/**
 * Reading the durable side: an accounting ledger written by the proxy.
 *
 * WHY BOTH THIS AND THE LIVE RING. The ring in `proxy/transformations.ts`
 * answers "what just happened" with no configuration at all, and loses
 * everything when the proxy stops. The ledger answers "what happened on
 * Tuesday" but only for an operator who set `TOKEN_OPTIMIZER_PROXY_ACCOUNTING`
 * before Tuesday. Neither is a substitute for the other, so `inspect` reads
 * whichever the caller asks for.
 *
 * STREAMED, NOT SLURPED, AND BOUNDED. A ledger accumulates one line per
 * request for as long as it is configured, which in a long-lived session is
 * megabytes. Reading it whole to show the last ten records would make the
 * diagnostic the most expensive thing in the session, so this streams and keeps
 * a ring of the last `last` parsed records.
 *
 * A TORN OR FOREIGN LINE IS SKIPPED, NOT FATAL. `appendRecord` writes
 * synchronously precisely so lines are whole, but a ledger can also be
 * truncated by a disk filling or concatenated by hand, and refusing to show
 * nine good records because the tenth is half-written would be the wrong
 * trade. The count of skipped lines is returned so the reader is told.
 */
import type { AccountingRecord } from '../proxy/accounting.js';
/** What a ledger read found, including what it could not parse. */
export interface LedgerRead {
    readonly records: readonly AccountingRecord[];
    readonly skipped: number;
}
/**
 * Whether a parsed line is a record rather than some other JSON.
 *
 * CHECKS THE FIELDS A RENDERER DEREFERENCES, not every field of the interface.
 * The optional ones are optional in the type too, and demanding them would
 * reject a record written by an older version of this package over a field
 * that had not been added yet -- which is exactly the ledger a reader is most
 * likely to be looking at when something went wrong.
 */
export declare function looksLikeRecord(value: unknown): value is AccountingRecord;
/** The last `last` records of a JSONL ledger, oldest first. */
export declare function readLedger(path: string, last?: number): Promise<LedgerRead>;
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