package api

import (
	"encoding/json"
	"fmt"
	"math"
	"math/rand"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"

	"eai_agentplatform/backend/internal/auth"
	"eai_agentplatform/backend/internal/middleware"
	"eai_agentplatform/backend/internal/model"
	"eai_agentplatform/backend/internal/repository"
	"eai_agentplatform/backend/internal/web"
)

// 考试域仓库，包内共享（知识源摄入也会写题目，见 knowledge.go）。
var (
	mistakeRepo    repository.MistakeRecordRepo
	questionRepo   repository.QuestionRepo
	paperRepo      repository.ExamPaperRepo
	examRecordRepo repository.ExamRecordRepo
)

func init() {
	mistakeRepo = repository.MistakeRecordRepo{}
	questionRepo = repository.QuestionRepo{}
	paperRepo = repository.ExamPaperRepo{}
	examRecordRepo = repository.ExamRecordRepo{}
}

// Option 题目选项
type Option struct {
	Key  string `json:"key"`
	Text string `json:"text"`
}

type questionReq struct {
	Domain      string   `json:"domain"`
	CourseID    *uint    `json:"course_id"`
	Type        string   `json:"type"`
	Stem        string   `json:"stem"`
	Options     []Option `json:"options"`
	Answer      []string `json:"answer"`
	Explanation string   `json:"explanation"`
}

var validDomains = map[string]bool{"company": true, "product": true, "sales": true}
var validQTypes = map[string]bool{"single": true, "multiple": true, "judge": true, "essay": true}

// questionView 题目出参（options/answer 反序列化为对象）
func questionView(q model.Question) gin.H {
	var opts []Option
	_ = json.Unmarshal([]byte(q.Options), &opts)
	if opts == nil {
		opts = []Option{}
	}
	var ans []string
	_ = json.Unmarshal([]byte(q.Answer), &ans)
	if ans == nil {
		ans = []string{}
	}
	return gin.H{
		"id":          q.ID,
		"domain":      q.Domain,
		"course_id":   q.CourseID,
		"type":        q.Type,
		"stem":        q.Stem,
		"options":     opts,
		"answer":      ans,
		"explanation": q.Explanation,
		"status":      q.Status,
	}
}

// ============ 题库 CRUD（管理员） ============

// ListQuestions GET /api/exam/questions?domain=&status=
func ListQuestions(c *gin.Context) {
	// 管理端题库：status 缺省要看到全部（含已停用），按约定传 "all"
	items := questionRepo.List(c.Query("domain"), orDefault(c.Query("status"), "all"))
	out := make([]gin.H, 0, len(items))
	for _, it := range items {
		out = append(out, questionView(it))
	}
	web.OK(c, out)
}

// CreateQuestion POST /api/exam/questions (admin)
func CreateQuestion(c *gin.Context) {
	var req questionReq
	if err := c.ShouldBindJSON(&req); err != nil {
		web.Fail(c, web.NewBadRequest("请求参数错误"))
		return
	}
	if !validDomains[req.Domain] || !validQTypes[req.Type] || req.Stem == "" || len(req.Answer) == 0 {
		web.Fail(c, web.NewBadRequest("domain/type/stem/answer 必填且合法"))
		return
	}
	if (req.Type == "single" || req.Type == "multiple") && len(req.Options) == 0 {
		web.Fail(c, web.NewBadRequest("单选题/多选题必须提供选项"))
		return
	}
	optsJSON, _ := json.Marshal(req.Options)
	ansJSON, _ := json.Marshal(req.Answer)
	q := model.Question{
		Domain:      req.Domain,
		CourseID:    req.CourseID,
		Type:        req.Type,
		Stem:        req.Stem,
		Options:     string(optsJSON),
		Answer:      string(ansJSON),
		Explanation: req.Explanation,
		Status:      "active",
	}
	if !questionRepo.Insert(&q) {
		web.Fail(c, web.NewBadRequest("创建题目失败"))
		return
	}
	web.OK(c, questionView(q))
}

// UpdateQuestion PUT /api/exam/questions/{id} (admin)
func UpdateQuestion(c *gin.Context) {
	id, ok := parseID(c, "id")
	if !ok {
		return
	}
	q, found := questionRepo.GetByID(id)
	if !found {
		web.Fail(c, web.NewNotFoundError("题目不存在"))
		return
	}
	var req questionReq
	if err := c.ShouldBindJSON(&req); err != nil {
		web.Fail(c, web.NewBadRequest("请求参数错误"))
		return
	}
	if !validDomains[req.Domain] || !validQTypes[req.Type] || req.Stem == "" || len(req.Answer) == 0 {
		web.Fail(c, web.NewBadRequest("domain/type/stem/answer 必填且合法"))
		return
	}
	if (req.Type == "single" || req.Type == "multiple") && len(req.Options) == 0 {
		web.Fail(c, web.NewBadRequest("单选题/多选题必须提供选项"))
		return
	}
	optsJSON, _ := json.Marshal(req.Options)
	ansJSON, _ := json.Marshal(req.Answer)
	q.Domain = req.Domain
	q.CourseID = req.CourseID
	q.Type = req.Type
	q.Stem = req.Stem
	q.Options = string(optsJSON)
	q.Answer = string(ansJSON)
	q.Explanation = req.Explanation
	if !questionRepo.Update(&q) {
		web.Fail(c, web.NewBadRequest("更新题目失败"))
		return
	}
	web.OK(c, questionView(q))
}

// DeleteQuestion DELETE /api/exam/questions/{id} (admin) —— 软删除
func DeleteQuestion(c *gin.Context) {
	id, ok := parseID(c, "id")
	if !ok {
		return
	}
	if _, found := questionRepo.GetByID(id); !found {
		web.Fail(c, web.NewNotFoundError("题目不存在"))
		return
	}
	if !questionRepo.Delete(id) {
		web.Fail(c, web.NewBadRequest("停用题目失败"))
		return
	}
	web.OK(c, gin.H{"id": id, "status": "inactive"})
}

// ============ 考试配置 CRUD（管理员） ============

// ListPapers GET /api/exam/papers
func ListPapers(c *gin.Context) {
	web.OK(c, paperRepo.List())
}

// CreatePaper POST /api/exam/papers (admin)
func CreatePaper(c *gin.Context) {
	var p model.ExamPaper
	if err := c.ShouldBindJSON(&p); err != nil {
		web.Fail(c, web.NewBadRequest("请求参数错误"))
		return
	}
	if p.Name == "" || (p.Type != "self_test" && p.Type != "formal") || p.QuestionCount <= 0 || p.TotalScore <= 0 || p.PassScore < 0 {
		web.Fail(c, web.NewBadRequest("考试名称/类型/题量/总分/合格线必填且合法"))
		return
	}
	if !validatePaperPosition(c, p.PositionID) {
		return
	}
	if !validatePaperBlueprintCount(c, p) {
		return
	}
	p.Status = "active"
	if !paperRepo.Insert(&p) {
		web.Fail(c, web.NewBadRequest("创建考试失败"))
		return
	}
	web.OK(c, p)
}

// UpdatePaper PUT /api/exam/papers/{id} (admin)
func UpdatePaper(c *gin.Context) {
	id, ok := parseID(c, "id")
	if !ok {
		return
	}
	p, found := paperRepo.GetByID(id)
	if !found {
		web.Fail(c, web.NewNotFoundError("考试配置不存在"))
		return
	}
	var req model.ExamPaper
	if err := c.ShouldBindJSON(&req); err != nil {
		web.Fail(c, web.NewBadRequest("请求参数错误"))
		return
	}
	if req.Name == "" || (req.Type != "self_test" && req.Type != "formal") || req.QuestionCount <= 0 || req.TotalScore <= 0 {
		web.Fail(c, web.NewBadRequest("考试名称/类型/题量/总分必填且合法"))
		return
	}
	if !validatePaperPosition(c, req.PositionID) {
		return
	}
	if !validatePaperBlueprintCount(c, req) {
		return
	}
	p.Name = req.Name
	p.Type = req.Type
	p.Domain = req.Domain
	p.QuestionCount = req.QuestionCount
	p.TotalScore = req.TotalScore
	p.PassScore = req.PassScore
	p.DurationMinutes = req.DurationMinutes
	p.Randomize = req.Randomize
	p.PositionID = req.PositionID
	if req.Status != "" {
		p.Status = req.Status
	}
	if !paperRepo.Update(&p) {
		web.Fail(c, web.NewBadRequest("更新考试失败"))
		return
	}
	web.OK(c, p)
}

// DeletePaper DELETE /api/exam/papers/{id} (admin) —— 软删除
func DeletePaper(c *gin.Context) {
	id, ok := parseID(c, "id")
	if !ok {
		return
	}
	if _, found := paperRepo.GetByID(id); !found {
		web.Fail(c, web.NewNotFoundError("考试配置不存在"))
		return
	}
	if !paperRepo.Delete(id) {
		web.Fail(c, web.NewBadRequest("停用考试失败"))
		return
	}
	web.OK(c, gin.H{"id": id, "status": "inactive"})
}

// ============ 学员端考试 ============

// ExamList GET /api/exam/list —— 我的考试列表（含完成状态）
func ExamList(c *gin.Context) {
	u := middleware.CurrentUser(c)
	items := paperRepo.GetActive()

	type row struct {
		ID              uint   `json:"id"`
		Name            string `json:"name"`
		Type            string `json:"type"`
		Domain          string `json:"domain"`
		QuestionCount   int    `json:"question_count"`
		TotalScore      int    `json:"total_score"`
		PassScore       int    `json:"pass_score"`
		DurationMinutes int    `json:"duration_minutes"`
		Status          string `json:"status"` // available / completed
	}
	out := make([]row, 0, len(items))
	for _, p := range items {
		st := "available"
		if p.Type == "formal" && u != nil && examRecordRepo.HasTaken(u.ID, p.ID) {
			st = "completed"
		}
		out = append(out, row{
			ID: p.ID, Name: p.Name, Type: p.Type, Domain: p.Domain,
			QuestionCount: p.QuestionCount, TotalScore: p.TotalScore,
			PassScore: p.PassScore, DurationMinutes: p.DurationMinutes, Status: st,
		})
	}
	web.OK(c, out)
}

// ExamCover GET /api/exam/cover?paper_id={paper_id}
func ExamCover(c *gin.Context) {
	id64, err := strconv.ParseUint(c.Query("paper_id"), 10, 64)
	if err != nil || id64 == 0 {
		web.Fail(c, web.NewBadRequest("无效的 id"))
		return
	}
	id := uint(id64)
	p, found := paperRepo.GetByID(id)
	if !found || p.Status != "active" {
		web.Fail(c, web.NewNotFoundError("考试不存在或已停用"))
		return
	}
	web.OK(c, gin.H{
		"id": p.ID, "name": p.Name, "type": p.Type, "domain": p.Domain,
		"question_count": p.QuestionCount, "total_score": p.TotalScore,
		"pass_score": p.PassScore, "duration_minutes": p.DurationMinutes,
	})
}

// positionScope 把岗位知识映射折算成抽题范围：知识域集合 + 课程集合。
//
// 岗位考试的两种抽题路径（直接抽 / 按蓝图抽）共用同一份口径，避免两处各写一遍。
func positionScope(pks []model.PositionKnowledge) ([]string, []uint) {
	domains := make([]string, 0, len(pks))
	courseIDs := make([]uint, 0, len(pks))
	for _, pk := range pks {
		domains = append(domains, pk.Domain)
		if pk.CourseID != nil {
			courseIDs = append(courseIDs, *pk.CourseID)
		}
	}
	return dedupeStrings(domains), dedupeUints(courseIDs)
}

// pickQuestions 按 paper 抽题：岗位有蓝图优先按蓝图，否则岗位知识映射圈定题池，再否则回退 domain 抽题
func pickQuestions(p model.ExamPaper) ([]model.Question, error) {
	var domains []string
	var courseIDs []uint
	if p.PositionID != nil {
		// 岗位考试：优先蓝图，其次岗位知识映射
		if bps := positionRepo.Blueprints(*p.PositionID); len(bps) > 0 {
			return pickQuestionsByBlueprint(p, bps)
		}
		// 岗位考试：圈定岗位应学范围
		domains, courseIDs = positionScope(positionRepo.Knowledge(*p.PositionID))
	} else {
		// 原有逻辑：按 exam_paper.domain 抽题
		domains = splitDomains(p.Domain)
	}

	var qs []model.Question
	if !questionRepo.ActivePool(domains, courseIDs).Order("id ASC").Find(&qs) {
		return nil, fmt.Errorf("查询题库失败")
	}
	if len(qs) < p.QuestionCount {
		return nil, fmt.Errorf("题库题目不足：需要 %d，可用 %d", p.QuestionCount, len(qs))
	}
	if p.Randomize {
		rand.Shuffle(len(qs), func(i, j int) { qs[i], qs[j] = qs[j], qs[i] })
	}
	return qs[:p.QuestionCount], nil
}

// pickQuestionsByBlueprint 按岗位考试蓝图逐条抽题：先在岗位应学范围内，再按 (domain, type) 细分抽样。
func pickQuestionsByBlueprint(p model.ExamPaper, bps []model.PositionExamBlueprint) ([]model.Question, error) {
	// 圈定岗位应学范围（与 P0 岗位知识映射抽题一致）
	domains, courseIDs := positionScope(positionRepo.Knowledge(*p.PositionID))
	base := questionRepo.ActivePool(domains, courseIDs)

	out := make([]model.Question, 0, p.QuestionCount)
	used := map[uint]bool{}
	for _, bp := range bps {
		q := base.Where("type = ?", bp.Type)
		if bp.Domain != "" {
			q = q.Where("domain = ?", bp.Domain)
		}
		var pool []model.Question
		if !q.Order("id ASC").Find(&pool) {
			return nil, fmt.Errorf("查询题库失败")
		}
		// 排除已抽中的题，避免重复
		candidates := make([]model.Question, 0, len(pool))
		for _, qq := range pool {
			if !used[qq.ID] {
				candidates = append(candidates, qq)
			}
		}
		if len(candidates) < bp.Count {
			domainLabel := bp.Domain
			if domainLabel == "" {
				domainLabel = "不限"
			}
			return nil, fmt.Errorf("蓝图[域 %s / 题型 %s]题目不足：需要 %d，可用 %d", domainLabel, bp.Type, bp.Count, len(candidates))
		}
		if p.Randomize {
			rand.Shuffle(len(candidates), func(i, j int) { candidates[i], candidates[j] = candidates[j], candidates[i] })
		}
		for i := 0; i < bp.Count; i++ {
			out = append(out, candidates[i])
			used[candidates[i].ID] = true
		}
	}
	if len(out) < p.QuestionCount {
		return nil, fmt.Errorf("蓝图抽题总数不足：需要 %d，蓝图提供 %d", p.QuestionCount, len(out))
	}
	if len(out) > p.QuestionCount {
		out = out[:p.QuestionCount]
	}
	if p.Randomize {
		rand.Shuffle(len(out), func(i, j int) { out[i], out[j] = out[j], out[i] })
	}
	return out, nil
}

// dedupeStrings 去重并保持顺序
func dedupeStrings(in []string) []string {
	seen := make(map[string]bool, len(in))
	out := make([]string, 0, len(in))
	for _, s := range in {
		if s != "" && !seen[s] {
			seen[s] = true
			out = append(out, s)
		}
	}
	return out
}

// dedupeUints 去重并保持顺序
func dedupeUints(in []uint) []uint {
	seen := make(map[uint]bool, len(in))
	out := make([]uint, 0, len(in))
	for _, v := range in {
		if !seen[v] {
			seen[v] = true
			out = append(out, v)
		}
	}
	return out
}

// validatePaperPosition 校验岗位考试：岗位必须存在且已配置知识映射
func validatePaperPosition(c *gin.Context, positionID *uint) bool {
	if positionID == nil {
		return true
	}
	pos, found := positionRepo.GetByID(*positionID)
	if !found || pos.Status != "active" {
		web.Fail(c, web.NewBadRequest("关联岗位不存在或已停用"))
		return false
	}
	if positionRepo.CountKnowledge(*positionID) == 0 {
		web.Fail(c, web.NewBadRequest("岗位考试必须先配置岗位知识映射"))
		return false
	}
	return true
}

// validatePaperBlueprintCount 校验岗位考试蓝图题量不小于试卷题量（蓝图存在时）。
func validatePaperBlueprintCount(c *gin.Context, p model.ExamPaper) bool {
	if p.PositionID == nil {
		return true
	}
	bps := positionRepo.Blueprints(*p.PositionID)
	if len(bps) == 0 {
		return true
	}
	sum := 0
	for _, bp := range bps {
		sum += bp.Count
	}
	if sum < p.QuestionCount {
		web.Fail(c, web.NewBadRequest(fmt.Sprintf("岗位考试蓝图题量(%d)小于试卷题量(%d)，请调整蓝图或题量", sum, p.QuestionCount)))
		return false
	}
	return true
}

func splitDomains(s string) []string {
	var out []string
	for _, d := range strings.Split(s, ",") {
		d = strings.TrimSpace(d)
		if d != "" {
			out = append(out, d)
		}
	}
	return out
}

// ExamStart POST /api/exam/start —— 下发题目，返回无状态会话
func ExamStart(c *gin.Context) {
	u := middleware.CurrentUser(c)
	var req struct {
		PaperID uint `json:"paper_id"`
	}
	if err := c.ShouldBindJSON(&req); err != nil || req.PaperID == 0 {
		web.Fail(c, web.NewBadRequest("paper_id 必填"))
		return
	}
	p, found := paperRepo.GetByID(req.PaperID)
	if !found || p.Status != "active" {
		web.Fail(c, web.NewNotFoundError("考试不存在或已停用"))
		return
	}
	if p.Type == "formal" && u != nil && examRecordRepo.HasTaken(u.ID, p.ID) {
		web.Fail(c, web.NewConflictError("已参加过该正式考试"))
		return
	}
	questions, err := pickQuestions(p)
	if err != nil {
		web.Fail(c, web.NewBadRequest(err.Error()))
		return
	}

	ids := make([]string, len(questions))
	for i, q := range questions {
		ids[i] = strconv.FormatUint(uint64(q.ID), 10)
	}
	now := time.Now()
	session, err := auth.SignClaims(jwt.MapClaims{
		"uid":  u.ID,
		"pid":  p.ID,
		"type": p.Type,
		"qids": strings.Join(ids, ","),
		"iat":  now.Unix(),
		"exp":  now.Add(time.Duration(p.DurationMinutes+5) * time.Minute).Unix(),
	}, Cfg.JWTSecret)
	if err != nil {
		web.Fail(c, web.NewBadRequest("生成考试会话失败"))
		return
	}

	type qView struct {
		ID      uint     `json:"id"`
		Order   int      `json:"order"`
		Type    string   `json:"type"`
		Stem    string   `json:"stem"`
		Options []Option `json:"options"`
	}
	qs := make([]qView, 0, len(questions))
	for i, q := range questions {
		var opts []Option
		_ = json.Unmarshal([]byte(q.Options), &opts)
		if opts == nil {
			opts = []Option{}
		}
		qs = append(qs, qView{ID: q.ID, Order: i + 1, Type: q.Type, Stem: q.Stem, Options: opts})
	}

	web.OK(c, gin.H{
		"session_id":     session,
		"exam_name":      p.Name,
		"time_limit_min": p.DurationMinutes,
		"questions":      qs,
	})
}

// normalizeUserAnswer 把提交的答案规整为 string 或 []string
func normalizeUserAnswer(v any) any {
	switch t := v.(type) {
	case string:
		return t
	case bool:
		return strconv.FormatBool(t)
	case []string:
		return t
	case []any:
		s := make([]string, len(t))
		for i, e := range t {
			s[i] = fmt.Sprintf("%v", e)
		}
		return s
	case nil:
		return nil
	default:
		return fmt.Sprintf("%v", v)
	}
}

func sortedEqual(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}
	aa := append([]string(nil), a...)
	bb := append([]string(nil), b...)
	sort.Strings(aa)
	sort.Strings(bb)
	for i := range aa {
		if aa[i] != bb[i] {
			return false
		}
	}
	return true
}

// isCorrect 判分（对齐 BE02 _is_correct）
func isCorrect(qtype string, correct []string, user any) bool {
	switch qtype {
	case "multiple":
		us, ok := user.([]string)
		if !ok || len(us) != len(correct) {
			return false
		}
		return sortedEqual(correct, us)
	case "judge":
		us, ok := user.(string)
		if !ok || len(correct) == 0 {
			return false
		}
		return strings.EqualFold(correct[0], us)
	default: // single
		us, ok := user.(string)
		if !ok || len(correct) == 0 {
			return false
		}
		return correct[0] == us
	}
}

type questionDetail struct {
	QuestionID    uint     `json:"question_id"`
	Stem          string   `json:"stem"`
	Type          string   `json:"type"`
	UserAnswer    any      `json:"user_answer"`
	CorrectAnswer []string `json:"correct_answer"`
	IsCorrect     bool     `json:"is_correct"`
	ScoreRate     *float64 `json:"score_rate"` // essay 专用：0~1 得分率，其余题型为 null
	Comment       string   `json:"comment"`    // essay 专用：LLM 评语
	Explanation   string   `json:"explanation"`
}

// ExamSubmit POST /api/exam/submit —— 交卷判分
func ExamSubmit(c *gin.Context) {
	u := middleware.CurrentUser(c)
	var req struct {
		SessionID    string         `json:"session_id"`
		Answers      map[string]any `json:"answers"`
		TimeSpentSec int            `json:"time_spent_sec"`
	}
	if err := c.ShouldBindJSON(&req); err != nil || req.SessionID == "" {
		web.Fail(c, web.NewBadRequest("session_id 必填"))
		return
	}
	claims, err := auth.ParseToken(req.SessionID, Cfg.JWTSecret)
	if err != nil {
		web.Fail(c, web.NewAuthError("考试会话无效或已过期"))
		return
	}
	pid, _ := claims["pid"].(float64)
	qidsStr, _ := claims["qids"].(string)
	stype, _ := claims["type"].(string)
	sessUID, _ := claims["uid"].(float64)

	// 会话与当前用户绑定，防止跨用户使用他人会话交卷
	if u == nil || uint(sessUID) != u.ID {
		web.Fail(c, web.NewForbiddenError("考试会话与当前用户不匹配"))
		return
	}

	// 错题重练：无试卷、即时判分，答对即掌握对应错题
	if stype == "re_practice" {
		ids := splitIDs(qidsStr)
		if len(ids) == 0 {
			web.Fail(c, web.NewBadRequest("练习会话无题目"))
			return
		}
		qs := questionRepo.ListByIDs(ids)
		qmap := make(map[uint]model.Question, len(qs))
		for _, q := range qs {
			qmap[q.ID] = q
		}
		correctCount := 0
		scoreRateSum := 0.0
		details := make([]questionDetail, 0, len(ids))
		for _, qid := range ids {
			q, exists := qmap[qid]
			if !exists {
				continue
			}
			var correct []string
			_ = json.Unmarshal([]byte(q.Answer), &correct)
			userAns := normalizeUserAnswer(req.Answers[strconv.FormatUint(uint64(qid), 10)])

			ok := false
			rate := 0.0
			comment := ""
			if q.Type == "essay" {
				rubric := strings.Join(correct, "\n")
				userText := ""
				if s, isStr := userAns.(string); isStr {
					userText = s
				}
				r, cmt, err := gradeEssay(u.ID, q.Stem, rubric, userText)
				if err != nil {
					r = 0
					cmt = "评分失败：" + err.Error()
				}
				rate = r
				comment = cmt
				ok = rate >= 0.6
			} else {
				ok = isCorrect(q.Type, correct, userAns)
				if ok {
					rate = 1
				}
			}

			if ok {
				correctCount++
			}
			scoreRateSum += rate

			var scoreRate *float64
			if q.Type == "essay" {
				v := rate
				scoreRate = &v
			}
			details = append(details, questionDetail{
				QuestionID: qid, Stem: q.Stem, Type: q.Type,
				UserAnswer: userAns, CorrectAnswer: correct, IsCorrect: ok,
				ScoreRate: scoreRate, Comment: comment, Explanation: q.Explanation,
			})

			touchMistakeOnPractice(u.ID, qid, q, userAns, correct, ok)
		}

		total := len(ids)
		score := 0
		if total > 0 {
			score = int(math.Round(100 * scoreRateSum / float64(total)))
		}
		web.OK(c, gin.H{
			"session_id":    req.SessionID,
			"exam_name":     "错题重练",
			"score":         score,
			"total_score":   100,
			"pass_score":    0,
			"passed":        correctCount == total,
			"correct_count": correctCount,
			"wrong_count":   total - correctCount,
			"detail":        details,
		})
		return
	}

	p, found := paperRepo.GetByID(uint(pid))
	if !found {
		web.Fail(c, web.NewNotFoundError("考试不存在"))
		return
	}

	// 正式考不可重复交卷
	if stype == "formal" && u != nil && examRecordRepo.HasTaken(u.ID, p.ID) {
		web.Fail(c, web.NewConflictError("已参加过该正式考试"))
		return
	}

	ids := splitIDs(qidsStr)
	if len(ids) == 0 {
		web.Fail(c, web.NewBadRequest("考试会话无题目"))
		return
	}
	questions := questionRepo.ListByIDs(ids)
	qmap := make(map[uint]model.Question, len(questions))
	for _, q := range questions {
		qmap[q.ID] = q
	}

	correctCount := 0
	scoreRateSum := 0.0
	details := make([]questionDetail, 0, len(ids))
	for _, qid := range ids {
		q, exists := qmap[qid]
		if !exists {
			continue
		}
		var correct []string
		_ = json.Unmarshal([]byte(q.Answer), &correct)
		userAns := normalizeUserAnswer(req.Answers[strconv.FormatUint(uint64(qid), 10)])

		ok := false
		rate := 0.0
		comment := ""
		if q.Type == "essay" {
			// 简答题：LLM 按评分标准打分（0~1 得分率）
			rubric := strings.Join(correct, "\n")
			userText := ""
			if s, isStr := userAns.(string); isStr {
				userText = s
			}
			r, cmt, err := gradeEssay(u.ID, q.Stem, rubric, userText)
			if err != nil {
				// 评分失败：不静默吞掉 —— 0 分 + 可见评语（G02 失败可见、不静默回退）
				r = 0
				cmt = "评分失败：" + err.Error()
			}
			rate = r
			comment = cmt
			ok = rate >= 0.6
		} else {
			ok = isCorrect(q.Type, correct, userAns)
			if ok {
				rate = 1
			}
		}

		if ok {
			correctCount++
		}
		scoreRateSum += rate

		var scoreRate *float64
		if q.Type == "essay" {
			v := rate
			scoreRate = &v
		}
		details = append(details, questionDetail{
			QuestionID: qid, Stem: q.Stem, Type: q.Type,
			UserAnswer: userAns, CorrectAnswer: correct, IsCorrect: ok,
			ScoreRate: scoreRate, Comment: comment, Explanation: q.Explanation,
		})

		// 错题入本（自测/正式均写入，供学员复盘）
		if !ok {
			recordMistake(u.ID, qid, q, userAns, correct, stype)
		}
	}

	total := len(ids)
	score := 0
	if total > 0 {
		score = int(math.Round(float64(p.TotalScore) * scoreRateSum / float64(total)))
	}
	passed := score >= p.PassScore
	wrongCount := total - correctCount

	result := gin.H{
		"session_id":    req.SessionID,
		"exam_name":     p.Name,
		"score":         score,
		"total_score":   p.TotalScore,
		"pass_score":    p.PassScore,
		"passed":        passed,
		"correct_count": correctCount,
		"wrong_count":   wrongCount,
		"detail":        details,
	}

	// 正式考持久化 + 通过发证 + 积分
	if stype == "formal" && u != nil {
		detailJSON, _ := json.Marshal(gin.H{"questions": details, "time_spent_sec": req.TimeSpentSec})
		rec := model.ExamRecord{
			UserID: u.ID, PaperID: p.ID, ExamName: p.Name,
			Score: score, TotalScore: p.TotalScore, PassScore: p.PassScore, Passed: passed,
			CorrectCount: correctCount, WrongCount: wrongCount,
			DetailJSON: string(detailJSON), SubmittedAt: time.Now(),
		}
		examRecordRepo.Insert(&rec)
		if passed {
			awardPoints(u.ID, "formal_pass", ptFormalPass, "paper", p.ID)
			issueCertificate(u, rec)
		}
	} else if stype == "self_test" && u != nil {
		// 自测不落分、不存档（P03），仅计一次练习积分
		awardPoints(u.ID, "self_test", ptSelfTestSubmit, "paper", p.ID)
	}

	web.OK(c, result)
}

func splitIDs(s string) []uint {
	var out []uint
	for _, part := range strings.Split(s, ",") {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		if n, err := strconv.ParseUint(part, 10, 64); err == nil && n > 0 {
			out = append(out, uint(n))
		}
	}
	return out
}

// ExamRecordList GET /api/exam/record?page=&size= —— 我的考试记录
func ExamRecordList(c *gin.Context) {
	u := middleware.CurrentUser(c)
	items := examRecordRepo.ListByUser(u.ID)
	if items == nil {
		items = []model.ExamRecord{}
	}
	web.OK(c, items)
}

// ExamRecordDetail GET /api/exam/record/{record_id} —— 记录详情回溯
func ExamRecordDetail(c *gin.Context) {
	u := middleware.CurrentUser(c)
	id, ok := parseID(c, "record_id")
	if !ok {
		return
	}
	rec, found := examRecordRepo.GetByID(id)
	if !found {
		web.Fail(c, web.NewNotFoundError("考试记录不存在"))
		return
	}
	if u.Role != "admin" && rec.UserID != u.ID {
		web.Fail(c, web.NewForbiddenError("无权查看他人考试记录"))
		return
	}
	var detail any
	_ = json.Unmarshal([]byte(rec.DetailJSON), &detail)
	web.OK(c, gin.H{
		"id": rec.ID, "user_id": rec.UserID, "paper_id": rec.PaperID, "exam_name": rec.ExamName,
		"score": rec.Score, "total_score": rec.TotalScore, "pass_score": rec.PassScore, "passed": rec.Passed,
		"correct_count": rec.CorrectCount, "wrong_count": rec.WrongCount,
		"detail": detail, "submitted_at": rec.SubmittedAt,
	})
}

// ============ 错题本（学员自助） ============

// mistakePayload 组装错题本记录：作答与正确答案以 JSON 落库，
// 与 mistakeView 的反序列化、MyMistakes 的出参形状对齐。
func mistakePayload(userID, questionID uint, source string, q model.Question, userAns any, correct []string) model.MistakeRecord {
	userAnsJSON, _ := json.Marshal(userAns)
	correctJSON, _ := json.Marshal(correct)
	return model.MistakeRecord{
		UserID: userID, QuestionID: questionID, Source: source,
		QuestionType: q.Type, QuestionStem: q.Stem,
		UserAnswer: string(userAnsJSON), CorrectAnswer: string(correctJSON),
		Explanation: q.Explanation,
	}
}

// recordMistake 答错入本：按 (user_id, question_id, source) 去重，再次答错则更新并重置为未掌握。
func recordMistake(userID, questionID uint, q model.Question, userAns any, correct []string, source string) {
	mistakeRepo.RecordWrong(mistakePayload(userID, questionID, source, q, userAns, correct))
}

// mistakeView 错题出参（answer 反序列化，便于前端直接展示）
type mistakeView struct {
	ID            uint      `json:"id"`
	QuestionID    uint      `json:"question_id"`
	Source        string    `json:"source"`
	QuestionType  string    `json:"question_type"`
	QuestionStem  string    `json:"question_stem"`
	UserAnswer    any       `json:"user_answer"`
	CorrectAnswer []string  `json:"correct_answer"`
	Explanation   string    `json:"explanation"`
	Resolved      bool      `json:"resolved"`
	UpdatedAt     time.Time `json:"updated_at"`
}

// MyMistakes GET /api/exam/mistakes —— 我的错题本
func MyMistakes(c *gin.Context) {
	u := middleware.CurrentUser(c)
	items := mistakeRepo.ListByUser(u.ID)
	out := make([]mistakeView, 0, len(items))
	for _, it := range items {
		var userAns any
		_ = json.Unmarshal([]byte(it.UserAnswer), &userAns)
		var correct []string
		_ = json.Unmarshal([]byte(it.CorrectAnswer), &correct)
		if correct == nil {
			correct = []string{}
		}
		out = append(out, mistakeView{
			ID: it.ID, QuestionID: it.QuestionID, Source: it.Source,
			QuestionType: it.QuestionType, QuestionStem: it.QuestionStem,
			UserAnswer: userAns, CorrectAnswer: correct, Explanation: it.Explanation,
			Resolved: it.Resolved, UpdatedAt: it.UpdatedAt,
		})
	}
	web.OK(c, out)
}

// ResolveMistake PUT /api/exam/mistakes/{id}/resolve —— 标记 / 取消「已掌握」
func ResolveMistake(c *gin.Context) {
	u := middleware.CurrentUser(c)
	id, ok := parseID(c, "id")
	if !ok {
		return
	}
	rec, found := mistakeRepo.GetByID(id)
	if !found {
		web.Fail(c, web.NewNotFoundError("错题记录不存在"))
		return
	}
	if rec.UserID != u.ID {
		web.Fail(c, web.NewForbiddenError("无权操作他人错题"))
		return
	}
	var req struct {
		Resolved *bool `json:"resolved"`
	}
	_ = c.ShouldBindJSON(&req)
	target := true
	if req.Resolved != nil {
		target = *req.Resolved
	}
	wasResolved := rec.Resolved
	rec.Resolved = target
	if !mistakeRepo.Update(&rec) {
		web.Fail(c, web.NewBadRequest("更新错题状态失败"))
		return
	}
	// 仅在「未掌握 → 已掌握」时加分，避免反复切换刷分
	if !wasResolved && target {
		awardPoints(u.ID, "mistake_resolved", ptMistakeResolved, "mistake", rec.ID)
	}
	web.OK(c, gin.H{"id": rec.ID, "resolved": rec.Resolved})
}

// MistakePractice POST /api/exam/mistakes/practice —— 错题重练：从错题生成练习会话
func MistakePractice(c *gin.Context) {
	u := middleware.CurrentUser(c)
	if u == nil {
		web.Fail(c, web.NewAuthError("未登录"))
		return
	}
	var req struct {
		Source         string `json:"source"`
		OnlyUnresolved bool   `json:"only_unresolved"`
	}
	_ = c.ShouldBindJSON(&req)

	recs := mistakeRepo.ListForPractice(u.ID, req.Source, req.OnlyUnresolved)
	if len(recs) == 0 {
		web.Fail(c, web.NewBadRequest("暂无可重练的错题"))
		return
	}

	ids := make([]uint, 0, len(recs))
	for _, r := range recs {
		ids = append(ids, r.QuestionID)
	}
	ids = dedupeUints(ids)

	// 剔除已停用/删除的题目，仅下发可作答题目
	questions := questionRepo.ListActiveByIDs(ids)
	if len(questions) == 0 {
		web.Fail(c, web.NewBadRequest("错题对应题目已失效，暂无可重练题目"))
		return
	}

	qidStrs := make([]string, len(questions))
	for i, q := range questions {
		qidStrs[i] = strconv.FormatUint(uint64(q.ID), 10)
	}
	now := time.Now()
	session, err := auth.SignClaims(jwt.MapClaims{
		"uid":  u.ID,
		"type": "re_practice",
		"qids": strings.Join(qidStrs, ","),
		"iat":  now.Unix(),
		"exp":  now.Add(2 * time.Hour).Unix(),
	}, Cfg.JWTSecret)
	if err != nil {
		web.Fail(c, web.NewBadRequest("生成练习会话失败"))
		return
	}

	type qView struct {
		ID      uint     `json:"id"`
		Order   int      `json:"order"`
		Type    string   `json:"type"`
		Stem    string   `json:"stem"`
		Options []Option `json:"options"`
	}
	qs := make([]qView, 0, len(questions))
	for i, q := range questions {
		var opts []Option
		_ = json.Unmarshal([]byte(q.Options), &opts)
		if opts == nil {
			opts = []Option{}
		}
		qs = append(qs, qView{ID: q.ID, Order: i + 1, Type: q.Type, Stem: q.Stem, Options: opts})
	}

	web.OK(c, gin.H{
		"session_id":     session,
		"exam_name":      "错题重练",
		"time_limit_min": 0,
		"questions":      qs,
	})
}

// touchMistakeOnPractice 错题重练判分后同步错题状态：答对置为已掌握（加积分），答错重置为未掌握。
func touchMistakeOnPractice(userID, questionID uint, q model.Question, userAns any, correct []string, resolved bool) {
	payload := mistakePayload(userID, questionID, "", q, userAns, correct)
	flipped, touched := mistakeRepo.TouchOnPractice(payload, resolved)
	if !touched {
		// 防御性兜底：理论上重练题目均来自错题本，这里创建一条
		payload.Source = "re_practice"
		mistakeRepo.RecordWrong(payload)
		return
	}
	// 仅在「未掌握 → 已掌握」时加分，避免反复重练刷分
	for _, id := range flipped {
		awardPoints(userID, "mistake_resolved", ptMistakeResolved, "mistake", id)
	}
}