module Language.Properties where

open import Language.Base
open import Language.Semantics
open import Language.Graphs
open import Language.Traces

open import Data.Fin as Fin using (suc; zero)
open import Data.Fin.Properties as FinProp using (suc-injective)
open import Data.List as List using (List; _∷_; [])
open import Data.List.Properties using (filter-none)
open import Data.List.Relation.Unary.Any using (here; there)
open import Data.List.Relation.Unary.All using (All; []; _∷_; map; tabulate)
open import Data.List.Membership.Propositional as ListMem using ()
open import Data.List.Membership.Propositional.Properties as ListMemProp using ()
open import Data.Nat as Nat using ()
open import Data.Product using (Σ; _,_; _×_; proj₂)
open import Data.Product.Properties as ProdProp using ()
open import Data.Sum using (inj₁; inj₂)
open import Data.Vec as Vec using (_∷_)
open import Data.Vec.Properties using (lookup-++ˡ; ++-identityʳ; lookup-++ʳ)
open import Function using (_∘_)
open import Relation.Binary.PropositionalEquality as Eq using (_≡_; refl; sym; cong)
open import Relation.Nullary using (¬_)

open import Utils using (x∈xs⇒fx∈fxs; ∈-cartesianProduct; concat-∈)

-- All of the below helpers are to reason about what edges aren't included
-- when combinings graphs. The currenty most important use for this is proving
-- that the entry node has no incoming edges.
--
-- -------------- Begin ugly code to make this work ----------------
↑-≢ : ∀ {n m} (f₁ : Fin.Fin n) (f₂ : Fin.Fin m) → ¬ (f₁ Fin.↑ˡ m) ≡ (n Fin.↑ʳ f₂)
↑-≢ zero f₂ ()
↑-≢ (suc f₁') f₂ f₁≡f₂ = ↑-≢ f₁' f₂ (suc-injective f₁≡f₂)

idx→f∉↑ʳᵉ : ∀ {n m} (idx : Fin.Fin (n Nat.+ m)) (f : Fin.Fin n) (es₂ : List (Fin.Fin m × Fin.Fin m)) → ¬ (idx , f Fin.↑ˡ m) ListMem.∈ (n ↑ʳᵉ es₂)
idx→f∉↑ʳᵉ idx f ((idx₁ , idx₂) ∷ es') (here idx,f≡idx₁,idx₂) = ↑-≢ f idx₂ (cong proj₂ idx,f≡idx₁,idx₂)
idx→f∉↑ʳᵉ idx f (_ ∷ es₂') (there idx→f∈es₂') = idx→f∉↑ʳᵉ idx f es₂' idx→f∈es₂'

idx→f∉pair : ∀ {n m} (idx idx' : Fin.Fin (n Nat.+ m)) (f : Fin.Fin n) (inputs₂ : List (Fin.Fin m)) → ¬ (idx , f Fin.↑ˡ m) ListMem.∈ (List.map (idx' ,_) (n ↑ʳⁱ inputs₂))
idx→f∉pair idx idx' f [] ()
idx→f∉pair idx idx' f (input ∷ inputs') (here idx,f≡idx',input) = ↑-≢ f input (cong proj₂ idx,f≡idx',input)
idx→f∉pair idx idx' f (_ ∷ inputs₂') (there idx,f∈inputs₂') = idx→f∉pair idx idx' f inputs₂' idx,f∈inputs₂'

idx→f∉cart : ∀ {n m} (idx : Fin.Fin (n Nat.+ m)) (f : Fin.Fin n) (outputs₁ : List (Fin.Fin n)) (inputs₂ : List (Fin.Fin m)) → ¬ (idx , f Fin.↑ˡ m) ListMem.∈ (List.cartesianProduct (outputs₁ ↑ˡⁱ m) (n ↑ʳⁱ inputs₂))
idx→f∉cart idx f [] inputs₂ ()
idx→f∉cart {n} {m} idx f (output ∷ outputs₁') inputs₂ idx,f∈pair++cart
    with ListMemProp.∈-++⁻ (List.map (output Fin.↑ˡ m ,_) (n ↑ʳⁱ inputs₂)) idx,f∈pair++cart
...   | inj₁ idx,f∈pair = idx→f∉pair idx (output Fin.↑ˡ m) f inputs₂ idx,f∈pair
...   | inj₂ idx,f∈cart = idx→f∉cart idx f outputs₁' inputs₂ idx,f∈cart

help : let g₁ = singleton [] in
       ∀ (g₂ : Graph) (idx₁ : Graph.Index g₁) (idx : Graph.Index (g₁ ↦ g₂)) →
       ¬ (idx , idx₁ Fin.↑ˡ Graph.size g₂) ListMem.∈ ((Graph.size g₁ ↑ʳᵉ Graph.edges g₂) List.++
                                                      (List.cartesianProduct (Graph.outputs g₁ ↑ˡⁱ Graph.size g₂)
                                                                             (Graph.size g₁ ↑ʳⁱ Graph.inputs g₂)))
help g₂ idx₁ idx idx,idx₁∈g
    with ListMemProp.∈-++⁻ (Graph.size (singleton []) ↑ʳᵉ Graph.edges g₂) idx,idx₁∈g
...   | inj₁ idx,idx₁∈edges₂ = idx→f∉↑ʳᵉ idx idx₁ (Graph.edges g₂) idx,idx₁∈edges₂
...   | inj₂ idx,idx₁∈cart = idx→f∉cart idx idx₁ (Graph.outputs (singleton [])) (Graph.inputs g₂) idx,idx₁∈cart

helpAll : let g₁ = singleton [] in
       ∀ (g₂ : Graph) (idx₁ : Graph.Index g₁) →
       All (λ idx → ¬ (idx , idx₁ Fin.↑ˡ Graph.size g₂) ListMem.∈ ((Graph.size g₁ ↑ʳᵉ Graph.edges g₂) List.++
                                                                   (List.cartesianProduct (Graph.outputs g₁ ↑ˡⁱ Graph.size g₂)
                                                                                          (Graph.size g₁ ↑ʳⁱ Graph.inputs g₂)))) (indices (g₁ ↦ g₂))
helpAll g₂ idx₁ = tabulate (λ {idx} _ → help g₂ idx₁ idx)

module _ (g : Graph) where
    wrap-preds-∅ : (idx : Graph.Index (wrap g)) →
                   idx ListMem.∈ Graph.inputs (wrap g) → predecessors (wrap g) idx ≡ []
    wrap-preds-∅ zero (here refl) =
        filter-none (λ idx' → (idx' , zero) ∈?
                              (Graph.edges (wrap g)))
                    (helpAll (g ↦ singleton []) zero)
        where open import Data.List.Membership.DecPropositional (ProdProp.≡-dec (FinProp._≟_ {Graph.size (wrap g)}) (FinProp._≟_ {Graph.size (wrap g)})) using (_∈?_)
-- -------------- End ugly code to make this work ----------------


module _ (g : Graph) where
    wrap-input : Σ (Graph.Index (wrap g)) (λ idx → Graph.inputs (wrap g) ≡ idx ∷ [])
    wrap-input = (_ , refl)

    wrap-output : Σ (Graph.Index (wrap g)) (λ idx → Graph.outputs (wrap g) ≡ idx ∷ [])
    wrap-output = (_ , refl)

Trace-∙ˡ : ∀ {g₁ g₂ : Graph} {idx₁ idx₂ : Graph.Index g₁} {ρ₁ ρ₂ : Env} →
           Trace {g₁} idx₁ idx₂ ρ₁ ρ₂ →
           Trace {g₁ ∙ g₂} (idx₁ Fin.↑ˡ Graph.size g₂) (idx₂ Fin.↑ˡ Graph.size g₂) ρ₁ ρ₂
Trace-∙ˡ {g₁} {g₂} {idx₁} {idx₁} (Trace-single ρ₁⇒ρ₂)
    rewrite sym (lookup-++ˡ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-single ρ₁⇒ρ₂
Trace-∙ˡ {g₁} {g₂} {idx₁} (Trace-edge ρ₁⇒ρ idx₁→idx tr')
    rewrite sym (lookup-++ˡ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-edge ρ₁⇒ρ (ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (_↑ˡ Graph.size g₂) idx₁→idx))
                    (Trace-∙ˡ tr')

Trace-∙ʳ : ∀ {g₁ g₂ : Graph} {idx₁ idx₂ : Graph.Index g₂} {ρ₁ ρ₂ : Env} →
           Trace {g₂} idx₁ idx₂ ρ₁ ρ₂ →
           Trace {g₁ ∙ g₂} (Graph.size g₁ Fin.↑ʳ idx₁) (Graph.size g₁ Fin.↑ʳ idx₂) ρ₁ ρ₂
Trace-∙ʳ {g₁} {g₂} {idx₁} {idx₁} (Trace-single ρ₁⇒ρ₂)
    rewrite sym (lookup-++ʳ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-single ρ₁⇒ρ₂
Trace-∙ʳ {g₁} {g₂} {idx₁} (Trace-edge ρ₁⇒ρ idx₁→idx tr')
    rewrite sym (lookup-++ʳ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-edge ρ₁⇒ρ (ListMemProp.∈-++⁺ʳ _ (x∈xs⇒fx∈fxs (Graph.size g₁ ↑ʳ_) idx₁→idx))
                    (Trace-∙ʳ tr')

EndToEndTrace-∙ˡ : ∀ {g₁ g₂ : Graph} {ρ₁ ρ₂ : Env} →
                   EndToEndTrace {g₁} ρ₁ ρ₂ →
                   EndToEndTrace {g₁ ∙ g₂} ρ₁ ρ₂
EndToEndTrace-∙ˡ {g₁} {g₂} etr = record
    { idx₁ = EndToEndTrace.idx₁ etr Fin.↑ˡ Graph.size g₂
    ; idx₁∈inputs = ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (Fin._↑ˡ Graph.size g₂)
                                                    (EndToEndTrace.idx₁∈inputs etr))
    ; idx₂ = EndToEndTrace.idx₂ etr Fin.↑ˡ Graph.size g₂
    ; idx₂∈outputs = ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (Fin._↑ˡ Graph.size g₂)
                                                    (EndToEndTrace.idx₂∈outputs etr))
    ; trace = Trace-∙ˡ (EndToEndTrace.trace etr)
    }

EndToEndTrace-∙ʳ : ∀ {g₁ g₂ : Graph} {ρ₁ ρ₂ : Env} →
           EndToEndTrace {g₂} ρ₁ ρ₂ →
           EndToEndTrace {g₁ ∙ g₂} ρ₁ ρ₂
EndToEndTrace-∙ʳ {g₁} {g₂} etr = record
    { idx₁ = Graph.size g₁ Fin.↑ʳ EndToEndTrace.idx₁ etr
    ; idx₁∈inputs = ListMemProp.∈-++⁺ʳ (Graph.inputs g₁ ↑ˡⁱ Graph.size g₂)
                                       ((x∈xs⇒fx∈fxs (Graph.size g₁ Fin.↑ʳ_)
                                                     (EndToEndTrace.idx₁∈inputs etr)))
    ; idx₂ = Graph.size g₁ Fin.↑ʳ EndToEndTrace.idx₂ etr
    ; idx₂∈outputs = ListMemProp.∈-++⁺ʳ (Graph.outputs g₁ ↑ˡⁱ Graph.size g₂)
                                        ((x∈xs⇒fx∈fxs (Graph.size g₁ Fin.↑ʳ_)
                                                      (EndToEndTrace.idx₂∈outputs etr)))

    ; trace = Trace-∙ʳ (EndToEndTrace.trace etr)
    }

Trace-↦ˡ : ∀ {g₁ g₂ : Graph} {idx₁ idx₂ : Graph.Index g₁} {ρ₁ ρ₂ : Env} →
           Trace {g₁} idx₁ idx₂ ρ₁ ρ₂ →
           Trace {g₁ ↦ g₂} (idx₁ Fin.↑ˡ Graph.size g₂) (idx₂ Fin.↑ˡ Graph.size g₂) ρ₁ ρ₂
Trace-↦ˡ {g₁} {g₂} {idx₁} {idx₁} (Trace-single ρ₁⇒ρ₂)
    rewrite sym (lookup-++ˡ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-single ρ₁⇒ρ₂
Trace-↦ˡ {g₁} {g₂} {idx₁} (Trace-edge ρ₁⇒ρ idx₁→idx tr')
    rewrite sym (lookup-++ˡ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-edge ρ₁⇒ρ (ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (_↑ˡ Graph.size g₂) idx₁→idx))
                    (Trace-↦ˡ tr')

Trace-↦ʳ : ∀ {g₁ g₂ : Graph} {idx₁ idx₂ : Graph.Index g₂} {ρ₁ ρ₂ : Env} →
           Trace {g₂} idx₁ idx₂ ρ₁ ρ₂ →
           Trace {g₁ ↦ g₂} (Graph.size g₁ Fin.↑ʳ idx₁) (Graph.size g₁ Fin.↑ʳ idx₂) ρ₁ ρ₂
Trace-↦ʳ {g₁} {g₂} {idx₁} {idx₁} (Trace-single ρ₁⇒ρ₂)
    rewrite sym (lookup-++ʳ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-single ρ₁⇒ρ₂
Trace-↦ʳ {g₁} {g₂} {idx₁} (Trace-edge ρ₁⇒ρ idx₁→idx tr')
    rewrite sym (lookup-++ʳ (Graph.nodes g₁) (Graph.nodes g₂) idx₁) =
    Trace-edge ρ₁⇒ρ (ListMemProp.∈-++⁺ʳ (Graph.edges g₁ ↑ˡᵉ Graph.size g₂)
                                        (ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (Graph.size g₁ ↑ʳ_) idx₁→idx)))
                    (Trace-↦ʳ {g₁} {g₂} tr')

loop-edge-groups : ∀ (g : Graph) → List (List (Graph.Edge (loop g)))
loop-edge-groups g =
    (2 ↑ʳᵉ Graph.edges g) ∷
    (List.map (zero ,_) (2 ↑ʳⁱ Graph.inputs g)) ∷
    (List.map (_, suc zero) (2 ↑ʳⁱ Graph.outputs g)) ∷
    ((suc zero , zero) ∷ (zero , suc zero) ∷ []) ∷
    []

loop-edge-help : ∀ (g : Graph) {l : List (Graph.Edge (loop g))} {e : Graph.Edge (loop g)} →
                 e ListMem.∈ l → l ListMem.∈ loop-edge-groups g →
                 e ListMem.∈ Graph.edges (loop g)
loop-edge-help g e∈l l∈ess = concat-∈ e∈l l∈ess

Trace-loop : ∀ {g : Graph} {idx₁ idx₂ : Graph.Index g} {ρ₁ ρ₂ : Env} →
             Trace {g} idx₁ idx₂ ρ₁ ρ₂ → Trace {loop g} (2 Fin.↑ʳ idx₁) (2 Fin.↑ʳ idx₂) ρ₁ ρ₂
Trace-loop {g} {idx₁} {idx₁} (Trace-single ρ₁⇒ρ₂)
    rewrite sym (lookup-++ʳ (List.[] ∷ List.[] ∷ Vec.[]) (Graph.nodes g) idx₁) =
    Trace-single ρ₁⇒ρ₂
Trace-loop {g} {idx₁} (Trace-edge ρ₁⇒ρ idx₁→idx tr')
    rewrite sym (lookup-++ʳ (List.[] ∷ List.[] ∷ Vec.[]) (Graph.nodes g) idx₁) =
    Trace-edge ρ₁⇒ρ (ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (2 ↑ʳ_) idx₁→idx))
                    (Trace-loop {g} tr')

EndToEndTrace-loop : ∀ {g : Graph} {ρ₁ ρ₂ : Env} →
                     EndToEndTrace {g} ρ₁ ρ₂ → EndToEndTrace {loop g} ρ₁ ρ₂
EndToEndTrace-loop {g} etr =
    let
        zero→idx₁' = x∈xs⇒fx∈fxs (zero ,_)
                                 (x∈xs⇒fx∈fxs (2 Fin.↑ʳ_)
                                              (EndToEndTrace.idx₁∈inputs etr))
        zero→idx₁ = loop-edge-help g zero→idx₁' (there (here refl))
        idx₂→suc' = x∈xs⇒fx∈fxs (_, suc zero)
                               (x∈xs⇒fx∈fxs (2 Fin.↑ʳ_)
                                            (EndToEndTrace.idx₂∈outputs etr))
        idx₂→suc = loop-edge-help g idx₂→suc' (there (there (here refl)))
    in
        record
            { idx₁ = zero
            ; idx₁∈inputs = here refl
            ; idx₂ = suc zero
            ; idx₂∈outputs = here refl
            ; trace =
                Trace-single [] ++⟨ zero→idx₁ ⟩
                Trace-loop {g} (EndToEndTrace.trace etr) ++⟨ idx₂→suc ⟩
                Trace-single []
            }

EndToEndTrace-loop² : ∀ {g : Graph} {ρ₁ ρ₂ ρ₃ : Env} →
                      EndToEndTrace {loop g} ρ₁ ρ₂ →
                      EndToEndTrace {loop g} ρ₂ ρ₃ →
                      EndToEndTrace {loop g} ρ₁ ρ₃
EndToEndTrace-loop² {g} (MkEndToEndTrace zero (here refl) (suc zero) (here refl) tr₁)
                        (MkEndToEndTrace zero (here refl) (suc zero) (here refl) tr₂) =
    let
        suc→zero = loop-edge-help g (here refl)
                                    (there (there (there (here refl))))
    in
        record
            { idx₁ = zero
            ; idx₁∈inputs = here refl
            ; idx₂ = suc zero
            ; idx₂∈outputs = here refl
            ; trace = tr₁ ++⟨ suc→zero ⟩ tr₂
            }

EndToEndTrace-loop⁰ : ∀ {g : Graph} {ρ : Env} →
                      EndToEndTrace {loop g} ρ ρ
EndToEndTrace-loop⁰ {g} {ρ} =
    let
        zero→suc = loop-edge-help g (there (here refl))
                                    (there (there (there (here refl))))
    in
        record
            { idx₁ = zero
            ; idx₁∈inputs = here refl
            ; idx₂ = suc zero
            ; idx₂∈outputs = here refl
            ; trace = Trace-single [] ++⟨ zero→suc ⟩ Trace-single []
            }

infixr 5 _++_
_++_ : ∀ {g₁ g₂ : Graph} {ρ₁ ρ₂ ρ₃ : Env} →
       EndToEndTrace {g₁} ρ₁ ρ₂ → EndToEndTrace {g₂} ρ₂ ρ₃ →
       EndToEndTrace {g₁ ↦ g₂} ρ₁ ρ₃
_++_ {g₁} {g₂} etr₁ etr₂
    = record
        { idx₁ = EndToEndTrace.idx₁ etr₁ Fin.↑ˡ Graph.size g₂
        ; idx₁∈inputs = x∈xs⇒fx∈fxs (Fin._↑ˡ Graph.size g₂) (EndToEndTrace.idx₁∈inputs etr₁)
        ; idx₂ = Graph.size g₁ Fin.↑ʳ EndToEndTrace.idx₂ etr₂
        ; idx₂∈outputs = x∈xs⇒fx∈fxs (Graph.size g₁ Fin.↑ʳ_) (EndToEndTrace.idx₂∈outputs etr₂)
        ; trace =
            let
                o∈tr₁ = x∈xs⇒fx∈fxs (Fin._↑ˡ Graph.size g₂) (EndToEndTrace.idx₂∈outputs etr₁)
                i∈tr₂ = x∈xs⇒fx∈fxs (Graph.size g₁ Fin.↑ʳ_) (EndToEndTrace.idx₁∈inputs etr₂)
                oi∈es = ListMemProp.∈-++⁺ʳ (Graph.edges g₁ ↑ˡᵉ Graph.size g₂)
                                           (ListMemProp.∈-++⁺ʳ (Graph.size g₁ ↑ʳᵉ Graph.edges g₂)
                                                               (∈-cartesianProduct o∈tr₁ i∈tr₂))
            in
                (Trace-↦ˡ {g₁} {g₂} (EndToEndTrace.trace etr₁)) ++⟨ oi∈es ⟩
                (Trace-↦ʳ {g₁} {g₂} (EndToEndTrace.trace etr₂))
        }

EndToEndTrace-singleton : ∀ {bss : List BasicStmt} {ρ₁ ρ₂ : Env} →
                  ρ₁ , bss ⇒ᵇˢ ρ₂ → EndToEndTrace {singleton bss} ρ₁ ρ₂
EndToEndTrace-singleton ρ₁⇒ρ₂ = record
    { idx₁ = zero
    ; idx₁∈inputs = here refl
    ; idx₂ = zero
    ; idx₂∈outputs = here refl
    ; trace = Trace-single ρ₁⇒ρ₂
    }

EndToEndTrace-singleton[] : ∀ (ρ : Env) → EndToEndTrace {singleton []} ρ ρ
EndToEndTrace-singleton[] env = EndToEndTrace-singleton []

EndToEndTrace-wrap : ∀ {g : Graph} {ρ₁ ρ₂ : Env} →
                     EndToEndTrace {g} ρ₁ ρ₂ → EndToEndTrace {wrap g} ρ₁ ρ₂
EndToEndTrace-wrap {g} {ρ₁} {ρ₂} etr = EndToEndTrace-singleton[] ρ₁ ++ etr ++ EndToEndTrace-singleton[] ρ₂

buildCfg-sufficient : ∀ {s : Stmt} {ρ₁ ρ₂ : Env} → ρ₁ , s ⇒ˢ ρ₂ →
                      EndToEndTrace {buildCfg s} ρ₁ ρ₂
buildCfg-sufficient (⇒ˢ-⟨⟩ ρ₁ ρ₂ bs ρ₁,bs⇒ρ₂) =
    EndToEndTrace-singleton (ρ₁,bs⇒ρ₂ ∷ [])
buildCfg-sufficient (⇒ˢ-then ρ₁ ρ₂ ρ₃ s₁ s₂ ρ₁,s₁⇒ρ₂ ρ₂,s₂⇒ρ₃) =
    buildCfg-sufficient ρ₁,s₁⇒ρ₂ ++ buildCfg-sufficient ρ₂,s₂⇒ρ₃
buildCfg-sufficient (⇒ˢ-if-true ρ₁ ρ₂ _ _ s₁ s₂ _ _ ρ₁,s₁⇒ρ₂) =
    EndToEndTrace-∙ˡ (buildCfg-sufficient ρ₁,s₁⇒ρ₂)
buildCfg-sufficient (⇒ˢ-if-false ρ₁ ρ₂ _ s₁ s₂ _ ρ₁,s₂⇒ρ₂) =
    EndToEndTrace-∙ʳ {buildCfg s₁} (buildCfg-sufficient ρ₁,s₂⇒ρ₂)
buildCfg-sufficient (⇒ˢ-while-true ρ₁ ρ₂ ρ₃ _ _ s _ _ ρ₁,s⇒ρ₂ ρ₂,ws⇒ρ₃) =
    EndToEndTrace-loop² {buildCfg s}
                        (EndToEndTrace-loop {buildCfg s} (buildCfg-sufficient ρ₁,s⇒ρ₂))
                        (buildCfg-sufficient ρ₂,ws⇒ρ₃)
buildCfg-sufficient (⇒ˢ-while-false ρ _ s _) =
    EndToEndTrace-loop⁰ {buildCfg s} {ρ}