// Command das-welcome is the Das OS first-login window: interface language,
// home folder names, updates, settings and help.
//
//	das-welcome              show the window
//	das-welcome --autostart  show it only if the user did not turn that off
package main

import (
	"context"
	"flag"
	"fmt"
	"html"
	"os"
	"os/exec"
	"path/filepath"
	"strings"

	"github.com/gotk3/gotk3/glib"
	"github.com/gotk3/gotk3/gtk"

	"dasos/tools/internal/i18n"
	"dasos/tools/internal/system"
	"dasos/tools/internal/userdirs"
)

const (
	appID   = "ua.org.das.Welcome"
	helpURL = "https://git.das.org.ua/das/Das-OS"
)

func main() {
	autostart := flag.Bool("autostart", false, "show the window only if it is enabled at login")
	flag.Parse()

	if *autostart && !showAtLogin() {
		return
	}
	app, err := gtk.ApplicationNew(appID, glib.APPLICATION_FLAGS_NONE)
	if err != nil {
		fmt.Fprintln(os.Stderr, "das-welcome:", err)
		os.Exit(1)
	}
	var win *gtk.ApplicationWindow
	app.Connect("activate", func() {
		if win != nil {
			win.Present()
			return
		}
		win, err = newWindow(app)
		if err != nil {
			fmt.Fprintln(os.Stderr, "das-welcome:", err)
			app.Quit()
			return
		}
		win.ShowAll()
	})
	os.Exit(app.Run(nil))
}

// settingsFile records whether the window opens at login. Without it the
// window opens once: at the first login of a user (or every live session).
func settingsFile() string {
	dir := os.Getenv("XDG_CONFIG_HOME")
	if dir == "" {
		dir = filepath.Join(os.Getenv("HOME"), ".config")
	}
	return filepath.Join(dir, "das", "welcome")
}

func showAtLogin() bool {
	data, err := os.ReadFile(settingsFile())
	if err != nil {
		return true
	}
	return strings.TrimSpace(string(data)) == "autostart=true"
}

func setShowAtLogin(on bool) error {
	path := settingsFile()
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	return os.WriteFile(path, []byte(fmt.Sprintf("autostart=%v\n", on)), 0o644)
}

// builder collects the first error of a chain of gotk3 constructors.
type builder struct{ err error }

func (b *builder) check(err error) {
	if b.err == nil {
		b.err = err
	}
}

func (b *builder) label(text string, wrap bool) *gtk.Label {
	l, err := gtk.LabelNew(text)
	b.check(err)
	if err == nil {
		l.SetXAlign(0)
		l.SetLineWrap(wrap)
	}
	return l
}

func (b *builder) button(text string, onClick func()) *gtk.Button {
	btn, err := gtk.ButtonNewWithLabel(text)
	b.check(err)
	if err == nil {
		btn.SetVAlign(gtk.ALIGN_CENTER)
		btn.Connect("clicked", onClick)
	}
	return btn
}

// row is one entry of the list: icon, title, description and controls.
func (b *builder) row(icon, title, desc string, controls ...gtk.IWidget) (*gtk.Box, *gtk.Label) {
	box, err := gtk.BoxNew(gtk.ORIENTATION_HORIZONTAL, 14)
	b.check(err)
	img, err := gtk.ImageNewFromIconName(icon, gtk.ICON_SIZE_DND)
	b.check(err)
	text, err := gtk.BoxNew(gtk.ORIENTATION_VERTICAL, 2)
	b.check(err)
	if b.err != nil {
		return box, nil
	}
	img.SetPixelSize(32)
	t := b.label("", false)
	t.SetMarkup("<b>" + html.EscapeString(title) + "</b>")
	d := b.label(desc, true)
	if style, err := d.GetStyleContext(); err == nil {
		style.AddClass("dim-label")
	}
	text.PackStart(t, false, false, 0)
	text.PackStart(d, false, false, 0)
	box.PackStart(img, false, false, 0)
	box.PackStart(text, true, true, 0)
	for _, c := range controls {
		box.PackEnd(c, false, false, 0)
	}
	return box, d
}

func newWindow(app *gtk.Application) (*gtk.ApplicationWindow, error) {
	b := &builder{}
	win, err := gtk.ApplicationWindowNew(app)
	if err != nil {
		return nil, err
	}
	win.SetTitle(i18n.T("welcome.title"))
	win.SetIconName("das-logo")
	win.SetDefaultSize(640, -1)
	win.SetPosition(gtk.WIN_POS_CENTER)

	outer, err := gtk.BoxNew(gtk.ORIENTATION_VERTICAL, 16)
	b.check(err)
	if b.err != nil {
		return nil, b.err
	}
	outer.SetMarginStart(24)
	outer.SetMarginEnd(24)
	outer.SetMarginTop(24)
	outer.SetMarginBottom(18)

	header, err := gtk.BoxNew(gtk.ORIENTATION_HORIZONTAL, 16)
	b.check(err)
	logo, err := gtk.ImageNewFromIconName("das-logo", gtk.ICON_SIZE_DIALOG)
	b.check(err)
	titles, err := gtk.BoxNew(gtk.ORIENTATION_VERTICAL, 4)
	b.check(err)
	if b.err != nil {
		return nil, b.err
	}
	logo.SetPixelSize(72)
	title := b.label("", false)
	title.SetMarkup(`<span size="xx-large" weight="bold">` + html.EscapeString(i18n.T("welcome.title")) + "</span>")
	titles.SetVAlign(gtk.ALIGN_CENTER)
	titles.PackStart(title, false, false, 0)
	titles.PackStart(b.label(i18n.T("welcome.subtitle"), true), false, false, 0)
	header.PackStart(logo, false, false, 0)
	header.PackStart(titles, true, true, 0)
	outer.PackStart(header, false, false, 0)

	list, err := gtk.BoxNew(gtk.ORIENTATION_VERTICAL, 14)
	b.check(err)
	add := func(row *gtk.Box) {
		if sep, err := gtk.SeparatorNew(gtk.ORIENTATION_HORIZONTAL); err == nil {
			list.PackStart(sep, false, false, 0)
		}
		list.PackStart(row, false, false, 0)
	}

	if system.IsLive() {
		install := b.button(i18n.T("welcome.install"), func() { launch("das-install") })
		if style, err := install.GetStyleContext(); err == nil {
			style.AddClass("suggested-action")
		}
		row, _ := b.row("das-logo", i18n.T("welcome.install"), i18n.T("welcome.install.desc"), install)
		add(row)
	}
	if row := languageRow(b); row != nil {
		add(row)
	}
	if row := foldersRow(b); row != nil {
		add(row)
	}
	if !system.IsLive() {
		row, _ := b.row("software-update-available", i18n.T("welcome.update"), i18n.T("welcome.update.desc"),
			b.button(i18n.T("welcome.update.open"), func() { launch("das-update") }))
		add(row)
	}
	row, _ := b.row("preferences-desktop", i18n.T("welcome.settings"), i18n.T("welcome.settings.desc"),
		b.button(i18n.T("welcome.open"), func() { launch("xfce4-settings-manager") }))
	add(row)
	row, _ = b.row("help-browser", i18n.T("welcome.help"), i18n.T("welcome.help.desc"),
		b.button(i18n.T("welcome.open"), func() { launch("xdg-open", helpURL) }))
	add(row)
	outer.PackStart(list, false, false, 0)

	footer, err := gtk.BoxNew(gtk.ORIENTATION_HORIZONTAL, 12)
	b.check(err)
	autostart, err := gtk.CheckButtonNewWithLabel(i18n.T("welcome.autostart"))
	b.check(err)
	if b.err != nil {
		return nil, b.err
	}
	// The window opens by itself only once unless the user asks for more.
	autostart.SetActive(false)
	if _, err := os.Stat(settingsFile()); err == nil {
		autostart.SetActive(showAtLogin())
	} else if err := setShowAtLogin(false); err != nil {
		fmt.Fprintln(os.Stderr, "das-welcome:", err)
	}
	autostart.Connect("toggled", func() {
		if err := setShowAtLogin(autostart.GetActive()); err != nil {
			fmt.Fprintln(os.Stderr, "das-welcome:", err)
		}
	})
	footer.PackStart(autostart, false, false, 0)
	footer.PackEnd(b.button(i18n.T("welcome.close"), func() { win.Close() }), false, false, 0)
	outer.PackEnd(footer, false, false, 0)

	win.Add(outer)
	return win, b.err
}

func launch(name string, args ...string) {
	if err := exec.Command(name, args...).Start(); err != nil {
		fmt.Fprintln(os.Stderr, "das-welcome:", err)
	}
}

// languageRow offers the UTF-8 locales the system has built. It returns nil
// when there is nothing to choose from.
func languageRow(b *builder) *gtk.Box {
	locales := availableLocales()
	if len(locales) < 2 {
		return nil
	}
	combo, err := gtk.ComboBoxTextNew()
	b.check(err)
	if err != nil {
		return nil
	}
	current := currentLocale()
	for _, l := range locales {
		combo.Append(l, localeName(l))
	}
	if !combo.SetActiveID(current) {
		combo.SetActive(0)
	}
	combo.SetVAlign(gtk.ALIGN_CENTER)

	var desc *gtk.Label
	apply := b.button(i18n.T("welcome.apply"), func() {
		if err := setLanguage(combo.GetActiveID()); err != nil {
			desc.SetText(i18n.T("welcome.error", err))
			return
		}
		desc.SetText(i18n.T("welcome.lang.done"))
	})
	row, d := b.row("preferences-desktop-locale", i18n.T("welcome.lang"), i18n.T("welcome.lang.desc"), apply, combo)
	desc = d
	return row
}

// foldersRow offers to rename home folders that kept English names.
func foldersRow(b *builder) *gtk.Box {
	home := os.Getenv("HOME")
	renames, err := pendingRenames(home)
	if err != nil {
		fmt.Fprintln(os.Stderr, "das-welcome:", err)
		return nil
	}
	if len(renames) == 0 {
		return nil
	}
	names := make([]string, len(renames))
	for i, r := range renames {
		names[i] = filepath.Base(r.From)
	}
	var desc *gtk.Label
	var rename *gtk.Button
	rename = b.button(i18n.T("welcome.dirs.rename"), func() {
		if err := userdirs.Apply(home, renames); err != nil {
			desc.SetText(i18n.T("welcome.error", err))
			return
		}
		desc.SetText(i18n.T("welcome.dirs.done"))
		rename.SetSensitive(false)
	})
	row, d := b.row("folder", i18n.T("welcome.dirs"), i18n.T("welcome.dirs.desc", strings.Join(names, ", ")), rename)
	desc = d
	return row
}

func pendingRenames(home string) ([]userdirs.Rename, error) {
	data, err := os.ReadFile(userdirs.ConfigFile(home))
	if os.IsNotExist(err) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	ctx := context.Background()
	english, err := userdirs.Defaults(ctx, "C.UTF-8")
	if err != nil {
		return nil, err
	}
	localized, err := userdirs.Defaults(ctx, "")
	if err != nil {
		return nil, err
	}
	return userdirs.Plan(home, userdirs.Parse(string(data)), english, localized), nil
}