From QuickChick Require Import QuickChick Generators.
Require Import Lia.

Set Warnings "-notation-overridden".
From mathcomp Require Import ssreflect ssrnat ssrbool eqtype.

From QuickChick.RedBlack Require Import redblack.

Require Import List String.
Import ListNotations.

Open Scope string.

Open Scope Checker_scope.

(* Red-Black Tree invariant: executable definition *)

Fixpoint black_height_bool (t: tree) : option nat :=
  match t with
    | Leaf => Some 0
    | Node c tl _ tr =>
      let h1 := black_height_bool tl in
      let h2 := black_height_bool tr in
      match h1, h2 with
        | Some n1, Some n2 =>
          if n1 == n2 then
            match c with
              | Black => Some (S n1)
              | Red => Some n1
            end
          else None
        | _, _ => None
      end
  end.

Definition is_black_balanced (t : tree) : bool :=
  isSome (black_height_bool t).

Fixpoint has_no_red_red (c : color) (t : tree) : bool :=
  match t with
    | Leaf => true
    | Node Red t1 _ t2 =>
      match c with
        | Red => false
        | Black => has_no_red_red Red t1 && has_no_red_red Red t2
      end
    | Node Black t1 _ t2 =>
      has_no_red_red Black t1 && has_no_red_red Black t2
  end.

(* begin is_redblack_bool *)
Definition is_redblack_bool (t : tree) : bool :=
  is_black_balanced t && has_no_red_red Red t.
(* end is_redblack_bool *)

Definition showColor (c : color) :=
  match c with
    | Red => "Red"
    | Black => "Black"
  end.

Fixpoint tree_to_string (t : tree) :=
  match t with
    | Leaf => "Leaf"
    | Node c l x r => "Node " ++ showColor c ++ " "
                            ++ "(" ++ tree_to_string l ++ ") "
                            ++ show x ++ " "
                            ++ "(" ++ tree_to_string r ++ ")"
  end.

#[global]
Instance showTree {A : Type} `{_ : Show A} : Show tree :=
  {|
    show t := "" (* CH: tree_to_string t causes a 9x increase in runtime *)
  |}.

(* begin insert_preserves_redblack_checker *)
Definition insert_preserves_redblack_checker (genTree : G tree) : Checker :=
  forAll arbitrary (fun n => forAll genTree (fun t =>
    is_redblack_bool t ==> is_redblack_bool (insert n t))).
(* end insert_preserves_redblack_checker *)

Import QcDefaultNotation. Open Scope qc_scope.

(* begin genAnyTree *)
Definition genColor := elems [Red; Black].
Fixpoint genAnyTree_depth (d : nat) : G tree :=
  match d with 
    | 0 => returnGen Leaf
    | S d' => freq [(1, returnGen Leaf);
                    (9, liftGen4 Node genColor (genAnyTree_depth d')
                                     arbitrary (genAnyTree_depth d'))]
  end.
Definition genAnyTree : G tree := sized genAnyTree_depth.
(* end genAnyTree *)

Extract Constant defSize => "10".

Definition test_naive :=
  insert_preserves_redblack_checker genAnyTree.
(* begin QC_naive *)
(*! QuickChick test_naive. *)
(* end QC_naive *)

(* gathering some size statistics *)
Fixpoint tree_size (t : tree) : nat :=
  match t with
    | Leaf => 1
    | Node c tl _ tr => 1 + (tree_size tl) + (tree_size tr)
  end.

Definition insert_preserves_redblack_checker_size (genTree : G tree) : Checker :=
  forAll arbitrary (fun n => forAll genTree (fun t =>
    collect (append "size " (show (tree_size t)))
    (is_redblack_bool t ==> is_redblack_bool (insert n t)))).

(*
Extract Constant Test.defNumTests => "100000".
QuickChick (insert_preserves_redblack_checker_size genAnyTree).
*)

Module DoNotation.
Import ssrfun.
Notation "'do!' X <- A ; B" :=
  (bindGen A (fun X => B))
  (at level 200, X ident, A at level 100, B at level 200).
End DoNotation.
Import DoNotation.

Require Import Relations Wellfounded Lexicographic_Product.

Definition ltColor (c1 c2: color) : Prop :=
  match c1, c2 with
    | Red, Black => True
    | _, _ => False
  end.

Lemma well_foulded_ltColor : well_founded ltColor.
Proof.
  unfold well_founded.
  intros c; destruct c;
  repeat (constructor; intros c ?; destruct c; try now (exfalso; auto)).
Qed.

Definition sigT_of_prod {A B : Type} (p : A * B) : {_ : A & B} :=
  let (a, b) := p in existT (fun _ : A => B) a b.

Definition prod_of_sigT {A B : Type} (p : {_ : A & B}) : A * B :=
  let (a, b) := p in (a, b).


Definition wf_hc (c1 c2 : (nat * color)) : Prop :=
  lexprod nat (fun _ => color) lt (fun _ => ltColor) (sigT_of_prod c1) (sigT_of_prod c2).

Lemma well_founded_hc : well_founded wf_hc.
Proof.
  unfold wf_hc. apply wf_inverse_image.
  apply wf_lexprod. now apply Wf_nat.lt_wf. intros _; now apply well_foulded_ltColor.
Qed.

#if COQ_VERSION >= (8, 21, 0)
From Stdlib.Program Require Import Wf WfExtensionality. Import WfExtensionality.
#else
From Coq.Program Require Import Wf. Import WfExtensionality.
#endif
Require Import FunctionalExtensionality.

(* begin genRBTree_height *)
Program Fixpoint genRBTree_height (hc : nat*color) {wf wf_hc hc} : G tree :=
  match hc with
  | (0, Red) => returnGen Leaf
  | (0, Black) => oneOf [returnGen Leaf;
                    (do! n <- arbitrary; returnGen (Node Red Leaf n Leaf))]
  | (S h, Red) => liftGen4 Node (returnGen Black) (genRBTree_height (h, Black))
                                        arbitrary (genRBTree_height (h, Black))
  | (S h, Black) => do! c' <- genColor;
                    let h' := match c' with Red => S h | Black => h end in
                    liftGen4 Node (returnGen c') (genRBTree_height (h', c'))
                                       arbitrary (genRBTree_height (h', c')) end.
(* end genRBTree_height *)
Next Obligation.
  unfold wf_hc; simpl; left; lia.
Qed.
Next Obligation.
  unfold wf_hc; simpl; left; lia.
Qed.
Next Obligation.
  unfold wf_hc; simpl; destruct c'; [right; apply I | left; lia].
Qed.
Next Obligation.
  unfold wf_hc; simpl; destruct c'; [right; apply I | left; lia].
Qed.
Next Obligation.
  abstract (apply well_founded_hc).
Defined.

Lemma genRBTree_height_eq (hc : nat*color) :
  genRBTree_height hc =
  match hc with
  | (0, Red) => returnGen Leaf
  | (0, Black) => oneOf [returnGen Leaf;
                    (do! n <- arbitrary; returnGen (Node Red Leaf n Leaf))]
  | (S h, Red) => liftGen4 Node (returnGen Black) (genRBTree_height (h, Black))
                                        arbitrary (genRBTree_height (h, Black))
  | (S h, Black) => do! c' <- genColor;
                    let h' := match c' with Red => S h | Black => h end in
                    liftGen4 Node (returnGen c') (genRBTree_height (h', c'))
                                       arbitrary (genRBTree_height (h', c')) end.
Proof.
  unfold_sub genRBTree_height (genRBTree_height hc).
  f_equal. destruct hc as [[|h] [|]]; try reflexivity.
  f_equal. apply functional_extensionality => [[|]]; reflexivity.
Qed.

(* Hope that this is enough for preventing unfolding genRBTree_height *)
Global Opaque genRBTree_height.


(* begin genRBTree *)
Definition genRBTree := bindGen arbitrary (fun h => genRBTree_height (h, Red)).
(* end genRBTree *)

Definition showDiscards (r : Result) :=
  match r with
  | Success ns nd _ _ => "Success: number of successes " ++ show (ns-1) ++ newline ++
                         "         number of discards "  ++ show nd ++ newline
  | _ => show r
  end.

Definition testInsert :=
  showDiscards (quickCheck (insert_preserves_redblack_checker genRBTree)).

Extract Constant defSize => "10".
Definition test_smart :=
  (insert_preserves_redblack_checker genRBTree). 
(* begin QC_good *)
(*! QuickChick test_smart. *)
(* end QC_good *)

(* gathering some size statistics
Extract Constant Test.defNumTests => "100000".
QuickChick (insert_preserves_redblack_checker_size genRBTree).
*)
