import Mathlib

structure RingBuffer (T : Type) where
  capacity : Nat
  view : List T

def RingBuffer.is_valid {T} (rb : RingBuffer T) : Prop :=
  rb.capacity > 0 ∧ rb.view.length ≤ rb.capacity

-- Precondition definitions
@[reducible, simp]
def dequeue_precond {T} (rb : RingBuffer T) : Prop :=
  -- !benchmark @start precond
  rb.is_valid ∧ rb.view.length > 0
  -- !benchmark @end precond

-- !benchmark @start auxcode
-- !benchmark @end auxcode

-- Main function definition
-- Returns (value, new_ringbuffer)
def dequeue {T} (rb : RingBuffer T)
    (h_precond : dequeue_precond rb) : T × RingBuffer T :=
  -- !benchmark @start code
  sorry
  -- !benchmark @end code

-- Postcondition definitions
@[reducible, simp]
def dequeue_postcond {T} (rb : RingBuffer T) (result : T × RingBuffer T)
    (_ : dequeue_precond rb) : Prop :=
  -- !benchmark @start postcond
  let (val, new_rb) := result
  new_rb.is_valid ∧
  new_rb.capacity = rb.capacity ∧
  -- Concise & Proof-Free: Old view is (val :: new_view)
  rb.view = val :: new_rb.view
  -- !benchmark @end postcond

-- !benchmark @start lemma
-- !benchmark @end lemma

-- Proof content
theorem dequeue_postcond_satisfied {T} (rb : RingBuffer T)
    (h_precond : dequeue_precond rb) :
    dequeue_postcond rb (dequeue rb h_precond) h_precond := by
  -- !benchmark @start proof
  sorry
  -- !benchmark @end proof