Library iris.algebra.lib.gmap_view

From Coq.QArith Require Import Qcanon.
From iris.algebra Require Export view gmap frac dfrac.
From iris.algebra Require Import local_updates proofmode_classes big_op.
From iris.prelude Require Import options.

CMRA for a "view of a gmap".

The authoritative element gmap_view_auth is any gmap K V. The fragments gmap_view_frag represent ownership of a single key in that map. Ownership is governed by a discardable fraction, which provides the possibiltiy to obtain persistent read-only ownership of a key.
The key frame-preserving updates are gmap_view_alloc to allocate a new key, gmap_view_update to update a key given full ownership of the corresponding fragment, and gmap_view_persist to make a key read-only by discarding any fraction of the corresponding fragment. Crucially, the latter does not require owning the authoritative element.
NOTE: The API surface for gmap_view is experimental and subject to change. We plan to add notations for authoritative elements and fragments, and hope to support arbitrary maps as fragments.

Local Definition gmap_view_fragUR (K : Type) `{Countable K} (V : cmra) : ucmra :=
  gmapUR K (prodR dfracR V).

View relation.
Section rel.
  Context (K : Type) `{Countable K} (V : cmra).
  Implicit Types (m : gmap K V) (k : K) (v : V) (n : nat).
  Implicit Types (f : gmap K (dfrac × V)).

  Local Definition gmap_view_rel_raw n m f :=
    map_Forall (λ k fv,
       v dq, m !! k = Some v ✓{n} (dq, v) (Some fv ≼{n} Some (dq, v))) f.

  Local Lemma gmap_view_rel_raw_mono n1 n2 m1 m2 f1 f2 :
    gmap_view_rel_raw n1 m1 f1
    m1 ≡{n2}≡ m2
    f2 ≼{n2} f1
    n2 n1
    gmap_view_rel_raw n2 m2 f2.
  Proof.
    intros Hrel Hm Hf Hn k [dqa va] Hk.
    destruct (lookup_includedN n2 f2 f1) as [Hf' _].
    specialize (Hf' Hf k). clear Hf. rewrite Hk in Hf'.
    destruct (Some_includedN_is_Some _ _ _ Hf') as [[q' va'] Heq]. rewrite Heq in Hf'.
    specialize (Hrel _ _ Heq) as (v & dq & Hm1 & [Hvval Hdqval] & Hvincl). simpl in ×.
    specialize (Hm k).
    edestruct (dist_Some_inv_l _ _ _ _ Hm Hm1) as (v' & Hm2 & Hv).
    eexists. dq. split; first done. split.
    { split; first done. simpl. rewrite -Hv. eapply cmra_validN_le; done. }
    rewrite -Hv. etrans; first exact Hf'.
    apply: cmra_includedN_le; done.
  Qed.

  Local Lemma gmap_view_rel_raw_valid n m f :
    gmap_view_rel_raw n m f ✓{n} f.
  Proof.
    intros Hrel k. destruct (f !! k) as [[dqa va]|] eqn:Hf; rewrite Hf; last done.
    specialize (Hrel _ _ Hf) as (v & dq & Hmval & Hvval & Hvincl). simpl in ×.
    eapply cmra_validN_includedN. 2:done. done.
  Qed.

  Local Lemma gmap_view_rel_raw_unit n :
     m, gmap_view_rel_raw n m ε.
  Proof. . apply: map_Forall_empty. Qed.

  Local Canonical Structure gmap_view_rel : view_rel (gmapO K V) (gmap_view_fragUR K V) :=
    ViewRel gmap_view_rel_raw gmap_view_rel_raw_mono
            gmap_view_rel_raw_valid gmap_view_rel_raw_unit.

  Local Lemma gmap_view_rel_exists n f :
    ( m, gmap_view_rel n m f) ✓{n} f.
  Proof.
    split.
    { intros [m Hrel]. eapply gmap_view_rel_raw_valid, Hrel. }
    intros Hf.
    cut ( m, gmap_view_rel n m f k, f !! k = None m !! k = None).
    { naive_solver. }
    induction f as [|k [dq v] f Hk' IH] using map_ind.
    { . split; [|done]. apply: map_Forall_empty. }
    move: (Hf k). rewrite lookup_insert⇒ -[/= ??].
    destruct IH as (m & Hm & Hdom).
    { intros k'. destruct (decide (k = k')) as [->|?]; [by rewrite Hk'|].
      move: (Hf k'). by rewrite lookup_insert_ne. }
     (<[k:=v]> m).
    rewrite /gmap_view_rel /= /gmap_view_rel_raw map_Forall_insert //=. split_and!.
    - v, dq. split; first by rewrite lookup_insert.
      split; first by split. done.
    - eapply map_Forall_impl; [apply Hm|]; simpl.
      intros k' [dq' ag'] (v'&?&?&?). v'.
      rewrite lookup_insert_ne; naive_solver.
    - intros k'. rewrite !lookup_insert_None. naive_solver.
  Qed.

  Local Lemma gmap_view_rel_unit n m : gmap_view_rel n m ε.
  Proof. apply: map_Forall_empty. Qed.

  Local Lemma gmap_view_rel_discrete :
    CmraDiscrete V ViewRelDiscrete gmap_view_rel.
  Proof.
    intros ? n m f Hrel k [df va] Hk.
    destruct (Hrel _ _ Hk) as (v & dq & Hm & Hvval & Hvincl).
     v, dq. split; first done.
    split; first by apply cmra_discrete_valid_iff_0.
    rewrite -cmra_discrete_included_iff_0. done.
  Qed.
End rel.

Local Existing Instance gmap_view_rel_discrete.

gmap_view is a notation to give canonical structure search the chance to infer the right instances (see auth).
Notation gmap_view K V := (view (@gmap_view_rel_raw K _ _ V)).
Definition gmap_viewO (K : Type) `{Countable K} (V : cmra) : ofe :=
  viewO (gmap_view_rel K V).
Definition gmap_viewR (K : Type) `{Countable K} (V : cmra) : cmra :=
  viewR (gmap_view_rel K V).
Definition gmap_viewUR (K : Type) `{Countable K} (V : cmra) : ucmra :=
  viewUR (gmap_view_rel K V).

Section definitions.
  Context {K : Type} `{Countable K} {V : cmra}.

  Definition gmap_view_auth (dq : dfrac) (m : gmap K V) : gmap_viewR K V :=
    V{dq} m.
  Definition gmap_view_frag (k : K) (dq : dfrac) (v : V) : gmap_viewR K V :=
    V {[k := (dq, v)]}.
End definitions.

Section lemmas.
  Context {K : Type} `{Countable K} {V : cmra}.
  Implicit Types (m : gmap K V) (k : K) (q : Qp) (dq : dfrac) (v : V).

  Global Instance : Params (@gmap_view_auth) 5 := {}.
  Global Instance gmap_view_auth_ne dq : NonExpansive (gmap_view_auth (K:=K) (V:=V) dq).
  Proof. solve_proper. Qed.
  Global Instance gmap_view_auth_proper dq : Proper ((≡) ==> (≡)) (gmap_view_auth (K:=K) (V:=V) dq).
  Proof. apply ne_proper, _. Qed.

  Global Instance : Params (@gmap_view_frag) 6 := {}.
  Global Instance gmap_view_frag_ne k oq : NonExpansive (gmap_view_frag (V:=V) k oq).
  Proof. solve_proper. Qed.
  Global Instance gmap_view_frag_proper k oq : Proper ((≡) ==> (≡)) (gmap_view_frag (V:=V) k oq).
  Proof. apply ne_proper, _. Qed.

  Local Lemma gmap_view_rel_lookup n m k dq v :
    gmap_view_rel K V n m {[k := (dq, v)]}
     v' dq', m !! k = Some v' ✓{n} (dq', v') Some (dq, v) ≼{n} Some (dq', v').
  Proof.
    split.
    - intros Hrel.
      edestruct (Hrel k) as (v' & dq' & Hlookup & Hval & Hinc).
      { rewrite lookup_singleton. done. }
      simpl in ×. eexists _, _. split_and!; done.
    - intros (v' & dq' & Hlookup & Hval & ?) j [df va].
      destruct (decide (k = j)) as [<-|Hne]; last by rewrite lookup_singleton_ne.
      rewrite lookup_singleton. intros [= <- <-]. simpl.
       v', dq'. split_and!; by rewrite ?Hv'.
  Qed.

Composition and validity
  Lemma gmap_view_auth_dfrac_op dp dq m :
    gmap_view_auth (dp dq) m
    gmap_view_auth dp m gmap_view_auth dq m.
  Proof. by rewrite /gmap_view_auth view_auth_dfrac_op. Qed.
  Global Instance gmap_view_auth_dfrac_is_op dq dq1 dq2 m :
    IsOp dq dq1 dq2 IsOp' (gmap_view_auth dq m) (gmap_view_auth dq1 m) (gmap_view_auth dq2 m).
  Proof. rewrite /gmap_view_auth. apply _. Qed.

  Lemma gmap_view_auth_dfrac_op_invN n dp m1 dq m2 :
    ✓{n} (gmap_view_auth dp m1 gmap_view_auth dq m2) m1 ≡{n}≡ m2.
  Proof. apply view_auth_dfrac_op_invN. Qed.
  Lemma gmap_view_auth_dfrac_op_inv dp m1 dq m2 :
     (gmap_view_auth dp m1 gmap_view_auth dq m2) m1 m2.
  Proof. apply view_auth_dfrac_op_inv. Qed.

  Lemma gmap_view_auth_dfrac_validN m n dq : ✓{n} gmap_view_auth dq m dq.
  Proof.
    rewrite view_auth_dfrac_validN. intuition eauto using gmap_view_rel_unit.
  Qed.
  Lemma gmap_view_auth_dfrac_valid m dq : gmap_view_auth dq m dq.
  Proof.
    rewrite view_auth_dfrac_valid. intuition eauto using gmap_view_rel_unit.
  Qed.
  Lemma gmap_view_auth_valid m : gmap_view_auth (DfracOwn 1) m.
  Proof. rewrite gmap_view_auth_dfrac_valid. done. Qed.

  Lemma gmap_view_auth_dfrac_op_validN n dq1 dq2 m1 m2 :
    ✓{n} (gmap_view_auth dq1 m1 gmap_view_auth dq2 m2) (dq1 dq2) m1 ≡{n}≡ m2.
  Proof.
    rewrite view_auth_dfrac_op_validN. intuition eauto using gmap_view_rel_unit.
  Qed.
  Lemma gmap_view_auth_dfrac_op_valid dq1 dq2 m1 m2 :
     (gmap_view_auth dq1 m1 gmap_view_auth dq2 m2) (dq1 dq2) m1 m2.
  Proof.
    rewrite view_auth_dfrac_op_valid. intuition eauto using gmap_view_rel_unit.
  Qed.

  Lemma gmap_view_auth_op_validN n m1 m2 :
    ✓{n} (gmap_view_auth (DfracOwn 1) m1 gmap_view_auth (DfracOwn 1) m2) False.
  Proof. apply view_auth_op_validN. Qed.
  Lemma gmap_view_auth_op_valid m1 m2 :
     (gmap_view_auth (DfracOwn 1) m1 gmap_view_auth (DfracOwn 1) m2) False.
  Proof. apply view_auth_op_valid. Qed.

  Lemma gmap_view_frag_validN n k dq v : ✓{n} gmap_view_frag k dq v dq ✓{n} v.
  Proof.
    rewrite view_frag_validN gmap_view_rel_exists singleton_validN pair_validN.
    naive_solver.
  Qed.
  Lemma gmap_view_frag_valid k dq v : gmap_view_frag k dq v dq v.
  Proof.
    rewrite cmra_valid_validN. setoid_rewrite gmap_view_frag_validN.
    rewrite cmra_valid_validN. naive_solver eauto using O.
  Qed.

  Lemma gmap_view_frag_op k dq1 dq2 v1 v2 :
    gmap_view_frag k (dq1 dq2) (v1 v2)
      gmap_view_frag k dq1 v1 gmap_view_frag k dq2 v2.
  Proof. rewrite -view_frag_op singleton_op -pair_op //. Qed.
  Lemma gmap_view_frag_add k q1 q2 v1 v2 :
    gmap_view_frag k (DfracOwn (q1 + q2)) (v1 v2)
      gmap_view_frag k (DfracOwn q1) v1 gmap_view_frag k (DfracOwn q2) v2.
  Proof. rewrite -gmap_view_frag_op. done. Qed.

  Lemma gmap_view_frag_op_validN n k dq1 dq2 v1 v2 :
    ✓{n} (gmap_view_frag k dq1 v1 gmap_view_frag k dq2 v2)
       (dq1 dq2) ✓{n} (v1 v2).
  Proof.
    rewrite view_frag_validN gmap_view_rel_exists singleton_op singleton_validN.
    by rewrite -pair_op pair_validN.
  Qed.
  Lemma gmap_view_frag_op_valid k dq1 dq2 v1 v2 :
     (gmap_view_frag k dq1 v1 gmap_view_frag k dq2 v2)
       (dq1 dq2) (v1 v2).
  Proof.
    rewrite view_frag_valid. setoid_rewrite gmap_view_rel_exists.
    rewrite -cmra_valid_validN singleton_op singleton_valid.
    by rewrite -pair_op pair_valid.
  Qed.

  Lemma gmap_view_both_dfrac_validN n dp m k dq v :
    ✓{n} (gmap_view_auth dp m gmap_view_frag k dq v)
       v' dq', dp m !! k = Some v' ✓{n} (dq', v')
                Some (dq, v) ≼{n} Some (dq', v').
  Proof.
    rewrite /gmap_view_auth /gmap_view_frag.
    rewrite view_both_dfrac_validN gmap_view_rel_lookup. naive_solver.
  Qed.
  Lemma gmap_view_both_validN n dp m k v :
    ✓{n} (gmap_view_auth dp m gmap_view_frag k (DfracOwn 1) v)
       dp ✓{n} v m !! k ≡{n}≡ Some v.
  Proof.
    rewrite gmap_view_both_dfrac_validN. split.
    - intros [Hdp (v' & dq' & Hlookup & Hvalid & Hincl)].
      split; first done. rewrite Hlookup.
      destruct (Some_includedN_exclusive _ _ _ Hincl Hvalid) as [_ Heq].
      simpl in Heq. split.
      + rewrite pair_validN in Hvalid. rewrite Heq. naive_solver.
      + by rewrite Heq.
    - intros (Hdp & Hval & Hlookup).
      apply dist_Some_inv_r' in Hlookup as [v' [Hlookup Heq]].
       v', (DfracOwn 1). do 2 (split; [done|]). split.
      + rewrite pair_validN. by rewrite -Heq.
      + by apply: Some_includedN_refl.
  Qed.
The backwards direction here does not hold: if dq = DfracOwn 1 but v v', we have to find a suitable erased fraction dq' to satisfy the view relation, but there is no way to satisfy Some (DfracOwn 1, v) ≼{n} Some (dq', v') for any dq'. The "if and only if" version of this lemma would have to involve some extra condition like dq = DfracOwn 1 v = v', or phrased more like the view relation itself: dq', dq' Some (v, dq) ≼{n} Some (v', dq').
  Lemma gmap_view_both_dfrac_validN_total `{!CmraTotal V} n dp m k dq v :
    ✓{n} (gmap_view_auth dp m gmap_view_frag k dq v)
     v', dp dq m !! k = Some v' ✓{n} v' v ≼{n} v'.
  Proof.
    rewrite gmap_view_both_dfrac_validN.
    intros (v' & dq' & Hdp & Hlookup & Hvalid & Hincl).
     v'. split; first done. split.
    - eapply (cmra_valid_Some_included dq'); first by apply Hvalid.
      eapply cmra_discrete_included_iff.
      eapply Some_pair_includedN_l. done.
    - split; first done. split; first apply Hvalid.
      move:Hincl⇒ /Some_pair_includedN_r /Some_includedN_total. done.
  Qed.

Without CmraDiscrete, we cannot do much better than n, <same as above>. This is because both the dq' and the witness for the ≼{n} can be different for each step-index. It is totally possible that at low step-indices, v has a frame (and dq' > dq) while at higher step-indices, v has no frame (and dq' = dq).
  Lemma gmap_view_both_dfrac_valid_discrete `{!CmraDiscrete V} dp m k dq v :
     (gmap_view_auth dp m gmap_view_frag k dq v)
       v' dq', dp m !! k = Some v'
                 (dq', v')
                Some (dq, v) Some (dq', v').
  Proof.
    rewrite cmra_valid_validN. setoid_rewrite gmap_view_both_dfrac_validN. split.
    - intros Hvalid. specialize (Hvalid 0).
      destruct Hvalid as (v' & dq' & Hdp & Hlookup & Hvalid & Hincl).
       v', dq'. do 2 (split; first done).
      split; first by apply cmra_discrete_valid.
      by apply: cmra_discrete_included_r.
    - intros (v' & dq' & Hdp & Hlookup & Hvalid & Hincl) n.
       v', dq'. do 2 (split; first done).
      split; first by apply cmra_valid_validN.
      by apply: cmra_included_includedN.
  Qed.
The backwards direction here does not hold: if dq = DfracOwn 1 but v v', we have to find a suitable erased fraction dq' to satisfy the view relation, but there is no way to satisfy Some (DfracOwn 1, v) Some (dq', v') for any dq'. The "if and only if" version of this lemma would have to involve some extra condition like dq = DfracOwn 1 v = v', or phrased more like the view relation itself: dq', dq' Some (v, dq) Some (v', dq').
  Lemma gmap_view_both_dfrac_valid_discrete_total
      `{!CmraDiscrete V, !CmraTotal V} dp m k dq v :
     (gmap_view_auth dp m gmap_view_frag k dq v)
     v', dp dq m !! k = Some v' v' v v'.
  Proof.
    rewrite gmap_view_both_dfrac_valid_discrete.
    intros (v' & dq' & Hdp & Hlookup & Hvalid & Hincl).
     v'. split; first done. split.
    - eapply (cmra_valid_Some_included dq'); first by apply Hvalid.
      eapply Some_pair_included_l. done.
    - split; first done. split; first apply Hvalid.
      move:Hincl⇒ /Some_pair_included_r /Some_included_total. done.
  Qed.
On the other hand, this one holds for all CMRAs, not just discrete ones.
  Lemma gmap_view_both_valid m dp k v :
     (gmap_view_auth dp m gmap_view_frag k (DfracOwn 1) v)
     dp v m !! k Some v.
  Proof.
    rewrite cmra_valid_validN. setoid_rewrite gmap_view_both_validN. split.
    - intros Hvalid. split; last split.
      + eapply (Hvalid 0).
      + apply cmra_valid_validN. intros n. eapply Hvalid.
      + apply equiv_dist. intros n. eapply Hvalid.
    - intros (Hdp & Hval & Hlookup). intros n.
      split; first done. split.
      + apply cmra_valid_validN. done.
      + rewrite Hlookup. done.
  Qed.

Frame-preserving updates
  Lemma gmap_view_alloc m k dq v :
    m !! k = None
     dq
     v
    gmap_view_auth (DfracOwn 1) m ~~>
      gmap_view_auth (DfracOwn 1) (<[k := v]> m) gmap_view_frag k dq v.
  Proof.
    intros Hfresh Hdq Hval. apply view_update_allocn bf Hrel j [df va] /=.
    rewrite lookup_op. destruct (decide (j = k)) as [->|Hne].
    - assert (bf !! k = None) as Hbf.
      { destruct (bf !! k) as [[df' va']|] eqn:Hbf; last done.
        specialize (Hrel _ _ Hbf). destruct Hrel as (v' & dq' & Hm & _).
        exfalso. rewrite Hm in Hfresh. done. }
      rewrite lookup_singleton Hbf right_id.
      intros [= <- <-]. eexists _, _.
      rewrite lookup_insert. split; first done.
      split; last by apply: Some_includedN_refl.
      split; first done. by eapply cmra_valid_validN.
    - rewrite lookup_singleton_ne; last done.
      rewrite left_idHbf.
      specialize (Hrel _ _ Hbf). destruct Hrel as (v' & ? & Hm & ?).
      eexists _, _. split; last done.
      rewrite lookup_insert_ne //.
  Qed.

  Lemma gmap_view_alloc_big m m' dq :
    m' ##ₘ m
     dq
    map_Forall (λ k v, v) m'
    gmap_view_auth (DfracOwn 1) m ~~>
      gmap_view_auth (DfracOwn 1) (m' m)
      ([^op map] kv m', gmap_view_frag k dq v).
  Proof.
    intros ?? Hm'.
    induction m' as [|k v m' ? IH] using map_ind; decompose_map_disjoint.
    { rewrite big_opM_empty left_id_L right_id. done. }
    apply map_Forall_insert in Hm' as [??]; last done.
    rewrite IH //. rewrite big_opM_insert // assoc.
    apply cmra_update_op; last done.
    rewrite -insert_union_l. apply (gmap_view_alloc _ k dq); [|done..].
    by apply lookup_union_None.
  Qed.

  Lemma gmap_view_delete m k v :
    gmap_view_auth (DfracOwn 1) m gmap_view_frag k (DfracOwn 1) v ~~>
    gmap_view_auth (DfracOwn 1) (delete k m).
  Proof.
    apply view_update_deallocn bf Hrel j [df va] Hbf /=.
    destruct (decide (j = k)) as [->|Hne].
    - edestruct (Hrel k) as (v' & dq' & ? & Hval & Hincl).
      { rewrite lookup_op Hbf lookup_singleton -Some_op. done. }
      eapply (cmra_validN_Some_includedN _ _ _ Hval) in Hincl as Hval'.
      exfalso. clear Hval Hincl.
      rewrite pair_validN /= in Hval'.
      apply: dfrac_full_exclusive. apply Hval'.
    - edestruct (Hrel j) as (v' & ? & ? & ?).
      { rewrite lookup_op lookup_singleton_ne // Hbf. done. }
      eexists v', _. split; last done.
      rewrite lookup_delete_ne //.
  Qed.

  Lemma gmap_view_delete_big m m' :
    gmap_view_auth (DfracOwn 1) m
    ([^op map] kv m', gmap_view_frag k (DfracOwn 1) v) ~~>
      gmap_view_auth (DfracOwn 1) (m m').
  Proof.
    induction m' as [|k v m' ? IH] using map_ind.
    { rewrite right_id_L big_opM_empty right_id //. }
    rewrite big_opM_insert //.
    rewrite [gmap_view_frag _ _ _ _]comm assoc IH gmap_view_delete.
    rewrite -delete_difference. done.
  Qed.

We do not use local_update (¬l~>) in the premise because we also want to expose the role of the fractions.
  Lemma gmap_view_update m k dq v mv' v' dq' :
    ( n mv f,
      m !! k = Some mv
      ✓{n} ((dq, v) ⋅? f)
      mv ≡{n}≡ v ⋅? (snd <$> f)
      ✓{n} ((dq', v') ⋅? f) mv' ≡{n}≡ v' ⋅? (snd <$> f))
    gmap_view_auth (DfracOwn 1) m gmap_view_frag k dq v ~~>
      gmap_view_auth (DfracOwn 1) (<[k := mv']> m) gmap_view_frag k dq' v'.
  Proof.
    intros Hup. apply view_updaten bf Hrel j [df va].
    rewrite lookup_op.
    destruct (decide (j = k)) as [->|Hne]; last first.
    {
      simplify_map_eq. rewrite lookup_singleton_ne //.
      rewrite left_id. intros Hbf.
      edestruct (Hrel j) as (mva & mdf & Hlookup & Hval & Hincl).
      { rewrite lookup_op lookup_singleton_ne // left_id //. }
      naive_solver. }
    simplify_map_eq. rewrite lookup_singleton.
    intros Hbf.
    edestruct (Hrel k) as (mv & mdf & Hlookup & Hval & Hincl).
    { rewrite lookup_op lookup_singleton // Some_op_opM //. }
    rewrite Some_includedN_opM in Hincl.
    destruct Hincl as [f' Hincl]. rewrite cmra_opM_opM_assoc in Hincl.
    set f := bf !! k f'.     change (bf !! k f') with f in Hincl.
    specialize (Hup n mv f). destruct Hup as (Hval' & Hincl').
    { done. }
    { rewrite -Hincl. done. }
    { destruct Hincl as [_ Hincl]. simpl in Hincl. rewrite Hincl.
      by destruct f. }
    eexists mv', (dq' ⋅? (fst <$> f)). split; first done.
    rewrite -Hbf. clear Hbf. split.
    - rewrite Hincl'. destruct Hval'. by destruct f.
    - rewrite Some_op_opM. rewrite Some_includedN_opM.
       f'. rewrite Hincl'.
      rewrite cmra_opM_opM_assoc. change (bf !! k f') with f.
      by destruct f.
  Qed.

This derived version cannot exploit dq = DfracOwn 1.
  Lemma gmap_view_update_local m k dq mv v mv' v' :
    m !! k = Some mv
    (mv, v) ¬l~> (mv', v')
    gmap_view_auth (DfracOwn 1) m gmap_view_frag k dq v ~~>
    gmap_view_auth (DfracOwn 1) (<[k := mv']> m) gmap_view_frag k dq v'.
  Proof.
    intros Hlookup Hup. apply gmap_view_update.
    intros n mv0 f Hmv0 Hval Hincl.
    rewrite Hlookup in Hmv0. injection Hmv0 as [= <-].
    specialize (Hup n (snd <$> f)). destruct Hup as (Hval' & Hincl').
    { rewrite Hincl. destruct Hval. by destruct f. }
    { simpl. done. }
    split; last done. split.
    - destruct Hval. by destruct f.
    - simpl in ×. replace (((dq, v') ⋅? f).2) with (v' ⋅? (snd <$> f)).
      2:{ by destruct f. }
      rewrite -Hincl'. done.
  Qed.

  Lemma gmap_view_replace m k v v' :
     v'
    gmap_view_auth (DfracOwn 1) m gmap_view_frag k (DfracOwn 1) v ~~>
      gmap_view_auth (DfracOwn 1) (<[k := v']> m) gmap_view_frag k (DfracOwn 1) v'.
  Proof.
    intros Hval'. apply gmap_view_update.
    intros n mv f Hlookup Hval Hincl.
    destruct f; simpl.
    { apply exclusiveN_l in Hval; first done. apply _. }
    split; last done.
    split; first done. simpl. apply cmra_valid_validN. done.
  Qed.

  Lemma gmap_view_replace_big m m0 m1 :
    dom m0 = dom m1
    map_Forall (λ k v, v) m1
    gmap_view_auth (DfracOwn 1) m
    ([^op map] kv m0, gmap_view_frag k (DfracOwn 1) v) ~~>
      gmap_view_auth (DfracOwn 1) (m1 m)
      ([^op map] kv m1, gmap_view_frag k (DfracOwn 1) v).
  Proof.
    intros Hdom%eq_sym. revert m1 Hdom.
    induction m0 as [|k v m0 Hnotdom IH] using map_ind; intros m1 Hdom Hval.
    { rewrite dom_empty_L in Hdom.
      apply dom_empty_iff_L in Hdom as →.
      rewrite left_id_L big_opM_empty. done. }
    rewrite dom_insert_L in Hdom.
    assert (k dom m1) as Hindom by set_solver.
    apply elem_of_dom in Hindom as [v' Hlookup].
    rewrite big_opM_insert //.
    rewrite [gmap_view_frag _ _ _ _]comm assoc.
    rewrite (IH (delete k m1)); last first.
    { by apply map_Forall_delete. }
    { rewrite dom_delete_L Hdom.
      apply not_elem_of_dom in Hnotdom. set_solver -Hdom. }
    rewrite -assoc [_ gmap_view_frag _ _ _]comm assoc.
    rewrite (gmap_view_replace _ _ _ v').
    2:{ eapply Hval. done. }
    rewrite (big_opM_delete _ m1 k v') // -assoc.
    rewrite insert_union_r; last by rewrite lookup_delete.
    rewrite union_delete_insert //.
  Qed.

  Lemma gmap_view_auth_persist dq m :
    gmap_view_auth dq m ~~> gmap_view_auth DfracDiscarded m.
  Proof. apply view_update_auth_persist. Qed.

  Lemma gmap_view_auth_unpersist m :
    gmap_view_auth DfracDiscarded m ~~>: λ a, q, a = gmap_view_auth (DfracOwn q) m.
  Proof. apply view_updateP_auth_unpersist. Qed.

  Local Lemma gmap_view_frag_dfrac k dq P v :
    dq ~~>: P
    gmap_view_frag k dq v ~~>: λ a, dq', a = gmap_view_frag k dq' v P dq'.
  Proof.
    intros Hdq.
    eapply cmra_updateP_weaken;
      [apply view_updateP_frag
         with (P := λ b', dq', V b' = gmap_view_frag k dq' v P dq')
      |naive_solver].
    intros m n bf Hrel.
    destruct (Hrel k ((dq, v) ⋅? bf !! k)) as (v' & dq' & Hlookup & Hval & Hincl).
    { by rewrite lookup_op lookup_singleton Some_op_opM. }
    rewrite Some_includedN_opM in Hincl.
    destruct Hincl as [f' Hincl]. rewrite cmra_opM_opM_assoc in Hincl.
    set f := bf !! k f'.     change (bf !! k f') with f in Hincl.
    destruct (Hdq n (option_map fst f)) as (dq'' & HPdq'' & Hvdq'').
    { destruct Hincl as [Heq _]. simpl in Heq. rewrite Heq in Hval.
      destruct Hval as [Hval _]. by destruct f. }
    eexists. split; first by dq''.
    intros j [df va] Heq.
    destruct (decide (k = j)) as [->|Hne].
    - rewrite lookup_op lookup_singleton in Heq.
      eexists v', (dq'' ⋅? (fst <$> f)).
      split; first done. split.
      + split; last by apply Hval. simpl. done.
      + rewrite -Heq. f'.
        rewrite -assoc. change (bf !! j f') with f.
        destruct Hincl as [_ Hincl]. simpl in Hincl. rewrite Hincl.
        by destruct f.
    - rewrite lookup_op lookup_singleton_ne // left_id in Heq.
      eapply Hrel. rewrite lookup_op lookup_singleton_ne // left_id Heq //.
  Qed.

  Lemma gmap_view_frag_persist k dq v :
    gmap_view_frag k dq v ~~> gmap_view_frag k DfracDiscarded v.
  Proof.
    eapply (cmra_update_lift_updateP (λ dq, gmap_view_frag k dq v)).
    - intros. by apply gmap_view_frag_dfrac.
    - apply dfrac_discard_update.
  Qed.

  Lemma gmap_view_frag_unpersist k v :
    gmap_view_frag k DfracDiscarded v ~~>:
      λ a, q, a = gmap_view_frag k (DfracOwn q) v.
  Proof.
    eapply cmra_updateP_weaken.
    { apply gmap_view_frag_dfrac, dfrac_undiscard_update. }
    naive_solver.
  Qed.

Typeclass instances
  Global Instance gmap_view_frag_core_id k dq v :
    CoreId dq CoreId v CoreId (gmap_view_frag k dq v).
  Proof. apply _. Qed.

  Global Instance gmap_view_cmra_discrete :
    CmraDiscrete V CmraDiscrete (gmap_viewR K V).
  Proof. apply _. Qed.

  Global Instance gmap_view_frag_mut_is_op dq dq1 dq2 k v v1 v2 :
    IsOp dq dq1 dq2
    IsOp v v1 v2
    IsOp' (gmap_view_frag k dq v) (gmap_view_frag k dq1 v1) (gmap_view_frag k dq2 v2).
  Proof. rewrite /IsOp' /IsOp ⇒ → →. apply gmap_view_frag_op. Qed.
End lemmas.

Functor
Program Definition gmap_viewURF (K : Type) `{Countable K} (F : rFunctor) : urFunctor := {|
  urFunctor_car A _ B _ := gmap_viewUR K (rFunctor_car F A B);
  urFunctor_map A1 _ A2 _ B1 _ B2 _ fg :=
    viewO_map (rel:=gmap_view_rel K (rFunctor_car F A1 B1))
              (rel':=gmap_view_rel K (rFunctor_car F A2 B2))
              (gmapO_map (K:=K) (rFunctor_map F fg))
              (gmapO_map (K:=K) (prodO_map cid (rFunctor_map F fg)))
|}.
Next Obligation.
  intros K ?? F A1 ? A2 ? B1 ? B2 ? n f g Hfg.
  apply viewO_map_ne.
  - apply gmapO_map_ne, rFunctor_map_ne. done.
  - apply gmapO_map_ne. apply prodO_map_ne; first done.
    apply rFunctor_map_ne. done.
Qed.
Next Obligation.
  intros K ?? F A ? B ? x; simpl in ×. rewrite -{2}(view_map_id x).
  apply (view_map_ext _ _ _ _)=> y.
  - rewrite /= -{2}(map_fmap_id y).
    apply: map_fmap_equiv_extk ??.
    apply rFunctor_map_id.
  - rewrite /= -{2}(map_fmap_id y).
    apply: map_fmap_equiv_extk [df va] ?.
    split; first done. simpl.
    apply rFunctor_map_id.
Qed.
Next Obligation.
  intros K ?? F A1 ? A2 ? A3 ? B1 ? B2 ? B3 ? f g f' g' x; simpl in ×.
  rewrite -view_map_compose.
  apply (view_map_ext _ _ _ _)=> y.
  - rewrite /= -map_fmap_compose.
    apply: map_fmap_equiv_extk ??.
    apply rFunctor_map_compose.
  - rewrite /= -map_fmap_compose.
    apply: map_fmap_equiv_extk [df va] ?.
    split; first done. simpl.
    apply rFunctor_map_compose.
Qed.
Next Obligation.
  intros K ?? F A1 ? A2 ? B1 ? B2 ? fg; simpl.
  apply: view_map_cmra_morphism; [apply _..|]=> n m f.
  intros Hrel k [df va] Hf. move: Hf.
  rewrite !lookup_fmap.
  destruct (f !! k) as [[df' va']|] eqn:Hfk; rewrite Hfk; last done.
  simpl=>[= <- <-].
  specialize (Hrel _ _ Hfk). simpl in Hrel.
  destruct Hrel as (v & dq & Hlookup & Hval & Hincl).
  eexists (rFunctor_map F fg v), dq.
  rewrite Hlookup. split; first done. split.
  - split; first by apply Hval. simpl. apply: cmra_morphism_validN. apply Hval.
  - destruct Hincl as [[[fdq fv]|] Hincl].
    + apply: Some_includedN_mono. rewrite -Some_op in Hincl.
      apply (inj _) in Hincl. rewrite -pair_op in Hincl.
       (fdq, rFunctor_map F fg fv). rewrite -pair_op.
      split; first apply Hincl. rewrite -cmra_morphism_op.
      simpl. f_equiv. apply Hincl.
    + None. rewrite right_id in Hincl. apply (inj _) in Hincl.
      rewrite right_id. f_equiv. split; first apply Hincl.
      simpl. f_equiv. apply Hincl.
Qed.

Global Instance gmap_viewURF_contractive (K : Type) `{Countable K} F :
  rFunctorContractive F urFunctorContractive (gmap_viewURF K F).
Proof.
  intros ? A1 ? A2 ? B1 ? B2 ? n f g Hfg.
  apply viewO_map_ne.
  - apply gmapO_map_ne. apply rFunctor_map_contractive. done.
  - apply gmapO_map_ne. apply prodO_map_ne; first done.
    apply rFunctor_map_contractive. done.
Qed.

Program Definition gmap_viewRF (K : Type) `{Countable K} (F : rFunctor) : rFunctor := {|
  rFunctor_car A _ B _ := gmap_viewR K (rFunctor_car F A B);
  rFunctor_map A1 _ A2 _ B1 _ B2 _ fg :=
    viewO_map (rel:=gmap_view_rel K (rFunctor_car F A1 B1))
              (rel':=gmap_view_rel K (rFunctor_car F A2 B2))
              (gmapO_map (K:=K) (rFunctor_map F fg))
              (gmapO_map (K:=K) (prodO_map cid (rFunctor_map F fg)))
|}.
Solve Obligations with apply gmap_viewURF.

Global Instance gmap_viewRF_contractive (K : Type) `{Countable K} F :
  rFunctorContractive F rFunctorContractive (gmap_viewRF K F).
Proof. apply gmap_viewURF_contractive. Qed.

Global Typeclasses Opaque gmap_view_auth gmap_view_frag.