/********************************************************************************
 * Copyright (c) 2026 CrossBreeze, EclipseSource and others.
 *
 * This program and the accompanying materials are made available under the
 * terms of the MIT License which is available in the project root.
 *
 * SPDX-License-Identifier: MIT
 ********************************************************************************/
import { DisposableCollection } from '@hydranium/protocol';
import { FrontendApplicationContribution } from '@theia/core/lib/browser/frontend-application-contribution';
import { ILogger } from '@theia/core/lib/common/logger';
import { PreferenceService } from '@theia/core/lib/common/preferences/preference-service';
import { type interfaces } from '@theia/core/shared/inversify';
/** Inversify token for the preference id {@link LogLevelPreferenceContribution} watches. */
export declare const LogLevelPreference: unique symbol;
/**
 * Applies the framework log threshold from a Theia preference, once per
 * application.
 *
 * **Why this is a `FrontendApplicationContribution` and not a logger concern.**
 * The threshold is a process-global (`Logger.setLevel`, read by every
 * `AbstractLogger` at emit time), so applying it is an *application* lifecycle
 * event. Applying it from a logger's `@postConstruct` instead puts a global side
 * effect on the construction of an object whose singleton scope is the
 * per-diagram container, which costs two things:
 *
 *  - the `onPreferenceChanged` subscription is never disposed AND is re-created
 *    for every diagram container, so opening N diagrams leaves N live listeners
 *    holding N loggers;
 *  - with no diagram open the preference is never applied at all, so anything
 *    logging before the first diagram runs at the default threshold.
 *
 * Bound by {@link bindLogLevelPreference} in the **frontend** container — a
 * diagram container is a child and cannot contribute to the parent's
 * multi-binding.
 */
export declare class LogLevelPreferenceContribution implements FrontendApplicationContribution {
    protected readonly preferenceName: string;
    protected readonly preferences: PreferenceService;
    protected readonly logger: ILogger;
    /** Holds the single preference subscription. `DisposableCollection` disposes a
     *  push-after-dispose immediately, so a subscription that lands after
     *  {@link onStop} cannot outlive the application either. */
    protected readonly toDispose: DisposableCollection;
    /** Guards against a second subscription if `onStart` is ever invoked twice —
     *  a duplicated listener is exactly the failure this contribution exists to
     *  prevent. */
    protected subscribed: boolean;
    /**
     * Returns `void` rather than the promise, so `FrontendApplication.start` does
     * NOT await it.
     *
     * This is load-bearing: `PreferenceService.ready` resolves only once the
     * preference providers are initialised, which happens as part of the same
     * startup sequence that runs the contributions, so awaiting it here deadlocks
     * the frontend on its preload splash. The threshold is therefore applied as
     * soon as preferences are ready, which is early but not synchronously before
     * the first possible log line.
     */
    onStart(): void;
    /** The awaited body of {@link onStart}, separated so it can be driven directly
     *  in tests without going through the non-awaited lifecycle hook. */
    protected applyWhenReady(): Promise<void>;
    onStop(): void;
    /**
     * Read the preference and apply it. An unparseable or unset value leaves the
     * current threshold alone rather than resetting it to a default — the value may
     * legitimately have been set by another source (an env baseline, a test).
     *
     * Override for a custom preference→level mapping.
     */
    protected applyLevel(): void;
}
/**
 * Bind {@link LogLevelPreferenceContribution} for `preferenceName`.
 *
 * Call from a **frontend** container module. Adopters using
 * `AbstractHydraniumGlspTheiaFrontendModule` set its `logLevelPreference` field
 * instead and the base calls this for them.
 */
export declare function bindLogLevelPreference(bind: interfaces.Bind, preferenceName: string): void;
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