package loader

import (
	"context"
	"errors"
	"fmt"
	"galaxy/connector"
	mc "galaxy/model/client"
	"galaxy/storage"
	"plugin"
	"time"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/widget"
)

type ClientInit func(storage.UIStorage, connector.UIConnector, fyne.App) (mc.Client, error)

type loader struct {
	app        fyne.App
	storage    storage.Storage
	connector  connector.Connector
	client     mc.Client
	window     fyne.Window
	textGrid   *widget.TextGrid
	btn        *widget.Button
	fatalError bool
	loaded     chan struct{}
}

const (
	pluginInitSymbol = "Factory"
	libUIPluginFile  = "libui"
)

var (
	checkConnectionTimeout = time.Second * 5
	checkVersionTimeout    = time.Minute * 60
)

func NewLoader(s storage.Storage, conn connector.Connector, app fyne.App) (*loader, error) {
	l := &loader{
		app:       app,
		connector: conn,
		storage:   s,
		textGrid:  widget.NewTextGrid(),
		window:    app.NewWindow("Loader"),
		loaded:    make(chan struct{}),
	}
	l.btn = widget.NewButton("OK", l.onButtonAction)
	l.btn.Disable()

	content := container.NewStack(
		l.textGrid,
		container.NewHBox(
			container.NewCenter(
				l.btn,
			),
		),
	)
	l.window.SetContent(content)

	return l, nil
}

func (l *loader) initPlugin() (mc.Client, error) {
	exists, pluginPath, err := l.storage.FileExists(libUIPluginFile)
	if err != nil {
		l.appendFatalError(fmt.Errorf("Client plugin file lookup error: %w", err))
		return nil, err
	}
	if !exists {
		l.logText("Client plugin file not found, fetching available versions")
		v, err := l.connector.CheckVersion()
		if err != nil {
			l.logError(err)
			return nil, err
		}
		l.logText(fmt.Sprintf("Received %d versions", len(v)))
		latest, ok, err := latestVersion(v)
		if err != nil {
			l.logError(err)
			return nil, err
		}
		if !ok {
			l.logError(errors.New("Server did not responded with a suitable client version"))
			return nil, err
		}
		l.logText(fmt.Sprintf("Downloading version %s", latest.Version))
		data, err := l.connector.DownloadVersion(latest.URL)
		if err != nil {
			l.logError(fmt.Errorf("Version %s download error: %w", latest.Version, err))
			return nil, err
		}
		err = l.storage.WriteFile(libUIPluginFile, data)
		if err != nil {
			l.appendFatalError(fmt.Errorf("Plugin file write error: %w", err))
			return nil, err
		}
	}
	l.logText(fmt.Sprintf("Loading client plugin from %s", pluginPath))
	cli, err := loadClientPlugin(l.storage, l.connector, l.app, pluginPath, pluginInitSymbol)
	if err != nil {
		l.appendFatalError(err)
		return nil, err
	}
	return cli, nil
}

func (l *loader) init() {
	l.fatalError = false
	fyne.Do(func() {
		l.textGrid.SetText("")
		l.btn.Hide()
		l.btn.Disable()
	})
	var err error
	l.client, err = l.initPlugin()
	if err == nil {
		fyne.Do(func() {
			l.window.Hide()
			err = l.client.Run()
		})
	}
	if err != nil {
		fyne.Do(func() {
			if l.fatalError {
				l.btn.SetText("Quit")
				l.logText("Please re-install application.")
			} else {
				l.btn.SetText("Retry")
			}
			l.btn.Enable()
			l.btn.Show()
			l.window.Show()
		})
	} else {
		l.loaded <- struct{}{}
	}
}

func (l *loader) onButtonAction() {
	if l.fatalError {
		l.app.Quit()
	} else {
		go l.init()
	}
}

func (l *loader) logText(v string) {
	fyne.Do(func() { l.textGrid.Append(v) })
}

func (l *loader) logError(err error) {
	l.logText(fmt.Sprintf("❌ %s", err))
}

func (l *loader) appendFatalError(err error) {
	l.logError(err)
	l.fatalError = true
}

func (l *loader) Run(ctx context.Context) error {
	go l.init()
	l.app.Run()
	select {
	case <-ctx.Done():
		return nil
	case <-l.loaded:
		return l.runClient(ctx)
	}
}

func (l *loader) runClient(ctx context.Context) error {
	if l.client == nil {
		return errors.New("run: client wasn't initialized, this is an program fatal error.")
	}
	final := make(chan struct{}, 1)
	go l.backgroundLoop(ctx, final)
	defer func() { final <- struct{}{} }()
	if err := l.client.Run(); err != nil {
		return err
	}
	final <- struct{}{}
	return nil
}

func (l *loader) backgroundLoop(ctx context.Context, final <-chan struct{}) {
	checkConnTimer := time.NewTimer(checkConnectionTimeout)
	checkVersionTimer := time.NewTimer(checkVersionTimeout)
	defer func() {
		checkConnTimer.Stop()
		checkVersionTimer.Stop()
	}()
	for {
		select {
		case <-ctx.Done():
			l.client.Shutdown()
			return
		case <-final:
			return
		case <-checkConnTimer.C:
			isGood := l.connector.CheckConnection()
			l.client.OnConnection(isGood)
			checkConnTimer.Reset(checkConnectionTimeout)
		case <-checkVersionTimer.C:
			versions, err := l.connector.CheckVersion()
			if err != nil {
				// propagate error to the UI
			} else if latest, ok, err := latestVersion(versions); err != nil {
				// propagate error to the UI
			} else if ok {
				l.downloadVersion(latest)
			}
			checkVersionTimer.Reset(checkVersionTimeout)
		}
	}
}

// loadClientPlugin loads a Client implementation from a shared plugin file at the specified path.
// It calls the constructor function by name, passing the necessary dependencies, and returns the initialized Client.
func loadClientPlugin(s storage.UIStorage, conn connector.UIConnector, app fyne.App, path, name string) (mc.Client, error) {
	if path == "" {
		return nil, errors.New("no plugin path given")
	}

	plug, err := plugin.Open(path)
	if err != nil {
		return nil, fmt.Errorf("open plugin %q: %w", path, err)
	}

	sym, err := plug.Lookup(name)
	if err != nil {
		return nil, fmt.Errorf("lookup symbol %q: %w", name, err)
	}

	initializerPtr, ok := sym.(*ClientInit)
	if !ok {
		return nil, fmt.Errorf("unexpected type %T; want %T", sym, initializerPtr)
	}

	return (*initializerPtr)(s, conn, app)
}