import OAI.Analysis.CharacterCriterion.Definitions
import OAI.Analysis.CharacterCriterion.Projectionless

namespace OAI

noncomputable section
open scoped TensorProduct
open scoped InnerProductSpace
open scoped BigOperators
open Set Module
open Topology
open NormedSpace
open scoped ComplexOrder
open scoped ComplexOrder
open scoped InnerProductSpace
open scoped InnerProductSpace
open NormedSpace
open scoped TensorProduct InnerProductSpace
open UniformSpace
variable [KirchbergRordam.GenericRW.Size]
local notation "rankNum" => KirchbergRordam.GenericRW.Size.n
variable [KirchbergRordam.GenericRW.PauliData]
omit [KirchbergRordam.GenericRW.Size] [KirchbergRordam.GenericRW.PauliData]
open Filter Topology BoundedContinuousFunction
open Filter Topology
open Topology
open scoped TensorProduct CStarAlgebra
open scoped CStarAlgebra ComplexOrder
open NormedSpace
open scoped ComplexOrder
open scoped ComplexOrder
open scoped InnerProductSpace
open scoped CStarAlgebra ComplexOrder
open scoped TensorProduct InnerProductSpace
open UniformSpace

namespace KirchbergRordam.PrimeDropPresentation
open scoped CStarAlgebra ComplexOrder
variable (S : PrimeDropPresentation)
lemma size_two (n : ℕ) : 2≤S.size n := by
  rw [S.size_power]
  exact Nat.le_self_pow (by omega) 2
instance (n : ℕ) : NeZero (S.size n) := ⟨by have := S.size_two n; omega⟩
instance (n : ℕ) : Nontrivial (S.Stage n) := inferInstanceAs
  (Nontrivial (PrimeDimensionDrop.Algebra (S.size n) (S.size n+1)))
instance (n : ℕ) : TopologicalSpace.SeparableSpace (S.Stage n) := inferInstanceAs
  (TopologicalSpace.SeparableSpace (PrimeDimensionDrop.Algebra (S.size n) (S.size n+1)))
lemma stage_step_norm (S : PrimeDropPresentation) :
    ∀ stage (element : S.Stage stage),
      ‖GeneralDropSystem.step (S.stepData stage) element‖ = ‖element‖ :=
  fun stage element => GeneralDropSystem.step_norm (S.stepData stage) element

instance (n : ℕ) : Nontrivial (S.system.obj n) := inferInstanceAs (Nontrivial (S.Stage n))
instance (n : ℕ) : TopologicalSpace.SeparableSpace (S.system.obj n) :=
  inferInstanceAs (TopologicalSpace.SeparableSpace (S.Stage n))
def Algebra : Type := CStarInductiveLimit.Algebra S.system
instance : CStarAlgebra S.Algebra := inferInstanceAs (CStarAlgebra (CStarInductiveLimit.Algebra S.system))
instance : Nontrivial S.Algebra := inferInstanceAs (Nontrivial (CStarInductiveLimit.Algebra S.system))
instance : TopologicalSpace.SeparableSpace S.Algebra := inferInstanceAs (TopologicalSpace.SeparableSpace (CStarInductiveLimit.Algebra S.system))
def inclusion (n : ℕ) : S.Stage n →⋆ₐ[ℂ] S.Algebra := CStarInductiveLimit.of S.system n
lemma norm_inclusion (n : ℕ) (x : S.Stage n) : ‖S.inclusion n x‖=‖x‖ :=
  CStarInductiveLimit.norm_of S.system n x
lemma inclusion_isometry (n : ℕ) : Isometry (S.inclusion n) := CStarInductiveLimit.of_isometry _ _
lemma inclusion_map (i j : ℕ) (hij : i≤j) (x : S.Stage i) :
    S.inclusion j (S.chain.map i j hij x)=S.inclusion i x := CStarInductiveLimit.of_map _ _ _ _ _
lemma inclusion_step (n : ℕ) (x : S.Stage n) :
    S.inclusion (n+1) (GeneralDropSystem.step (S.stepData n) x)=S.inclusion n x := by
  have h := S.inclusion_map n (n+1) (Nat.le_succ n) x
  rw [S.chain.map_succ n n le_rfl,S.chain.map_self] at h
  exact h
lemma denseRange_inclusion : DenseRange (fun x : Σ n, S.Stage n => S.inclusion x.1 x.2) :=
  CStarInductiveLimit.denseRange_of _
theorem stage_to_central (A : Type*) [CStarAlgebra A] [Nontrivial A]
    [TopologicalSpace.SeparableSpace A] (ω : Ultrafilter ℕ) (hω : (ω : Filter ℕ)≤Filter.cofinite)
    (hF : IsEmpty (NormUltrapower.CentralAlgebra A ω →⋆ₐ[ℂ] ℂ)) (n : ℕ) :
    Nonempty (S.Stage n →⋆ₐ[ℂ] NormUltrapower.CentralAlgebra A ω) := by
  have aux (p : ℕ) [NeZero p] (he : p=2^(S.exponent n+1)) :
      Nonempty (PrimeDimensionDrop.Algebra p (p+1) →⋆ₐ[ℂ] NormUltrapower.CentralAlgebra A ω) := by
    subst p
    exact central_prime_power_drop A ω hω hF (S.exponent n)
  exact aux (S.size n) (S.size_power n)
theorem to_central (A : Type*) [CStarAlgebra A] [Nontrivial A]
    [TopologicalSpace.SeparableSpace A] (ω : Ultrafilter ℕ) (hω : (ω : Filter ℕ)≤Filter.cofinite)
    (hF : IsEmpty (NormUltrapower.CentralAlgebra A ω →⋆ₐ[ℂ] ℂ)) :
    Nonempty (S.Algebra →⋆ₐ[ℂ] NormUltrapower.CentralAlgebra A ω) :=
  CStarInductiveLimit.exists_toCentral S.system ω hω (fun n => (S.stage_to_central A ω hω hF n).some)
end KirchbergRordam.PrimeDropPresentation
namespace KirchbergRordam.PrimeDropPresentation.Iteration
open scoped CStarAlgebra ComplexOrder
open Filter Topology
open MatrixDiagonalPath DiagonalIteration GeneralDropSystem
variable (S : PrimeDropPresentation)

abbrev diagonalSystem : DiagonalIteration.System where
  obj n := PrimeDimensionDrop.Fiber (S.size n) (S.size n+1)
  slot n := Slot (S.stepData n)
  diagonal n := (CStarMatrix.reindexₐ ℂ ℂ (zeroReindex (S.stepData n))).toStarAlgHom.comp block
  eigen n := eigenpath (S.stepData n)
  twist n := (MatrixPermutationPath.path 1
    ((zeroReindex (S.stepData n)).symm.trans (oneReindex (S.stepData n)))).toContinuousMap

lemma eigen_lipschitz : ∀ n i, LipschitzWith (1/2) ((diagonalSystem S).eigen n i) :=
  fun n i => GeneralDropSystem.eigen_lipschitz (S.stepData n) i

lemma iterate_full (n k : ℕ) (f : S.Stage n) (t : unitInterval) :
    (S.chain.map n (n+k) (Nat.le_add_right n k) f).val t =
      (diagonalSystem S).full n k f.val t := by
  induction k generalizing t with
  | zero => simp only [Nat.add_zero,S.chain.map_self,DiagonalIteration.System.full]; rfl
  | succ k ih =>
    erw [S.chain.map_succ n (n+k) (Nat.le_add_right n k)]
    change MatrixDiagonalPath.interpolate _ _ t
      (block (fun i => (S.chain.map n (n+k) _ f).val (eigenpath (S.stepData (n+k)) i t))) = _
    simp only [ih]
    rfl

def normalizedPath (n k : ℕ) (t : unitInterval) :
    unitary (PrimeDimensionDrop.Fiber (S.size (n+k)) (S.size (n+k)+1)) :=
  (diagonalSystem S).unitaryPath n k t * star ((diagonalSystem S).unitaryPath n k 0)
lemma normalizedPath_continuous (n k : ℕ) : Continuous (normalizedPath S n k) :=
  ((diagonalSystem S).unitaryPath_continuous n k).mul continuous_const
@[simp] lemma normalizedPath_zero (n k : ℕ) : normalizedPath S n k 0=1 := by
  exact mul_inv_cancel _

lemma untwist (n k : ℕ) (f : S.Stage n) (t : unitInterval) :
    conj (star (normalizedPath S n k t))
      ((S.chain.map n (n+k) (Nat.le_add_right n k) f).val t) =
      conj ((diagonalSystem S).unitaryPath n k 0) ((diagonalSystem S).flat n k f.val t) := by
  rw [iterate_full S,(diagonalSystem S).full_eq]
  exact DiagonalIteration.normalize_cancel _ _ _

lemma untwist_norm (n k : ℕ) (f : S.Stage n) (t : unitInterval) :
    ‖conj (star (normalizedPath S n k t))
      ((S.chain.map n (n+k) (Nat.le_add_right n k) f).val t)-
      (S.chain.map n (n+k) (Nat.le_add_right n k) f).val 0‖ =
      ‖(diagonalSystem S).flat n k f.val t-(diagonalSystem S).flat n k f.val 0‖ := by
  rw [untwist S,iterate_full S,(diagonalSystem S).full_eq]
  rw [←map_sub,StarAlgEquiv.norm_map]

lemma eventually_untwist_small (n : ℕ) (f : S.Stage n) (ε : ℝ) (hε : 0<ε) :
    ∀ᶠ k in atTop, ∀ t : unitInterval,
      ‖conj (star (normalizedPath S n k t))
        ((S.chain.map n (n+k) (Nat.le_add_right n k) f).val t)-
        (S.chain.map n (n+k) (Nat.le_add_right n k) f).val 0‖≤ε := by
  filter_upwards [(diagonalSystem S).flat_eventually_small (eigen_lipschitz S) n f.val ε hε] with k hk t
  rw [untwist_norm S]
  exact hk t 0
end KirchbergRordam.PrimeDropPresentation.Iteration
namespace KirchbergRordam.PrimeDropPresentation.HalfFlip
open scoped CStarAlgebra ComplexOrder
open Filter Topology
open PrimeDropPresentation.Iteration
open UnitaryDisplacement BalancedDropHalfFlip
def mappedUnitary {A B : Type} [CStarAlgebra A] [CStarAlgebra B]
    (φ : A →⋆ₐ[ℂ] B) (w : unitary (MaxTensor.Algebra A A)) :
    unitary (MaxTensor.Algebra B B) :=
  Unitary.map (StarMonoidHom.ofClass (squareMap φ)) w

lemma mappedUnitary_control {A B : Type} [CStarAlgebra A] [CStarAlgebra B]
    (φ : A →⋆ₐ[ℂ] B) (w : unitary (MaxTensor.Algebra A A)) (a : A) :
    ‖conj (mappedUnitary φ w) (MaxTensor.includeLeft (φ a))-MaxTensor.includeRight (φ a)‖≤
      ‖conj w (MaxTensor.includeLeft a)-MaxTensor.includeRight a‖ := by
  exact control_map φ w a
variable (S : PrimeDropPresentation)
lemma finite_stage (n : ℕ) (F : Finset (S.Stage n)) (ε : ℝ) (hε : 0<ε) :
    ∃ w : unitary (MaxTensor.Algebra S.Algebra S.Algebra), ∀ f∈F,
      ‖conj w (MaxTensor.includeLeft (S.inclusion n f))-
        MaxTensor.includeRight (S.inclusion n f)‖≤ε := by
  have he : ∀ᶠ k in atTop, ∀ f∈F, ∀ t : unitInterval,
      ‖conj (star (normalizedPath S n k t))
        ((S.chain.map n (n+k) (Nat.le_add_right n k) f).val t)-
        (S.chain.map n (n+k) (Nat.le_add_right n k) f).val 0‖≤ε/4 := by
    apply (Filter.eventually_all_finset F).mpr
    intro f hf
    exact eventually_untwist_small S n f (ε/4) (by positivity)
  obtain ⟨k,hk⟩ := he.exists
  obtain ⟨w,hw⟩ := PrimeSquareUnitary.exists_half_flip_control (p:=S.size (n+k)) (q:=S.size (n+k)+1) (normalizedPath S n k)
    (normalizedPath_continuous S n k) (normalizedPath_zero S n k)
  refine ⟨mappedUnitary (S.inclusion (n+k)) w,fun f hf => ?_⟩
  have hc := (mappedUnitary_control (S.inclusion (n+k)) w (S.chain.map n (n+k) (Nat.le_add_right n k) f)).trans
    (hw _ (ε/4) (hk f hf))
  have hm : S.inclusion (n+k) (S.chain.map n (n+k) (Nat.le_add_right n k) f)=S.inclusion n f :=
    S.inclusion_map n (n+k) (Nat.le_add_right n k) f
  rw [hm] at hc
  have he : 4*(ε/4)=ε := by ring
  rwa [he] at hc

lemma common_stage (F : Finset S.Algebra) (ε : ℝ) (hε : 0<ε) :
    ∃ n : ℕ, ∃ a : S.Algebra → S.Stage n, ∀ x∈F, ‖S.inclusion n (a x)-x‖<ε :=
  CStarInductiveLimit.approximation_common_stage S.system F ε hε

lemma finite_control (F : Finset S.Algebra) (ε : ℝ) (hε : 0<ε) :
    ∃ w : unitary (MaxTensor.Algebra S.Algebra S.Algebra), ∀ x∈F,
      ‖conj w (MaxTensor.includeLeft x)-MaxTensor.includeRight x‖≤ε := by
  classical
  obtain ⟨n,a,ha⟩ := common_stage S F (ε/4) (by positivity)
  obtain ⟨w,hw⟩ := finite_stage S n (F.image a) (ε/2) (by positivity)
  refine ⟨w,fun x hx => ?_⟩
  have hb := hw (a x) (Finset.mem_image_of_mem a hx)
  have hc := FiniteHalfFlipSequence.perturbation MaxTensor.includeLeft MaxTensor.includeRight w x (S.inclusion n (a x))
  have hd := ha x hx
  rw [norm_sub_rev] at hd
  change ‖conj w (MaxTensor.includeLeft x)-MaxTensor.includeRight x‖≤
    2*‖x-S.inclusion n (a x)‖+‖conj w (MaxTensor.includeLeft (S.inclusion n (a x)))-MaxTensor.includeRight (S.inclusion n (a x))‖ at hc
  linarith


theorem exists_half_flip : ∃ w : ℕ → unitary (MaxTensor.Algebra S.Algebra S.Algebra),
    ∀ x : S.Algebra, Tendsto (fun n => conj (w n) (MaxTensor.includeLeft x)) atTop
      (𝓝 (MaxTensor.includeRight x)) :=
  FiniteHalfFlipSequence.exists_sequence MaxTensor.includeLeft MaxTensor.includeRight (finite_control S)
end KirchbergRordam.PrimeDropPresentation.HalfFlip
namespace KirchbergRordam.PrimeDropPresentation.Channels
open MatrixDiagonalPath MatrixBlockReindex DiagonalIteration GeneralEndpointMultiplicity
open DropMatrixRepresentations DropChannels GeneralDropSystem
open BalancedDropSystem (half)
open scoped CStarAlgebra ComplexOrder
variable (S : PrimeDropPresentation)
lemma zeroCount (n : ℕ) :
    2≤Fintype.card (Fin (S.stepData n).zeroEnd ⊕ (Fin (S.size n+1)×Fin (S.stepData n).zeroMid)) := by
  simpa only [Fintype.card_sum,Fintype.card_prod,Fintype.card_fin] using S.zero_copies n
lemma oneCount (n : ℕ) :
    2≤Fintype.card (Fin (S.stepData n).oneEnd ⊕ (Fin (S.size n)×Fin (S.stepData n).oneMid)) := by
  simpa only [Fintype.card_sum,Fintype.card_prod,Fintype.card_fin] using S.one_copies n
lemma block_const_left {P E : Type*} [Fintype P] [Fintype E] [DecidableEq P] [DecidableEq E]
    (a : Mat P) : block (fun _ : E => a)=MatrixTensor.leftMatrix (κ:=E) a := by
  ext ⟨i,k⟩ ⟨j,l⟩
  change (if k=l then a i j else 0)=a i j*(if k=l then 1 else 0)
  split <;> simp_all

def zeroRep (n : ℕ) (v : unitary (PrimeDimensionDrop.Fiber (S.size n) (S.size n+1))) :
    DimensionDrop23 →⋆ₐ[ℂ] Mat (Fin (S.size (n+1))) :=
  (CStarMatrix.reindexₐ ℂ ℂ (zeroOuter (S.stepData n))).toStarAlgHom.comp
    (leftRep (P:=Fin (S.size n)) (Q:=Fin (S.size n+1)) (R:=Fin (S.stepData n).zeroMid)
      (E:=Fin (S.stepData n).zeroEnd) (zeroCount S n) v)
def oneRep (n : ℕ) (v : unitary (PrimeDimensionDrop.Fiber (S.size n) (S.size n+1))) :
    DimensionDrop23 →⋆ₐ[ℂ] Mat (Fin (S.size (n+1)+1)) :=
  (CStarMatrix.reindexₐ ℂ ℂ (oneOuter (S.stepData n))).toStarAlgHom.comp
    (rightRep (P:=Fin (S.size n)) (Q:=Fin (S.size n+1)) (R:=Fin (S.stepData n).oneMid)
      (E:=Fin (S.stepData n).oneEnd) (oneCount S n) v)
lemma zeroRep_bound (n : ℕ)
    (v : unitary (PrimeDimensionDrop.Fiber (S.size n) (S.size n+1)))
    (f : S.Stage n) (d : DimensionDrop23) {ε : ℝ}
    (hf : ‖conj (star v) (f.val half)-f.val 0‖≤ε) :
    ‖MatrixTensor.leftMatrix (κ:=Fin (S.size (n+1)+1)) (zeroRep S n v d)*(step (S.stepData n) f).val 0-
      (step (S.stepData n) f).val 0*MatrixTensor.leftMatrix (κ:=Fin (S.size (n+1)+1)) (zeroRep S n v d)‖≤2*ε*‖d‖ := by
  have he := rawStep_zero (S.stepData n) f.val _ (leftValue_spec (S.size n) (S.size n+1) f)
  change (step (S.stepData n) f).val 0=_ at he
  rw [block_const_left] at he
  rw [he]
  let φ := (MatrixTensor.leftMatrix (κ:=Fin (S.size (n+1)+1))).comp
    (CStarMatrix.reindexₐ ℂ ℂ (zeroOuter (S.stepData n))).toStarAlgHom
  apply (commutator_map_bound φ _ _).trans
  apply leftRep_bound (zeroCount S n)
  erw [leftValue_spec (S.size n) (S.size n+1) f]
  rw [norm_sub_conj]
  exact hf
lemma oneRep_bound (n : ℕ)
    (v : unitary (PrimeDimensionDrop.Fiber (S.size n) (S.size n+1)))
    (f : S.Stage n) (d : DimensionDrop23) {ε : ℝ}
    (hf : ‖conj (star v) (f.val half)-f.val 1‖≤ε) :
    ‖MatrixTensor.rightMatrix (ι:=Fin (S.size (n+1))) (oneRep S n v d)*(step (S.stepData n) f).val 1-
      (step (S.stepData n) f).val 1*MatrixTensor.rightMatrix (ι:=Fin (S.size (n+1))) (oneRep S n v d)‖≤2*ε*‖d‖ := by
  have he := rawStep_one (S.stepData n) f.val _ (rightValue_spec (S.size n) (S.size n+1) f)
  change (step (S.stepData n) f).val 1=_ at he
  rw [block_const_left] at he
  rw [he]
  let φ := (MatrixTensor.rightMatrix (ι:=Fin (S.size (n+1)))).comp
    (CStarMatrix.reindexₐ ℂ ℂ (oneOuter (S.stepData n))).toStarAlgHom
  apply (commutator_map_bound φ _ _).trans
  apply rightRep_bound (oneCount S n)
  erw [rightValue_spec (S.size n) (S.size n+1) f]
  rw [norm_sub_conj]
  exact hf
end KirchbergRordam.PrimeDropPresentation.Channels
end

end OAI