(*  Title:      HOL/Tools/Predicate_Compile/code_prolog.ML

     Author:     Lukas Bulwahn, TU Muenchen

 Prototype of an code generator for logic programming languages (a.k.a. Prolog)

 *)

 signature CODE_PROLOG =

 sig

   datatype prol_term = Var of string | Cons of string | AppF of string * prol_term list;

   datatype prem = Conj of prem list | NotRel of string * prol_term list

     | Rel of string * prol_term list | Eq of prol_term * prol_term | NotEq of prol_term * prol_term;

   type clause = ((string * prol_term list) * prem);

   type logic_program = clause list;

   type constant_table = (string * string) list

   val generate : Proof.context -> string list -> (logic_program * constant_table)

   val write_program : logic_program -> string

   val run : logic_program -> string -> string list -> int option -> prol_term list list

   val trace : bool Unsynchronized.ref

 end;

 structure Code_Prolog : CODE_PROLOG =

 struct

 (* diagnostic tracing *)

 val trace = Unsynchronized.ref false

 fun tracing s = if !trace then Output.tracing s else () 

 (* general string functions *)

 val first_upper = implode o nth_map 0 Symbol.to_ascii_upper o explode;

 val first_lower = implode o nth_map 0 Symbol.to_ascii_lower o explode;

 (* internal program representation *)

 datatype prol_term = Var of string | Cons of string | AppF of string * prol_term list;

 fun string_of_prol_term (Var s) = "Var " ^ s

   | string_of_prol_term (Cons s) = "Cons " ^ s

   | string_of_prol_term (AppF (f, args)) = f ^ "(" ^ commas (map string_of_prol_term args) ^ ")" 

 datatype prem = Conj of prem list | NotRel of string * prol_term list

     | Rel of string * prol_term list | Eq of prol_term * prol_term | NotEq of prol_term * prol_term;

 fun dest_Rel (Rel (c, ts)) = (c, ts)

 type clause = ((string * prol_term list) * prem);

 type logic_program = clause list;

 (* translation from introduction rules to internal representation *)

 (** constant table **)

 type constant_table = (string * string) list

 (* assuming no clashing *)

 fun mk_constant_table consts =

   AList.make (first_lower o Long_Name.base_name) consts

 fun declare_consts consts constant_table =

   fold (fn c => AList.update (op =) (c, first_lower (Long_Name.base_name c))) consts constant_table

 fun translate_const constant_table c =

   case AList.lookup (op =) constant_table c of

     SOME c' => c'

   | NONE => error ("No such constant: " ^ c)

 fun inv_lookup _ [] _ = NONE

   | inv_lookup eq ((key, value)::xs) value' =

       if eq (value', value) then SOME key

       else inv_lookup eq xs value';

 fun restore_const constant_table c =

   case inv_lookup (op =) constant_table c of

     SOME c' => c'

   | NONE => error ("No constant corresponding to "  ^ c)

 (** translation of terms, literals, premises, and clauses **)

 fun translate_term ctxt constant_table t =

   case strip_comb t of

     (Free (v, T), []) => Var v 

   | (Const (c, _), []) => Cons (translate_const constant_table c)

   | (Const (c, _), args) =>

     AppF (translate_const constant_table c, map (translate_term ctxt constant_table) args)

   | _ => error ("illegal term for translation: " ^ Syntax.string_of_term ctxt t)

 fun translate_literal ctxt constant_table t =

   case strip_comb t of

     (Const (@{const_name "op ="}, _), [l, r]) =>

       Eq (pairself (translate_term ctxt constant_table) (l, r))

   | (Const (c, _), args) =>

       Rel (translate_const constant_table c, map (translate_term ctxt constant_table) args)

   | _ => error ("illegal literal for translation: " ^ Syntax.string_of_term ctxt t)

 fun NegRel_of (Rel lit) = NotRel lit

   | NegRel_of (Eq eq) = NotEq eq

 fun translate_prem ctxt constant_table t =  

     case try HOLogic.dest_not t of

       SOME t => NegRel_of (translate_literal ctxt constant_table t)

     | NONE => translate_literal ctxt constant_table t

 fun translate_intros ctxt gr const constant_table =

   let

     val intros = Graph.get_node gr const

     val (intros', ctxt') = Variable.import_terms true (map prop_of intros) ctxt

     val constant_table' = declare_consts (fold Term.add_const_names intros' []) constant_table

     fun translate_intro intro =

       let

         val head = HOLogic.dest_Trueprop (Logic.strip_imp_concl intro)

         val prems = map HOLogic.dest_Trueprop (Logic.strip_imp_prems intro) 

         val prems' = Conj (map (translate_prem ctxt' constant_table') prems)

         val clause = (dest_Rel (translate_literal ctxt' constant_table' head), prems')

       in clause end

   in (map translate_intro intros', constant_table') end

 fun generate ctxt const =

   let 

      fun strong_conn_of gr keys =

       Graph.strong_conn (Graph.subgraph (member (op =) (Graph.all_succs gr keys)) gr)

     val gr = Predicate_Compile_Core.intros_graph_of ctxt

     val scc = strong_conn_of gr const

     val constant_table = mk_constant_table (flat scc)

   in

     apfst flat (fold_map (translate_intros ctxt gr) (flat scc) constant_table)

   end

 (* transform logic program *)

 (** ensure groundness of terms before negation **)

 fun add_vars (Var x) vs = insert (op =) x vs

   | add_vars (Cons c) vs = vs

   | add_vars (AppF (f, args)) vs = fold add_vars args vs

 fun string_of_typ (Type (s, Ts)) = Long_Name.base_name s

 fun mk_groundness_prems ts =

   let

     val vars = fold add_vars ts []

     fun mk_ground v =

       Rel ("ground", [Var v])

   in

     map mk_ground vars

   end

 fun ensure_groundness_prem (NotRel (c, ts)) = Conj (mk_groundness_prems ts @ [NotRel (c, ts)]) 

   | ensure_groundness_prem (NotEq (l, r)) = Conj (mk_groundness_prems [l, r] @ [NotEq (l, r)])

   | ensure_groundness_prem (Conj ps) = Conj (map ensure_groundness_prem ps)

   | ensure_groundness_prem p = p

 fun ensure_groundness_before_negation p =

   map (apsnd ensure_groundness_prem) p

 (* code printer *)

 fun write_term (Var v) = first_upper v

   | write_term (Cons c) = c

   | write_term (AppF (f, args)) = f ^ "(" ^ space_implode ", " (map write_term args) ^ ")" 

 fun write_rel (pred, args) =

   pred ^ "(" ^ space_implode ", " (map write_term args) ^ ")" 

 fun write_prem (Conj prems) = space_implode ", " (map write_prem prems)

   | write_prem (Rel p) = write_rel p  

   | write_prem (NotRel p) = "not(" ^ write_rel p ^ ")"

   | write_prem (Eq (l, r)) = write_term l ^ " = " ^ write_term r

   | write_prem (NotEq (l, r)) = write_term l ^ " \\= " ^ write_term r

 fun write_clause (head, prem) =

   write_rel head ^ (if prem = Conj [] then "." else " :- " ^ write_prem prem ^ ".")

 fun write_program p =

   cat_lines (map write_clause p) 

 (** query templates **)

 fun query_first rel vnames =

   "eval :- once("  ^ rel ^ "(" ^ space_implode ", " vnames ^ ")),\n" ^

   "writef('" ^ space_implode ";" (map (fn v => v ^ " = %w") vnames) ^

   "\\n', [" ^ space_implode ", " vnames ^ "]).\n"

 fun query_firstn n rel vnames =

   "eval :- findnsols(" ^ string_of_int n ^ ", (" ^ space_implode ", " vnames ^ "), " ^

     rel ^ "(" ^ space_implode ", " vnames ^ "), Sols), writelist(Sols).\n" ^

     "writelist([]).\n" ^

     "writelist([(" ^ space_implode ", " vnames ^ ")|T]) :- " ^

     "writef('" ^ space_implode ";" (map (fn v => v ^ " = %w") vnames) ^

     "\\n', [" ^ space_implode ", " vnames ^ "]), writelist(T).\n"

 val prelude =

   "#!/usr/bin/swipl -q -t main -f\n\n" ^

   ":- use_module(library('dialect/ciao/aggregates')).\n" ^

   ":- style_check(-singleton).\n\n" ^

   "main :- catch(eval, E, (print_message(error, E), fail)), halt.\n" ^

   "main :- halt(1).\n"

 (* parsing prolog solution *)

 val scan_atom =

   Scan.many1 (fn s => Symbol.is_ascii_lower s orelse Symbol.is_ascii_quasi s)

 val scan_var =

   Scan.many1

     (fn s => Symbol.is_ascii_upper s orelse Symbol.is_ascii_digit s orelse Symbol.is_ascii_quasi s)

 val scan_ident =

   Scan.repeat (Scan.one

     (fn s => Symbol.is_ascii_letter s orelse Symbol.is_ascii_digit s orelse Symbol.is_ascii_quasi s))

 fun dest_Char (Symbol.Char s) = s

 val string_of = concat o map (dest_Char o Symbol.decode)

 val is_atom_ident = forall Symbol.is_ascii_lower

 val is_var_ident =

   forall (fn s => Symbol.is_ascii_upper s orelse Symbol.is_ascii_digit s orelse Symbol.is_ascii_quasi s)

 fun scan_terms xs = (((scan_term --| $$ ",") ::: scan_terms)

   || (scan_term >> single)) xs

 and scan_term xs =

   ((scan_var >> (Var o string_of))

   || ((scan_atom -- ($$ "(" |-- scan_terms --| $$ ")"))

     >> (fn (f, ts) => AppF (string_of f, ts)))

   || (scan_atom >> (Cons o string_of))) xs

 val parse_term = fst o Scan.finite Symbol.stopper

     (Scan.error (!! (fn _ => raise Fail "parsing prolog output failed")) scan_term)

   o explode

 fun parse_solutions sol =

   let

     fun dest_eq s = case space_explode "=" s of

         (l :: r :: []) => parse_term (unprefix " " r)

       | _ => raise Fail "unexpected equation in prolog output"

     fun parse_solution s = map dest_eq (space_explode ";" s)

   in

     map parse_solution (fst (split_last (space_explode "\n" sol)))

   end 

 (* calling external interpreter and getting results *)

 fun run p query_rel vnames nsols =

   let

     val cmd = Path.named_root

     val query = case nsols of NONE => query_first | SOME n => query_firstn n 

     val prog = prelude ^ query query_rel vnames ^ write_program p

     val _ = tracing ("Generated prolog program:\n" ^ prog)

     val prolog_file = File.tmp_path (Path.basic "prolog_file")

     val _ = File.write prolog_file prog

     val (solution, _) = bash_output ("/usr/local/bin/swipl -f " ^ File.shell_path prolog_file)

     val _ = tracing ("Prolog returned solution(s):\n" ^ solution)

     val tss = parse_solutions solution

   in

     tss

   end

 (* values command *)

 fun restore_term ctxt constant_table (Var s, T) = Free (s, T)

   | restore_term ctxt constant_table (Cons s, T) = Const (restore_const constant_table s, T)

   | restore_term ctxt constant_table (AppF (f, args), T) =

     let

       val thy = ProofContext.theory_of ctxt

       val c = restore_const constant_table f

       val cT = Sign.the_const_type thy c

       val (argsT, resT) = strip_type cT

       val subst = Sign.typ_match thy (resT, T) Vartab.empty

       val argsT' = map (Envir.subst_type subst) argsT

     in

       list_comb (Const (c, Envir.subst_type subst cT),

         map (restore_term ctxt constant_table) (args ~~ argsT'))

     end

 fun values ctxt soln t_compr =

   let

     val split = case t_compr of (Const (@{const_name Collect}, _) $ t) => t

       | _ => error ("Not a set comprehension: " ^ Syntax.string_of_term ctxt t_compr);

     val (body, Ts, fp) = HOLogic.strip_psplits split;

     val output_names = Name.variant_list (Term.add_free_names body [])

       (map (fn i => "x" ^ string_of_int i) (1 upto length Ts))

     val output_frees = rev (map2 (curry Free) output_names Ts)

     val body = subst_bounds (output_frees, body)

     val (pred as Const (name, T), all_args) =

       case strip_comb body of

         (Const (name, T), all_args) => (Const (name, T), all_args)

       | (head, _) => error ("Not a constant: " ^ Syntax.string_of_term ctxt head)

     val vnames =

       case try (map (fst o dest_Free)) all_args of

         SOME vs => vs

       | NONE => error ("Not only free variables in " ^ commas (map (Syntax.string_of_term ctxt) all_args))

     val _ = tracing "Generating prolog program..."

     val (p, constant_table) = generate ctxt [name]

     val _ = tracing "Running prolog program..."

     val tss = run p (translate_const constant_table name) (map first_upper vnames) soln

     val _ = tracing "Restoring terms..."

     fun mk_set_comprehension t =

       let

         val frees = Term.add_frees t []

         val uu as (uuN, uuT) = singleton (Variable.variant_frees ctxt [t]) ("uu", fastype_of t)

       in HOLogic.mk_Collect (uuN, uuT, fold (fn (s, T) => fn t => HOLogic.mk_exists (s, T, t))

         frees (HOLogic.mk_conj (HOLogic.mk_eq (Free uu, t), @{term "True"}))) end

     val set_comprs = map (fn ts =>

       mk_set_comprehension (HOLogic.mk_tuple (map (restore_term ctxt constant_table) (ts ~~ Ts)))) tss

   in

     foldl1 (HOLogic.mk_binop @{const_name sup}) (set_comprs @ [Free ("...", fastype_of t_compr)])

   end

 fun values_cmd print_modes soln raw_t state =

   let

     val ctxt = Toplevel.context_of state

     val t = Syntax.read_term ctxt raw_t

     val t' = values ctxt soln t

     val ty' = Term.type_of t'

     val ctxt' = Variable.auto_fixes t' ctxt

     val p = Print_Mode.with_modes print_modes (fn () =>

       Pretty.block [Pretty.quote (Syntax.pretty_term ctxt' t'), Pretty.fbrk,

         Pretty.str "::", Pretty.brk 1, Pretty.quote (Syntax.pretty_typ ctxt' ty')]) ();

   in Pretty.writeln p end;

 (* renewing the values command for Prolog queries *)

 val opt_print_modes =

   Scan.optional (Parse.$$$ "(" |-- Parse.!!! (Scan.repeat1 Parse.xname --| Parse.$$$ ")")) [];

 val _ = Outer_Syntax.improper_command "values" "enumerate and print comprehensions" Keyword.diag

   (opt_print_modes -- Scan.optional (Parse.nat >> SOME) NONE -- Parse.term

    >> (fn ((print_modes, soln), t) => Toplevel.keep

         (values_cmd print_modes soln t)));

 end;