package store

import (
	"context"
	"database/sql"
	"errors"
	"time"
)

// PutClusterState keeps a value under a key, for machines that read the
// store rather than a control plane; it reports whether it changed.
func (s *DB) PutClusterState(ctx context.Context, key, value string) (bool, error) {
	if old, err := s.ClusterState(ctx, key); err == nil && old == value {
		return false, nil
	}
	_, err := s.db.ExecContext(ctx, `INSERT INTO cluster_state (key, value, updated_at) VALUES (?, ?, ?)
		ON CONFLICT (key) DO UPDATE SET value = excluded.value, updated_at = excluded.updated_at`,
		key, value, millis(time.Now()))
	return err == nil, err
}

// ClusterState reads a value; ErrNotFound when there is none.
func (s *DB) ClusterState(ctx context.Context, key string) (string, error) {
	var v string
	err := s.db.QueryRowContext(ctx, `SELECT value FROM cluster_state WHERE key = ?`, key).Scan(&v)
	if errors.Is(err, sql.ErrNoRows) {
		return "", ErrNotFound
	}
	return v, err
}