module A201605.AltArtemov.Old.Common.Var.Basic where

open import A201605.AltArtemov.Old.Common.OPE.Basic public


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