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Require Export algebra.cmra.
Require Import prelude.sets algebra.dra.
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Local Arguments valid _ _ !_ /.
Local Arguments op _ _ !_ !_ /.
Local Arguments unit _ _ !_ /.

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Inductive sts {A B} (R : relation A) (tok : A  set B) :=
  | auth : A  set B  sts R tok
  | frag : set A  set B  sts R tok.
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Arguments auth {_ _ _ _} _ _.
Arguments frag {_ _ _ _} _ _.
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Module sts.
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Section sts_core.
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Context {A B : Type} (R : relation A) (tok : A  set B).
Infix "≼" := dra_included.
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Inductive sts_equiv : Equiv (sts R tok) :=
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  | auth_equiv s T1 T2 : T1  T2  auth s T1  auth s T2
  | frag_equiv S1 S2 T1 T2 : T1  T2  S1  S2  frag S1 T1  frag S2 T2.
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Global Existing Instance sts_equiv.
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Inductive step : relation (A * set B) :=
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  | Step s1 s2 T1 T2 :
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     R s1 s2  tok s1  T1    tok s2  T2    tok s1  T1  tok s2  T2 
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     step (s1,T1) (s2,T2).
Hint Resolve Step.
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Inductive frame_step (T : set B) (s1 s2 : A) : Prop :=
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  | Frame_step T1 T2 :
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     T1  (tok s1  T)    step (s1,T1) (s2,T2)  frame_step T s1 s2.
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Hint Resolve Frame_step.
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Record closed (T : set B) (S : set A) : Prop := Closed {
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  closed_ne : S  ;
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  closed_disjoint s : s  S  tok s  T  ;
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  closed_step s1 s2 : s1  S  frame_step T s1 s2  s2  S
}.
Lemma closed_steps S T s1 s2 :
  closed T S  s1  S  rtc (frame_step T) s1 s2  s2  S.
Proof. induction 3; eauto using closed_step. Qed.
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Global Instance sts_valid : Valid (sts R tok) := λ x,
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  match x with auth s T => tok s  T   | frag S' T => closed T S' end.
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Definition up (T : set B) (s : A) : set A := mkSet (rtc (frame_step T) s).
Definition up_set (T : set B) (S : set A) : set A := S = up T.
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Global Instance sts_unit : Unit (sts R tok) := λ x,
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  match x with
  | frag S' _ => frag (up_set  S')  | auth s _ => frag (up  s) 
  end.
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Inductive sts_disjoint : Disjoint (sts R tok) :=
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  | frag_frag_disjoint S1 S2 T1 T2 :
     S1  S2    T1  T2    frag S1 T1  frag S2 T2
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  | auth_frag_disjoint s S T1 T2 : s  S  T1  T2    auth s T1  frag S T2
  | frag_auth_disjoint s S T1 T2 : s  S  T1  T2    frag S T1  auth s T2.
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Global Existing Instance sts_disjoint.
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Global Instance sts_op : Op (sts R tok) := λ x1 x2,
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  match x1, x2 with
  | frag S1 T1, frag S2 T2 => frag (S1  S2) (T1  T2)
  | auth s T1, frag _ T2 => auth s (T1  T2)
  | frag _ T1, auth s T2 => auth s (T1  T2)
  | auth s T1, auth _ T2 => auth s (T1  T2) (* never happens *)
  end.
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Global Instance sts_minus : Minus (sts R tok) := λ x1 x2,
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  match x1, x2 with
  | frag S1 T1, frag S2 T2 => frag (up_set (T1  T2) S1) (T1  T2)
  | auth s T1, frag _ T2 => auth s (T1  T2)
  | frag _ T2, auth s T1 => auth s (T1  T2) (* never happens *)
  | auth s T1, auth _ T2 => frag (up (T1  T2) s) (T1  T2)
  end.

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Hint Extern 10 (equiv (A:=set _) _ _) => solve_elem_of : sts.
Hint Extern 10 (¬(equiv (A:=set _) _ _)) => solve_elem_of : sts.
Hint Extern 10 (_  _) => solve_elem_of : sts.
Hint Extern 10 (_  _) => solve_elem_of : sts.
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Instance: Equivalence (() : relation (sts R tok)).
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Proof.
  split.
  * by intros []; constructor.
  * by destruct 1; constructor.
  * destruct 1; inversion_clear 1; constructor; etransitivity; eauto.
Qed.
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Instance framestep_proper : Proper (() ==> (=) ==> (=) ==> impl) frame_step.
Proof. intros ?? HT ?? <- ?? <-; destruct 1; econstructor; eauto with sts. Qed.
Instance closed_proper' : Proper (() ==> () ==> impl) closed.
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Proof.
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  intros ?? HT ?? HS; destruct 1;
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    constructor; intros until 0; rewrite -?HS -?HT; eauto.
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Qed.
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Instance closed_proper : Proper (() ==> () ==> iff) closed.
Proof. by split; apply closed_proper'. Qed.
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Lemma closed_op T1 T2 S1 S2 :
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  closed T1 S1  closed T2 S2 
  T1  T2    S1  S2    closed (T1  T2) (S1  S2).
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Proof.
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  intros [_ ? Hstep1] [_ ? Hstep2] ?; split; [done|solve_elem_of|].
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  intros s3 s4; rewrite !elem_of_intersection; intros [??] [T3 T4 ?]; split.
  * apply Hstep1 with s3, Frame_step with T3 T4; auto with sts.
  * apply Hstep2 with s3, Frame_step with T3 T4; auto with sts.
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Qed.
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Instance up_preserving : Proper (flip () ==> (=) ==> ()) up.
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Proof.
  intros T T' HT s ? <-; apply elem_of_subseteq.
  induction 1 as [|s1 s2 s3 [T1 T2]]; [constructor|].
  eapply rtc_l; [eapply Frame_step with T1 T2|]; eauto with sts.
Qed.
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Instance up_proper : Proper (() ==> (=) ==> ()) up.
Proof. by intros ?? [??] ???; split; apply up_preserving. Qed.
Instance up_set_proper : Proper (() ==> () ==> ()) up_set.
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Proof. by intros T1 T2 HT S1 S2 HS; rewrite /up_set HS HT. Qed.
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Lemma elem_of_up s T : s  up T s.
Proof. constructor. Qed.
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Lemma subseteq_up_set S T : S  up_set T S.
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Proof. intros s ?; apply elem_of_bind; eauto using elem_of_up. Qed.
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Lemma closed_up_set S T :
  ( s, s  S  tok s  T  )  S    closed T (up_set T S).
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Proof.
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  intros HS Hne; unfold up_set; split.
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  * assert ( s, s  up T s) by eauto using elem_of_up. solve_elem_of.
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  * intros s; rewrite !elem_of_bind; intros (s'&Hstep&Hs').
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    specialize (HS s' Hs'); clear Hs' Hne S.
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    induction Hstep as [s|s1 s2 s3 [T1 T2 ? Hstep] ? IH]; auto.
    inversion_clear Hstep; apply IH; clear IH; auto with sts.
  * intros s1 s2; rewrite !elem_of_bind; intros (s&?&?) ?; exists s.
    split; [eapply rtc_r|]; eauto.
Qed.
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Lemma closed_up_set_empty S : S    closed  (up_set  S).
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Proof. eauto using closed_up_set with sts. Qed.
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Lemma closed_up s T : tok s  T    closed T (up T s).
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Proof.
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  intros; rewrite -(collection_bind_singleton (up T) s).
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  apply closed_up_set; solve_elem_of.
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Qed.
Lemma closed_up_empty s : closed  (up  s).
Proof. eauto using closed_up with sts. Qed.
Lemma up_closed S T : closed T S  up_set T S  S.
Proof.
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  intros; split; auto using subseteq_up_set; intros s.
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  unfold up_set; rewrite elem_of_bind; intros (s'&Hstep&?).
  induction Hstep; eauto using closed_step.
Qed.
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Global Instance sts_dra : DRA (sts R tok).
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Proof.
  split.
  * apply _.
  * by do 2 destruct 1; constructor; setoid_subst.
  * by destruct 1; constructor; setoid_subst.
  * by intros ? [|]; destruct 1; inversion_clear 1; constructor; setoid_subst.
  * by do 2 destruct 1; constructor; setoid_subst.
  * assert ( T T' S s,
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      closed T S  s  S  tok s  T'    tok s  (T  T')  ).
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    { intros S T T' s [??]; solve_elem_of. }
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    destruct 3; simpl in *; auto using closed_op with sts.
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  * intros []; simpl; eauto using closed_up, closed_up_set, closed_ne with sts.
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  * intros ???? (z&Hy&?&Hxz); destruct Hxz; inversion Hy;clear Hy; setoid_subst;
      rewrite ?disjoint_union_difference; auto using closed_up with sts.
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    eapply closed_up_set; eauto 2 using closed_disjoint with sts.
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  * intros [] [] []; constructor; rewrite ?assoc; auto with sts.
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  * destruct 4; inversion_clear 1; constructor; auto with sts.
  * destruct 4; inversion_clear 1; constructor; auto with sts.
  * destruct 1; constructor; auto with sts.
  * destruct 3; constructor; auto with sts.
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  * intros [|S T]; constructor; auto using elem_of_up with sts.
    assert (S  up_set  S  S  ) by eauto using subseteq_up_set, closed_ne.
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    solve_elem_of.
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  * intros [|S T]; constructor; auto with sts.
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    assert (S  up_set  S); auto using subseteq_up_set with sts.
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  * intros [s T|S T]; constructor; auto with sts.
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    + rewrite (up_closed (up _ _)); auto using closed_up with sts.
    + rewrite (up_closed (up_set _ _));
        eauto using closed_up_set, closed_ne with sts.
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  * intros x y ?? (z&Hy&?&Hxz); exists (unit (x  y)); split_ands.
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    + destruct Hxz;inversion_clear Hy;constructor;unfold up_set; solve_elem_of.
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    + destruct Hxz; inversion_clear Hy; simpl;
        auto using closed_up_set_empty, closed_up_empty with sts.
    + destruct Hxz; inversion_clear Hy; constructor;
        repeat match goal with
        | |- context [ up_set ?T ?S ] =>
           unless (S  up_set T S) by done; pose proof (subseteq_up_set S T)
        | |- context [ up ?T ?s ] =>
           unless (s  up T s) by done; pose proof (elem_of_up s T)
        end; auto with sts.
  * intros x y ?? (z&Hy&_&Hxz); destruct Hxz; inversion_clear Hy; constructor;
      repeat match goal with
      | |- context [ up_set ?T ?S ] =>
         unless (S  up_set T S) by done; pose proof (subseteq_up_set S T)
      | |- context [ up ?T ?s ] =>
           unless (s  up T s) by done; pose proof (elem_of_up s T)
      end; auto with sts.
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  * intros x y ?? (z&Hy&?&Hxz); destruct Hxz as [S1 S2 T1 T2| |];
      inversion Hy; clear Hy; constructor; setoid_subst;
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      rewrite ?disjoint_union_difference; auto.
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    split; [|apply intersection_greatest; auto using subseteq_up_set with sts].
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    apply intersection_greatest; [auto with sts|].
    intros s2; rewrite elem_of_intersection.
    unfold up_set; rewrite elem_of_bind; intros (?&s1&?&?&?).
    apply closed_steps with T2 s1; auto with sts.
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Qed.
Lemma step_closed s1 s2 T1 T2 S Tf :
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  step (s1,T1) (s2,T2)  closed Tf S  s1  S  T1  Tf   
  s2  S  T2  Tf    tok s2  T2  .
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Proof.
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  inversion_clear 1 as [???? HR Hs1 Hs2]; intros [?? Hstep]??; split_ands; auto.
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  * eapply Hstep with s1, Frame_step with T1 T2; auto with sts.
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  * solve_elem_of -Hstep Hs1 Hs2.
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Qed.
End sts_core.
End sts.

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Section stsRA.
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Context {A B : Type} (R : relation A) (tok : A  set B).
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Canonical Structure stsRA := validityRA (sts R tok).
Definition sts_auth (s : A) (T : set B) : stsRA := to_validity (auth s T).
Definition sts_frag (S : set A) (T : set B) : stsRA := to_validity (frag S T).
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Lemma sts_update s1 s2 T1 T2 :
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  sts.step R tok (s1,T1) (s2,T2)  sts_auth s1 T1 ~~> sts_auth s2 T2.
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Proof.
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  intros ?; apply validity_update; inversion 3 as [|? S ? Tf|]; subst.
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  destruct (sts.step_closed R tok s1 s2 T1 T2 S Tf) as (?&?&?); auto.
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  repeat (done || constructor).
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Qed.
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End stsRA.