package ui

import (
	"fmt"
	"os"
	"strings"
	"sync"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/dialog"
	"fyne.io/fyne/v2/theme"
	"fyne.io/fyne/v2/widget"
	"github.com/pkg/sftp"
	"golang.org/x/crypto/ssh"

	"gitea.apointless.space/bsncubed/haul/internal/sshconf"
	"gitea.apointless.space/bsncubed/haul/internal/sshx"
)

// connectWindow is haul's front door: the hosts already in ~/.ssh/config on one
// tab, an ad-hoc target on the other. It stays alive behind each session so
// closing a session returns here rather than quitting.
type connectWindow struct {
	app fyne.App
	win fyne.Window

	cfgPath  string
	hosts    []sshconf.Host // everything parsed from the config
	shown    []sshconf.Host // what the filter currently leaves visible
	list     *widget.List
	selected int

	qHost *widget.Entry
	qPort *widget.Entry
	qUser *widget.Entry
	qPass *widget.Entry
	qKey  *widget.Entry

	tabs       *container.AppTabs
	connectBtn *widget.Button
	status     *widget.Label
	loadErr    string // config problem found before the status label existed
}

func newConnectWindow(app fyne.App) *connectWindow {
	c := &connectWindow{
		app:      app,
		win:      app.NewWindow("haul"),
		selected: -1,
	}

	c.loadHosts()
	savedTab := container.NewTabItemWithIcon("Saved hosts", theme.ComputerIcon(), c.buildSavedTab())
	quickTab := container.NewTabItemWithIcon("Quick connect", theme.SearchIcon(), c.buildQuickTab())
	c.tabs = container.NewAppTabs(savedTab, quickTab)

	c.status = widget.NewLabel(c.loadErr)
	c.status.Wrapping = fyne.TextWrapWord
	c.connectBtn = widget.NewButtonWithIcon("Connect", theme.ConfirmIcon(), c.connect)
	c.connectBtn.Importance = widget.HighImportance

	bottom := container.NewBorder(widget.NewSeparator(), nil, nil, c.connectBtn, c.status)
	c.win.SetContent(container.NewBorder(nil, bottom, nil, nil, c.tabs))
	c.win.Resize(fyne.NewSize(620, 520))
	return c
}

// --- saved hosts ---

func (c *connectWindow) loadHosts() {
	path, err := sshconf.DefaultConfigPath()
	if err != nil {
		return
	}
	c.cfgPath = path
	hosts, err := sshconf.Parse(path)
	if err != nil {
		// A malformed config shouldn't stop haul launching — quick connect still
		// works — so the problem is held here and shown once the window is built.
		c.loadErr = "Could not read " + path + ": " + err.Error()
		return
	}
	c.hosts = hosts
	c.shown = hosts
}

func (c *connectWindow) buildSavedTab() fyne.CanvasObject {
	search := widget.NewEntry()
	search.SetPlaceHolder("Filter hosts…")
	search.OnChanged = c.filter

	c.list = widget.NewList(
		func() int { return len(c.shown) },
		func() fyne.CanvasObject {
			return container.NewVBox(
				widget.NewLabelWithStyle("", fyne.TextAlignLeading, fyne.TextStyle{Bold: true}),
				widget.NewLabel(""),
			)
		},
		func(id widget.ListItemID, o fyne.CanvasObject) {
			box, ok := o.(*fyne.Container)
			if !ok || id < 0 || id >= len(c.shown) {
				return
			}
			h := c.shown[id]
			alias := box.Objects[0].(*widget.Label)
			detail := box.Objects[1].(*widget.Label)
			alias.SetText(h.Alias)
			detail.SetText(describeHost(h))
		},
	)
	c.list.OnSelected = func(id widget.ListItemID) { c.selected = id }

	// The "no hosts" note is only added when it has something to say — an empty
	// label still occupies a full row, which reads as a rendering glitch.
	top := fyne.CanvasObject(search)
	if len(c.hosts) == 0 {
		note := widget.NewLabel("No hosts found in " + c.cfgPath + " — use Quick connect.")
		note.Wrapping = fyne.TextWrapWord
		top = container.NewVBox(search, note)
	}

	return container.NewBorder(top, nil, nil, nil, c.list)
}

// describeHost is the one-line summary under each alias in the list.
func describeHost(h sshconf.Host) string {
	target := h.HostName
	if target == "" {
		target = h.Alias
	}
	if h.User != "" {
		target = h.User + "@" + target
	}
	if h.Port != "" && h.Port != "22" {
		target += ":" + h.Port
	}
	if h.ProxyJump != "" {
		target += "  (via " + h.ProxyJump + ")"
	}
	if len(h.Tags) > 0 {
		target += "  [" + strings.Join(h.Tags, ", ") + "]"
	}
	return target
}

func (c *connectWindow) filter(q string) {
	q = strings.ToLower(strings.TrimSpace(q))
	if q == "" {
		c.shown = c.hosts
	} else {
		c.shown = nil
		for _, h := range c.hosts {
			if strings.Contains(strings.ToLower(h.Alias), q) ||
				strings.Contains(strings.ToLower(h.HostName), q) ||
				strings.Contains(strings.ToLower(strings.Join(h.Tags, " ")), q) {
				c.shown = append(c.shown, h)
			}
		}
	}
	c.selected = -1
	c.list.UnselectAll()
	c.list.Refresh()
}

// --- quick connect ---

func (c *connectWindow) buildQuickTab() fyne.CanvasObject {
	c.qHost = widget.NewEntry()
	c.qHost.SetPlaceHolder("hostname or IP")
	c.qPort = widget.NewEntry()
	c.qPort.SetText("22")
	c.qUser = widget.NewEntry()
	c.qUser.SetText(currentUser())
	c.qPass = widget.NewPasswordEntry()
	c.qPass.SetPlaceHolder("leave blank to use ssh-agent / key")
	c.qKey = widget.NewEntry()
	c.qKey.SetPlaceHolder("optional private key file")

	browse := widget.NewButtonWithIcon("", theme.FolderOpenIcon(), func() {
		dialog.ShowFileOpen(func(r fyne.URIReadCloser, err error) {
			if err != nil || r == nil {
				return
			}
			defer r.Close()
			c.qKey.SetText(r.URI().Path())
		}, c.win)
	})

	form := widget.NewForm(
		widget.NewFormItem("Host", c.qHost),
		widget.NewFormItem("Port", c.qPort),
		widget.NewFormItem("User", c.qUser),
		widget.NewFormItem("Password", c.qPass),
		widget.NewFormItem("Key file", container.NewBorder(nil, nil, nil, browse, c.qKey)),
	)
	// Enter anywhere in the form connects.
	c.qHost.OnSubmitted = func(string) { c.connect() }
	c.qPass.OnSubmitted = func(string) { c.connect() }

	note := widget.NewLabel("Quick connect doesn't touch ~/.ssh/config. An unrecognised host key is " +
		"shown for confirmation before it's recorded in known_hosts.")
	note.Wrapping = fyne.TextWrapWord

	return container.NewVBox(form, widget.NewSeparator(), note)
}

func currentUser() string {
	for _, k := range []string{"USER", "USERNAME", "LOGNAME"} {
		if v := os.Getenv(k); v != "" {
			return v
		}
	}
	return ""
}

// --- connecting ---

func (c *connectWindow) connect() {
	if c.tabs.SelectedIndex() == 1 {
		c.connectQuick()
		return
	}
	c.connectSaved()
}

func (c *connectWindow) connectSaved() {
	if c.selected < 0 || c.selected >= len(c.shown) {
		c.setStatus("Select a host first.")
		return
	}
	alias := c.shown[c.selected].Alias
	c.start(alias, "", func(opts sshx.Options) (*ssh.Client, error) {
		return sshx.Connect(alias, opts)
	})
}

func (c *connectWindow) connectQuick() {
	host := strings.TrimSpace(c.qHost.Text)
	if host == "" {
		c.setStatus("Enter a hostname.")
		return
	}
	// "user@host:port" typed into the host box is understood, since that's how
	// people paste a target.
	user := strings.TrimSpace(c.qUser.Text)
	port := strings.TrimSpace(c.qPort.Text)
	if u, rest, ok := strings.Cut(host, "@"); ok {
		user, host = u, rest
	}
	if h, p, ok := strings.Cut(host, ":"); ok {
		host, port = h, p
	}
	if port == "" {
		port = "22"
	}

	p := sshx.Params{
		Alias:    host,
		HostName: host,
		User:     user,
		Port:     port,
	}
	if key := strings.TrimSpace(c.qKey.Text); key != "" {
		p.IdentityFiles = []string{key}
		p.IdentitiesOnly = true
	}
	label := host
	if user != "" {
		label = user + "@" + host
	}
	c.start(label, c.qPass.Text, func(opts sshx.Options) (*ssh.Client, error) {
		return sshx.ConnectParams(p, opts)
	})
}

// start runs a connection attempt off the UI thread and opens a session window
// on success. dial is whichever sshx entry point the chosen tab implies.
func (c *connectWindow) start(name, password string, dial func(sshx.Options) (*ssh.Client, error)) {
	c.connectBtn.Disable()
	c.setStatus("Connecting to " + name + "…")

	go func() {
		var diagMu sync.Mutex
		var diag []string

		opts := c.sshOptions(password, func(format string, args ...any) {
			diagMu.Lock()
			defer diagMu.Unlock()
			diag = append(diag, fmt.Sprintf(format, args...))
		})

		client, err := dial(opts)
		if err != nil {
			diagMu.Lock()
			detail := strings.Join(diag, "\n  · ")
			diagMu.Unlock()
			fyne.Do(func() {
				c.connectBtn.Enable()
				c.setStatus("")
				c.showConnectError(err, detail)
			})
			return
		}

		sf, err := sftp.NewClient(client)
		if err != nil {
			client.Close()
			fyne.Do(func() {
				c.connectBtn.Enable()
				c.setStatus("")
				dialog.ShowError(fmt.Errorf("opening SFTP subsystem: %w", err), c.win)
			})
			return
		}

		fyne.Do(func() {
			c.connectBtn.Enable()
			c.setStatus("")
			c.win.Hide()
			newSession(c.app, name, client, sf, func() { c.win.Show() })
		})
	}()
}

// sshOptions wires sshx's blocking callbacks to dialogs on the UI thread. Each
// callback is invoked from the connecting goroutine and waits for an answer.
func (c *connectWindow) sshOptions(initialPassword string, logf func(string, ...any)) sshx.Options {
	var mu sync.Mutex
	cached := initialPassword

	return sshx.Options{
		Passphrase: func(keyfile string) ([]byte, error) {
			reply := make(chan []byte, 1)
			fyne.Do(func() {
				askSecret(c.win, "Key passphrase", "Enter the passphrase for "+keyfile, reply)
			})
			return <-reply, nil
		},
		Password: func(user, host string) ([]byte, error) {
			mu.Lock()
			defer mu.Unlock()
			// A password typed on the quick-connect form is reused for the
			// keyboard-interactive round rather than prompting twice.
			if cached != "" {
				return []byte(cached), nil
			}
			reply := make(chan []byte, 1)
			target := host
			if user != "" {
				target = user + "@" + host
			}
			fyne.Do(func() {
				askSecret(c.win, "Password", "Password for "+target, reply)
			})
			b := <-reply
			cached = string(b)
			return b, nil
		},
		AcceptHostKey: func(host string, key ssh.PublicKey) (bool, error) {
			reply := make(chan bool, 1)
			fyne.Do(func() { askHostKey(c.win, host, key, reply) })
			return <-reply, nil
		},
		Logf: logf,
	}
}

// showConnectError presents the failure with the auth diagnostics sshx
// collected, which is usually what actually explains it.
func (c *connectWindow) showConnectError(err error, detail string) {
	msg := err.Error()
	if detail != "" {
		msg += "\n\nAuth diagnostics:\n  · " + detail
	}
	label := widget.NewLabel(msg)
	label.Wrapping = fyne.TextWrapWord
	d := dialog.NewCustom("Connection failed", "Close", container.NewVScroll(label), c.win)
	d.Resize(fyne.NewSize(560, 320))
	d.Show()
}

func (c *connectWindow) setStatus(s string) { c.status.SetText(s) }

func (c *connectWindow) showAndRun() {
	c.win.ShowAndRun()
}