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.List as List using (List; _∷_; [])
open import Data.List.Relation.Unary.Any using (here; there)
open import Data.List.Membership.Propositional.Properties as ListMemProp using ()
open import Data.Product using (Σ; _,_; _×_)
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)

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


buildCfg-input : ∀ (s : Stmt) → let g = buildCfg s in Σ (Graph.Index g) (λ idx → Graph.inputs g ≡ idx ∷ [])
buildCfg-input ⟨ bs₁ ⟩ = (zero , refl)
buildCfg-input (s₁ then s₂)
    with (idx , p) ← buildCfg-input s₁ rewrite p = (_ , refl)
buildCfg-input (if _ then s₁ else s₂) = (zero , refl)
buildCfg-input (while _ repeat s)
    with (idx , p) ← buildCfg-input s rewrite p = (_ , refl)

buildCfg-output : ∀ (s : Stmt) → let g = buildCfg s in Σ (Graph.Index g) (λ idx → Graph.outputs g ≡ idx ∷ [])
buildCfg-output ⟨ bs₁ ⟩ = (zero , refl)
buildCfg-output (s₁ then s₂)
    with (idx , p) ← buildCfg-output s₂ rewrite p = (_ , refl)
buildCfg-output (if _ then s₁ else s₂) = (_ , refl)
buildCfg-output (while _ repeat s)
    with (idx , p) ← buildCfg-output s rewrite p = (_ , 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')

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 = ListMemProp.∈-++⁺ʳ (2 ↑ʳᵉ Graph.edges g) (ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (zero ,_) (x∈xs⇒fx∈fxs (2 Fin.↑ʳ_) (EndToEndTrace.idx₁∈inputs etr))))
        idx₂→suc = ListMemProp.∈-++⁺ʳ (2 ↑ʳᵉ Graph.edges g) (ListMemProp.∈-++⁺ʳ (List.map (zero ,_) (2 ↑ʳⁱ Graph.inputs g)) (ListMemProp.∈-++⁺ˡ (x∈xs⇒fx∈fxs (_, suc zero) (x∈xs⇒fx∈fxs (2 Fin.↑ʳ_) (EndToEndTrace.idx₂∈outputs etr)))))
    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 = ListMemProp.∈-++⁺ʳ (2 ↑ʳᵉ Graph.edges g) (ListMemProp.∈-++⁺ʳ (List.map (zero ,_) (2 ↑ʳⁱ Graph.inputs g)) (ListMemProp.∈-++⁺ʳ (List.map (_, suc zero) (2 ↑ʳⁱ Graph.outputs g)) (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 = ListMemProp.∈-++⁺ʳ (2 ↑ʳᵉ Graph.edges g) (ListMemProp.∈-++⁺ʳ (List.map (zero ,_) (2 ↑ʳⁱ Graph.inputs g)) (ListMemProp.∈-++⁺ʳ (List.map (_, suc zero) (2 ↑ʳⁱ Graph.outputs g)) (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 []

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-singleton[] ρ₁ ++
    (EndToEndTrace-∙ˡ (buildCfg-sufficient ρ₁,s₁⇒ρ₂)) ++
    EndToEndTrace-singleton[] ρ₂
buildCfg-sufficient (⇒ˢ-if-false ρ₁ ρ₂ _ s₁ s₂ _ ρ₁,s₂⇒ρ₂) =
    EndToEndTrace-singleton[] ρ₁ ++
    (EndToEndTrace-∙ʳ {buildCfg s₁} (buildCfg-sufficient ρ₁,s₂⇒ρ₂)) ++
    EndToEndTrace-singleton[] 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}