(*
    ||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
                   | LEnv of 'a
                   | Warn of string
		   | String of string
                   | Loc

type ('a, 'b) message = ('a, 'b) item list

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

let level = ref 0

let loc = ref "unknown location"

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

let std = F.std_formatter

let err = F.err_formatter

let pp_items frm st l items =   
   let pp_item frm = function
      | Term (c, t) -> F.fprintf frm "@,%a" (st.pp_term c) t
      | LEnv c      -> F.fprintf frm "%a" st.pp_lenv c
      | Warn s      -> F.fprintf frm "@,%s" s
      | String s    -> F.fprintf frm "%s " s
      | Loc         -> F.fprintf frm " <%s>" !loc 
   in
   let iter map frm l = List.iter (map frm) l in
   if !level >= l then F.fprintf frm "%a" (iter pp_item) items

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

let box l = 
   if !level >= l then
   begin F.fprintf std "@,@[<v 2>%s" "  "; F.pp_print_if_newline std () end

let unbox l = if !level >= l then F.fprintf std "@]"

let flush l = if !level >= l then F.fprintf std "@]@."

let box_err () = F.fprintf err "@[<v>"

let flush_err () = F.fprintf err "@]@."

let log st l items = pp_items std st l items

let error st items = pp_items err st 0 items

let items1 s = [Warn s]

let t_items1 st c t =
   [Warn st; Term (c, t)]

let et_items1 sc c st t =
   [Warn sc; LEnv c; Warn st; Term (c, t)]

let et_items2 sc1 c1 st1 t1 ?sc2 ?c2 st2 t2 =
   let tl = match sc2, c2 with
      | Some sc2, Some c2 -> et_items1 sc2 c2 st2 t2
      | None, None        -> t_items1 st2 c1 t2
      | _                 -> assert false
   in
   et_items1 sc1 c1 st1 t1 @ tl  

let et_items3 sc1 c1 st1 t1 ?sc2 ?c2 st2 t2 ?sc3 ?c3 st3 t3 =
   let tl = match sc3, c3 with
      | Some sc3, Some c3 -> et_items1 sc3 c3 st3 t3
      | None, None        -> t_items1 st3 c1 t3 
      | _                 -> assert false
   in   
   et_items2 sc1 c1 st1 t1 ?sc2 ?c2 st2 t2 @ tl 

let warn msg = F.fprintf std "@,%s" msg