package db

import (
	"time"

	"crypto-miner-server/internal/models"
)

// ListStaleOnlineAgents returns online agents whose last_seen is older than
// the given threshold. Uses indexed status+last_seen filters instead of a full
// table scan.
func (d *Database) ListStaleOnlineAgents(olderThan time.Duration) ([]*models.Agent, error) {
	cutoff := time.Now().Add(-olderThan)
	query := `SELECT ` + agentSelectCols + ` FROM agents WHERE status = 'online' AND last_seen < ? ORDER BY last_seen ASC`
	rows, err := d.Query(query, cutoff)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var agents []*models.Agent
	for rows.Next() {
		a, err := d.scanAgent(rows)
		if err != nil {
			return nil, err
		}
		agents = append(agents, a)
	}
	return agents, rows.Err()
}