package httpapi

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/csv"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"unicode/utf8"

	"github.com/xuri/excelize/v2"
	"golang.org/x/text/encoding/simplifiedchinese"
	textunicode "golang.org/x/text/encoding/unicode"
	"golang.org/x/text/transform"

	"git.yeij.top/AskaEth/Scoreboard/server/internal/auth"
	"git.yeij.top/AskaEth/Scoreboard/server/internal/middleware"
)

// ---------- 认证 ----------

func (s *server) login(w http.ResponseWriter, r *http.Request) (any, error) {
	var in loginInput
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	if strings.TrimSpace(in.Username) == "" || in.Password == "" {
		return nil, badRequest("username 与 password 必填", nil)
	}

	ip := middleware.ClientIP(r)
	u, token, err := s.auth.Authenticate(r.Context(), in.Username, in.Password, ip, r.UserAgent())
	switch {
	case err == auth.ErrRateLimited:
		return nil, rateLimited("登录尝试过于频繁，请稍后再试")
	case err == auth.ErrInvalidCredentials, err == auth.ErrUserInactive:
		return nil, unauthorized("AUTH_FAILED", err.Error())
	case err != nil:
		return nil, internal(err)
	}

	s.auth.SetSessionCookie(w, token)
	csrf, err := auth.NewCSRFToken()
	if err != nil {
		return nil, internal(err)
	}
	s.auth.SetCSRFCookie(w, csrf)
	// 登录时请求 ctx 里还是 guest，Auditor 取不到用户，需在审计条目里显式带上 actorID。
	middleware.Record(r.Context(), middleware.AuditEntry{
		Action: "auth.login", EntityType: "user", EntityID: u.ID, ActorID: u.ID,
		After: map[string]any{"username": u.Username},
	})
	return userDTO(u), nil
}

func (s *server) logout(w http.ResponseWriter, r *http.Request) (any, error) {
	if c, err := r.Cookie(auth.CookieSession); err == nil {
		if err := s.auth.Logout(r.Context(), c.Value); err != nil {
			return nil, internal(err)
		}
	}
	s.auth.ClearSessionCookie(w)
	s.auth.ClearCSRFCookie(w)
	return nil, nil
}

func (s *server) me(w http.ResponseWriter, r *http.Request) (any, error) {
	u := middleware.User(r.Context())
	return userDTO(u), nil
}

type changePasswordInput struct {
	CurrentPassword string `json:"currentPassword"`
	NewPassword     string `json:"newPassword"`
}

// changePassword 修改当前登录用户的密码：先验原密码，再改密并作废全部会话。
func (s *server) changePassword(w http.ResponseWriter, r *http.Request) (any, error) {
	u := middleware.User(r.Context())
	if u.Role == auth.RoleGuest {
		return nil, unauthorized("AUTH_REQUIRED", "请先登录")
	}

	var in changePasswordInput
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	if len(in.NewPassword) < 8 {
		return nil, badRequest("新密码至少 8 位", nil)
	}
	if len(in.NewPassword) > auth.MaxPasswordBytes {
		return nil, badRequest(fmt.Sprintf("新密码不能超过 %d 字节", auth.MaxPasswordBytes), nil)
	}
	if in.NewPassword == in.CurrentPassword {
		return nil, badRequest("新密码不能与原密码相同", nil)
	}
	// 会话被盗后不能直接改密，必须再验一次原密码
	if err := s.auth.VerifyPassword(r.Context(), u.ID, in.CurrentPassword); err != nil {
		return nil, unauthorized("AUTH_FAILED", "原密码不正确")
	}
	if err := s.auth.SetPassword(r.Context(), u.Username, in.NewPassword, false); err != nil {
		return nil, internal(err)
	}

	// SetPassword 已作废全部会话，这里清掉 Cookie 让前端引导重新登录
	s.auth.ClearSessionCookie(w)
	s.auth.ClearCSRFCookie(w)
	s.audit(r.Context(), "auth.change_password", "user", u.ID, nil, map[string]any{"username": u.Username})
	return map[string]any{"relogin": true}, nil
}

func userDTO(u *auth.User) currentUserDTO {
	dto := currentUserDTO{
		ID:                 u.ID,
		Username:           u.Username,
		DisplayName:        u.DisplayName,
		Role:               u.Role.String(),
		MustChangePassword: u.MustChangePassword,
	}
	if u.Role == auth.RoleGuest {
		dto.Username = "guest"
		dto.DisplayName = "访客"
	}
	if u.LastLoginAt != "" {
		v := u.LastLoginAt
		dto.LastLoginAt = &v
	}
	return dto
}

// ---------- settings ----------

func (s *server) getSettingsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	return s.getSettings(r.Context())
}

func (s *server) updateSettingsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in settingsPatch
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	return nil, s.idempotent(w, r, in.RequestID, func() (any, error) {
		before, err := s.getSettings(r.Context())
		if err != nil {
			return nil, err
		}
		updated, err := s.updateSettings(r.Context(), in)
		if err != nil {
			return nil, err
		}
		s.audit(r.Context(), "settings.update", "settings", 0, before, updated)
		return updated, nil
	})
}

// ---------- teams ----------

func (s *server) listTeamsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	includeDeleted := isQueryTrue(r, "includeDeleted")
	// 已彻底删除的单位不进任何列表，只有 admin 能用显式开关把它们翻出来排查。
	if includeDeleted && !middleware.User(r.Context()).Role.Allows(auth.RoleAdmin) {
		return nil, forbidden("只有管理员可以查看已彻底删除的单位")
	}
	return s.listTeams(r.Context(), includeDeleted)
}

func (s *server) getTeamHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	t, err := s.getTeam(r.Context(), id)
	if err != nil {
		return nil, err
	}
	// 彻底删除的单位对非 admin 按不存在处理；admin 仍查得到，便于排查。
	if t.DeletedAt != nil && !middleware.User(r.Context()).Role.Allows(auth.RoleAdmin) {
		return nil, notFound("单位不存在")
	}
	return t, nil
}

func (s *server) createTeamHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in teamDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	created, err := s.createTeam(r.Context(), in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "team.create", "team", created.ID, nil, created)
	return created, nil
}

func (s *server) updateTeamHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in teamDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.getTeam(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.updateTeam(r.Context(), id, in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "team.update", "team", id, before, updated)
	return updated, nil
}

// deleteTeamHandler 默认软删除（停用）；带 purge=1 时彻底删除（对界面不可见，行仍在库里）。
func (s *server) deleteTeamHandler(w http.ResponseWriter, r *http.Request) error {
	id, err := pathID(r, "id")
	if err != nil {
		return err
	}
	before, err := s.getTeam(r.Context(), id)
	if err != nil {
		return err
	}
	if !isQueryTrue(r, "purge") {
		if err := s.deleteTeam(r.Context(), id); err != nil {
			return err
		}
		s.audit(r.Context(), "team.delete", "team", id, before, nil)
		return nil
	}
	after, err := s.hideTeam(r.Context(), id)
	if err != nil {
		return err
	}
	// 记清楚这是「隐藏」而不是物理删除：报名、成绩、流水一行没动，审计要能自证。
	s.audit(r.Context(), "team.purge", "team", id, before, map[string]any{
		"hidden": true, "deletedAt": after.DeletedAt,
	})
	return nil
}

// ---------- sports ----------

func (s *server) listSportsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	return s.listSports(r.Context())
}

func (s *server) getSportHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.getSport(r.Context(), id)
}

func (s *server) createSportHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in sportDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	created, err := s.createSport(r.Context(), in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "sport.create", "sport", created.ID, nil, created)
	return created, nil
}

func (s *server) updateSportHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in sportDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.getSport(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.updateSport(r.Context(), id, in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "sport.update", "sport", id, before, updated)
	return updated, nil
}

func (s *server) deleteSportHandler(w http.ResponseWriter, r *http.Request) error {
	id, err := pathID(r, "id")
	if err != nil {
		return err
	}
	before, err := s.getSport(r.Context(), id)
	if err != nil {
		return err
	}
	if err := s.deleteSport(r.Context(), id); err != nil {
		return err
	}
	s.audit(r.Context(), "sport.delete", "sport", id, before, nil)
	return nil
}

// ---------- events ----------

func (s *server) listEventsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	sportID, _ := int64Query(r, "sportId")
	return s.listEvents(r.Context(), sportID)
}

func (s *server) getEventHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.getEvent(r.Context(), id)
}

func (s *server) createEventHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in eventDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	created, err := s.createEvent(r.Context(), in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "event.create", "event", created.ID, nil, created)
	return created, nil
}

func (s *server) updateEventHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in eventDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.getEvent(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.updateEvent(r.Context(), id, in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "event.update", "event", id, before, updated)
	return updated, nil
}

func (s *server) deleteEventHandler(w http.ResponseWriter, r *http.Request) error {
	id, err := pathID(r, "id")
	if err != nil {
		return err
	}
	before, err := s.getEvent(r.Context(), id)
	if err != nil {
		return err
	}
	if err := s.deleteEvent(r.Context(), id); err != nil {
		return err
	}
	s.audit(r.Context(), "event.delete", "event", id, before, nil)
	return nil
}

func (s *server) listEntriesHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.listEntriesWithResults(r.Context(), id)
}

func (s *server) listCategoriesHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.listCategories(r.Context(), id)
}

func (s *server) replaceCategoriesHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in categoriesPayload
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.listCategories(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.replaceCategories(r.Context(), id, in.Categories)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "event.categories.replace", "event", id, before, updated)
	return updated, nil
}

func (s *server) listChannelsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.listChannels(r.Context(), id)
}

func (s *server) replaceChannelsHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in channelsPayload
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.listChannels(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.replaceChannels(r.Context(), id, in.Channels)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "event.channels.replace", "event", id, before, updated)
	return updated, nil
}

// ---------- scoring profiles ----------

func (s *server) listProfilesHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	return s.listProfiles(r.Context())
}

func (s *server) getProfileHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.getProfile(r.Context(), id)
}

func (s *server) createProfileHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in profileDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	created, err := s.createProfile(r.Context(), in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "profile.create", "scoring_profile", created.ID, nil, created)
	return created, nil
}

func (s *server) updateProfileHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in profileDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.getProfile(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.updateProfile(r.Context(), id, in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "profile.update", "scoring_profile", id, before, updated)
	return updated, nil
}

// ---------- athletes ----------

func (s *server) listAthletesHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	teamID, _ := int64Query(r, "teamId")
	return s.listAthletes(r.Context(), teamID)
}

func (s *server) getAthleteHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	return s.getAthlete(r.Context(), id)
}

func (s *server) createAthleteHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in athleteDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	created, err := s.createAthlete(r.Context(), in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "athlete.create", "athlete", created.ID, nil, created)
	return created, nil
}

func (s *server) updateAthleteHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	var in athleteDTO
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	before, err := s.getAthlete(r.Context(), id)
	if err != nil {
		return nil, err
	}
	updated, err := s.updateAthlete(r.Context(), id, in)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "athlete.update", "athlete", id, before, updated)
	return updated, nil
}

// deleteAthleteHandler 默认软删除（停用）；带 purge=1 时物理删除人员、报名、成绩并重算受影响的积分。
func (s *server) deleteAthleteHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	before, err := s.getAthlete(r.Context(), id)
	if err != nil {
		return nil, err
	}
	if !isQueryTrue(r, "purge") {
		if err := s.deleteAthlete(r.Context(), id); err != nil {
			return nil, err
		}
		s.audit(r.Context(), "athlete.delete", "athlete", id, before, nil)
		return nil, nil
	}
	purged, err := s.purgeAthlete(r.Context(), id)
	if err != nil {
		return nil, err
	}
	// 审计带上删除规模与重算过的小项，事后能对上「榜为什么变了」。
	s.audit(r.Context(), "athlete.purge", "athlete", id, before, purged)
	return purged, nil
}

// isQueryTrue 解析开关型查询参数：只认 1 / true（大小写不敏感），其余值一律当 false。
// 写错的值不会误开开关——purge=0、purge=false 都还是软删除。
func isQueryTrue(r *http.Request, key string) bool {
	switch strings.ToLower(strings.TrimSpace(r.URL.Query().Get(key))) {
	case "1", "true":
		return true
	}
	return false
}

// ---------- 报名表导入 ----------

type entryImportResult struct {
	Created   int              `json:"created"`
	Updated   int              `json:"updated"`
	Skipped   int              `json:"skipped"`
	Errors    []string         `json:"errors"`
	Conflicts []importConflict `json:"conflicts"`
}

// importConflict 是「证件号或号码布已存在、但人员字段与库中不一致」的一行。
// 该行本轮不落库，等用户逐条决策后走 /api/entries/import/resolve。
type importConflict struct {
	Row           int               `json:"row"`
	IDCard        string            `json:"idCard"`
	Bib           string            `json:"bib"`
	AthleteID     int64             `json:"athleteId"`
	Existing      importAthleteView `json:"existing"`
	Incoming      importAthleteView `json:"incoming"`
	ChangedFields []string          `json:"changedFields"`
}

// importAthleteView 是冲突两端可比的字段快照（单位用编码，前端好展示）。
type importAthleteView struct {
	Name       string  `json:"name"`
	Gender     *string `json:"gender"`
	TeamCode   string  `json:"teamCode"`
	EmployeeNo *string `json:"employeeNo"`
	IDCard     *string `json:"idCard"`
	Bib        *string `json:"bib"`
	Age        *int    `json:"age"`
}

// importDecision 是冲突决策：keep-existing 保留库中人员字段，keep-new 用表里的字段覆盖。
// 证件号与号码布二选一作为决策键，证件号优先。
type importDecision struct {
	IDCard string `json:"idCard"`
	Bib    string `json:"bib"`
	Action string `json:"action"`
}

const (
	decisionKeepExisting = "keep-existing"
	decisionKeepNew      = "keep-new"
)

// maxEntryImportBytes 是报名表上传的硬上限（16MB 文件 + multipart 开销）。
const maxEntryImportBytes = 32 << 20

// readImportForm 解析报名表上传（multipart file 字段），返回表格行。
func (s *server) readImportForm(w http.ResponseWriter, r *http.Request) ([][]string, error) {
	r.Body = http.MaxBytesReader(w, r.Body, maxEntryImportBytes)
	if err := r.ParseMultipartForm(16 << 20); err != nil {
		return nil, badRequest("上传文件解析失败", err.Error())
	}
	file, header, err := r.FormFile("file")
	if err != nil {
		return nil, badRequest("缺少 file 字段", err.Error())
	}
	defer func() { _ = file.Close() }()
	return readTable(filepath.Ext(header.Filename), file)
}

// importEntriesHandler 解析 CSV/XLSX 报名表；表头见 importColumns。
func (s *server) importEntriesHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	rows, err := s.readImportForm(w, r)
	if err != nil {
		return nil, err
	}
	result, err := s.importEntries(r.Context(), rows)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "entries.import", "entry", 0, nil, result)
	return result, nil
}

// resolveImportHandler 按用户对冲突的逐条决策重跑导入：
// 已决策的冲突按决策落库，未决策的冲突继续留在 conflicts 里返回。
func (s *server) resolveImportHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	rows, err := s.readImportForm(w, r)
	if err != nil {
		return nil, err
	}
	raw := strings.TrimSpace(r.FormValue("decisions"))
	if raw == "" {
		return nil, badRequest("缺少 decisions 字段", nil)
	}
	var decisions []importDecision
	if err := json.Unmarshal([]byte(raw), &decisions); err != nil {
		return nil, badRequest("decisions 不是合法 JSON", err.Error())
	}
	byKey := make(map[string]string, len(decisions))
	for _, d := range decisions {
		if d.Action != decisionKeepExisting && d.Action != decisionKeepNew {
			return nil, badRequest("action 只能是 keep-existing 或 keep-new", d.Action)
		}
		key := strings.TrimSpace(d.IDCard)
		if key == "" {
			key = strings.TrimSpace(d.Bib)
		}
		byKey[key] = d.Action
	}
	result, err := s.importEntriesWith(r.Context(), rows, byKey)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "entries.import.resolve", "entry", 0, nil, result)
	return result, nil
}

// setEntriesHeatHandler 批量设置 / 清除一批报名项的批次（PUT /api/entries/heat）。
func (s *server) setEntriesHeatHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	var in entryHeatPayload
	if err := decodeJSON(r, &in); err != nil {
		return nil, err
	}
	result, err := s.setEntriesHeat(r.Context(), in.EntryIDs, in.Heat)
	if err != nil {
		return nil, err
	}
	s.audit(r.Context(), "entry.heat", "entry", 0, nil,
		map[string]any{"entryIds": result.EntryIDs, "heat": result.Heat, "updated": result.Updated})
	return result, nil
}

func readTable(ext string, file io.Reader) ([][]string, error) {
	switch strings.ToLower(ext) {
	case ".xlsx":
		f, err := excelize.OpenReader(file)
		if err != nil {
			return nil, badRequest("无法解析 xlsx", err.Error())
		}
		defer func() { _ = f.Close() }()
		sheets := f.GetSheetList()
		if len(sheets) == 0 {
			return nil, badRequest("xlsx 没有工作表", nil)
		}
		rows, err := f.GetRows(sheets[0])
		if err != nil {
			return nil, badRequest("读取 xlsx 失败", err.Error())
		}
		return rows, nil
	default:
		text, err := decodeTableText(file)
		if err != nil {
			return nil, err
		}
		reader := csv.NewReader(strings.NewReader(text))
		reader.FieldsPerRecord = -1
		reader.TrimLeadingSpace = true
		rows, err := reader.ReadAll()
		if err != nil {
			return nil, badRequest("无法解析 CSV", err.Error())
		}
		return rows, nil
	}
}

// 报名表文本可能带的字节序标记。
var (
	tableUTF8BOM    = []byte{0xEF, 0xBB, 0xBF}
	tableUTF16LEBOM = []byte{0xFF, 0xFE}
	tableUTF16BEBOM = []byte{0xFE, 0xFF}
)

// decodeTableText 把报名表的字节流解码成 UTF-8 文本。
//
// 现场拿到的 CSV 基本都是直接从 Excel 存的，而 Excel 默认不写 UTF-8：中文 Windows 上
// 「另存为 CSV」出的是 GB18030，「CSV UTF-8」会带 BOM，PowerShell 的 Export-Csv 出 UTF-16LE。
// 这三种原样丢给 csv.Reader 都会炸，而且症状很误导——
// 中文单位名、运动员名变乱码；BOM 会粘在第一列表头上（"\ufeffevent_code"），
// 于是报「报名表缺少列 event_code」，让人以为表头写错了。
func decodeTableText(file io.Reader) (string, error) {
	// 上游 readImportForm 已用 MaxBytesReader 限住 body，整读不会失控。
	data, err := io.ReadAll(file)
	if err != nil {
		return "", badRequest("读取报名表失败", err.Error())
	}

	switch {
	case bytes.HasPrefix(data, tableUTF8BOM):
		data = data[len(tableUTF8BOM):]
	case bytes.HasPrefix(data, tableUTF16LEBOM):
		return decodeUTF16Table(data[len(tableUTF16LEBOM):], textunicode.LittleEndian)
	case bytes.HasPrefix(data, tableUTF16BEBOM):
		return decodeUTF16Table(data[len(tableUTF16BEBOM):], textunicode.BigEndian)
	}

	if utf8.Valid(data) {
		return string(data), nil
	}
	// GBK 是 GB18030 的子集，按 GB18030 解能一并覆盖。
	text, _, err := transform.String(simplifiedchinese.GB18030.NewDecoder(), string(data))
	if err != nil {
		return "", badRequest("报名表编码无法识别，请另存为 UTF-8 或 GB18030 编码的 CSV 后重试", err.Error())
	}
	return text, nil
}

// decodeUTF16Table 解 UTF-16（BOM 已由调用方摘掉）。
func decodeUTF16Table(data []byte, order textunicode.Endianness) (string, error) {
	text, _, err := transform.String(textunicode.UTF16(order, textunicode.IgnoreBOM).NewDecoder(), string(data))
	if err != nil {
		return "", badRequest("报名表编码无法识别，请另存为 UTF-8 编码的 CSV 后重试", err.Error())
	}
	return text, nil
}

// importColumns 是报名表必须包含的表头（大小写不敏感）；
// id_card、gender、age 为可选列，缺列不报错，按空值处理。
var importColumns = []string{
	"event_code", "category", "team_code", "athlete_name", "bib", "seed", "status", "member_names",
}

func (s *server) importEntries(ctx context.Context, rows [][]string) (entryImportResult, error) {
	return s.importEntriesWith(ctx, rows, nil)
}

// importEntriesWith 是导入主体。decisions 为 nil 表示纯导入：冲突只收集不落库；
// 非 nil 时按决策处理证件号/号码布命中的冲突，未出现在 decisions 里的冲突继续收集。
func (s *server) importEntriesWith(ctx context.Context, rows [][]string, decisions map[string]string) (entryImportResult, error) {
	result := entryImportResult{Errors: []string{}, Conflicts: []importConflict{}}
	if len(rows) < 2 {
		return result, badRequest("报名表为空", nil)
	}
	index := make(map[string]int, len(rows[0]))
	for i, h := range rows[0] {
		index[strings.ToLower(strings.TrimSpace(h))] = i
	}
	for _, col := range importColumns {
		if _, ok := index[col]; !ok {
			return result, badRequest("报名表缺少列 "+col, nil)
		}
	}

	// 同一文件里证件号、号码布都只能出现一次，否则无法判断是不是同一个人。
	seenIDCards := make(map[string]bool)
	seenBibs := make(map[string]bool)
	for n, row := range rows[1:] {
		line := n + 2
		cell := func(name string) string {
			i, ok := index[name]
			if !ok || i >= len(row) {
				return ""
			}
			return strings.TrimSpace(row[i])
		}
		eventCode := cell("event_code")
		categoryName := cell("category")
		teamCode := cell("team_code")
		athleteName := cell("athlete_name")
		if eventCode == "" || teamCode == "" {
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line, "event_code / team_code 必填"))
			continue
		}
		// status 先归一：填表人写 DNS、退赛这类值不会撞 CHECK，认不出的填法在这里给出行级提示。
		status, err := normalizeImportStatus(cell("status"))
		if err != nil {
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line, "%s", err.Error()))
			continue
		}
		// heat 是可选列：留空 = 未分批；填了必须是正整数，否则整行拦截（其余行照常导入）。
		heat, ok := parseImportHeat(cell("heat"))
		if !ok {
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line,
				"heat 需要是 1-%d 的整数（留空表示未分批）", maxEntryHeat))
			continue
		}

		eventID, err := s.lookupID(ctx, `SELECT id FROM events WHERE code = ?`, eventCode)
		if err != nil {
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line, "小项 %s 不存在", eventCode))
			continue
		}
		teamID, err := s.lookupID(ctx, `SELECT id FROM teams WHERE code = ?`, teamCode)
		if err != nil {
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line, "单位 %s 不存在", teamCode))
			continue
		}
		// 编码查单位时不排除已隐藏的（编码有唯一索引，排除会撞索引或重复建档），
		// 命中就复活他：这一行马上要给他建报名，人却看不见就说不通了。
		if err := s.reviveTeam(ctx, teamID); err != nil {
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line, "%s", err.Error()))
			continue
		}
		var categoryID int64
		if categoryName != "" {
			categoryID, err = s.lookupID(ctx, `SELECT id FROM event_categories WHERE event_id = ? AND name = ?`, eventID, categoryName)
			if err != nil {
				result.Skipped++
				result.Errors = append(result.Errors, s.interceptRow(line, "组别 %s 不存在", categoryName))
				continue
			}
		} else {
			categoryID, err = s.lookupID(ctx, `SELECT id FROM event_categories WHERE event_id = ? ORDER BY sort_order, id LIMIT 1`, eventID)
			if err != nil {
				result.Skipped++
				result.Errors = append(result.Errors, s.interceptRow(line, "小项 %s 没有组别", eventCode))
				continue
			}
		}

		// 团体/对抗行（athlete_name 为空）行为不变：只建报名，不涉及人员。
		var athleteID *int64
		if athleteName != "" {
			idCard := cell("id_card")
			bib := cell("bib")
			// 证件号与号码布二选一即可，都没有就无法区分同名的两个人。
			if idCard == "" && bib == "" {
				result.Skipped++
				result.Errors = append(result.Errors, s.interceptRow(line, "填写了 athlete_name 就必须填 id_card 或 bib"))
				continue
			}
			age, ok := parseImportAge(cell("age"))
			if !ok {
				result.Skipped++
				result.Errors = append(result.Errors, s.interceptRow(line, "age 需要是 0-120 的整数"))
				continue
			}
			if idCard != "" {
				if seenIDCards[idCard] {
					result.Skipped++
					result.Errors = append(result.Errors, s.interceptRow(line, "证件号 %s 在报名表内重复出现", idCard))
					continue
				}
				seenIDCards[idCard] = true
			}
			if bib != "" {
				if seenBibs[bib] {
					result.Skipped++
					result.Errors = append(result.Errors, s.interceptRow(line, "号码布 %s 在报名表内重复出现", bib))
					continue
				}
				seenBibs[bib] = true
			}

			matched, err := s.matchImportedAthlete(ctx, athleteImportRow{
				Line:     line,
				Name:     athleteName,
				Gender:   normalizeGender(cell("gender")),
				TeamID:   teamID,
				TeamCode: teamCode,
				IDCard:   idCard,
				Bib:      bib,
				Age:      age,
			}, decisions)
			if err != nil {
				result.Skipped++
				result.Errors = append(result.Errors, s.interceptRow(line, "%s", err.Error()))
				continue
			}
			if matched.Conflict != nil {
				result.Conflicts = append(result.Conflicts, *matched.Conflict)
				continue
			}
			athleteID = &matched.AthleteID
			// keep-existing 时报名跟随库里已有的单位，避免报名与人员的单位不一致。
			teamID = matched.TeamID
		}

		created, err := s.upsertImportedEntry(ctx, entryDTO{
			EventID:     eventID,
			CategoryID:  categoryID,
			TeamID:      teamID,
			AthleteID:   athleteID,
			MemberNames: splitNames(cell("member_names")),
			Bib:         nilIfEmpty(cell("bib")),
			Seed:        nilIfEmpty(cell("seed")),
			Heat:        heat,
			Status:      status,
		})
		switch {
		case err != nil:
			result.Skipped++
			result.Errors = append(result.Errors, s.interceptRow(line, "%s", err.Error()))
		case created:
			result.Created++
		default:
			result.Updated++
		}
	}
	return result, nil
}

// parseImportAge 解析可选的 age 列：空值合法（返回 nil），非整数或超出 0-120 视为非法。
func parseImportAge(raw string) (*int, bool) {
	if raw == "" {
		return nil, true
	}
	n, err := strconv.Atoi(raw)
	if err != nil || n < 0 || n > 120 {
		return nil, false
	}
	return &n, true
}

// parseImportHeat 解析可选的 heat 列：留空表示未分批（nil），非整数或超出 1-maxEntryHeat 视为非法。
func parseImportHeat(raw string) (*int64, bool) {
	if raw == "" {
		return nil, true
	}
	n, err := strconv.ParseInt(raw, 10, 64)
	if err != nil || n < 1 || n > maxEntryHeat {
		return nil, false
	}
	return &n, true
}

// normalizeGender 只认 男/女，其它值（含空）一律忽略。
func normalizeGender(raw string) string {
	switch raw {
	case "男", "女":
		return raw
	}
	return ""
}

func splitNames(raw string) []string {
	if raw == "" {
		return nil
	}
	parts := strings.FieldsFunc(raw, func(r rune) bool { return r == ',' || r == '，' || r == '/' })
	out := make([]string, 0, len(parts))
	for _, p := range parts {
		if s := strings.TrimSpace(p); s != "" {
			out = append(out, s)
		}
	}
	return out
}

// ---------- 图片上传与静态访问 ----------

// maxUploadBytes 是单张图片的硬上限；multipart 边界与表头还占少量字节，
// 解析上限相应放宽，真实大小由 uploadHandler 里的 LimitReader 兜住。
const (
	maxUploadBytes     = 5 << 20
	maxUploadFormBytes = maxUploadBytes + 1<<20
)

// allowedUploadImageTypes 是允许上传的图片扩展名与对应 Content-Type。
// 收 SVG 会让匿名可访问的同源静态资源变成存储型 XSS 入口，故白名单里没有 .svg。
var allowedUploadImageTypes = map[string]string{
	".png":  "image/png",
	".jpg":  "image/jpeg",
	".jpeg": "image/jpeg",
	".webp": "image/webp",
	".gif":  "image/gif",
}

// uploadsCacheControl 命中随机文件名即可长缓存：同名文件内容不会变。
const uploadsCacheControl = "public, max-age=86400"

// uploadResult 是上传成功后的访问路径；path 与 url 同值，前端可直接拿去当 <img src>。
type uploadResult struct {
	Path string `json:"path"`
	URL  string `json:"url"`
}

// uploadsDir 返回当前赛事项目的上传目录（赛事包导出会带上它，跨设备转移靠的就是这里）。
// 未配置项目目录时没有落盘位置，返回 503 而不是 panic。
func (s *server) uploadsDir() (string, error) {
	dir := strings.TrimSpace(s.projectDir)
	if dir == "" {
		return "", serviceUnavailable("STATE_INVALID", "当前未配置赛事项目目录，无法上传图片")
	}
	return filepath.Join(dir, "uploads"), nil
}

// uploadHandler 保存 multipart file 字段里的图片。
// 客户端文件名只用来取扩展名，落盘名是随机十六进制，避免重名覆盖与路径注入。
func (s *server) uploadHandler(w http.ResponseWriter, r *http.Request) (any, error) {
	dir, err := s.uploadsDir()
	if err != nil {
		return nil, err
	}

	r.Body = http.MaxBytesReader(w, r.Body, maxUploadFormBytes)
	if err := r.ParseMultipartForm(maxUploadFormBytes); err != nil {
		var tooLarge *http.MaxBytesError
		if errors.As(err, &tooLarge) {
			return nil, badRequest("图片超过 5 MiB 上限", nil)
		}
		return nil, badRequest("上传内容解析失败", err.Error())
	}
	defer func() { _ = r.MultipartForm.RemoveAll() }()

	file, header, err := r.FormFile("file")
	if err != nil {
		return nil, badRequest("缺少 file 字段", nil)
	}
	defer func() { _ = file.Close() }()

	ext := strings.ToLower(filepath.Ext(header.Filename))
	if _, ok := allowedUploadImageTypes[ext]; !ok {
		return nil, badRequest("只支持 png/jpg/jpeg/webp/gif 图片", ext)
	}
	// header.Size 由客户端声明，不可信，按真实读到的字节数判限。
	body, err := io.ReadAll(io.LimitReader(file, maxUploadBytes+1))
	if err != nil {
		return nil, badRequest("读取上传内容失败", err.Error())
	}
	if len(body) > maxUploadBytes {
		return nil, badRequest("图片超过 5 MiB 上限", nil)
	}
	if len(body) == 0 {
		return nil, badRequest("上传内容为空", nil)
	}

	name, err := newUploadName(ext)
	if err != nil {
		return nil, internal(err)
	}
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return nil, internal(err)
	}
	if err := os.WriteFile(filepath.Join(dir, name), body, 0o644); err != nil {
		return nil, internal(err)
	}

	s.audit(r.Context(), "uploads.create", "upload", 0, nil,
		map[string]any{"file": name, "size": len(body)})
	path := "/uploads/" + name
	return uploadResult{Path: path, URL: path}, nil
}

// newUploadName 生成随机文件名：不用客户端文件名，既防重名覆盖也防路径注入。
func newUploadName(ext string) (string, error) {
	buf := make([]byte, 16)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf) + ext, nil
}

// serveUpload 匿名提供上传目录里的图片：大屏与 <img> 不带会话，不能要求登录。
func (s *server) serveUpload(w http.ResponseWriter, r *http.Request) {
	name := r.PathValue("name")
	ctype, ok := uploadContentType(name)
	if !ok {
		s.writeAPIError(w, r, notFound("图片不存在"))
		return
	}
	dir, err := s.uploadsDir()
	if err != nil {
		s.writeAPIError(w, r, notFound("图片不存在"))
		return
	}
	// 名字已过白名单校验，这里再用 Base 兜一层，确保只会读到 uploads 内的文件。
	file := filepath.Join(dir, filepath.Base(name))
	if info, err := os.Stat(file); err != nil || info.IsDir() {
		s.writeAPIError(w, r, notFound("图片不存在"))
		return
	}
	w.Header().Set("Content-Type", ctype)
	w.Header().Set("Cache-Control", uploadsCacheControl)
	http.ServeFile(w, r, file)
}

// uploadContentType 校验文件名并给出 Content-Type：
// 只接受「单层文件名 + 白名单扩展名」，含分隔符、.. 或只有扩展名的名字一律拒绝。
func uploadContentType(name string) (string, bool) {
	if name == "" || name != filepath.Base(name) || strings.ContainsAny(name, `/\`) {
		return "", false
	}
	ext := strings.ToLower(filepath.Ext(name))
	if name == ext {
		return "", false
	}
	ctype, ok := allowedUploadImageTypes[ext]
	return ctype, ok
}