import type { DeviceChannel } from "./types.js";
/** Options for configuring polling-based subscriptions. */
export interface SubscriptionOptions {
    /** Polling interval in milliseconds (default 10000 = 10 seconds). */
    intervalMs?: number;
}
/** A snapshot of a single channel's current state, emitted on change. */
export interface ChannelUpdate {
    serial: string;
    channel: number;
    value: number | null;
    units: string | null;
    status: string | null;
    timestamp: string | null;
}
/** Handle returned by subscribe() to stop receiving updates. */
export interface Subscription {
    /** Stop polling and release resources. */
    unsubscribe(): void;
}
/** Callback invoked with each channel update. */
export type ChannelUpdateCallback = (update: ChannelUpdate) => void;
/** Callback invoked when a polling cycle encounters an error. */
export type ErrorCallback = (error: Error) => void;
/** Dependency: a function that fetches all channels for a device serial. */
export type ChannelFetcher = (serial: string, signal?: AbortSignal) => Promise<DeviceChannel[]>;
/**
 * Create a polling subscription that monitors a device's channels for changes.
 *
 * @param serial - Device serial to monitor
 * @param fetchChannels - Function to retrieve current channel state (injected for testability)
 * @param callback - Called with each channel update when state changes
 * @param options - Polling configuration and error handler
 * @returns Subscription handle with unsubscribe()
 */
export declare function createSubscription(serial: string, fetchChannels: ChannelFetcher, callback: ChannelUpdateCallback, options?: SubscriptionOptions & {
    onError?: ErrorCallback;
}): Subscription;
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