(* Copyright 2014 Guillaume Bury *)

exception Syntax_error of int

type line =
    | Empty
    | Comment
    | Pcnf of int * int
    | Clause of int list

let ssplit = Str.split (Str.regexp "[ \t]+")

let of_input f =
    match ssplit (input_line f) with
    | [] -> Empty
    | "c" :: _ -> Comment
    | "p" :: "cnf" :: i :: j :: [] ->
            begin try
                Pcnf (int_of_string i, int_of_string j)
            with Invalid_argument _ ->
                raise (Syntax_error (-1))
            end
    | l ->
            begin try
              begin match List.rev_map int_of_string l with
              | 0 :: r -> Clause r
              | _ -> raise (Syntax_error (-1))
              end
            with Invalid_argument _ -> raise (Syntax_error (-1))
            end

let parse_with todo file =
    let f = open_in file in
    let line = ref 0 in
    try
        while true do
            incr line;
            todo (of_input f)
        done
    with
    | Syntax_error _ ->
        raise (Syntax_error !line)
    | End_of_file ->
        close_in f

let cnf = ref []
let parse_line = function
    | Empty | Comment | Pcnf _ -> ()
    | Clause l -> cnf := l :: !cnf

let parse f =
    cnf := [];
    parse_with parse_line f;
    !cnf