DEV-MERGE-LEGACY-BACKEND-2026/internal/academic/dualrun/cases.go

package dualrun

import (
	"database/sql"
	"fmt"
	"sort"
	"strings"
	"time"
)

// 兜底层级（与 SP 的四级兜底一一对应）。
const (
	TierTeacherClassify     = "teacher-classify"      // 老师 + 具体分类
	TierTeacherGradeSubject = "teacher-grade-subject" // 老师 + 年级/科目
	TierCert                = "cert-tier"             // 持证老师 + 教龄档
	TierGeneric             = "generic-tier"          // 通用 + 教龄档
	TierDegraded            = "degraded"              // SP 无命中 ⇒ PHP 走 legacy 退化分支
	TierNone                = "none"
)

// 用例类别。
const (
	CatBaseline      = "baseline"
	CatTier          = "tier"
	CatIncome3DP     = "income-3dp"
	CatIncomeZeroMin = "income-zero-min"
	CatSupplement    = "supplement-both"
	CatNonDivisible  = "nondivisible"
	CatRewardType2   = "rewardtype2"
)

// ---------- 内存参照表（小表全量装载，避免 74,870 次相关子查询）----------

type payRow struct {
	id       int64
	schoolid int64
	campusid int64
	actived  int64
	effect   time.Time
}

type clsRow struct {
	id        int64
	gradeid   int64
	subjectid int64
	classType int64
}

type teacherRow struct {
	exp    time.Time
	cert   int64
	hasExp bool
}

type detailRow struct {
	id         int64
	paymentid  int64
	teacherid  int64
	cert       int64
	classType  int64
	gradeid    int64
	subjectid  int64
	expMin     float64
	expMax     float64
	classifyid int64
	percentage float64
	minPay     float64
	maxPay     float64
	reward     float64
}

type aggRow struct {
	sumCost float64
	elig    int
	rows    int
}

type refs struct {
	pays        []payRow
	classifies  map[int64]*clsRow
	courseClass map[int64]int64
	teachers    map[int64]teacherRow
	details     map[int64][]detailRow // paymentid → 规则
	detailByID  map[int64]detailRow
	studentAgg  map[string]aggRow // recordid → 打卡聚合
}

func loadRefs(db *sql.DB, schema string) (*refs, error) {
	r := &refs{
		classifies:  map[int64]*clsRow{},
		courseClass: map[int64]int64{},
		teachers:    map[int64]teacherRow{},
		details:     map[int64][]detailRow{},
		detailByID:  map[int64]detailRow{},
		studentAgg:  map[string]aggRow{},
	}

	rows, err := db.Query("SELECT id, schoolid, IFNULL(campusid,0), CAST(IFNULL(actived,0) AS UNSIGNED), " +
		"DATE_FORMAT(IFNULL(effect_date,'1970-01-01'),'%Y-%m-%d %H:%i:%s') FROM " + schema + ".t_course_payment")
	if err != nil {
		return nil, fmt.Errorf("load payments: %w", err)
	}
	for rows.Next() {
		var p payRow
		var eff string
		if err := rows.Scan(&p.id, &p.schoolid, &p.campusid, &p.actived, &eff); err == nil {
			p.effect, _ = time.ParseInLocation("2006-01-02 15:04:05", eff, time.Local)
			r.pays = append(r.pays, p)
		}
	}
	rows.Close()

	if rows, err = db.Query("SELECT id, IFNULL(gradeid,-1), IFNULL(subjectid,-1), IFNULL(class_type,0) FROM " + schema + ".t_courses_classify"); err == nil {
		for rows.Next() {
			var c clsRow
			if err := rows.Scan(&c.id, &c.gradeid, &c.subjectid, &c.classType); err == nil {
				cc := c
				r.classifies[c.id] = &cc
			}
		}
		rows.Close()
	} else {
		return nil, fmt.Errorf("load classify: %w", err)
	}

	if rows, err = db.Query("SELECT id, IFNULL(classifyid,0) FROM " + schema + ".t_courses"); err == nil {
		for rows.Next() {
			var id, cid int64
			if err := rows.Scan(&id, &cid); err == nil {
				r.courseClass[id] = cid
			}
		}
		rows.Close()
	} else {
		return nil, fmt.Errorf("load courses: %w", err)
	}

	if rows, err = db.Query("SELECT teacherid, IFNULL(DATE_FORMAT(teacher_exp,'%Y-%m-%d %H:%i:%s'),''), " +
		"CAST(IFNULL(teacher_cert,0) AS UNSIGNED) FROM " + schema + ".t_teacher_information"); err == nil {
		for rows.Next() {
			var id int64
			var expStr string
			var t teacherRow
			if err := rows.Scan(&id, &expStr, &t.cert); err == nil {
				if expStr != "" {
					t.exp, _ = time.ParseInLocation("2006-01-02 15:04:05", expStr, time.Local)
					t.hasExp = true
				}
				r.teachers[id] = t
			}
		}
		rows.Close()
	} else {
		return nil, fmt.Errorf("load teachers: %w", err)
	}

	rows, err = db.Query("SELECT id, course_paymentid, IFNULL(teacherid,0), CAST(IFNULL(teacher_cert,0) AS UNSIGNED), " +
		"IFNULL(class_type,0), IFNULL(gradeid,-1), IFNULL(subjectid,-1), IFNULL(teacher_exp_min,0), IFNULL(teacher_exp_max,0), " +
		"IFNULL(classifyid,0), IFNULL(percentage,0), IFNULL(min_payment,0), IFNULL(max_payment,0), IFNULL(reward,0) FROM " +
		schema + ".t_course_payment_detail")
	if err != nil {
		return nil, fmt.Errorf("load rules: %w", err)
	}
	for rows.Next() {
		var d detailRow
		if err := rows.Scan(&d.id, &d.paymentid, &d.teacherid, &d.cert, &d.classType, &d.gradeid, &d.subjectid,
			&d.expMin, &d.expMax, &d.classifyid, &d.percentage, &d.minPay, &d.maxPay, &d.reward); err == nil {
			r.details[d.paymentid] = append(r.details[d.paymentid], d)
			r.detailByID[d.id] = d
		}
	}
	rows.Close()

	rows, err = db.Query("SELECT recordid, IFNULL(SUM(cost),0), SUM(type IN (1,2)), COUNT(*) FROM " +
		schema + ".t_courses_record_student GROUP BY recordid")
	if err != nil {
		return nil, fmt.Errorf("load student agg: %w", err)
	}
	for rows.Next() {
		var rid string
		var a aggRow
		if err := rows.Scan(&rid, &a.sumCost, &a.elig, &a.rows); err == nil {
			r.studentAgg[rid] = a
		}
	}
	rows.Close()

	return r, nil
}

// resolvePayment 复刻 SP 的两级找方案：先 (school,campus)，再 (school,0)。
func (r *refs) resolvePayment(schoolid, campusid int64, at time.Time) int64 {
	best, varEff := int64(0), time.Time{}
	for _, p := range r.pays {
		if p.schoolid != schoolid || p.actived != 1 || p.campusid != campusid || p.effect.After(at) {
			continue
		}
		if best == 0 || p.effect.After(varEff) {
			best, varEff = p.id, p.effect
		}
	}
	if best > 0 {
		return best
	}
	for _, p := range r.pays {
		if p.schoolid != schoolid || p.actived != 1 || p.campusid != 0 || p.effect.After(at) {
			continue
		}
		if best == 0 || p.effect.After(varEff) {
			best, varEff = p.id, p.effect
		}
	}
	return best
}

// hitRule 复刻 sp_course_payment_detail_get_teacher_detail 的判定顺序，返回 (规则, 层级)。
//
// 顺序（与 SP 一致，不可换）：
//  1. teacher-classify     老师专属 + classifyid 精确匹配
//  2. teacher-grade-subject 老师专属 + 年级/科目（含 -1 通配）
//  3. cert-tier            持证 + 教龄档
//  4. generic-tier         通用 + 教龄档
//
// 注意 SP 用 `id>1` 才采纳（历史怪癖），这里照抄。
func (r *refs) hitRule(schoolid, campusid, teacherid int64, at time.Time, cls *clsRow, teacherExp float64, teacherCert int64) (detailRow, string, bool) {
	if cls == nil {
		return detailRow{}, TierNone, false
	}
	payid := r.resolvePayment(schoolid, campusid, at)
	if payid <= 0 {
		return detailRow{}, TierDegraded, false
	}
	if teacherExp < 0 {
		teacherExp = 0
	}
	oneself := 0
	for _, d := range r.details[payid] {
		if d.teacherid == teacherid && d.classType == cls.classType {
			oneself++
		}
	}
	find := func(match func(d detailRow) bool) (detailRow, bool) {
		var best detailRow
		found := false
		for _, d := range r.details[payid] {
			if d.classType != cls.classType || !match(d) {
				continue
			}
			if !found || d.id < best.id {
				best, found = d, true
			}
		}
		if found && best.id > 1 {
			return best, true
		}
		return detailRow{}, false
	}
	if oneself > 0 {
		if d, ok := find(func(d detailRow) bool { return d.teacherid == teacherid && d.classifyid == cls.id }); ok {
			return d, TierTeacherClassify, true
		}
		if d, ok := find(func(d detailRow) bool {
			return d.teacherid == teacherid &&
				(d.gradeid == cls.gradeid || d.gradeid == -1) &&
				(d.subjectid == cls.subjectid || d.subjectid == -1)
		}); ok {
			return d, TierTeacherGradeSubject, true
		}
	}
	if teacherCert > 0 {
		if d, ok := find(func(d detailRow) bool {
			return d.teacherid == 0 && d.cert == 1 &&
				(d.gradeid == cls.gradeid || d.gradeid == -1) &&
				(d.subjectid == cls.subjectid || d.subjectid == -1) &&
				teacherExp >= d.expMin && teacherExp <= d.expMax
		}); ok {
			return d, TierCert, true
		}
	}
	if d, ok := find(func(d detailRow) bool {
		return d.teacherid == 0 && d.cert == 0 &&
			(d.gradeid == cls.gradeid || d.gradeid == -1) &&
			(d.subjectid == cls.subjectid || d.subjectid == -1) &&
			teacherExp >= d.expMin && teacherExp <= d.expMax
	}); ok {
		return d, TierGeneric, true
	}
	return detailRow{}, TierDegraded, false
}

// teacherExpYears 与 PHP `Utils::calculatingAge()` 同口径：固定 365 天/年、四舍五入 1 位。
//
// ⚠ 这里用 runner 自己的 `now` 计算，只用于**选 case 与命中预判**；
// 真正参与 oracle 计算的教龄由 PHP 侧 `time()` 决定（A22：PHP 时钟不受 SET timestamp 影响）。
func teacherExpYears(t teacherRow, now time.Time) float64 {
	if !t.hasExp || t.exp.Year() <= 1970 {
		return 0
	}
	years := now.Sub(t.exp).Hours() / 24 / 365
	return float64(int(years*10+0.5)) / 10
}

// recordRow 是挑选 case 时需要的 record 字段。
type recordRow struct {
	id         string
	schoolid   int64
	campusid   int64
	teacherid  int64
	coursesid  int64
	rewardType int8
	stuNumber  int
	status     int
	income     float64
	startTime  time.Time
}

// loadRecords 流式扫描 record（只取必要列）。
func loadRecords(db *sql.DB, schema string) ([]recordRow, error) {
	rows, err := db.Query("SELECT id, schoolid, IFNULL(campusid,0), teacherid, coursesid, " +
		"IFNULL(teacher_reward_type,1), IFNULL(student_number,0), IFNULL(status,0), IFNULL(income,0), " +
		"DATE_FORMAT(actual_start_time,'%Y-%m-%d %H:%i:%s') FROM " + schema + ".t_courses_record " +
		"WHERE teacherid>0 AND actual_start_time IS NOT NULL AND coursesid IS NOT NULL ORDER BY id")
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []recordRow
	for rows.Next() {
		var rec recordRow
		var st string
		if err := rows.Scan(&rec.id, &rec.schoolid, &rec.campusid, &rec.teacherid, &rec.coursesid,
			&rec.rewardType, &rec.stuNumber, &rec.status, &rec.income, &st); err == nil {
			rec.startTime, _ = time.ParseInLocation("2006-01-02 15:04:05", st, time.Local)
			out = append(out, rec)
		}
	}
	return out, rows.Err()
}

// caseFacts 是一条 record 在"选 case"阶段算出的全部判定依据。
type caseFacts struct {
	rec      recordRow
	cls      *clsRow
	teacher  teacherRow
	expYears float64
	agg      aggRow
	rule     detailRow
	tier     string
	hit      bool
}

// buildFacts 给一条 record 补全判定依据。
func (r *refs) buildFacts(rec recordRow, now time.Time) caseFacts {
	cls := r.classifies[r.courseClass[rec.coursesid]]
	t := r.teachers[rec.teacherid]
	exp := teacherExpYears(t, now)
	rule, tier, ok := r.hitRule(rec.schoolid, rec.campusid, rec.teacherid, rec.startTime, cls, exp, t.cert)
	return caseFacts{
		rec: rec, cls: cls, teacher: t, expYears: exp,
		agg: r.studentAgg[rec.id], rule: rule, tier: tier, hit: ok,
	}
}

// ---------- 真实基线：分层抽样 ----------

func pctBand(d detailRow) string {
	switch {
	case d.percentage <= 25:
		return "pct<=25"
	case d.percentage <= 50:
		return "pct26-50"
	default:
		return "pct>50"
	}
}

func sizeBand(elig int) string {
	switch {
	case elig <= 1:
		return "n1"
	case elig <= 5:
		return "n2-5"
	default:
		return "n6+"
	}
}

// BuildRealCases 按「percentage 区间 × 人数区间」分层抽样 n 条真实基线。
//
// 分层而不是取前 n 条：前 n 条集中在某个校区/某位老师，会给出"看起来很整齐"的假结论。
func BuildRealCases(records []recordRow, r *refs, n int, now time.Time) []Case {
	buckets := map[string][]caseFacts{}
	var keys []string
	for _, rec := range records {
		if rec.status != 2 {
			continue // 已结课
		}
		f := r.buildFacts(rec, now)
		if !f.hit || f.agg.sumCost <= 0 || f.agg.elig <= 0 {
			continue // 无命中 / 无收入 / 无有效学生 ⇒ 不进基线
		}
		k := pctBand(f.rule) + "|" + sizeBand(f.agg.elig)
		if _, ok := buckets[k]; !ok {
			keys = append(keys, k)
		}
		buckets[k] = append(buckets[k], f)
	}
	sort.Strings(keys)

	// 桶内按 record id 排序（稳定），桶间轮转取数 ⇒ 分层且可复现
	for _, k := range keys {
		sort.Slice(buckets[k], func(i, j int) bool { return buckets[k][i].rec.id < buckets[k][j].rec.id })
	}
	var out []Case
	idx := make([]int, len(keys))
	for len(out) < n {
		progressed := false
		for bi, k := range keys {
			if idx[bi] >= len(buckets[k]) {
				continue
			}
			f := buckets[k][idx[bi]]
			idx[bi]++
			progressed = true
			out = append(out, Case{
				ID:         fmt.Sprintf("real-%04d", len(out)+1),
				Kind:       KindReal,
				Category:   CatBaseline,
				RecordID:   f.rec.id,
				ExpectTier: f.tier,
				Expectation: fmt.Sprintf("分层桶 %s，期望 %s 命中；income=%.3f，人数=%d",
					k, f.tier, f.agg.sumCost, f.agg.elig),
				Note: "真实基线：status=2 且 income>0 且有规则命中",
			})
			if len(out) >= n {
				break
			}
		}
		if !progressed {
			break
		}
	}
	return out
}

// ---------- 合成边界 ----------

// synPool 收集某一特征下的候选 record（按 id 升序，保证可复现）。
type synPool struct {
	facts []caseFacts
}

func (r *refs) collect(records []recordRow, now time.Time, pred func(caseFacts) bool) []caseFacts {
	var out []caseFacts
	for _, rec := range records {
		f := r.buildFacts(rec, now)
		if pred(f) {
			out = append(out, f)
		}
	}
	sort.Slice(out, func(i, j int) bool { return out[i].rec.id < out[j].rec.id })
	return out
}

// insertRuleSQL 造一条规则（事务内插入，随回滚消失）。
func insertRuleSQL(paymentID int64, classType, classifyID, teacherID int64, teacherCert int, pct, minPay, maxPay, reward float64, expMin, expMax float64, name string) string {
	return fmt.Sprintf("INSERT INTO t_course_payment_detail "+
		"(course_paymentid, gradeid, subjectid, class_type, classifyid, teacherid, name, percentage, min_payment, max_payment, reward, teacher_cert, teacher_exp_min, teacher_exp_max, actived) "+
		"VALUES (%d, -1, -1, %d, %d, %d, '%s', %.1f, %.1f, %.1f, %.1f, b'%d', %.3f, %.3f, b'1')",
		paymentID, classType, classifyID, teacherID, name, pct, minPay, maxPay, reward, teacherCert, expMin, expMax)
}

// BuildSyntheticCases 造 6 类 × perCat 条合成边界。
//
// 每类 5 条（perCat=5），其中 tier 类覆盖四级兜底：teacher-grade-subject / generic-tier 直接选现成记录，
// teacher-classify / cert-tier 真实命中数为 0，**必须靠事务内造规则**才可能命中（见 P0 §13）。
func BuildSyntheticCases(records []recordRow, r *refs, perCat int, now time.Time) ([]Case, []string) {
	var out []Case
	var notes []string
	used := map[string]bool{}

	baseOK := func(f caseFacts) bool {
		return f.hit && f.agg.sumCost > 0 && f.agg.elig > 0 && f.rec.status == 2 && !used[f.rec.id]
	}
	take := func(pool []caseFacts, n int) []caseFacts {
		var got []caseFacts
		for _, f := range pool {
			if len(got) >= n {
				break
			}
			if used[f.rec.id] {
				continue
			}
			got = append(got, f)
			used[f.rec.id] = true
		}
		return got
	}

	add := func(c Case) { out = append(out, c) }

	// ---- 类 1：四级兜底，**每级各 perCat 条**（默认 5 × 4 = 20 条）----
	//
	// 为什么要每级 5 条而不是凑 5 条：四级是"最担心的未验证路径"（真实数据里两级 0 命中），
	// 造数成本几乎为零；而 1~2 条测不出「有 min 无 max / 无 min 无 max / 有 max 无 min」这类组合差异 ——
	// `min_payment=0 表示不设限` 这个语义正是 D10 踩过的坑。
	tierSpecs := []struct {
		tier string
		pred func(f caseFacts) bool
		note string
	}{
		{TierTeacherGradeSubject, func(f caseFacts) bool {
			return baseOK(f) && f.tier == TierTeacherGradeSubject
		}, "现成记录即命中 teacher-grade-subject（无需造数）"},
		{TierGeneric, func(f caseFacts) bool {
			return baseOK(f) && f.tier == TierGeneric
		}, "现成记录即命中 generic-tier（无需造数）"},
		{TierTeacherClassify, func(f caseFacts) bool {
			return baseOK(f) && f.tier == TierGeneric && f.cls != nil && f.rec.teacherid > 0
		}, "造一条 teacherid=该老师 且 classifyid=该分类 的规则 ⇒ 应命中 teacher-classify"},
		{TierCert, func(f caseFacts) bool {
			return baseOK(f) && f.tier == TierGeneric && f.teacher.cert == 0 && f.cls != nil
		}, "老师置持证 + 造 teacher_cert=1 且教龄 0~99 的通用规则 ⇒ 应命中 cert-tier"},
	}
	for _, spec := range tierSpecs {
		pool := r.collect(records, now, spec.pred)
		got := take(pool, perCat)
		if len(got) < perCat {
			notes = append(notes, fmt.Sprintf("tier-%s：候选只有 %d 条（要求 %d）", spec.tier, len(got), perCat))
		}
		for i, f := range got {
			c := Case{
				ID:   fmt.Sprintf("syn-tier-%s-%d", strings.ReplaceAll(spec.tier, "-", "_"), i+1),
				Kind: KindSynthetic, Category: CatTier, RecordID: f.rec.id,
				ExpectTier: spec.tier, Expectation: spec.note,
				Note: "四级兜底之一（P0 §13：classify / cert 真实命中数为 0，必须造数）",
			}
			payid := r.resolvePayment(f.rec.schoolid, f.rec.campusid, f.rec.startTime)
			switch spec.tier {
			case TierTeacherClassify:
				// 三种 min/max 组合轮转，覆盖「只设 min」「只设 max」「都不设」
				minPay, maxPay := 0.0, 0.0
				switch i % 3 {
				case 0:
					minPay = 80.0
				case 1:
					maxPay = 260.0
				case 2:
					minPay, maxPay = 90.0, 240.0
				}
				c.Mutations = []string{insertRuleSQL(payid, f.cls.classType, f.cls.id, f.rec.teacherid, 0,
					33.0, minPay, maxPay, 0, 0, 99, "ac15-syn-classify")}
				c.Expectation += fmt.Sprintf("（min=%.0f max=%.0f）", minPay, maxPay)
			case TierCert:
				minPay, maxPay := 0.0, 0.0
				switch i % 3 {
				case 0:
					minPay = 70.0
				case 1:
					maxPay = 300.0
				case 2:
					minPay, maxPay = 60.0, 280.0
				}
				c.Mutations = []string{
					fmt.Sprintf("UPDATE t_teacher_information SET teacher_cert = b'1' WHERE teacherid = %d", f.rec.teacherid),
					insertRuleSQL(payid, f.cls.classType, 0, 0, 1, 44.0, minPay, maxPay, 0, 0, 99, "ac15-syn-cert"),
				}
				c.Expectation += fmt.Sprintf("（min=%.0f max=%.0f）", minPay, maxPay)
			}
			add(c)
		}
	}

	// ---- 类 2：income 带 3 位小数，**五种尾数各一条**----
	//
	// 五个尾数分别对应五种收敛方向，缺一种就等于没测：
	//   .333 舍 / .667 入 / .999 跨整数进位 / .005 恰好半分 / .347 保留原样
	tails := []struct {
		total float64
		tail  string
		why   string
	}{
		{100.333, "333", "舍（100.333 → 100.33）"},
		{200.667, "667", "入（200.667 → 200.67）"},
		{299.999, "999", "跨整数进位（299.999 → 300.00），Δincome=+0.001 最易漏"},
		{300.005, "005", "恰好半分（300.005 → 300.01），四舍五入边界"},
		{349.347, "347", "保留原样（349.347 → 349.35）"},
	}
	pool3dpBase := r.collect(records, now, func(f caseFacts) bool {
		return baseOK(f) && f.agg.elig >= 1
	})
	got3dp := take(pool3dpBase, len(tails))
	if len(got3dp) < len(tails) {
		notes = append(notes, fmt.Sprintf("income-3dp：候选只有 %d 条（要求 %d）", len(got3dp), len(tails)))
	}
	for i, f := range got3dp {
		t := tails[i]
		add(Case{
			ID: fmt.Sprintf("syn-income-3dp-%s", t.tail), Kind: KindSynthetic, Category: CatIncome3DP,
			RecordID: f.rec.id, ExpectTier: f.tier,
			Mutations: []string{
				fmt.Sprintf("UPDATE t_courses_record_student SET cost = 0 WHERE recordid = '%s'", f.rec.id),
				fmt.Sprintf("UPDATE t_courses_record_student SET cost = %.3f WHERE recordid = '%s' AND type IN (1,2) ORDER BY studentid LIMIT 1", t.total, f.rec.id),
			},
			Expectation: fmt.Sprintf("事务内把 income 钉成 %.3f（尾数 .%s）：%s ⇒ 迁移后 ΣROUND(cost,2) 与 legacy round(Σ,3) 必不同", t.total, t.tail, t.why),
			Note:        "专门验证 PRECISION-CONVERGENCE 的五个收敛方向",
		})
	}

	// ---- 类 3：income=0 但 student_number>0（min_payment 夹取）----
	poolZero := r.collect(records, now, func(f caseFacts) bool {
		return baseOK(f) && f.rule.minPay > 0 && f.agg.elig > 0
	})
	for i, f := range take(poolZero, perCat) {
		add(Case{ID: fmt.Sprintf("syn-income-zero-min-%d", i+1), Kind: KindSynthetic, Category: CatIncomeZeroMin,
			RecordID:    f.rec.id,
			Mutations:   []string{fmt.Sprintf("UPDATE t_courses_record_student SET cost = 0 WHERE recordid = '%s'", f.rec.id)},
			ExpectTier:  f.tier,
			Expectation: fmt.Sprintf("事务内把 cost 全置 0 ⇒ income=0 但人数=%d>0 ⇒ 应被 min_payment=%.1f 夹取", f.agg.elig, f.rule.minPay),
			Note:        "验证 min 夹取分支；真实数据里 status!=2 的 income=0 记录都走退化分支，不可比"})
	}
	if len(poolZero) < perCat {
		notes = append(notes, fmt.Sprintf("income-zero-min：候选只有 %d 条", len(poolZero)))
	}

	// ---- 类 4：isSupplement 两值都跑 ----
	poolSup := r.collect(records, now, func(f caseFacts) bool {
		return baseOK(f) && f.agg.elig >= 2
	})
	for i, f := range take(poolSup, perCat) {
		add(Case{ID: fmt.Sprintf("syn-supplement-both-%d", i+1), Kind: KindSynthetic, Category: CatSupplement,
			RecordID: f.rec.id, BothSupplement: true, ExpectTier: f.tier,
			Expectation: "同一 record 跑 isSupplement=false / true 各一次；record 级应相同，逐行级应如 R13 所述不同",
			Note:        "验证 isSupplement 只控制「是否重写逐行」"})
	}
	if len(poolSup) < perCat {
		notes = append(notes, fmt.Sprintf("supplement-both：候选只有 %d 条", len(poolSup)))
	}

	// ---- 类 5：人数不整除（R13）----
	poolNonDiv := r.collect(records, now, func(f caseFacts) bool {
		return baseOK(f) && f.agg.elig >= 2 && nondivisible(f.agg.sumCost, f.rule, f.agg.elig)
	})
	for i, f := range take(poolNonDiv, perCat) {
		add(Case{ID: fmt.Sprintf("syn-nondivisible-%d", i+1), Kind: KindSynthetic, Category: CatNonDivisible,
			RecordID: f.rec.id, ExpectTier: f.tier,
			Expectation: fmt.Sprintf("总额/人数 不整除（人数=%d）⇒ PHP 每行 round(,3) 与 Go 分位分配必然不同", f.agg.elig),
			Note:        "专门验证 R13，逐行不参与通过判定"})
	}
	if len(poolNonDiv) < perCat {
		notes = append(notes, fmt.Sprintf("nondivisible：候选只有 %d 条", len(poolNonDiv)))
	}

	// ---- 类 6：rewardType=2 固定课酬（人数 1/6/9 + 2 条补充）----
	wantSizes := []int{1, 6, 9, 3, 7}
	for _, want := range wantSizes {
		pool := r.collect(records, now, func(f caseFacts) bool {
			return f.rec.status == 2 && f.agg.elig == want && f.hit && !used[f.rec.id]
		})
		got := take(pool, 1)
		if len(got) != 1 {
			notes = append(notes, fmt.Sprintf("rewardtype2 人数=%d：无法造数（找不到 elig=%d 且有命中的记录）", want, want))
			continue
		}
		f := got[0]
		add(Case{ID: fmt.Sprintf("syn-rewardtype2-n%d", want), Kind: KindSynthetic, Category: CatRewardType2,
			RecordID:    f.rec.id,
			Mutations:   []string{fmt.Sprintf("UPDATE t_courses_record SET teacher_reward_type = 2 WHERE id = '%s'", f.rec.id)},
			ExpectTier:  f.tier,
			Expectation: fmt.Sprintf("置 teacher_reward_type=2（人数=%d）⇒ 按 makeupCost 查表，>6 人应取 'max'=>200", f.agg.elig),
			Note:        "验证固定课酬查表与超表兜底"})
	}

	return out, notes
}

// hasThirdDecimal 判断金额是否有第三位小数（即迁移 3→2 位会变）。
func hasThirdDecimal(v float64) bool {
	milli := int64(v*1000 + 0.5*signOf(v))
	return milli%10 != 0
}

func signOf(v float64) float64 {
	if v < 0 {
		return -1
	}
	return 1
}

// nondivisible 判断"课酬总额 / 人数"在分位是否除不尽（R13 的触发条件）。
func nondivisible(sumCost float64, rule detailRow, n int) bool {
	if n <= 0 || rule.percentage == 0 {
		return false
	}
	reward := sumCost*rule.percentage/100 + rule.reward
	if rule.maxPay > 0 && reward > rule.maxPay {
		reward = rule.maxPay
	} else if rule.minPay > 0 && reward < rule.minPay {
		reward = rule.minPay
	}
	cents := int64(reward*100 + 0.5)
	return cents%int64(n) != 0
}

// tierLabel 把 refs 的内部层级名转成报告用词（保持与 SP 一致）。
func tierLabel(t string) string {
	switch t {
	case TierTeacherClassify, TierTeacherGradeSubject, TierCert, TierGeneric, TierDegraded:
		return t
	case "":
		return TierNone
	default:
		return t
	}
}

// String 便于调试输出。
func (f caseFacts) String() string {
	return strings.Join([]string{
		f.rec.id,
		fmt.Sprintf("tier=%s", f.tier),
		fmt.Sprintf("income=%.3f", f.agg.sumCost),
		fmt.Sprintf("elig=%d", f.agg.elig),
	}, " ")
}