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 enqueue_precond {T} (rb : RingBuffer T) (v : T) : Prop :=
  -- !benchmark @start precond
  rb.is_valid
  -- !benchmark @end precond

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

-- Main function definition
def enqueue {T} (rb : RingBuffer T) (v : T)
    (h_precond : enqueue_precond rb v) : RingBuffer T :=
  -- !benchmark @start code
  sorry
  -- !benchmark @end code

-- Postcondition definitions
@[reducible, simp]
def enqueue_postcond {T} (rb : RingBuffer T) (v : T) (result : RingBuffer T)
    (_ : enqueue_precond rb v) : Prop :=
  -- !benchmark @start postcond
  result.is_valid ∧
  result.capacity = rb.capacity ∧
  (rb.view.length < rb.capacity → result.view = rb.view ++ [v]) ∧
  (rb.view.length = rb.capacity → result.view = rb.view.drop 1 ++ [v])
  -- !benchmark @end postcond

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

-- Proof content
theorem enqueue_postcond_satisfied {T} (rb : RingBuffer T) (v : T)
    (h_precond : enqueue_precond rb v) :
    enqueue_postcond rb v (enqueue rb v h_precond) h_precond := by
  -- !benchmark @start proof
  sorry
  -- !benchmark @end proof