@microsoft/signalr/src/ILogger.ts

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

// These values are designed to match the ASP.NET Log Levels since that's the pattern we're emulating here.
/** Indicates the severity of a log message.
 *
 * Log Levels are ordered in increasing severity. So `Debug` is more severe than `Trace`, etc.
 */
export enum LogLevel {
    /** Log level for very low severity diagnostic messages. */
    Trace = 0,
    /** Log level for low severity diagnostic messages. */
    Debug = 1,
    /** Log level for informational diagnostic messages. */
    Information = 2,
    /** Log level for diagnostic messages that indicate a non-fatal problem. */
    Warning = 3,
    /** Log level for diagnostic messages that indicate a failure in the current operation. */
    Error = 4,
    /** Log level for diagnostic messages that indicate a failure that will terminate the entire application. */
    Critical = 5,
    /** The highest possible log level. Used when configuring logging to indicate that no log messages should be emitted. */
    None = 6,
}

/** An abstraction that provides a sink for diagnostic messages. */
export interface ILogger {
    /** Called by the framework to emit a diagnostic message.
     *
     * @param {LogLevel} logLevel The severity level of the message.
     * @param {string} message The message.
     */
    log(logLevel: LogLevel, message: string): void;
}