#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <filesystem>
#include <string>

#include <imgui.h>
#include <SDL.h>
#include <SDL_opengl.h>
#include <backends/imgui_impl_opengl3.h>
#include <backends/imgui_impl_sdl2.h>

#include "ImGuiFrontend.h"
#include "Command.h"
#include "Editor.h"
#include "GUIConfig.h"
#include "GUITheme.h"
#include "fonts/Font.h" // embedded default font (DefaultFont)
#include "fonts/FontRegistry.h"
#include "fonts/IosevkaExtended.h"
#include "syntax/HighlighterRegistry.h"
#include "syntax/NullHighlighter.h"


#ifndef KTE_FONT_SIZE
#define KTE_FONT_SIZE 16.0f
#endif

static auto kGlslVersion = "#version 150"; // GL 3.2 core (macOS compatible)

// ---------------------------------------------------------------------------
// Helpers shared between Init and OpenNewWindow_
// ---------------------------------------------------------------------------

static void
apply_syntax_to_buffer(Buffer *b, const GUIConfig &cfg)
{
	if (!b)
		return;
	if (cfg.syntax) {
		b->SetSyntaxEnabled(true);
		b->EnsureHighlighter();
		if (auto *eng = b->Highlighter()) {
			if (!eng->HasHighlighter()) {
				std::string first_line;
				const auto &rows = b->Rows();
				if (!rows.empty())
					first_line = static_cast<std::string>(rows[0]);
				std::string ft = kte::HighlighterRegistry::DetectForPath(
					b->Filename(), first_line);
				if (!ft.empty()) {
					eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
					b->SetFiletype(ft);
					eng->InvalidateFrom(0);
				} else {
					eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
					b->SetFiletype("");
					eng->InvalidateFrom(0);
				}
			}
		}
	} else {
		b->SetSyntaxEnabled(false);
	}
}


// Update editor logical rows/cols from current ImGui metrics for a given display size.
static void
update_editor_dimensions(Editor &ed, float disp_w, float disp_h)
{
	float row_h = ImGui::GetTextLineHeightWithSpacing();
	float ch_w  = ImGui::CalcTextSize("M").x;
	if (row_h <= 0.0f)
		row_h = 16.0f;
	if (ch_w <= 0.0f)
		ch_w = 8.0f;

	const float pad_x = 6.0f;
	const float pad_y = 6.0f;

	float wanted_bar_h   = ImGui::GetFrameHeight();
	float total_avail_h  = std::max(0.0f, disp_h - 2.0f * pad_y);
	float actual_avail_h = std::floor((total_avail_h - wanted_bar_h) / row_h) * row_h;

	auto content_rows = static_cast<std::size_t>(std::max(0.0f, std::floor(actual_avail_h / row_h)));
	std::size_t rows  = content_rows + 1;

	float avail_w    = std::max(0.0f, disp_w - 2.0f * pad_x);
	std::size_t cols = static_cast<std::size_t>(std::max(1.0f, std::floor(avail_w / ch_w)));

	if (rows != ed.Rows() || cols != ed.Cols()) {
		ed.SetDimensions(rows, cols);
	}
}


bool
GUIFrontend::Init(int &argc, char **argv, Editor &ed)
{
	(void) argc;
	(void) argv;

	// Load GUI configuration (fullscreen, columns/rows, font size, theme, background)
	config_ = GUIConfig::Load();

	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) != 0) {
		return false;
	}

	// GL attributes for core profile
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
	SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);

	// Compute desired window size from config
	Uint32 win_flags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;

	int init_w = 1280, init_h = 800;
	if (config_.fullscreen) {
		SDL_Rect usable{};
		if (SDL_GetDisplayUsableBounds(0, &usable) == 0) {
			init_w = usable.w;
			init_h = usable.h;
		}
#if !defined(__APPLE__)
		win_flags |= SDL_WINDOW_FULLSCREEN_DESKTOP;
#endif
	} else {
		int w = config_.columns * static_cast<int>(config_.font_size);
		int h = config_.rows * static_cast<int>(config_.font_size * 1.2);
		SDL_Rect usable{};
		if (SDL_GetDisplayUsableBounds(0, &usable) == 0) {
			w = std::min(w, usable.w);
			h = std::min(h, usable.h);
		}
		init_w = std::max(320, w);
		init_h = std::max(200, h);
	}

	SDL_SetHint(SDL_HINT_VIDEO_ALLOW_SCREENSAVER, "1");
	SDL_Window *win = SDL_CreateWindow(
		"kge - kyle's graphical editor " KTE_VERSION_STR,
		SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
		init_w, init_h,
		win_flags);
	if (!win) {
		return false;
	}

	SDL_EnableScreenSaver();

#if defined(__APPLE__)
	if (config_.fullscreen) {
		SDL_Rect usable{};
		if (SDL_GetDisplayUsableBounds(0, &usable) == 0) {
			SDL_SetWindowPosition(win, usable.x, usable.y);
		}
	}
#endif

	SDL_GLContext gl_ctx = SDL_GL_CreateContext(win);
	if (!gl_ctx) {
		SDL_DestroyWindow(win);
		return false;
	}
	SDL_GL_MakeCurrent(win, gl_ctx);
	SDL_GL_SetSwapInterval(1); // vsync

	IMGUI_CHECKVERSION();
	ImGui::CreateContext();
	ImGuiIO &io = ImGui::GetIO();

	// Set custom ini filename path to ~/.config/kte/imgui.ini
	if (const char *home = std::getenv("HOME")) {
		namespace fs = std::filesystem;
		fs::path config_dir = fs::path(home) / ".config" / "kte";
		std::error_code ec;
		if (!fs::exists(config_dir)) {
			fs::create_directories(config_dir, ec);
		}
		if (fs::exists(config_dir)) {
			static std::string ini_path = (config_dir / "imgui.ini").string();
			io.IniFilename              = ini_path.c_str();
		}
	}

	io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
	io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
	ImGui::StyleColorsDark();

	if (config_.background == "light")
		kte::SetBackgroundMode(kte::BackgroundMode::Light);
	else
		kte::SetBackgroundMode(kte::BackgroundMode::Dark);
	kte::ApplyThemeByName(config_.theme);

	apply_syntax_to_buffer(ed.CurrentBuffer(), config_);

	if (!ImGui_ImplSDL2_InitForOpenGL(win, gl_ctx))
		return false;
	if (!ImGui_ImplOpenGL3_Init(kGlslVersion))
		return false;

	// Cache initial window size
	int w, h;
	SDL_GetWindowSize(win, &w, &h);
	init_w = w;
	init_h = h;

#if defined(__APPLE__)
	if (w > 1 && h > 1) {
		SDL_SetWindowSize(win, w - 1, h - 1);
		SDL_SetWindowSize(win, w, h);
		SDL_GetWindowSize(win, &w, &h);
		init_w = w;
		init_h = h;
	}
#endif

	// Install embedded fonts
	kte::Fonts::InstallDefaultFonts();
	if (!kte::Fonts::FontRegistry::Instance().LoadFont(config_.font, (float) config_.font_size)) {
		LoadGuiFont_(nullptr, (float) config_.font_size);
		kte::Fonts::FontRegistry::Instance().RequestLoadFont("default", (float) config_.font_size);
		std::string n;
		float s = 0.0f;
		if (kte::Fonts::FontRegistry::Instance().ConsumePendingFontRequest(n, s)) {
			kte::Fonts::FontRegistry::Instance().LoadFont(n, s);
		}
	}

	// Build primary WindowState
	auto ws    = std::make_unique<WindowState>();
	ws->window = win;
	ws->gl_ctx = gl_ctx;
	ws->width  = init_w;
	ws->height = init_h;
	// The primary window's editor IS the editor passed in from main; we don't
	// use ws->editor for the primary — instead we keep a pointer to &ed.
	// We store a sentinel: window index 0 uses the external editor reference.
	// To keep things simple, attach input to the passed-in editor.
	ws->input.Attach(&ed);
	windows_.push_back(std::move(ws));

	return true;
}


bool
GUIFrontend::OpenNewWindow_(Editor &primary)
{
	SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);

	Uint32 win_flags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;
	int w            = windows_[0]->width;
	int h            = windows_[0]->height;

	SDL_Window *win = SDL_CreateWindow(
		"kge - kyle's graphical editor " KTE_VERSION_STR,
		SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
		w, h,
		win_flags);
	if (!win)
		return false;

	SDL_GLContext gl_ctx = SDL_GL_CreateContext(win);
	if (!gl_ctx) {
		SDL_DestroyWindow(win);
		return false;
	}
	SDL_GL_MakeCurrent(win, gl_ctx);
	SDL_GL_SetSwapInterval(1);

	// Secondary windows share the ImGui context already created in Init.
	// We need to init the SDL2/OpenGL backends for this new window.
	// ImGui_ImplSDL2 supports multiple windows via SDL_GetWindowID checks.
	ImGui_ImplOpenGL3_Init(kGlslVersion);

	auto ws    = std::make_unique<WindowState>();
	ws->window = win;
	ws->gl_ctx = gl_ctx;
	ws->width  = w;
	ws->height = h;

	// Secondary editor shares the primary's buffer list
	ws->editor.SetSharedBuffers(&primary.Buffers());
	ws->editor.SetDimensions(primary.Rows(), primary.Cols());
	ws->input.Attach(&ws->editor);

	windows_.push_back(std::move(ws));

	// Restore primary GL context as current
	SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
	return true;
}


void
GUIFrontend::Step(Editor &ed, bool &running)
{
	// --- Event processing ---
	SDL_Event e;
	while (SDL_PollEvent(&e)) {
		ImGui_ImplSDL2_ProcessEvent(&e);

		// Determine which window this event belongs to
		Uint32 event_win_id = 0;
		switch (e.type) {
		case SDL_WINDOWEVENT:
			event_win_id = e.window.windowID;
			break;
		case SDL_KEYDOWN:
		case SDL_KEYUP:
			event_win_id = e.key.windowID;
			break;
		case SDL_TEXTINPUT:
			event_win_id = e.text.windowID;
			break;
		case SDL_MOUSEBUTTONDOWN:
		case SDL_MOUSEBUTTONUP:
			event_win_id = e.button.windowID;
			break;
		case SDL_MOUSEWHEEL:
			event_win_id = e.wheel.windowID;
			break;
		default:
			break;
		}

		if (e.type == SDL_QUIT) {
			running = false;
			break;
		}

		if (e.type == SDL_WINDOWEVENT) {
			if (e.window.event == SDL_WINDOWEVENT_CLOSE) {
				// Mark the window as dead; primary window close = quit
				for (std::size_t i = 0; i < windows_.size(); ++i) {
					if (SDL_GetWindowID(windows_[i]->window) == e.window.windowID) {
						if (i == 0) {
							running = false;
						} else {
							windows_[i]->alive = false;
						}
						break;
					}
				}
			} else if (e.window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
				for (auto &ws: windows_) {
					if (SDL_GetWindowID(ws->window) == e.window.windowID) {
						ws->width  = e.window.data1;
						ws->height = e.window.data2;
						break;
					}
				}
			}
		}

		// Route input events to the correct window's input handler
		if (event_win_id != 0) {
			// Primary window (index 0) uses the external editor &ed
			if (windows_.size() > 0 &&
			    SDL_GetWindowID(windows_[0]->window) == event_win_id) {
				windows_[0]->input.ProcessSDLEvent(e);
			} else {
				for (std::size_t i = 1; i < windows_.size(); ++i) {
					if (SDL_GetWindowID(windows_[i]->window) == event_win_id) {
						windows_[i]->input.ProcessSDLEvent(e);
						break;
					}
				}
			}
		}
	}

	if (!running)
		return;

	// --- Apply pending font change ---
	{
		std::string fname;
		float fsize = 0.0f;
		if (kte::Fonts::FontRegistry::Instance().ConsumePendingFontRequest(fname, fsize)) {
			if (!fname.empty() && fsize > 0.0f) {
				kte::Fonts::FontRegistry::Instance().LoadFont(fname, fsize);
				ImGui_ImplOpenGL3_DestroyFontsTexture();
				ImGui_ImplOpenGL3_CreateFontsTexture();
			}
		}
	}

	// --- Step each window ---
	// We iterate by index because OpenNewWindow_ may append to windows_.
	for (std::size_t wi = 0; wi < windows_.size(); ++wi) {
		WindowState &ws = *windows_[wi];
		if (!ws.alive)
			continue;

		Editor &wed = (wi == 0) ? ed : ws.editor;

		SDL_GL_MakeCurrent(ws.window, ws.gl_ctx);

		// Start a new ImGui frame
		ImGui_ImplOpenGL3_NewFrame();
		ImGui_ImplSDL2_NewFrame(ws.window);
		ImGui::NewFrame();

		// Update editor dimensions
		{
			ImGuiIO &io  = ImGui::GetIO();
			float disp_w = io.DisplaySize.x > 0 ? io.DisplaySize.x : static_cast<float>(ws.width);
			float disp_h = io.DisplaySize.y > 0 ? io.DisplaySize.y : static_cast<float>(ws.height);
			update_editor_dimensions(wed, disp_w, disp_h);
		}

		// Allow deferred opens
		wed.ProcessPendingOpens();

		// Drain input queue
		for (;;) {
			MappedInput mi;
			if (!ws.input.Poll(mi))
				break;
			if (mi.hasCommand) {
				if (mi.id == CommandId::NewWindow) {
					// Open a new window; handled after this loop
					wed.SetNewWindowRequested(true);
				} else {
					const std::string before = wed.KillRingHead();
					Execute(wed, mi.id, mi.arg, mi.count);
					const std::string after = wed.KillRingHead();
					if (after != before && !after.empty()) {
						SDL_SetClipboardText(after.c_str());
					}
				}
			}
		}

		// Handle new-window request
		if (wed.NewWindowRequested()) {
			wed.SetNewWindowRequested(false);
			OpenNewWindow_(ed); // always share primary editor's buffers
		}

		if (wi == 0 && wed.QuitRequested()) {
			running = false;
		}

		// Draw
		ws.renderer.Draw(wed);

		// Render
		ImGui::Render();
		int display_w, display_h;
		SDL_GL_GetDrawableSize(ws.window, &display_w, &display_h);
		glViewport(0, 0, display_w, display_h);
		glClearColor(0.1f, 0.1f, 0.11f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);
		ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
		SDL_GL_SwapWindow(ws.window);
	}

	// Remove dead secondary windows
	for (auto it = windows_.begin() + 1; it != windows_.end();) {
		if (!(*it)->alive) {
			SDL_GL_MakeCurrent((*it)->window, (*it)->gl_ctx);
			ImGui_ImplOpenGL3_Shutdown();
			SDL_GL_DeleteContext((*it)->gl_ctx);
			SDL_DestroyWindow((*it)->window);
			it = windows_.erase(it);
			// Restore primary context
			SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
		} else {
			++it;
		}
	}
}


void
GUIFrontend::Shutdown()
{
	// Destroy secondary windows first
	for (std::size_t i = 1; i < windows_.size(); ++i) {
		SDL_GL_MakeCurrent(windows_[i]->window, windows_[i]->gl_ctx);
		ImGui_ImplOpenGL3_Shutdown();
		SDL_GL_DeleteContext(windows_[i]->gl_ctx);
		SDL_DestroyWindow(windows_[i]->window);
	}
	windows_.resize(std::min(windows_.size(), std::size_t(1)));

	// Destroy primary window
	if (!windows_.empty()) {
		SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
	}
	ImGui_ImplOpenGL3_Shutdown();
	ImGui_ImplSDL2_Shutdown();
	ImGui::DestroyContext();

	if (!windows_.empty()) {
		if (windows_[0]->gl_ctx) {
			SDL_GL_DeleteContext(windows_[0]->gl_ctx);
			windows_[0]->gl_ctx = nullptr;
		}
		if (windows_[0]->window) {
			SDL_DestroyWindow(windows_[0]->window);
			windows_[0]->window = nullptr;
		}
	}
	windows_.clear();
	SDL_Quit();
}


bool
GUIFrontend::LoadGuiFont_(const char * /*path*/, const float size_px)
{
	const ImGuiIO &io = ImGui::GetIO();
	io.Fonts->Clear();

	ImFontConfig config;
	config.MergeMode = false;

	io.Fonts->AddFontFromMemoryCompressedTTF(
		kte::Fonts::DefaultFontData,
		kte::Fonts::DefaultFontSize,
		size_px,
		&config,
		io.Fonts->GetGlyphRangesDefault());

	config.MergeMode                       = true;
	static const ImWchar extended_ranges[] = {
		0x0370, 0x03FF, // Greek and Coptic
		0x2200, 0x22FF, // Mathematical Operators
		0,
	};
	io.Fonts->AddFontFromMemoryCompressedTTF(
		kte::Fonts::IosevkaExtended::DefaultFontRegularCompressedData,
		kte::Fonts::IosevkaExtended::DefaultFontRegularCompressedSize,
		size_px,
		&config,
		extended_ranges);

	io.Fonts->Build();
	return true;
}