import OAI.Analysis.CharacterCriterion.WeightedUnits

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 [instSize : KirchbergRordam.GenericRW.Size]
local notation "rankNum" => KirchbergRordam.GenericRW.Size.n



namespace KirchbergRordam.GenericRW

open scoped Matrix Kronecker ComplexOrder

abbrev M2 := CStarMatrix (Fin rankNum) (Fin rankNum) ℂ
abbrev M3 := CStarMatrix (Fin (rankNum+1)) (Fin (rankNum+1)) ℂ
abbrev M6 := CStarMatrix (Fin rankNum × Fin (rankNum+1)) (Fin rankNum × Fin (rankNum+1)) ℂ


def leftMatrixAlgebra : Matrix (Fin rankNum) (Fin rankNum) ℂ →⋆ₐ[ℂ]
    Matrix (Fin rankNum × Fin (rankNum+1)) (Fin rankNum × Fin (rankNum+1)) ℂ where
  toFun a := a ⊗ₖ (1 : Matrix (Fin (rankNum+1)) (Fin (rankNum+1)) ℂ)
  map_zero' := Matrix.zero_kronecker _
  map_one' := Matrix.one_kronecker_one
  map_add' a b := Matrix.add_kronecker _ _ _
  map_mul' a b := by
    simpa only [mul_one] using Matrix.mul_kronecker_mul a b
      (1 : Matrix (Fin (rankNum+1)) (Fin (rankNum+1)) ℂ) (1 : Matrix (Fin (rankNum+1)) (Fin (rankNum+1)) ℂ)
  commutes' z := by
    simp only [Algebra.algebraMap_eq_smul_one, Matrix.smul_kronecker,
      Matrix.one_kronecker_one]
  map_star' a := by
    change aᴴ ⊗ₖ (1 : Matrix (Fin (rankNum+1)) (Fin (rankNum+1)) ℂ) = (a ⊗ₖ 1)ᴴ
    rw [Matrix.conjTranspose_kronecker, Matrix.conjTranspose_one]


def rightMatrixAlgebra : Matrix (Fin (rankNum+1)) (Fin (rankNum+1)) ℂ →⋆ₐ[ℂ]
    Matrix (Fin rankNum × Fin (rankNum+1)) (Fin rankNum × Fin (rankNum+1)) ℂ where
  toFun a := (1 : Matrix (Fin rankNum) (Fin rankNum) ℂ) ⊗ₖ a
  map_zero' := Matrix.kronecker_zero _
  map_one' := Matrix.one_kronecker_one
  map_add' a b := Matrix.kronecker_add _ _ _
  map_mul' a b := by
    simpa only [mul_one] using Matrix.mul_kronecker_mul
      (1 : Matrix (Fin rankNum) (Fin rankNum) ℂ) (1 : Matrix (Fin rankNum) (Fin rankNum) ℂ) a b
  commutes' z := by
    simp only [Algebra.algebraMap_eq_smul_one, Matrix.kronecker_smul,
      Matrix.one_kronecker_one]
  map_star' a := by
    change (1 : Matrix (Fin rankNum) (Fin rankNum) ℂ) ⊗ₖ aᴴ = (1 ⊗ₖ a)ᴴ
    rw [Matrix.conjTranspose_kronecker, Matrix.conjTranspose_one]


def leftMatrix : M2 →⋆ₐ[ℂ] M6 :=
  CStarMatrix.ofMatrixStarAlgEquiv.toStarAlgHom.comp
    (leftMatrixAlgebra.comp CStarMatrix.ofMatrixStarAlgEquiv.symm.toStarAlgHom)


def rightMatrix : M3 →⋆ₐ[ℂ] M6 :=
  CStarMatrix.ofMatrixStarAlgEquiv.toStarAlgHom.comp
    (rightMatrixAlgebra.comp CStarMatrix.ofMatrixStarAlgEquiv.symm.toStarAlgHom)


def matrixEval (t : unitInterval) : C(unitInterval, M6) →⋆ₐ[ℂ] M6 where
  toFun f := f t
  map_zero' := rfl
  map_one' := rfl
  map_add' _ _ := rfl
  map_mul' _ _ := rfl
  commutes' _ := rfl
  map_star' _ := rfl


def dimensionDropSubalgebra : StarSubalgebra ℂ C(unitInterval, M6) :=
  leftMatrix.range.comap (matrixEval 0) ⊓ rightMatrix.range.comap (matrixEval 1)

instance : FiniteDimensional ℂ M6 :=
  inferInstanceAs (FiniteDimensional ℂ (Matrix (Fin rankNum × Fin (rankNum+1)) (Fin rankNum × Fin (rankNum+1)) ℂ))

instance dimensionDropClosed : IsClosed
    (dimensionDropSubalgebra : Set C(unitInterval, M6)) := by
  change IsClosed ((fun f : C(unitInterval, M6) => f 0) ⁻¹' (leftMatrix.range : Set M6) ∩
    (fun f : C(unitInterval, M6) => f 1) ⁻¹' (rightMatrix.range : Set M6))
  exact ((leftMatrix.range.toSubalgebra.toSubmodule.closed_of_finiteDimensional).preimage
    (continuous_eval_const (0 : unitInterval))).inter
    ((rightMatrix.range.toSubalgebra.toSubmodule.closed_of_finiteDimensional).preimage
    (continuous_eval_const (1 : unitInterval)))


abbrev DimensionDrop23 := dimensionDropSubalgebra

instance dropSubringClass : SubringClass
    (StarSubalgebra ℂ C(unitInterval, M6)) C(unitInterval, M6) :=
  StarSubalgebra.subringClass (R := ℂ) (A := C(unitInterval, M6))

instance : CStarAlgebra DimensionDrop23 :=
  StarSubalgebra.cstarAlgebra dimensionDropSubalgebra
example : Nontrivial DimensionDrop23 := inferInstance


def dropCoordinate : DimensionDrop23 :=
  ⟨⟨fun t => ((t : ℝ) : ℂ) • (1 : M6), by fun_prop⟩,
    by
      constructor
      · change ∃ a : M2, leftMatrix a = ((0 : unitInterval) : ℝ) • (1 : M6)
        exact ⟨0, by simp⟩
      · change ∃ a : M3, rightMatrix a = ((1 : unitInterval) : ℝ) • (1 : M6)
        exact ⟨1, by simp⟩⟩


def leftCone (a : M2) : DimensionDrop23 :=
  ⟨⟨fun t => (1 - ((t : ℝ) : ℂ)) • leftMatrix a, by fun_prop⟩,
    by
      constructor
      · refine ⟨a, ?_⟩
        change leftMatrix a = (1 - (((0 : unitInterval) : ℝ) : ℂ)) • leftMatrix a
        simp
      · refine ⟨0, ?_⟩
        change rightMatrix 0 = (1 - (((1 : unitInterval) : ℝ) : ℂ)) • leftMatrix a
        simp⟩


def rightCone (a : M3) : DimensionDrop23 :=
  ⟨⟨fun t => ((t : ℝ) : ℂ) • rightMatrix a, by fun_prop⟩,
    by
      constructor
      · refine ⟨0, ?_⟩
        change leftMatrix 0 = (((0 : unitInterval) : ℝ) : ℂ) • rightMatrix a
        simp
      · refine ⟨a, ?_⟩
        change rightMatrix a = (((1 : unitInterval) : ℝ) : ℂ) • rightMatrix a
        simp⟩


def matrixUnit {n : ℕ} (i j : Fin n) : CStarMatrix (Fin n) (Fin n) ℂ :=
  CStarMatrix.ofMatrixStarAlgEquiv (Matrix.single i j 1)

@[ext]
theorem drop_ext {f g : DimensionDrop23}
    (h : ∀ t, (f : C(unitInterval, M6)) t = (g : C(unitInterval, M6)) t) : f = g := by
  apply Subtype.ext
  exact ContinuousMap.ext h

omit instSize in
@[simp]
theorem matrixUnit_mul
    [KirchbergRordam.GenericRW.Size]
    {n : ℕ} (i j k : Fin n) :
    matrixUnit i j * matrixUnit j k = matrixUnit i k := by
  unfold matrixUnit
  rw [← map_mul]
  simp only [Matrix.single_mul_single_same, mul_one]

omit instSize in
theorem matrixUnit_mul_self
    [KirchbergRordam.GenericRW.Size]
    {n : ℕ} (i j : Fin n) (h : i ≠ j) :
    matrixUnit i j * matrixUnit i j = 0 := by
  unfold matrixUnit
  rw [← map_mul, Matrix.single_mul_single_of_ne (1 : ℂ) i j i h.symm (1 : ℂ), map_zero]

theorem leftCone_mul_self (a : M2) (ha : a * a = 0) :
    leftCone a * leftCone a = 0 := by
  apply drop_ext
  intro t
  change ((1 - ((t : ℝ) : ℂ)) • leftMatrix a) *
    ((1 - ((t : ℝ) : ℂ)) • leftMatrix a) = 0
  rw [smul_mul_smul, ← map_mul, ha, map_zero, smul_zero]

theorem rightCone_mul_self (a : M3) (ha : a * a = 0) :
    rightCone a * rightCone a = 0 := by
  apply drop_ext
  intro t
  change (((t : ℝ) : ℂ) • rightMatrix a) *
    (((t : ℝ) : ℂ) • rightMatrix a) = 0
  rw [smul_mul_smul, ← map_mul, ha, map_zero, smul_zero]

end KirchbergRordam.GenericRW

namespace KirchbergRordam.GenericRW.FieldCalculus
open scoped BigOperators
variable {X : Type*} [TopologicalSpace X] [CompactSpace X] [T2Space X]
variable {ι : Type*} [Fintype ι] [DecidableEq ι]
variable {A : Type*} [CStarAlgebra A]


structure Data (X ι A : Type*) [TopologicalSpace X] [CompactSpace X] [T2Space X]
    [Fintype ι] [DecidableEq ι] [CStarAlgebra A] where
  p : C(X,ℂ)
  selfAdjoint_p : IsSelfAdjoint p
  eval : C(X,ℂ) →⋆ₐ[ℂ] A
  x : ι → ι → A
  star_x : ∀ i j, star (x i j) = x j i
  mul_x : ∀ i j k l, x i j*x k l = if j=k then eval p*x i l else 0
  commute_eval : ∀ i j f, Commute (x i j) (eval f)
  bound : ∀ i j f, ‖x i j*eval f‖ ≤ ‖p*f‖

namespace Data
variable (D : Data X ι A)
abbrev Domain := Vanish.Functions {t | D.p t=0}

def aux (i j : ι) : C(X,ℂ) →ₗ[ℂ] A where
  toFun f := D.x i j*D.eval f
  map_add' _ _ := by simp [mul_add]
  map_smul' _ _ := by simp

def coeff (i j : ι) : D.Domain →L[ℂ] A := (D.aux i j).extendOfNorm (Vanish.multiplier D.p)

lemma coeff_mul (i j : ι) (f : C(X,ℂ)) :
    D.coeff i j (Vanish.multiplier D.p f) = D.x i j*D.eval f := by
  exact LinearMap.extendOfNorm_eq (Vanish.multiplier_dense D.p)
    ⟨1,fun f => by change ‖D.x i j*D.eval f‖ ≤ 1*‖D.p*f‖; simpa only [one_mul] using D.bound i j f⟩ f

lemma norm_coeff_le (i j : ι) (f : D.Domain) : ‖D.coeff i j f‖ ≤ ‖f‖ := by
  simpa only [coeff,one_mul] using LinearMap.norm_extendOfNorm_apply_le
    (f := D.aux i j) (Vanish.multiplier_dense D.p) 1
    (fun f => by change ‖D.x i j*D.eval f‖ ≤ 1*‖D.p*f‖; simpa only [one_mul] using D.bound i j f) f

omit instSize in
lemma multiplier_star.{contextLevel1, contextLevel2, contextLevel3}
    [KirchbergRordam.GenericRW.Size]
    {X : Type contextLevel1}
    [TopologicalSpace X]
    [CompactSpace X]
    [T2Space X]
    {ι : Type contextLevel2}
    [Fintype ι]
    [DecidableEq ι]
    {A : Type contextLevel3}
    [CStarAlgebra A]
    (D : KirchbergRordam.GenericRW.FieldCalculus.Data X ι A)
    (f : C(X,ℂ)) :
    star (Vanish.multiplier D.p f) = Vanish.multiplier D.p (star f) := by
  apply Subtype.ext
  change star (D.p*f)=D.p*star f
  rw [star_mul,D.selfAdjoint_p.star_eq,mul_comm]

omit instSize in
lemma multiplier_product.{contextLevel1, contextLevel2, contextLevel3}
    [KirchbergRordam.GenericRW.Size]
    {X : Type contextLevel1}
    [TopologicalSpace X]
    [CompactSpace X]
    [T2Space X]
    {ι : Type contextLevel2}
    [Fintype ι]
    [DecidableEq ι]
    {A : Type contextLevel3}
    [CStarAlgebra A]
    (D : KirchbergRordam.GenericRW.FieldCalculus.Data X ι A)
    (f g : C(X,ℂ)) :
    Vanish.multiplier D.p f * Vanish.multiplier D.p g =
      Vanish.multiplier D.p (D.p*f*g) := by
  apply Subtype.ext
  change (D.p*f)*(D.p*g)=D.p*(D.p*f*g)
  ring

lemma star_coeff (i j : ι) (f : D.Domain) :
    star (D.coeff i j f) = D.coeff j i (star f) := by
  refine (Vanish.multiplier_dense D.p).induction_on f (isClosed_eq (by fun_prop) (by fun_prop)) ?_
  intro g
  rw [D.multiplier_star,D.coeff_mul,D.coeff_mul,star_mul,D.star_x,map_star]
  simpa only [map_star] using (D.commute_eval j i (star g)).symm.eq

lemma product_coeff (i j k l : ι) (f g : D.Domain) :
    D.coeff i j f * D.coeff k l g = if j=k then D.coeff i l (f*g) else 0 := by
  refine (Vanish.multiplier_dense D.p).induction_on₂ (p := fun f g =>
    D.coeff i j f * D.coeff k l g = if j=k then D.coeff i l (f*g) else 0)
    (isClosed_eq (by fun_prop) (by by_cases hjk : j=k <;> simp only [hjk,↓reduceIte] <;> fun_prop)) ?_ f g
  intro f g
  rw [D.multiplier_product,D.coeff_mul,D.coeff_mul,D.coeff_mul]
  have he : (D.x i j*D.eval f)*(D.x k l*D.eval g) =
      (D.x i j*D.x k l)*(D.eval f*D.eval g) := by
    rw [mul_assoc (D.x i j),← mul_assoc (D.eval f),(D.commute_eval k l f).symm.eq]
    noncomm_ring
  rw [he,D.mul_x]
  split_ifs with hjk
  · rw [map_mul,map_mul,← (D.commute_eval i l D.p).eq]
    noncomm_ring
  · simp


def scalarMul (f : C(X,ℂ)) : D.Domain →L[ℂ] D.Domain :=
  { toFun := fun g => ⟨f*(g:C(X,ℂ)), by intro t ht; simp [g.property t ht]⟩
    map_add' := by intro g h; ext t; simp [mul_add]
    map_smul' := by intro c g; ext t; simp
    cont := by fun_prop }

lemma scalar_coeff (i j : ι) (f : C(X,ℂ)) (g : D.Domain) :
    D.coeff i j (D.scalarMul f g) = D.eval f * D.coeff i j g := by
  refine (Vanish.multiplier_dense D.p).induction_on g (isClosed_eq (by fun_prop) (by fun_prop)) ?_
  intro u
  have he : D.scalarMul f (Vanish.multiplier D.p u) = Vanish.multiplier D.p (f*u) := by
    apply Subtype.ext
    change f*(D.p*u)=D.p*(f*u)
    ring
  rw [he,D.coeff_mul,D.coeff_mul,map_mul]
  rw [← mul_assoc, (D.commute_eval i j f).eq, mul_assoc]

abbrev Matrices := Matrix ι ι D.Domain

def matrices : D.Matrices →ₗ[ℂ] A where
  toFun m := ∑ i,∑ j,D.coeff i j (m i j)
  map_add' m n := by simp [Finset.sum_add_distrib]
  map_smul' c m := by simp [Finset.smul_sum]

omit instSize in
lemma matrices_single.{contextLevel1, contextLevel2, contextLevel3}
    [KirchbergRordam.GenericRW.Size]
    {X : Type contextLevel1}
    [TopologicalSpace X]
    [CompactSpace X]
    [T2Space X]
    {ι : Type contextLevel2}
    [Fintype ι]
    [DecidableEq ι]
    {A : Type contextLevel3}
    [CStarAlgebra A]
    (D : KirchbergRordam.GenericRW.FieldCalculus.Data X ι A)
    (i j : ι) (f : D.Domain) :
    D.matrices (Matrix.single i j f) = D.coeff i j f := by
  simp [matrices,Matrix.single,ite_and,apply_ite]

lemma matrices_product (m n : D.Matrices) : D.matrices (m*n) = D.matrices m*D.matrices n := by
  induction m using Matrix.induction_on' with
  | h_zero => simp
  | h_add m m' hm hm' => simp only [add_mul,map_add,hm,hm']
  | h_std_basis i j f =>
    induction n using Matrix.induction_on' with
    | h_zero => simp
    | h_add n n' hn hn' => simp only [mul_add,map_add,hn,hn']
    | h_std_basis k l g =>
      by_cases h : j=k
      · subst k
        rw [Matrix.single_mul_single_same,D.matrices_single,D.matrices_single,
          D.matrices_single,D.product_coeff,ite_eq_left rfl]
      · rw [Matrix.single_mul_single_of_ne (h := h),D.matrices_single,D.matrices_single,
          D.product_coeff,ite_eq_right h,map_zero]

lemma matrices_star (m : D.Matrices) : D.matrices (star m) = star (D.matrices m) := by
  simp only [matrices,LinearMap.coe_mk,AddHom.coe_mk,star_sum,D.star_coeff]
  exact Finset.sum_comm


def hom : D.Matrices →⋆ₙₐ[ℂ] A where
  toFun := D.matrices
  map_zero' := map_zero _
  map_add' := map_add _
  map_smul' := map_smul _
  map_mul' := D.matrices_product
  map_star' := D.matrices_star
end Data
end KirchbergRordam.GenericRW.FieldCalculus
namespace KirchbergRordam.GenericRW.OrderZero
open scoped BigOperators
open IntervalCalculus
variable {ι κ A : Type*} [Fintype ι] [DecidableEq ι] [Fintype κ] [DecidableEq κ]
variable [CStarAlgebra A] [Nontrivial A] [PartialOrder A] [StarOrderedRing A]


structure Pair (ι κ A : Type*) [Fintype ι] [DecidableEq ι] [Fintype κ] [DecidableEq κ]
    [CStarAlgebra A] [PartialOrder A] where
  left : WeightedUnits ι A
  right : WeightedUnits κ A
  commute : ∀ i j k l, Commute (left.x i j) (right.x k l)
  sum_one : left.h+right.h=1

namespace Pair
variable (P : Pair ι κ A)
omit [Nontrivial A] [StarOrderedRing A] in
omit instSize in
lemma left_h.{contextLevel1, contextLevel2, contextLevel3}
    [KirchbergRordam.GenericRW.Size]
    {ι : Type contextLevel1}
    {κ : Type contextLevel2}
    {A : Type contextLevel3}
    [Fintype ι]
    [DecidableEq ι]
    [Fintype κ]
    [DecidableEq κ]
    [CStarAlgebra A]
    [PartialOrder A]
    (P : KirchbergRordam.GenericRW.OrderZero.Pair ι κ A)
    : P.left.h=1-P.right.h := (eq_sub_iff_add_eq).mpr P.sum_one

omit [Nontrivial A] [StarOrderedRing A] in
omit instSize in
lemma left_commute_right_h.{contextLevel1, contextLevel2, contextLevel3}
    [KirchbergRordam.GenericRW.Size]
    {ι : Type contextLevel1}
    {κ : Type contextLevel2}
    {A : Type contextLevel3}
    [Fintype ι]
    [DecidableEq ι]
    [Fintype κ]
    [DecidableEq κ]
    [CStarAlgebra A]
    [PartialOrder A]
    (P : KirchbergRordam.GenericRW.OrderZero.Pair ι κ A)
    (i j : ι) : Commute (P.left.x i j) P.right.h := by
  change P.left.x i j*P.right.h=P.right.h*P.left.x i j
  rw [← P.right.diagonal,Finset.mul_sum,Finset.sum_mul]
  exact Finset.sum_congr rfl fun k _ => (P.commute i j k k).eq

omit [Nontrivial A] [StarOrderedRing A] in
lemma right_commute_left_h (i j : κ) : Commute (P.right.x i j) P.left.h := by
  rw [P.left_h]
  exact (Commute.one_right _).sub_right (P.right.commute_h i j)

abbrev eval : C(unitInterval,ℂ) →⋆ₐ[ℂ] A := IntervalCalculus.hom P.right.nonneg P.right.norm_le

lemma commute_eval {x : A} (hc : Commute x P.right.h) (f : C(unitInterval,ℂ)) :
    Commute x (P.eval f) := by
  exact ((IsSelfAdjoint.of_nonneg P.right.nonneg).commute_cfcHom
    (IsSelfAdjoint.of_nonneg P.right.nonneg).isStarNormal hc.symm _).symm

def weight (_P : Pair ι κ A) : C(unitInterval,ℂ) := (1-coord)*coord

omit [Nontrivial A] [StarOrderedRing A] in
omit instSize in
lemma selfAdjoint_weight.{contextLevel1, contextLevel2, contextLevel3}
    [KirchbergRordam.GenericRW.Size]
    {ι : Type contextLevel1}
    {κ : Type contextLevel2}
    {A : Type contextLevel3}
    [Fintype ι]
    [DecidableEq ι]
    [Fintype κ]
    [DecidableEq κ]
    [CStarAlgebra A]
    [PartialOrder A]
    (P : KirchbergRordam.GenericRW.OrderZero.Pair ι κ A)
    : IsSelfAdjoint P.weight := by
  ext t
  simp [weight,coord]

lemma eval_weight : P.eval P.weight = P.left.h*P.right.h := by
  rw [weight,map_mul,map_sub,map_one,hom_coord,P.left_h]

lemma norm_product (i j : ι) (k l : κ) (f : C(unitInterval,ℂ)) :
    ‖(P.left.x i j*P.right.x k l)*P.eval f‖ ≤ ‖P.weight*f‖ := by
  calc
    _ ≤ ‖P.left.h*(P.right.x k l*P.eval f)‖ := by
      rw [mul_assoc]
      exact P.left.norm_mul_le i j _
    _ = ‖P.right.x k l*(P.left.h*P.eval f)‖ := by
      rw [← mul_assoc,(P.right_commute_left_h k l).symm.eq,mul_assoc]
    _ ≤ ‖P.right.h*(P.left.h*P.eval f)‖ := P.right.norm_mul_le k l _
    _ = ‖P.eval (P.weight*f)‖ := by
      rw [map_mul,P.eval_weight,P.left_h]
      congr 1
      noncomm_ring
    _ ≤ ‖P.weight*f‖ := norm_hom_le _ _ _


def field : FieldCalculus.Data unitInterval (ι × κ) A where
  p := P.weight
  selfAdjoint_p := P.selfAdjoint_weight
  eval := P.eval
  x u v := P.left.x u.1 v.1*P.right.x u.2 v.2
  star_x u v := by
    rw [star_mul,P.left.star_x,P.right.star_x]
    exact (P.commute v.1 u.1 v.2 u.2).symm.eq
  mul_x u v w z := by
    have he : (P.left.x u.1 v.1*P.right.x u.2 v.2)*(P.left.x w.1 z.1*P.right.x w.2 z.2) =
        (P.left.x u.1 v.1*P.left.x w.1 z.1)*(P.right.x u.2 v.2*P.right.x w.2 z.2) := by
      rw [mul_assoc (P.left.x u.1 v.1),← mul_assoc (P.right.x u.2 v.2),
        (P.commute w.1 z.1 u.2 v.2).symm.eq]
      noncomm_ring
    rw [he,P.left.mul_x,P.right.mul_x,P.eval_weight]
    by_cases h1 : v.1=w.1 <;> by_cases h2 : v.2=w.2
    · have h : v=w := Prod.ext h1 h2
      simp only [h,↓reduceIte]
      rw [mul_assoc P.left.h,← mul_assoc (P.left.x u.1 z.1),
        (P.left_commute_right_h u.1 z.1).eq]
      noncomm_ring
    · have h : v ≠ w := fun he => h2 (congrArg Prod.snd he)
      simp [h1,h2,h]
    · have h : v ≠ w := fun he => h1 (congrArg Prod.fst he)
      simp [h1,h2,h]
    · have h : v ≠ w := fun he => h1 (congrArg Prod.fst he)
      simp [h1,h2,h]
  commute_eval u v f := P.commute_eval
    ((P.left_commute_right_h u.1 v.1).mul_left (P.right.commute_h u.2 v.2)) f
  bound u v f := P.norm_product _ _ _ _ f

lemma left_x_field (i j : ι) (u v : ι × κ) :
    P.left.x i j * P.field.x u v =
      if j=u.1 then P.left.h*P.field.x (i,u.2) v else 0 := by
  change _*(P.left.x u.1 v.1*P.right.x u.2 v.2) = _
  rw [← mul_assoc,P.left.mul_x]
  by_cases h : j=u.1 <;> simp [h,field,mul_assoc]

lemma right_x_field (i j : κ) (u v : ι × κ) :
    P.right.x i j * P.field.x u v =
      if j=u.2 then P.right.h*P.field.x (u.1,i) v else 0 := by
  change _*(P.left.x u.1 v.1*P.right.x u.2 v.2) = _
  rw [← mul_assoc,(P.commute u.1 v.1 i j).symm.eq,mul_assoc,P.right.mul_x]
  by_cases h : j=u.2
  · simp only [h,↓reduceIte]
    change P.left.x u.1 v.1*(P.right.h*P.right.x i v.2) =
      P.right.h*(P.left.x u.1 v.1*P.right.x i v.2)
    rw [← mul_assoc, (P.left_commute_right_h u.1 v.1).eq,mul_assoc]
  · simp [h]

lemma left_x_coeff (i j : ι) (u v : ι × κ) (f : P.field.Domain) :
    P.left.x i j*P.field.coeff u v f =
      if j=u.1 then P.field.coeff (i,u.2) v (P.field.scalarMul (1-coord) f) else 0 := by
  refine (Vanish.multiplier_dense P.field.p).induction_on f
    (isClosed_eq (by fun_prop) (by by_cases h : j=u.1 <;> simp only [h,↓reduceIte] <;> fun_prop)) ?_
  intro g
  rw [P.field.coeff_mul]
  rw [← mul_assoc,P.left_x_field]
  by_cases h : j=u.1
  · rw [ite_eq_left h,ite_eq_left h,P.field.scalar_coeff,P.field.coeff_mul]
    change (P.left.h*P.field.x (i,u.2) v)*P.eval g =
      P.eval (1-coord)*(P.field.x (i,u.2) v*P.eval g)
    rw [map_sub,map_one,hom_coord,← P.left_h,mul_assoc]
  · simp [h]

lemma right_x_coeff (i j : κ) (u v : ι × κ) (f : P.field.Domain) :
    P.right.x i j*P.field.coeff u v f =
      if j=u.2 then P.field.coeff (u.1,i) v (P.field.scalarMul coord f) else 0 := by
  refine (Vanish.multiplier_dense P.field.p).induction_on f
    (isClosed_eq (by fun_prop) (by by_cases h : j=u.2 <;> simp only [h,↓reduceIte] <;> fun_prop)) ?_
  intro g
  rw [P.field.coeff_mul,← mul_assoc,P.right_x_field]
  by_cases h : j=u.2
  · rw [ite_eq_left h,ite_eq_left h,P.field.scalar_coeff,P.field.coeff_mul]
    change (P.right.h*P.field.x (u.1,i) v)*P.eval g =
      P.eval coord*(P.field.x (u.1,i) v*P.eval g)
    rw [hom_coord,mul_assoc]
  · simp [h]
end Pair
end KirchbergRordam.GenericRW.OrderZero
end

end OAI