(*  Title:      Tools/Code/code_namespace.ML

     Author:     Florian Haftmann, TU Muenchen

 Mastering target language namespaces.

 *)

 signature CODE_NAMESPACE =

 sig

   type flat_program

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

     module_prefix: string, reserved: Name.context, empty_nsp: 'a,

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

     modify_stmt: Code_Thingol.stmt -> Code_Thingol.stmt option }

       -> Code_Thingol.program

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

            flat_program: flat_program }

   datatype ('a, 'b) node =

       Dummy

     | Stmt of 'a

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

   type ('a, 'b) hierarchical_program

   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: ('a, 'b) hierarchical_program }

   val print_hierarchical: { print_module: string list -> string -> 'b -> 'c list -> 'c,

     print_stmt: string list -> string * 'a -> 'c,

     lift_markup: (Pretty.T -> Pretty.T) -> 'c -> 'c }

       -> ('a, 'b) hierarchical_program -> 'c list

 end;

 structure Code_Namespace : CODE_NAMESPACE =

 struct

 (** building module name hierarchy **)

 val dest_name =

   apfst Long_Name.implode o split_last o fst o split_last o Long_Name.explode;

 fun build_module_namespace { module_alias, module_prefix, reserved } program =

   let

     fun alias_fragments name = case module_alias name

      of SOME name' => Long_Name.explode name'

       | NONE => map (fn name => fst (Name.variant name reserved)) (Long_Name.explode name);

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

   in

     fold (fn name => Symtab.update (name, Long_Name.explode module_prefix @ alias_fragments name))

       module_names Symtab.empty

   end;

 (** flat program structure **)

 type flat_program = ((string * Code_Thingol.stmt option) Graph.T * (string * string list) list) Graph.T;

 fun flat_program labelled_name { module_alias, module_prefix, reserved,

       empty_nsp, namify_stmt, modify_stmt } program =

   let

     (* building module name hierarchy *)

     val fragments_tab = build_module_namespace { module_alias = module_alias,

       module_prefix = module_prefix, reserved = reserved } program;

     val dest_name = dest_name

       #>> (Long_Name.implode o the o Symtab.lookup fragments_tab);

     (* distribute statements over hierarchy *)

     fun add_stmt name stmt =

       let

         val (module_name, base) = dest_name name;

       in

         Graph.default_node (module_name, (Graph.empty, []))

         #> (Graph.map_node module_name o apfst) (Graph.new_node (name, (base, stmt)))

       end;

     fun add_dependency name name' =

       let

         val (module_name, _) = dest_name name;

         val (module_name', _) = dest_name name';

       in if module_name = module_name'

         then (Graph.map_node module_name o apfst) (Graph.add_edge (name, name'))

         else (Graph.map_node module_name o apsnd) (AList.map_default (op =) (module_name', []) (insert (op =) name'))

       end;

     val proto_program = Graph.empty

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

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

           Graph.Keys.fold (add_dependency name) names) program;

     (* name declarations and statement modifications *)

     fun declare name (base, stmt) (gr, nsp) = 

       let

         val (base', nsp') = namify_stmt stmt base nsp;

         val gr' = (Graph.map_node name o apfst) (K base') gr;

       in (gr', nsp') end;

     fun declarations gr = (gr, empty_nsp)

       |> fold (fn name => declare name (Graph.get_node gr name)) (Graph.keys gr) 

       |> fst

       |> (Graph.map o K o apsnd) modify_stmt;

     val flat_program = proto_program

       |> (Graph.map o K o apfst) declarations;

     (* qualified and unqualified imports, deresolving *)

     fun base_deresolver name = fst (Graph.get_node

       (fst (Graph.get_node flat_program (fst (dest_name name)))) name);

     fun classify_names gr imports =

       let

         val import_tab = maps

           (fn (module_name, names) => map (rpair module_name) names) imports;

         val imported_names = map fst import_tab;

         val here_names = Graph.keys gr;

       in

         Symtab.empty

         |> fold (fn name => Symtab.update (name, base_deresolver name)) here_names

         |> fold (fn name => Symtab.update (name,

             Long_Name.append (the (AList.lookup (op =) import_tab name))

               (base_deresolver name))) imported_names

       end;

     val deresolver_tab = Symtab.make (AList.make

       (uncurry classify_names o Graph.get_node flat_program)

         (Graph.keys flat_program));

     fun deresolver "" name =

           Long_Name.append (fst (dest_name name)) (base_deresolver name)

       | deresolver module_name name =

           the (Symtab.lookup (the (Symtab.lookup deresolver_tab module_name)) name)

           handle Option => error ("Unknown statement name: " ^ labelled_name name);

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

 (** hierarchical program structure **)

 datatype ('a, 'b) node =

     Dummy

   | Stmt of 'a

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

 type ('a, 'b) hierarchical_program = (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 *)

     val fragments_tab = build_module_namespace { module_alias = module_alias,

       module_prefix = "", reserved = reserved } program;

     val dest_name = 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, _) = dest_name name;

         val (name_fragments', _) = 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))) =>

           Graph.Keys.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;

         fun zip_fillup xs ys = xs ~~ ys @ replicate (length xs - length ys) NONE;

         fun select_names names = case filter (member (op =) stmt_names) names

          of [] => NONE

           | xs => SOME xs;

         val modify_stmts' = AList.make (snd o Graph.get_node nodes)

           #> split_list

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

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

         val stmtss' = (maps modify_stmts' o map_filter select_names o 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;

 fun print_hierarchical { print_module, print_stmt, lift_markup } =

   let

     fun print_node _ (_, Dummy) =

           NONE

       | print_node prefix_fragments (name, Stmt stmt) =

           SOME (lift_markup (Code_Printer.markup_stmt name)

             (print_stmt prefix_fragments (name, stmt)))

       | print_node prefix_fragments (name_fragment, Module (data, nodes)) =

           let

             val prefix_fragments' = prefix_fragments @ [name_fragment]

           in

             Option.map (print_module prefix_fragments'

               name_fragment data) (print_nodes prefix_fragments' nodes)

           end

     and print_nodes prefix_fragments nodes =

       let

         val xs = (map_filter (fn name => print_node prefix_fragments

           (name, snd (Graph.get_node nodes name))) o rev o flat o Graph.strong_conn) nodes

       in if null xs then NONE else SOME xs end;

   in these o print_nodes [] end;

 end;