import Semantics.PISTMachine
import Semantics.Functions.BracketedCalculus

namespace Semantics.PBACSSignal

open Semantics.Functions.BracketedCalculus
open Semantics.PISTMachine

/-! # PBACS REV3 — Signal Transport
Neutralized Specification.
Anchored to: linear/RES-2311
-/

/-- 1-bit output symbol. -/
abbrev Symbol := Bool

/-- PBACS Unified State Vector.
    Refactored to align with PISTMachine nomenclature. -/
structure State where
  phi          : UInt32  -- L2 φ-accumulator
  error        : Int32   -- L1 Error accumulator
  tension      : UInt32  -- L4 Tension accumulator
  phase        : Phase   -- L4 PIST Phase sort
  lastSymbol   : Symbol  -- L1 Output symbol
  bracket      : BracketedDIAT -- L5 BracketedDIAT
deriving Repr, BEq, DecidableEq

namespace State

def default : State := {
  phi := 0,
  error := 0,
  tension := 0,
  phase := Phase.grounded,
  lastSymbol := false,
  bracket := BracketedDIAT.encode 0 0 0 0
}

/-- Step 1: Phi increment (Golden Ratio constant). -/
def nextPhi (phi : UInt32) : UInt32 :=
  phi + 106070 -- ≈ 2^32 / φ^2

/-- Step 2: Threshold LUT lookup (simulated via MSB check). -/
def getThreshold (phi : UInt32) : Int32 :=
  if phi >= 0x80000000 then 32768 else -32768

/-- Canonical Update Law (Steps 1-8).
    v_t: Input sample in Q16_16 mapped to Int32. -/
def update (s : State) (v_t : Int32) : State :=
  let v_q := _root_.Semantics.Q16_16.ofInt v_t.toInt
  let phiNext := nextPhi s.phi
  let theta_t := getThreshold phiNext
  
  -- Step 3 & 4: Error Accumulation and Symbol Decision
  let b_t := if theta_t < v_t + s.error then true else false
  let e_next := v_t + s.error - (if b_t then theta_t else 0)
  
  -- Step 5-8: Tension and Phase (Neutralized SLUQ)
  let stress := (e_next).abs
  let tensionNext := (s.tension * 921 + stress.toUInt32 * 103) / 1024
  
  let phaseNext := 
    if tensionNext > 50000 then Phase.seismic
    else if tensionNext > 10000 then Phase.drift
    else Phase.grounded

  -- L5: Update bracket (Constraint-preserving interval)
  let newBracket := BracketedDIAT.encode 
                      (s.bracket.lower + v_q - _root_.Semantics.Q16_16.epsilon)
                      (v_q)
                      (s.bracket.upper + v_q + _root_.Semantics.Q16_16.epsilon)
                      s.bracket.scale

  { phi := phiNext
  , error := e_next
  , tension := tensionNext
  , phase := phaseNext
  , lastSymbol := b_t
  , bracket := newBracket }

end State

end Semantics.PBACSSignal
