signature QUOTIENT_INFO =
sig
  type maps_info = {mapfun: string, relfun: string}
  val maps_lookup: theory -> string -> maps_info option
  val maps_update_thy: string -> maps_info -> theory -> theory    
  val maps_update: string -> maps_info -> Proof.context -> Proof.context     

  type quotient_info = {qtyp: typ, rtyp: typ, rel: term, equiv_thm: thm}
  val print_quotdata: Proof.context -> unit
  val quotdata_lookup_thy: theory -> quotient_info list
  val quotdata_lookup: Proof.context -> quotient_info list
  val quotdata_update_thy: (typ * typ * term * thm) -> theory -> theory
  val quotdata_update: (typ * typ * term * thm) -> Proof.context -> Proof.context
end;

structure Quotient_Info: QUOTIENT_INFO =
struct

(* data containers *)
(*******************)

(* info about map- and rel-functions *)
type maps_info = {mapfun: string, relfun: string}

structure MapsData = TheoryDataFun
  (type T = maps_info Symtab.table
   val empty = Symtab.empty
   val copy = I
   val extend = I
   fun merge _ = Symtab.merge (K true))

val maps_lookup = Symtab.lookup o MapsData.get


fun maps_update_thy k minfo = MapsData.map (Symtab.update (k, minfo))
fun maps_update k minfo = ProofContext.theory (maps_update_thy k minfo)

fun maps_attribute_aux s minfo = Thm.declaration_attribute 
  (fn thm => Context.mapping (maps_update_thy s minfo) (maps_update s minfo))

(* attribute to be used in declare statements *)
fun maps_attribute (ctxt, (tystr, (mapstr, relstr))) = 
let  
  val thy = ProofContext.theory_of ctxt
  val tyname = Sign.intern_type thy tystr
  val mapname = Sign.intern_const thy mapstr
  val relname = Sign.intern_const thy relstr
in
  maps_attribute_aux tyname {mapfun = mapname, relfun = relname}
end

val maps_attr_parser = 
      Args.context -- Scan.lift
       ((Args.name --| OuterParse.$$$ "=") -- 
         (OuterParse.$$$ "(" |-- Args.name --| OuterParse.$$$ "," -- 
           Args.name --| OuterParse.$$$ ")"))

val _ = Context.>> (Context.map_theory
         (Attrib.setup @{binding "map"} (maps_attr_parser >> maps_attribute) 
           "declaration of map information"))


(* info about the quotient types *)
type quotient_info = {qtyp: typ, rtyp: typ, rel: term, equiv_thm: thm}

structure QuotData = TheoryDataFun
  (type T = quotient_info list
   val empty = []
   val copy = I
   val extend = I
   fun merge _ = (op @)) (* FIXME: is this the correct merging function for the list? *)

val quotdata_lookup_thy = QuotData.get
val quotdata_lookup = QuotData.get o ProofContext.theory_of

fun quotdata_update_thy (qty, rty, rel, equiv_thm) thy = 
      QuotData.map (fn ls => {qtyp = qty, rtyp = rty, rel = rel, equiv_thm = equiv_thm}::ls) thy

fun quotdata_update (qty, rty, rel, equiv_thm) ctxt = 
      ProofContext.theory (quotdata_update_thy (qty, rty, rel, equiv_thm)) ctxt

fun print_quotdata ctxt =
let
  fun prt_quot {qtyp, rtyp, rel, equiv_thm} = 
      Pretty.block (Library.separate (Pretty.brk 2)
          [Pretty.str ("quotient type:"), 
           Syntax.pretty_typ ctxt qtyp,
           Pretty.str ("raw type:"), 
           Syntax.pretty_typ ctxt rtyp,
           Pretty.str ("relation:"), 
           Syntax.pretty_term ctxt rel,
           Pretty.str ("equiv. thm:"), 
           Syntax.pretty_term ctxt (prop_of equiv_thm)])
in
  QuotData.get (ProofContext.theory_of ctxt)
  |> map prt_quot
  |> Pretty.big_list "quotients:" 
  |> Pretty.writeln
end

val _ = 
  OuterSyntax.improper_command "print_quotients" "print out all quotients" 
    OuterKeyword.diag (Scan.succeed (Toplevel.keep (print_quotdata o Toplevel.context_of)))

end; (* structure *)

open Quotient_Info