module A201605.AltArtemov.Old.GN!.Core where

open import A201605.AltArtemov.Old.GN!.Tm public


data Ty :   Set where
    :  {n}  Ty n
  _⊃_ :  {n}  Ty n  Ty n  Ty n
  _∧_ :  {n}  Ty n  Ty n  Ty n
  _∶_ :  {n}  Tm 0 n  Ty n  Ty (suc n)

infixr 5 _⊃_
infixr 15 _∶_


data Cx : Set where
   : Cx
  _,_ :  {n}  Cx  Ty n  Cx

ᵍ⌊_⌋ : Cx  
ᵍ⌊       = zero
ᵍ⌊ Γ , A  = suc ᵍ⌊ Γ 


data _⊇_ : Cx  Cx  Set where
  base :   
  weak :  {Γ Γ′ n} {A : Ty n}  Γ′  Γ  (Γ′ , A)  Γ
  lift :  {Γ Γ′ n} {A : Ty n}  Γ′  Γ  (Γ′ , A)  (Γ , A)

ʰ⌊_⌋ :  {Γ Γ′}  Γ′  Γ  ᵍ⌊ Γ′   ᵍ⌊ Γ 
ʰ⌊ base    = base
ʰ⌊ weak η  = weak ʰ⌊ η 
ʰ⌊ lift η  = lift ʰ⌊ η 

⊇id :  {Γ}  Γ  Γ
⊇id {}     = base
⊇id {Γ , A} = lift ⊇id

⊇to :  {Γ}  Γ  
⊇to {}     = base
⊇to {Γ , A} = weak ⊇to

⊇wk :  {Γ n} {A : Ty n}  (Γ , A)  Γ
⊇wk = weak ⊇id

⊇str :  {Γ Γ′ n} {A : Ty n}  Γ′  (Γ , A)  Γ′  Γ
⊇str (weak η) = weak (⊇str η)
⊇str (lift η) = weak η

⊇drop :  {Γ Γ′ n} {A : Ty n}  (Γ′ , A)  (Γ , A)  Γ′  Γ
⊇drop (weak η) = ⊇str η
⊇drop (lift η) = η

_●_ :  {Γ Γ′ Γ″}  Γ″  Γ′  Γ′  Γ  Γ″  Γ
base     η      = η
weak η′  η      = weak (η′  η)
lift η′  weak η = weak (η′  η)
lift η′  lift η = lift (η′  η)

η●id :  {Γ Γ′} (η : Γ′  Γ)  η  ⊇id  η
η●id base     = refl
η●id (weak η) = cong weak (η●id η)
η●id (lift η) = cong lift (η●id η)

id●η :  {Γ Γ′} (η : Γ′  Γ)  ⊇id  η  η
id●η base     = refl
id●η (weak η) = cong weak (id●η η)
id●η (lift η) = cong lift (id●η η)

id-⌊⌋-id :  Γ  ʰ⌊ ⊇id {Γ}   ≥id {ᵍ⌊ Γ }
id-⌊⌋-id        = refl
id-⌊⌋-id (Γ , A) = cong lift (id-⌊⌋-id Γ)

to-⌊⌋-to :  Γ  ʰ⌊ ⊇to {Γ}   ≥to {ᵍ⌊ Γ }
to-⌊⌋-to        = refl
to-⌊⌋-to (Γ , A) = cong weak (to-⌊⌋-to Γ)

ren-fin-⌊⌋-id :  {Γ} (i : Fin ᵍ⌊ Γ )  ren-fin ʰ⌊ ⊇id  i  i
ren-fin-⌊⌋-id {Γ} i rewrite id-⌊⌋-id Γ = ren-fin-id i

ren-tm-⌊⌋-id :  {Γ n} (t : Tm ᵍ⌊ Γ  n)  ren-tm ʰ⌊ ⊇id  t  t
ren-tm-⌊⌋-id {Γ} t rewrite id-⌊⌋-id Γ = ren-tm-id t


data Var :  {n}  Cx  Ty n  Set where
  top :  {Γ n}  {A : Ty n}  Var (Γ , A) A
  pop :  {Γ n n′} {A : Ty n} {B : Ty n′}  Var Γ A  Var (Γ , B) A

ⁱ⌊_⌋ :  {Γ n} {A : Ty n}  Var Γ A  Fin ᵍ⌊ Γ 
ⁱ⌊ top    = zero
ⁱ⌊ pop x  = suc ⁱ⌊ x 

ren-var :  {Γ Γ′ n} {A : Ty n}  Γ′  Γ  Var Γ A  Var Γ′ A
ren-var base     x       = x
ren-var (weak η) x       = pop (ren-var η x)
ren-var (lift η) top     = top
ren-var (lift η) (pop x) = pop (ren-var η x)

wk-var :  {Γ n n′} {A : Ty n} {C : Ty n′}  Var Γ C  Var (Γ , A) C
wk-var = ren-var ⊇wk

wk*-var :  {Γ n} {C : Ty n}  Var  C  Var Γ C
wk*-var ()

ren-var-id :  {Γ n} {A : Ty n} (x : Var Γ A)  ren-var ⊇id x  x
ren-var-id top     = refl
ren-var-id (pop x) = cong pop (ren-var-id x)

ren-var-● :  {Γ Γ′ Γ″ n} {A : Ty n} (η′ : Γ″  Γ′) (η : Γ′  Γ) (x : Var Γ A) 
              ren-var η′ (ren-var η x)  ren-var (η′  η) x
ren-var-● base      η        x       = refl
ren-var-● (weak η′) η        x       = cong pop (ren-var-● η′ η x)
ren-var-● (lift η′) (weak η) x       = cong pop (ren-var-● η′ η x)
ren-var-● (lift η′) (lift η) top     = refl
ren-var-● (lift η′) (lift η) (pop x) = cong pop (ren-var-● η′ η x)

ren-fin-⌊⌋-var :  {Γ Γ′ n} {A : Ty n} (η : Γ′  Γ) (x : Var Γ A) 
                   ren-fin ʰ⌊ η  ⁱ⌊ x   ⁱ⌊ ren-var η x 
ren-fin-⌊⌋-var base     x       = refl
ren-fin-⌊⌋-var (weak η) x       = cong suc (ren-fin-⌊⌋-var η x)
ren-fin-⌊⌋-var (lift η) top     = refl
ren-fin-⌊⌋-var (lift η) (pop x) = cong suc (ren-fin-⌊⌋-var η x)

x₀ :  {Γ n} {A : Ty n}  Var (Γ , A) A
x₀ = top

x₁ :  {Γ n n′} {A : Ty n} {B : Ty n′}  Var ((Γ , A) , B) A
x₁ = pop x₀

x₂ :  {Γ n n′ n″} {A : Ty n} {B : Ty n′} {C : Ty n″}  Var (((Γ , A) , B) , C) A
x₂ = pop x₁