Measure latency to the next higher sample

module future_threshold_latency (
  input  logic       clk,
  input  logic       rst_n,
  input  logic       in_valid,
  input  logic       in_last,
  input  logic [7:0] temperature,
  input  logic       out_ready,
  output logic       in_ready,
  output logic       out_valid,
  output logic       out_last,
  output logic [4:0] out_index,
  output logic [5:0] out_distance
);
  typedef enum logic [1:0] {S_INPUT, S_RESOLVE, S_OUTPUT} state_t;
  state_t state_q;

  logic [7:0] stack_temp_q [0:31];
  logic [4:0] stack_index_q [0:31];
  logic [5:0] distance_q [0:31];
  logic [5:0] stack_count_q, frame_count_q;
  logic [4:0] input_index_q, output_index_q;
  logic [7:0] pending_temp_q;
  logic [4:0] pending_index_q;
  logic pending_last_q;
  logic [4:0] top_slot;

  assign top_slot     = stack_count_q - 1'b1;
  assign in_ready     = (state_q == S_INPUT);
  assign out_valid    = (state_q == S_OUTPUT);
  assign out_index    = output_index_q;
  assign out_distance = distance_q[output_index_q];
  assign out_last     = (state_q == S_OUTPUT) &&
                        ({1'b0, output_index_q} + 1'b1 == frame_count_q);

  always_ff @(posedge clk) begin : sample_and_resolve_frame
    // TODO: implement sampled reset; capture one accepted input; resolve at most
    // one stack pop per edge, then push the retained sample; emit/retire the
    // completed frame in index order while holding output across stalls.
  end
endmodule