package application

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"sync/atomic"
	"time"

	"github.com/go-gl/gl/v3.3-core/gl"
	"github.com/veandco/go-sdl2/sdl"
	"github.com/veandco/go-sdl2/ttf"
	"rhemawavetech.com/rhemawave/internal/db"
	"rhemawavetech.com/rhemawave/internal/fontManager"
	"rhemawavetech.com/rhemawave/internal/graphics"
	"rhemawavetech.com/rhemawave/internal/keybinds"
	"rhemawavetech.com/rhemawave/internal/license"
	"rhemawavetech.com/rhemawave/internal/logger"
	"rhemawavetech.com/rhemawave/internal/mixer"
	"rhemawavetech.com/rhemawave/internal/network"
	"rhemawavetech.com/rhemawave/internal/page"
	"rhemawavetech.com/rhemawave/internal/shaderManager"
)

const (
	targetFPS          = 60.0
	volumeStepSize     = 16
	openGLMajorVersion = 3
	openGLMinorVersion = 3
	apiURL             = "http://localhost:8000"
	apiPath            = "/api/v1/licenseKey/validate"
	audioFileURL       = "https://files.neilclack.com/audio.wav"
)

type Application struct {
	Window        *sdl.Window
	License       *license.Response
	pageStack     []page.Page
	pendingAction func()
	running       bool
}

// ----------------------------------------------------------------------------
// Main Entry Point
// ----------------------------------------------------------------------------

func Run() {
	logger.Info("Starting application")

	appDataDir, err := initializeApplicationDirectory()
	if err != nil {
		logger.Fatal("Failed to initialize application directory: %v", err)
	}

	logger.Info("App directory: %s", appDataDir)
	logger.AddFile(filepath.Join(appDataDir, "log.txt"))

	if err := initializeDatabase(appDataDir); err != nil {
		logger.Fatal("Database initialization failed: %v", err)
	}

	app := &Application{}

	app.initializeSDLAndOpenGL()
	defer app.cleanup()

	app.initializeManagers()
	app.initializeAudio()
	app.validateLicenseKey()
	app.startupPageStack()
	app.runEventLoop()
}

// ----------------------------------------------------------------------------
// Initialization Functions
// ----------------------------------------------------------------------------

func initializeApplicationDirectory() (string, error) {
	homeDir, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("failed to get user home directory: %w", err)
	}

	appDataDir := filepath.Join(homeDir, ".local", "share", "rhemawave")

	if err := os.MkdirAll(appDataDir, 0755); err != nil {
		return "", fmt.Errorf("could not create application data directory %s: %w", appDataDir, err)
	}

	testFile := filepath.Join(appDataDir, ".access_test")
	f, err := os.Create(testFile)
	if err != nil {
		return "", fmt.Errorf("application data directory %s is not writable: %w", appDataDir, err)
	}
	f.Close()
	os.Remove(testFile)

	return appDataDir, nil
}

func initializeDatabase(appDataDir string) error {
	dbPath := filepath.Join(appDataDir, "data.db")
	if err := db.InitDatabase(dbPath); err != nil {
		return fmt.Errorf("failed to initialize database: %w", err)
	}
	logger.AddDatabase(db.DB)
	return nil
}

type progressWriter struct {
	w       io.Writer
	written *atomic.Int64
}

func (pw *progressWriter) Write(p []byte) (int, error) {
	n, err := pw.w.Write(p)
	pw.written.Add(int64(n))
	return n, err
}

// ensureAudioFile checks whether the selected audio file exists. If it does,
// it returns nil. Otherwise it starts a background download and returns a
// DownloadProgressPage that tracks the download so it can be pushed onto the
// page stack.
func ensureAudioFile() *page.DownloadProgressPage {
	assetsDir, err := db.GetConfigValue("assets_dir")
	if err != nil {
		logger.Error("Failed to get assets_dir: %v", err)
		return nil
	}
	selectedAudio, err := db.GetConfigValue("selected_audio")
	if err != nil || selectedAudio == "" {
		logger.Warning("No selected_audio configured")
		return nil
	}

	audioPath := filepath.Join(assetsDir, selectedAudio)
	if _, err := os.Stat(audioPath); err == nil {
		logger.Info("Audio file found: %s", audioPath)
		return nil
	}

	logger.Info("Audio file not found at %s, downloading from %s", audioPath, audioFileURL)

	totalBytes := &atomic.Int64{}
	bytesWritten := &atomic.Int64{}
	done := &atomic.Bool{}
	hasError := &atomic.Bool{}

	downloadPage := &page.DownloadProgressPage{
		TotalBytes:   totalBytes,
		BytesWritten: bytesWritten,
		Done:         done,
		HasError:     hasError,
	}

	go func() {
		defer done.Store(true)

		if err := os.MkdirAll(filepath.Dir(audioPath), 0755); err != nil {
			logger.Error("Failed to create audio directory: %v", err)
			hasError.Store(true)
			return
		}

		resp, err := http.Get(audioFileURL)
		if err != nil {
			logger.Error("Failed to download audio file: %v", err)
			hasError.Store(true)
			return
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			logger.Error("Audio download returned status %d", resp.StatusCode)
			hasError.Store(true)
			return
		}

		if resp.ContentLength > 0 {
			totalBytes.Store(resp.ContentLength)
		}

		tmp := audioPath + ".tmp"
		f, err := os.Create(tmp)
		if err != nil {
			logger.Error("Failed to create audio file: %v", err)
			hasError.Store(true)
			return
		}

		pw := &progressWriter{w: f, written: bytesWritten}
		_, err = io.Copy(pw, resp.Body)
		f.Close()
		if err != nil {
			os.Remove(tmp)
			logger.Error("Failed to write audio file: %v", err)
			hasError.Store(true)
			return
		}

		if err := os.Rename(tmp, audioPath); err != nil {
			os.Remove(tmp)
			logger.Error("Failed to move audio file into place: %v", err)
			hasError.Store(true)
			return
		}

		logger.Info("Audio file downloaded successfully (%d bytes)", bytesWritten.Load())
	}()

	return downloadPage
}

func (app *Application) initializeSDLAndOpenGL() {
	logger.Info("Initializing SDL")
	if err := sdl.Init(sdl.INIT_VIDEO | sdl.INIT_AUDIO); err != nil {
		logger.Fatal("SDL init failed: %v", err)
	}

	logger.Info("Initializing TTF")
	if err := ttf.Init(); err != nil {
		logger.Fatal("TTF init failed: %v", err)
	}

	sdl.GLSetAttribute(sdl.GL_CONTEXT_MAJOR_VERSION, openGLMajorVersion)
	sdl.GLSetAttribute(sdl.GL_CONTEXT_MINOR_VERSION, openGLMinorVersion)
	sdl.GLSetAttribute(sdl.GL_CONTEXT_PROFILE_MASK, sdl.GL_CONTEXT_PROFILE_CORE)
	sdl.ShowCursor(sdl.DISABLE)
	sdl.SetRelativeMouseMode(true)

	logger.Info("Querying display mode")
	displayMode, err := sdl.GetDisplayMode(0, 0)
	if err != nil {
		logger.Fatal("Display mode query failed: %v", err)
	}
	if displayMode.W == 0 || displayMode.H == 0 {
		logger.Fatal("Invalid display dimensions: %dx%d", displayMode.W, displayMode.H)
	}
	logger.Info("Display: %dx%d @ %dHz", displayMode.W, displayMode.H, displayMode.RefreshRate)

	logger.Info("Creating window")
	window, err := sdl.CreateWindow(
		"Rhema Wave",
		sdl.WINDOWPOS_UNDEFINED,
		sdl.WINDOWPOS_UNDEFINED,
		displayMode.W,
		displayMode.H,
		sdl.WINDOW_OPENGL|sdl.WINDOW_FULLSCREEN_DESKTOP|sdl.WINDOW_SHOWN,
	)
	if err != nil {
		logger.Fatal("Window creation failed: %v", err)
	}
	app.Window = window

	logger.Info("Creating OpenGL context")
	if _, err := app.Window.GLCreateContext(); err != nil {
		logger.Fatal("OpenGL context creation failed: %v", err)
	}

	logger.Info("Initializing go-gl")
	if err := gl.InitWithProcAddrFunc(sdl.GLGetProcAddress); err != nil {
		logger.Fatal("go-gl initialization failed: %v", err)
	}

	logger.Info("OpenGL version: %s", gl.GoStr(gl.GetString(gl.VERSION)))
	logger.Info("OpenGL renderer: %s", gl.GoStr(gl.GetString(gl.RENDERER)))

	if err := sdl.GLSetSwapInterval(1); err != nil {
		logger.Warning("Failed to enable vsync: %v", err)
	}

	w, h := app.Window.GLGetDrawableSize()
	logger.Info("Drawable size: %dx%d", w, h)

	logger.Info("Initializing virtual framebuffer (%dx%d -> %dx%d)",
		graphics.VirtualWidth, graphics.VirtualHeight, w, h)
	if err := graphics.InitVirtualFramebuffer(w, h); err != nil {
		logger.Fatal("Virtual framebuffer init failed: %v", err)
	}

	app.initKeybinds()
	logger.Info("SDL and OpenGL initialization complete")
}

func (app *Application) initializeManagers() {
	logger.Info("Initializing ShaderManager")
	if err := shaderManager.InitShaderManager(); err != nil {
		logger.Fatal("ShaderManager initialization failed: %v", err)
	}

	logger.Info("Initializing FontManager")
	if err := fontManager.InitFontManager(); err != nil {
		logger.Fatal("FontManager initialization failed: %v", err)
	}
}

func (app *Application) initializeAudio() {
	logger.Info("Initializing audio")
	audioDevice, err := db.GetConfigValue("audio_device_name")
	if err != nil {
		logger.Warning("Failed to get audio device name from config: %v", err)
	}

	if err := mixer.Init(audioDevice); err != nil {
		logger.Error("Unable to initialize audio device '%s': %v", audioDevice, err)
		logger.Error("Audio will be unavailable until a device is configured")
	} else {
		logger.Info("Audio initialized with device: '%s'", audioDevice)
	}
}

func (app *Application) cleanup() {
	logger.Info("Cleaning up")

	for _, p := range app.pageStack {
		p.Destroy()
	}
	app.pageStack = nil

	graphics.DestroyVirtualFramebuffer()

	if app.Window != nil {
		app.Window.Destroy()
	}

	ttf.Quit()
	sdl.Quit()
	logger.Info("Cleanup complete")
	logger.Close()
}

// ----------------------------------------------------------------------------
// Event Loop
// ----------------------------------------------------------------------------

func (app *Application) runEventLoop() {
	if len(app.pageStack) == 0 {
		logger.Fatal("No initial page loaded, pageStack is empty")
	}

	const frameDelay = time.Second / targetFPS
	app.running = true
	lastTime := time.Now()

	logger.Info("Entering event loop")

	for app.running {
		frameStart := time.Now()

		app.handleEvents()
		if !app.running {
			break
		}

		deltaTime := float32(time.Since(lastTime).Seconds())
		lastTime = time.Now()

		app.updateCurrentPage(deltaTime)
		app.renderFrame()
		app.applyPendingAction()

		frameTime := time.Since(frameStart)
		if frameTime < frameDelay {
			time.Sleep(frameDelay - frameTime)
		}
	}

	logger.Info("Event loop exited")
}

func (app *Application) handleEvents() {
	for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
		switch e := event.(type) {
		case *sdl.QuitEvent:
			app.running = false
			return

		case *sdl.TextInputEvent:
			logger.Info("[EVENT] TextInputEvent: text=%q, IsTextInputActive=%v", e.GetText(), sdl.IsTextInputActive())

		case *sdl.KeyboardEvent:
			eventType := "KEYDOWN"
			if e.Type == sdl.KEYUP {
				eventType = "KEYUP"
			}
			logger.Info("[EVENT] KeyboardEvent: type=%s, sym=%d (%s), scancode=%d, mod=0x%04x, IsTextInputActive=%v",
				eventType, e.Keysym.Sym, sdl.GetKeyName(e.Keysym.Sym), e.Keysym.Scancode, e.Keysym.Mod, sdl.IsTextInputActive())

			if e.Type == sdl.KEYDOWN && e.Repeat == 0 {
				isCtrlPressed := (e.Keysym.Mod&sdl.KMOD_CTRL) != 0 || (e.Keysym.Mod&sdl.KMOD_GUI) != 0
				if e.Keysym.Sym == sdl.K_c && isCtrlPressed {
					continue
				}
				keybinds.PerformAction(e)
			}
		}

		if currentPage := app.currentPage(); currentPage != nil {
			if err := currentPage.HandleEvent(&event); err != nil {
				logger.Error("Page event handler error: %v", err)
			}
		}
	}
}

func (app *Application) updateCurrentPage(deltaTime float32) {
	if currentPage := app.currentPage(); currentPage != nil {
		currentPage.Update(deltaTime)
	}
}

func (app *Application) renderFrame() {
	graphics.BeginVirtualRender()
	gl.ClearColor(0.0, 0.0, 0.0, 1.0)
	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

	if currentPage := app.currentPage(); currentPage != nil {
		currentPage.Render()
	}

	graphics.BlitToScreen()
	app.Window.GLSwap()
}

// ----------------------------------------------------------------------------
// Keybind Registration
// ----------------------------------------------------------------------------

func (app *Application) initKeybinds() {
	keybinds.Register(sdl.K_F3, sdl.KMOD_NONE, func() {
		app.PushPage(&page.Settings{})
	})

	keybinds.Register(sdl.K_F2, sdl.KMOD_NONE, func() {
		downloadPage := ensureAudioFile()
		if downloadPage != nil {
			downloadPage.NextPage = &page.ScrollerPage{}
			app.PushPage(downloadPage)
		} else {
			app.PushPage(&page.ScrollerPage{})
		}
	})

	keybinds.Register(sdl.K_F1, sdl.KMOD_NONE, func() {
		app.UnwindToPage(&page.Welcome{})
	})

	keybinds.Register(sdl.K_q, sdl.KMOD_RCTRL, func() {
		app.Stop()
	})

	keybinds.Register(sdl.K_UP, sdl.KMOD_SHIFT, func() {
		mixer.SetVolume128(volumeStepSize)
	})

	keybinds.Register(sdl.K_DOWN, sdl.KMOD_SHIFT, func() {
		mixer.SetVolume128(-volumeStepSize)
	})
}

func (app *Application) Stop() {
	app.running = false
}

// ----------------------------------------------------------------------------
// Page Management
// ----------------------------------------------------------------------------

func (app *Application) currentPage() page.Page {
	if len(app.pageStack) == 0 {
		return nil
	}
	return app.pageStack[len(app.pageStack)-1]
}

func (app *Application) applyPendingAction() {
	if app.pendingAction != nil {
		app.pendingAction()
		app.pendingAction = nil
	}
}

func (app *Application) schedulePush(p page.Page) {
	app.pendingAction = func() {
		if err := p.Init(app); err != nil {
			logger.Error("Failed to init page on push: %v", err)
			return
		}

		if topPage := app.currentPage(); topPage != nil {
			topPage.Destroy()
		}

		app.pageStack = append(app.pageStack, p)
	}
}

func (app *Application) scheduleSwitch(p page.Page) {
	app.pendingAction = func() {
		if topPage := app.currentPage(); topPage != nil {
			topPage.Destroy()
			app.pageStack = app.pageStack[:len(app.pageStack)-1]
		}

		if err := p.Init(app); err != nil {
			logger.Error("Failed to init page on switch: %v", err)
			return
		}

		app.pageStack = append(app.pageStack, p)
	}
}

func (app *Application) scheduleUnwind(targetPage page.Page) {
	app.pendingAction = func() {
		foundIndex := -1
		for i := len(app.pageStack) - 1; i >= 0; i-- {
			if app.pageStack[i] == targetPage {
				foundIndex = i
				break
			}
		}

		if foundIndex != -1 {
			for i := len(app.pageStack) - 1; i > foundIndex; i-- {
				app.pageStack[i].Destroy()
			}
			app.pageStack = app.pageStack[:foundIndex+1]
		} else {
			if topPage := app.currentPage(); topPage != nil {
				topPage.Destroy()
				app.pageStack = app.pageStack[:len(app.pageStack)-1]
			}

			if err := targetPage.Init(app); err != nil {
				logger.Error("Failed to init page on unwind: %v", err)
				return
			}

			app.pageStack = append(app.pageStack, targetPage)
		}
	}
}

func (app *Application) SchedulePop() {
	app.pendingAction = func() {
		if len(app.pageStack) == 0 {
			return
		}

		topPage := app.pageStack[len(app.pageStack)-1]
		topPage.Destroy()
		app.pageStack = app.pageStack[:len(app.pageStack)-1]

		if newTop := app.currentPage(); newTop != nil {
			if err := newTop.Init(app); err != nil {
				logger.Error("Failed to re-init page after pop: %v", err)
			}
		}
	}
}

// ----------------------------------------------------------------------------
// Public Page Navigation Interface
// ----------------------------------------------------------------------------

func (app *Application) PushPage(p page.Page) {
	app.schedulePush(p)
}

func (app *Application) SwitchPage(p page.Page) {
	app.scheduleSwitch(p)
}

func (app *Application) UnwindToPage(p page.Page) {
	app.scheduleUnwind(p)
}

func (app *Application) GetDrawableSize() (w, h int32) {
	return graphics.VirtualWidth, graphics.VirtualHeight
}

func (app *Application) PopPage() {
	app.SchedulePop()
}

// ----------------------------------------------------------------------------
// License Validation
// ----------------------------------------------------------------------------

func (app *Application) validateLicenseKey() {
	logger.Info("Validating license key")
	validator := license.NewValidator(apiURL, apiPath)

	key, err := db.GetConfigValue("license_key")
	if err != nil {
		logger.Error("Failed to fetch license key from database: %v", err)
	}

	email, err := db.GetConfigValue("email_address")
	if err != nil {
		logger.Error("Failed to fetch email from database: %v", err)
	}

	result, err := validator.Validate(key, email)
	if err != nil {
		logger.Error("License validation failed: %v", err)
		app.License = nil
		return
	}

	logger.Info("License validation successful")
	app.License = result
}

// ----------------------------------------------------------------------------
// Startup Page Stack
// ----------------------------------------------------------------------------

func (app *Application) startupPageStack() {
	app.PushPage(&page.Welcome{})
	app.applyPendingAction()

	key, _ := db.GetConfigValue("license_key")
	if key == "" {
		logger.Info("No license key found, pushing license key page")
		app.PushPage(&page.LicenseKeyPage{})
		app.applyPendingAction()
	} else {
		// Ensure the license key file exists for the updater script.
		// Older versions only stored the key in the database.
		if homeDir, err := os.UserHomeDir(); err == nil {
			keyPath := filepath.Join(homeDir, ".local", "share", "rhemawave", "license_key")
			if _, err := os.Stat(keyPath); os.IsNotExist(err) {
				logger.Info("License key file missing, writing from database")
				if err := os.MkdirAll(filepath.Dir(keyPath), 0755); err != nil {
					logger.Error("Failed to create license key directory: %v", err)
				} else if err := os.WriteFile(keyPath, []byte(key), 0644); err != nil {
					logger.Error("Failed to write license key file: %v", err)
				}
			}
		}
	}

	email, _ := db.GetConfigValue("email_address")
	if email == "" {
		logger.Info("No email address found, pushing email address page")
		app.PushPage(&page.EmailAddressPage{})
		app.applyPendingAction()
	}

	// TOS pages — must be accepted before anything else.
	// Pushed last so they sit on top of the stack (shown first).
	sections, err := db.GetTOSSections()
	if err != nil {
		logger.Error("Failed to load TOS sections: %v", err)
	}
	// Push in reverse order so section 1 is on top of the stack
	for i := len(sections) - 1; i >= 0; i-- {
		s := sections[i]
		configKey := fmt.Sprintf("tos_section_%d_accepted", s.SectionNumber)
		accepted, _ := db.GetConfigValue(configKey)
		if accepted != "true" {
			app.PushPage(&page.TOSPage{
				Title:     s.Title,
				Content:   s.Content,
				ConfigKey: configKey,
			})
			app.applyPendingAction()
		}
	}

	// Internet check — pushed last so it appears first if no internet.
	// Skip WiFi setup if ethernet is connected (it auto-configures) or if
	// internet is already reachable through any interface.
	nm, err := network.New()
	if err != nil {
		logger.Warning("Could not initialize network manager: %v", err)
	} else {
		status, err := nm.CheckInternetConnection()
		if err != nil {
			logger.Warning("Network connectivity check failed: %v", err)
		} else {
			switch status.StatusCode {
			case network.StatusEthernetConnectedInternetUp,
				network.StatusEthernetConnectedNoInternet,
				network.StatusWifiConnectedInternetUp:
				// Internet is up or ethernet is connected and will auto-configure
			default:
				logger.Info("No internet connection, pushing WiFi setup page")
				app.PushPage(&page.WiFiSetupPage{})
				app.applyPendingAction()
			}
		}
	}
}

func (app *Application) Quit() {
	logger.Info("User has quit the application")
	app.running = false
}