type logger

type level =
  | TRACE
  | DEBUG
  | INFO
  | WARN
  | ERROR

(* log_function (fun m -> m "<fmt>" <args>); *)
type 'a log_function =
  ((('a, Format.formatter, unit) format -> 'a) -> unit) -> unit

type 'a log_module_function =
  ?__POS__:(string * int * int * int)
  -> ?__FUNCTION__:string
  -> ?errno:int
  -> ('a log_function)

module type Logs = sig
  val logger : logger
  val trace : _ log_module_function
  val debug : _ log_module_function
  val info  : _ log_module_function
  val warn  : _ log_module_function
  val error : _ log_module_function
  val exn   : exn -> Printexc.raw_backtrace -> _ log_module_function
  val log   : level -> ?exn:((exn * Printexc.raw_backtrace) option) -> _ log_module_function
end

val logs : string -> (module Logs)
val sublogs : logger -> string -> (module Logs)

val init_pretty_writer :
  ?min_level:level ->
  ?color:bool ->
  ?timestamp:bool ->
  ?namespace:bool ->
  ?level:bool ->
  ?source_loc:bool ->
  ?backtrace:bool ->
  out_channel -> unit

val init_journald_writer :
  ?min_level:level ->
  ?path:string ->
  unit -> unit

val should_upgrade_to_journald : unit -> bool