.BizSystem, ts, nonce, string(body))

	req, err := http.NewRequest(http.MethodPost, cfg.CallbackURL, bytes.NewReader(body))
	if err != nil {
		log.Printf("[biz_notify] 订单 %s 构造回调请求失败: %v", o.OutTradeNo, err)
		return
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("X-Pay-System", o.BizSystem)
	req.Header.Set("X-Pay-Timestamp", ts)
	req.Header.Set("X-Pay-Nonce", nonce)
	req.Header.Set("X-Pay-Sign", sign)

	entry := &model.BizNotifyLog{OutTradeNo: o.OutTradeNo, BizSystem: o.BizSystem, URL: cfg.CallbackURL, Payload: string(body)}
	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	success := false
	if err != nil {
		entry.RespBody = err.Error()
	} else {
		rb, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		resp.Body.Close()
		entry.RespCode = resp.StatusCode
		entry.RespBody = string(rb)
		// 约定：业务方返回 HTTP 200 且响应含 SUCCESS 视为受理成功。
		if resp.StatusCode == http.StatusOK && strings.Contains(strings.ToUpper(string(rb)), "SUCCESS") {
			success = true
		}
	}
	entry.OK = success
	_ = s.db.Create(entry).Error

	if success {
		s.db.Model(&model.Order{}).Where("out_trade_no = ?", o.OutTradeNo).Update("biz_notified", true)
		log.Printf("[biz_notify] 订单 %s 已成功回调 %s", o.OutTradeNo, o.BizSystem)
	} else {
		log.Printf("[biz_notify] 订单 %s 回调 %s 失败(code=%d)，等待重试", o.OutTradeNo, o.BizSystem, entry.RespCode)
	}
}

// NotifyBizPending 兜底重试：把已支付但未成功回调业务方的订单再推一次。
func (s *OrderService) NotifyBizPending() {
	var orders []model.Order
	cutoff := time.Now().Add(-24 * time.Hour)
	if err := s.db.Where("status = ? AND biz_system <> '' AND biz_notified = ? AND created_at > ?",
		model.OrderPaid, false, cutoff).Limit(50).Find(&orders).Error; err != nil {
		log.Printf("[biz_notify] 查询待回调订单失败: %v", err)
		return
	}
	for i := range orders {
		s.notifyBizByOutTradeNo(orders[i].OutTradeNo)
	}
}

// StartBizNotifyRetry 启动业务回调重试循环（兜底 webhook 丢失/业务方短暂不可用）。
func (s *OrderService) StartBizNotifyRetry(interval time.Duration) {
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		for range ticker.C {
			s.NotifyBizPending()
		}
	}()
}