package service

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"affiliate_dash/internal/model"
	"affiliate_dash/internal/pkg/timeutil"
	"gorm.io/gorm"
)

func (s *DeliveryService) authorizeDeliveryLink(order *model.FulfillmentOrder, auth DeliveryLinkAuth) error {
	if order == nil {
		return newDeliveryHTTPError(http.StatusNotFound, "订单不存在")
	}
	if strings.TrimSpace(auth.Sign) == "" {
		return newDeliveryHTTPError(http.StatusForbidden, "链接参数缺失")
	}
	if order.DeliveryLinkRevokedAt != nil {
		return newDeliveryHTTPError(http.StatusForbidden, "发货链接已作废")
	}
	// 订单已取消后链接立即失效，防止已退款订单仍通过链接查看或继续发货。
	if normalizeOrderStatus(order) == model.OrderStatusCancelled {
		return newDeliveryHTTPError(http.StatusForbidden, "订单已取消，发货链接不可用")
	}
	// 从未生成过链接（兼容历史数据：本次改动前生成的有时效链接没有 generated_at 记录）。
	if order.DeliveryLinkGeneratedAt == nil && order.DeliveryLinkExpiresAt == nil {
		return newDeliveryHTTPError(http.StatusForbidden, "发货链接未生成")
	}
	// 永久有效链接（expires_at 为 NULL）：仅校验签名（exp 固定为 0），不检查过期。
	if order.DeliveryLinkExpiresAt == nil {
		expected := s.signDeliveryLink(order.OrderNo, auth.Exp)
		if !hmac.Equal([]byte(strings.ToLower(strings.TrimSpace(auth.Sign))), []byte(expected)) {
			return newDeliveryHTTPError(http.StatusForbidden, "发货链接签名无效")
		}
		return nil
	}
	expiresAt := order.DeliveryLinkExpiresAt.UTC().Truncate(time.Second)
	linkExpires := time.Unix(auth.Exp, 0).UTC()
	if !linkExpires.Equal(expiresAt) {
		return newDeliveryHTTPError(http.StatusForbidden, "发货链接已失效")
	}
	if time.Now().UTC().After(linkExpires) {
		return newDeliveryHTTPError(http.StatusForbidden, "发货链接已过期")
	}
	expected := s.signDeliveryLink(order.OrderNo, auth.Exp)
	if !hmac.Equal([]byte(strings.ToLower(strings.TrimSpace(auth.Sign))), []byte(expected)) {
		return newDeliveryHTTPError(http.StatusForbidden, "发货链接签名无效")
	}
	return nil
}

// buildDeliveryLinkResult 组装链接结果；expiresAt 为 nil 表示永久有效（exp 固定为 0）。
func (s *DeliveryService) buildDeliveryLinkResult(orderNo string, expiresAt *time.Time, requestBaseURL string) *DeliveryLinkResult {
	exp := int64(0)
	if expiresAt != nil {
		exp = expiresAt.UTC().Unix()
	}
	sign := s.signDeliveryLink(orderNo, exp)
	return &DeliveryLinkResult{
		OrderNo:     orderNo,
		DeliveryURL: s.buildDeliveryURL(orderNo, exp, sign, requestBaseURL),
		ExpiresAt:   expiresAt,
		Exp:         exp,
		Sign:        sign,
	}
}

func (s *DeliveryService) buildDeliveryURL(orderNo string, exp int64, sign, requestBaseURL string) string {
	path := fmt.Sprintf("/delivery/%s/%s?exp=%d&sign=%s", url.PathEscape(s.channel), url.PathEscape(orderNo), exp, url.QueryEscape(sign))
	base := strings.TrimRight(s.linkBaseURL, "/")
	if base == "" {
		base = strings.TrimRight(requestBaseURL, "/")
	}
	if base == "" {
		return path
	}
	return base + path
}

func (s *DeliveryService) signDeliveryLink(orderNo string, exp int64) string {
	mac := hmac.New(sha256.New, []byte(s.linkSecret))
	_, _ = mac.Write([]byte(orderNo + "|" + strconv.FormatInt(exp, 10)))
	return hex.EncodeToString(mac.Sum(nil))
}

func (s *DeliveryService) GetOrCreateDeliveryLink(merchantID uint, orderNo, requestBaseURL string) (*DeliveryLinkResult, error) {
	orderNo = strings.TrimSpace(orderNo)
	if orderNo == "" {
		return nil, errors.New("订单号不能为空")
	}
	order, err := s.fulfillment.GetOrder(merchantID, orderNo)
	if err != nil {
		return nil, err
	}
	// 已取消订单即使存在未过期链接也不再发放（买家侧授权同样拦截已取消订单）。
	if normalizeOrderStatus(order) == model.OrderStatusCancelled {
		return nil, newDeliveryHTTPError(http.StatusBadRequest, "订单已取消，无法获取发货链接")
	}
	now := time.Now().UTC()
	if order.DeliveryLinkRevokedAt != nil {
		return nil, newDeliveryHTTPError(http.StatusForbidden, "发货链接已作废")
	}
	// 复用未过期链接：已交付/发货中订单也允许查看兑换结果或进度，仅停止发放新链接。
	if order.DeliveryLinkExpiresAt != nil && order.DeliveryLinkExpiresAt.After(now) {
		expiresAt := order.DeliveryLinkExpiresAt.UTC().Truncate(time.Second)
		return s.buildDeliveryLinkResult(order.OrderNo, &expiresAt, requestBaseURL), nil
	}
	// 永久有效链接（已生成、未作废、无有效期）直接复用，不重复生成。
	if order.DeliveryLinkGeneratedAt != nil && order.DeliveryLinkExpiresAt == nil {
		return s.buildDeliveryLinkResult(order.OrderNo, nil, requestBaseURL), nil
	}
	// 仅待发货（含可重试的发货失败）订单能生成或续期新链接。
	canShip, reason := CanFulfill(order)
	if !canShip {
		if reason == "" {
			reason = "订单暂不可发货"
		}
		return nil, newDeliveryHTTPError(http.StatusBadRequest, reason)
	}
	var expiresAt *time.Time
	if s.linkTTL > 0 {
		value := now.Add(s.linkTTL).UTC().Truncate(time.Second)
		expiresAt = &value
	}
	if err := s.fulfillment.db.Model(&model.FulfillmentOrder{}).
		Where("id = ?", order.ID).
		Updates(map[string]interface{}{
			"delivery_link_expires_at":   expiresAt,
			"delivery_link_revoked_at":   nil,
			"delivery_link_generated_at": now,
		}).Error; err != nil {
		return nil, err
	}
	return s.buildDeliveryLinkResult(order.OrderNo, expiresAt, requestBaseURL), nil
}

func (s *DeliveryService) RevokeDeliveryLink(merchantID, actorUserID uint, orderNo string) error {
	orderNo = strings.TrimSpace(orderNo)
	if orderNo == "" {
		return errors.New("订单号不能为空")
	}
	order, err := s.fulfillment.GetOrder(merchantID, orderNo)
	if err != nil {
		return err
	}
	now := time.Now().UTC().Truncate(time.Second)
	return s.fulfillment.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Model(&model.FulfillmentOrder{}).
			Where("id = ?", order.ID).
			Updates(map[string]interface{}{
				"delivery_link_revoked_at": now,
			}).Error; err != nil {
			return err
		}
		return writeAudit(tx, &merchantID, optionalUint(actorUserID), nil, "delivery_link.revoke", "fulfillment_order", order.OrderNo, map[string]interface{}{
			"revoked_at": timeutil.FormatAPITime(now),
		})
	})
}

func (s *DeliveryService) RestoreDeliveryLink(merchantID, actorUserID uint, orderNo, requestBaseURL string) (*DeliveryLinkResult, error) {
	orderNo = strings.TrimSpace(orderNo)
	if orderNo == "" {
		return nil, errors.New("订单号不能为空")
	}
	order, err := s.fulfillment.GetOrder(merchantID, orderNo)
	if err != nil {
		return nil, err
	}
	canShip, reason := CanFulfill(order)
	if !canShip {
		if reason == "" {
			reason = "订单暂不可发货"
		}
		return nil, newDeliveryHTTPError(http.StatusBadRequest, reason)
	}
	now := time.Now().UTC()
	var expiresAt *time.Time
	if s.linkTTL > 0 {
		value := now.Add(s.linkTTL).Truncate(time.Second)
		if order.DeliveryLinkExpiresAt != nil && value.Equal(order.DeliveryLinkExpiresAt.UTC().Truncate(time.Second)) {
			value = value.Add(time.Second)
		}
		expiresAt = &value
	}
	if err := s.fulfillment.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Model(&model.FulfillmentOrder{}).
			Where("id = ?", order.ID).
			Updates(map[string]interface{}{
				"delivery_link_expires_at":   expiresAt,
				"delivery_link_revoked_at":   nil,
				"delivery_link_generated_at": now,
			}).Error; err != nil {
			return err
		}
		metadata := map[string]interface{}{
			"generated_at": timeutil.FormatAPITime(now),
		}
		if expiresAt != nil {
			metadata["expires_at"] = timeutil.FormatAPITime(*expiresAt)
		} else {
			metadata["permanent"] = true
		}
		return writeAudit(tx, &merchantID, optionalUint(actorUserID), nil, "delivery_link.restore", "fulfillment_order", order.OrderNo, metadata)
	}); err != nil {
		return nil, err
	}
	return s.buildDeliveryLinkResult(order.OrderNo, expiresAt, requestBaseURL), nil
}