import Mathlib
import OAI.Computability.DirectedFeedback.Machines.MachineBinaryNameMachine

namespace OAI


namespace DFVSGames.Explicit.ProductTarget

open DFVSGames.Foundations
open Target
open MachineOutputContract
open scoped BigOperators

variable {L R E : Type*} {q N M : ℕ}

def fullTable (p : Equiv.Perm (Fin q)) : PermutationTable q where
  images := Vector.ofFn p
  inverseImages := Vector.ofFn p.symm
  leftInverse a := by simp
  rightInverse a := by simp

@[simp] theorem fullTable_images (p : Equiv.Perm (Fin q)) (a : Fin q) :
    (fullTable p).images[a] = p a := by simp [fullTable]

@[simp] theorem permutationEquiv_fullTable (p : Equiv.Perm (Fin q)) :
    permutationEquiv (fullTable p) = p := by
  ext a
  simp [permutationEquiv, fullTable]

def row (G : BipartiteGame L R E (Fin q)) (vertices : (L ⊕ R) ≃ Fin N)
    (edges : Fin M ≃ E) (tables : E → PermutationTable q) (i : Fin M) :
    Constraint N q where
  source := vertices (Sum.inl (G.left (edges i)))
  target := vertices (Sum.inr (G.right (edges i)))
  permutation := tables (edges i)

def render (G : BipartiteGame L R E (Fin q)) (vertices : (L ⊕ R) ≃ Fin N)
    (edges : Fin M ≃ E) (tables : E → PermutationTable q) (hM : 0 < M) :
    Instance q where
  vertices := N
  constraints := List.ofFn (row G vertices edges tables)
  nonempty := by
    intro hempty
    have hlength := congrArg List.length hempty
    simp only [List.length_ofFn, List.length_nil] at hlength
    omega

@[simp] theorem render_length (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M) :
    (render G vertices edges tables hM).constraints.length = M := by
  simp [render]

theorem render_get (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M)
    (i : Fin (render G vertices edges tables hM).constraints.length) :
    (render G vertices edges tables hM).constraints[i] =
      row G vertices edges tables ⟨i.val, by simpa using i.isLt⟩ := by
  change (List.ofFn (row G vertices edges tables))[i.val]'(by simpa using i.isLt) = _
  exact List.getElem_ofFn (by simpa using i.isLt)

def render_simpleBipartite (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M) :
    SimpleBipartite (render G vertices edges tables hM) where
  side v := Sum.elim (fun _ => false) (fun _ => true) (vertices.symm v)
  sourceSide i := by simp only [render_get, row, Equiv.symm_apply_apply, Sum.elim_inl]
  targetSide i := by simp only [render_get, row, Equiv.symm_apply_apply, Sum.elim_inr]
  endpoints_injective := by
    intro i j hij
    have hi : i.val < M := by simpa using i.isLt
    have hj : j.val < M := by simpa using j.isLt
    have hrows :
        ((row G vertices edges tables ⟨i.val, hi⟩).source,
          (row G vertices edges tables ⟨i.val, hi⟩).target) =
        ((row G vertices edges tables ⟨j.val, hj⟩).source,
          (row G vertices edges tables ⟨j.val, hj⟩).target) := by
      simp only [render_get] at hij
      exact hij
    have hedge : edges ⟨i.val, hi⟩ = edges ⟨j.val, hj⟩ := by
      apply G.simple
      apply Prod.ext
      · exact Sum.inl.inj (vertices.injective (congrArg Prod.fst hrows))
      · exact Sum.inr.inj (vertices.injective (congrArg Prod.snd hrows))
    exact Fin.ext (congrArg (fun k : Fin M => k.val) (edges.injective hedge))

section Value

variable [Fintype L] [Fintype R] [Fintype E]

omit [Fintype L] [Fintype R] in

theorem render_count (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M)
    (htable : ∀ e, permutationEquiv (tables e) = G.permutation e)
    (labeling : Fin N → Fin q) :
    countSatisfied labeling (render G vertices edges tables hM).constraints =
      G.satisfiedCount (fun x => labeling (vertices (Sum.inl x)))
        (fun y => labeling (vertices (Sum.inr y))) := by
  classical
  have ht (e : E) (a : Fin q) : (tables e).images[a] = G.permutation e a :=
    congrArg (fun p : Equiv.Perm (Fin q) => p a) (htable e)
  change countSatisfied labeling (List.ofFn (row G vertices edges tables)) = _
  rw [Integration.GapSemantics.countSatisfied_ofFn]
  unfold BipartiteGame.satisfiedCount
  apply Fintype.sum_equiv edges
  intro i
  simp [row, Constraint.satisfied, ht]

def mergeLabelings (vertices : (L ⊕ R) ≃ Fin N)
    (left : L → Fin q) (right : R → Fin q) : Fin N → Fin q :=
  fun v => Sum.elim left right (vertices.symm v)

omit [Fintype L] [Fintype R] in
@[simp] theorem mergeLabelings_left (vertices : (L ⊕ R) ≃ Fin N)
    (left : L → Fin q) (right : R → Fin q) (x : L) :
    mergeLabelings vertices left right (vertices (Sum.inl x)) = left x := by
  simp [mergeLabelings]

omit [Fintype L] [Fintype R] in
@[simp] theorem mergeLabelings_right (vertices : (L ⊕ R) ≃ Fin N)
    (left : L → Fin q) (right : R → Fin q) (y : R) :
    mergeLabelings vertices left right (vertices (Sum.inr y)) = right y := by
  simp [mergeLabelings]

omit [Fintype L] [Fintype R] in
theorem render_count_merge (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M)
    (htable : ∀ e, permutationEquiv (tables e) = G.permutation e)
    (left : L → Fin q) (right : R → Fin q) :
    countSatisfied (mergeLabelings vertices left right)
      (render G vertices edges tables hM).constraints = G.satisfiedCount left right := by
  simpa only [mergeLabelings_left, mergeLabelings_right] using
    render_count G vertices edges tables hM htable (mergeLabelings vertices left right)

theorem render_maxSatisfied (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M)
    (htable : ∀ e, permutationEquiv (tables e) = G.permutation e) :
    Integration.InstanceValue.maxSatisfied (render G vertices edges tables hM) =
      G.maxSatisfied := by
  classical
  apply Nat.le_antisymm
  · unfold Integration.InstanceValue.maxSatisfied
    apply Finset.sup_le
    intro labeling _
    change Fin N → Fin q at labeling
    exact (render_count G vertices edges tables hM htable labeling).le.trans
      (G.satisfiedCount_le_maxSatisfied _ _)
  · unfold BipartiteGame.maxSatisfied
    apply Finset.sup_le
    intro labeling _
    rw [← render_count_merge G vertices edges tables hM htable]
    exact Integration.InstanceValue.countSatisfied_le_maxSatisfied
      (render G vertices edges tables hM) (mergeLabelings vertices labeling.1 labeling.2)

theorem render_value (G : BipartiteGame L R E (Fin q))
    (vertices : (L ⊕ R) ≃ Fin N) (edges : Fin M ≃ E)
    (tables : E → PermutationTable q) (hM : 0 < M)
    (htable : ∀ e, permutationEquiv (tables e) = G.permutation e) :
    Integration.InstanceValue.value (render G vertices edges tables hM) = G.value := by
  unfold Integration.InstanceValue.value BipartiteGame.value
  rw [render_maxSatisfied G vertices edges tables hM htable, render_length]
  have hcard : M = Fintype.card E := by simpa using Fintype.card_congr edges
  rw [hcard]

end Value

def tuples (n t : ℕ) : List (Fin t → Fin n) :=
  (List.finRange (n ^ t)).map finFunctionFinEquiv.symm

@[simp] theorem tuples_length (n t : ℕ) : (tuples n t).length = n ^ t := by
  simp [tuples]

theorem tuples_mem {n t : ℕ} (f : Fin t → Fin n) : f ∈ tuples n t := by
  apply List.mem_map.mpr
  exact ⟨finFunctionFinEquiv f, List.mem_finRange _, Equiv.symm_apply_apply _ _⟩

theorem tuples_nodup (n t : ℕ) : (tuples n t).Nodup :=
  (List.nodup_finRange _).map finFunctionFinEquiv.symm.injective

@[simp] theorem tuples_get (n t : ℕ) (i : Fin (n ^ t)) :
    (tuples n t)[i.val]'(by simpa only [tuples_length] using i.isLt) =
      finFunctionFinEquiv.symm i := by
  simp [tuples]

theorem tuple_address (n t : ℕ) (f : Fin t → Fin n) :
    (finFunctionFinEquiv f : ℕ) = ∑ i : Fin t, (f i : ℕ) * n ^ (i : ℕ) :=
  finFunctionFinEquiv_apply f

theorem address_eq_ofDigits {n t : ℕ} (f : Fin t → Fin n) :
    (finFunctionFinEquiv f : ℕ) = Nat.ofDigits n (List.ofFn (fun i => (f i : ℕ))) := by
  have hmap :
      (List.ofFn (fun i => (f i : ℕ))).mapIdx (fun i a => a * n ^ i) =
        List.ofFn (fun i : Fin t => (f i : ℕ) * n ^ (i : ℕ)) := by
    apply List.ext_getElem
    · simp
    · intro i hi hj
      simp
  rw [finFunctionFinEquiv_apply, Nat.ofDigits_eq_sum_mapIdx, hmap, List.sum_ofFn]

theorem address_eq_horner {n t : ℕ} (f : Fin t → Fin n) :
    (finFunctionFinEquiv f : ℕ) =
      (List.ofFn (fun i => (f i : ℕ))).reverse.foldl
        (fun acc digit => n * acc + digit) 0 := by
  rw [address_eq_ofDigits, Nat.ofDigits_eq_foldr, List.foldl_reverse]
  simp only [Nat.cast_id, Nat.add_comm]

end DFVSGames.Explicit.ProductTarget


namespace DFVSGames.Explicit.SubdivisionTarget

open DFVSGames.Foundations Target
open MachineOutputContract
open scoped BigOperators

def ofInstance {q : Nat} (H : Instance q) :
    OccurrenceGame (Fin H.vertices) (Fin H.constraints.length) (Fin q) where
  source e := H.constraints[e].source
  target e := H.constraints[e].target
  permutation e := permutationEquiv H.constraints[e].permutation

theorem ofInstance_count {q : Nat} (H : Instance q) (a : Fin H.vertices → Fin q) :
    (ofInstance H).satisfiedCount a = countSatisfied a H.constraints := by
  have h := Integration.GapSemantics.countSatisfied_ofFn a
    (fun i : Fin H.constraints.length => H.constraints[i.val])
  rw [List.ofFn_getElem] at h
  rw [h]
  simp only [OccurrenceGame.satisfiedCount, ofInstance, permutationEquiv,
    Equiv.coe_fn_mk, Constraint.satisfied, decide_eq_true_eq, Fin.getElem_fin]
  rfl

theorem ofInstance_maxSatisfied {q : Nat} (H : Instance q) :
    (ofInstance H).maxSatisfied = Integration.InstanceValue.maxSatisfied H := by
  classical
  unfold OccurrenceGame.maxSatisfied Integration.InstanceValue.maxSatisfied
  apply Finset.sup_congr
  · ext a
    simp only [Finset.mem_univ]
  · intro a _
    exact ofInstance_count H a

theorem ofInstance_value {q : Nat} (H : Instance q) :
    (ofInstance H).value = Integration.InstanceValue.value H := by
  unfold OccurrenceGame.value Integration.InstanceValue.value
  rw [ofInstance_maxSatisfied]
  simp

def numericRightEquiv (Q : Nat) : Fin Q × Bool ≃ Fin (Q * 2) :=
  (Equiv.prodCongr (Equiv.refl (Fin Q)) finTwoEquiv.symm).trans finProdFinEquiv

@[simp] theorem numericRightEquiv_false_val (Q : Nat) (e : Fin Q) :
    (numericRightEquiv Q (e, false)).val = 2 * e.val := by
  change 0 + 2 * e.val = 2 * e.val
  exact Nat.zero_add _

@[simp] theorem numericRightEquiv_true_val (Q : Nat) (e : Fin Q) :
    (numericRightEquiv Q (e, true)).val = 2 * e.val + 1 := by
  change 1 + 2 * e.val = 2 * e.val + 1
  exact Nat.add_comm _ _

def numericVertexEquiv (n Q : Nat) :
    (Fin n ⊕ Fin Q) ⊕ (Fin Q × Bool) ≃ Fin (n + 3 * Q) :=
  ((Equiv.sumCongr
      (finSumFinEquiv : Fin n ⊕ Fin Q ≃ Fin (n + Q))
      (numericRightEquiv Q)).trans
    (finSumFinEquiv : Fin (n + Q) ⊕ Fin (Q * 2) ≃ Fin ((n + Q) + Q * 2))).trans
      (finCongr (by ring : (n + Q) + Q * 2 = n + 3 * Q))

@[simp] theorem numericVertexEquiv_original_val (n Q : Nat) (v : Fin n) :
    (numericVertexEquiv n Q (Sum.inl (Sum.inl v))).val = v.val := rfl

@[simp] theorem numericVertexEquiv_middle_val (n Q : Nat) (e : Fin Q) :
    (numericVertexEquiv n Q (Sum.inl (Sum.inr e))).val = n + e.val := rfl

@[simp] theorem numericVertexEquiv_p_val (n Q : Nat) (e : Fin Q) :
    (numericVertexEquiv n Q (Sum.inr (e, false))).val = n + Q + 2 * e.val := by
  change n + Q + (0 + 2 * e.val) = n + Q + 2 * e.val
  rw [Nat.zero_add]

@[simp] theorem numericVertexEquiv_r_val (n Q : Nat) (e : Fin Q) :
    (numericVertexEquiv n Q (Sum.inr (e, true))).val = n + Q + 2 * e.val + 1 := by
  change n + Q + (1 + 2 * e.val) = n + Q + 2 * e.val + 1
  omega

def numericEdgeEquiv (Q : Nat) : Fin (4 * Q) ≃ Fin Q × Fin 4 :=
  (finCongr (Nat.mul_comm 4 Q)).trans finProdFinEquiv.symm

@[simp] theorem numericEdgeEquiv_symm_val (Q : Nat) (e : Fin Q) (i : Fin 4) :
    ((numericEdgeEquiv Q).symm (e, i)).val = 4 * e.val + i.val := by
  change i.val + 4 * e.val = 4 * e.val + i.val
  exact Nat.add_comm _ _

def tables {q : Nat} (H : Instance q) (ei : Fin H.constraints.length × Fin 4) :
    PermutationTable q :=
  if ei.2 = 3 then MachineSubdivisionRows.inverseTable H.constraints[ei.1].permutation
  else MachineSubdivisionRows.identityTable q

theorem tables_correspond {q : Nat} (H : Instance q)
    (ei : Fin H.constraints.length × Fin 4) :
    permutationEquiv (tables H ei) = (Subdivision.game (ofInstance H)).permutation ei := by
  ext a
  by_cases hi : ei.2 = 3 <;>
    simp [tables, permutationEquiv, Subdivision.game, Subdivision.permutation, ofInstance,
      MachineSubdivisionRows.inverseTable, MachineSubdivisionRows.identityTable, hi]

def vertexFields {q : Nat} (H : Instance q) (e : Fin H.constraints.length) :
    Fin 5 → Fin (H.vertices + 3 * H.constraints.length) :=
  ![numericVertexEquiv _ _ (Sum.inl (Sum.inl H.constraints[e].source)),
    numericVertexEquiv _ _ (Sum.inr (e, false)),
    numericVertexEquiv _ _ (Sum.inl (Sum.inr e)),
    numericVertexEquiv _ _ (Sum.inr (e, true)),
    numericVertexEquiv _ _ (Sum.inl (Sum.inl H.constraints[e].target))]

theorem vertexFields_val {q : Nat} (H : Instance q) (e : Fin H.constraints.length)
    (j : Fin 5) :
    (vertexFields H e j).val = MachineSubdivisionRows.subdivisionVertexWords
      H.vertices H.constraints.length H.constraints[e].source.val
        H.constraints[e].target.val e.val j := by
  fin_cases j <;> simp [vertexFields, MachineSubdivisionRows.subdivisionVertexWords]

theorem rows_eq {q : Nat} (H : Instance q) (e : Fin H.constraints.length) :
    List.ofFn (fun i : Fin 4 => ProductTarget.row (Subdivision.game (ofInstance H))
      (numericVertexEquiv H.vertices H.constraints.length)
      (numericEdgeEquiv H.constraints.length) (tables H)
      ((numericEdgeEquiv H.constraints.length).symm (e, i))) =
    MachineSubdivisionRows.rows (vertexFields H e) H.constraints[e].permutation := by
  simp [List.ofFn_succ, ProductTarget.row, Subdivision.game, Subdivision.left,
    Subdivision.right, ofInstance, tables, vertexFields, MachineSubdivisionRows.rows]

theorem tables_translation {q s : Nat}
    (coordinates : Fin q ≃ Integration.BinaryLinear.Vector s) (H : Instance q)
    (hH : Integration.TranslationTarget.IsTranslationInstance coordinates H)
    (ei : Fin H.constraints.length × Fin 4) :
    ∃ shift : Integration.BinaryLinear.Vector s, ∀ a : Fin q,
      coordinates ((tables H ei).images[a]) = coordinates a + shift := by
  by_cases hi : ei.2 = 3
  · obtain ⟨shift, hs⟩ := hH H.constraints[ei.1] (List.getElem_mem ei.1.isLt)
    refine ⟨shift, ?_⟩
    intro a
    simp only [tables, hi, ite_eq_left, MachineSubdivisionRows.inverseTable]
    have h := hs (H.constraints[ei.1].permutation.inverseImages[a])
    rw [H.constraints[ei.1].permutation.rightInverse] at h
    have hc := congrArg (fun x => x + shift) h
    simpa only [add_assoc, ZModModule.add_self, add_zero] using hc.symm
  · refine ⟨0, ?_⟩
    intro a
    simp [tables, hi, MachineSubdivisionRows.identityTable]

def subdivide {q : Nat} (H : Instance q) : Instance q :=
  ProductTarget.render (Subdivision.game (ofInstance H))
    (numericVertexEquiv H.vertices H.constraints.length)
    (numericEdgeEquiv H.constraints.length) (tables H)
    (by have h := H.constraintCount_positive; omega)

@[simp] theorem subdivide_vertices {q : Nat} (H : Instance q) :
    (subdivide H).vertices = H.vertices + 3 * H.constraints.length := rfl

@[simp] theorem subdivide_length {q : Nat} (H : Instance q) :
    (subdivide H).constraints.length = 4 * H.constraints.length := by
  apply ProductTarget.render_length

theorem subdivide_translation {q s : Nat}
    (coordinates : Fin q ≃ Integration.BinaryLinear.Vector s) (H : Instance q)
    (hH : Integration.TranslationTarget.IsTranslationInstance coordinates H) :
    Integration.TranslationTarget.IsTranslationInstance coordinates (subdivide H) := by
  intro c hc
  change c ∈ List.ofFn _ at hc
  obtain ⟨i, rfl⟩ := List.mem_ofFn.mp hc
  exact tables_translation coordinates H hH (numericEdgeEquiv H.constraints.length i)

def simpleBipartite {q : Nat} (H : Instance q) : SimpleBipartite (subdivide H) :=
  ProductTarget.render_simpleBipartite _ _ _ _ _

theorem numeric_side (n Q : Nat) (v : Fin (n + 3 * Q)) :
    Sum.elim (fun _ => false) (fun _ => true) ((numericVertexEquiv n Q).symm v) =
      decide (n + Q ≤ v.val) := by
  obtain ⟨x, rfl⟩ := (numericVertexEquiv n Q).surjective v
  rcases x with (v | e) | ⟨e, b⟩
  · simp only [Equiv.symm_apply_apply, Sum.elim_inl, numericVertexEquiv_original_val]
    have h : ¬ n + Q ≤ v.val := by omega
    simp [h]
  · simp only [Equiv.symm_apply_apply, Sum.elim_inl, numericVertexEquiv_middle_val]
    have h : ¬ n + Q ≤ n + e.val := by omega
    simp [h]
  · cases b
    · simp only [Equiv.symm_apply_apply, Sum.elim_inr, numericVertexEquiv_p_val]
      have h : n + Q ≤ n + Q + 2 * e.val := by omega
      simp [h]
    · simp only [Equiv.symm_apply_apply, Sum.elim_inr, numericVertexEquiv_r_val]
      have h : n + Q ≤ n + Q + 2 * e.val + 1 := by omega
      simp [h]

theorem simpleBipartite_side {q : Nat} (H : Instance q) (v : Fin (subdivide H).vertices) :
    (simpleBipartite H).side v = decide (H.vertices + H.constraints.length ≤ v.val) :=
  numeric_side H.vertices H.constraints.length v

theorem subdivide_count {q : Nat} (H : Instance q)
    (a : Fin (H.vertices + 3 * H.constraints.length) → Fin q) :
    countSatisfied a (subdivide H).constraints =
      (Subdivision.game (ofInstance H)).satisfiedCount
        (fun l => a (numericVertexEquiv H.vertices H.constraints.length (Sum.inl l)))
        (fun r => a (numericVertexEquiv H.vertices H.constraints.length (Sum.inr r))) :=
  ProductTarget.render_count _ _ _ _ _ (tables_correspond H) a

theorem subdivide_value {q : Nat} (H : Instance q) :
    Integration.InstanceValue.value (subdivide H) =
      (Subdivision.game (ofInstance H)).value :=
  ProductTarget.render_value _ _ _ _ _ (tables_correspond H)

theorem value_eq {q : Nat} (H : Instance q) (hq : 0 < q) :
    Integration.InstanceValue.value (subdivide H) =
      1 - (1 - Integration.InstanceValue.value H) / 4 := by
  let : Nonempty (Fin q) := ⟨⟨0, hq⟩⟩
  let : Nonempty (Fin H.constraints.length) := ⟨⟨0, H.constraintCount_positive⟩⟩
  rw [subdivide_value, Subdivision.value_eq, ofInstance_value]

end DFVSGames.Explicit.SubdivisionTarget


namespace DFVSGames.Explicit.SubdivisionEncoding

open DFVSGames.Foundations Target Complexity
open SubdivisionTarget

theorem subdivide_constraints {q : Nat} (H : Instance q) :
    (subdivide H).constraints =
      (List.ofFn (fun e : Fin H.constraints.length =>
        MachineSubdivisionRows.rows (vertexFields H e)
          H.constraints[e].permutation)).flatten := by
  change List.ofFn _ = _
  rw [List.ofFn_mul']
  congr 1
  apply congrArg List.ofFn
  funext e
  rw [← rows_eq H e]
  apply congrArg List.ofFn
  funext i
  congr 1
  apply Fin.ext
  simp only [numericEdgeEquiv_symm_val]

theorem subdivide_constraints_flatMap {q : Nat} (H : Instance q) :
    (subdivide H).constraints = (List.finRange H.constraints.length).flatMap
      (fun e => MachineSubdivisionRows.rows (vertexFields H e)
        H.constraints[e].permutation) := by
  rw [subdivide_constraints, List.ofFn_eq_map]
  rfl

theorem subdivide_gameWords {q : Nat} (H : Instance q) :
    gameWords (subdivide H) =
      [H.vertices + 3 * H.constraints.length, q, 4 * H.constraints.length] ++
      (List.finRange H.constraints.length).flatMap (fun e =>
        (MachineSubdivisionRows.rows (vertexFields H e)
          H.constraints[e].permutation).flatMap constraintWords) := by
  change [H.vertices + 3 * H.constraints.length, q, (subdivide H).constraints.length] ++
    (subdivide H).constraints.flatMap
      (@constraintWords (H.vertices + 3 * H.constraints.length) q) = _
  rw [subdivide_length, subdivide_constraints_flatMap, List.flatMap_assoc]

private theorem encodeWords_flatMap_inline_SubdivisionEncoding {X : Type*} (xs : List X) (f : X → List Nat) :
    encodeWords (xs.flatMap f) = xs.flatMap (fun x => encodeWords (f x)) := by
  induction xs with
  | nil => rfl
  | cons x xs ih => simp [ih]

theorem subdivide_gameBits {q : Nat} (H : Instance q) :
    gameBits (subdivide H) =
      encodeWords [H.vertices + 3 * H.constraints.length, q, 4 * H.constraints.length] ++
      (List.finRange H.constraints.length).flatMap (fun e =>
        MachineSubdivisionRows.rowBits (vertexFields H e) H.constraints[e].permutation) := by
  rw [gameBits, subdivide_gameWords, encodeWords_append, encodeWords_flatMap_inline_SubdivisionEncoding]
  rfl

theorem subdivide_gameWords_length {q : Nat} (H : Instance q) :
    (gameWords (subdivide H)).length = 3 + 4 * H.constraints.length * (q + 2) := by
  rw [gameWords_length, subdivide_length]

theorem subdivide_gameBits_length_le {q : Nat} (H : Instance q) :
    (gameBits (subdivide H)).length ≤
      H.vertices + 3 * H.constraints.length + q + 4 * H.constraints.length + 3 +
        (4 * H.constraints.length) *
          (2 * (H.vertices + 3 * H.constraints.length) + q * (q + 1)) := by
  have h := DFVSGames.Reduction.GameEncodingSize.gameBits_length_le (subdivide H)
  rw [subdivide_length] at h
  exact h

end DFVSGames.Explicit.SubdivisionEncoding


namespace DFVSGames.Explicit.MachineSubdivisionCorrespondence

open DFVSGames.Foundations DFVSGames.Foundations.Target
open DFVSGames.Foundations.Complexity
open MachineSubdivisionLoopFrame

def Involutive {q : Nat} (H : Instance q) : Prop :=
  ∀ e : Fin H.constraints.length,
    MachineSubdivisionRows.inverseTable H.constraints[e].permutation = H.constraints[e].permutation

theorem inverseTable_eq {q : Nat} (p : PermutationTable q)
    (same : p.inverseImages = p.images) : MachineSubdivisionRows.inverseTable p = p := by
  cases p with
  | mk images inverseImages left right =>
    dsimp at same
    cases same
    rfl

theorem translations_involutive {q s : Nat}
    (coordinates : Fin q ≃ Integration.BinaryLinear.Vector s) (H : Instance q)
    (translations : Integration.TranslationTarget.IsTranslationInstance coordinates H) :
    Involutive H := by
  intro e
  apply inverseTable_eq
  apply Vector.ext
  intro i hi
  apply coordinates.injective
  obtain ⟨shift, law⟩ := translations H.constraints[e] (List.getElem_mem e.isLt)
  have h := law (H.constraints[e].permutation.inverseImages[(⟨i, hi⟩ : Fin q)])
  rw [H.constraints[e].permutation.rightInverse] at h
  have cancel : shift + shift = 0 := by
    ext j
    simp [CharTwo.add_self_eq_zero]
  have doubled := congrArg (fun x => x + shift) h
  have inverseLaw : coordinates (H.constraints[e].permutation.inverseImages[(⟨i, hi⟩ : Fin q)]) =
      coordinates ⟨i, hi⟩ + shift := by
    simpa only [add_assoc, cancel, add_zero] using doubled.symm
  exact inverseLaw.trans (law ⟨i, hi⟩).symm

theorem rowBits_eq_semantic {q : Nat} (H : Instance q) (e : Fin H.constraints.length)
    (involutive : Involutive H) :
    rowBits H.constraints.length e.val H.constraints[e] =
      MachineSubdivisionRows.rowBits (SubdivisionTarget.vertexFields H e)
        H.constraints[e].permutation := by
  have words := MachineSubdivisionBodySpec.rowBits_eq_dynamic
    (SubdivisionTarget.vertexFields H e) H.constraints[e].permutation
  have vertices (j : Fin 5) := SubdivisionTarget.vertexFields_val H e j
  simp only [MachineSubdivisionRows.subdivisionVertexWords] at vertices
  have dynamic : MachineSubdivisionDynamicRows.rowBits
      (SubdivisionTarget.vertexFields H e) H.constraints[e].permutation =
      MachineSubdivisionRows.rowBits (SubdivisionTarget.vertexFields H e)
        H.constraints[e].permutation := by
    simp only [MachineSubdivisionDynamicRows.rowBits, MachineSubdivisionRows.rowBits,
      MachineSubdivisionDynamicRows.rows, MachineSubdivisionRows.rows, involutive e]
  rw [← dynamic, ← words]
  simp only [vertices, MachineSubdivisionBodySpec.rowBits, rowBits, identityBits,
    MachineSubdivisionBody.tableBits, encodeWords_append, List.append_assoc]

theorem outputRows_eq_ofFn {n q : Nat} (Q e : Nat) (edges : List (Constraint n q)) :
    outputRows Q e edges =
      (List.ofFn (fun i : Fin edges.length => rowBits Q (e + i.val) edges[i])).flatten := by
  induction edges generalizing e with
  | nil => rfl
  | cons edge edges ih =>
    rw [outputRows, ih, List.ofFn_succ]
    simp [Nat.add_comm, Nat.add_left_comm]

theorem outputRows_eq_semantic {q : Nat} (H : Instance q) (involutive : Involutive H) :
    outputRows H.constraints.length 0 H.constraints =
      (List.finRange H.constraints.length).flatMap (fun e =>
        MachineSubdivisionRows.rowBits (SubdivisionTarget.vertexFields H e)
          H.constraints[e].permutation) := by
  rw [outputRows_eq_ofFn]
  simp only [Nat.zero_add, rowBits_eq_semantic H _ involutive, List.ofFn_eq_map,
    List.flatMap_def]

theorem output_eq_gameBits {q : Nat} (H : Instance q) (involutive : Involutive H) :
    MachineSubdivisionEmission.headerBits H.vertices q H.constraints.length ++
      outputRows H.constraints.length 0 H.constraints =
      gameBits (SubdivisionTarget.subdivide H) := by
  rw [SubdivisionEncoding.subdivide_gameBits, outputRows_eq_semantic H involutive]
  rfl

end DFVSGames.Explicit.MachineSubdivisionCorrespondence


namespace DFVSGames.Explicit.MachineSubdivisionRuntime

open Turing
open DFVSGames.Foundations DFVSGames.Foundations.Target
open DFVSGames.Foundations.Complexity
open MachineSubdivisionProgram MachineSubdivisionLoopFrame
open MachineSubdivisionCorrespondence

noncomputable section

def prefixPolynomial (q : Nat) : Polynomial Nat :=
  Polynomial.X * (Polynomial.C 100 *
    (Polynomial.C 4 * Polynomial.X + Polynomial.C (q * (q + 1)) + 1) + 1) +
    Polynomial.C 62 * Polynomial.X + Polynomial.C (q + 50)

def timePolynomial (q : Nat) : Polynomial Nat :=
  MachineSubdivisionFinish.timePolynomial q (prefixPolynomial q)

theorem input_eq {q : Nat} (H : Instance q) :
    gameBits H = encodeWords [H.vertices, q, H.constraints.length] ++ bodyBits H.constraints := by
  simp only [gameBits, gameWords, bodyBits, encodeWords_append]

theorem input_size {q : Nat} (H : Instance q) :
    H.vertices ≤ (gameBits H).length ∧ H.constraints.length ≤ (gameBits H).length := by
  rw [input_eq]
  simp only [List.length_append, encodeWords_length, List.sum_cons, List.sum_nil,
    List.length_cons, List.length_nil]
  omega

def finalTapes {q : Nat} (H : Instance q) : Tape → List Bool :=
  frame H.constraints.length H.constraints.length ([] : List (Constraint H.vertices q))
    (MachineSubdivisionEmission.headerBits H.vertices q H.constraints.length ++
      outputRows H.constraints.length 0 H.constraints)

theorem final_outputEmpty {q : Nat} (H : Instance q) : finalTapes H .output = [] := rfl

theorem final_accumulator {q : Nat} (H : Instance q) (involutive : Involutive H) :
    finalTapes H .accumulator = (gameBits (SubdivisionTarget.subdivide H)).reverse := by
  change (MachineSubdivisionEmission.headerBits H.vertices q H.constraints.length ++
    outputRows H.constraints.length 0 H.constraints).reverse = _
  rw [output_eq_gameBits H involutive]

def prefixInTime {q : Nat} (H : Instance q) :
    StateTransition.EvalsToInTime (machine q).step
      (initList (machine q) (gameBits H))
      (some ⟨some .finishStart, initialState, finalTapes H⟩)
      ((prefixPolynomial q).eval (gameBits H).length) := by
  have initial := MachineSubdivisionEmission.prepareInTime q H.vertices H.constraints.length
    (bodyBits H.constraints)
  rw [← input_eq H, ← frame_prepared H.constraints] at initial
  have loop := MachineSubdivisionLoop.loopInTime H.constraints.length 0 H.constraints
    (MachineSubdivisionEmission.headerBits H.vertices q H.constraints.length) (by simp)
  simp only [Nat.zero_add] at loop
  have whole := StateTransition.EvalsToInTime.trans _ _ _ _ _ _ initial loop
  refine { toEvalsTo := whole.toEvalsTo, steps_le_m := ?_ }
  have hn := (input_size H).1
  have hQ := (input_size H).2
  have bodyBound : MachineSubdivisionLoop.bodyBound H.vertices q H.constraints.length + 1 ≤
      100 * (4 * (gameBits H).length + q * (q + 1) + 1) + 1 := by
    unfold MachineSubdivisionLoop.bodyBound
    omega
  have loopBound := Nat.mul_le_mul hQ bodyBound
  have prepBound : H.vertices + q + H.constraints.length + 6 +
      9 * MachineSubdivisionInit.stageCost H.vertices H.constraints.length +
      (3 * (H.vertices + 7 * H.constraints.length + 2) + 10) ≤
      62 * (gameBits H).length + q + 49 := by
    unfold MachineSubdivisionInit.stageCost
    omega
  have bound := whole.steps_le_m
  simp only [prefixPolynomial, Polynomial.eval_add, Polynomial.eval_mul,
    Polynomial.eval_C, Polynomial.eval_X, Polynomial.eval_one]
  omega

def fullRunInTime {q : Nat} (H : Instance q) (involutive : Involutive H) :
    TM2OutputsInTime (machine q) (gameBits H)
      (some (gameBits (SubdivisionTarget.subdivide H)))
      ((timePolynomial q).eval (gameBits H).length) := by
  have run := MachineSubdivisionFinish.completePrefix q (gameBits H) (prefixPolynomial q)
    (finalTapes H) (prefixInTime H) (final_outputEmpty H)
  simpa only [final_accumulator H involutive, List.reverse_reverse, timePolynomial] using run

def computableInPolyTime (q : Nat) :
    TM2ComputableInPolyTime
      (fun H : {H : Instance q // Involutive H} => gameBits H.val)
      gameBits (fun H => SubdivisionTarget.subdivide H.val) where
  tm := machine q
  inputAlphabet := Equiv.refl Bool
  outputAlphabet := Equiv.refl Bool
  time := timePolynomial q
  outputsFun H := by
    change TM2OutputsInTime (machine q) ((gameBits H.val).map (id : Bool → Bool))
      (some ((gameBits (SubdivisionTarget.subdivide H.val)).map (id : Bool → Bool)))
      ((timePolynomial q).eval (gameBits H.val).length)
    dsimp only [machine]
    simp only [List.map_id]
    exact fullRunInTime H.val H.property

def familyComputableInPolyTime {α : Type} {q : Nat} (f : α → Instance q)
    (involutive : ∀ a, Involutive (f a)) :
    TM2ComputableInPolyTime (fun a => gameBits (f a)) gameBits
      (fun a => SubdivisionTarget.subdivide (f a)) where
  tm := machine q
  inputAlphabet := Equiv.refl Bool
  outputAlphabet := Equiv.refl Bool
  time := timePolynomial q
  outputsFun a := by
    change TM2OutputsInTime (machine q) ((gameBits (f a)).map (id : Bool → Bool))
      (some ((gameBits (SubdivisionTarget.subdivide (f a))).map (id : Bool → Bool)))
      ((timePolynomial q).eval (gameBits (f a)).length)
    dsimp only [machine]
    simp only [List.map_id]
    exact fullRunInTime (f a) (involutive a)

theorem workAlphabetFinite (q : Nat) (tape : (computableInPolyTime q).tm.K) :
    Finite ((computableInPolyTime q).tm.Γ tape) := by
  change Finite Bool
  infer_instance

end
end DFVSGames.Explicit.MachineSubdivisionRuntime


namespace DFVSGames.Explicit.MachineSubdivisionCompose

open Turing
open DFVSGames.Foundations DFVSGames.Foundations.Target
open DFVSGames.Foundations.Complexity
open MachineSubdivisionCorrespondence

noncomputable section

variable {α : Type} {q : Nat} {encode : α → List Bool} {f : α → Instance q}

def certifiedOutput (involutive : ∀ a, Involutive (f a)) (a : α) :
    {H : Instance q // Involutive H} := ⟨f a, involutive a⟩

def certify (upstream : TM2ComputableInPolyTime encode gameBits f)
    (involutive : ∀ a, Involutive (f a)) :
    TM2ComputableInPolyTime encode (fun H : {H : Instance q // Involutive H} => gameBits H.val)
      (certifiedOutput involutive) where
  tm := upstream.tm
  inputAlphabet := upstream.inputAlphabet
  outputAlphabet := upstream.outputAlphabet
  time := upstream.time
  outputsFun := upstream.outputsFun

def computableInPolyTime (upstream : TM2ComputableInPolyTime encode gameBits f)
    (involutive : ∀ a, Involutive (f a)) :
    TM2ComputableInPolyTime encode gameBits (fun a => SubdivisionTarget.subdivide (f a)) :=
  MachineSequential.composeBits (f := certifiedOutput involutive)
    (g := fun H : {H : Instance q // Involutive H} => SubdivisionTarget.subdivide H.val)
    (certify upstream involutive)
    (MachineSubdivisionRuntime.computableInPolyTime q)

theorem finiteAlphabet (upstream : TM2ComputableInPolyTime encode gameBits f)
    (involutive : ∀ a, Involutive (f a))
    (finite : MachineFiniteAlphabet.FiniteAlphabet upstream.tm) :
    MachineFiniteAlphabet.FiniteAlphabet (computableInPolyTime upstream involutive).tm := by
  exact MachineFiniteAlphabet.composeBits (certify upstream involutive)
    (MachineSubdivisionRuntime.computableInPolyTime q) finite
    (MachineSubdivisionRuntime.workAlphabetFinite q)

def translationComputableInPolyTime {s : Nat}
    (coordinates : Fin q ≃ Integration.BinaryLinear.Vector s)
    (upstream : TM2ComputableInPolyTime encode gameBits f)
    (translations : ∀ a, Integration.TranslationTarget.IsTranslationInstance coordinates (f a)) :
    TM2ComputableInPolyTime encode gameBits (fun a => SubdivisionTarget.subdivide (f a)) :=
  computableInPolyTime upstream (fun a => translations_involutive coordinates (f a) (translations a))

end
end DFVSGames.Explicit.MachineSubdivisionCompose

end OAI