Mcltt.Core.Soundness.LogicalRelation.Definitions

From Coq Require Import Relation_Definitions RelationClasses.
From Equations Require Import Equations.

From Mcltt Require Import LibTactics.
From Mcltt.Core Require Import Base.
From Mcltt.Core.Semantic Require Export PER.
From Mcltt.Core.Soundness.Weakening Require Export Definitions.

Import Domain_Notations.
Global Open Scope predicate_scope.

Generalizable All Variables.

Notation "'glu_typ_pred_args'" := (Tcons ctx (Tcons typ Tnil)).
Notation "'glu_typ_pred'" := (predicate glu_typ_pred_args).
Notation "'glu_typ_pred_equivalence'" := (@predicate_equivalence glu_typ_pred_args) (only parsing).
This type annotation is to distinguish this notation from others
Notation "Γ ⊢ A ® R" := ((R Γ A : (Prop : Type)) : (Prop : (Type : Type))) (in custom judg at level 80, Γ custom exp, A custom exp, R constr).

Notation "'glu_exp_pred_args'" := (Tcons ctx (Tcons typ (Tcons exp (Tcons domain Tnil)))).
Notation "'glu_exp_pred'" := (predicate glu_exp_pred_args).
Notation "'glu_exp_pred_equivalence'" := (@predicate_equivalence glu_exp_pred_args) (only parsing).
Notation "Γ ⊢ M : A ® m ∈ R" := (R Γ A M m : (Prop : (Type : Type))) (in custom judg at level 80, Γ custom exp, M custom exp, A custom exp, m custom domain, R constr).

Notation "'glu_sub_pred_args'" := (Tcons ctx (Tcons sub (Tcons env Tnil))).
Notation "'glu_sub_pred'" := (predicate glu_sub_pred_args).
Notation "'glu_sub_pred_equivalence'" := (@predicate_equivalence glu_sub_pred_args) (only parsing).
Notation "Γ ⊢s σ ® ρ ∈ R" := ((R Γ σ ρ : Prop) : (Prop : (Type : Type))) (in custom judg at level 80, Γ custom exp, σ custom exp, ρ custom domain, R constr).

Notation "'DG' a ∈ R ↘ P ↘ El" := (R P El a : ((Prop : Type) : (Type : Type))) (in custom judg at level 90, a custom domain, R constr, P constr, El constr).
Notation "'EG' A ∈ R ↘ Sb " := (R Sb A : ((Prop : (Type : Type)) : (Type : Type))) (in custom judg at level 90, A custom exp, R constr, Sb constr).

Inductive glu_nat : ctx -> exp -> domain -> Prop :=
| glu_nat_zero :
  `{ {{ Γ M zero : }} ->
     glu_nat Γ M d{{{ zero }}} }
| glu_nat_succ :
  `{ {{ Γ M succ M' : }} ->
     glu_nat Γ M' m' ->
     glu_nat Γ M d{{{ succ m' }}} }
| glu_nat_neut :
  `{ per_bot m m ->
     (forall {Δ σ M'}, {{ Δ w σ : Γ }} -> {{ Rne m in length Δ M' }} -> {{ Δ M[σ] M' : }}) ->
     glu_nat Γ M d{{{ a m }}} }.

#[export]
Hint Constructors glu_nat : mcltt.

Definition nat_glu_typ_pred i : glu_typ_pred := fun Γ A => {{ Γ A : Type@i }}.
Arguments nat_glu_typ_pred i Γ A/.

Definition nat_glu_exp_pred i : glu_exp_pred := fun Γ A M m => {{ Γ A ® nat_glu_typ_pred i }} /\ glu_nat Γ M m.
Arguments nat_glu_exp_pred i Γ A M m/.

Definition neut_glu_typ_pred i a : glu_typ_pred :=
  fun Γ A => {{ Γ A : Type@i }} /\
            (forall Δ σ A', {{ Δ w σ : Γ }} -> {{ Rne a in length Δ A' }} -> {{ Δ A[σ] A' : Type@i }}).
Arguments neut_glu_typ_pred i a Γ A/.

Variant neut_glu_exp_pred i a : glu_exp_pred :=
| mk_neut_glu_exp_pred :
  `{ {{ Γ A ® neut_glu_typ_pred i a }} ->
     {{ Γ M : A }} ->
     {{ Dom m m per_bot }} ->
     (forall Δ σ M', {{ Δ w σ : Γ }} ->
                   {{ Rne m in length Δ M' }} ->
                   {{ Δ M[σ] M' : A[σ] }}) ->
     {{ Γ M : A ® b m neut_glu_exp_pred i a }} }.

Variant pi_glu_typ_pred i
  (IR : relation domain)
  (IP : glu_typ_pred)
  (IEl : glu_exp_pred)
  (OP : forall c (equiv_c : {{ Dom c c IR }}), glu_typ_pred) : glu_typ_pred :=
| mk_pi_glu_typ_pred :
  `{ {{ Γ A Π IT OT : Type@i }} ->
     {{ Γ IT : Type@i }} ->
     {{ Γ , IT OT : Type@i }} ->
     (forall Δ σ, {{ Δ w σ : Γ }} -> {{ Δ IT[σ] ® IP }}) ->
     (forall Δ σ M m,
         {{ Δ w σ : Γ }} ->
         {{ Δ M : IT[σ] ® m IEl }} ->
         forall (equiv_m : {{ Dom m m IR }}),
           {{ Δ OT[σ,,M] ® OP _ equiv_m }}) ->
     {{ Γ A ® pi_glu_typ_pred i IR IP IEl OP }} }.

Variant pi_glu_exp_pred i
  (IR : relation domain)
  (IP : glu_typ_pred)
  (IEl : glu_exp_pred)
  (elem_rel : relation domain)
  (OEl : forall c (equiv_c : {{ Dom c c IR }}), glu_exp_pred): glu_exp_pred :=
| mk_pi_glu_exp_pred :
  `{ {{ Γ M : A }} ->
     {{ Dom m m elem_rel }} ->
     {{ Γ A Π IT OT : Type@i }} ->
     {{ Γ IT : Type@i }} ->
     {{ Γ , IT OT : Type@i }} ->
     (forall Δ σ, {{ Δ w σ : Γ }} -> {{ Δ IT[σ] ® IP }}) ->
     (forall Δ σ N n,
         {{ Δ w σ : Γ }} ->
         {{ Δ N : IT[σ] ® n IEl }} ->
         forall (equiv_n : {{ Dom n n IR }}),
         exists mn, {{ $| m & n |↘ mn }} /\ {{ Δ M[σ] N : OT[σ,,N] ® mn OEl _ equiv_n }}) ->
     {{ Γ M : A ® m pi_glu_exp_pred i IR IP IEl elem_rel OEl }} }.

#[export]
Hint Constructors neut_glu_exp_pred pi_glu_typ_pred pi_glu_exp_pred : mcltt.

Definition univ_glu_typ_pred j i : glu_typ_pred := fun Γ A => {{ Γ A Type@j : Type@i }}.
Arguments univ_glu_typ_pred j i Γ A/.
Transparent univ_glu_typ_pred.

Section Gluing.
  Variable
    (i : nat)
      (glu_univ_typ_rec : forall {j}, j < i -> domain -> glu_typ_pred).

  Definition univ_glu_exp_pred' {j} (lt_j_i : j < i) : glu_exp_pred :=
    fun Γ A M m =>
      {{ Γ M : A }} /\
        {{ Γ A Type@j : Type@i }} /\
        {{ Γ M ® glu_univ_typ_rec lt_j_i m }}.

  #[global]
  Arguments univ_glu_exp_pred' {j} lt_j_i Γ A M m/.

  Inductive glu_univ_elem_core : glu_typ_pred -> glu_exp_pred -> domain -> Prop :=
  | glu_univ_elem_core_univ :
    `{ forall typ_rel
         el_rel
         (lt_j_i : j < i),
          typ_rel <∙> univ_glu_typ_pred j i ->
          el_rel <∙> univ_glu_exp_pred' lt_j_i ->
          {{ DG 𝕌@j glu_univ_elem_core typ_rel el_rel }} }

  | glu_univ_elem_core_nat :
    `{ forall typ_rel el_rel,
          typ_rel <∙> nat_glu_typ_pred i ->
          el_rel <∙> nat_glu_exp_pred i ->
          {{ DG glu_univ_elem_core typ_rel el_rel }} }

  | glu_univ_elem_core_pi :
    `{ forall (in_rel : relation domain)
         IP IEl
         (OP : forall c (equiv_c_c : {{ Dom c c in_rel }}), glu_typ_pred)
         (OEl : forall c (equiv_c_c : {{ Dom c c in_rel }}), glu_exp_pred)
         typ_rel el_rel
         (elem_rel : relation domain),
          {{ DG a glu_univ_elem_core IP IEl }} ->
          {{ DF a a per_univ_elem i in_rel }} ->
          (forall {c} (equiv_c : {{ Dom c c in_rel }}) b,
              {{ B ρ c b }} ->
              {{ DG b glu_univ_elem_core OP _ equiv_c OEl _ equiv_c }}) ->
          {{ DF Π a ρ B Π a ρ B per_univ_elem i elem_rel }} ->
          typ_rel <∙> pi_glu_typ_pred i in_rel IP IEl OP ->
          el_rel <∙> pi_glu_exp_pred i in_rel IP IEl elem_rel OEl ->
          {{ DG Π a ρ B glu_univ_elem_core typ_rel el_rel }} }

  | glu_univ_elem_core_neut :
    `{ forall typ_rel el_rel,
          {{ Dom b b per_bot }} ->
          typ_rel <∙> neut_glu_typ_pred i b ->
          el_rel <∙> neut_glu_exp_pred i b ->
          {{ DG a b glu_univ_elem_core typ_rel el_rel }} }.
End Gluing.

#[export]
Hint Constructors glu_univ_elem_core : mcltt.

Equations glu_univ_elem (i : nat) : glu_typ_pred -> glu_exp_pred -> domain -> Prop by wf i :=
| i => glu_univ_elem_core i (fun j lt_j_i a Γ A => exists P El, {{ DG a glu_univ_elem j P El }} /\ {{ Γ A ® P }}).

Definition glu_univ_typ (i : nat) (a : domain) : glu_typ_pred :=
  fun Γ A => exists P El, {{ DG a glu_univ_elem i P El }} /\ {{ Γ A ® P }}.
Arguments glu_univ_typ i a Γ A/.

Definition univ_glu_exp_pred j i : glu_exp_pred :=
    fun Γ A M m =>
      {{ Γ M : A }} /\ {{ Γ A Type@j : Type@i }} /\
        {{ Γ M ® glu_univ_typ j m }}.
Arguments univ_glu_exp_pred j i Γ A M m/.

Section GluingInduction.
  Hypothesis
    (motive : nat -> glu_typ_pred -> glu_exp_pred -> domain -> Prop)

      (case_univ :
        forall i j
          (P : glu_typ_pred) (El : glu_exp_pred) (lt_j_i : j < i),
          (forall P' El' a, {{ DG a glu_univ_elem j P' El' }} -> motive j P' El' a) ->
          P <∙> univ_glu_typ_pred j i ->
          El <∙> univ_glu_exp_pred j i ->
          motive i P El d{{{ 𝕌 @ j }}})

      (case_nat :
        forall i (P : glu_typ_pred) (El : glu_exp_pred),
          P <∙> nat_glu_typ_pred i ->
          El <∙> nat_glu_exp_pred i ->
          motive i P El d{{{ }}})

      (case_pi :
        forall i a B (ρ : env) (in_rel : relation domain) (IP : glu_typ_pred)
          (IEl : glu_exp_pred) (OP : forall c : domain, {{ Dom c c in_rel }} -> glu_typ_pred)
          (OEl : forall c : domain, {{ Dom c c in_rel }} -> glu_exp_pred) (P : glu_typ_pred) (El : glu_exp_pred)
          (elem_rel : relation domain),
          {{ DG a glu_univ_elem i IP IEl }} ->
          motive i IP IEl a ->
          {{ DF a a per_univ_elem i in_rel }} ->
          (forall (c : domain) (equiv_c : {{ Dom c c in_rel }}) (b : domain),
              {{ B ρ c b }} ->
              {{ DG b glu_univ_elem i OP c equiv_c OEl c equiv_c }}) ->
          (forall (c : domain) (equiv_c : {{ Dom c c in_rel }}) (b : domain),
              {{ B ρ c b }} ->
              motive i (OP c equiv_c) (OEl c equiv_c) b) ->
          {{ DF Π a ρ B Π a ρ B per_univ_elem i elem_rel }} ->
          P <∙> pi_glu_typ_pred i in_rel IP IEl OP ->
          El <∙> pi_glu_exp_pred i in_rel IP IEl elem_rel OEl ->
          motive i P El d{{{ Π a ρ B }}})

      (case_neut :
        forall i b a
          (P : glu_typ_pred)
          (El : glu_exp_pred),
          {{ Dom b b per_bot }} ->
          P <∙> neut_glu_typ_pred i b ->
          El <∙> neut_glu_exp_pred i b ->
          motive i P El d{{{ a b }}})
  .

  #[local]
  Ltac def_simp := simp glu_univ_elem in *; mauto 3.

  #[derive(equations=no, eliminator=no), tactic="def_simp"]
  Equations glu_univ_elem_ind i P El a
    (H : glu_univ_elem i P El a) : motive i P El a by wf i :=
  | i, P, El, a, H =>
      glu_univ_elem_core_ind
        i
        (fun j lt_j_i a Γ A => glu_univ_typ j a Γ A)
        (motive i)
        (fun j P' El' lt_j_i HP' HEl' =>
           case_univ i j P' El' lt_j_i
             (fun P'' El'' A H => glu_univ_elem_ind j P'' El'' A H)
             HP'
             HEl')
        (case_nat i)
        _ (* (case_pi i) *)
        (case_neut i)
        P El a
        _.
  Next Obligation.
    eapply (case_pi i); def_simp; eauto.
  Qed.
End GluingInduction.

Variant glu_elem_bot i a Γ A M m : Prop :=
| glu_elem_bot_make : forall P El,
    {{ Γ M : A }} ->
    {{ DG a glu_univ_elem i P El }} ->
    {{ Γ A ® P }} ->
    {{ Dom m m per_bot }} ->
    (forall Δ σ M', {{ Δ w σ : Γ }} -> {{ Rne m in length Δ M' }} -> {{ Δ M[σ] M' : A[σ] }}) ->
    {{ Γ M : A ® m glu_elem_bot i a }}.
#[export]
Hint Constructors glu_elem_bot : mcltt.

Variant glu_elem_top i a Γ A M m : Prop :=
| glu_elem_top_make : forall P El,
    {{ Γ M : A }} ->
    {{ DG a glu_univ_elem i P El }} ->
    {{ Γ A ® P }} ->
    {{ Dom a m a m per_top }} ->
    (forall Δ σ w, {{ Δ w σ : Γ }} -> {{ Rnf a m in length Δ w }} -> {{ Δ M[σ] w : A[σ] }}) ->
    {{ Γ M : A ® m glu_elem_top i a }}.
#[export]
Hint Constructors glu_elem_top : mcltt.

Variant glu_typ_top i a Γ A : Prop :=
| glu_typ_top_make :
    {{ Γ A : Type@i }} ->
    {{ Dom a a per_top_typ }} ->
    (forall Δ σ A', {{ Δ w σ : Γ }} -> {{ Rtyp a in length Δ A' }} -> {{ Δ A[σ] A' : Type@i }}) ->
    {{ Γ A ® glu_typ_top i a }}.
#[export]
Hint Constructors glu_typ_top : mcltt.

Variant glu_rel_typ_with_sub i Δ A σ ρ : Prop :=
| mk_glu_rel_typ_with_sub :
  `{ forall P El,
        {{ A ρ a }} ->
        {{ DG a glu_univ_elem i P El }} ->
        {{ Δ A[σ] ® P }} ->
        glu_rel_typ_with_sub i Δ A σ ρ }.

Definition nil_glu_sub_pred : glu_sub_pred :=
  fun Δ σ ρ => {{ Δ s σ : }}.
Arguments nil_glu_sub_pred Δ σ ρ/.

The parameters are ordered differently from the Agda version so that we can return glu_sub_pred.
Variant cons_glu_sub_pred i Γ A (TSb : glu_sub_pred) : glu_sub_pred :=
| mk_cons_glu_sub_pred :
  `{ forall P El,
        {{ Δ s σ : Γ, A }} ->
        {{ A ρ a }} ->
        {{ DG a glu_univ_elem i P El }} ->
        
Here we use {{{ A[Wk][σ] }}} instead of {{{ A[Wk∘σ] }}} as syntactic judgement derived from that is a more direct consequence of {{ Γ, A #0 : A[Wk] }}
        {{ Δ #0[σ] : A[Wk][σ] ® ^(ρ 0) El }} ->
        {{ Δ s Wk σ ® ρ TSb }} ->
        {{ Δ s σ ® ρ cons_glu_sub_pred i Γ A TSb }} }.

Inductive glu_ctx_env : glu_sub_pred -> ctx -> Prop :=
| glu_ctx_env_nil :
  `{ forall Sb,
        Sb <∙> nil_glu_sub_pred ->
        {{ EG glu_ctx_env Sb }} }
| glu_ctx_env_cons :
  `{ forall i TSb Sb,
        {{ EG Γ glu_ctx_env TSb }} ->
        {{ Γ A : Type@i }} ->
        (forall Δ σ ρ,
            {{ Δ s σ ® ρ TSb }} ->
            glu_rel_typ_with_sub i Δ A σ ρ) ->
        Sb <∙> cons_glu_sub_pred i Γ A TSb ->
        {{ EG Γ, A glu_ctx_env Sb }} }.

Variant glu_rel_exp_with_sub i Δ M A σ ρ : Prop :=
| mk_glu_rel_exp_with_sub :
  `{ forall P El,
        {{ A ρ a }} ->
        {{ M ρ m }} ->
        {{ DG a glu_univ_elem i P El }} ->
        {{ Δ M[σ] : A[σ] ® m El }} ->
        glu_rel_exp_with_sub i Δ M A σ ρ }.

Variant glu_rel_sub_with_sub Δ τ (Sb : glu_sub_pred) σ ρ : Prop :=
| mk_glu_rel_sub_with_sub :
  `{ {{ τ s ρ ρ' }} ->
     {{ Δ s τ σ ® ρ' Sb }} ->
     glu_rel_sub_with_sub Δ τ Sb σ ρ}.

Definition glu_rel_ctx Γ : Prop := exists Sb, {{ EG Γ glu_ctx_env Sb }}.
Arguments glu_rel_ctx Γ/.

Definition glu_rel_exp Γ M A : Prop :=
  exists Sb,
    {{ EG Γ glu_ctx_env Sb }} /\
      exists i,
      forall Δ σ ρ,
        {{ Δ s σ ® ρ Sb }} ->
        glu_rel_exp_with_sub i Δ M A σ ρ.
Arguments glu_rel_exp Γ M A/.

Definition glu_rel_sub Γ τ Γ' : Prop :=
  exists Sb Sb',
    {{ EG Γ glu_ctx_env Sb }} /\
    {{ EG Γ' glu_ctx_env Sb' }} /\
      forall Δ σ ρ,
        {{ Δ s σ ® ρ Sb }} ->
        glu_rel_sub_with_sub Δ τ Sb' σ ρ.
Arguments glu_rel_sub Γ τ Γ'/.

Notation "⊩ Γ" := (glu_rel_ctx Γ) (in custom judg at level 80, Γ custom exp).
Notation "Γ ⊩ M : A" := (glu_rel_exp Γ M A) (in custom judg at level 80, Γ custom exp, M custom exp, A custom exp).
Notation "Γ ⊩s τ : Γ'" := (glu_rel_sub Γ τ Γ') (in custom judg at level 80, Γ custom exp, τ custom exp, Γ' custom exp).