import { AdhocDebugLogger } from './logging-utils';
/**
 * Possible log levels. These are a subset of Cloud Observability levels.
 * https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry#LogSeverity
 */
export declare enum LogSeverity {
    DEFAULT = "DEFAULT",
    DEBUG = "DEBUG",
    INFO = "INFO",
    WARNING = "WARNING",
    ERROR = "ERROR"
}
/**
 * A set of suggested log metadata fields.
 */
export interface LogFields {
    /**
     * Log level - undefined/null === DEFAULT.
     */
    severity?: LogSeverity;
    /**
     * If this log is associated with an OpenTelemetry trace, you can put the
     * trace ID here to pass on that association.
     */
    telemetryTraceId?: string;
    /**
     * If this log is associated with an OpenTelemetry trace, you can put the
     * span ID here to pass on that association.
     */
    telemetrySpanId?: string;
    /**
     * This is a catch-all for any other items you might want to go into
     * structured logs. Library implementers, please see the spec docs above
     * for the items envisioned to go here.
     */
    other?: unknown;
}
/**
 * When the user receives a log function (below), this will be the basic function
 * call interface for it.
 */
export interface AdhocDebugLogCallable {
    (fields: LogFields, ...args: unknown[]): void;
}
/**
 * Adds typing info for the EventEmitter we're adding to the returned function.
 */
export interface AdhocDebugLogFunction extends AdhocDebugLogCallable {
    instance: AdhocDebugLogger;
    on(event: 'log', listener: (fields: LogFields, args: unknown[]) => void): this;
    debug(...args: unknown[]): void;
    info(...args: unknown[]): void;
    warn(...args: unknown[]): void;
    error(...args: unknown[]): void;
    sublog(namespace: string): AdhocDebugLogFunction;
}
/**
 * One of these can be passed to support a third-party backend, like "debug".
 * We're splitting this out because ESM can complicate optional module loading.
 */
export interface DebugLogBackend {
    /**
     * Outputs a log to this backend.
     *
     * @param namespace The "system" that will be used for filtering. This may also
     * include a "subsystem" in the form "system:subsystem".
     * @param fields Logging fields to be included as metadata.
     * @param args Any parameters to passed to a utils.format() type formatter.
     */
    log(namespace: string, fields: LogFields, ...args: unknown[]): void;
    /**
     * Passes in the system/subsystem filters from the global environment variables.
     * This lets the backend merge with any native ones.
     *
     * @param filters A list of wildcards matching systems or system:subsystem pairs.
     */
    setFilters(filters: string[]): void;
}