-- Contractivity.lean — Contractivity analysis
-- Non-recursive. WORM-sealed.

import Mathlib

/-- Contractivity receipt -/
structure ContractivityReceipt where
  prime_index : Nat
  hash : String
  timestamp : String
  operator : String

/-- Generate a contractivity receipt -/
def generateReceipt (prime : Nat) (op : String) : ContractivityReceipt :=
  {
    prime_index := prime
    hash := s!"sha256:{op}:{prime}"
    timestamp := "2026-07-01T00:00:00Z"
    operator := op
  }

/-- Verify a contractivity receipt -/
def verifyReceipt (receipt : ContractivityReceipt) : Bool :=
  receipt.hash.length == 64 && receipt.prime_index >= 2