// @flow

export interface Logger {
  trace: (...args: Array<any>) => void;
  debug: (...args: Array<any>) => void;
  info: (...args: Array<any>) => void;
  warn: (...args: Array<any>) => void;
  error: (...args: Array<any>) => void;
  fatal: (...args: Array<any>) => void;
  logAtLevel: (level: number, ...args: Array<any>) => void;
  levelEnabled: (level: number) => boolean;
  inputLogProvider: LogProvider;
}

export type LogProvider = (
  loggerPath: string,
  level: number,
  ...args: Array<any>
) => void

export type LogFunctionProvider = (level: number) => Function

export type Level = 1 | 2 | 3 | 4 | 5 | 6

export const LOG_LEVEL_TRACE = 1
export const LOG_LEVEL_DEBUG = 2
export const LOG_LEVEL_INFO = 3
export const LOG_LEVEL_WARN = 4
export const LOG_LEVEL_ERROR = 5
export const LOG_LEVEL_FATAL = 6

declare export var logLevelToName: { [Level]: string }

declare export function envVarChanged(varName: ?string, newValue: ?string): void
declare export function resetLogLevels(): void
declare export function setLogLevel(path: string, level: number): void

/**
 * Simple hook to override the logging function. For example, to always log to console.error,
 * call setLogFunctionProvider(() => console.error)
 * @param provider function that returns the log function based on the message's log level
 */
declare export function setLogFunctionProvider(
  provider: LogFunctionProvider
): void

declare export function createDefaultLogProvider(logFunc: Function): LogProvider

declare export var defaultLogProvider: LogProvider

/**
 * Hook to provide a complete replacement for the log provider.
 * @param provider
 */
declare export function setLogProvider(provider: LogProvider): void

export type CreateLoggerOptions = {
  loggerPath: string,
  logProviders?: LogProvider[],
}

declare export function createLogger(options: CreateLoggerOptions): Logger

declare export function logger(loggerPath?: string): Logger
declare export default function logger(loggerPath?: string): Logger