internal
void accum_dt_ms(Delta_Time_Accum &accum, f32 dt)
{
	if (accum.count < accum.max) {
		assert(accum.start == 0);
		accum.base[accum.count++] = dt;
	} else {
		accum.base[accum.start++] = dt;
		if (accum.start == accum.max)
			accum.start = 0;
	}
}

internal
f32 calc_avg_dt_ms(const Delta_Time_Accum &accum)
{
	f32 res = 0;
	for (u16 idx = 0; idx < accum.count; ++idx)
		res += accum.base[idx];
	if (accum.count) res /= accum.count;
	return res;
}

internal
String8 to_pretty_size(Arena *arena, u64 bytes)
{
	if (bytes >= GiB(1)) return push_str8f(arena, "%.1f GiB", (f32)bytes / GiB(1));
	if (bytes >= MiB(1)) return push_str8f(arena, "%.1f MiB", (f32)bytes / MiB(1));
	if (bytes >= KiB(1)) return push_str8f(arena, "%.1f KiB", (f32)bytes / KiB(1));
	return push_str8f(arena, "%zu B", bytes);
}

internal
u32 mem_edit_bg_color_fn(const u8 *, u64 off, void *user_data)
{
  App_State *app = reinterpret_cast<App_State *>(user_data);
  const RNTuple_Data &rdata = app->rndata;
  u64 rblob_sz = rdata.rblob_header_size;

  off += app->vsettings.base_display_addr;

#define COL(c) (ImColor((c)[0], (c)[1], (c)[2]))
  // Handle pages
  // fast case: offset from same page info as previous
  if (off < app->last_pinfo->range.end()) return COL(app->vsettings.col_page);

  // still fast case: offset from next page info
  if (app->last_pinfo->next) app->last_pinfo = app->last_pinfo->next;
  if (app->last_pinfo && app->last_pinfo->range.start <= off && off <= app->last_pinfo->range.end())
    return COL(app->vsettings.col_page);

  if (off <= rdata.root_file_header_size) return COL(app->vsettings.col_tfile);
  if (rdata.rng_anchor_key.start <= off && off <= rdata.rng_anchor_key.end()) return COL(app->vsettings.col_key);
  if (rdata.rng_header.start - rblob_sz <= off && off <= rdata.rng_header.start) return COL(app->vsettings.col_key);
  if (rdata.rng_footer.start - rblob_sz <= off && off <= rdata.rng_footer.start) return COL(app->vsettings.col_key);
  if (rdata.rng_anchor.start <= off && off <= rdata.rng_anchor.end()) return COL(app->vsettings.col_anchor);
  if (rdata.rng_header.start <= off && off <= rdata.rng_header.end()) return COL(app->vsettings.col_header);
  if (rdata.rng_footer.start <= off && off <= rdata.rng_footer.end()) return COL(app->vsettings.col_footer);

  // Slow page group lookup, hopefully rare (ideally only done once)
  // printf("%lu vs %lu\n", off, rdata.page_groups[rdata.n_page_groups - 1].range.end());
  for (Page_Info_Chunk *chunk = rdata.page_chunks; chunk; chunk = chunk->next) {
    if (chunk->range.start <= off && off <= chunk->range.end()) {
      printf("slow path for 0x%lX (last pinfo: 0x%lX - 0x%lX)\n", off, app->last_pinfo->range.start, app->last_pinfo->range.end());
      for (u64 group_idx = chunk->first_group; group_idx < rdata.n_page_groups; ++group_idx) {
        const Page_Info_Group &group = rdata.page_groups[group_idx];
        if (off < group.range.start || off > group.range.end()) 
          continue;

        for (Page_Info_Node *pinfo = group.first; pinfo; pinfo = pinfo->next) {
          if (pinfo->range.start <= off && off <= pinfo->range.end()) {
            app->last_pinfo = pinfo;
            if (pinfo->range.start == off) return COL(app->vsettings.col_page_start);
            else return COL(app->vsettings.col_page);
          }
        }
      }

      fprintf(stderr, "Offset 0x%lX is in chunk 0x%lX - 0x%lX, but found in no page_info range!\n", 
              off, chunk->range.start, chunk->range.end());
      assert(false);
    }
  }
#undef COL

  return IM_COL32(0, 0, 0, 0);
}

internal
MemoryEditor make_memory_editor(App_State &app)
{
  MemoryEditor mem_edit;
  // mem_edit.ReadOnly = true;
  mem_edit.Cols = 32;
  mem_edit.OptShowDataPreview = true;
  mem_edit.BgColorFn = mem_edit_bg_color_fn;
  mem_edit.BgColorFnUserData = &app;
  return mem_edit;
}

internal
Viewer_Settings make_viewer_settings()
{
  Viewer_Settings settings {};
#define COL(c, r, g, b) settings.c[0] = r/255.0, settings.c[1] = g/255.0, settings.c[2] = b/255.0
  COL(col_anchor, 150, 150, 0);
  COL(col_header, 150, 0, 50);
  COL(col_footer, 50, 0, 150);
  COL(col_key,    0, 100, 50);
  COL(col_tfile,  90, 90, 90);
  COL(col_page,   125, 0, 125);
  COL(col_page_start, 75, 0, 75);
#undef COL
  return settings;
}

internal
void update_and_render(Arena *arena, App_State &app, f32 delta_time_ms)
{
  accum_dt_ms(app.delta_time_accum, delta_time_ms);
  
  ImGui::SetNextWindowPos({ 0, 0 });
  ImGui::SetNextWindowSize({ (f32)app.win_data.width, (f32)app.win_data.height });

  Temp scratch = temp_begin(arena);
  defer { temp_end(scratch); };

  const u64 inspected_max_size = 2048;
  u64 text_buf_size = min(app.inspected_file_size * 2, inspected_max_size);
  char *text_buf = arena_push_array_nozero<char>(scratch.arena, text_buf_size + 1);
  // Convert file content to human readable
  // @Speed: maybe do this only when the file changes
  for (u64 i = 0; i < text_buf_size / 2; ++i)
    sprintf(&text_buf[2 * i], "%02X", app.inspected_fmem[i]);
  text_buf[text_buf_size] = 0;
  
  const auto main_win_flags = ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoDecoration;
  if (ImGui::Begin("main", nullptr, main_win_flags)) {
        
    String8 ntpl_desc = rntuple_description(scratch.arena, app.rndata);
    ImGui::Text("RNTuple '%s' (%s) from file \"%s\"", app.ntpl_name, ntpl_desc.c(), app.inspected_fname);

    // Draw stats
    {
      ImGui::SameLine();

      f32 avg_dt = calc_avg_dt_ms(app.delta_time_accum);

      String8 mem_used = to_pretty_size(scratch.arena, arena->mem_used);
      String8 mem_peak = to_pretty_size(scratch.arena, arena->mem_peak_used);
      String8 stat_txt = push_str8f(scratch.arena, "mem used: %s (peak: %s) | avg dt: %.1f", 
                                    mem_used.c(), mem_peak.c(), avg_dt);

      f32 pos_x = (ImGui::GetCursorPosX() + ImGui::GetColumnWidth() - ImGui::CalcTextSize(stat_txt.c()).x 
        - ImGui::GetScrollX() - 2 * ImGui::GetStyle().ItemSpacing.x);
      if (pos_x > ImGui::GetCursorPosX())
        ImGui::SetCursorPosX(pos_x);

      ImGui::Text("%s", stat_txt.c());
    }

    ImGui::Separator();

    // Draw main content
    {
      static MemoryEditor mem_edit = make_memory_editor(app);
      ImGui::BeginTable("Hex View", 2);

      ImGui::TableNextColumn();

      assert(app.vsettings.base_display_addr < app.inspected_file_size);
      void *content = app.inspected_fmem + app.vsettings.base_display_addr;
      u64 content_size = app.inspected_file_size - app.vsettings.base_display_addr;
      app.last_pinfo = &invalid_pinfo;
      mem_edit.DrawContents(content, content_size, app.vsettings.base_display_addr);

      ImGui::TableNextColumn();
      ImGuiColorEditFlags flags =  ImGuiColorEditFlags_NoInputs|ImGuiColorEditFlags_NoLabel;

      ImGui::ColorEdit3("_TFile",          app.vsettings.col_tfile,  flags);
      ImGui::SameLine(); 
      if (ImGui::Button("TFile")) app.vsettings.base_display_addr = 0;

      ImGui::ColorEdit3("_RNTuple Anchor", app.vsettings.col_anchor, flags);
      ImGui::SameLine(); 
      if (ImGui::Button("RNTuple Anchor")) app.vsettings.base_display_addr = app.rndata.rng_anchor.start;

      ImGui::ColorEdit3("_RNTuple Header", app.vsettings.col_header, flags);
      ImGui::SameLine(); 
      if (ImGui::Button("RNTuple Header")) app.vsettings.base_display_addr = app.rndata.rng_header.start;

      ImGui::ColorEdit3("_RNTuple Footer", app.vsettings.col_footer, flags);
      ImGui::SameLine(); 
      if (ImGui::Button("RNTuple Footer")) app.vsettings.base_display_addr = app.rndata.rng_footer.start;

      ImGui::ColorEdit3("_TKey Header",    app.vsettings.col_key,    flags);
      ImGui::SameLine(); 
      if (ImGui::Button("TKey Header"))    {} // TODO app.vsettings.base_display_addr = app.rndatarng_footer.start;

      ImGui::Separator();
      ImGui::Text("Num pages: %lu", app.rndata.n_pages);
      ImGui::Text("Num elements: %lu", app.rndata.n_elems);

      ImGui::EndTable();
    }

    ImGui::End();
  }
}