using Microsoft.Data.Sqlite;
public sealed record LedgerDecision(bool Replay, bool Conflict, int Amount);
public sealed class LocalLedger {
    private readonly string connectionString;
    public LocalLedger(LabSettings settings) { connectionString = new SqliteConnectionStringBuilder { DataSource = settings.LedgerPath, DefaultTimeout = 2 }.ToString(); }
    private SqliteConnection Open() { var connection = new SqliteConnection(connectionString); connection.Open(); return connection; }
    public void Initialize() { using var connection = Open(); using var command = connection.CreateCommand(); command.CommandText = "CREATE TABLE IF NOT EXISTS receipts (request_key TEXT PRIMARY KEY, amount INTEGER NOT NULL)"; command.ExecuteNonQuery(); }
    public LedgerDecision Record(string key, int amount) {
        using var connection = Open(); using var transaction = connection.BeginTransaction();
        using var insert = connection.CreateCommand(); insert.Transaction = transaction;
        insert.CommandText = "INSERT INTO receipts(request_key, amount) VALUES ($key, $amount) ON CONFLICT(request_key) DO NOTHING";
        insert.Parameters.AddWithValue("$key", key); insert.Parameters.AddWithValue("$amount", amount); int changed = insert.ExecuteNonQuery();
        using var read = connection.CreateCommand(); read.Transaction = transaction; read.CommandText = "SELECT amount FROM receipts WHERE request_key = $key"; read.Parameters.AddWithValue("$key", key);
        int stored = Convert.ToInt32(read.ExecuteScalar(), System.Globalization.CultureInfo.InvariantCulture); transaction.Commit();
        return new LedgerDecision(changed == 0, stored != amount, stored);
    }
    public int Count() { using var connection = Open(); using var read = connection.CreateCommand(); read.CommandText = "SELECT COUNT(*) FROM receipts"; return Convert.ToInt32(read.ExecuteScalar(), System.Globalization.CultureInfo.InvariantCulture); }
}