#include "imgui_layer.hpp"

#include <string>

#include <imgui.h>
#include <imgui_impl_dx11.h>
#include <imgui_impl_win32.h>

#include "coop/dpi.hpp"
#include "coop/tool_paths.hpp"
#include "ui/app_chrome.hpp"
#include "util/utf8.hpp"

namespace coop {

ImGuiLayer::~ImGuiLayer()
{
	if (initialized_) {
		ImGui_ImplDX11_Shutdown();
		ImGui_ImplWin32_Shutdown();
		ImGui::DestroyContext();
		initialized_ = false;
	}
}

bool ImGuiLayer::init(HWND hwnd, ID3D11Device* device, ID3D11DeviceContext* context)
{
	IMGUI_CHECKVERSION();
	ImGui::CreateContext();
	ImGuiIO& io = ImGui::GetIO();
	// Persist the panel layout next to the executable so window positions/sizes survive
	// restarts. CWD is unreliable when Steam launches us under the donor appid, so anchor
	// to the exe directory. If a layout already exists, tell the chrome not to force the
	// computed default on startup (which would clobber the restored positions).
	const std::wstring ini_w = exe_directory() + L"coop_layout.ini";
	const bool had_layout = GetFileAttributesW(ini_w.c_str()) != INVALID_FILE_ATTRIBUTES;
	// ImGui treats IniFilename as UTF-8 (it converts to wide for _wfopen), so narrow to UTF-8, not
	// the system ANSI code page.
	ini_path_ = narrow(ini_w);
	io.IniFilename = ini_path_.c_str();
	set_layout_persisted(had_layout);

	if (!ImGui_ImplWin32_Init(hwnd)) {
		return false;
	}
	if (!ImGui_ImplDX11_Init(device, context)) {
		return false;
	}
	initialized_ = true;

	// Scale the overlay (font + style) to the monitor the window opened on. The process is
	// per-monitor-DPI-aware (set in wWinMain), so GetDpiForWindow returns that monitor's real DPI.
	apply_dpi(GetDpiForWindow(hwnd));
	return true;
}

void ImGuiLayer::apply_dpi(unsigned dpi)
{
	const float scale = dpi_scale_from(dpi);
	ImGuiIO& io = ImGui::GetIO();

	// Rebuild the font atlas at the DPI-scaled pixel size so ImGui's built-in default font is
	// rasterized crisp at the target size, rather than bitmap-stretched the way io.FontGlobalScale
	// would leave it. scaled_font_px() scales the one named base-size constant.
	io.Fonts->Clear();
	ImFontConfig cfg;
	cfg.SizePixels = scaled_font_px(dpi);
	io.Fonts->AddFontDefault(&cfg);

	// Reset to the base dark theme, then scale spacing/padding/border sizes to match. Resetting
	// first keeps repeated DPI changes from compounding (ScaleAllSizes multiplies the style in place).
	ImGui::StyleColorsDark();
	ImGui::GetStyle().ScaleAllSizes(scale);

	// Drop the DX11 backend's cached font texture so it rebuilds from the new atlas next frame. Before
	// the first frame nothing is built yet, so this is a harmless no-op during init().
	if (initialized_) {
		ImGui_ImplDX11_InvalidateDeviceObjects();
	}
	dpi_scale_ = scale;
}

void ImGuiLayer::set_dpi(unsigned dpi)
{
	if (!initialized_ || dpi_scale_from(dpi) == dpi_scale_) {
		return; // not up yet, or the scale didn't actually change -- skip a needless atlas rebuild
	}
	apply_dpi(dpi);
}

void ImGuiLayer::begin_frame()
{
	ImGui_ImplDX11_NewFrame();
	ImGui_ImplWin32_NewFrame();
	ImGui::NewFrame();
}

void ImGuiLayer::end_frame()
{
	ImGui::Render();
	ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
}

} // namespace coop