(*
    ||M||  This file is part of HELM, an Hypertextual, Electronic        
    ||A||  Library of Mathematics, developed at the Computer Science     
    ||T||  Department, University of Bologna, Italy.                     
    ||I||                                                                
    ||T||  HELM is free software; you can redistribute it and/or         
    ||A||  modify it under the terms of the GNU General Public License   
    \   /  version 2 or (at your option) any later version.              
     \ /   This software is distributed as is, NO WARRANTY.              
      V_______________________________________________________________ *)

module P = Printf
module F = Format
module C = Cps

type ('a, 'b) item = Term of 'a * 'b
                   | Context of 'a
                   | Warn of string
		   | String of string

type ('a, 'b) specs = {
   pp_term   : F.formatter -> 'a -> 'b -> unit;
   pp_context: F.formatter -> 'a -> unit
}

let level = ref 0

(* Internal functions *******************************************************)

let init =
   let started = ref false in
   fun () ->
      if !started then () else 
      begin P.printf "\n"; started := true end

let pp_items frm st l items =   
   let pp_item = function
      | Term (c, t) -> st.pp_context frm c; st.pp_term frm c t
      | Context c   -> st.pp_context frm c
      | Warn s      -> F.fprintf frm "@[%s\n@]" s
      | String s    -> F.fprintf frm "@[%s @]" s
   in
   if !level >= l then List.iter pp_item items

(* Interface functions ******************************************************)

let warn msg = 
   init (); P.printf " %s\n" msg; flush stdout

let log st l items = pp_items F.std_formatter st l items

let error st items = pp_items F.err_formatter st 0 items

let items1 s = [Warn s]

let ct_items1 s c t =
   [Warn s; Term (c, t)]

let ct_items2 s1 c1 t1 s2 c2 t2 =
   [Warn s1; Term (c1, t1); Warn s2; Term (c2, t2)]