/**
 * Shared primitives for the hash-chained event log: record shapes, the genesis
 * hash, type guards, the byte hasher, and the head reader. Split out so both
 * {@link EventLog} (`event-log.ts`) and the watermark-aware verifier
 * (`event-log-verify.ts`) can depend on them without an import cycle.
 *
 * @module core/event-log-shared
 */
import type { Storage } from '../storage/interface.ts';
import type { WorkflowVersionTuple } from './workflow-version-tuple.ts';
/** Hash value used as `prevHash` for the very first entry in a log. */
export declare const GENESIS_HASH = "0000000000000000";
/** A single entry in the event log, as stored in the KV backend. */
export interface WorkflowLogEntry {
    /** Discriminates the entry type, e.g. `'workflow:checkpoint'`. */
    type: string;
    /** Workflow this entry belongs to. */
    workflowId: string;
    /** Zero-based monotonic sequence number. */
    sequence: number;
    /**
     * wyhash (16 hex chars) of the *encoded bytes* of the previous entry.
     * The first entry carries {@link GENESIS_HASH}.
     */
    prevHash: string;
    /** Arbitrary event payload. */
    payload: unknown;
    /** Unix timestamp (ms) at the time of the append. */
    timestamp: number;
    /**
     * Workflow, agent, and tool version tuple captured at the time of this
     * entry. Only present when the caller passes a `versionTuple` argument.
     * Absent for entries written by non-agent workflows or callers that opt out.
     */
    versionTuple?: WorkflowVersionTuple;
}
/**
 * The head record stored at `ev:{workflowId}:head`.
 * Tracks both the latest sequence number and the hash of the last committed
 * entry so that subsequent appends can chain without a second storage read.
 */
export interface EventHeadRecord {
    sequence: number;
    lastHash: string;
}
/**
 * The head state for a workflow with no committed entries.
 * Used as the starting point when appending the first event.
 * Frozen to prevent accidental mutation of the shared genesis sentinel.
 */
export declare const EMPTY_EVENT_HEAD: Readonly<EventHeadRecord>;
/** Compute a 16-character hex hash of an arbitrary byte buffer. */
export declare function hashBytes(bytes: Uint8Array): string;
/** Narrow an unknown decoded value to {@link WorkflowLogEntry}. */
export declare function isWorkflowLogEntry(value: unknown): value is WorkflowLogEntry;
/** Narrow an unknown decoded value to {@link EventHeadRecord}. */
export declare function isEventHeadRecord(value: unknown): value is EventHeadRecord;
/**
 * Read the current head record for a workflow from storage.
 *
 * Returns {@link EMPTY_EVENT_HEAD} (`sequence: -1`) when no head record exists
 * (i.e., the log is empty). This lets the first append compute `sequence = 0`
 * and `prevHash = GENESIS_HASH`.
 */
export declare function readEventHead(storage: Storage, workflowId: string): Promise<EventHeadRecord>;