package main

import (
	"bufio"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"regexp"
	"strings"
	"syscall"
	"time"

	qt "github.com/mappu/miqt/qt6"
)

// GUIConfig carries all application configurations.
type GUIConfig struct {
	DestinationFolder string
	PlaylistEnabled   bool
}

// GetDestinationFolder attempts to retrieve (if not yet) and returns the
// configured destination folder.
func (c *GUIConfig) GetDestinationFolder() string {
	fallback := DefaultDownloadsFolder()
	val := settings.Value(*qt.NewQAnyStringView3("destinationFolder"), qt.NewQVariant11(fallback)).ToString()
	c.DestinationFolder = val
	return val
}

// GetPlaylistEnabled attempts to retrieve (if not yet) and returns the
// configured value of whether playlist download is enabled.
func (c *GUIConfig) GetPlaylistEnabled() bool {
	fallback := true
	val := settings.Value(*qt.NewQAnyStringView3("playlistEnabled"), qt.NewQVariant8(fallback)).ToBool()
	c.PlaylistEnabled = val
	return val
}

// SetDestinationFolder sets and persists the configured destination folder.
func (c *GUIConfig) SetDestinationFolder(val string) {
	c.DestinationFolder = val
	go func() { settings.SetValue(*qt.NewQAnyStringView3("destinationFolder"), qt.NewQVariant11(val)) }()
}

// SetPlaylistEnabled sets and persists the configured value of whether playlist
// download is enabled.
func (c *GUIConfig) SetPlaylistEnabled(val bool) {
	c.PlaylistEnabled = val
	go func() { settings.SetValue(*qt.NewQAnyStringView3("playlistEnabled"), qt.NewQVariant8(val)) }()
}

// LoadGUIConfig loads config values from persisted settings if possible, or
// loads defaults otherwise.
func LoadGUIConfig() *GUIConfig {
	c := &GUIConfig{}
	c.GetDestinationFolder()
	c.GetPlaylistEnabled()
	return c
}

var settings *qt.QSettings
var guiConfig *GUIConfig

func printError(url string, err error) {
	fmt.Printf(
		"Downloading %s error:\n%s\n", url, err,
	)
}

//

type outputBuffer struct {
	textEdit               *qt.QPlainTextEdit
	reader                 *bufio.Reader
	scanner                *bufio.Scanner
	carriageReturnInAction bool
}

func newOutputBuffer(textEdit *qt.QPlainTextEdit) *outputBuffer {
	return &outputBuffer{
		textEdit:               textEdit,
		reader:                 nil,
		scanner:                nil,
		carriageReturnInAction: false,
	}
}

func (b *outputBuffer) attachReader(r io.Reader) {
	b.reader = bufio.NewReaderSize(r, 64*1024)
	b.scanner = bufio.NewScanner(b.reader)
	re := regexp.MustCompile(`^[^\r\n]*(\r\n|\r|\n)`)
	b.scanner.Split(func(data []byte, atEOF bool) (advance int, token []byte, err error) {
		token = re.Find(data)
		if token != nil {
			return len(token), token, nil
		}
		if !atEOF {
			return 0, nil, nil
		}
		return 0, data, bufio.ErrFinalToken
	})
}

// addLine adds a line that might end in LF, CRLF, CR, or none of the above (in
// which case an LF is appended). Aware of CR and scroll position.
func (b *outputBuffer) addLine(line string) {
	scrollBar := b.textEdit.VerticalScrollBar()
	currentScroll := scrollBar.Value()
	userScrolledBack := currentScroll != scrollBar.Maximum()

	cursor := b.textEdit.TextCursor()
	cursor.MovePosition3(qt.QTextCursor__End, qt.QTextCursor__MoveAnchor, 1)
	if b.carriageReturnInAction {
		// Remove last line.
		cursor.Select(qt.QTextCursor__LineUnderCursor)
		cursor.RemoveSelectedText()
	}
	b.carriageReturnInAction = false
	if len(line) > 0 {
		switch lastCh := line[len(line)-1]; lastCh {
		case '\n':
			cursor.InsertText(line)
		case '\r':
			cursor.InsertText(line[:len(line)-1])
			b.carriageReturnInAction = true
		default:
			cursor.InsertText(line + "\n")
		}
	} else {
		cursor.InsertText("\n")
	}

	if userScrolledBack {
		scrollBar.SetValue(currentScroll)
	} else {
		scrollBar.SetValue(scrollBar.Maximum())
	}
}

func (b *outputBuffer) readLineAndUpdate() (fullLine string, err error) {
	if !b.scanner.Scan() {
		err = b.scanner.Err()
		if err != nil {
			return "", err
		}
		err = io.EOF
	}
	fullLine = b.scanner.Text()
	if len(fullLine) > 0 {
		b.addLine(fullLine)
	}
	return
}

func init() {
	flag.Parse()

	initLanguages()

	qt.QCoreApplication_SetOrganizationName(appAuthor)
	qt.QCoreApplication_SetOrganizationDomain(appAuthorDomain)

	settings = qt.NewQSettings5()
	guiConfig = LoadGUIConfig()
}

func initAboutWindow(parent *qt.QWidget) *qt.QDialog {
	w := qt.NewQDialog(parent)
	label := qt.NewQLabel3(about)
	label.SetOpenExternalLinks(true)
	layout := qt.NewQVBoxLayout2()
	layout.AddWidget(label.QWidget)
	w.SetLayout(layout.QLayout)
	return w
}

func main() {
	qt.NewQApplication(os.Args)

	window := qt.NewQMainWindow2()
	window.SetWindowTitle(appName)

	const WindowStateVersion = 0

	window.OnCloseEvent(func(super func(event *qt.QCloseEvent), event *qt.QCloseEvent) {
		settings.SetValue(*qt.NewQAnyStringView3("_geometry"), qt.NewQVariant12(window.SaveGeometry()))
		settings.SetValue(*qt.NewQAnyStringView3("_windowState"), qt.NewQVariant12(window.SaveState1(WindowStateVersion)))

		super(event)
	})

	{
		prevGeometry := settings.Value(*qt.NewQAnyStringView3("_geometry"), qt.NewQVariant()).ToByteArray()
		if len(prevGeometry) > 0 {
			window.RestoreGeometry(prevGeometry)
		}

		prevWindowState := settings.Value(*qt.NewQAnyStringView3("_windowState"), qt.NewQVariant()).ToByteArray()
		if len(prevWindowState) > 0 {
			window.RestoreState2(prevWindowState, WindowStateVersion)
		}
	}

	centralWidget := qt.NewQWidget(window.QWidget)
	window.SetCentralWidget(centralWidget)

	menuBar := window.MenuBar()
	applicationMenu := menuBar.AddMenuWithTitle(tr("Application"))
	aboutWindow := initAboutWindow(window.QWidget)
	aboutAction := applicationMenu.AddActionWithText(tr("About"))
	aboutAction.SetMenuRole(qt.QAction__AboutRole)
	aboutAction.OnTriggered(func() {
		aboutWindow.Show()
		aboutWindow.Raise()
	})

	urlLineEdit := qt.NewQLineEdit(nil)

	folderLineEdit := qt.NewQLineEdit3(guiConfig.DestinationFolder)
	folderLineEdit.SetReadOnly(true)
	folderLineEdit.SetMinimumWidth(250)
	folderButton := qt.NewQPushButton3(tr("Pick another folder"))
	folderDialog := qt.NewQFileDialog6(window.QWidget, tr("Destination folder"), guiConfig.DestinationFolder, "")
	folderDialog.SetFileMode(qt.QFileDialog__Directory)
	folderButton.OnClicked(func() {
		if folderDialog.Exec() != int(qt.QDialog__Accepted) { // FIXME blocking call
			return
		}
		destinationFolder := qt.QDir_ToNativeSeparators(folderDialog.SelectedFiles()[0])
		folderLineEdit.SetText(destinationFolder)
		guiConfig.SetDestinationFolder(destinationFolder)
	})
	folderHBoxLayout := qt.NewQHBoxLayout2()
	folderHBoxLayout.AddWidget3(folderLineEdit.QWidget, 1, 0)
	folderHBoxLayout.AddWidget3(folderButton.QWidget, 0, 0)

	playlistCheckBox := qt.NewQCheckBox(nil)
	playlistCheckBox.SetChecked(guiConfig.PlaylistEnabled)
	playlistCheckBox.OnToggled(func(checked bool) {
		guiConfig.SetPlaylistEnabled(checked)
	})

	inputFormLayout := qt.NewQFormLayout(nil)
	inputFormLayout.SetFieldGrowthPolicy(qt.QFormLayout__AllNonFixedFieldsGrow)
	inputFormLayout.AddRow3(tr("Video URL"), urlLineEdit.QWidget)
	inputFormLayout.AddRow4(tr("Destination folder"), folderHBoxLayout.QLayout)
	inputFormLayout.AddRow3(tr("Download playlists"), playlistCheckBox.QWidget)

	outputTextEdit := qt.NewQPlainTextEdit2()
	outputTextEdit.SetReadOnly(true)
	outputTextEdit.SetMinimumHeight(400)
	outputTextEdit.SetMinimumWidth(1000)
	outputTextEdit.SetLineWrapMode(qt.QPlainTextEdit__NoWrap)
	monospaceFont := qt.NewQFont2("Courier")
	monospaceFont.SetStyleHint(qt.QFont__Monospace)
	outputTextEdit.SetFont(monospaceFont)
	output := newOutputBuffer(outputTextEdit)
	output.addLine(tr("Awaiting user input"))

	downloadButton := qt.NewQPushButton3(tr("Download"))
	downloadButton.OnClicked(func() {
		url := strings.TrimSpace(urlLineEdit.Text())
		if len(url) > 0 {
			output.addLine(time.Now().Format("15:04:05 ") + tr("Download started"))

			savedStdout := os.Stdout
			r, w, _ := os.Pipe()
			output.attachReader(r)
			os.Stdout = w

			go func() {
				for {
					_, err := output.readLineAndUpdate()
					if err != nil {
						if err == io.EOF {
							break
						}
						log.Fatal(err)
					}
					// fmt.Fprint(savedStdout, line)
				}
				output.addLine("")
			}()

			go func() {
				if !download(url, guiConfig.PlaylistEnabled, guiConfig.DestinationFolder) {
					fmt.Println(tr("On network errors, e.g. HTTP 403, please retry a few times."))
				}
				w.Close()
				os.Stdout = savedStdout
			}()
		}
	})

	layout := qt.NewQVBoxLayout2()
	layout.AddLayout2(inputFormLayout.QLayout, 0)
	layout.AddWidget3(downloadButton.QWidget, 0, 0)
	layout.AddWidget3(outputTextEdit.QWidget, 1, 0)
	centralWidget.SetLayout(layout.QLayout)

	window.Show()

	sigs := make(chan os.Signal)
	signal.Notify(sigs, syscall.SIGSEGV, syscall.SIGABRT)
	go func() {
		for {
			sig := <-sigs
			log.Print(sig)
		}
	}()

	qt.QApplication_Exec()
}