package httpapi

import (
	"context"
	"database/sql"
	"errors"
	"strings"

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

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

const eventColumns = `id, sport_id, code, name, event_type, result_mode, result_type, compare,
	record_eligible, scored, multiplier, status, scheduled_at, venue, sort_order, remark`

func scanEvent(row interface{ Scan(...any) error }) (eventDTO, error) {
	var (
		e                        eventDTO
		scheduledAt, venue, note sql.NullString
	)
	err := row.Scan(&e.ID, &e.SportID, &e.Code, &e.Name, &e.EventType, &e.ResultMode, &e.ResultType,
		&e.Compare, &e.RecordEligible, &e.Scored, &e.Multiplier, &e.Status,
		&scheduledAt, &venue, &e.SortOrder, &note)
	e.ScheduledAt = strPtr(scheduledAt)
	e.Venue = strPtr(venue)
	e.Remark = strPtr(note)
	return e, err
}

func (s *server) listEvents(ctx context.Context, sportID int64) ([]eventDTO, error) {
	query := `SELECT ` + eventColumns + ` FROM events`
	args := []any{}
	if sportID > 0 {
		query += ` WHERE sport_id = ?`
		args = append(args, sportID)
	}
	query += ` ORDER BY sort_order, code`

	rows, err := s.ev.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]eventDTO, 0)
	for rows.Next() {
		e, err := scanEvent(rows)
		if err != nil {
			return nil, internal(err)
		}
		out = append(out, e)
	}
	return out, rows.Err()
}

func (s *server) getEvent(ctx context.Context, id int64) (eventDTO, error) {
	e, err := eventByIDQ(ctx, s.ev, id)
	if err != nil {
		return eventDTO{}, err
	}
	cats, err := s.listCategories(ctx, id)
	if err != nil {
		return eventDTO{}, err
	}
	chs, err := s.listChannels(ctx, id)
	if err != nil {
		return eventDTO{}, err
	}
	e.Categories = cats
	e.Channels = chs
	return e, nil
}

// eventByIDQ 在给定连接/事务内读取小项（不含组别/通道），供写事务内构造 change_log 载荷复用。
func eventByIDQ(ctx context.Context, q queryer, id int64) (eventDTO, error) {
	e, err := scanEvent(q.QueryRowContext(ctx, `SELECT `+eventColumns+` FROM events WHERE id = ?`, id))
	if errors.Is(err, sql.ErrNoRows) {
		return eventDTO{}, notFound("小项不存在")
	}
	if err != nil {
		return eventDTO{}, internal(err)
	}
	return e, nil
}

func (s *server) createEvent(ctx context.Context, in eventDTO) (eventDTO, error) {
	if in.SportID == 0 || strings.TrimSpace(in.Code) == "" || strings.TrimSpace(in.Name) == "" {
		return eventDTO{}, badRequest("sportId、code、name 必填", nil)
	}
	tx, err := s.ev.BeginTx(ctx, nil)
	if err != nil {
		return eventDTO{}, internal(err)
	}
	defer func() { _ = tx.Rollback() }()

	res, err := tx.ExecContext(ctx,
		`INSERT INTO events (sport_id, code, name, event_type, result_mode, result_type, compare,
		        record_eligible, scored, multiplier, status, scheduled_at, venue, sort_order, remark)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		in.SportID, in.Code, in.Name,
		orDefault(in.EventType, "individual"), orDefault(in.ResultMode, "auto"),
		orDefault(in.ResultType, "none"), orDefault(in.Compare, "none"),
		in.RecordEligible, in.Scored, multiplierOrOne(in.Multiplier), orDefault(in.Status, "pending"),
		nullStr(in.ScheduledAt), nullStr(in.Venue), in.SortOrder, nullStr(in.Remark))
	if isUniqueViolation(err) {
		return eventDTO{}, conflict("小项编码已存在")
	}
	if isForeignKeyViolation(err) {
		return eventDTO{}, badRequest("sportId 不存在", nil)
	}
	if err != nil {
		return eventDTO{}, internal(err)
	}
	id, err := lastInsertID(res)
	if err != nil {
		return eventDTO{}, internal(err)
	}
	// 项目增删改要推给大屏，否则底栏/分项页拿不到新项目。
	if err := s.bumpEvent(ctx, tx, id); err != nil {
		return eventDTO{}, err
	}
	if err := tx.Commit(); err != nil {
		return eventDTO{}, internal(err)
	}
	return s.getEvent(ctx, id)
}

func (s *server) updateEvent(ctx context.Context, id int64, in eventDTO) (eventDTO, error) {
	tx, err := s.ev.BeginTx(ctx, nil)
	if err != nil {
		return eventDTO{}, internal(err)
	}
	defer func() { _ = tx.Rollback() }()

	res, err := tx.ExecContext(ctx,
		`UPDATE events SET sport_id = ?, code = ?, name = ?, event_type = ?, result_mode = ?,
		        result_type = ?, compare = ?, record_eligible = ?, scored = ?, multiplier = ?,
		        status = ?, scheduled_at = ?, venue = ?, sort_order = ?, remark = ?
		  WHERE id = ?`,
		in.SportID, in.Code, in.Name,
		orDefault(in.EventType, "individual"), orDefault(in.ResultMode, "auto"),
		orDefault(in.ResultType, "none"), orDefault(in.Compare, "none"),
		in.RecordEligible, in.Scored, multiplierOrOne(in.Multiplier), orDefault(in.Status, "pending"),
		nullStr(in.ScheduledAt), nullStr(in.Venue), in.SortOrder, nullStr(in.Remark), id)
	if isUniqueViolation(err) {
		return eventDTO{}, conflict("小项编码已存在")
	}
	if isForeignKeyViolation(err) {
		return eventDTO{}, badRequest("sportId 不存在", nil)
	}
	if err != nil {
		return eventDTO{}, internal(err)
	}
	if err := requireChanges(res, "小项不存在"); err != nil {
		return eventDTO{}, err
	}
	if err := s.bumpEvent(ctx, tx, id); err != nil {
		return eventDTO{}, err
	}
	if err := tx.Commit(); err != nil {
		return eventDTO{}, internal(err)
	}
	return s.getEvent(ctx, id)
}

// bumpEvent 在写事务内推送小项变更；组别/通道的改动同样以本小项为载体。
func (s *server) bumpEvent(ctx context.Context, tx *sql.Tx, eventID int64) error {
	ev, err := eventByIDQ(ctx, tx, eventID)
	if err != nil {
		return err
	}
	return bumpVersion(ctx, tx, "events", eventID, "upsert", ev, middleware.User(ctx).ID)
}

func (s *server) deleteEvent(ctx context.Context, id int64) error {
	has, err := exists(ctx, s.ev, `SELECT 1 FROM entries WHERE event_id = ? LIMIT 1`, id)
	if err != nil {
		return internal(err)
	}
	if has {
		return conflict("小项已有报名数据，不能删除")
	}
	tx, err := s.ev.BeginTx(ctx, nil)
	if err != nil {
		return internal(err)
	}
	defer func() { _ = tx.Rollback() }()
	for _, stmt := range []string{
		`DELETE FROM event_score_channels WHERE event_id = ?`,
		`DELETE FROM event_categories WHERE event_id = ?`,
		`DELETE FROM events WHERE id = ?`,
	} {
		if _, err := tx.ExecContext(ctx, stmt, id); err != nil {
			return internal(err)
		}
	}
	if err := bumpVersion(ctx, tx, "events", id, "void", map[string]any{"id": id}, middleware.User(ctx).ID); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return internal(err)
	}
	return nil
}

func multiplierOrOne(v float64) float64 {
	if v <= 0 {
		return 1
	}
	return v
}

// ---------- categories ----------

func (s *server) listCategories(ctx context.Context, eventID int64) ([]categoryDTO, error) {
	rows, err := s.ev.QueryContext(ctx,
		`SELECT id, event_id, name, multiplier, gender, age_min, age_max, sort_order
		   FROM event_categories WHERE event_id = ? ORDER BY sort_order, id`, eventID)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]categoryDTO, 0)
	for rows.Next() {
		var (
			c              categoryDTO
			gender         sql.NullString
			ageMin, ageMax sql.NullInt64
		)
		if err := rows.Scan(&c.ID, &c.EventID, &c.Name, &c.Multiplier, &gender, &ageMin, &ageMax, &c.SortOrder); err != nil {
			return nil, internal(err)
		}
		c.Gender = strPtr(gender)
		c.AgeMin = intPtr(ageMin)
		c.AgeMax = intPtr(ageMax)
		out = append(out, c)
	}
	return out, rows.Err()
}

// replaceCategories 整体替换某小项的组别（devdocs/05 约定）。已有报名数据时拒绝替换，
// 否则外键会把历史报名项一并带走。
func (s *server) replaceCategories(ctx context.Context, eventID int64, in []categoryDTO) ([]categoryDTO, error) {
	has, err := exists(ctx, s.ev,
		`SELECT 1 FROM entries e JOIN event_categories c ON c.id = e.category_id
		  WHERE c.event_id = ? LIMIT 1`, eventID)
	if err != nil {
		return nil, internal(err)
	}
	if has {
		return nil, conflict("该项目已有报名数据，不能整体替换组别")
	}

	tx, err := s.ev.BeginTx(ctx, nil)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = tx.Rollback() }()

	if _, err := tx.ExecContext(ctx, `DELETE FROM event_categories WHERE event_id = ?`, eventID); err != nil {
		return nil, internal(err)
	}
	for i, c := range in {
		if strings.TrimSpace(c.Name) == "" {
			return nil, badRequest("组别 name 必填", i)
		}
		if _, err := tx.ExecContext(ctx,
			`INSERT INTO event_categories (event_id, name, multiplier, gender, age_min, age_max, sort_order)
			 VALUES (?, ?, ?, ?, ?, ?, ?)`,
			eventID, c.Name, multiplierOrOne(c.Multiplier), nullStr(c.Gender), nullInt(c.AgeMin), nullInt(c.AgeMax), c.SortOrder); err != nil {
			if isUniqueViolation(err) {
				return nil, conflict("组别名称重复：" + c.Name)
			}
			return nil, internal(err)
		}
	}
	if err := s.bumpEvent(ctx, tx, eventID); err != nil {
		return nil, err
	}
	if err := tx.Commit(); err != nil {
		return nil, internal(err)
	}
	return s.listCategories(ctx, eventID)
}

// ---------- score channels ----------

func (s *server) listChannels(ctx context.Context, eventID int64) ([]channelDTO, error) {
	rows, err := s.ev.QueryContext(ctx,
		`SELECT id, event_id, scope, basis, profile_id, sort_order
		   FROM event_score_channels WHERE event_id = ? ORDER BY sort_order, id`, eventID)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]channelDTO, 0)
	for rows.Next() {
		var c channelDTO
		if err := rows.Scan(&c.ID, &c.EventID, &c.Scope, &c.Basis, &c.ProfileID, &c.SortOrder); err != nil {
			return nil, internal(err)
		}
		out = append(out, c)
	}
	return out, rows.Err()
}

func (s *server) replaceChannels(ctx context.Context, eventID int64, in []channelDTO) ([]channelDTO, error) {
	tx, err := s.ev.BeginTx(ctx, nil)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = tx.Rollback() }()

	if _, err := tx.ExecContext(ctx, `DELETE FROM event_score_channels WHERE event_id = ?`, eventID); err != nil {
		return nil, internal(err)
	}
	for i, c := range in {
		if c.Scope != "athlete" && c.Scope != "team" {
			return nil, badRequest("通道 scope 只能是 athlete/team", i)
		}
		switch c.Basis {
		case "result", "manual", "aggregate":
		default:
			return nil, badRequest("通道 basis 非法", i)
		}
		if c.ProfileID == 0 {
			return nil, badRequest("通道 profileId 必填", i)
		}
		if _, err := tx.ExecContext(ctx,
			`INSERT INTO event_score_channels (event_id, scope, basis, profile_id, sort_order)
			 VALUES (?, ?, ?, ?, ?)`,
			eventID, c.Scope, c.Basis, c.ProfileID, c.SortOrder); err != nil {
			if isUniqueViolation(err) {
				return nil, conflict("同一 scope+basis 只能配置一个通道")
			}
			if isForeignKeyViolation(err) {
				return nil, badRequest("profileId 不存在", i)
			}
			return nil, internal(err)
		}
	}
	if err := s.bumpEvent(ctx, tx, eventID); err != nil {
		return nil, err
	}
	if err := tx.Commit(); err != nil {
		return nil, internal(err)
	}
	return s.listChannels(ctx, eventID)
}

// ---------- entries ----------

const entryColumns = `e.id, e.event_id, e.category_id, e.team_id, e.athlete_id, e.member_names,
	e.bib, e.seed, e.status, e.remark, a.name, t.code, t.name, t.short_name, c.name`

func scanEntry(row interface{ Scan(...any) error }) (entryDTO, error) {
	var (
		e              entryDTO
		athleteID      sql.NullInt64
		memberNames    sql.NullString
		bib, seed, rem sql.NullString
		athleteName    sql.NullString
		teamCode       sql.NullString
		teamName       sql.NullString
		shortName      sql.NullString
		categoryName   sql.NullString
	)
	if err := row.Scan(&e.ID, &e.EventID, &e.CategoryID, &e.TeamID, &athleteID, &memberNames,
		&bib, &seed, &e.Status, &rem, &athleteName, &teamCode, &teamName, &shortName, &categoryName); err != nil {
		return e, err
	}
	e.AthleteID = i64Ptr(athleteID)
	e.MemberNames = parseNames(memberNames)
	e.Bib = strPtr(bib)
	e.Seed = strPtr(seed)
	e.Remark = strPtr(rem)
	e.AthleteName = strPtr(athleteName)
	e.TeamCode = teamCode.String
	e.TeamName = teamName.String
	e.ShortName = strPtr(shortName)
	e.CategoryName = categoryName.String
	return e, nil
}

const entrySelect = `SELECT ` + entryColumns + `
	FROM entries e
	LEFT JOIN athletes a ON a.id = e.athlete_id
	JOIN teams t ON t.id = e.team_id
	JOIN event_categories c ON c.id = e.category_id`

func (s *server) listEntries(ctx context.Context, eventID int64) ([]entryDTO, error) {
	rows, err := s.ev.QueryContext(ctx, entrySelect+` WHERE e.event_id = ? ORDER BY c.sort_order, e.id`, eventID)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]entryDTO, 0)
	for rows.Next() {
		e, err := scanEntry(rows)
		if err != nil {
			return nil, internal(err)
		}
		out = append(out, e)
	}
	return out, rows.Err()
}

// listEntriesWithResults 返回报名项及其成绩（无成绩时 result=null）。
func (s *server) listEntriesWithResults(ctx context.Context, eventID int64) ([]entryWithResultDTO, error) {
	entries, err := s.listEntries(ctx, eventID)
	if err != nil {
		return nil, err
	}
	results, err := s.resultsByEvent(ctx, eventID)
	if err != nil {
		return nil, err
	}
	byEntry := make(map[int64]resultDTO, len(results))
	for _, r := range results {
		byEntry[r.EntryID] = r
	}

	out := make([]entryWithResultDTO, 0, len(entries))
	for _, e := range entries {
		item := entryWithResultDTO{entryDTO: e}
		if r, ok := byEntry[e.ID]; ok {
			cp := r
			item.Result = &cp
		}
		out = append(out, item)
	}
	return out, nil
}

func (s *server) getEntry(ctx context.Context, id int64) (entryDTO, error) {
	e, err := scanEntry(s.ev.QueryRowContext(ctx, entrySelect+` WHERE e.id = ?`, id))
	if errors.Is(err, sql.ErrNoRows) {
		return entryDTO{}, notFound("报名项不存在")
	}
	if err != nil {
		return entryDTO{}, internal(err)
	}
	return e, nil
}

func (s *server) createEntry(ctx context.Context, in entryDTO) (entryDTO, error) {
	if in.EventID == 0 || in.CategoryID == 0 || in.TeamID == 0 {
		return entryDTO{}, badRequest("eventId、categoryId、teamId 必填", nil)
	}
	res, err := s.ev.ExecContext(ctx,
		`INSERT INTO entries (event_id, category_id, team_id, athlete_id, member_names, bib, seed, status, remark)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		in.EventID, in.CategoryID, in.TeamID, nullI64(in.AthleteID), marshalNames(in.MemberNames),
		nullStr(in.Bib), nullStr(in.Seed), orDefault(in.Status, "registered"), nullStr(in.Remark))
	if isUniqueViolation(err) {
		return entryDTO{}, conflict("该报名项已存在")
	}
	if isForeignKeyViolation(err) {
		return entryDTO{}, badRequest("eventId/categoryId/teamId/athleteId 不存在", nil)
	}
	if err != nil {
		return entryDTO{}, internal(err)
	}
	id, err := lastInsertID(res)
	if err != nil {
		return entryDTO{}, internal(err)
	}
	return s.getEntry(ctx, id)
}

func (s *server) updateEntry(ctx context.Context, id int64, in entryDTO) (entryDTO, error) {
	res, err := s.ev.ExecContext(ctx,
		`UPDATE entries SET category_id = ?, team_id = ?, athlete_id = ?, member_names = ?,
		        bib = ?, seed = ?, status = ?, remark = ? WHERE id = ?`,
		in.CategoryID, in.TeamID, nullI64(in.AthleteID), marshalNames(in.MemberNames),
		nullStr(in.Bib), nullStr(in.Seed), orDefault(in.Status, "registered"), nullStr(in.Remark), id)
	if isUniqueViolation(err) {
		return entryDTO{}, conflict("该报名项已存在")
	}
	if isForeignKeyViolation(err) {
		return entryDTO{}, badRequest("categoryId/teamId/athleteId 不存在", nil)
	}
	if err != nil {
		return entryDTO{}, internal(err)
	}
	if err := requireChanges(res, "报名项不存在"); err != nil {
		return entryDTO{}, err
	}
	return s.getEntry(ctx, id)
}

func (s *server) deleteEntry(ctx context.Context, id int64) error {
	// 报名项被成绩引用时不允许删除；业务数据一律软删（status=scratched）。
	res, err := s.ev.ExecContext(ctx, `UPDATE entries SET status = 'scratched' WHERE id = ?`, id)
	if err != nil {
		return internal(err)
	}
	return requireChanges(res, "报名项不存在")
}