lean/OAI/Computability/BinPacking/PCP/RawInitialPredicate.lean

import Mathlib.Computability.Encoding
import Mathlib.Logic.Equiv.Fin.Basic
import Mathlib.Tactic.FinCases
import OAI.Computability.BinPacking.PCP.AlphabetRetraction
import OAI.Computability.BinPacking.PCP.FiniteGraph
import OAI.Computability.BinPacking.Reductions.BinaryCoordinates

namespace OAI

namespace BinPackingGames.Foundations.PCP.GraphTables

open BinPackingGames.Foundations.Complexity

abbrev Label := Fin 64
abbrev RelationTable := Vector Bool 4096

def relationIndex : Label × Label ≃ Fin 4096 := finProdFinEquiv

theorem relationIndex_val (a b : Label) :
    (relationIndex (a, b)).val = b.val + 64 * a.val := rfl

def relationAt (table : RelationTable) (a b : Label) : Bool :=
  table[relationIndex (a, b)]

def relationOf (predicate : Label → Label → Bool) : RelationTable :=
  Vector.ofFn (fun i => predicate (relationIndex.symm i).1 (relationIndex.symm i).2)

@[simp] theorem relationAt_relationOf (predicate : Label → Label → Bool) (a b : Label) :
    relationAt (relationOf predicate) a b = predicate a b := by
  simp [relationAt, relationOf]

structure DartRow (vertices darts : Nat) where
  tail : Fin vertices
  reverseIndex : Fin darts
  relation : RelationTable

abbrev Rows (vertices darts : Nat) := Vector (DartRow vertices darts) darts

def reverseAt {n m : Nat} (rows : Rows n m) (e : Fin m) : Fin m :=
  rows[e].reverseIndex

def acceptsAt {n m : Nat} (rows : Rows n m) (e : Fin m) (a b : Label) : Bool :=
  relationAt rows[e].relation a b

def Valid {n m : Nat} (rows : Rows n m) : Prop :=
  (∀ e, reverseAt rows (reverseAt rows e) = e) ∧
  (∀ e a b, acceptsAt rows (reverseAt rows e) b a = acceptsAt rows e a b)

instance {n m : Nat} (rows : Rows n m) : Decidable (Valid rows) := by
  unfold Valid
  infer_instance

structure Table where
  vertices : Nat
  darts : Nat
  rows : Rows vertices darts
  valid : Valid rows

def rowList (table : Table) : List (DartRow table.vertices table.darts) := table.rows.toList

@[simp] theorem rowList_length (table : Table) : (rowList table).length = table.darts := by
  simp [rowList]

def semantics (table : Table) : ConstraintGraph (Fin table.vertices) (Fin table.darts) Label where
  reverse :=
    { toFun := reverseAt table.rows
      invFun := reverseAt table.rows
      left_inv := table.valid.1
      right_inv := table.valid.1 }
  reverse_involutive := table.valid.1
  tail e := table.rows[e].tail
  accepts := acceptsAt table.rows
  reverse_accepts := table.valid.2

@[simp] theorem semantics_reverse (table : Table) (e : Fin table.darts) :
    (semantics table).reverse e = table.rows[e].reverseIndex := rfl

@[simp] theorem semantics_tail (table : Table) (e : Fin table.darts) :
    (semantics table).tail e = table.rows[e].tail := rfl

@[simp] theorem semantics_accepts (table : Table) (e : Fin table.darts) (a b : Label) :
    (semantics table).accepts e a b = relationAt table.rows[e].relation a b := rfl

def graphRows {n m : Nat} (G : ConstraintGraph (Fin n) (Fin m) Label) : Rows n m :=
  Vector.ofFn (fun e => ⟨G.tail e, G.reverse e, relationOf (G.accepts e)⟩)

@[simp] theorem reverseAt_graphRows {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (e : Fin m) :
    reverseAt (graphRows G) e = G.reverse e := by
  simp [reverseAt, graphRows]

@[simp] theorem acceptsAt_graphRows {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (e : Fin m) (a b : Label) :
    acceptsAt (graphRows G) e a b = G.accepts e a b := by
  simp [acceptsAt, graphRows]

theorem graphRows_valid {n m : Nat} (G : ConstraintGraph (Fin n) (Fin m) Label) :
    Valid (graphRows G) := by
  constructor
  · intro e
    simpa using G.reverse_involutive e
  · intro e a b
    simpa using G.reverse_accepts e a b

def ofGraph {n m : Nat} (G : ConstraintGraph (Fin n) (Fin m) Label) : Table :=
  ⟨n, m, graphRows G, graphRows_valid G⟩

@[simp] theorem semantics_ofGraph_reverse {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (e : Fin m) :
    (semantics (ofGraph G)).reverse e = G.reverse e := by
  exact reverseAt_graphRows G e

@[simp] theorem semantics_ofGraph_tail {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (e : Fin m) :
    (semantics (ofGraph G)).tail e = G.tail e := by
  change (graphRows G)[e.val].tail = G.tail e
  simp only [graphRows, Vector.getElem_ofFn]

@[simp] theorem semantics_ofGraph_accepts {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (e : Fin m) (a b : Label) :
    (semantics (ofGraph G)).accepts e a b = G.accepts e a b := by
  exact acceptsAt_graphRows G e a b

@[simp] theorem semantics_ofGraph_edgeSatisfied {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (labeling : Fin n → Label) (e : Fin m) :
    (semantics (ofGraph G)).edgeSatisfied labeling e = G.edgeSatisfied labeling e := by
  simp [ConstraintGraph.edgeSatisfied, ConstraintGraph.head]

private theorem constraintGraph_ext {V E A : Type*} {G H : ConstraintGraph V E A}
    (hr : ∀ e, G.reverse e = H.reverse e) (ht : G.tail = H.tail)
    (hp : G.accepts = H.accepts) : G = H := by
  cases G with
  | mk reverse hinv tail accepts htranspose =>
    cases H with
    | mk reverse' hinv' tail' accepts' htranspose' =>
      dsimp only at hr ht hp
      have he : reverse = reverse' := Equiv.ext hr
      cases he
      cases ht
      cases hp
      rfl

@[simp] theorem semantics_ofGraph {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) : semantics (ofGraph G) = G := by
  apply constraintGraph_ext
  · exact semantics_ofGraph_reverse G
  · funext e
    exact semantics_ofGraph_tail G e
  · funext e a b
    exact semantics_ofGraph_accepts G e a b

@[simp] theorem semantics_ofGraph_rejectionCount {n m : Nat}
    (G : ConstraintGraph (Fin n) (Fin m) Label) (labeling : Fin n → Label) :
    (semantics (ofGraph G)).rejectionCount labeling = G.rejectionCount labeling := by
  rw [semantics_ofGraph]
  rfl

def enumeratedGraph {V E A : Type*} {n m : Nat} (G : ConstraintGraph V E A)
    (vertexOrder : V ≃ Fin n) (dartOrder : E ≃ Fin m) (labelOrder : A ≃ Label) :
    ConstraintGraph (Fin n) (Fin m) Label where
  reverse := (dartOrder.symm.trans G.reverse).trans dartOrder
  reverse_involutive e := by
    change dartOrder (G.reverse (dartOrder.symm
      (dartOrder (G.reverse (dartOrder.symm e))))) = e
    rw [dartOrder.symm_apply_apply, G.reverse_involutive, dartOrder.apply_symm_apply]
  tail e := vertexOrder (G.tail (dartOrder.symm e))
  accepts e a b := G.accepts (dartOrder.symm e) (labelOrder.symm a) (labelOrder.symm b)
  reverse_accepts e a b := by
    change G.accepts (dartOrder.symm (dartOrder (G.reverse (dartOrder.symm e))))
      (labelOrder.symm b) (labelOrder.symm a) = _
    rw [dartOrder.symm_apply_apply]
    exact G.reverse_accepts _ _ _

theorem enumeratedGraph_edgeSatisfied {V E A : Type*} {n m : Nat}
    (G : ConstraintGraph V E A) (vertexOrder : V ≃ Fin n) (dartOrder : E ≃ Fin m)
    (labelOrder : A ≃ Label) (labeling : V → A) (e : E) :
    (enumeratedGraph G vertexOrder dartOrder labelOrder).edgeSatisfied
      (fun v => labelOrder (labeling (vertexOrder.symm v))) (dartOrder e) =
        G.edgeSatisfied labeling e := by
  simp [ConstraintGraph.edgeSatisfied, ConstraintGraph.head, enumeratedGraph]

theorem enumeratedGraph_rejectionCount {V E A : Type*} [Fintype E] {n m : Nat}
    (G : ConstraintGraph V E A) (vertexOrder : V ≃ Fin n) (dartOrder : E ≃ Fin m)
    (labelOrder : A ≃ Label) (labeling : V → A) :
    (enumeratedGraph G vertexOrder dartOrder labelOrder).rejectionCount
      (fun v => labelOrder (labeling (vertexOrder.symm v))) = G.rejectionCount labeling := by
  classical
  unfold ConstraintGraph.rejectionCount
  symm
  apply Finset.card_equiv dartOrder
  intro e
  simp only [ConstraintGraph.mem_rejectedDarts, enumeratedGraph_edgeSatisfied]

def ofEnumeratedGraph {V E A : Type*} {n m : Nat} (G : ConstraintGraph V E A)
    (vertexOrder : V ≃ Fin n) (dartOrder : E ≃ Fin m) (labelOrder : A ≃ Label) : Table :=
  ofGraph (enumeratedGraph G vertexOrder dartOrder labelOrder)

def bitWord (b : Bool) : Nat := if b then 1 else 0

def parseBit : Nat → Option Bool
  | 0 => some false
  | 1 => some true
  | _ => none

@[simp] theorem parseBit_bitWord (b : Bool) : parseBit (bitWord b) = some b := by
  cases b <;> rfl

@[simp] theorem parseBits_bitWords (bits : List Bool) :
    (bits.map bitWord).mapM parseBit = some bits := by
  induction bits with
  | nil => rfl
  | cons bit bits ih => simp [ih]

def relationWords (relation : RelationTable) : List Nat := relation.toList.map bitWord

@[simp] theorem relationWords_length (relation : RelationTable) :
    (relationWords relation).length = 4096 := by simp [relationWords]

def parseRelation (words : List Nat) : Option RelationTable := do
  let bits ← words.mapM parseBit
  if length_ok : bits.length = 4096 then
    some ⟨bits.toArray, by simpa using length_ok⟩
  else none

@[simp] theorem parseRelation_encoded (relation : RelationTable) :
    parseRelation (relationWords relation) = some relation := by
  unfold parseRelation relationWords
  rw [parseBits_bitWords]
  simp
  exact Vector.toArray_toList

def rowWords {n m : Nat} (row : DartRow n m) : List Nat :=
  [row.tail.val, row.reverseIndex.val] ++ relationWords row.relation

def parseRow (vertices darts : Nat) : List Nat → Option (DartRow vertices darts × List Nat)
  | tail :: reverseIndex :: words => do
      let tail ← parseLabel vertices tail
      let reverseIndex ← parseLabel darts reverseIndex
      let relation ← parseRelation (words.take 4096)
      return (⟨tail, reverseIndex, relation⟩, words.drop 4096)
  | _ => none

@[simp] theorem parseRow_encoded {n m : Nat} (row : DartRow n m) (rest : List Nat) :
    parseRow n m (rowWords row ++ rest) = some (row, rest) := by
  cases row with
  | mk tail reverseIndex relation =>
      have taken := List.take_left' (l₂ := rest) (relationWords_length relation)
      have dropped := List.drop_left' (l₂ := rest) (relationWords_length relation)
      simp [rowWords, parseRow, taken, dropped]

def parseRows (vertices darts : Nat) :
    Nat → List Nat → Option (List (DartRow vertices darts) × List Nat)
  | 0, words => some ([], words)
  | count + 1, words => do
      let (row, words) ← parseRow vertices darts words
      let (rows, words) ← parseRows vertices darts count words
      return (row :: rows, words)

@[simp] theorem parseRows_encoded {n m : Nat} (rows : List (DartRow n m)) (rest : List Nat) :
    parseRows n m rows.length (rows.flatMap rowWords ++ rest) = some (rows, rest) := by
  induction rows with
  | nil => rfl
  | cons row rows ih => simp [parseRows, List.append_assoc, ih]

def tableWords (table : Table) : List Nat :=
  [table.vertices, table.darts] ++ (rowList table).flatMap rowWords

def tableBits (table : Table) : List Bool := encodeWords (tableWords table)

def decodeTableWords : List Nat → Option Table
  | vertices :: darts :: words => do
      let (parsed, trailing) ← parseRows vertices darts darts words
      if trailing = [] then
        if length_ok : parsed.length = darts then
          let rows : Rows vertices darts := ⟨parsed.toArray, by simpa using length_ok⟩
          if valid : Valid rows then some ⟨vertices, darts, rows, valid⟩ else none
        else none
      else none
  | _ => none

@[simp] theorem decodeTableWords_encoded (table : Table) :
    decodeTableWords (tableWords table) = some table := by
  cases table with
  | mk vertices darts rows valid =>
      have parsed := parseRows_encoded rows.toList []
      simp only [Vector.length_toList, List.append_nil] at parsed
      simp [tableWords, rowList, decodeTableWords, parsed, valid, Vector.toArray_toList]

def decodeTableBits (bits : List Bool) : Option Table :=
  decodeWords bits >>= decodeTableWords

@[simp] theorem decodeTableBits_encoded (table : Table) :
    decodeTableBits (tableBits table) = some table := by
  simp [decodeTableBits, tableBits]

def encoding : Computability.Encoding Table Bool where
  encode := tableBits
  decode := decodeTableBits
  decode_encode := decodeTableBits_encoded

theorem tableBits_injective : Function.Injective tableBits := encoding.encode_injective

@[simp] theorem rowWords_length {n m : Nat} (row : DartRow n m) :
    (rowWords row).length = 4098 := by simp [rowWords]

theorem rowsWords_length {n m : Nat} (rows : List (DartRow n m)) :
    (rows.flatMap rowWords).length = 4098 * rows.length := by
  induction rows with
  | nil => rfl
  | cons row rows ih => simp [ih, Nat.mul_add, Nat.add_comm]

@[simp] theorem tableWords_length (table : Table) :
    (tableWords table).length = 2 + 4098 * table.darts := by
  simp only [tableWords, List.length_append, List.length_cons, List.length_nil,
    rowsWords_length, rowList_length]

theorem tableWords_length_le_bits (table : Table) :
    2 + 4098 * table.darts ≤ (tableBits table).length := by
  rw [tableBits, encodeWords_length, ← tableWords_length]
  omega

theorem relationBits_length_le (relation : RelationTable) :
    (encodeWords (relationWords relation)).length ≤ 8192 := by
  have h := encodeWords_length_le (relationWords relation) 1 (by
    intro word hword
    obtain ⟨bit, _, rfl⟩ := List.mem_map.mp hword
    cases bit <;> decide)
  simpa only [relationWords_length] using h

theorem rowBits_length_le {n m : Nat} (row : DartRow n m) :
    (encodeWords (rowWords row)).length ≤ n + m + 8192 := by
  have ht := row.tail.isLt
  have hr := row.reverseIndex.isLt
  have hp := relationBits_length_le row.relation
  simp only [rowWords, encodeWords_append, List.length_append, encodeWords,
    encodeWord_length, List.length_nil] at ⊢
  omega

theorem rowsBits_length_le {n m : Nat} (rows : List (DartRow n m)) :
    (encodeWords (rows.flatMap rowWords)).length ≤ rows.length * (n + m + 8192) := by
  induction rows with
  | nil => simp [encodeWords]
  | cons row rows ih =>
      have hrow := rowBits_length_le row
      simp only [List.flatMap_cons, encodeWords_append, List.length_append,
        List.length_cons, Nat.add_mul, Nat.one_mul]
      omega

theorem tableBits_length_le (table : Table) :
    (tableBits table).length ≤ table.vertices + table.darts + 2 +
      table.darts * (table.vertices + table.darts + 8192) := by
  have hrows := rowsBits_length_le (rowList table)
  rw [rowList_length] at hrows
  simp only [tableBits, tableWords, encodeWords_append, List.length_append,
    encodeWords, encodeWord_length, List.length_nil]
  omega

theorem vertices_le_tableBits_length (table : Table) :
    table.vertices ≤ (tableBits table).length := by
  simp only [tableBits, tableWords, encodeWords_append, List.length_append,
    encodeWords, encodeWord_length, List.length_nil]
  omega

theorem darts_le_tableBits_length (table : Table) :
    table.darts ≤ (tableBits table).length := by
  simp only [tableBits, tableWords, encodeWords_append, List.length_append,
    encodeWords, encodeWord_length, List.length_nil]
  omega

end BinPackingGames.Foundations.PCP.GraphTables

namespace BinPackingGames.Foundations.PCP.PortTables

open PoweringWalks

abbrev Label := GraphTables.Label

def rowIndex (vertices ports : Nat) :
    Fin vertices × Fin ports ≃ Fin (vertices * ports) := finProdFinEquiv

@[simp] theorem rowIndex_val (n d : Nat) (e : Fin n × Fin d) :
    (rowIndex n d e).val = e.2.val + d * e.1.val := rfl

structure Table (vertices ports : Nat) where
  reverseIndex : Vector (Fin (vertices * ports)) (vertices * ports)
  relations : Vector GraphTables.RelationTable (vertices * ports)
  involutive : Function.Involutive
    (fun i : Fin (vertices * ports) => reverseIndex[i])
  transpose : ∀ (i : Fin (vertices * ports)) (a b : Label),
    GraphTables.relationAt relations[reverseIndex[i]] b a =
      GraphTables.relationAt relations[i] a b

variable {n d : Nat}

def rotation (table : Table n d) (e : Fin n × Fin d) : Fin n × Fin d :=
  (rowIndex n d).symm table.reverseIndex[rowIndex n d e]

def accepts (table : Table n d) (e : Fin n × Fin d) (a b : Label) : Bool :=
  GraphTables.relationAt table.relations[rowIndex n d e] a b

@[simp] theorem rowIndex_rotation (table : Table n d) (e : Fin n × Fin d) :
    rowIndex n d (rotation table e) = table.reverseIndex[rowIndex n d e] := by
  exact (rowIndex n d).apply_symm_apply _

theorem rotation_involutive (table : Table n d) : Function.Involutive (rotation table) := by
  intro e
  simp only [rotation, Equiv.apply_symm_apply]
  exact (congrArg (rowIndex n d).symm (table.involutive (rowIndex n d e))).trans
    ((rowIndex n d).symm_apply_apply e)

theorem accepts_rotation (table : Table n d) (e : Fin n × Fin d) (a b : Label) :
    accepts table (rotation table e) b a = accepts table e a b := by
  simpa only [accepts, rowIndex_rotation] using table.transpose (rowIndex n d e) a b

def portGraph (table : Table n d) : PortGraph (Fin n) (Fin d) where
  rot :=
    { toFun := rotation table
      invFun := rotation table
      left_inv := rotation_involutive table
      right_inv := rotation_involutive table }
  rot_involutive := rotation_involutive table

@[simp] theorem portGraph_rot (table : Table n d) (e : Fin n × Fin d) :
    (portGraph table).rot e = rotation table e := rfl

def baseGraph (table : Table n d) : ConstraintGraph (Fin n) (Fin n × Fin d) Label where
  reverse := (portGraph table).rot
  reverse_involutive := rotation_involutive table
  tail := Prod.fst
  accepts := accepts table
  reverse_accepts := accepts_rotation table

@[simp] theorem baseGraph_reverse (table : Table n d) (e : Fin n × Fin d) :
    (baseGraph table).reverse e = rotation table e := rfl

@[simp] theorem baseGraph_tail (table : Table n d) (e : Fin n × Fin d) :
    (baseGraph table).tail e = e.1 := rfl

@[simp] theorem baseGraph_head (table : Table n d) (e : Fin n × Fin d) :
    (baseGraph table).head e = (rotation table e).1 := rfl

@[simp] theorem baseGraph_accepts (table : Table n d) (e : Fin n × Fin d) (a b : Label) :
    (baseGraph table).accepts e a b = accepts table e a b := rfl

def ofPortGraph (G : PortGraph (Fin n) (Fin d))
    (predicate : (Fin n × Fin d) → Label → Label → Bool)
    (htranspose : ∀ e a b, predicate (G.rot e) b a = predicate e a b) : Table n d where
  reverseIndex := Vector.ofFn (fun i => rowIndex n d (G.rot ((rowIndex n d).symm i)))
  relations := Vector.ofFn (fun i => GraphTables.relationOf (predicate ((rowIndex n d).symm i)))
  involutive := by
    intro i
    simp only [Fin.getElem_fin, Vector.getElem_ofFn, Fin.eta,
      Equiv.symm_apply_apply]
    exact (congrArg (rowIndex n d) (G.rot_involutive ((rowIndex n d).symm i))).trans
      ((rowIndex n d).apply_symm_apply i)
  transpose := by
    intro i a b
    simp only [Fin.getElem_fin, Vector.getElem_ofFn, Fin.eta,
      Equiv.symm_apply_apply, GraphTables.relationAt_relationOf]
    exact htranspose ((rowIndex n d).symm i) a b

@[simp] theorem rotation_ofPortGraph (G : PortGraph (Fin n) (Fin d))
    (predicate : (Fin n × Fin d) → Label → Label → Bool)
    (htranspose : ∀ e a b, predicate (G.rot e) b a = predicate e a b)
    (e : Fin n × Fin d) : rotation (ofPortGraph G predicate htranspose) e = G.rot e := by
  simp only [rotation, ofPortGraph, Fin.getElem_fin, Vector.getElem_ofFn, Fin.eta,
    Equiv.symm_apply_apply]

@[simp] theorem accepts_ofPortGraph (G : PortGraph (Fin n) (Fin d))
    (predicate : (Fin n × Fin d) → Label → Label → Bool)
    (htranspose : ∀ e a b, predicate (G.rot e) b a = predicate e a b)
    (e : Fin n × Fin d) (a b : Label) :
    accepts (ofPortGraph G predicate htranspose) e a b = predicate e a b := by
  simp only [accepts, ofPortGraph, Fin.getElem_fin, Vector.getElem_ofFn, Fin.eta,
    Equiv.symm_apply_apply, GraphTables.relationAt_relationOf]

def flatRows (table : Table n d) : GraphTables.Rows n (n * d) :=
  Vector.ofFn (fun i =>
    ⟨((rowIndex n d).symm i).1, table.reverseIndex[i], table.relations[i]⟩)

@[simp] theorem reverseAt_flatRows (table : Table n d) (i : Fin (n * d)) :
    GraphTables.reverseAt (flatRows table) i = table.reverseIndex[i] := by
  simp [GraphTables.reverseAt, flatRows]

@[simp] theorem acceptsAt_flatRows (table : Table n d) (i : Fin (n * d)) (a b : Label) :
    GraphTables.acceptsAt (flatRows table) i a b = GraphTables.relationAt table.relations[i] a b := by
  simp [GraphTables.acceptsAt, flatRows]

theorem flatRows_valid (table : Table n d) : GraphTables.Valid (flatRows table) := by
  constructor
  · intro i
    simpa only [reverseAt_flatRows] using table.involutive i
  · intro i a b
    simpa only [reverseAt_flatRows, acceptsAt_flatRows] using table.transpose i a b

def graphTable (table : Table n d) : GraphTables.Table :=
  ⟨n, n * d, flatRows table, flatRows_valid table⟩

def tableWords (table : Table n d) : List Nat := GraphTables.tableWords (graphTable table)

def tableBits (table : Table n d) : List Bool := GraphTables.tableBits (graphTable table)

abbrev Input (ports : Nat) := (vertices : Nat) × Table vertices ports

def inputBits {ports : Nat} (input : Input ports) : List Bool := tableBits input.2

theorem tableWords_eq (table : Table n d) :
    tableWords table = [n, n * d] ++ (flatRows table).toList.flatMap GraphTables.rowWords := rfl

theorem tableWords_length (table : Table n d) :
    (tableWords table).length = 2 + 4098 * (n * d) :=
  GraphTables.tableWords_length (graphTable table)

theorem vertices_le_tableBits_length (table : Table n d) : n ≤ (tableBits table).length :=
  GraphTables.vertices_le_tableBits_length (graphTable table)

end BinPackingGames.Foundations.PCP.PortTables

namespace BinPackingGames.Foundations.PCP.PortTableLookup

private theorem flatMap_word {α β : Type*} (f : α → List β)
    (width j : Nat) (hj : j < width) :
    ∀ (rows : List α), (∀ a ∈ rows, (f a).length = width) →
      ∀ (i : Nat) (row : α), rows[i]? = some row →
        (rows.flatMap f)[width * i + j]? = (f row)[j]? := by
  intro rows
  induction rows with
  | nil =>
      intro _ i row selected
      simp at selected
  | cons a rows ih =>
      intro hwidth i row selected
      have ha : (f a).length = width := hwidth a (by simp)
      cases i with
      | zero =>
          have heq : a = row := by simpa using selected
          subst row
          simp only [Nat.mul_zero, Nat.zero_add, List.flatMap_cons]
          exact List.getElem?_append_left (by omega)
      | succ i =>
          have selected' : rows[i]? = some row := by simpa using selected
          have hskip : (f a).length ≤ width * (i + 1) + j := by
            rw [ha, Nat.mul_add, Nat.mul_one]
            omega
          have hoff : width * (i + 1) + j - (f a).length = width * i + j := by
            rw [ha, Nat.mul_add, Nat.mul_one]
            omega
          rw [List.flatMap_cons, List.getElem?_append_right hskip, hoff]
          exact ih (fun b hb => hwidth b (by simp [hb])) i row selected'

variable {n d : Nat}

theorem vertices_word (table : PortTables.Table n d) :
    (PortTables.tableWords table)[0]? = some n := rfl

theorem darts_word (table : PortTables.Table n d) :
    (PortTables.tableWords table)[1]? = some (n * d) := rfl

private theorem row_word (table : PortTables.Table n d) (i : Fin (n * d))
    (j : Nat) (hj : j < 4098) :
    (PortTables.tableWords table)[2 + 4098 * i.val + j]? =
      (GraphTables.rowWords (PortTables.flatRows table)[i])[j]? := by
  rw [PortTables.tableWords_eq]
  change (n :: n * d :: (PortTables.flatRows table).toList.flatMap
    GraphTables.rowWords)[2 + 4098 * i.val + j]? = _
  rw [show 2 + 4098 * i.val + j = (4098 * i.val + j + 1) + 1 by omega,
    List.getElem?_cons_succ, List.getElem?_cons_succ]
  apply flatMap_word GraphTables.rowWords 4098 j hj
    (PortTables.flatRows table).toList
    (fun row _ => GraphTables.rowWords_length row) i.val
    ((PortTables.flatRows table)[i])
  simp only [Vector.getElem?_toList, Vector.getElem?_eq_getElem i.isLt,
    Fin.getElem_fin]

theorem tail_word (table : PortTables.Table n d) (i : Fin (n * d)) :
    (PortTables.tableWords table)[2 + 4098 * i.val]? =
      some (((PortTables.rowIndex n d).symm i).1.val) := by
  have h := row_word table i 0 (by decide)
  simpa only [Nat.add_zero, GraphTables.rowWords, PortTables.flatRows,
    Fin.getElem_fin, Vector.getElem_ofFn, Fin.eta, List.cons_append,
    List.nil_append, List.getElem?_cons_zero] using h

theorem reverse_word (table : PortTables.Table n d) (i : Fin (n * d)) :
    (PortTables.tableWords table)[3 + 4098 * i.val]? =
      some (table.reverseIndex[i].val) := by
  have h := row_word table i 1 (by decide)
  rw [show 2 + 4098 * i.val + 1 = 3 + 4098 * i.val by omega] at h
  simpa only [GraphTables.rowWords, PortTables.flatRows, Fin.getElem_fin,
    Vector.getElem_ofFn, Fin.eta, List.cons_append, List.nil_append,
    List.getElem?_cons_succ, List.getElem?_cons_zero] using h

theorem relation_word (table : PortTables.Table n d) (i : Fin (n * d))
    (j : Fin 4096) :
    (PortTables.tableWords table)[4 + 4098 * i.val + j.val]? =
      some (GraphTables.bitWord table.relations[i][j]) := by
  have h := row_word table i (j.val + 2) (by omega)
  rw [show 2 + 4098 * i.val + (j.val + 2) = 4 + 4098 * i.val + j.val by omega] at h
  simpa only [GraphTables.rowWords, GraphTables.relationWords,
    PortTables.flatRows, Fin.getElem_fin, Vector.getElem_ofFn, Fin.eta,
    List.cons_append, List.nil_append, List.getElem?_cons_succ,
    List.getElem?_map, Vector.getElem?_toList,
    Vector.getElem?_eq_getElem j.isLt, Option.map_some] using h

theorem accepts_word (table : PortTables.Table n d) (e : Fin n × Fin d)
    (a b : PortTables.Label) :
    (PortTables.tableWords table)[4 + 4098 * (PortTables.rowIndex n d e).val +
        (GraphTables.relationIndex (a, b)).val]? =
      some (GraphTables.bitWord (PortTables.accepts table e a b)) :=
  relation_word table (PortTables.rowIndex n d e) (GraphTables.relationIndex (a, b))

theorem rotation_head_word (table : PortTables.Table n d) (e : Fin n × Fin d) :
    (PortTables.tableWords table)[2 + 4098 * (table.reverseIndex[PortTables.rowIndex n d e]).val]? =
      some ((PortTables.rotation table e).1.val) :=
  tail_word table (table.reverseIndex[PortTables.rowIndex n d e])

theorem rotor_lookups (table : PortTables.Table n d) (e : Fin n × Fin d) :
    (PortTables.tableWords table)[3 + 4098 * (PortTables.rowIndex n d e).val]? =
      some (table.reverseIndex[PortTables.rowIndex n d e].val) ∧
    (PortTables.tableWords table)[2 + 4098 * (table.reverseIndex[PortTables.rowIndex n d e]).val]? =
      some ((PortTables.rotation table e).1.val) :=
  ⟨reverse_word table (PortTables.rowIndex n d e), rotation_head_word table e⟩

end BinPackingGames.Foundations.PCP.PortTableLookup

namespace BinPackingGames.Foundations.PCP.PortTables

variable {n d : Nat}

def HasPortTails (rows : GraphTables.Rows n (n * d)) : Prop :=
  ∀ i : Fin (n * d), rows[i].tail = ((rowIndex n d).symm i).1

instance (rows : GraphTables.Rows n (n * d)) : Decidable (HasPortTails rows) := by
  unfold HasPortTails
  infer_instance

@[simp] theorem flatRows_hasPortTails (table : Table n d) : HasPortTails (flatRows table) := by
  intro i
  simp [flatRows]

def ofRows (rows : GraphTables.Rows n (n * d)) (valid : GraphTables.Valid rows) : Table n d where
  reverseIndex := Vector.ofFn (fun i => rows[i].reverseIndex)
  relations := Vector.ofFn (fun i => rows[i].relation)
  involutive := by
    intro i
    simp only [Fin.getElem_fin, Vector.getElem_ofFn]
    exact valid.1 i
  transpose := by
    intro i a b
    simp only [Fin.getElem_fin, Vector.getElem_ofFn]
    exact valid.2 i a b

private theorem table_ext {table table' : Table n d}
    (hr : table.reverseIndex = table'.reverseIndex)
    (hp : table.relations = table'.relations) : table = table' := by
  cases table
  cases table'
  cases hr
  cases hp
  rfl

@[simp] theorem ofRows_flatRows (table : Table n d) :
    ofRows (flatRows table) (flatRows_valid table) = table := by
  apply table_ext
  · apply Vector.ext
    intro i hi
    simp [ofRows, flatRows]
  · apply Vector.ext
    intro i hi
    simp [ofRows, flatRows]

def extractInput (ports : Nat) : GraphTables.Table → Option (Input ports)
  | ⟨vertices, darts, rows, valid⟩ =>
      if count_ok : darts = vertices * ports then
        let rows' : GraphTables.Rows vertices (vertices * ports) := count_ok ▸ rows
        let valid' : GraphTables.Valid rows' := by
          cases count_ok
          exact valid
        if HasPortTails rows' then
          some ⟨vertices, ofRows rows' valid'⟩
        else none
      else none

@[simp] theorem extractInput_graphTable (table : Table n d) :
    extractInput d (graphTable table) = some (⟨n, table⟩ : Input d) := by
  simp [extractInput, graphTable]

def decodeInputBits (ports : Nat) (bits : List Bool) : Option (Input ports) :=
  GraphTables.decodeTableBits bits >>= extractInput ports

@[simp] theorem decodeInputBits_inputBits {ports : Nat} (input : Input ports) :
    decodeInputBits ports (inputBits input) = some input := by
  rcases input with ⟨vertices, table⟩
  simp [decodeInputBits, inputBits, tableBits]

def encoding (ports : Nat) : Computability.Encoding (Input ports) Bool where
  encode := inputBits
  decode := decodeInputBits ports
  decode_encode := decodeInputBits_inputBits

theorem inputBits_injective (ports : Nat) : Function.Injective (@inputBits ports) :=
  (encoding ports).encode_injective

end BinPackingGames.Foundations.PCP.PortTables

namespace BinPackingGames.Foundations.PCP.RawInitialTables

open Target GraphTables

def unitOrder : Unit ≃ Fin 1 where
  toFun _ := 0
  invFun _ := ()
  left_inv _ := rfl
  right_inv i := by fin_cases i; rfl

def slotOrder : Slot ≃ Fin 3 where
  toFun
    | .first => 0
    | .second => 1
    | .third => 2
  invFun i := if i = 0 then .first else if i = 1 then .second else .third
  left_inv s := by cases s <;> rfl
  right_inv i := by fin_cases i <;> rfl

def binaryOrder (n : Nat) : (Fin n → Bool) ≃ Fin (2 ^ n) where
  toFun bits := (BinPackingGames.Integration.BinaryCoordinates.pack bits).toFin
  invFun index := BinPackingGames.Integration.BinaryCoordinates.unpack (BitVec.ofFin index)
  left_inv bits := BinPackingGames.Integration.BinaryCoordinates.unpack_pack bits
  right_inv index := by
    change (BinPackingGames.Integration.BinaryCoordinates.pack
      (BinPackingGames.Integration.BinaryCoordinates.unpack (BitVec.ofFin index))).toFin = index
    rw [BinPackingGames.Integration.BinaryCoordinates.pack_unpack]

def labelOrder : AlphabetRetraction.Label64 ≃ GraphTables.Label := binaryOrder 6

def vertexOrder (F : Formula) :
    InitialGraph.Vertex F ≃ Fin (F.variables + F.clauses.length + 1) :=
  ((finSumFinEquiv.sumCongr unitOrder).trans finSumFinEquiv)

def eventOrder (F : Formula) : RandomEvent F ≃ Fin (F.clauses.length * 3) :=
  ((Equiv.refl (Fin F.clauses.length)).prodCongr slotOrder).trans finProdFinEquiv

def dartOrder (F : Formula) : InitialGraph.Dart F ≃ Fin (6 * F.clauses.length + 1) :=
  (((((eventOrder F).prodCongr finTwoEquiv.symm).trans finProdFinEquiv).sumCongr
    unitOrder).trans finSumFinEquiv).trans (finCongr (by omega))

def raw64 (F : Formula) : ConstraintGraph (InitialGraph.Vertex F)
    (InitialGraph.Dart F) AlphabetRetraction.Label64 :=
  AlphabetRetraction.pullback (InitialGraph.raw F) AlphabetRetraction.decode64

def table (F : Formula) : GraphTables.Table :=
  GraphTables.ofEnumeratedGraph (raw64 F) (vertexOrder F) (dartOrder F) labelOrder

@[simp] theorem table_vertices (F : Formula) :
    (table F).vertices = F.variables + F.clauses.length + 1 := rfl

@[simp] theorem table_darts (F : Formula) : (table F).darts = 6 * F.clauses.length + 1 := rfl

theorem table_vertices_positive (F : Formula) : 0 < (table F).vertices := by
  rw [table_vertices]; omega

theorem table_darts_positive (F : Formula) : 0 < (table F).darts := by
  rw [table_darts]; omega

theorem raw64_satisfiable_iff (F : Formula) : (raw64 F).Satisfiable ↔ F.Satisfiable :=
  (AlphabetRetraction.satisfiable_pullback_iff (InitialGraph.raw F)
    AlphabetRetraction.decode64 AlphabetRetraction.encode64
      AlphabetRetraction.decode_encode64).trans (InitialGraph.raw_satisfiable_iff F)

theorem table_semantics (F : Formula) :
    GraphTables.semantics (table F) =
      (raw64 F).reindex (vertexOrder F) (dartOrder F) labelOrder := by
  change GraphTables.semantics (GraphTables.ofGraph
    (GraphTables.enumeratedGraph (raw64 F) (vertexOrder F) (dartOrder F) labelOrder)) = _
  rw [GraphTables.semantics_ofGraph]
  rfl

theorem table_satisfiable_iff (F : Formula) :
    (GraphTables.semantics (table F)).Satisfiable ↔ F.Satisfiable := by
  rw [table_semantics]
  exact ((raw64 F).satisfiable_reindex (vertexOrder F) (dartOrder F) labelOrder).trans
    (raw64_satisfiable_iff F)

theorem initial_rejection (F : Formula) (unsat : ¬ F.Satisfiable)
    (labeling : Fin (table F).vertices → GraphTables.Label) :
    1 ≤ (GraphTables.semantics (table F)).rejectionCount labeling :=
  ConstraintGraph.rejectionCount_positive _
    (fun h => unsat ((table_satisfiable_iff F).mp h)) labeling

theorem initial_size (F : Formula) :
    (table F).vertices + (table F).darts = F.variables + 7 * F.clauses.length + 2 := by
  rw [table_vertices, table_darts]
  omega

end BinPackingGames.Foundations.PCP.RawInitialTables

namespace BinPackingGames.Foundations.PCP.RawInitialRows

open Target GraphTables RawInitialTables

abbrev Signs := Bool × Bool × Bool
abbrev Names := Nat × Nat × Nat

def clauseSigns {n : Nat} (c : Clause n) : Signs :=
  ((c)[0].positive, (c)[1].positive, (c)[2].positive)

def clauseNames {n : Nat} (c : Clause n) : Names :=
  ((c)[0].variableIndex.val, (c)[1].variableIndex.val, (c)[2].variableIndex.val)

def nameWord (names : Names) : Slot → Nat
  | .first => names.1
  | .second => names.2.1
  | .third => names.2.2

def decodedLabel (a : GraphTables.Label) : InitialGraph.Label :=
  AlphabetRetraction.decode64 (labelOrder.symm a)

def incidencePredicate (signs : Signs) (slot : Slot)
    (clauseLabel variableLabel : InitialGraph.Label) : Bool :=
  InitialGraph.variableValid variableLabel &&
    (((literalValue signs.1 clauseLabel.1 ||
      literalValue signs.2.1 clauseLabel.2.1) ||
      literalValue signs.2.2 clauseLabel.2.2) &&
      decide (answerAt (InitialGraph.toClauseAnswer clauseLabel) slot = variableLabel.1))

def relationPredicate (signs : Signs) (slot : Slot) :
    Bool → GraphTables.Label → GraphTables.Label → Bool
  | false, a, b => incidencePredicate signs slot (decodedLabel a) (decodedLabel b)
  | true, a, b => incidencePredicate signs slot (decodedLabel b) (decodedLabel a)

def relationWordsFor (signs : Signs) (slot : Slot) (orientation : Bool) : List Nat :=
  relationWords (relationOf (relationPredicate signs slot orientation))

@[simp] theorem relationWordsFor_length (signs : Signs) (slot : Slot) (orientation : Bool) :
    (relationWordsFor signs slot orientation).length = 4096 := by
  exact relationWords_length _

def incidenceWords (n i : Nat) (names : Names) (signs : Signs)
    (slot : Slot) (orientation : Bool) : List Nat :=
  [if orientation then nameWord names slot else n + i,
    6 * i + 2 * (slotOrder slot).val + (if orientation then 0 else 1)] ++
      relationWordsFor signs slot orientation

def clauseWords (n i : Nat) (names : Names) (signs : Signs) : List Nat :=
  incidenceWords n i names signs .first false ++
  incidenceWords n i names signs .first true ++
  incidenceWords n i names signs .second false ++
  incidenceWords n i names signs .second true ++
  incidenceWords n i names signs .third false ++
  incidenceWords n i names signs .third true

def dummyWords (n m : Nat) : List Nat :=
  [n + m, 6 * m] ++ List.replicate 4096 1

end BinPackingGames.Foundations.PCP.RawInitialRows

end OAI