package httpapi

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"

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

// ---------- 成员姓名 JSON 数组 ----------

func parseNames(ns sql.NullString) []string {
	if !ns.Valid || ns.String == "" {
		return nil
	}
	var out []string
	if err := json.Unmarshal([]byte(ns.String), &out); err != nil {
		return nil
	}
	return out
}

func marshalNames(names []string) any {
	if len(names) == 0 {
		return nil
	}
	raw, err := json.Marshal(names)
	if err != nil {
		return nil
	}
	return string(raw)
}

// ---------- results ----------

const resultColumns = `id, event_id, entry_id, rank, result_text, result_value, unit, is_tie,
	points_override, status, state, recorded_by, recorded_at, verified_by, verified_at, note`

func scanResult(row interface{ Scan(...any) error }) (resultDTO, error) {
	var (
		r                            resultDTO
		rank                         sql.NullInt64
		text, unit                   sql.NullString
		value, override              sql.NullFloat64
		recordedBy, verifiedBy       sql.NullInt64
		recordedAt, verifiedAt, note sql.NullString
	)
	if err := row.Scan(&r.ID, &r.EventID, &r.EntryID, &rank, &text, &value, &unit, &r.IsTie,
		&override, &r.Status, &r.State, &recordedBy, &recordedAt, &verifiedBy, &verifiedAt, &note); err != nil {
		return r, err
	}
	r.Rank = intPtr(rank)
	r.ResultText = text.String
	r.ResultValue = f64Ptr(value)
	r.Unit = unit.String
	r.PointsOverride = f64Ptr(override)
	r.RecordedBy = i64Ptr(recordedBy)
	r.RecordedAt = strPtr(recordedAt)
	r.VerifiedBy = i64Ptr(verifiedBy)
	r.VerifiedAt = strPtr(verifiedAt)
	r.Note = strPtr(note)
	return r, nil
}

func (s *server) resultsByEvent(ctx context.Context, eventID int64) ([]resultDTO, error) {
	return queryResults(ctx, s.ev, `SELECT `+resultColumns+` FROM results WHERE event_id = ? ORDER BY id`, eventID)
}

func queryResults(ctx context.Context, q queryer, query string, args ...any) ([]resultDTO, error) {
	rows, err := q.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]resultDTO, 0)
	for rows.Next() {
		r, err := scanResult(rows)
		if err != nil {
			return nil, internal(err)
		}
		out = append(out, r)
	}
	if err := rows.Err(); err != nil {
		return nil, internal(err)
	}
	if err := attachResultPoints(ctx, q, out); err != nil {
		return nil, err
	}
	return out, nil
}

// attachResultPoints 给已发布成绩补上得分（该成绩产生的 result 流水合计）。
// 草稿没有流水，保持 nil；录入页据此预览发布后的分值变化。
func attachResultPoints(ctx context.Context, q queryer, items []resultDTO) error {
	ids := make([]any, 0, len(items))
	index := make(map[int64]int, len(items))
	for i := range items {
		if items[i].State != "published" {
			continue
		}
		ids = append(ids, items[i].ID)
		index[items[i].ID] = i
	}
	if len(ids) == 0 {
		return nil
	}

	rows, err := q.QueryContext(ctx,
		`SELECT result_id, SUM(points) FROM score_ledger
		  WHERE voided = 0 AND source_type = 'result' AND result_id IN (`+placeholders(len(ids))+`)
		  GROUP BY result_id`, ids...)
	if err != nil {
		return internal(err)
	}
	defer func() { _ = rows.Close() }()

	for rows.Next() {
		var (
			resultID int64
			points   float64
		)
		if err := rows.Scan(&resultID, &points); err != nil {
			return internal(err)
		}
		if i, ok := index[resultID]; ok {
			v := points
			items[i].Points = &v
		}
	}
	if err := rows.Err(); err != nil {
		return internal(err)
	}
	return nil
}

func (s *server) getResult(ctx context.Context, id int64) (resultDTO, error) {
	r, err := scanResult(s.ev.QueryRowContext(ctx, `SELECT `+resultColumns+` FROM results WHERE id = ?`, id))
	if errors.Is(err, sql.ErrNoRows) {
		return resultDTO{}, notFound("成绩不存在")
	}
	if err != nil {
		return resultDTO{}, internal(err)
	}
	items := []resultDTO{r}
	if err := attachResultPoints(ctx, s.ev, items); err != nil {
		return resultDTO{}, err
	}
	return items[0], nil
}

func (s *server) listResultsPage(ctx context.Context, eventID int64, state string, page, size int) (pageResult[resultDTO], error) {
	where := []string{"1 = 1"}
	args := []any{}
	if eventID > 0 {
		where = append(where, "event_id = ?")
		args = append(args, eventID)
	}
	if state != "" {
		where = append(where, "state = ?")
		args = append(args, state)
	}
	clause := " WHERE " + joinAnd(where)

	var total int
	if err := s.ev.QueryRowContext(ctx, `SELECT COUNT(*) FROM results`+clause, args...).Scan(&total); err != nil {
		return pageResult[resultDTO]{}, internal(err)
	}

	query := `SELECT ` + resultColumns + ` FROM results` + clause + ` ORDER BY id LIMIT ? OFFSET ?`
	args = append(args, size, (page-1)*size)
	items, err := queryResults(ctx, s.ev, query, args...)
	if err != nil {
		return pageResult[resultDTO]{}, err
	}
	return pageResult[resultDTO]{Items: items, Total: total, Page: page, Size: size}, nil
}

// upsertDraft 批量保存草稿；已发布的成绩直接拒绝（STATE_INVALID），
// 必须先撤销发布再改，避免 rank 被就地清空而流水不动。
func (s *server) upsertDraft(ctx context.Context, eventID int64, userID int64, items []draftResultInput) ([]resultDTO, error) {
	tx, err := s.ev.BeginTx(ctx, nil)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = tx.Rollback() }()

	for i, it := range items {
		if it.EntryID == 0 {
			return nil, badRequest("results[].entryId 必填", i)
		}
		var entryEvent int64
		if err := tx.QueryRowContext(ctx, `SELECT event_id FROM entries WHERE id = ?`, it.EntryID).Scan(&entryEvent); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return nil, badRequest("entryId 不存在", it.EntryID)
			}
			return nil, internal(err)
		}
		if entryEvent != eventID {
			return nil, badRequest("entryId 不属于该小项", it.EntryID)
		}
		// 已发布成绩不能被「存草稿」就地改写：ON CONFLICT 不改 state，
		// 若放行会把 rank 清空但流水不动，大屏奖牌与积分立刻对不上。
		var state string
		err := tx.QueryRowContext(ctx, `SELECT state FROM results WHERE entry_id = ?`, it.EntryID).Scan(&state)
		switch {
		case errors.Is(err, sql.ErrNoRows):
			// 尚无成绩，正常新建草稿。
		case err != nil:
			return nil, internal(err)
		case state == string(domain.ResultStatePublished):
			return nil, stateInvalid("该成绩已发布，请先撤销发布再修改")
		}
		if _, err := tx.ExecContext(ctx,
			`INSERT INTO results (event_id, entry_id, rank, result_text, result_value, unit, is_tie,
			        points_override, status, state, recorded_by, recorded_at, note, updated_at)
			 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 'draft', ?, datetime('now'), ?, datetime('now'))
			 ON CONFLICT(entry_id) DO UPDATE SET
			        rank = excluded.rank,
			        result_text = excluded.result_text,
			        result_value = excluded.result_value,
			        unit = COALESCE(excluded.unit, results.unit),
			        is_tie = excluded.is_tie,
			        points_override = excluded.points_override,
			        status = excluded.status,
			        note = excluded.note,
			        recorded_by = excluded.recorded_by,
			        recorded_at = excluded.recorded_at,
			        updated_at = datetime('now')`,
			eventID, it.EntryID, nullInt(it.Rank), nullStr(it.ResultText), nullF64(it.ResultValue),
			nullStr(it.Unit), it.IsTie, nullF64(it.PointsOverride), orDefault(it.Status, "ok"),
			nullID(userID), nullStr(it.Note)); err != nil {
			return nil, internal(err)
		}
	}
	if err := tx.Commit(); err != nil {
		return nil, internal(err)
	}
	return s.resultsByEvent(ctx, eventID)
}

func nullID(id int64) any {
	if id == 0 {
		return nil
	}
	return id
}

func joinAnd(parts []string) string {
	out := ""
	for i, p := range parts {
		if i > 0 {
			out += " AND "
		}
		out += p
	}
	return out
}

// ---------- ledger ----------

func (s *server) activeLedger(ctx context.Context, q queryer) ([]domain.LedgerEntry, error) {
	return queryLedger(ctx, q, `SELECT id, team_id, athlete_id, event_id, entry_id, result_id,
		source_type, source_id, points, voided, created_at FROM score_ledger WHERE voided = 0`)
}

func queryLedger(ctx context.Context, q queryer, query string, args ...any) ([]domain.LedgerEntry, error) {
	rows, err := q.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, internal(err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]domain.LedgerEntry, 0)
	for rows.Next() {
		var (
			l       domain.LedgerEntry
			athlete sql.NullInt64
			event   sql.NullInt64
			entry   sql.NullInt64
			result  sql.NullInt64
			created sql.NullString
		)
		if err := rows.Scan(&l.ID, &l.TeamID, &athlete, &event, &entry, &result,
			&l.SourceType, &l.SourceID, &l.Points, &l.Voided, &created); err != nil {
			return nil, internal(err)
		}
		l.AthleteID = athlete.Int64
		l.EventID = event.Int64
		l.EntryID = entry.Int64
		l.ResultID = result.Int64
		l.CreatedAt = created.String
		out = append(out, l)
	}
	return out, rows.Err()
}