// Package gui provides the Fyne desktop app: a settings window and a system
// tray that start/stop the flinger engine.
//
// The engine itself lives in internal/flinger and is GUI-free, so the tray
// can control streaming without any UI dependency. This package wires the two
// together: config persistence, the settings form, and the tray menu.
package gui

import (
	"errors"
	"fmt"
	"image/color"
	"log"
	"strconv"
	"time"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/dialog"
	"fyne.io/fyne/v2/driver/desktop"
	"fyne.io/fyne/v2/widget"
	"fyne.io/systray"

	"teleportfling/assets"
	"teleportfling/internal/capture"
	"teleportfling/internal/config"
	"teleportfling/internal/flinger"
)

// errInvalidPort is returned when the port field contains a non-numeric or
// out-of-range value.
var errInvalidPort = errors.New("port must be 1–65535")

func itoa(v int) string { return strconv.Itoa(v) }

func atoi(s string) (int, error) { return strconv.Atoi(s) }

// scaleLabel renders a scale factor as a percentage option.
func scaleLabel(scale float64) string {
	switch {
	case scale >= 0.95:
		return "100%"
	case scale >= 0.7:
		return "75%"
	case scale >= 0.45:
		return "50%"
	default:
		return "25%"
	}
}

// parseScale converts a scale option label back to a factor.
func parseScale(label string) float64 {
	switch label {
	case "75%":
		return 0.75
	case "50%":
		return 0.5
	case "25%":
		return 0.25
	default:
		return 1.0
	}
}

// appID is the Fyne application ID used for preferences/settings storage.
const appID = "io.teleportfling"

// App is the desktop application shell.
type App struct {
	fyneApp fyne.App
	win     fyne.Window
	desk    desktop.App

	// configPath overrides the default config location ("" = default).
	configPath string

	cfg  config.Config
	eng  *flinger.Engine
	lock bool // serialises start/stop against UI actions

	// Tray state icons, built once at startup.
	iconIdle, iconActive *staticResource

	// UI state.
	startBtn    *widget.Button
	statusLab   *widget.Label
	portEnt     *widget.Entry
	qualitySel  *widget.Select
	fpsSel      *widget.Select
	presetSel   *widget.Select
	scaleSel    *widget.Select
	nameEnt     *widget.Entry
	audioChk    *widget.Check
	audioSel    *widget.Select
	audioDevs   []capture.AudioDevice
	announceChk *widget.Check
	srcSel      *widget.Select
	monSel      *widget.Select
	monitors    []capture.Monitor
	statsDone   chan struct{}

	// lastStart records the capture-affecting config the current engine was
	// created with, so Start can resume instead of reopening the portal.
	lastStart config.Config
}

// Run starts the GUI and blocks until the app exits. configPath selects a
// non-default settings file ("" uses the default location).
func Run(configPath string) {
	g := &App{configPath: configPath}

	g.fyneApp = app.NewWithID(appID)
	g.win = g.fyneApp.NewWindow("TeleportFling")
	g.fyneApp.SetIcon(fyne.NewStaticResource("teleportfling", assets.AppIcon))
	g.iconIdle = newTrayResource(color.NRGBA{R: 90, G: 90, B: 95, A: 255}, color.NRGBA{R: 60, G: 60, B: 65, A: 255})
	g.iconActive = newTrayResource(color.NRGBA{R: 46, G: 125, B: 50, A: 255}, color.NRGBA{R: 150, G: 220, B: 140, A: 255})

	// Load persisted settings (falling back to defaults).
	g.cfg = g.mustLoadConfig()

	g.buildUI()

	// Closing the window hides it (tray keeps the app alive) rather than
	// quitting, which is the expected behaviour for a tray app.
	g.win.SetCloseIntercept(func() {
		g.win.Hide()
	})

	g.setupTray()

	g.win.ShowAndRun()
}

// mustLoadConfig loads the config (from the configured path, or the default),
// logging and falling back to defaults on error.
func (g *App) mustLoadConfig() config.Config {
	var (
		c   config.Config
		err error
	)
	if g.configPath != "" {
		c, err = config.LoadFrom(g.configPath)
	} else {
		c, err = config.Load()
	}
	if err != nil {
		log.Printf("gui: config load: %v (using defaults)", err)
		return config.Default()
	}
	return c
}

// buildUI creates the settings form and wires its widgets to cfg.
func (g *App) buildUI() {
	// Stream identity.
	g.nameEnt = widget.NewEntry()
	g.nameEnt.SetPlaceHolder("Stream name (default: hostname)")
	g.nameEnt.SetText(g.cfg.Name)

	// Port.
	g.portEnt = widget.NewEntry()
	g.portEnt.SetText(itoa(g.cfg.Port))
	g.portEnt.Validator = func(s string) error {
		n, err := atoi(s)
		if err != nil || n < 1 || n > 65535 {
			return errInvalidPort
		}
		return nil
	}

	// Source.
	g.srcSel = widget.NewSelect([]string{"screen", "pattern"}, func(string) {})
	g.srcSel.SetSelected(g.cfg.Source)
	g.setupMonitorPicker()

	// Quality.
	g.qualitySel = widget.NewSelect([]string{"50", "60", "70", "80", "90", "100"}, g.applyLiveSettings)
	g.qualitySel.SetSelected(itoa(g.cfg.Quality))

	// FPS.
	g.fpsSel = widget.NewSelect([]string{"15", "30", "60"}, g.applyLiveSettings)
	g.fpsSel.SetSelected(itoa(g.cfg.FPS))

	// Scale: downsampling factor (1.0 = native, 0.5 = half, etc).
	g.scaleSel = widget.NewSelect([]string{"100%", "75%", "50%", "25%"}, g.applyLiveSettings)
	g.scaleSel.SetSelected(scaleLabel(g.cfg.Scale))

	// Preset: one-click quality/fps combos. Choosing one sets the Quality and
	// Frame rate selectors and applies them (live if running). Created after
	// the quality/fps selects so applyPreset's references are valid.
	g.presetSel = widget.NewSelect([]string{"Low", "Medium", "High", "Ultra"}, g.applyPreset)
	g.presetSel.SetSelected("High")

	// Audio.
	g.audioChk = widget.NewCheck("Capture system audio", func(bool) { g.applyLiveSettings("") })
	g.audioChk.SetChecked(g.cfg.Audio)
	g.setupAudioPicker()

	// Announce over multicast.
	g.announceChk = widget.NewCheck("Announce on LAN", nil)
	announce := true
	if g.cfg.Announce != nil {
		announce = *g.cfg.Announce
	}
	g.announceChk.SetChecked(announce)

	// Status label.
	g.statusLab = widget.NewLabel("Stopped")
	g.statusLab.Importance = widget.MediumImportance

	// Start/stop toggle.
	g.startBtn = widget.NewButton("Start", g.toggleStream)
	g.startBtn.Importance = widget.HighImportance

	form := &widget.Form{
		Items: []*widget.FormItem{
			{Text: "Name", Widget: g.nameEnt},
			{Text: "Port", Widget: g.portEnt},
			{Text: "Source", Widget: g.srcSel},
			{Text: "Monitor", Widget: g.monSel},
			{Text: "Preset", Widget: g.presetSel},
			{Text: "Quality", Widget: g.qualitySel},
			{Text: "Frame rate", Widget: g.fpsSel},
			{Text: "Scale", Widget: g.scaleSel},
			{Text: "Audio", Widget: g.audioChk},
			{Text: "Audio source", Widget: g.audioSel},
			{Text: "", Widget: g.announceChk},
		},
	}

	content := container.NewVBox(
		widget.NewLabelWithStyle("TeleportFling", fyne.TextAlignCenter, fyne.TextStyle{Bold: true}),
		form,
		g.statusLab,
		g.startBtn,
	)

	g.win.SetContent(container.NewBorder(nil, content, nil, nil, nil))
	g.win.Resize(fyne.NewSize(380, 0))
}

// setupMonitorPicker populates the monitor dropdown and ties its visibility
// to the source selector. When monitor enumeration is unavailable (non-
// Hyprland), it falls back to a raw index entry driven by the saved config.
func (g *App) setupMonitorPicker() {
	// Populate monitor names for the picker.
	g.monitors, _ = capture.ListMonitors()
	names := make([]string, 0, len(g.monitors))
	for _, m := range g.monitors {
		names = append(names, fmt.Sprintf("%s (%dx%d)", m.Name, m.Width, m.Height))
	}

	// If we could not enumerate, present the saved index as a single option.
	if len(names) == 0 {
		names = []string{fmt.Sprintf("Monitor %d", g.cfg.StreamIndex)}
		g.monitors = []capture.Monitor{{Index: g.cfg.StreamIndex, Name: fmt.Sprintf("Monitor %d", g.cfg.StreamIndex)}}
	}

	g.monSel = widget.NewSelect(names, func(string) {})
	if len(g.monitors) > 0 {
		// Preselect the configured index if it's within range.
		for i, m := range g.monitors {
			if m.Index == g.cfg.StreamIndex {
				g.monSel.SetSelectedIndex(i)
				break
			}
		}
	}

	// Monitor picker only applies to the "screen" source.
	g.srcSel.OnChanged = func(string) {
		g.monSel.Disable()
		if g.srcSel.Selected == "screen" {
			g.monSel.Enable()
		}
	}
	g.monSel.Disable()
	if g.cfg.Source == "screen" {
		g.monSel.Enable()
	}
}

// selectedMonitorIndex returns the monitor index chosen in the picker, or the
// saved config value when the picker is unavailable/disabled.
func (g *App) selectedMonitorIndex() int {
	if g.monSel != nil && g.monSel.SelectedIndex() >= 0 && g.monSel.SelectedIndex() < len(g.monitors) {
		return g.monitors[g.monSel.SelectedIndex()].Index
	}
	return g.cfg.StreamIndex
}

// setupAudioPicker populates the audio source dropdown from PipeWire. The
// first option is "Default output"; the rest are the enumerated sinks and
// microphones. A no-op if enumeration is unavailable.
func (g *App) setupAudioPicker() {
	g.audioDevs, _ = capture.ListAudioSources()

	names := []string{"Default output"}
	for _, d := range g.audioDevs {
		label := d.Desc
		if label == "" {
			label = d.Name
		}
		if d.IsOutput {
			label = "Output: " + label
		} else {
			label = "Input: " + label
		}
		names = append(names, label)
	}

	g.audioSel = widget.NewSelect(names, func(string) { g.applyLiveSettings("") })

	// Preselect the configured serial if it matches an enumerated device.
	if g.cfg.AudioSource > 0 {
		for i, d := range g.audioDevs {
			if d.Serial == g.cfg.AudioSource {
				g.audioSel.SetSelectedIndex(i + 1)
				break
			}
		}
	} else {
		g.audioSel.SetSelectedIndex(0)
	}
}

// selectedAudioSerial returns the PipeWire serial chosen in the picker, or 0
// for the default output.
func (g *App) selectedAudioSerial() uint64 {
	if g.audioSel == nil || g.audioSel.SelectedIndex() <= 0 {
		return 0
	}
	idx := g.audioSel.SelectedIndex() - 1
	if idx >= 0 && idx < len(g.audioDevs) {
		return g.audioDevs[idx].Serial
	}
	return 0
}

// applyPreset applies a named quality/fps preset to the Quality and Frame
// rate selectors, then pushes it live if the engine is running.
func (g *App) applyPreset(string) {
	var q, f int
	switch g.presetSel.Selected {
	case "Low":
		q, f = 50, 15
	case "Medium":
		q, f = 70, 30
	case "Ultra":
		q, f = 100, 60
	default: // High
		q, f = 85, 30
	}
	g.qualitySel.SetSelected(itoa(q))
	g.fpsSel.SetSelected(itoa(f))
	g.applyLiveSettings("")
}

// applyLiveSettings pushes the current form values (quality, fps, name,
// audio, announce) into a running engine via SetConfig so changes take
// effect without restarting the stream. When the engine is not running it is
// a no-op; the values are still captured on the next Start.
func (g *App) applyLiveSettings(string) {
	if g.eng == nil {
		return
	}
	quality, _ := atoi(g.qualitySel.Selected)
	fps, _ := atoi(g.fpsSel.Selected)
	announce := g.announceChk.Checked
	cfg := flinger.Config{
		Name:        g.nameEnt.Text,
		Port:        g.cfg.Port,
		Quality:     quality,
		FPS:         fps,
		Source:      g.cfg.Source,
		Audio:       g.audioChk.Checked,
		AudioSource: g.selectedAudioSerial(),
		StreamIndex: g.cfg.StreamIndex,
		Scale:       parseScale(g.scaleSel.Selected),
		Announce:    announce,
	}
	if err := g.eng.SetConfig(cfg); err != nil {
		log.Printf("gui: live settings: %v", err)
		return
	}
	// Keep the persisted config in sync with what we just applied.
	g.cfg.Quality = quality
	g.cfg.FPS = fps
	g.cfg.Audio = cfg.Audio
	g.cfg.AudioSource = cfg.AudioSource
	g.cfg.Name = cfg.Name
	g.cfg.Scale = cfg.Scale
	ann := announce
	g.cfg.Announce = &ann
}

// toggleStream starts or stops the engine based on current UI state.
func (g *App) toggleStream() {
	if g.lock {
		return
	}
	// Engine exists and is currently running → pause it.
	if g.eng != nil && g.eng.Status().Running {
		g.stop()
		return
	}
	g.start()
}

// start reads the form into cfg, saves it, and boots the engine. If an engine
// already exists and the capture-affecting settings are unchanged, it resumes
// the paused engine instead of reopening the portal session (which cannot be
// reliably re-created in-process).
func (g *App) start() {
	port, _ := atoi(g.portEnt.Text)
	quality, _ := atoi(g.qualitySel.Selected)
	fps, _ := atoi(g.fpsSel.Selected)

	announce := g.announceChk.Checked
	newCfg := config.Config{
		Name:        g.nameEnt.Text,
		Port:        port,
		Quality:     quality,
		FPS:         fps,
		Source:      g.srcSel.Selected,
		Audio:       g.audioChk.Checked,
		AudioSource: g.selectedAudioSerial(),
		StreamIndex: g.selectedMonitorIndex(),
		Scale:       parseScale(g.scaleSel.Selected),
		Announce:    &announce,
	}
	g.cfg = newCfg
	if g.configPath != "" {
		if err := config.SaveTo(g.configPath, g.cfg); err != nil {
			log.Printf("gui: config save: %v", err)
		}
	} else if err := config.Save(g.cfg); err != nil {
		log.Printf("gui: config save: %v", err)
	}

	// Resume the existing engine if capture-affecting fields are unchanged.
	if g.eng != nil && captureConfigEqual(g.lastStart, newCfg) {
		// Push live-applicable changes, then resume.
		g.applyLiveSettings("")
		g.eng.Resume()
		g.startedUI(newCfg)
		return
	}

	// Otherwise close any existing engine and create a fresh one.
	if g.eng != nil {
		g.eng.Close()
		g.eng = nil
	}

	eng, err := flinger.New(g.cfg.ToFlinger())
	if err != nil {
		dialog.ShowError(err, g.win)
		return
	}
	g.eng = eng
	g.lastStart = newCfg
	g.eng.Start()

	g.startedUI(newCfg)
}

// captureConfigEqual reports whether two configs agree on the fields that
// require reopening the capture session (source, port, monitor, audio
// source). Live-applicable fields (quality, fps, scale, name, announce,
// audio-on) are ignored.
func captureConfigEqual(a, b config.Config) bool {
	return a.Source == b.Source && a.Port == b.Port &&
		a.StreamIndex == b.StreamIndex && a.AudioSource == b.AudioSource
}

// startedUI updates the UI to the streaming state after a start/resume.
func (g *App) startedUI(cfg config.Config) {
	g.startBtn.SetText("Stop")
	g.startBtn.Importance = widget.DangerImportance
	g.statusLab.SetText("Streaming (port " + itoa(cfg.Port) + ")")
	g.statusLab.Importance = widget.SuccessImportance
	g.setTrayState(true, "TeleportFling · Streaming")
	g.refresh()
	g.watchStats()
}

// watchStats refreshes the status label with live counters while streaming.
func (g *App) watchStats() {
	done := make(chan struct{})
	g.statsDone = done
	go func() {
		tick := time.NewTicker(2 * time.Second)
		defer tick.Stop()
		for {
			select {
			case <-tick.C:
				if g.eng == nil {
					return
				}
				st := g.eng.Status()
				frames := itoa(int(st.Frames))
				dropped := itoa(int(st.Dropped))
				// Fyne UI calls must run on the main thread.
				fyne.Do(func() {
					g.statusLab.SetText(formatStatus(st))
					if st.Err != nil {
						g.statusLab.Importance = widget.DangerImportance
					} else {
						g.statusLab.Importance = widget.SuccessImportance
					}
					tip := "TeleportFling · " + frames + " frames, " + dropped + " dropped"
					if st.Bitrate > 0 {
						tip += " · " + formatBitrate(st.Bitrate)
					}
					if st.Err != nil {
						tip += " · error"
					}
					g.setTrayState(true, tip)
				})
			case <-done:
				return
			}
		}
	}()
}

// formatStatus renders the live status line.
func formatStatus(st flinger.Status) string {
	base := "Streaming · " + itoa(int(st.Frames)) + " frames"
	if st.Dropped > 0 {
		base += " · " + itoa(int(st.Dropped)) + " dropped"
	}
	if st.Bitrate > 0 {
		base += " · " + formatBitrate(st.Bitrate)
	}
	if st.Err != nil {
		base += "\nError: " + st.Err.Error()
	}
	return base
}

// formatBitrate renders a bits/sec value in a human-readable form.
func formatBitrate(bps int64) string {
	switch {
	case bps >= 1_000_000:
		return fmt.Sprintf("%.1f Mbps", float64(bps)/1_000_000)
	case bps >= 1_000:
		return fmt.Sprintf("%.0f kbps", float64(bps)/1_000)
	default:
		return fmt.Sprintf("%d bps", bps)
	}
}

// stop pauses the engine (keeping the portal session open) and returns the
// UI to the stopped state.
func (g *App) stop() {
	if g.statsDone != nil {
		close(g.statsDone)
		g.statsDone = nil
	}
	if g.eng != nil {
		g.eng.Stop()
	}
	g.startBtn.SetText("Start")
	g.startBtn.Importance = widget.HighImportance
	g.statusLab.SetText("Stopped")
	g.statusLab.Importance = widget.MediumImportance
	g.setTrayState(false, "TeleportFling")
	g.refresh()
}

// refresh forces the window to repaint (state/importance changed).
func (g *App) refresh() {
	g.startBtn.Refresh()
	g.statusLab.Refresh()
}

// setupTray registers the system tray menu and window. If the platform driver
// does not support a tray (older Fyne/desktops), this is a no-op and the
// window close intercept simply won't hide.
func (g *App) setupTray() {
	desk, ok := g.fyneApp.(desktop.App)
	if !ok {
		log.Printf("gui: system tray not supported on this desktop")
		return
	}
	g.desk = desk

	m := fyne.NewMenu("TeleportFling",
		fyne.NewMenuItem("Show", func() {
			// Show is a no-op if the window is already visible, so also raise
			// and focus it to bring it to the foreground.
			g.win.Show()
			g.win.RequestFocus()
		}),
		fyne.NewMenuItemSeparator(),
		fyne.NewMenuItem("Start", g.toggleStream),
		fyne.NewMenuItem("Stop", func() {
			if g.eng != nil {
				g.stop()
			}
		}),
		fyne.NewMenuItemSeparator(),
		fyne.NewMenuItem("Quit", func() {
			if g.eng != nil {
				g.eng.Stop()
			}
			g.fyneApp.Quit()
		}),
	)
	desk.SetSystemTrayMenu(m)
	// Left-clicking the tray icon shows the settings window.
	desk.SetSystemTrayWindow(g.win)
	g.win.SetOnClosed(func() { g.fyneApp.Quit() })

	// Show the "stopped" state icon initially.
	g.setTrayState(false, "TeleportFling")
}

// setTrayState swaps the tray icon and tooltip to reflect the streaming state.
// It is a no-op if the tray is unavailable.
func (g *App) setTrayState(streaming bool, tooltip string) {
	if g.desk == nil || g.iconIdle == nil || g.iconActive == nil {
		return
	}
	icon := fyne.Resource(g.iconIdle)
	if streaming {
		icon = g.iconActive
	}
	g.desk.SetSystemTrayIcon(icon)
	systray.SetTooltip(tooltip)
}