import { LogHook } from "./hooks.js";
/**
 * A simple logger that can be used to log structured data
 */
export default class Logger {
    /**
     * The function to call to output a JSON line log message
     */
    private readonly out;
    /**
     * Base fields that will be included in every log message sent by this logger
     */
    private readonly baseFields;
    /**
     * The level this logger is configured to log at
     */
    private readonly logLevel;
    /**
     * Any hooks that have been added to this logger
     */
    private readonly hooks;
    /**
     * Creates a new logger
     * @param out The function to call to output the JSON based log message
     * @param baseFields Any fields to include in every log message
     * @param hooks Any hooks to apply to every log message
     */
    constructor(out: (obj: unknown) => void, baseFields?: FieldsObject, hooks?: LogHook[]);
    /**
     * Trace logs a message at the trace level
     */
    trace(msg: string, fields?: FieldsObject): void;
    /**
     * Debug logs a message at the debug level
     */
    debug(msg: string, fields?: FieldsObject): void;
    /**
     * Info logs a message at the info level
     */
    info(msg: string, fields?: FieldsObject): void;
    /**
     * Warn logs a message at the warn level
     */
    warn(err: Error | unknown, fields?: FieldsObject): void;
    warn(err: Error | unknown, msg: string, fields?: FieldsObject): void;
    warn(msg: string, fields?: FieldsObject): void;
    /**
     * Error logs a message at the error level
     */
    error(err: Error | unknown, fields?: FieldsObject): void;
    error(err: Error | unknown, msg: string, fields?: FieldsObject): void;
    error(msg: string, fields?: FieldsObject): void;
    /**
     * Fatal logs a message at the fatal level
     */
    fatal(err: Error, fields?: FieldsObject): void;
    fatal(err: Error, msg: string, fields?: FieldsObject): void;
    fatal(msg: string, fields?: FieldsObject): void;
    /**
     * with returns a new logger with the given fields added to all log messages
     * created by it
     */
    with(fields: FieldsObject): Logger;
    /**
     * hook returns a new logger with the given hooks applied to all log messages
     * on top of any existing hooks this logger has
     */
    hook(...newHooks: LogHook[]): Logger;
    /**
     * the actual logging implementation
     */
    private log;
}
/**
 * A field value we support logging
 */
export type FieldValue = string | number | boolean | null | undefined | FieldsObject | FieldValue[];
/**
 * A map of fields that can be logged
 */
export type FieldsObject = Record<string, FieldValue>;