exception ParsingError of string;;

let mk_app x y = Num.mk_app x y;;
let mk_lam x = `Lam(true, x);;
let mk_var x = `Var(x, -666);;

let isAlphaNum c = let n = Char.code c in
 (48 <= n && n <= 90) || (95 <= n && n <= 122) ;;
let isSpace c = c = ' ' || c = '\n' || c = '\t' ;;

(* FIXME *)
let mk_var' (bound, free) x =
  if List.mem x bound
  then free, mk_var (Util.index_of x bound)
  else if List.mem x free
       then free, mk_var (List.length bound + Util.index_of x free)
       else (free @ [x]), mk_var (List.length bound + List.length free)
;;

let mk_app' = function
  | [] ->  raise (ParsingError "bug")
  | t :: ts -> List.fold_left mk_app t ts
;;

let explode s =
  let rec aux i l =
    if i < 0 then l else aux (i - 1) (s.[i] :: l)
  in aux (String.length s - 1) []
;;

let implode l =
  let res = String.create (List.length l) in
  let rec aux i = function
    | [] -> res
    | c :: l -> res.[i] <- c; aux (i + 1) l in
  aux 0 l
;;

let rec strip_spaces = function
  | c::cs when isSpace c -> strip_spaces cs
  | cs -> cs
;;

let read_var s =
  let rec aux = function
  | [] -> None, []
  | c::cs as x -> if isAlphaNum c
    then match aux cs with
         | (Some x), cs' -> Some (c :: x), cs'
         | None, cs' -> (Some [c]), cs'
    else None, x
  in match aux s with
    | None, y -> None, y
    | Some x, y -> Some (implode x), y
;;

let read_var' (bound, free as vars) s =
  match read_var s with
  | Some varname, cs ->
    let free, v = mk_var' vars varname in
    Some [v], cs, (bound, free)
  | _, _ -> raise (ParsingError ("Can't read variable"))
;;

let rec read_smt vars =
  let check_if_lambda cs = match read_var cs with
    | None, _ -> false
    | Some x, cs -> match strip_spaces cs with
      | [] -> false
      | c::_ -> c = '.'
  in let read_lambda (bound, free) cs = (
    match read_var (strip_spaces cs) with
      | Some varname, cs ->
      let vars' = (varname::bound, free) in
      (match strip_spaces cs with
        | [] -> raise (ParsingError "manca dopo variabile lambda")
        | c::cs -> (if c = '.' then (match read_smt vars' cs with
          | None, _, _ -> raise (ParsingError "manca corpo lambda")
          | Some [x], y, (_, free) -> Some [mk_lam x], y, (bound, free)
          | Some _, _, _ -> raise (ParsingError "???")
          ) else raise (ParsingError "manca . nel lambda")
        ))
      | _, _ -> assert false
 ) in let rec aux vars cs =
  match strip_spaces cs with
  | [] -> None, [], vars
  | c::_ as x ->
      let tms, cs, vars = (
           if c = '(' then read_pars vars x
      else if c = ')' then (None, x, vars)
      else if check_if_lambda x then read_lambda vars x
      else read_var' vars x) in
      match tms with
      | Some [tm] -> (
        match aux vars cs with
          | None, cs, vars -> Some [tm], cs, vars
          | Some ts, cs, vars -> Some (tm :: ts), cs, vars
        )
      | Some _ -> raise (ParsingError "bug")
      | None -> None, x, vars
  in fun cs -> match aux vars cs with
    | None, cs, vars -> None, cs, vars
    | Some ts, cs, vars -> Some [mk_app' ts], cs, vars
and read_pars vars = function
  | [] -> None, [], vars
  | c::cs -> if c = '(' then (
    let tm, cs, vars = read_smt vars cs in
    let cs = strip_spaces cs in
    match cs with
      | [] -> None, [], vars
      | c::cs -> if c = ')' then tm, cs, vars else raise (ParsingError ") mancante")
    ) else raise (ParsingError "???")
;;

let parse x =
  match read_smt ([],[]) (explode x) with
  | Some [y], [], _ -> y
  | _, _, _ -> raise (ParsingError "???")
;;

let parse_many strs =
  let f (x, y) z = match read_smt y (explode z) with
  | Some[tm], [], vars -> (tm :: x, vars)
  | _, _, _ -> raise (ParsingError "???")
  in let aux = List.fold_left f ([], ([], [])) (* index zero is reserved *)
  in let (tms, (_, free)) = aux strs
  in (List.rev tms, free)
;;

let problem_of_string s =
 let lines = Str.split (Str.regexp "[\n\r\x0c\t;]+") s in
 let head, lines = List.hd lines, List.tl lines in
 let name = String.trim (String.sub head 1 (String.length head - 1)) in
 let lines = List.filter ((<>) "") lines in
 let aux (last, div, conv, ps) line =
  let chr = String.sub line 0 1 in
  let line = String.trim (String.sub line 1 (String.length line - 1)) in
  if line = "" then chr, div, conv, ps else
  let rec aux' chr line =
   if chr = "#"
    then chr, div, conv, ps
   else if chr = "D"
    then chr, line, conv, ps
   else if chr = "C"
    then chr, div, line::conv, ps
   else if chr = "N"
    then chr, div, conv, line::ps
   else if chr = " "
    then aux' last line
   else raise (ParsingError
     ("Unexpected at beginning of problem: `" ^ chr ^ "` " ^ line)) in
  aux' chr line in
 let _, div, conv, ps = List.fold_left aux ("#", "", [], []) lines in
 let div_provided = div <> "" in
 let div = if div_provided then div else "xxxxxx" in
 let strs = [div] @ ps @ conv in

 if List.length ps = 0 && List.length conv = 0
  then raise (ParsingError "empty problem");

 (* parse' *)
 let (tms, free) = parse_many strs in
 let n_bot = try Util.index_of "BOT" free with Not_found -> min_int in
 let n_pac = try Util.index_of "PAC" free with Not_found -> min_int in
 let n_bomb = try Util.index_of "BOMB" free with Not_found -> min_int in
 let fix lev v =
 if v = lev + n_bot then failwith "Example with `Bottom"
  else if v = lev + n_pac then failwith "Example with `Pacman"
   else if v = lev + n_bomb then failwith "Example with `Bomb"
    else if v = lev then `Var(v, min_int) (* zero *)
      else `Var(v,1) in (* 1 by default when variable not applied *)
 (* Fix arity *)
 let open Num in
 let rec aux lev : nf -> nf = function
 | `I((n,_), args) -> `I((n,(if lev = 0 then 0 else 1) + Listx.length args), Listx.map (aux lev) args)
 | `Var(n,_) -> fix lev n
 | `Lam(_,t) -> `Lam (true, aux (lev+1) t)
 | `Match _ | `N _ -> assert false in
let all_tms = List.map (aux 0) (tms :> Num.nf list) in

(* problem_of *)
let div, (ps, conv) = List.hd all_tms, Util.list_cut (List.length ps, List.tl all_tms) in

let div = if not div_provided
 then None
 else match div with
  | `I _ as t -> Some t
  | _ -> raise (ParsingError "div is not an inert or BOT in the initial problem") in
let conv = Util.filter_map (
 function
 | #i_n_var as t -> Some t
 | `Lam _ -> None
 | _ -> raise (ParsingError "A term in conv is not i_n_var")
 ) conv in
let ps = List.map (
 function
  | #i_n_var as y -> y
  | _ as y -> raise (ParsingError ("A term in num is not i_n_var" ^ Num.string_of_nf y))
 ) ps in
 name, div, conv, ps, free
;;


let from_file path =
 let lines = ref ["#"] in
 let chan = open_in path in
 let _ = try
  while true; do
    lines := input_line chan :: !lines
  done
 with End_of_file ->
  close_in chan in
 let txt = String.concat "\n" (List.rev !lines) in
 let problems = Str.split (Str.regexp "[\n\r]+\\$") txt in
 List.map problem_of_string (List.tl (List.map ((^) "$") problems))
;;