package db

import (
	"database/sql"
	"errors"
)

// GetJetstreamCursor returns the last persisted Jetstream cursor (time_us).
// Returns 0 when no cursor has been saved yet (e.g. fresh database).
func GetJetstreamCursor(db DBTX) (int64, error) {
	var cursor int64
	err := db.QueryRow(`SELECT cursor FROM jetstream_cursor WHERE id = 1`).Scan(&cursor)
	if errors.Is(err, sql.ErrNoRows) {
		return 0, nil
	}
	if err != nil {
		return 0, err
	}
	return cursor, nil
}

// SaveJetstreamCursor writes the given cursor to the singleton jetstream_cursor row.
// Idempotent — safe to call on every tick.
func SaveJetstreamCursor(db DBTX, cursor int64) error {
	_, err := db.Exec(`
		INSERT INTO jetstream_cursor (id, cursor, updated_at)
		VALUES (1, ?, CURRENT_TIMESTAMP)
		ON CONFLICT(id) DO UPDATE SET
			cursor = excluded.cursor,
			updated_at = excluded.updated_at
	`, cursor)
	return err
}