open import Level
open import Ordinals
module filter {n : Level } (O : Ordinals {n})   where

open import zf
open import logic
import OD 

open import Relation.Nullary 
open import Relation.Binary 
open import Data.Empty 
open import Relation.Binary
open import Relation.Binary.Core
open import Relation.Binary.PropositionalEquality
open import Data.Nat renaming ( zero to Zero ; suc to Suc ;  ℕ to Nat ; _⊔_ to _n⊔_ ) 
import BAlgbra 

open BAlgbra O

open inOrdinal O
open OD O
open OD.OD
open ODAxiom odAxiom

import ODC

open _∧_
open _∨_
open Bool

-- Kunen p.76 and p.53, we use ⊆
record Filter  ( L : HOD  ) : Set (suc n) where
   field
       filter : HOD   
       f⊆PL :  filter ⊆ Power L 
       filter1 : { p q : HOD } →  q ⊆ L  → filter ∋ p →  p ⊆ q  → filter ∋ q
       filter2 : { p q : HOD } → filter ∋ p →  filter ∋ q  → filter ∋ (p ∩ q)

open Filter

record prime-filter { L : HOD } (P : Filter L) : Set (suc (suc n)) where
   field
       proper  : ¬ (filter P ∋ od∅)
       prime   : {p q : HOD } →  filter P ∋ (p ∪ q) → ( filter P ∋ p ) ∨ ( filter P ∋ q )

record ultra-filter { L : HOD } (P : Filter L) : Set (suc (suc n)) where
   field
       proper  : ¬ (filter P ∋ od∅)
       ultra   : {p : HOD } → p ⊆ L →  ( filter P ∋ p ) ∨ (  filter P ∋ ( L ＼ p) )

open _⊆_

trans-⊆ :  { A B C : HOD} → A ⊆ B → B ⊆ C → A ⊆ C
trans-⊆ A⊆B B⊆C = record { incl = λ x → incl B⊆C (incl A⊆B x) }

power→⊆ :  ( A t : HOD) → Power A ∋ t → t ⊆ A
power→⊆ A t  PA∋t = record { incl = λ {x} t∋x → ODC.double-neg-eilm O (t1 t∋x) } where
   t1 : {x : HOD }  → t ∋ x → ¬ ¬ (A ∋ x)
   t1 = zf.IsZF.power→ isZF A t PA∋t

∈-filter : {L p : HOD} → (P : Filter L ) → filter P ∋ p → p ⊆ L
∈-filter {L} {p} P lt = power→⊆ L p ( incl (f⊆PL P) lt )

∪-lemma1 : {L p q : HOD } → (p ∪ q)  ⊆ L → p ⊆ L
∪-lemma1 {L} {p} {q} lt = record { incl = λ {x} p∋x → incl lt (case1 p∋x) }

∪-lemma2 : {L p q : HOD } → (p ∪ q)  ⊆ L → q ⊆ L
∪-lemma2 {L} {p} {q} lt = record { incl = λ {x} p∋x → incl lt (case2 p∋x) }

q∩q⊆q : {p q : HOD } → (q ∩ p) ⊆ q 
q∩q⊆q = record { incl = λ lt → proj1 lt } 

open HOD
_=h=_ : (x y : HOD) → Set n
x =h= y  = od x == od y

-----
--
--  ultra filter is prime
--

filter-lemma1 :  {L : HOD} → (P : Filter L)  → ∀ {p q : HOD } → ultra-filter P  → prime-filter P 
filter-lemma1 {L} P u = record {
         proper = ultra-filter.proper u
       ; prime = lemma3
    } where
  lemma3 : {p q : HOD} → filter P ∋ (p ∪ q) → ( filter P ∋ p ) ∨ ( filter P ∋ q )
  lemma3 {p} {q} lt with ultra-filter.ultra u (∪-lemma1 (∈-filter P lt) )
  ... | case1 p∈P  = case1 p∈P
  ... | case2 ¬p∈P = case2 (filter1 P {q ∩ (L ＼ p)} (∪-lemma2 (∈-filter P lt)) lemma7 lemma8) where
    lemma5 : ((p ∪ q ) ∩ (L ＼ p)) =h=  (q ∩ (L ＼ p))
    lemma5 = record { eq→ = λ {x} lt → record { proj1 = lemma4 x lt ; proj2 = proj2 lt  }
       ;  eq← = λ {x} lt → record { proj1 = case2 (proj1 lt) ; proj2 = proj2 lt }
      } where
         lemma4 : (x : Ordinal ) → odef ((p ∪ q) ∩ (L ＼ p)) x → odef q x
         lemma4 x lt with proj1 lt
         lemma4 x lt | case1 px = ⊥-elim ( proj2 (proj2 lt) px )
         lemma4 x lt | case2 qx = qx
    lemma6 : filter P ∋ ((p ∪ q ) ∩ (L ＼ p))
    lemma6 = filter2 P lt ¬p∈P
    lemma7 : filter P ∋ (q ∩ (L ＼ p))
    lemma7 =  subst (λ k → filter P ∋ k ) (==→o≡ lemma5 ) lemma6
    lemma8 : (q ∩ (L ＼ p)) ⊆ q
    lemma8 = q∩q⊆q

-----
--
--  if Filter contains L, prime filter is ultra
--

filter-lemma2 :  {L : HOD} → (P : Filter L)  → filter P ∋ L → prime-filter P → ultra-filter P
filter-lemma2 {L} P f∋L prime = record {
         proper = prime-filter.proper prime
       ; ultra = λ {p}  p⊆L → prime-filter.prime prime (lemma p  p⊆L)
   } where
        open _==_
        p+1-p=1 : {p : HOD} → p ⊆ L → L =h= (p ∪ (L ＼ p)) 
        eq→ (p+1-p=1 {p} p⊆L) {x} lt with ODC.decp O (odef p x)
        eq→ (p+1-p=1 {p} p⊆L) {x} lt | yes p∋x = case1 p∋x
        eq→ (p+1-p=1 {p} p⊆L) {x} lt | no ¬p = case2 (record { proj1 = lt ; proj2 = ¬p })
        eq← (p+1-p=1 {p} p⊆L) {x} ( case1 p∋x ) = subst (λ k → odef L k ) diso (incl p⊆L ( subst (λ k → odef p k) (sym diso) p∋x  )) 
        eq← (p+1-p=1 {p} p⊆L) {x} ( case2 ¬p  ) = proj1 ¬p
        lemma : (p : HOD) → p ⊆ L   →  filter P ∋ (p ∪ (L ＼ p))
        lemma p p⊆L = subst (λ k → filter P ∋ k ) (==→o≡ (p+1-p=1 p⊆L)) f∋L

record Dense  (P : HOD ) : Set (suc n) where
   field
       dense : HOD
       incl :  dense ⊆ P 
       dense-f : HOD → HOD
       dense-d :  { p : HOD} → P ∋ p  → dense ∋ dense-f p  
       dense-p :  { p : HOD} → P ∋ p  →  p ⊆ (dense-f p) 

record Ideal  ( L : HOD  ) : Set (suc n) where
   field
       ideal : HOD   
       i⊆PL :  ideal ⊆ Power L 
       ideal1 : { p q : HOD } →  q ⊆ L  → ideal ∋ p →  q ⊆ p  → ideal ∋ q
       ideal2 : { p q : HOD } → ideal ∋ p →  ideal ∋ q  → ideal ∋ (p ∪ q)

open Ideal

proper-ideal : {L : HOD} → (P : Ideal L ) → {p : HOD} → Set n
proper-ideal {L} P {p} = ideal P ∋ od∅

prime-ideal : {L : HOD} → Ideal L → ∀ {p q : HOD } → Set n
prime-ideal {L} P {p} {q} =  ideal P ∋ ( p ∩ q) → ( ideal P ∋ p ) ∨ ( ideal P ∋ q )

-------
--    the set of finite partial functions from ω to 2
--
--

import OPair
open OPair O

ODSuc : (y : HOD) → infinite ∋ y → HOD
ODSuc y lt = Union (y , (y , y)) 

nat→ω : Nat → HOD
nat→ω Zero = od∅
nat→ω (Suc y) = Union (nat→ω y , (nat→ω y , nat→ω y)) 

postulate  -- we have proved in other module
   ω∋nat→ω : {n : Nat} → def (od infinite) (od→ord (nat→ω n))
   ω<next-o∅ : {y : Ordinal} → infinite-d y → y o< next o∅

postulate
   ho< : {x : HOD} → hod-ord< {x} -- : ({x : HOD} → od→ord x o< next (odmax x)) 

data Hω2 : ( x : Ordinal  ) → Set n where
  hφ :  Hω2 o∅
  h0 : {x : Ordinal  } → Hω2 x  →
    Hω2 (od→ord < nat→ω 0 , ord→od x >)
  h1 : {x : Ordinal  } → Hω2 x  →
    Hω2 (od→ord < nat→ω 1 , ord→od x >)
  h2 : {x : Ordinal  } → Hω2 x  →
    Hω2 (od→ord < nat→ω 2 , ord→od x >)

HODω2 :  HOD
HODω2 = record { od = record { def = λ x → Hω2 x } ; odmax = next o∅ ; <odmax = odmax0 } where
    lemma0 : {n y : Ordinal} → Hω2 y → odef infinite n  → od→ord < ord→od n , ord→od y > o< next y
    lemma0 {n} {y} hw2 inf = nexto=n {!!} 
    odmax0 : {y : Ordinal} → Hω2 y → y o< next o∅
    odmax0 {o∅} hφ = x<nx
    odmax0 (h0 {y} lt) = next< (odmax0 lt) (subst (λ k → k o< next y ) (cong (λ k →  od→ord < k , ord→od y >) oiso )  (lemma0 lt (ω∋nat→ω {0} )))
    odmax0 (h1 {y} lt) = next< (odmax0 lt) (subst (λ k → k o< next y ) (cong (λ k →  od→ord < k , ord→od y >) oiso )  (lemma0 lt (ω∋nat→ω {1} )))
    odmax0 (h2 {y} lt) = next< (odmax0 lt) (subst (λ k → k o< next y ) (cong (λ k →  od→ord < k , ord→od y >) oiso )  (lemma0 lt (ω∋nat→ω {2} )))

-- the set of finite partial functions from ω to 2

data Two : Set n where
   i0 : Two
   i1 : Two

Hω2f : Set (suc n)
Hω2f = (Nat → Set n) → Two

Hω2f→Hω2 : Hω2f  → HOD
Hω2f→Hω2 p = record { od = record { def = λ x → (p {!!} ≡ i0 ) ∨ (p {!!} ≡ i1 )}; odmax = {!!} ; <odmax = {!!} }