open import Level
open import Category 
module CCCgraph1 where

open import HomReasoning
open import cat-utility
open import  Relation.Binary.PropositionalEquality hiding ( [_] )
open import CCC
open import graph

module ccc-from-graph {c₁  c₂  : Level} (G : Graph {c₁} {c₂} )  where
   open import  Relation.Binary.PropositionalEquality hiding ( [_] )
   open import  Relation.Binary.Core 
   open Graph
   
   data Objs : Set (c₁ ⊔ c₂) where
      atom : (vertex G) → Objs 
      ⊤ : Objs 
      _∧_ : Objs  → Objs  → Objs 
      _<=_ : Objs → Objs → Objs 

   data Arrow :  Objs → Objs → Set (c₁ ⊔ c₂)  where                       --- case i
      arrow : {a b : vertex G} →  (edge G) a b → Arrow (atom a) (atom b)
      π : {a b : Objs } → Arrow ( a ∧ b ) a
      π' : {a b : Objs } → Arrow ( a ∧ b ) b
      ε : {a b : Objs } → Arrow ((a <= b) ∧ b ) a
      _* : {a b c : Objs } → Arrow (c ∧ b ) a → Arrow c ( a <= b )        --- case v

   data  Arrows  : (b c : Objs ) → Set ( c₁  ⊔  c₂ ) where
      id : ( a : Objs ) → Arrows a a                                      --- case i
      ○ : ( a : Objs ) → Arrows a ⊤                                       --- case i
      <_,_> : {a b c : Objs } → Arrows c a → Arrows c b → Arrows c (a ∧ b)   --- case iii
      iv  : {b c d : Objs } ( f : Arrow d c ) ( g : Arrows b d ) → Arrows b c   -- cas iv

   eval :  {a b : Objs } (f : Arrows a b ) → Arrows a b
   eval (id a) = id a
   eval (○ a) = ○ a
   eval < f , f₁ > = < eval f , eval f₁ >
   eval (iv π < f , g > ) =  eval f
   eval (iv π' < f , g > ) = eval g
   eval (iv f g) = iv f (eval g)

   _・_ :  {a b c : Objs } (f : Arrows b c ) → (g : Arrows a b) → Arrows a c
   id a ・ g = eval g
   < f , g > ・  h = <  f ・ h  ,  g ・ h  >
   iv f (id _) ・ h = iv f (eval h)
   iv π < g , g₁ > ・  h = g ・ h
   iv π' < g , g₁ > ・  h = g₁ ・ h
   iv ε < g , g₁ > ・  h = iv ε < g ・ h , g₁ ・ h >
   iv (f *) < g , g₁ > ・ h = iv (f *) < g ・ h , g₁ ・ h > 
   iv f ( (○ a)) ・ g = iv f ( ○ _ )
   iv x y ・ id a = iv x (eval y)
   iv f (iv f₁ g) ・ h = iv f (  iv f₁ g ・ h )
   ○ a ・ g = ○ _

   _==_  : {a b : Objs } → ( x y : Arrows a b ) → Set (c₁ ⊔ c₂)
   _==_ {a} {b} x y   = eval x  ≡ eval  y 

   identityR : {A B : Objs} {f : Arrows A B} → (f ・ id A) == f
   identityR {a} {.a} {id a} = refl
   identityR {a} {.⊤} {○ a} = refl
   identityR {a} {.(_ ∧ _)} {< f , f₁ >} = cong₂ (λ j k → < j , k > ) (identityR {_} {_} {f} ) (identityR  {_} {_} {f₁})
   identityR {a} {b} {iv f (id a)} = refl
   identityR {a} {b} {iv f (○ a)} = refl
   identityR {a} {b} {iv π < g , g₁ >} = {!!}
   identityR {a} {b} {iv π' < g , g₁ >} = {!!}
   identityR {a} {b} {iv ε < f , f₁ >} = cong₂ (λ j k → iv ε < j , k > ) (identityR {_} {_} {f} ) (identityR  {_} {_} {f₁})
   identityR {a} {_} {iv (x *) < f , f₁ >} = cong₂ (λ j k → iv (x *) < j , k > ) (identityR {_} {_} {f} ) (identityR  {_} {_} {f₁})
   identityR {a} {b} {iv f (iv g h)} = {!!}

   ==←≡ : {A B : Objs} {f g : Arrows A B} → f ≡ g → f == g
   ==←≡ eq = cong (λ k → eval k ) eq

   PL :  Category  (c₁ ⊔ c₂) (c₁ ⊔ c₂) (c₁ ⊔ c₂)
   PL = record {
            Obj  = Objs;
            Hom = λ a b →  Arrows  a b ;
            _o_ =  λ{a} {b} {c} x y → x ・ y ;
            _≈_ =  λ x y → x  == y ;
            Id  =  λ{a} → id a ;
            isCategory  = record {
                    isEquivalence =  record {refl = refl ; trans = trans ; sym = sym } ;
                    identityL  = λ {a b f} → identityL {a} {b} {f} ; 
                    identityR  = λ {a b f} → identityR {a} {b} {f} ; 
                    o-resp-≈  = λ {a b c f g h i} → o-resp-≈ {a} {b} {c} {f} {g} {h} {i}  ; 
                    associative  = λ{a b c d f g h } → associative  f g h
               }
           }  where
               identityL : {A B : Objs} {f : Arrows A B} → (id B ・ f) == f
               identityL {_} {_} {id a} = refl
               identityL {_} {_} {○ a} = refl
               identityL {a} {b} {< f , f₁ >} = {!!}
               identityL {_} {_} {iv f f₁} = {!!}
               associative : {a b c d : Objs} (f : Arrows c d) (g : Arrows b c) (h : Arrows a b) →
                            (f ・ (g ・ h)) == ((f ・ g) ・ h)
               associative (id a) g h = {!!}
               associative (○ a) g h = refl
               associative (< f , f1 > ) g h = cong₂ ( λ j k → < j , k > ) (associative f g h) (associative f1 g h)
               associative {a} (iv x f) g h = {!!} -- cong ( λ k → iv x k ) (associative f g h) 
               o-resp-≈  : {A B C : Objs} {f g : Arrows A B} {h i : Arrows B C} →
                            f == g → h == i → (h ・ f) == (i ・ g)
               o-resp-≈  f=g h=i = {!!}