# ============================================================================
# drawstats.ludic — every draw a frame makes, by pass, program and kind
# (R3D_DRAWSTATS=<frames>).
#
# Measurement only. Every draw on both backends goes through the five doors in
# gpu.ludic (gpu_draw_mesh, _instanced, _bound_elements, _range, _mesh_indirect);
# each door tallies itself here under the profiler pass that is open (prof_begin)
# and the program that is bound. Nothing about the frame changes.
#
#   R3D_DRAWSTATS=<n>          count n frames (default 60 when not a number)
#   R3D_DRAWSTATS_FROM=<f>     start at render frame f (default 90: streaming settled)
#   R3D_DRAWSTATS_CSV=<path>   the per-row table (default build/drawstats.csv)
#
# The report prints when the window closes, so any run long enough to reach
# f + n frames produces it - a headless shot, a bench, a windowed walk.
#
# An indirect draw is one API call carrying n command records; its "instances"
# column is the record count, and whether the GPU's culling emptied a record is
# not known here (see R3D_VK_PROF for the Vulkan side's own count).
# ============================================================================

const DS_MESH: int = 0
const DS_INSTANCED: int = 1
const DS_PATCH: int = 2
const DS_RANGE: int = 3
const DS_INDIRECT: int = 4
const DS_KINDS: int = 5


# passes, in the order the frame first opens them

# rows: (pass, program, kind)

@alloc_ok("profiling and statistics, only under R3D_PROF / R3D_DRAWSTATS")
function ds_enabled(render3d_st: mut Render3dState) -> bool {
  if render3d_st.ds_on < 0 {
    render3d_st.ds_on = 0
    if r3d_env_has(render3d_st, "R3D_DRAWSTATS") {
      render3d_st.ds_on = 1
      render3d_st.ds_frames = Text.to_int(r3d_env(render3d_st, "R3D_DRAWSTATS"))
      if render3d_st.ds_frames < 2 { render3d_st.ds_frames = 60 }
      if r3d_env_has(render3d_st, "R3D_DRAWSTATS_FROM") { render3d_st.ds_from = Text.to_int(r3d_env(render3d_st, "R3D_DRAWSTATS_FROM")) }
      render3d_st.ds_pass_names = new []pointer;  render3d_st.ds_pass_prog = new []long;  render3d_st.ds_pass_tex = new []long
      render3d_st.ds_row_pass = new []int;  render3d_st.ds_row_prog = new []int;  render3d_st.ds_row_kind = new []int
      render3d_st.ds_row_draws = new []long;  render3d_st.ds_row_inst = new []long;  render3d_st.ds_row_idx = new []long
      ds_set_pass(render3d_st, render3d_st.ds_outside)
    }
  }
  return render3d_st.ds_on == 1
}

# the profiler's pass boundaries (prof_begin / prof_end), whether or not R3D_PROF is on
@alloc_ok("profiling and statistics, only under R3D_PROF / R3D_DRAWSTATS")
function ds_set_pass(render3d_st: mut Render3dState, name: pointer) -> void {
  if render3d_st.ds_on != 1 { return }
  render3d_st.ds_last = -1
  var i = 0
  while i < len(render3d_st.ds_pass_names) {
    if render3d_st.ds_pass_names[i] == name { render3d_st.ds_pass_i = i;  return }
    i += 1
  }
  push(render3d_st.ds_pass_names, name);  push(render3d_st.ds_pass_prog, 0);  push(render3d_st.ds_pass_tex, 0)
  render3d_st.ds_pass_i = len(render3d_st.ds_pass_names) - 1
}

# once per render frame, before any of its work (prof_gen_frame)
function ds_frame(render3d_st: mut Render3dState) -> void {
  if not ds_enabled(render3d_st) { return }
  render3d_st.ds_frame_no += 1
  ds_set_pass(render3d_st, render3d_st.ds_outside)
  if render3d_st.ds_frame_no == render3d_st.ds_from {
    render3d_st.ds_counting = true
    print(`r3d: drawstats counting frames {render3d_st.ds_from}..{render3d_st.ds_from + render3d_st.ds_frames - 1}`)
  }
  if render3d_st.ds_frame_no == render3d_st.ds_from + render3d_st.ds_frames {
    render3d_st.ds_counting = false
    ds_report(render3d_st)
  }
}

@alloc_ok("profiling and statistics, only under R3D_PROF / R3D_DRAWSTATS")
function ds_draw(render3d_st: mut Render3dState, kind: int, instances: int, indices: int) -> void {
  if render3d_st.ds_on != 1 or not render3d_st.ds_counting { return }
  let p = render3d_st.gpu_prog_cur
  var r = render3d_st.ds_last
  if r < 0 or render3d_st.ds_row_prog[r] != p or render3d_st.ds_row_kind[r] != kind or render3d_st.ds_row_pass[r] != render3d_st.ds_pass_i {
    r = -1
    var i = 0
    while r < 0 and i < len(render3d_st.ds_row_pass) {
      if render3d_st.ds_row_pass[i] == render3d_st.ds_pass_i and render3d_st.ds_row_prog[i] == p and render3d_st.ds_row_kind[i] == kind { r = i }
      i += 1
    }
    if r < 0 {
      push(render3d_st.ds_row_pass, render3d_st.ds_pass_i);  push(render3d_st.ds_row_prog, p);  push(render3d_st.ds_row_kind, kind)
      push(render3d_st.ds_row_draws, 0);  push(render3d_st.ds_row_inst, 0);  push(render3d_st.ds_row_idx, 0)
      r = len(render3d_st.ds_row_pass) - 1
    }
    render3d_st.ds_last = r
  }
  render3d_st.ds_row_draws[r] = render3d_st.ds_row_draws[r] + 1
  render3d_st.ds_row_inst[r] = render3d_st.ds_row_inst[r] + instances
  render3d_st.ds_row_idx[r] = render3d_st.ds_row_idx[r] + indices
}

function ds_program_change(render3d_st: mut Render3dState, from: int, to: int) -> void {
  if render3d_st.ds_on != 1 or not render3d_st.ds_counting or from == to { return }
  render3d_st.ds_pass_prog[render3d_st.ds_pass_i] = render3d_st.ds_pass_prog[render3d_st.ds_pass_i] + 1
}
function ds_tex_bind(render3d_st: mut Render3dState) -> void {
  if render3d_st.ds_on != 1 or not render3d_st.ds_counting { return }
  render3d_st.ds_pass_tex[render3d_st.ds_pass_i] = render3d_st.ds_pass_tex[render3d_st.ds_pass_i] + 1
}

function ds_kind_name(k: int) -> pointer {
  if k == DS_MESH { return "mesh" }
  if k == DS_INSTANCED { return "instanced" }
  if k == DS_PATCH { return "terrain patch" }
  if k == DS_RANGE { return "overlay range" }
  return "indirect"
}
# a per-frame mean with one decimal
@alloc_ok("the draw-count report: printed once, at the end of a run that asked for it")
function ds_per(render3d_st: Render3dState, v: long) -> string {
  let x = (v * 10) / render3d_st.ds_frames
  return `{string(x / 10)}.{string(x % 10)}`
}
function ds_backend(render3d_st: Render3dState) -> pointer {
  if render3d_st.gpu_kind == GPU_VK { return "vulkan" }
  return "opengl"
}

@alloc_ok("profiling and statistics, only under R3D_PROF / R3D_DRAWSTATS")
function ds_report(render3d_st: mut Render3dState) -> void {
  let n_rows = len(render3d_st.ds_row_pass)
  let n_pass = len(render3d_st.ds_pass_names)
  var total: long = 0
  let by_kind = new []long
  for k in 0 .. DS_KINDS { push(by_kind, 0) }
  let pass_draws = new []long
  let pass_inst = new []long
  for s in 0 .. n_pass { push(pass_draws, 0);  push(pass_inst, 0) }
  for r in 0 .. n_rows {
    total = total + render3d_st.ds_row_draws[r]
    by_kind[render3d_st.ds_row_kind[r]] = by_kind[render3d_st.ds_row_kind[r]] + render3d_st.ds_row_draws[r]
    pass_draws[render3d_st.ds_row_pass[r]] = pass_draws[render3d_st.ds_row_pass[r]] + render3d_st.ds_row_draws[r]
    pass_inst[render3d_st.ds_row_pass[r]] = pass_inst[render3d_st.ds_row_pass[r]] + render3d_st.ds_row_inst[r]
  }
  print("")
  print(`draw calls per frame ({ds_backend(render3d_st)}, {gl_width()}x{gl_height()}, mean of {render3d_st.ds_frames} frames from {render3d_st.ds_from}): {ds_per(render3d_st, total)}`)
  var kinds = ""
  for k in 0 .. DS_KINDS { kinds = kinds + `  {ds_kind_name(k)} {ds_per(render3d_st, by_kind[k])}` }
  print(`  by kind:{kinds}`)
  print("")
  print("  pass                        draws   instances   program changes   texture binds")
  for s in 0 .. n_pass {
    print(`  {Text.pad_right(render3d_st.ds_pass_names[s], 24)} {Text.pad_left(ds_per(render3d_st, pass_draws[s]), 9)} {Text.pad_left(ds_per(render3d_st, pass_inst[s]), 11)} {Text.pad_left(ds_per(render3d_st, render3d_st.ds_pass_prog[s]), 17)} {Text.pad_left(ds_per(render3d_st, render3d_st.ds_pass_tex[s]), 15)}`)
  }
  # rows by draws, most first
  let order = new []int
  for r in 0 .. n_rows { push(order, r) }
  var a = 1
  while a < n_rows {
    let v = order[a]
    var b = a - 1
    while b >= 0 and render3d_st.ds_row_draws[order[b]] < render3d_st.ds_row_draws[v] { order[b + 1] = order[b];  b -= 1 }
    order[b + 1] = v
    a += 1
  }
  print("")
  print("  the 40 largest rows (pass / kind / program):")
  print("      draws   instances      indices  pass                      kind            program")
  var shown = 0
  while shown < 40 and shown < n_rows {
    let r = order[shown]
    print(`  {Text.pad_left(ds_per(render3d_st, render3d_st.ds_row_draws[r]), 9)} {Text.pad_left(ds_per(render3d_st, render3d_st.ds_row_inst[r]), 11)} {Text.pad_left(ds_per(render3d_st, render3d_st.ds_row_idx[r]), 12)}  {Text.pad_right(render3d_st.ds_pass_names[render3d_st.ds_row_pass[r]], 24)}  {Text.pad_right(ds_kind_name(render3d_st.ds_row_kind[r]), 14)}  {gpu_program_key(render3d_st, render3d_st.ds_row_prog[r])}`)
    shown += 1
  }
  var path = "build/drawstats.csv"
  if r3d_env_has(render3d_st, "R3D_DRAWSTATS_CSV") { path = r3d_env(render3d_st, "R3D_DRAWSTATS_CSV") }
  let f = file_open(path, "wb")
  if f == null { print(`r3d: drawstats could not write {path}`);  return }
  let head = "backend,width,height,frames,pass,kind,program,draws_per_frame,instances_per_frame,indices_per_frame,pass_program_changes_per_frame,pass_texture_binds_per_frame\n"
  file_write(f, head, len(head))
  for i in 0 .. n_rows {
    let r = order[i]
    let s = render3d_st.ds_row_pass[r]
    let line = `{ds_backend(render3d_st)},{gl_width()},{gl_height()},{render3d_st.ds_frames},"{render3d_st.ds_pass_names[s]}",{ds_kind_name(render3d_st.ds_row_kind[r])},"{gpu_program_key(render3d_st, render3d_st.ds_row_prog[r])}",{ds_per(render3d_st, render3d_st.ds_row_draws[r])},{ds_per(render3d_st, render3d_st.ds_row_inst[r])},{ds_per(render3d_st, render3d_st.ds_row_idx[r])},{ds_per(render3d_st, render3d_st.ds_pass_prog[s])},{ds_per(render3d_st, render3d_st.ds_pass_tex[s])}\n`
    file_write(f, line, len(line))
  }
  file_close(f)
  print(`  wrote {path} ({n_rows} rows)`)
}