(*
    ||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_______________________________________________________________ *)

(* $Id: nCicRefiner.mli 9227 2008-11-21 16:00:06Z tassi $ *)

module COT : Set.OrderedType with type t = int * NCic.term = 
  struct
        type t = int * NCic.term
        let compare = Pervasives.compare
  end

module HintSet = Set.Make(COT)

module DB = 
  Discrimination_tree.Make(NDiscriminationTree.NCicIndexable)(HintSet)

type db = DB.t

class status =
 object
  val db = DB.empty
  method uhint_db = db
  method set_uhint_db v = {< db = v >}
  method set_unifhint_status
   : 'status. < uhint_db : db; .. > as 'status -> 'self
   = fun o -> {< db = o#uhint_db >}
 end

let dummy = NCic.Const (NReference.reference_of_string "cic:/dummy_conv.dec");;
let pair t1 t2 = (NCic.Appl [dummy;t1;t2]) ;;

let index_hint hdb context t1 t2 precedence =
  assert (
    (match t1 with
    | NCic.Meta _ | NCic.Appl (NCic.Meta _ :: _) -> false | _ -> true)
    &&
    (match t2 with
    | NCic.Meta _ | NCic.Appl (NCic.Meta _ :: _) -> false | _ -> true)
  );
  let pair' = pair t1 t2 in
  let data = 
    List.fold_left 
     (fun t (n,e) -> 
        match e with
        | NCic.Decl ty -> NCic.Prod (n,ty,t)
        | NCic.Def (b,ty) -> NCic.LetIn (n,ty,b,t))
      pair' context in
  let src = 
    List.fold_left 
     (fun t (_,e) -> 
        match e with
        | NCic.Decl _ -> 
            NCicSubstitution.subst (NCic.Meta (-1,(0,NCic.Irl 0))) t
        | NCic.Def _ -> 
            NCicSubstitution.subst (NCic.Meta (-1,(0,NCic.Irl 0))) t)
     pair' context in
(*
  prerr_endline ("INDEXING: " ^ 
    NCicPp.ppterm ~metasenv:[] ~subst:[] ~context:[] src ^ " |==> " ^
    NCicPp.ppterm ~metasenv:[] ~subst:[] ~context:[] data);
*)
  hdb#set_uhint_db (DB.index hdb#uhint_db src (precedence, data))
;;

let add_user_provided_hint db t precedence =
  let c, a, b = 
    let rec aux ctx = function
      | NCic.Appl l ->
          (match List.rev l with
          | b::a::_ -> ctx, a, b
          | _ -> assert false)
      | NCic.Prod (n,s,t) -> aux ((n, NCic.Decl s) :: ctx) t
      | NCic.LetIn (n,ty,t,b) -> aux  ((n, NCic.Def (t,ty)) :: ctx) b
      | _ -> assert false
    in
      aux [] t
  in
   index_hint db c a b precedence
;;

let db () = 
  let combine f l =
   List.flatten
     (let rec aux = function 
      | u1 :: tl -> List.map (f u1) tl :: aux tl
      | [] -> []
     in aux l)
  in
  let mk_hint (u1,_,_) (u2,_,_) = 
    let l = OCic2NCic.convert_obj u1 
      (fst (CicEnvironment.get_obj CicUniv.oblivion_ugraph u1)) in
    let r = OCic2NCic.convert_obj u2 
      (fst (CicEnvironment.get_obj CicUniv.oblivion_ugraph u2)) in
    match List.hd l,List.hd r with
    | (_,h1,_,_,NCic.Constant (_,_,Some l,_,_)), 
      (_,h2,_,_,NCic.Constant (_,_,Some r,_,_)) ->
        let rec aux ctx t1 t2 =
          match t1, t2 with
          | NCic.Lambda (n1,s1,b1), NCic.Lambda(_,s2,b2) ->
              if NCicReduction.are_convertible ~subst:[] ~metasenv:[] ctx s1 s2
              then aux ((n1, NCic.Decl s1) :: ctx) b1 b2
              else []
          | b1,b2 -> 
              if NCicReduction.are_convertible ~subst:[] ~metasenv:[] ctx b1 b2 
              then begin
(*
                prerr_endline ("hint: " ^ NCicPp.ppterm ~metasenv:[] ~subst:[]
                  ~context:ctx b1 ^ " === " ^ NCicPp.ppterm ~metasenv:[]
                  ~subst:[] ~context:ctx b2);
*)
              let rec mk_rels =  
                 function 0 -> [] | n -> NCic.Rel n :: mk_rels (n-1) 
              in 
              let n1 = 
                NCic.Appl (NCic.Const(OCic2NCic.reference_of_ouri 
                 u1 (NReference.Def h1)) :: mk_rels (List.length ctx))
              in
              let n2 = 
                NCic.Appl (NCic.Const(OCic2NCic.reference_of_ouri 
                 u2 (NReference.Def h2)) :: mk_rels (List.length ctx))
              in
                [ctx,b1,b2; ctx,b1,n2; ctx,n1,b2; ctx,n1,n2]
              end else []
        in
          aux [] l r
    | _ -> []
  in
  let hints = 
    List.fold_left 
      (fun acc (_,_,l) -> 
          acc @ 
          if List.length l > 1 then 
           combine mk_hint l
          else [])
      [] (CoercDb.to_list (CoercDb.dump ()))
  in
  prerr_endline "MISTERO";
  assert false (* ERA
  List.fold_left 
    (fun db -> function 
     | (ctx,b1,b2) -> index_hint db ctx b1 b2 0)
    !user_db (List.flatten hints)
*)
;;

let saturate ?(delta=0) metasenv subst context ty goal_arity =
 assert (goal_arity >= 0);
  let rec aux metasenv = function
   | NCic.Prod (name,s,t) as ty ->
       let metasenv1, _, arg,_ = 
          NCicMetaSubst.mk_meta ~name:name metasenv context (`WithType s) in
       let t, metasenv1, args, pno = 
           aux metasenv1 (NCicSubstitution.subst arg t) 
       in
       if pno + 1 = goal_arity then
         ty, metasenv, [], goal_arity+1
       else
         t, metasenv1, arg::args, pno+1
   | ty ->
        match NCicReduction.whd ~subst context ty ~delta with
        | NCic.Prod _ as ty -> aux metasenv ty
        | _ -> ty, metasenv, [], 0 (* differs from the other impl in this line*)
  in
  let res, newmetasenv, arguments, _ = aux metasenv ty in
  res, newmetasenv, arguments
;;

let look_for_hint hdb metasenv subst context t1 t2 =
(*
  prerr_endline ("KEY1: "^NCicPp.ppterm ~metasenv ~subst ~context (pair t1 t2));
  prerr_endline ("KEY2: "^NCicPp.ppterm ~metasenv ~subst ~context (pair t2 t1));
  DB.iter hdb
   (fun p ds ->
      prerr_endline ("ENTRY: " ^
      NDiscriminationTree.NCicIndexable.string_of_path p ^ " |--> " ^
      String.concat "|" (List.map (NCicPp.ppterm ~metasenv:[] ~subst:[]
      ~context:[]) (HintSet.elements ds))));
*)
  let candidates1 = DB.retrieve_unifiables hdb#uhint_db (pair t1 t2) in
  let candidates2 = DB.retrieve_unifiables hdb#uhint_db (pair t2 t1) in
  let candidates1 = 
    List.map (fun (prec,ty) -> 
       prec,true,saturate ~delta:max_int metasenv subst context ty 0) 
    (HintSet.elements candidates1) 
  in
  let candidates2 = 
    List.map (fun (prec,ty) -> 
       prec,false,saturate ~delta:max_int metasenv subst context ty 0) 
    (HintSet.elements candidates2) 
  in
  let rc = 
    List.map
      (fun (p,b,(t,m,_)) ->
         let rec aux () (m,l as acc) = function
           | NCic.Meta _ as t -> acc, t
           | NCic.LetIn (name,ty,bo,t) ->
               let m,_,i,_=
                 NCicMetaSubst.mk_meta ~name m context (`WithType ty)in
               let t = NCicSubstitution.subst i t in
               aux () (m, (i,bo)::l) t
           | t -> NCicUntrusted.map_term_fold_a (fun _ () -> ()) () aux acc t
         in
         let (m,l), t = aux () (m,[]) t in
         p,b,(t,m,l))
   (candidates1 @ candidates2)
  in
  let rc = 
  List.map
   (function 
    | (prec,true,(NCic.Appl [_; t1; t2],metasenv,l))-> prec,metasenv,(t1,t2),l
    | (prec,false,(NCic.Appl [_; t1; t2],metasenv,l))-> prec,metasenv,(t2,t1),l
    | _ -> assert false)
    rc
  in
  let rc = 
    List.sort (fun (x,_,_,_) (y,_,_,_) -> Pervasives.compare x y) rc
  in 
  let rc = List.map (fun (_,x,y,z) -> x,y,z) rc in
(*
    prerr_endline "Hints:";
    List.iter 
      (fun (metasenv, (t1, t2), premises) ->
          prerr_endline 
          ("\t" ^ String.concat ";  "
                (List.map (fun (a,b) -> 
                   NCicPp.ppterm ~margin:max_int ~metasenv ~subst ~context a ^
                   " =?= "^
                   NCicPp.ppterm ~margin:max_int ~metasenv ~subst ~context b)
                premises) ^     
              "  ==> "^
              NCicPp.ppterm ~margin:max_int ~metasenv ~subst ~context t1 ^
              " = "^NCicPp.ppterm ~margin:max_int ~metasenv ~subst ~context t2))
      rc;
*)
  rc
;;