(*  Title:      HOL/Tools/Quickcheck/narrowing_generators.ML

    Author:     Lukas Bulwahn, TU Muenchen

Narrowing-based counterexample generation 

*)

signature NARROWING_GENERATORS =

sig

  val compile_generator_expr:

    Proof.context -> term -> int -> term list option * Quickcheck.report option

  val put_counterexample: (unit -> term list option) -> Proof.context -> Proof.context

  val setup: theory -> theory

end;

structure Narrowing_Generators : NARROWING_GENERATORS =

struct

val target = "Haskell"

(* invocation of Haskell interpreter *)

val narrowing_engine = File.read (Path.explode "~~/src/HOL/Tools/Quickcheck/Narrowing_Engine.hs")

fun exec verbose code =

  ML_Context.exec (fn () => Secure.use_text ML_Env.local_context (0, "generated code") verbose code)

fun value ctxt (get, put, put_ml) (code, value) =

  let

    val tmp_prefix = "Quickcheck_Narrowing"

    fun run in_path = 

      let

        val code_file = Path.append in_path (Path.basic "Code.hs")

        val narrowing_engine_file = Path.append in_path (Path.basic "Narrowing_Engine.hs")

        val main_file = Path.append in_path (Path.basic "Main.hs")

        val main = "module Main where {\n\n" ^

          "import Narrowing_Engine;\n" ^

          "import Code;\n\n" ^

          "main = Narrowing_Engine.smallCheck 7 (Code.value ())\n\n" ^

          "}\n"

        val code' = prefix "module Code where {\n\ndata Typerep = Typerep String [Typerep];\n"

          (unprefix "module Code where {" code)

        val _ = File.write code_file code'

        val _ = File.write narrowing_engine_file narrowing_engine

        val _ = File.write main_file main

        val executable = Path.implode (Path.append in_path (Path.basic "isa_lsc"))

        val cmd = getenv "EXEC_GHC" ^ " -fglasgow-exts " ^ 

          (space_implode " " (map Path.implode [code_file, narrowing_engine_file, main_file])) ^

          " -o " ^ executable ^ " && " ^ executable

      in

        bash_output cmd

      end

    val result = Isabelle_System.with_tmp_dir tmp_prefix run

    val output_value = the_default "NONE"

      (try (snd o split_last o filter_out (fn s => s = "") o split_lines o fst) result)

    val ml_code = "\nval _ = Context.set_thread_data (SOME (Context.map_proof (" ^ put_ml

      ^ " (fn () => " ^ output_value ^ ")) (ML_Context.the_generic_context ())))";

    val ctxt' = ctxt

      |> put (fn () => error ("Bad evaluation for " ^ quote put_ml))

      |> Context.proof_map (exec false ml_code);

  in get ctxt' () end;

fun evaluation cookie thy evaluator vs_t args =

  let

    val ctxt = ProofContext.init_global thy;

    val (program_code, value_name) = evaluator vs_t;

    val value_code = space_implode " "

      (value_name :: "()" :: map (enclose "(" ")") args);

  in Exn.interruptible_capture (value ctxt cookie) (program_code, value_code) end;

fun dynamic_value_strict cookie thy postproc t args =

  let

    fun evaluator naming program ((_, vs_ty), t) deps =

      evaluation cookie thy (Code_Target.evaluator thy target naming program deps) (vs_ty, t) args;

  in Exn.release (Code_Thingol.dynamic_value thy (Exn.map_result o postproc) evaluator t) end;

(* counterexample generator *)

structure Counterexample = Proof_Data

(

  type T = unit -> term list option

  fun init _ () = error "Counterexample"

)

val put_counterexample =  Counterexample.put

fun compile_generator_expr ctxt t size =

  let

    val thy = ProofContext.theory_of ctxt

    fun ensure_testable t =

      Const (@{const_name Quickcheck_Narrowing.ensure_testable}, fastype_of t --> fastype_of t) $ t

    val t = dynamic_value_strict

      (Counterexample.get, Counterexample.put, "Narrowing_Generators.put_counterexample")

      thy (Option.map o map) (ensure_testable t) []

  in

    (t, NONE)

  end;

val setup =

  Context.theory_map

    (Quickcheck.add_generator ("narrowing", compile_generator_expr))

end;