import { NgZone } from '@angular/core';
import { ConfigService } from 'tabby-core';
import { SSHTabComponent } from 'tabby-ssh';
/** What the dot next to a session shows. */
export type PingState = 'good' | 'fair' | 'poor' | 'unknown' | 'unavailable';
/**
 * Round-trip latency of the live SSH sessions, measured on the sessions
 * themselves.
 *
 * There is nothing to read: neither Tabby nor russh keeps a round-trip time
 * anywhere (checked on the installed bundle — russh's only mention of
 * keepalives is the interval handed to `connect()`, which reports nothing
 * back). So the number has to be produced, and the choice of how says what the
 * dot actually means.
 *
 * A timed SFTP request on the session's own channel, rather than an ICMP ping
 * or a TCP connect to port 22:
 *
 *   - it measures the *encrypted round trip of this session* — the delay that
 *     is felt when typing — where ICMP measures the host and is commonly
 *     filtered outright, which would show red on a perfectly good link;
 *   - it opens nothing. A TCP probe would start, then abandon, a connection
 *     before authentication on every tick: a trail in the server's auth log,
 *     and a plausible way to get banned by one's own fail2ban;
 *   - no external process, unlike `ping.exe`, once per session per tick.
 *
 * Two consequences to know about. The channel is shared with real SFTP work
 * (`SSHSession.openSFTP()` caches one channel per session), so a probe sent
 * during a large transfer queues behind its data and reads high — that is the
 * session genuinely being slow to answer, not a wrong measurement. And a
 * server with no SFTP subsystem cannot be measured at all: that session is
 * marked unavailable once and never probed again.
 */
export declare class SidebarPlusPingService {
    private config;
    private zone;
    private samples;
    /** Probes in flight, so a slow answer cannot pile up behind itself. */
    private inFlight;
    /** Sessions whose server has no SFTP subsystem — asked once, never again. */
    private unavailable;
    constructor(config: ConfigService, zone: NgZone);
    /** 0 disables the whole thing, which is the default — see the settings tab. */
    get intervalMs(): number;
    /**
     * Called on the tree's existing 2s poll, once per live session: no timer of
     * its own, on purpose. The tunnels list is refreshed the same way, and a
     * second interval in the sidebar is a second thing to remember to stop.
     */
    poll(tabs: SSHTabComponent[]): void;
    state(tab: SSHTabComponent): PingState;
    /**
     * The last measured round trip, or null when there is none — probing off,
     * first probe not back yet, or a server that opens no SFTP channel.
     *
     * The raw number rather than a sentence: the tooltip that shows it is a
     * compact `profil | 13 ms | 1m 47s`, so the wording belongs to the caller
     * and a placeholder here would have to be dropped by it anyway.
     */
    latencyMs(tab: SSHTabComponent): number | null;
    /**
     * One round trip on the session's SFTP channel.
     *
     * `stat('.')` is used as a *ping*, not as an observation: nothing in the
     * answer is read, only the time it took to come back. That distinction
     * matters here, because `stat()` is banned everywhere else in this codebase
     * for observing an entry — it answers mode 0 and a 1970 date (piège #50) —
     * and this is not that. It is the smallest request the protocol has: one
     * packet out, one small packet back, no directory listing.
     */
    private probe;
}