feat(payment): add complete payment system with multi-provider support

Add a full payment and subscription system supporting EasyPay (Alipay/WeChat),
Stripe, and direct Alipay/WeChat Pay providers with multi-instance load balancing.

backend/internal/service/payment_stats.go

@@ -0,0 +1,163 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"log/slog"
+	"math"
+	"sort"
+	"strconv"
+	"time"
+
+	dbent "github.com/Wei-Shaw/sub2api/ent"
+	"github.com/Wei-Shaw/sub2api/ent/paymentauditlog"
+	"github.com/Wei-Shaw/sub2api/ent/paymentorder"
+)
+
+// --- Dashboard & Analytics ---
+
+func (s *PaymentService) GetDashboardStats(ctx context.Context, days int) (*DashboardStats, error) {
+	if days <= 0 {
+		days = 30
+	}
+	now := time.Now()
+	since := now.AddDate(0, 0, -days)
+	todayStart := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
+
+	paidStatuses := []string{OrderStatusCompleted, OrderStatusPaid, OrderStatusRecharging}
+
+	orders, err := s.entClient.PaymentOrder.Query().
+		Where(
+			paymentorder.StatusIn(paidStatuses...),
+			paymentorder.PaidAtGTE(since),
+		).
+		All(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	st := &DashboardStats{}
+	computeBasicStats(st, orders, todayStart)
+
+	st.PendingOrders, err = s.entClient.PaymentOrder.Query().
+		Where(paymentorder.StatusEQ(OrderStatusPending)).
+		Count(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	st.DailySeries = buildDailySeries(orders, since, days)
+	st.PaymentMethods = buildMethodDistribution(orders)
+	st.TopUsers = buildTopUsers(orders)
+
+	return st, nil
+}
+
+func computeBasicStats(st *DashboardStats, orders []*dbent.PaymentOrder, todayStart time.Time) {
+	var totalAmount, todayAmount float64
+	var todayCount int
+	for _, o := range orders {
+		totalAmount += o.PayAmount
+		if o.PaidAt != nil && !o.PaidAt.Before(todayStart) {
+			todayAmount += o.PayAmount
+			todayCount++
+		}
+	}
+	st.TotalAmount = math.Round(totalAmount*100) / 100
+	st.TodayAmount = math.Round(todayAmount*100) / 100
+	st.TotalCount = len(orders)
+	st.TodayCount = todayCount
+	if st.TotalCount > 0 {
+		st.AvgAmount = math.Round(totalAmount/float64(st.TotalCount)*100) / 100
+	}
+}
+
+func buildDailySeries(orders []*dbent.PaymentOrder, since time.Time, days int) []DailyStats {
+	dailyMap := make(map[string]*DailyStats)
+	for _, o := range orders {
+		if o.PaidAt == nil {
+			continue
+		}
+		date := o.PaidAt.Format("2006-01-02")
+		ds, ok := dailyMap[date]
+		if !ok {
+			ds = &DailyStats{Date: date}
+			dailyMap[date] = ds
+		}
+		ds.Amount += o.PayAmount
+		ds.Count++
+	}
+	series := make([]DailyStats, 0, days)
+	for i := 0; i < days; i++ {
+		date := since.AddDate(0, 0, i+1).Format("2006-01-02")
+		if ds, ok := dailyMap[date]; ok {
+			ds.Amount = math.Round(ds.Amount*100) / 100
+			series = append(series, *ds)
+		} else {
+			series = append(series, DailyStats{Date: date})
+		}
+	}
+	return series
+}
+
+func buildMethodDistribution(orders []*dbent.PaymentOrder) []PaymentMethodStat {
+	methodMap := make(map[string]*PaymentMethodStat)
+	for _, o := range orders {
+		ms, ok := methodMap[o.PaymentType]
+		if !ok {
+			ms = &PaymentMethodStat{Type: o.PaymentType}
+			methodMap[o.PaymentType] = ms
+		}
+		ms.Amount += o.PayAmount
+		ms.Count++
+	}
+	methods := make([]PaymentMethodStat, 0, len(methodMap))
+	for _, ms := range methodMap {
+		ms.Amount = math.Round(ms.Amount*100) / 100
+		methods = append(methods, *ms)
+	}
+	return methods
+}
+
+func buildTopUsers(orders []*dbent.PaymentOrder) []TopUserStat {
+	userMap := make(map[int64]*TopUserStat)
+	for _, o := range orders {
+		us, ok := userMap[o.UserID]
+		if !ok {
+			us = &TopUserStat{UserID: o.UserID, Email: o.UserEmail}
+			userMap[o.UserID] = us
+		}
+		us.Amount += o.PayAmount
+	}
+	userList := make([]*TopUserStat, 0, len(userMap))
+	for _, us := range userMap {
+		us.Amount = math.Round(us.Amount*100) / 100
+		userList = append(userList, us)
+	}
+	sort.Slice(userList, func(i, j int) bool {
+		return userList[i].Amount > userList[j].Amount
+	})
+	limit := topUsersLimit
+	if len(userList) < limit {
+		limit = len(userList)
+	}
+	result := make([]TopUserStat, 0, limit)
+	for i := 0; i < limit; i++ {
+		result = append(result, *userList[i])
+	}
+	return result
+}
+
+// --- Audit Logs ---
+
+func (s *PaymentService) writeAuditLog(ctx context.Context, oid int64, action, op string, detail map[string]any) {
+	dj, _ := json.Marshal(detail)
+	_, err := s.entClient.PaymentAuditLog.Create().SetOrderID(strconv.FormatInt(oid, 10)).SetAction(action).SetDetail(string(dj)).SetOperator(op).Save(ctx)
+	if err != nil {
+		slog.Error("audit log failed", "orderID", oid, "action", action, "error", err)
+	}
+}
+
+func (s *PaymentService) GetOrderAuditLogs(ctx context.Context, oid int64) ([]*dbent.PaymentAuditLog, error) {
+	return s.entClient.PaymentAuditLog.Query().Where(paymentauditlog.OrderIDEQ(strconv.FormatInt(oid, 10))).Order(paymentauditlog.ByCreatedAt()).All(ctx)
+}