(*  Title:      Tools/Code/code_namespace.ML

     Author:     Florian Haftmann, TU Muenchen

 Mastering target language namespaces.

 *)

 signature CODE_NAMESPACE =

 sig

   datatype ('a, 'b) node =

       Dummy

     | Stmt of 'a

     | Module of ('b * (string * ('a, 'b) node) Graph.T);

   val hierarchical_program: (string -> string) -> { module_alias: string -> string option,

     reserved: Name.context, empty_nsp: 'c, namify_module: string -> 'c -> string * 'c,

     namify_stmt: Code_Thingol.stmt -> string -> 'c -> string * 'c,

     cyclic_modules: bool, empty_data: 'b, memorize_data: string -> 'b -> 'b,

     modify_stmts: (string * Code_Thingol.stmt) list -> 'a option list }

       -> Code_Thingol.program

       -> { deresolver: string list -> string -> string,

            hierarchical_program: (string * ('a, 'b) node) Graph.T }

 end;

 structure Code_Namespace : CODE_NAMESPACE =

 struct

 (* hierarchical program structure *)

 datatype ('a, 'b) node =

     Dummy

   | Stmt of 'a

   | Module of ('b * (string * ('a, 'b) node) Graph.T);

 fun map_module_content f (Module content) = Module (f content);

 fun map_module [] = I

   | map_module (name_fragment :: name_fragments) =

       apsnd o Graph.map_node name_fragment o apsnd o map_module_content

         o map_module name_fragments;

 fun hierarchical_program labelled_name { module_alias, reserved, empty_nsp,

       namify_module, namify_stmt, cyclic_modules, empty_data, memorize_data, modify_stmts } program =

   let

     (* building module name hierarchy *)

     fun alias_fragments name = case module_alias name

      of SOME name' => Long_Name.explode name'

       | NONE => map (fn name => fst (yield_singleton Name.variants name reserved))

           (Long_Name.explode name);

     val module_names = Graph.fold (insert (op =) o fst o Code_Printer.dest_name o fst) program [];

     val fragments_tab = fold (fn name => Symtab.update

       (name, alias_fragments name)) module_names Symtab.empty;

     val dest_name = Code_Printer.dest_name #>> (the o Symtab.lookup fragments_tab);

     (* building empty module hierarchy *)

     val empty_module = (empty_data, Graph.empty);

     fun ensure_module name_fragment (data, nodes) =

       if can (Graph.get_node nodes) name_fragment then (data, nodes)

       else (data,

         nodes |> Graph.new_node (name_fragment, (name_fragment, Module empty_module)));

     fun allocate_module [] = I

       | allocate_module (name_fragment :: name_fragments) =

           ensure_module name_fragment

           #> (apsnd o Graph.map_node name_fragment o apsnd o map_module_content o allocate_module) name_fragments;

     val empty_program = Symtab.fold (fn (_, fragments) => allocate_module fragments)

       fragments_tab empty_module;

     (* distribute statements over hierarchy *)

     fun add_stmt name stmt =

       let

         val (name_fragments, base) = dest_name name;

       in

         (map_module name_fragments o apsnd) (Graph.new_node (name, (base, Stmt stmt)))

       end;

     fun add_dependency name name' =

       let

         val (name_fragments, base) = dest_name name;

         val (name_fragments', base') = dest_name name';

         val (name_fragments_common, (diff, diff')) =

           chop_prefix (op =) (name_fragments, name_fragments');

         val is_module = not (null diff andalso null diff');

         val dep = pairself hd (diff @ [name], diff' @ [name']);

         val add_edge = if is_module andalso not cyclic_modules

           then (fn node => Graph.add_edge_acyclic dep node

             handle Graph.CYCLES _ => error ("Dependency "

               ^ quote name ^ " -> " ^ quote name'

               ^ " would result in module dependency cycle"))

           else Graph.add_edge dep

       in (map_module name_fragments_common o apsnd) add_edge end;

     val proto_program = empty_program

       |> Graph.fold (fn (name, (stmt, _)) => add_stmt name stmt) program

       |> Graph.fold (fn (name, (_, (_, names))) => fold (add_dependency name) names) program;

     (* name declarations, data and statement modifications *)

     fun make_declarations nsps (data, nodes) =

       let

         val (module_fragments, stmt_names) = List.partition

           (fn name_fragment => case Graph.get_node nodes name_fragment

             of (_, Module _) => true | _ => false) (Graph.keys nodes);

         fun declare namify name (nsps, nodes) =

           let

             val (base, node) = Graph.get_node nodes name;

             val (base', nsps') = namify node base nsps;

             val nodes' = Graph.map_node name (K (base', node)) nodes;

           in (nsps', nodes') end;

         val (nsps', nodes') = (nsps, nodes)

           |> fold (declare (K namify_module)) module_fragments

           |> fold (declare (namify_stmt o (fn Stmt stmt => stmt))) stmt_names;

         val modify_stmts' = filter (member (op =) stmt_names)

           #> AList.make (snd o Graph.get_node nodes)

           #> split_list

           ##> map (fn Stmt stmt => stmt)

           #> (fn (names, stmts) => names ~~ modify_stmts (names ~~ stmts));

         val stmtss' = maps modify_stmts' (Graph.strong_conn nodes);

         val nodes'' = Graph.map (fn name => apsnd (fn Module content => Module (make_declarations nsps' content)

             | _ => case AList.lookup (op =) stmtss' name of SOME (SOME stmt) => Stmt stmt | _ => Dummy)) nodes';

         val data' = fold memorize_data stmt_names data;

       in (data', nodes'') end;

     val (_, hierarchical_program) = make_declarations empty_nsp proto_program;

     (* deresolving *)

     fun deresolver prefix_fragments name =

       let

         val (name_fragments, _) = dest_name name;

         val (_, (_, remainder)) = chop_prefix (op =) (prefix_fragments, name_fragments);

         val nodes = fold (fn name_fragment => fn nodes => case Graph.get_node nodes name_fragment

          of (_, Module (_, nodes)) => nodes) name_fragments hierarchical_program;

         val (base', _) = Graph.get_node nodes name;

       in Long_Name.implode (remainder @ [base']) end

         handle Graph.UNDEF _ => error ("Unknown statement name: " ^ labelled_name name);

   in { deresolver = deresolver, hierarchical_program = hierarchical_program } end;

 end;