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Require Export algebra.auth algebra.functor.
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Require Export program_logic.invariants program_logic.ghost_ownership.
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Import uPred.
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Section auth.
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  Context {A : cmraT} `{Empty A, !CMRAIdentity A} `{! a : A, Timeless a}.
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  Context {Λ : language} {Σ : iFunctorG} (AuthI : gid) `{!InG Λ Σ AuthI (authRA A)}.
  Context (N : namespace) (φ : A  iPropG Λ Σ).
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  Implicit Types P Q R : iPropG Λ Σ.
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  Implicit Types a b : A.
  Implicit Types γ : gname.

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  (* Adding this locally only, since it overlaps with Auth_timelss in algebra/auth.v.
     TODO: Would moving this to auth.v and making it global break things? *)
  Local Instance AuthA_timeless (x : auth A) : Timeless x.
  Proof.
    (* FIXME: "destruct x; auto with typeclass_instances" should find this through Auth, right? *)
    destruct x. apply Auth_timeless; apply _.
  Qed.

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  (* TODO: Need this to be proven somewhere. *)
  (* FIXME ✓ binds too strong, I need parenthesis here. *)
  Hypothesis auth_valid :
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    forall a b, ( (Auth (Excl a) b) : iPropG Λ Σ)  ( b', a  b  b').
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  Definition auth_inv (γ : gname) : iPropG Λ Σ :=
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    ( a, own AuthI γ ( a)  φ a)%I.
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  Definition auth_own (γ : gname) (a : A) : iPropG Λ Σ := own AuthI γ ( a).
  Definition auth_ctx (γ : gname) : iPropG Λ Σ := inv N (auth_inv γ).
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  Lemma auth_alloc a :
    a  φ a  pvs N N ( γ, auth_ctx γ  auth_own γ a).
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  Proof.
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    intros Ha. rewrite -(right_id True%I ()%I (φ _)).
    rewrite (own_alloc AuthI (Auth (Excl a) a) N) //; [].
    rewrite pvs_frame_l. apply pvs_strip_pvs.
    rewrite sep_exist_l. apply exist_elim=>γ. rewrite -(exist_intro γ).
    transitivity (auth_inv γ  auth_own γ a)%I.
    { rewrite /auth_inv -later_intro -(exist_intro a).
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      rewrite [(_  φ _)%I]commutative -associative. apply sep_mono; first done.
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      rewrite /auth_own -own_op auth_both_op. done. }
    rewrite (inv_alloc N) /auth_ctx pvs_frame_r. apply pvs_mono.
    by rewrite always_and_sep_l'.
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  Qed.

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  Context {Hφ :  n, Proper (dist n ==> dist n) φ}.

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  Lemma auth_opened E a γ :
    (auth_inv γ  auth_own γ a)  pvs E E ( a', ▷φ (a  a')  own AuthI γ ( (a  a')   a)).
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  Proof.
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    rewrite /auth_inv. rewrite later_exist sep_exist_r. apply exist_elim=>b.
    rewrite later_sep [(own _ _ _)%I]pvs_timeless !pvs_frame_r. apply pvs_mono.
    rewrite /auth_own [(_  ▷φ _)%I]commutative -associative -own_op.
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    rewrite own_valid_r auth_valid !sep_exist_l /=. apply exist_elim=>a'.
    rewrite [  _]left_id -(exist_intro a').
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    apply (eq_rewrite b (a  a')
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              (λ x, ▷φ x  own AuthI γ ( x   a))%I); first by solve_ne.
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    { by rewrite !sep_elim_r. }
    apply sep_mono; first done.
    by rewrite sep_elim_l.
  Qed.
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  Lemma auth_closing E `{!LocalUpdate Lv L} a a' γ :
    Lv a   (L a  a') 
    (▷φ (L a  a')  own AuthI γ ( (a  a')   a))
     pvs E E (auth_inv γ  auth_own γ (L a)).
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  Proof.
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    intros HL Hv. rewrite /auth_inv /auth_own -(exist_intro (L a  a')).
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    rewrite later_sep [(_  ▷φ _)%I]commutative -associative.
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    rewrite -pvs_frame_l. apply sep_mono; first done.
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    rewrite -later_intro -own_op.
    by apply own_update, (auth_local_update_l L).
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  Qed.

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  (* Notice how the user has to prove that `b⋅a'` is valid at all
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     step-indices. However, since A is timeless, that should not be
     a restriction.  *)
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  Lemma auth_fsa {X : Type} {FSA} (FSAs : FrameShiftAssertion (A:=X) FSA)
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        `{!LocalUpdate Lv L} E P (Q : X  iPropG Λ Σ) γ a :
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    nclose N  E 
    (auth_ctx γ  auth_own γ a  ( a', ▷φ (a  a') -
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        FSA (E  nclose N) (λ x, (Lv a  (L aa'))  ▷φ (L a  a')  (auth_own γ (L a) - Q x))))
       FSA E Q.
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  Proof.
    rewrite /auth_ctx=>HN.
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    rewrite -inv_fsa; last eassumption.
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    apply sep_mono; first done. apply wand_intro_l.
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    rewrite associative auth_opened !pvs_frame_r !sep_exist_r.
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    apply fsa_strip_pvs; first done. apply exist_elim=>a'.
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    rewrite (forall_elim a'). rewrite [(_  _)%I]commutative.
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    rewrite -[((_  _)  _)%I]associative wand_elim_r fsa_frame_l.
    apply fsa_mono_pvs; first done. intros x. rewrite commutative -!associative.
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    apply const_elim_sep_l=>-[HL Hv].
    rewrite associative [(_  (_ - _))%I]commutative -associative.
    rewrite auth_closing //; []. erewrite pvs_frame_l. apply pvs_mono.
    by rewrite associative [(_  _)%I]commutative -associative wand_elim_l.
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  Qed.
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End auth.