//go:build gtk

// Package gui implements Captioneer's GTK4 desktop application.
package gui

import (
	"context"
	_ "embed"
	"fmt"
	"io"
	"os"
	"os/exec"
	"os/signal"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/diamondburned/gotk4/pkg/gdk/v4"
	"github.com/diamondburned/gotk4/pkg/gio/v2"
	"github.com/diamondburned/gotk4/pkg/glib/v2"
	"github.com/diamondburned/gotk4/pkg/gtk/v4"
	"tea.chunkbyte.com/kato/captioneer/src/app"
	"tea.chunkbyte.com/kato/captioneer/src/config"
	"tea.chunkbyte.com/kato/captioneer/src/diagnostics"
	"tea.chunkbyte.com/kato/captioneer/src/output"
	"tea.chunkbyte.com/kato/captioneer/src/output/history"
	"tea.chunkbyte.com/kato/captioneer/src/output/overlay"
	"tea.chunkbyte.com/kato/captioneer/src/output/terminal"
	"tea.chunkbyte.com/kato/captioneer/src/output/transcript"
)

const (
	applicationID   = "com.chunkbyte.captioneer"
	historyCapacity = 500
	consoleCapacity = 2000
)

//go:embed style.css
var applicationCSS string

type Application struct {
	launch  config.LaunchConfig
	config  config.AppConfig
	applied config.AppConfig
	stdout  io.Writer
	stderr  io.Writer

	gtkApp *gtk.Application
	window *gtk.ApplicationWindow
	stack  *gtk.Stack

	router     *output.Router
	history    *history.Sink
	log        *diagnostics.Log
	controller *app.Controller
	overlay    *overlay.Sink
	transcript *transcript.Sink

	statusLabel      *gtk.Label
	statusDot        *gtk.Label
	startStopButton  *gtk.Button
	statusSource     *gtk.Label
	statusSpeech     *gtk.Label
	statusOutputs    *gtk.Label
	captionBuffer    *gtk.TextBuffer
	captionView      *gtk.TextView
	captionScroll    *gtk.ScrolledWindow
	captionMetaTag   *gtk.TextTag
	captionHintTag   *gtk.TextTag
	provisionalLabel *gtk.Label
	consoleBuffer    *gtk.TextBuffer
	consoleView      *gtk.TextView
	consoleScroll    *gtk.ScrolledWindow
	consoleMetaTag   *gtk.TextTag
	consoleWarnTag   *gtk.TextTag
	consoleErrorTag  *gtk.TextTag
	settings         settingsControls
	settingsError    *gtk.Label
	applyButton      *gtk.Button
	lastShownError   string

	statusUpdates  <-chan app.Status
	stopStatus     func()
	historyUpdates <-chan history.Snapshot
	stopHistory    func()
	logUpdates     <-chan diagnostics.Entry
	stopLog        func()
	uiDone         chan struct{}

	closingMu sync.Mutex
	closing   bool
}

func Run(launch config.LaunchConfig, stdout, stderr io.Writer) int {
	application := newApplication(launch, stdout, stderr)
	application.gtkApp.ConnectActivate(application.activate)
	signals := make(chan os.Signal, 1)
	signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
	defer signal.Stop(signals)
	go func() {
		select {
		case <-signals:
			glib.IdleAdd(application.shutdown)
		case <-application.uiDone:
		}
	}()
	return application.gtkApp.Run([]string{os.Args[0]})
}

func newApplication(launch config.LaunchConfig, stdout, stderr io.Writer) *Application {
	mirror := io.Discard
	if launch.Config.Outputs.StderrDiagnostics {
		mirror = stderr
	}
	log := diagnostics.New(consoleCapacity, mirror)
	router := output.NewRouter()
	historySink := history.New(historyCapacity, launch.Config.Outputs.History)
	_ = router.Set("history", historySink)
	controller := app.NewController(router, log.Writer(diagnostics.Info, "engine"))
	return &Application{
		launch:     launch,
		config:     launch.Config,
		applied:    launch.Config,
		stdout:     stdout,
		stderr:     stderr,
		gtkApp:     gtk.NewApplication(applicationID, gio.ApplicationFlagsNone),
		router:     router,
		history:    historySink,
		log:        log,
		controller: controller,
		uiDone:     make(chan struct{}),
	}
}

func (a *Application) activate() {
	if a.window != nil {
		a.window.Present()
		return
	}
	a.installStyle()
	a.buildWindow()
	a.installActions()
	a.subscribeModels()
	overlay.SetPositionSaver(a.saveOverlayPosition)
	if a.launch.Warning != nil {
		a.log.Add(diagnostics.Warning, "configuration", fmt.Sprintf("%v; using built-in defaults", a.launch.Warning))
	}
	// Show the main window before creating the overlay so a Layer Shell /
	// display failure cannot leave the user with a silent no-GUI launch.
	a.window.Present()
	if err := a.configureOutputs(a.config, true); err != nil {
		a.log.Add(diagnostics.Error, "outputs", err.Error())
	}
	a.applyAlwaysOnTop(a.config.GUI.MainWindowAlwaysOnTop)
	if a.config.GUI.StartCaptions {
		a.startCaptions()
	}
}

func (a *Application) installStyle() {
	provider := gtk.NewCSSProvider()
	provider.LoadFromString(applicationCSS)
	gtk.StyleContextAddProviderForDisplay(
		gdk.DisplayGetDefault(),
		provider,
		gtk.STYLE_PROVIDER_PRIORITY_APPLICATION,
	)
}

func (a *Application) buildWindow() {
	a.window = gtk.NewApplicationWindow(a.gtkApp)
	a.window.SetTitle("Captioneer")
	a.window.SetDefaultSize(980, 680)
	a.window.SetSizeRequest(720, 480)
	a.window.AddCSSClass("captioneer-main")
	a.window.ConnectCloseRequest(func() bool {
		a.shutdown()
		return true
	})

	header := gtk.NewHeaderBar()
	header.AddCSSClass("captioneer-header")
	header.SetShowTitleButtons(true)

	brand := gtk.NewBox(gtk.OrientationHorizontal, 7)
	if iconPath := findIconPath(); iconPath != "" {
		icon := gtk.NewImageFromFile(iconPath)
		icon.SetPixelSize(20)
		brand.Append(icon)
	}
	title := gtk.NewLabel("CAPTIONEER")
	title.AddCSSClass("captioneer-brand")
	brand.Append(title)
	header.PackStart(brand)

	statusBox := gtk.NewBox(gtk.OrientationHorizontal, 6)
	statusBox.SetHAlign(gtk.AlignCenter)
	statusBox.AddCSSClass("status-cell")
	a.statusDot = gtk.NewLabel("●")
	a.statusDot.AddCSSClass("status-dot")
	a.statusLabel = gtk.NewLabel("STOPPED · VAD")
	a.statusLabel.AddCSSClass("status-text")
	statusBox.Append(a.statusDot)
	statusBox.Append(a.statusLabel)
	header.SetTitleWidget(statusBox)

	a.startStopButton = gtk.NewButtonWithLabel("START")
	a.startStopButton.AddCSSClass("primary-action")
	a.startStopButton.SetTooltipText("Start or stop caption processing")
	a.startStopButton.ConnectClicked(a.toggleCaptions)
	header.PackEnd(a.startStopButton)
	a.window.SetTitlebar(header)

	root := gtk.NewBox(gtk.OrientationVertical, 0)
	root.Append(a.buildMenuBar())
	a.stack = gtk.NewStack()
	a.stack.SetTransitionType(gtk.StackTransitionTypeNone)
	a.stack.SetHExpand(true)
	a.stack.SetVExpand(true)

	tabs := gtk.NewStackSwitcher()
	tabs.SetStack(a.stack)
	tabs.SetHAlign(gtk.AlignStart)
	tabStrip := gtk.NewBox(gtk.OrientationHorizontal, 0)
	tabStrip.AddCSSClass("captioneer-tabs")
	tabStrip.Append(tabs)
	root.Append(tabStrip)

	a.stack.AddTitled(a.buildCaptionsPage(), "captions", "CAPTIONS")
	a.stack.AddTitled(a.buildConsolePage(), "console", "CONSOLE")
	a.stack.AddTitled(a.buildSettingsPage(), "settings", "SETTINGS")
	root.Append(a.stack)

	statusbar := gtk.NewBox(gtk.OrientationHorizontal, 4)
	statusbar.AddCSSClass("statusbar")
	a.statusSource = statusSegment("Source: not connected")
	a.statusSource.SetHExpand(true)
	a.statusSource.SetXAlign(0)
	a.statusSource.SetEllipsize(3)
	a.statusSpeech = statusSegment("Speech: quiet")
	a.statusOutputs = statusSegment("Outputs: preparing")
	statusbar.Append(a.statusSource)
	statusbar.Append(a.statusSpeech)
	statusbar.Append(a.statusOutputs)
	root.Append(statusbar)
	a.window.SetChild(root)
}

func (a *Application) buildMenuBar() *gtk.PopoverMenuBar {
	root := gio.NewMenu()
	file := gio.NewMenu()
	file.Append("Start Captions", "app.start")
	file.Append("Stop Captions", "app.stop")
	file.Append("Restart Captions", "app.restart")
	file.Append("Clear Caption History", "app.clear-history")
	file.Append("Exit", "app.exit")
	root.AppendSubmenu("File", file)

	view := gio.NewMenu()
	view.Append("Captions", "app.view-captions")
	view.Append("Console", "app.view-console")
	view.Append("Settings", "app.view-settings")
	root.AppendSubmenu("View", view)

	help := gio.NewMenu()
	help.Append("Copy Diagnostics", "app.copy-diagnostics")
	help.Append("Open Configuration Folder", "app.open-config-folder")
	help.Append("About Captioneer", "app.about")
	root.AppendSubmenu("Help", help)
	bar := gtk.NewPopoverMenuBarFromModel(root)
	bar.AddCSSClass("captioneer-menu")
	return bar
}

func (a *Application) installActions() {
	a.addAction("start", a.startCaptions)
	a.addAction("stop", a.stopCaptions)
	a.addAction("restart", a.restartCaptions)
	a.addAction("clear-history", a.history.Clear)
	a.addAction("exit", a.shutdown)
	a.addAction("view-captions", func() { a.stack.SetVisibleChildName("captions") })
	a.addAction("view-console", func() { a.stack.SetVisibleChildName("console") })
	a.addAction("view-settings", func() { a.stack.SetVisibleChildName("settings") })
	a.addAction("copy-diagnostics", a.copyDiagnostics)
	a.addAction("open-config-folder", a.openConfigFolder)
	a.addAction("about", a.showAbout)
	a.gtkApp.SetAccelsForAction("app.start", []string{"F5"})
	a.gtkApp.SetAccelsForAction("app.stop", []string{"<Shift>F5"})
	a.gtkApp.SetAccelsForAction("app.restart", []string{"<Primary>r"})
	a.gtkApp.SetAccelsForAction("app.view-captions", []string{"<Alt>1"})
	a.gtkApp.SetAccelsForAction("app.view-console", []string{"<Alt>2"})
	a.gtkApp.SetAccelsForAction("app.view-settings", []string{"<Alt>3"})
	a.gtkApp.SetAccelsForAction("app.exit", []string{"<Primary>q"})
}

func (a *Application) addAction(name string, callback func()) {
	action := gio.NewSimpleAction(name, nil)
	action.ConnectActivate(func(*glib.Variant) { callback() })
	a.gtkApp.AddAction(action)
}

func (a *Application) subscribeModels() {
	a.statusUpdates, a.stopStatus = a.controller.Subscribe(32)
	a.historyUpdates, a.stopHistory = a.history.Subscribe(8)
	a.logUpdates, a.stopLog = a.log.Subscribe(128)
	go a.forwardStatus()
	go a.forwardHistory()
	go a.forwardLog()
}

func (a *Application) forwardStatus() {
	for {
		select {
		case <-a.uiDone:
			return
		case status, ok := <-a.statusUpdates:
			if !ok {
				return
			}
			copy := status
			glib.IdleAdd(func() { a.renderStatus(copy) })
		}
	}
}

func (a *Application) forwardHistory() {
	for {
		select {
		case <-a.uiDone:
			return
		case snapshot, ok := <-a.historyUpdates:
			if !ok {
				return
			}
			copy := snapshot
			glib.IdleAdd(func() { a.renderHistory(copy) })
		}
	}
}

func (a *Application) forwardLog() {
	for {
		select {
		case <-a.uiDone:
			return
		case _, ok := <-a.logUpdates:
			if !ok {
				return
			}
			glib.IdleAdd(a.renderConsole)
		}
	}
}

func (a *Application) toggleCaptions() {
	status := a.controller.Status()
	switch status.State {
	case app.StateStopped, app.StateError:
		a.startCaptions()
	default:
		a.stopCaptions()
	}
}

func (a *Application) startCaptions() {
	if err := a.controller.Start(a.applied.Settings); err != nil {
		a.log.Add(diagnostics.Error, "lifecycle", err.Error())
		return
	}
	a.log.Add(diagnostics.Info, "lifecycle", "Starting caption processing")
}

func (a *Application) stopCaptions() {
	go func() {
		timeout := a.applied.Settings.ModelShutdownTimeout + time.Second
		ctx, cancel := context.WithTimeout(context.Background(), timeout)
		defer cancel()
		if err := a.controller.Stop(ctx); err != nil {
			a.log.Add(diagnostics.Error, "lifecycle", fmt.Sprintf("Stop captions: %v", err))
			return
		}
		a.log.Add(diagnostics.Info, "lifecycle", "Caption processing stopped")
	}()
}

func (a *Application) restartCaptions() {
	go func() {
		timeout := a.applied.Settings.ModelShutdownTimeout + 2*time.Second
		ctx, cancel := context.WithTimeout(context.Background(), timeout)
		defer cancel()
		if err := a.controller.Restart(ctx, a.applied.Settings); err != nil {
			a.log.Add(diagnostics.Error, "lifecycle", fmt.Sprintf("Restart captions: %v", err))
			return
		}
		a.log.Add(diagnostics.Info, "lifecycle", "Caption processing restarted")
	}()
}

func (a *Application) saveOverlayPosition(x, y int) {
	a.config.Overlay.PositionX = x
	a.config.Overlay.PositionY = y
	a.applied.Overlay.PositionX = x
	a.applied.Overlay.PositionY = y
	if err := config.Save(a.launch.Path, a.config); err != nil {
		a.log.Add(diagnostics.Error, "configuration", fmt.Sprintf("Save overlay position: %v", err))
		return
	}
	a.log.Add(diagnostics.Info, "overlay", fmt.Sprintf("Saved caption position (%d, %d)", x, y))
}

func (a *Application) configureOutputs(next config.AppConfig, initial bool) error {
	var outputErr error
	a.history.SetEnabled(next.Outputs.History)
	if next.Outputs.StdoutCaptions {
		outputErr = joinError(outputErr, a.router.Set("stdout", terminal.New(a.stdout)))
	} else {
		outputErr = joinError(outputErr, a.router.Remove("stdout"))
	}

	if next.TranscriptLog.Enabled {
		if initial || a.transcript == nil || next.TranscriptLog != a.applied.TranscriptLog {
			sink, err := transcript.New(next.TranscriptLog.Directory)
			if err != nil {
				outputErr = joinError(outputErr, err)
			} else {
				a.transcript = sink
				outputErr = joinError(outputErr, a.router.Set("transcript", sink))
				a.log.Add(diagnostics.Info, "transcript", "Saving captions to "+sink.Path())
			}
		}
	} else {
		a.transcript = nil
		outputErr = joinError(outputErr, a.router.Remove("transcript"))
	}

	if next.Outputs.Overlay {
		settings := next.Overlay
		if !initial && settings.Backend != a.applied.Overlay.Backend {
			settings.Backend = a.applied.Overlay.Backend
		}
		if initial || a.overlay == nil || settings != a.applied.Overlay {
			sink, warning, err := overlay.New(settings)
			if warning != "" {
				a.log.Add(diagnostics.Warning, "overlay", warning)
			}
			if err != nil {
				outputErr = joinError(outputErr, err)
			} else {
				a.overlay = sink
				outputErr = joinError(outputErr, a.router.Set("overlay", sink))
			}
		}
	} else {
		a.overlay = nil
		outputErr = joinError(outputErr, a.router.Remove("overlay"))
	}

	if next.Outputs.StderrDiagnostics {
		a.log.SetMirror(a.stderr)
	} else {
		a.log.SetMirror(io.Discard)
	}
	return outputErr
}

func (a *Application) renderStatus(status app.Status) {
	a.updateApplyButton()
	state := strings.ToUpper(string(status.State))
	overloaded := !status.OverloadedAt.IsZero() && time.Since(status.OverloadedAt) < 5*time.Second
	if overloaded {
		state = "OVERLOADED"
	}
	mode := strings.ToUpper(string(status.Mode))
	if mode == "" {
		mode = strings.ToUpper(string(a.applied.Settings.Mode))
	}
	a.statusLabel.SetText(state + " · " + mode)
	a.statusDot.RemoveCSSClass("status-stopped")
	a.statusDot.RemoveCSSClass("status-running")
	a.statusDot.RemoveCSSClass("status-warning")
	a.statusDot.RemoveCSSClass("status-error")
	active := status.State != app.StateStopped && status.State != app.StateError
	switch {
	case status.State == app.StateError:
		a.statusDot.AddCSSClass("status-error")
	case overloaded:
		a.statusDot.AddCSSClass("status-warning")
	case active:
		a.statusDot.AddCSSClass("status-running")
	default:
		a.statusDot.AddCSSClass("status-stopped")
	}
	if active {
		a.startStopButton.SetLabel("STOP")
		a.startStopButton.RemoveCSSClass("primary-action")
		a.startStopButton.AddCSSClass("danger-action")
	} else {
		a.startStopButton.SetLabel("START")
		a.startStopButton.RemoveCSSClass("danger-action")
		a.startStopButton.AddCSSClass("primary-action")
	}
	speech := "quiet"
	if status.SpeechActive {
		speech = "detected"
	}
	source := status.Source
	if source == "" {
		source = "not connected"
	}
	if overloaded {
		speech += " · OVERLOADED"
		a.statusSpeech.AddCSSClass("warning-text")
	} else {
		a.statusSpeech.RemoveCSSClass("warning-text")
	}
	a.statusSource.SetText("Source: " + source)
	a.statusSpeech.SetText("Speech: " + speech)
	a.statusOutputs.SetText("Outputs: " + a.outputSummary())
	if status.LastError != "" && status.State == app.StateError && status.LastError != a.lastShownError {
		a.log.Add(diagnostics.Error, "engine", status.LastError)
		a.lastShownError = status.LastError
	} else if status.LastError == "" {
		a.lastShownError = ""
	}
}

func (a *Application) outputSummary() string {
	var active []string
	if a.config.Outputs.Overlay {
		active = append(active, "overlay")
	}
	if a.config.Outputs.History {
		active = append(active, "history")
	}
	if a.config.Outputs.StdoutCaptions {
		active = append(active, "stdout")
	}
	if a.config.TranscriptLog.Enabled {
		active = append(active, "log file")
	}
	if len(active) == 0 {
		return "none"
	}
	return strings.Join(active, ", ")
}

func (a *Application) copyDiagnostics() {
	var text strings.Builder
	status := a.controller.Status()
	fmt.Fprintf(&text, "Captioneer diagnostics\nState: %s\nMode: %s\nSource: %s\nConfig: %s\n\n", status.State, status.Mode, status.Source, a.launch.Path)
	for _, entry := range a.log.Entries() {
		fmt.Fprintf(&text, "%s %-7s [%s] %s\n", entry.At.Format(time.RFC3339), strings.ToUpper(string(entry.Severity)), entry.Category, entry.Message)
	}
	gdk.DisplayGetDefault().Clipboard().SetText(text.String())
	a.log.Add(diagnostics.Info, "gui", "Diagnostics copied to clipboard")
}

func (a *Application) openConfigFolder() {
	if err := exec.Command("xdg-open", filepath.Dir(a.launch.Path)).Start(); err != nil {
		a.log.Add(diagnostics.Error, "gui", fmt.Sprintf("Open configuration folder: %v", err))
	}
}

func (a *Application) showAbout() {
	dialog := gtk.NewAboutDialog()
	dialog.SetTransientFor(&a.window.Window)
	dialog.SetModal(true)
	dialog.SetProgramName("Captioneer")
	dialog.SetComments("Local live captions for Linux")
	dialog.SetLicenseType(gtk.LicenseApache20)
	dialog.SetWebsite("https://tea.chunkbyte.com/kato/captioneer")
	dialog.Present()
}

func (a *Application) shutdown() {
	a.closingMu.Lock()
	if a.closing {
		a.closingMu.Unlock()
		return
	}
	a.closing = true
	a.closingMu.Unlock()
	a.log.Add(diagnostics.Info, "lifecycle", "Shutting down Captioneer")
	go func() {
		timeout := a.applied.Settings.ModelShutdownTimeout + 2*time.Second
		ctx, cancel := context.WithTimeout(context.Background(), timeout)
		_ = a.controller.Stop(ctx)
		cancel()
		glib.IdleAdd(func() {
			close(a.uiDone)
			if a.stopStatus != nil {
				a.stopStatus()
				a.stopHistory()
				a.stopLog()
			}
			_ = a.router.Close()
			a.gtkApp.Quit()
		})
	}()
}

func statusSegment(text string) *gtk.Label {
	label := gtk.NewLabel(text)
	label.AddCSSClass("status-segment")
	return label
}

func joinError(current, next error) error {
	if current == nil {
		return next
	}
	if next == nil {
		return current
	}
	return fmt.Errorf("%v; %w", current, next)
}

func findIconPath() string {
	candidates := []string{filepath.Join("assets", "icon", "icon.png")}
	if executable, err := os.Executable(); err == nil {
		candidates = append(candidates, filepath.Join(filepath.Dir(executable), "assets", "icon", "icon.png"))
	}
	for _, candidate := range candidates {
		if info, err := os.Stat(candidate); err == nil && !info.IsDir() {
			return candidate
		}
	}
	return ""
}