(*
 *
 *)

open Mathql;;

(*
 * conversione di un pattern
 *)
let rec patterneval p =
 match p with
   [] -> ""
 | head::tail ->
    let h = match head with
               MQString (s) -> s
            |  MQSlash -> "/"
            |  MQAnyChr -> "[^/]?"
            |  MQAst -> "[^/]*"
            |  MQAstAst -> ".*"
    in
     h ^ (patterneval tail)
;;

(*
 * conversione di un fragment identifier
 *)
let fieval fi =
 match fst fi with
    None -> ""
 |  Some i ->
     let s = "#xpointer\(1/" ^ string_of_int (i) in
      match snd fi with
         None ->
	  s ^ "\)"
      |  Some j ->
	  s ^ "/" ^ string_of_int j ^ "\)"
;;

(*
 * trasforma un pattern MathQL in un pattern postgresql
 *
 * si utilizzano espressioni regolari POSIX anziche' l'operatore
 * SQL standard LIKE perche' MathQL prevede esperssioni con "*"
 * e con "**".
 *)
let pattern_match preamble pattern ext fragid =
 " ~ '" ^ preamble ^ ":/" ^ (patterneval pattern) ^ "." ^ ext ^ (fieval fragid) ^ "'"
;;