# steady.ludic - render3d allocates nothing in its steady state: a buffer released and made again
# (what a streamed or grown buffer does every few frames) and a whole frame, drawn over and over,
# leave malloc's live bytes where they were. Prints STEADY OK. The heap is read on the Mac
# (Vk.heap_bytes); elsewhere it reads 0 and the check passes on the run alone.
#
#   bin/ludic build examples/rendering/steady.ludic --headless && ./build/steady_headless
program Steady {
  numbers float
  import "ludic.render3d/r3d.ludic"

  property Marker { on: int = 1 }
  model Anchor { Marker }

  function scene_draw(render3d_st: mut Render3dState) -> void { }
  function scene_draw_casters(render3d_st: mut Render3dState, light_vp: floats) -> void { }
  function stream_fill(s: Stream, cx: int, cz: int, band: int) -> void { }

  # bytes gained by the heap over n rounds of the buffer path, after a warm-up of its own
  function buffer_rounds(render3d_st: mut Render3dState, b: int, n: int) -> long {
    let before = Vk.heap_bytes()
    for i in 0 .. n {
      gpu_buffer_upload(render3d_st, b, 4096 + (i % 16) * 4096, null, GPU_DYNAMIC)
      gpu_buffer_free(render3d_st, b)
    }
    return Vk.heap_bytes() - before
  }
  function frame_rounds(render3d_st: mut Render3dState, n: int) -> long {
    let before = Vk.heap_bytes()
    for i in 0 .. n {
      r3d_frame(render3d_st, float(i) / 60.0)
      r3d_present(render3d_st)
    }
    return Vk.heap_bytes() - before
  }

  handler Boot(render3d_st: mut Render3dState) phase Start {
    spawn Anchor {}
    r3d_on_draw(render3d_st, fn scene_draw)
    r3d_on_casters(render3d_st, fn scene_draw_casters)
    r3d_on_stream_fill(render3d_st, fn stream_fill)
    r3d_plate_mode(render3d_st, true)
    render3d_st.r3d_sky_path = "packages/ludic.lab/plate/sky.hdr"
    if not r3d_init(render3d_st, 320, 180, "Steady") {
      quit()
      return
    }
    let b = gpu_buffer_new(render3d_st)
    buffer_rounds(render3d_st, b, 500)
    let grew_b = buffer_rounds(render3d_st, b, 5000)
    frame_rounds(render3d_st, 120)
    let grew_f = frame_rounds(render3d_st, 600)
    print(`steady: the buffer path gained {grew_b} bytes over 5000 rounds, the frame {grew_f} over 600`)
    # a few KB of slack for what the system's own libraries keep (Metal's caches, the allocator)
    var ok = grew_b < 16384
    if not ok { print("steady: FAILED - releasing and making a buffer again leaves memory behind") }
    if grew_f >= 65536 {
      ok = false
      print("steady: FAILED - a frame leaves memory behind")
    }
    if ok { print("STEADY OK") } else { print("STEADY FAILED") }
    quit()
  }

  handler Present(render3d_st: mut Render3dState) phase Render {
    r3d_present(render3d_st)
  }
}