(* Data structures for representing the state of a system *)

open Util
open Ast

exception Combinatorial_cycle of string
exception No_variable of string
exception Type_error of string
let type_error e = raise (Type_error e)
exception Not_implemented of string
let not_implemented e = raise (Not_implemented e)

type scope = string

type svalue =
  | VInt of int
  | VBool of bool
  | VReal of float
  | VState of id
  | VPrevious of value
  | VBusy   (* intermediate value : calculating ! for detection of cycles *)
and value = svalue list

type state = svalue VarMap.t

(* functions for recursively getting variables *)

type calc_fun = 
  | F of (state -> calc_map -> state)
and calc_map = calc_fun VarMap.t

let get_var (st: state) (c: calc_map) (id: id) : (state * svalue) =
  let st =
    if VarMap.mem id st then st
    else try match VarMap.find id c with
    | F f ->
      Format.printf "%s[ " id;
      let r = f (VarMap.add id VBusy st) c in
      Format.printf "]%s " id;
      r
    with Not_found -> raise (No_variable id)
  in
    match VarMap.find id st with
    | VBusy -> raise (Combinatorial_cycle id)
    | v -> st, v

(* pretty-printing *)

let rec str_of_value = function
  | VInt i -> string_of_int i
  | VReal r -> string_of_float r
  | VBool b -> if b then "true" else "false"
  | VState s -> "state " ^ s
  | VPrevious p ->
    "[" ^
      List.fold_left (fun s v -> (if s = "" then "" else s ^ ", ") ^ str_of_value v) "" p
      ^ "]"
  | VBusy -> "#"
let print_state st =
  VarMap.iter (fun id v -> Format.printf "%s = %s@." id (str_of_value v)) st