// Package tray is the fast path: the tray icon, its grouped preset menu, and
// the confirm-then-apply flow.
//
// Everything here is driven by systray's callbacks, which run on the UI
// goroutine. Nothing slow may happen inline — a netsh apply takes one to three
// seconds and would freeze the menu — so every click handler hands off to a
// goroutine immediately.
package tray

import (
	"context"
	_ "embed"
	"errors"
	"fmt"
	"log"
	"sync"
	"time"

	"fyne.io/systray"

	"gitea.apointless.space/bsncubed/ipswap/internal/config"
	"gitea.apointless.space/bsncubed/ipswap/internal/desktop"
	"gitea.apointless.space/bsncubed/ipswap/internal/dialog"
	"gitea.apointless.space/bsncubed/ipswap/internal/elevate"
	"gitea.apointless.space/bsncubed/ipswap/internal/netcfg"
	"gitea.apointless.space/bsncubed/ipswap/internal/preset"
	"gitea.apointless.space/bsncubed/ipswap/internal/server"
	"gitea.apointless.space/bsncubed/ipswap/internal/switcher"
	"gitea.apointless.space/bsncubed/ipswap/internal/updater"
)

//go:embed icon.ico
var iconICO []byte

// App owns the tray and everything it talks to.
type App struct {
	Store    *preset.Store
	Switcher *switcher.Switcher
	Server   *server.Server
	Paths    config.Paths
	Version  string

	// OpenOnStart opens the editor as soon as the tray is up. Set for a
	// launch from the shortcut, cleared for the start-with-Windows launch —
	// nobody wants a browser tab at login.
	OpenOnStart bool

	mu       sync.Mutex
	settings config.Settings
	// activeID is the preset currently matching the live adapter state, empty
	// when nothing matches.
	activeID string
	// pendingUpdate is set once the update check finds a newer release.
	pendingUpdate *updater.Update

	// menuGen is closed and replaced on every menu rebuild, so the click
	// listeners attached to the previous set of items exit instead of leaking
	// a goroutine per rebuild.
	menuGen chan struct{}

	titleItem  *systray.MenuItem
	updateItem *systray.MenuItem
	// presetItems maps preset id to its menu entry, for the check marks.
	presetItems map[string]*systray.MenuItem

	elevated bool
}

// New builds the tray application.
func New(store *preset.Store, sw *switcher.Switcher, srv *server.Server, paths config.Paths, settings config.Settings, version string) *App {
	return &App{
		Store:    store,
		Switcher: sw,
		Server:   srv,
		Paths:    paths,
		Version:  version,
		settings: settings,
		elevated: elevate.IsElevated(),
	}
}

// Run blocks until the user exits. It must be called from the main goroutine.
func (a *App) Run() {
	a.Server.OnPresetsChange(func() {
		// The editor changed something; rebuild on the UI goroutine.
		go a.rebuild()
	})
	a.Server.OnSettingsChange(a.applySettings)
	a.Server.OnApplied(func() {
		// A switch made in the browser must move the tray's check mark too.
		go a.refreshActive()
	})

	systray.Run(a.onReady, a.onExit)
}

func (a *App) onReady() {
	systray.SetIcon(iconICO)
	systray.SetTitle(config.AppName)
	systray.SetTooltip(config.AppName)

	a.build()

	go a.pollActive()
	go a.checkUpdatesOnStartup()

	if a.OpenOnStart {
		// After the menu exists, so a failure to open the browser still leaves
		// a usable tray icon behind.
		go a.OpenEditor()
	}
}

func (a *App) onExit() {
	a.Server.Stop()
	log.Printf("%s exiting", config.AppName)
}

// --- menu construction ---

func (a *App) rebuild() {
	systray.ResetMenu()
	a.build()
	a.refreshActive()
}

func (a *App) build() {
	a.mu.Lock()
	if a.menuGen != nil {
		close(a.menuGen) // retire the previous generation's listeners
	}
	gen := make(chan struct{})
	a.menuGen = gen
	pending := a.pendingUpdate
	a.mu.Unlock()

	// Update offer sits at the very top when there is one.
	updateItem := systray.AddMenuItem("", "A newer release is available")
	updateItem.Hide()
	if pending != nil {
		updateItem.SetTitle(fmt.Sprintf("Update available — v%s", pending.Version))
		updateItem.Show()
	}
	a.onClick(gen, updateItem, a.doUpdate)

	titleItem := systray.AddMenuItem(config.AppName, "The preset currently applied")
	titleItem.Disable()
	systray.AddSeparator()

	// Groups become submenus. A flat list of fifty presets is unusable, so
	// this is not optional even when there are only a handful.
	presets := a.Store.All()
	if len(presets) == 0 {
		empty := systray.AddMenuItem("No presets yet — use Manage presets…", "")
		empty.Disable()
	}

	items := make(map[string]*systray.MenuItem, len(presets))
	var currentGroup string
	var sub *systray.MenuItem
	for _, p := range presets {
		g := p.GroupOrUngrouped()
		if g != currentGroup || sub == nil {
			currentGroup = g
			sub = systray.AddMenuItem(g, "")
		}
		item := sub.AddSubMenuItemCheckbox(p.Name, p.Notes, false)
		items[p.ID] = item

		id := p.ID
		a.onClick(gen, item, func() { a.applyPreset(id) })
	}

	// The menu is built on the UI goroutine but read by the active-preset
	// poller, so every handle it touches is published under the lock.
	a.mu.Lock()
	a.presetItems = items
	a.titleItem = titleItem
	a.updateItem = updateItem
	a.mu.Unlock()

	systray.AddSeparator()

	manage := systray.AddMenuItem("Manage presets…", "Open the preset editor in your browser")
	a.onClick(gen, manage, a.OpenEditor)

	check := systray.AddMenuItem("Check for updates", "")
	a.onClick(gen, check, a.checkUpdatesNow)

	if !a.elevated {
		systray.AddSeparator()
		relaunch := systray.AddMenuItem("Relaunch as administrator", "Applying a preset needs an elevated process")
		a.onClick(gen, relaunch, a.relaunch)
	}

	systray.AddSeparator()
	quit := systray.AddMenuItem("Exit", "")
	a.onClick(gen, quit, func() { systray.Quit() })
}

// onClick runs fn on its own goroutine for every click, until this menu
// generation is retired.
func (a *App) onClick(gen <-chan struct{}, item *systray.MenuItem, fn func()) {
	go func() {
		for {
			select {
			case <-gen:
				return
			case _, ok := <-item.ClickedCh:
				if !ok {
					return
				}
				go fn()
			}
		}
	}()
}

// --- actions ---

// applyPreset is the whole fast path: read the live config, show the diff,
// and on a Yes run the netsh plan.
func (a *App) applyPreset(id string) {
	p, live, err := a.Switcher.Preview(id)
	if err != nil {
		if errors.Is(err, switcher.ErrNotFound) {
			dialog.Error(config.AppName, "That preset no longer exists.")
			return
		}
		dialog.Error(config.AppName, fmt.Sprintf("Could not read the adapter.\n\n%v", err))
		return
	}

	if !dialog.Confirm(config.AppName, netcfg.ConfirmText(p, live)) {
		log.Printf("apply of %q cancelled at the prompt", p.Name)
		return
	}

	if err := a.Switcher.Apply(id); err != nil {
		if isElevationErr(err) && !a.elevated {
			if dialog.ErrorWithRetryAsAdmin(config.AppName,
				fmt.Sprintf("Applying %q needs administrator rights.", p.Name)) {
				a.relaunch()
			}
			return
		}
		dialog.Error(config.AppName, fmt.Sprintf("Applying %q failed.\n\n%v", p.Name, err))
		return
	}

	a.refreshActive()
}

// OpenEditor starts the editor server if needed and opens the browser at it.
// Exported because a second launch of ipswap reaches this through the control
// channel rather than starting a tray of its own.
func (a *App) OpenEditor() {
	url, err := a.Server.Start()
	if err != nil {
		dialog.Error(config.AppName, fmt.Sprintf("Could not start the preset editor.\n\n%v", err))
		return
	}
	if err := desktop.OpenURL(url); err != nil {
		// The server is up, so give the user the address rather than just failing.
		dialog.Error(config.AppName, fmt.Sprintf(
			"Could not open your browser. Paste this address into it:\n\n%s\n\n%v", url, err))
	}
}

func (a *App) relaunch() {
	if err := elevate.RelaunchAsAdmin(); err != nil {
		log.Printf("relaunch as admin failed: %v", err)
		return
	}
	systray.Quit()
}

func (a *App) applySettings(c config.Settings) {
	a.mu.Lock()
	a.settings = c
	a.mu.Unlock()

	if err := desktop.SetRunAtLogin(c.StartWithWindows); err != nil {
		log.Printf("updating the start-with-Windows setting: %v", err)
	}
}

func (a *App) currentSettings() config.Settings {
	a.mu.Lock()
	defer a.mu.Unlock()
	return a.settings
}

// --- active preset detection ---

// pollActive re-reads the live adapter state on a timer so the check mark and
// tooltip stay right when something outside ipswap changes the network.
func (a *App) pollActive() {
	a.refreshActive()

	interval := time.Duration(a.currentSettings().ActivePollSeconds) * time.Second
	t := time.NewTicker(interval)
	defer t.Stop()
	for range t.C {
		a.refreshActive()
	}
}

func (a *App) refreshActive() {
	st := a.Switcher.Active()
	activeID, activeName := st.ActiveID, st.ActiveName

	a.mu.Lock()
	a.activeID = activeID
	items := a.presetItems
	title := a.titleItem
	a.mu.Unlock()

	for id, item := range items {
		if id == activeID {
			item.Check()
		} else {
			item.Uncheck()
		}
	}

	label := config.AppName + " — unmatched"
	if activeName != "" {
		label = config.AppName + " — " + activeName
	}
	systray.SetTooltip(label)
	if title != nil {
		title.SetTitle(label)
	}
}

// --- updates ---

func (a *App) checkUpdatesOnStartup() {
	if !a.currentSettings().CheckUpdates {
		return
	}
	// Never block startup on the network, and never surface a failure: a
	// laptop on a customer site usually cannot reach the Gitea host.
	if _, err := a.checkUpdates(); err != nil {
		log.Printf("startup update check failed (ignored): %v", err)
	}
}

// checkUpdatesNow is the menu-driven check, which does report its result.
func (a *App) checkUpdatesNow() {
	up, err := a.checkUpdates()
	switch {
	case err != nil:
		dialog.Error(config.AppName, fmt.Sprintf("Could not check for updates.\n\n%v", err))
	case up == nil:
		dialog.Info(config.AppName, fmt.Sprintf("%s v%s is up to date.", config.AppName, a.Version))
	default:
		dialog.Info(config.AppName, fmt.Sprintf(
			"%s v%s is available.\n\nChoose \"Update available\" in the tray menu to install it.", config.AppName, up.Version))
	}
}

func (a *App) checkUpdates() (*updater.Update, error) {
	s := a.currentSettings()
	if s.UpdateRepo == "" {
		return nil, fmt.Errorf("no update repository is configured (set one in Settings)")
	}

	c := &updater.Checker{Repo: s.UpdateRepo, Current: a.Version}
	up, err := c.Check(context.Background())
	if err != nil {
		return nil, err
	}

	a.mu.Lock()
	a.pendingUpdate = up
	item := a.updateItem
	a.mu.Unlock()

	if up != nil && item != nil {
		item.SetTitle(fmt.Sprintf("Update available — v%s", up.Version))
		item.Show()
	}
	return up, nil
}

// doUpdate downloads, verifies and installs. Nothing here happens without the
// user having clicked the update item first.
func (a *App) doUpdate() {
	a.mu.Lock()
	up := a.pendingUpdate
	repo := a.settings.UpdateRepo
	a.mu.Unlock()
	if up == nil {
		return
	}

	if !dialog.Confirm(config.AppName, fmt.Sprintf(
		"Download and install %s v%s?\n\n%s will close and reopen once the update is in place.",
		config.AppName, up.Version, config.AppName)) {
		return
	}

	c := &updater.Checker{Repo: repo, Current: a.Version}
	path, err := c.Download(context.Background(), up, tempDir())
	if err != nil {
		dialog.Error(config.AppName, fmt.Sprintf("The update could not be downloaded.\n\n%v", err))
		return
	}

	if err := updater.InstallAndRestart(path); err != nil {
		dialog.Error(config.AppName, fmt.Sprintf("The update could not be installed.\n\n%v", err))
		return
	}
	systray.Quit()
}