{-# OPTIONS --guardedness --safe #-}

module Cubical.Codata.M.helper where

open import Cubical.Foundations.Prelude
open import Cubical.Foundations.Equiv using (_≃_)
open import Cubical.Foundations.Function using (_∘_)

open import Cubical.Data.Unit
open import Cubical.Data.Prod
open import Cubical.Data.Nat as ℕ using (ℕ ; suc ; _+_ )
open import Cubical.Data.Sigma hiding (_×_)

open import Cubical.Foundations.Transport
open import Cubical.Foundations.Univalence
open import Cubical.Foundations.Isomorphism
open import Cubical.Foundations.Function
open import Cubical.Foundations.Equiv
open import Cubical.Foundations.GroupoidLaws
open import Cubical.Foundations.Path

open import Cubical.Functions.Embedding
open import Cubical.Functions.FunExtEquiv

open Iso

-- General

iso→fun-Injection :
  ∀ {ℓ} {A B C : Type ℓ} (isom : Iso A B)
  → ∀ {f g : C -> A}
  → (x : C) → (Iso.fun isom (f x) ≡ Iso.fun isom (g x)) ≡ (f x ≡ g x)
iso→fun-Injection {A = A} {B} {C} isom {f = f} {g} =
  isEmbedding→Injection {A = A} {B} {C} (Iso.fun isom) (iso→isEmbedding {A = A} {B} isom) {f = f} {g = g}

abstract
  iso→Pi-fun-Injection :
    ∀ {ℓ} {A B C : Type ℓ} (isom : Iso A B)
    → ∀ {f g : C -> A}
    → Iso (∀ x → (fun isom) (f x) ≡ (fun isom) (g x)) (∀ x → f x ≡ g x)
  iso→Pi-fun-Injection {A = A} {B} {C} isom {f = f} {g} =
    pathToIso (cong (λ k → ∀ x → k x) (funExt (iso→fun-Injection isom {f = f} {g = g})))

iso→fun-Injection-Iso :
  ∀ {ℓ} {A B C : Type ℓ} (isom : Iso A B)
  → ∀ {f g : C -> A}
  → Iso (fun isom ∘ f ≡ fun isom ∘ g) (f ≡ g)
iso→fun-Injection-Iso {A = A} {B} {C} isom {f = f} {g} =
  (fun isom) ∘ f ≡ (fun isom) ∘ g
    Iso⟨ invIso funExtIso ⟩
  (∀ x → (fun isom) (f x) ≡ (fun isom) (g x))
     Iso⟨ iso→Pi-fun-Injection isom ⟩
  (∀ x → f x ≡ g x)
     Iso⟨ funExtIso ⟩
  f ≡ g ∎Iso

iso→fun-Injection-Path :
  ∀ {ℓ} {A B C : Type ℓ} (isom : Iso A B)
  → ∀ {f g : C -> A}
  → (fun isom ∘ f ≡ fun isom ∘ g) ≡ (f ≡ g)
iso→fun-Injection-Path {A = A} {B} {C} isom {f = f} {g} =
  isoToPath (iso→fun-Injection-Iso isom)

iso→inv-Injection-Path :
  ∀ {ℓ} {A B C : Type ℓ} (isom : Iso A B) →
  ∀ {f g : C -> B} →
  -----------------------
  ((inv isom) ∘ f ≡ (inv isom) ∘ g) ≡ (f ≡ g)
iso→inv-Injection-Path {A = A} {B} {C} isom {f = f} {g} = iso→fun-Injection-Path (invIso isom)

iso→fun-Injection-Iso-x :
    ∀ {ℓ} {A B : Type ℓ}
    → (isom : Iso A B)
    → ∀ {x y : A}
    → Iso ((fun isom) x ≡ (fun isom) y) (x ≡ y)
iso→fun-Injection-Iso-x isom {x} {y} =
    let tempx = λ {(lift tt) → x}
        tempy = λ {(lift tt) → y} in
    fun isom x ≡ fun isom y
      Iso⟨ iso (λ x₁ t → x₁)
               (λ x₁ → x₁ (lift tt))
               (λ x → refl)
               (λ x → refl) ⟩
    (∀ (t : Lift Unit) -> (((fun isom) ∘ tempx) t ≡ ((fun isom) ∘ tempy) t))
      Iso⟨ iso→Pi-fun-Injection isom ⟩
    (∀ (t : Lift Unit) -> tempx t ≡ tempy t)
      Iso⟨ iso (λ x₁ → x₁ (lift tt))
               (λ x₁ t → x₁)
               (λ x → refl)
               (λ x → refl) ⟩
    x ≡ y ∎Iso

iso→inv-Injection-Iso-x :
  ∀ {ℓ} {A B : Type ℓ}
  → (isom : Iso A B)
  → ∀ {x y : B}
  → Iso ((inv isom) x ≡ (inv isom) y) (x ≡ y)
iso→inv-Injection-Iso-x {A = A} {B = B} isom =
  iso→fun-Injection-Iso-x {A = B} {B = A} (invIso isom)

iso→fun-Injection-Path-x :
  ∀ {ℓ} {A B : Type ℓ}
  → (isom : Iso A B)
  → ∀ {x y : A}
  → ((fun isom) x ≡ (fun isom) y) ≡ (x ≡ y)
iso→fun-Injection-Path-x isom {x} {y} =
  isoToPath (iso→fun-Injection-Iso-x isom)

iso→inv-Injection-Path-x :
  ∀ {ℓ} {A B : Type ℓ}
  → (isom : Iso A B)
  → ∀ {x y : B}
  → ((inv isom) x ≡ (inv isom) y) ≡ (x ≡ y)
iso→inv-Injection-Path-x isom =
  isoToPath (iso→inv-Injection-Iso-x isom)