DEV-MERGE-LEGACY-BACKEND-2026/internal/academic/service/activity_discount_service_test.go

// ActivityDiscountService 单测（AC-07）：充值赠送使用/退回 + 代金券使用/退回 + 可用额。
//
// 断言纪律（对照 §5.1 第 4 条「横切优先」——**不是**数 case 数量）：
//  1. **退回分配顺序（降序）是阻断级**：两次用券 100/50、退 120 ⇒ **先 50 再 70**。
//     若把 `id DESC` 写成 `ASC`，总额同样是 120，只有"逐条明细"能证明分配错误 ⇒
//     本文件断言 `Items` 的顺序与逐条金额，而不只断言合计。
//  2. **盖帽**：退 40 只能退 40（单行冲回额 = min(|行金额|, 剩余应退)）。
//  3. **账务恒等式（自证失败式）**：`signed.activity_money_used == -Σ(used_log)`、
//     `pool.discount_amount_used == -Σ(discount_log)`——任何"少写一条流水/金额算错"都会立刻破式。
//  4. **代金券一次全额退**：type=3 的退回额 = 券面额，再按最近一条消费额盖帽（A13 修正）。
package service

import (
	"context"
	"testing"

	"gorm.io/gorm"

	"yuansiwei/unified-backend/internal/academic/apperr"
	"yuansiwei/unified-backend/internal/academic/model"
	"yuansiwei/unified-backend/internal/academic/money"
)

// ---------------------------------------------------------------- 辅助

// seedSignedFull 落一行报名行（可指定状态与两列金额）。
func seedSignedFull(t *testing.T, db *gorm.DB, userID string, activityID int64, status int32,
	activityMoney, activityMoneyUsed string) {
	t.Helper()
	row := &model.CoursesActivitySigned{
		ActivityID: activityID, UserID: userID, InstitutionID: 1, CampusID: 10,
		Status: status, ActivityMoney: activityMoney, ActivityMoneyUsed: activityMoneyUsed,
	}
	if err := db.Create(row).Error; err != nil {
		t.Fatalf("seed 报名行失败: %v", err)
	}
}

// seedPool 落一行赠送池（返回池 ID）。
func seedPool(t *testing.T, db *gorm.DB, userID string, activityID int64,
	discountAmount, discountAmountUsed string) int64 {
	t.Helper()
	row := &model.CoursesActivityUserDiscount{
		ActivityID: activityID, InstitutionID: 1, CampusID: 10, UserID: userID,
		DiscountAmount: discountAmount, DiscountAmountUsed: discountAmountUsed,
	}
	if err := db.Create(row).Error; err != nil {
		t.Fatalf("seed 赠送池失败: %v", err)
	}
	return row.ID
}

// readSignedUsed 读报名行已用额（分）。
func readSignedUsed(t *testing.T, db *gorm.DB, userID string, activityID int64) int64 {
	t.Helper()
	row := readSignedRow(t, db, userID, activityID)
	if row == nil {
		t.Fatalf("报名行不存在(user=%s,activity=%d)", userID, activityID)
	}
	return cents(t, row.ActivityMoneyUsed)
}

// sumUsedLogAmount 汇总某活动某用户的 used_log 金额（分；消费为负、退回为正）。
func sumUsedLogAmount(t *testing.T, db *gorm.DB, activityID int64, userID string) int64 {
	t.Helper()
	var rows []model.CoursesActivityUsedLog
	if err := db.Where("activity_id = ? AND user_id = ?", activityID, userID).Find(&rows).Error; err != nil {
		t.Fatalf("读 used_log 失败: %v", err)
	}
	total := int64(0)
	for i := range rows {
		total += cents(t, rows[i].ActivityMoneyUsed)
	}
	return total
}

// readPoolUsed 读池已用额（分）。
func readPoolUsed(t *testing.T, db *gorm.DB, poolID int64) int64 {
	t.Helper()
	var row model.CoursesActivityUserDiscount
	if err := db.Where("id = ?", poolID).Take(&row).Error; err != nil {
		t.Fatalf("读赠送池(%d) 失败: %v", poolID, err)
	}
	return cents(t, row.DiscountAmountUsed)
}

// sumDiscountLogAmount 汇总某池的 discount_log 金额（分；消费为负、退回为正）。
func sumDiscountLogAmount(t *testing.T, db *gorm.DB, poolID int64) int64 {
	t.Helper()
	var rows []model.CoursesActivityUserDiscountLog
	if err := db.Where("activity_user_discount_id = ?", poolID).Find(&rows).Error; err != nil {
		t.Fatalf("读 discount_log 失败: %v", err)
	}
	total := int64(0)
	for i := range rows {
		total += cents(t, rows[i].DiscountAmountUsed)
	}
	return total
}

// ---------------------------------------------------------------- 充值赠送：使用（SP12）

// TestUseRechargeGiftCapsToRemainingAndKeepsLedgerIdentity
// 使用额不得超过活动剩余额（A9 修正），且 `signed.used == -Σ used_log` 恒成立。
func TestUseRechargeGiftCapsToRemainingAndKeepsLedgerIdentity(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(20)

	seedActivityFull(t, db, 400, model.ActivityTypeRecharge, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	seedSignedFull(t, db, user, 400, model.ActivitySignedAttended, "100.00", "0.00")

	// 第一次：用 30（小于剩余 100）
	first, err := svc.UseRechargeGift(ctx, UseRechargeGiftInput{
		UserID: user, ActivityID: 400, StudentCourseID: 5001, Amount: mustAmount(t, "30.00"),
	})
	if err != nil {
		t.Fatalf("使用充值赠送失败: %v", err)
	}
	if first.UsedAmount.Cents() != 3000 || first.Remaining.Cents() != 7000 {
		t.Fatalf("首用应 3000 分、剩余 7000 分，实得 %d/%d",
			first.UsedAmount.Cents(), first.Remaining.Cents())
	}

	// 第二次：请求 90，但只剩 70 → 只能扣 70（A9：逐行递减到剩余额为止）
	second, err := svc.UseRechargeGift(ctx, UseRechargeGiftInput{
		UserID: user, ActivityID: 400, StudentCourseID: 5002, Amount: mustAmount(t, "90.00"),
	})
	if err != nil {
		t.Fatalf("第二次使用失败: %v", err)
	}
	if second.UsedAmount.Cents() != 7000 || second.Remaining.Cents() != 0 {
		t.Fatalf("第二次应被截到 7000 分、剩余 0，实得 %d/%d",
			second.UsedAmount.Cents(), second.Remaining.Cents())
	}

	// 第三次：额度已用完 → no-op（不写流水）
	third, err := svc.UseRechargeGift(ctx, UseRechargeGiftInput{
		UserID: user, ActivityID: 400, StudentCourseID: 5003, Amount: mustAmount(t, "10.00"),
	})
	if err != nil {
		t.Fatalf("第三次使用失败: %v", err)
	}
	if third.UsedAmount.Cents() != 0 {
		t.Fatalf("额度用完后应为 no-op，实得 %d 分", third.UsedAmount.Cents())
	}

	// 横切恒等式：报名行已用额 == -(Σ used_log)
	used := readSignedUsed(t, db, user, 400)
	if used != 10000 {
		t.Fatalf("报名行已用额应 10000 分，实得 %d", used)
	}
	if sum := sumUsedLogAmount(t, db, 400, user); sum != -used {
		t.Fatalf("恒等式破式：signed.used=%d 应等于 -Σ(used_log)=%d", used, -sum)
	}
}

// TestUseRechargeGiftRequiresAttendedStatus 报名行状态非 2（未参加）→ no-op（dump 游标条件）。
func TestUseRechargeGiftRequiresAttendedStatus(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(21)

	seedActivityFull(t, db, 401, model.ActivityTypeRecharge, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	seedSignedFull(t, db, user, 401, model.ActivitySignedSigned, "100.00", "0.00")

	res, err := svc.UseRechargeGift(ctx, UseRechargeGiftInput{
		UserID: user, ActivityID: 401, StudentCourseID: 5004, Amount: mustAmount(t, "10.00"),
	})
	if err != nil {
		t.Fatalf("使用充值赠送失败: %v", err)
	}
	if res.UsedAmount.Cents() != 0 {
		t.Fatalf("报名行 status!=2 时必须 no-op，实得 %d 分", res.UsedAmount.Cents())
	}
	if used := readSignedUsed(t, db, user, 401); used != 0 {
		t.Fatalf("报名行已用额应保持 0，实得 %d", used)
	}
	if sum := sumUsedLogAmount(t, db, 401, user); sum != 0 {
		t.Fatalf("不得写 used_log，实得合计 %d", sum)
	}
}

// ---------------------------------------------------------------- 充值赠送：退回（SP13）

// TestRefundRechargeGiftAllocatesDescending **降序分配**：先冲回最近一笔（50），再 70。
func TestRefundRechargeGiftAllocatesDescending(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(22)

	seedActivityFull(t, db, 402, model.ActivityTypeRecharge, "200.00", 1, 10, 0, model.ActivityStatusEnabled)
	seedSignedFull(t, db, user, 402, model.ActivitySignedAttended, "200.00", "150.00")
	// id 小的是**较早**的一笔（-100），id 大的是最近一笔（-50）
	seedUsedLogRow(t, db, 402, user, "6001", "-100.00")
	seedUsedLogRow(t, db, 402, user, "6001", "-50.00")

	res, err := svc.RefundRechargeGift(ctx, RefundRechargeGiftInput{
		StudentCourseID: 6001, Amount: mustAmount(t, "120.00"),
	})
	if err != nil {
		t.Fatalf("退回充值赠送失败: %v", err)
	}
	if res.RefundedTotal.Cents() != 12000 {
		t.Fatalf("应退 12000 分，实得 %d", res.RefundedTotal.Cents())
	}
	if len(res.Items) != 2 {
		t.Fatalf("应命中 2 笔，实得 %d 笔（%+v）", len(res.Items), res.Items)
	}
	// ★ 顺序断言：先 50（最近一笔），再 70（差额补到较早那笔）
	if res.Items[0].Amount.Cents() != 5000 {
		t.Fatalf("第一笔应为 5000 分（后入先退），实得 %d", res.Items[0].Amount.Cents())
	}
	if res.Items[1].Amount.Cents() != 7000 {
		t.Fatalf("第二笔应为 7000 分，实得 %d", res.Items[1].Amount.Cents())
	}

	// 横切恒等式：use(+150) 与 refund(-120) 之后 signed.used 应为 30
	if used := readSignedUsed(t, db, user, 402); used != 3000 {
		t.Fatalf("退回后报名行已用额应 3000 分，实得 %d", used)
	}
	if sum := sumUsedLogAmount(t, db, 402, user); sum != -3000 {
		t.Fatalf("恒等式破式：signed.used=3000 应等于 -Σ(used_log)=%d", -sum)
	}
}

// TestRefundRechargeGiftCapsAtRequested 退 40 只退 40（盖上"请求额"）。
func TestRefundRechargeGiftCapsAtRequested(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(23)

	seedActivityFull(t, db, 403, model.ActivityTypeRecharge, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	seedSignedFull(t, db, user, 403, model.ActivitySignedAttended, "100.00", "100.00")
	seedUsedLogRow(t, db, 403, user, "6002", "-100.00")

	res, err := svc.RefundRechargeGift(ctx, RefundRechargeGiftInput{
		StudentCourseID: 6002, Amount: mustAmount(t, "40.00"),
	})
	if err != nil {
		t.Fatalf("退回充值赠送失败: %v", err)
	}
	if res.RefundedTotal.Cents() != 4000 {
		t.Fatalf("只应退 4000 分，实得 %d", res.RefundedTotal.Cents())
	}
	if len(res.Items) != 1 || res.Items[0].Amount.Cents() != 4000 {
		t.Fatalf("应 1 笔 4000 分，实得 %+v", res.Items)
	}
	if used := readSignedUsed(t, db, user, 403); used != 6000 {
		t.Fatalf("退回 40 后已用额应 6000 分，实得 %d", used)
	}
}

// TestRefundRechargeGiftSkipsNonRechargeActivities 非 type=2 活动的流水不参与冲回（dump `IF type=2`）。
func TestRefundRechargeGiftSkipsNonRechargeActivities(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(24)

	seedActivityFull(t, db, 404, model.ActivityTypeRecommend, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	seedSignedFull(t, db, user, 404, model.ActivitySignedAttended, "100.00", "100.00")
	seedUsedLogRow(t, db, 404, user, "6003", "-100.00")

	res, err := svc.RefundRechargeGift(ctx, RefundRechargeGiftInput{
		StudentCourseID: 6003, Amount: mustAmount(t, "100.00"),
	})
	if err != nil {
		t.Fatalf("退回充值赠送失败: %v", err)
	}
	if res.RefundedTotal.Cents() != 0 || len(res.Items) != 0 {
		t.Fatalf("非充值赠送活动不得冲回，实得 %+v", res.Items)
	}
	if used := readSignedUsed(t, db, user, 404); used != 10000 {
		t.Fatalf("已用额应保持 10000 分，实得 %d", used)
	}
}

// ---------------------------------------------------------------- 代金券：使用（SP15）

// TestUseVoucherType3UsesFaceValue 代金券按 dump 口径取**券面额**（不是请求额、也不是剩余额）。
func TestUseVoucherType3UsesFaceValue(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(25)

	seedActivityFull(t, db, 405, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 405, "100.00", "0.00")

	res, err := svc.UseVoucher(ctx, UseVoucherInput{
		UserID: user, ActivityID: 405, StudentCourseID: 7001, Amount: mustAmount(t, "30.00"),
	})
	if err != nil {
		t.Fatalf("使用代金券失败: %v", err)
	}
	if res.Applied.Cents() != 10000 {
		t.Fatalf("代金券应按面额 10000 分占用，实得 %d", res.Applied.Cents())
	}
	if got := readPoolUsed(t, db, poolID); got != 10000 {
		t.Fatalf("池已用额应 10000 分，实得 %d", got)
	}
	// 横切恒等式：pool.used == -Σ(discount_log)
	if sum := sumDiscountLogAmount(t, db, poolID); sum != -10000 {
		t.Fatalf("恒等式破式：pool.used=10000 应等于 -Σ(discount_log)=%d", -sum)
	}
}

// TestUseVoucherRejectsInsufficientWith3109 可用额不足 → 3109（dump 静默 LEAVE，Go 显式）。
func TestUseVoucherRejectsInsufficientWith3109(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(26)

	seedActivityFull(t, db, 406, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 406, "100.00", "90.00") // 只剩 10

	_, err := svc.UseVoucher(ctx, UseVoucherInput{
		UserID: user, ActivityID: 406, StudentCourseID: 7002, Amount: mustAmount(t, "20.00"),
	})
	wantAppErr(t, err, apperr.CodeGiftAmountShort, "可用赠送金额不足")

	if got := readPoolUsed(t, db, poolID); got != 9000 {
		t.Fatalf("被 3109 拒绝后池已用额不得变，实得 %d", got)
	}
	// 被拒后**零副作用**：池已用额与流水条数都不变（种子池本身没有流水行 → 合计应为 0）
	if sum := sumDiscountLogAmount(t, db, poolID); sum != 0 {
		t.Fatalf("被 3109 拒绝后不得写 discount_log，实得合计 %d", sum)
	}
}

// ---------------------------------------------------------------- 代金券/赠送：按报课记录退回（SP16）

// TestRefundByStuCourseDescendingWithCap 降序（50 → 70）+ 盖帽（退 40 只退 40）。
func TestRefundByStuCourseDescendingWithCap(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(27)

	seedActivityFull(t, db, 407, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 407, "150.00", "150.00")
	// 两次用券：先 100、后 50（同一报课记录）→ 池 used = 150
	seedDiscountLogRow(t, db, poolID, 8001, "-100.00")
	seedDiscountLogRow(t, db, poolID, 8001, "-50.00")

	res, err := svc.RefundByStuCourse(ctx, RefundByStuCourseInput{
		StudentCourseID: 8001, Amount: mustAmount(t, "120.00"),
	})
	if err != nil {
		t.Fatalf("按报课记录退回失败: %v", err)
	}
	if res.RefundedTotal.Cents() != 12000 {
		t.Fatalf("应退 12000 分，实得 %d", res.RefundedTotal.Cents())
	}
	if len(res.Items) != 2 || res.Items[0].Amount.Cents() != 5000 || res.Items[1].Amount.Cents() != 7000 {
		t.Fatalf("降序分配应为 5000→7000，实得 %+v", res.Items)
	}
	if got := readPoolUsed(t, db, poolID); got != 3000 {
		t.Fatalf("退回后池已用额应 3000 分，实得 %d", got)
	}
	if sum := sumDiscountLogAmount(t, db, poolID); sum != -3000 {
		t.Fatalf("恒等式破式：pool.used=3000 应等于 -Σ(discount_log)=%d", -sum)
	}
}

// TestRefundByStuCourseCapsAtRequested 退 40 只退 40。
func TestRefundByStuCourseCapsAtRequested(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(28)

	seedActivityFull(t, db, 408, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 408, "100.00", "100.00")
	seedDiscountLogRow(t, db, poolID, 8002, "-100.00")

	res, err := svc.RefundByStuCourse(ctx, RefundByStuCourseInput{
		StudentCourseID: 8002, Amount: mustAmount(t, "40.00"),
	})
	if err != nil {
		t.Fatalf("按报课记录退回失败: %v", err)
	}
	if res.RefundedTotal.Cents() != 4000 || len(res.Items) != 1 {
		t.Fatalf("应退 4000 分 1 笔，实得 %d 分 %d 笔", res.RefundedTotal.Cents(), len(res.Items))
	}
	if got := readPoolUsed(t, db, poolID); got != 6000 {
		t.Fatalf("池已用额应 6000 分，实得 %d", got)
	}
}

// ---------------------------------------------------------------- 代金券：按活动退回（SP17）

// TestRefundByActivityVoucherFullRefund 代金券一次全额退（amount 置为券面额）。
func TestRefundByActivityVoucherFullRefund(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(29)

	seedActivityFull(t, db, 409, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 409, "100.00", "100.00")
	seedDiscountLogRow(t, db, poolID, 9001, "-100.00")

	// 请求 30，但代金券一次全额退 → 实际退 100（再按最近一条消费额 100 盖帽）
	res, err := svc.RefundByActivity(ctx, RefundByActivityInput{
		UserID: user, ActivityID: 409, Amount: mustAmount(t, "30.00"),
	})
	if err != nil {
		t.Fatalf("按活动退回失败: %v", err)
	}
	if res.Refunded.Cents() != 10000 {
		t.Fatalf("代金券应一次全额退 10000 分，实得 %d", res.Refunded.Cents())
	}
	if got := readPoolUsed(t, db, poolID); got != 0 {
		t.Fatalf("全额退后池已用额应 0，实得 %d", got)
	}
	if sum := sumDiscountLogAmount(t, db, poolID); sum != 0 {
		t.Fatalf("恒等式破式：pool.used=0 应等于 -Σ(discount_log)=%d", -sum)
	}
}

// TestRefundByActivityCappedByLastLog A13 修正：非代金券按"最近一条消费额"盖帽，不得超退。
func TestRefundByActivityCappedByLastLog(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(30)

	seedActivityFull(t, db, 410, model.ActivityTypeRecharge, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 410, "100.00", "50.00")
	seedDiscountLogRow(t, db, poolID, 9002, "-50.00")

	// 请求 80 > 最近一条消费 50 → 只能退 50（dump 的 `SELECT x = y` 从未赋值 ⇒ 会退 80，A13 修正）
	res, err := svc.RefundByActivity(ctx, RefundByActivityInput{
		UserID: user, ActivityID: 410, Amount: mustAmount(t, "80.00"),
	})
	if err != nil {
		t.Fatalf("按活动退回失败: %v", err)
	}
	if res.Refunded.Cents() != 5000 {
		t.Fatalf("应盖帽到 5000 分，实得 %d", res.Refunded.Cents())
	}
	if got := readPoolUsed(t, db, poolID); got != 0 {
		t.Fatalf("池已用额应 0，实得 %d", got)
	}
	if sum := sumDiscountLogAmount(t, db, poolID); sum != 0 {
		t.Fatalf("恒等式破式：pool.used=0 应等于 -Σ(discount_log)=%d", -sum)
	}
}

// TestRefundByActivityNoLogIsNoop 无消费流水 → no-op（dump LIMIT 1 空）。
func TestRefundByActivityNoLogIsNoop(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(31)

	seedActivityFull(t, db, 411, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	poolID := seedPool(t, db, user, 411, "100.00", "0.00")

	res, err := svc.RefundByActivity(ctx, RefundByActivityInput{
		UserID: user, ActivityID: 411, Amount: mustAmount(t, "100.00"),
	})
	if err != nil {
		t.Fatalf("按活动退回失败: %v", err)
	}
	if res.Refunded.Cents() != 0 {
		t.Fatalf("无消费流水应 no-op，实得 %d", res.Refunded.Cents())
	}
	if got := readPoolUsed(t, db, poolID); got != 0 {
		t.Fatalf("池已用额应保持 0，实得 %d", got)
	}
}

// ---------------------------------------------------------------- 可用额汇总（SP14）

// TestUsableAmountAggregatesAndRespectsScope 可用额 = Σ(face−used)（仅 face>used 的行），
// 且 `institutionID>0` 时校区条件是**等值**（campus_id=0 的机构级池只在 campusID=0 时命中）。
func TestUsableAmountAggregatesAndRespectsScope(t *testing.T) {
	db := newActivityDomainDB(t)
	svc := NewActivityDiscountService(db, fundSuperScope())
	ctx := context.Background()
	user := fundUserID(32)

	seedActivityFull(t, db, 412, model.ActivityTypeVoucher, "100.00", 1, 10, 0, model.ActivityStatusEnabled)
	seedPool(t, db, user, 412, "100.00", "30.00") // 本校区：可用 70
	// 机构级池（campus_id=0）：可用 10
	if err := db.Create(&model.CoursesActivityUserDiscount{
		ActivityID: 412, InstitutionID: 1, CampusID: 0, UserID: user,
		DiscountAmount: "10.00", DiscountAmountUsed: "0.00",
	}).Error; err != nil {
		t.Fatalf("seed 机构级池失败: %v", err)
	}
	// 已用尽的行不参与（face == used）
	seedPool(t, db, user, 412, "50.00", "50.00")

	// campusID=10：只命中本校区池 → 70
	res, err := svc.UsableAmount(ctx, UsableAmountInput{UserID: user, InstitutionID: 1, CampusID: 10})
	if err != nil {
		t.Fatalf("汇总可用额失败: %v", err)
	}
	if res.Usable.Cents() != 7000 {
		t.Fatalf("本校区可用额应 7000 分（等值过滤，不含机构级池），实得 %d", res.Usable.Cents())
	}

	// campusID=0：只命中机构级池 → 10
	res, err = svc.UsableAmount(ctx, UsableAmountInput{UserID: user, InstitutionID: 1, CampusID: 0})
	if err != nil {
		t.Fatalf("汇总可用额失败: %v", err)
	}
	if res.Usable.Cents() != 1000 {
		t.Fatalf("机构级池可用额应 1000 分，实得 %d", res.Usable.Cents())
	}

	// institutionID=0：平台视角，不加任何作用域条件 → 70+10=80
	res, err = svc.UsableAmount(ctx, UsableAmountInput{UserID: user})
	if err != nil {
		t.Fatalf("汇总可用额失败: %v", err)
	}
	if res.Usable.Cents() != 8000 {
		t.Fatalf("平台视角可用额应 8000 分，实得 %d", res.Usable.Cents())
	}
}

// seedDiscountLogRow 落一行 discount_log（负=消费/正=退回）。
func seedDiscountLogRow(t *testing.T, db *gorm.DB, poolID int64, stuCourseID int64, amount string) {
	t.Helper()
	row := &model.CoursesActivityUserDiscountLog{
		ActivityUserDiscountID: poolID,
		CoursesStudentID:       &stuCourseID,
		DiscountAmountUsed:     amount,
	}
	if err := db.Create(row).Error; err != nil {
		t.Fatalf("seed discount_log 失败: %v", err)
	}
}

// 编译期断言：避免 money 包被"只用类型"时误删导入。
var _ = money.FromCents