package ui

import (
	"fmt"
	"sync"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/dialog"
	"fyne.io/fyne/v2/layout"
	"fyne.io/fyne/v2/widget"
	"golang.org/x/crypto/ssh"

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

// The prompts in this file are all shaped the same way, because they are all
// answers a background goroutine is blocked waiting for: the goroutine makes a
// buffered channel, asks for the prompt to be shown on the UI thread, and reads
// its answer. Every dismissal path — button, escape, window close — must send
// exactly once, or the transfer goroutine hangs forever holding the connection.
// sync.Once is what guarantees the "exactly".

func confirmDialog(title, msg string, win fyne.Window, cb func(bool)) {
	dialog.ShowConfirm(title, msg, cb, win)
}

func newFormDialog(title, confirm string, items []*widget.FormItem, win fyne.Window, cb func(bool)) dialog.Dialog {
	d := dialog.NewForm(title, confirm, "Cancel", items, cb, win)
	d.Resize(fyne.NewSize(420, 0))
	return d
}

// conflictAnswer is the user's decision about one pre-existing destination file.
type conflictAnswer struct {
	choice xfer.Conflict
	all    bool // apply this decision to every remaining conflict
}

// askConflict shows the overwrite prompt. It must be called on the UI thread.
func askConflict(win fyne.Window, name string, reply chan<- conflictAnswer) {
	var once sync.Once
	send := func(a conflictAnswer) { once.Do(func() { reply <- a }) }

	all := widget.NewCheck("Apply to all remaining conflicts", nil)
	msg := widget.NewLabel(fmt.Sprintf("%s already exists at the destination.", name))
	msg.Wrapping = fyne.TextWrapWord

	var d *dialog.CustomDialog
	button := func(label string, c xfer.Conflict) *widget.Button {
		return widget.NewButton(label, func() {
			send(conflictAnswer{choice: c, all: all.Checked})
			d.Hide()
		})
	}
	overwrite := button("Overwrite", xfer.Overwrite)
	overwrite.Importance = widget.HighImportance

	content := container.NewVBox(
		msg,
		all,
		container.NewHBox(layout.NewSpacer(),
			button("Skip", xfer.Skip),
			button("Keep both", xfer.Rename),
			overwrite,
		),
	)
	d = dialog.NewCustomWithoutButtons("File exists", content, win)
	// Dismissing without choosing is treated as "skip this file": the safe
	// reading of "I didn't answer" is "don't destroy anything".
	d.SetOnClosed(func() { send(conflictAnswer{choice: xfer.Skip}) })
	d.Resize(fyne.NewSize(460, 0))
	d.Show()
}

// askSecret prompts for a password or key passphrase. An empty result means the
// user declined, which callers pass on to sshx as "skip this method".
func askSecret(win fyne.Window, title, prompt string, reply chan<- []byte) {
	var once sync.Once
	send := func(b []byte) { once.Do(func() { reply <- b }) }

	entry := widget.NewPasswordEntry()
	label := widget.NewLabel(prompt)
	label.Wrapping = fyne.TextWrapWord

	var d *dialog.CustomDialog
	submit := func() {
		send([]byte(entry.Text))
		d.Hide()
	}
	entry.OnSubmitted = func(string) { submit() }

	ok := widget.NewButton("OK", submit)
	ok.Importance = widget.HighImportance
	cancel := widget.NewButton("Cancel", func() {
		send(nil)
		d.Hide()
	})

	content := container.NewVBox(
		label,
		entry,
		container.NewHBox(layout.NewSpacer(), cancel, ok),
	)
	d = dialog.NewCustomWithoutButtons(title, content, win)
	d.SetOnClosed(func() { send(nil) })
	d.Resize(fyne.NewSize(420, 0))
	d.Show()
	win.Canvas().Focus(entry)
}

// askHostKey shows the unknown-host prompt, the GUI equivalent of ssh's
// "authenticity of host ... can't be established". The fingerprint is shown in
// the same SHA256 form ssh prints, so it can be compared by eye.
func askHostKey(win fyne.Window, host string, key ssh.PublicKey, reply chan<- bool) {
	var once sync.Once
	send := func(b bool) { once.Do(func() { reply <- b }) }

	msg := widget.NewLabel(fmt.Sprintf(
		"The authenticity of host %s can't be established.\n\n%s key fingerprint:", host, key.Type()))
	msg.Wrapping = fyne.TextWrapWord
	fp := widget.NewLabelWithStyle(sshx.FingerprintSHA256(key), fyne.TextAlignCenter, fyne.TextStyle{Monospace: true})
	warn := widget.NewLabel("Only continue if you recognise this fingerprint. It will be added to your known_hosts file.")
	warn.Wrapping = fyne.TextWrapWord

	var d *dialog.CustomDialog
	accept := widget.NewButton("Connect and record key", func() {
		send(true)
		d.Hide()
	})
	accept.Importance = widget.HighImportance
	reject := widget.NewButton("Cancel", func() {
		send(false)
		d.Hide()
	})

	content := container.NewVBox(msg, fp, warn,
		container.NewHBox(layout.NewSpacer(), reject, accept))
	d = dialog.NewCustomWithoutButtons("Unknown host key", content, win)
	d.SetOnClosed(func() { send(false) })
	d.Resize(fyne.NewSize(520, 0))
	d.Show()
}