(*  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;