package ui

import (
	"fmt"

	"codeflow.dananglin.me.uk/apollo/pelican/internal/board"
	"github.com/gdamore/tcell/v2"
	"github.com/rivo/tview"
)

type (
	boardMovement int
	boardMode     int
)

const (
	next boardMovement = iota
	previous
)

const (
	normal boardMode = iota
	selection
)

const (
	mainPage            string = "main"
	quitPage            string = "quit"
	cardFormPage        string = "card form"
	deleteCardModalPage string = "delete card modal"
	viewPage            string = "view"
)

type UI struct {
	*tview.Application

	columns         []*column
	flex            *tview.Flex
	pages           *tview.Pages
	focusedColumn   int
	board           board.Board
	mode            boardMode
	quitModal       *tview.Modal
	cardForm        *cardForm
	deleteCardModal *tview.Modal
	statusSelection statusSelection
	view            *cardView
}

// NewUI returns a new UI value.
func NewUI(path string) (UI, error) {
	kanban, err := board.Open(path)
	if err != nil {
		return UI{}, fmt.Errorf("unable to open the project's board; %w", err)
	}

	userInterface := UI{
		Application:     tview.NewApplication(),
		pages:           tview.NewPages(),
		flex:            tview.NewFlex(),
		quitModal:       tview.NewModal(),
		cardForm:        newCardForm(),
		focusedColumn:   0,
		columns:         nil,
		board:           kanban,
		deleteCardModal: tview.NewModal(),
		mode:            normal,
		statusSelection: statusSelection{0, 0, 0},
		view:            newCardView(),
	}

	if err := userInterface.init(); err != nil {
		return UI{}, fmt.Errorf("received an error after running the initialisation; %w", err)
	}

	return userInterface, nil
}

// closeBoard closes the board.
func (u *UI) closeBoard() {
	_ = u.board.Close()
}

// init initialises the UI.
func (u *UI) init() error {
	err := u.initColumns()
	if err != nil {
		return fmt.Errorf("error initialising the status columns; %w", err)
	}

	u.flex.SetInputCapture(u.inputCapture())

	u.pages.AddPage(mainPage, u.flex, true, true)

	u.initQuitModal()
	u.pages.AddPage(quitPage, u.quitModal, false, false)

	u.initCardForm()
	u.pages.AddPage(cardFormPage, u.cardForm, false, false)

	u.initDeleteCardModal()
	u.pages.AddPage(deleteCardModalPage, u.deleteCardModal, false, false)

	u.initView()
	u.pages.AddPage(viewPage, u.view, false, false)

	u.SetRoot(u.pages, true)

	if err := u.refresh(false); err != nil {
		return fmt.Errorf("error refreshing the board; %w", err)
	}

	return nil
}

func (u *UI) inputCapture() func(event *tcell.EventKey) *tcell.EventKey {
	return func(event *tcell.EventKey) *tcell.EventKey {
		key, letter := event.Key(), event.Rune()

		switch {
		case letter == 'h' || key == tcell.KeyLeft:
			u.shiftColumnFocus(previous)
		case letter == 'l' || key == tcell.KeyRight:
			u.shiftColumnFocus(next)
		case letter == 'c':
			if u.mode == normal {
				u.cardForm.mode = create
				u.cardForm.updateInputFields("", "")
				u.cardForm.frame.SetTitle(" Create Card ")
				u.pages.ShowPage(cardFormPage)
				u.SetFocus(u.cardForm)
			}
		case letter == 'm':
			if u.mode == normal {
				u.statusSelection.cardID = u.focusedCardID()
				u.statusSelection.currentStatusID = u.focusedStatusID()
				u.mode = selection
			}
		case letter == 'e':
			if u.mode == normal {
				u.cardForm.mode = edit
				card, _ := u.getFocusedCard()
				u.cardForm.updateInputFields(card.Title, card.Description)
				u.cardForm.frame.SetTitle(" Edit Card ")
				u.pages.ShowPage(cardFormPage)
				u.SetFocus(u.cardForm)
			}
		case key == tcell.KeyCtrlD:
			if u.mode == normal {
				u.pages.ShowPage(deleteCardModalPage)
				u.SetFocus(u.deleteCardModal)
			}
		case key == tcell.KeyCtrlQ:
			if u.mode == normal {
				u.pages.ShowPage(quitPage)
				u.SetFocus(u.quitModal)
			}
		case key == tcell.KeyESC:
			if u.mode != normal {
				u.mode = normal
			}
		case key == tcell.KeyEnter:
			switch u.mode {
			case normal:
				card, _ := u.getFocusedCard()
				status := u.focusedStatusName()
				u.view.print(card.ID, card.Title, status, card.Created, card.Description)
				u.pages.ShowPage(viewPage)
				u.SetFocus(u.view)
			case selection:
				u.statusSelection.nextStatusID = u.focusedStatusID()
				if u.statusSelection.currentStatusID != u.statusSelection.nextStatusID {
					u.statusSelection.moveCard(u.board)
				}

				u.statusSelection = statusSelection{0, 0, 0}
				u.mode = normal
				_ = u.refresh(false)
			}
		}

		return event
	}
}

// initCardForm initialises the card form.
func (u *UI) initCardForm() {
	doneFunc := func(title, description string, success bool, mode cardFormMode) {
		if success {
			switch mode {
			case create:
				_ = u.newCard(title, description)
			case edit:
				_ = u.editFocusedCard(title, description)
			}
		}

		u.pages.HidePage(cardFormPage)
		u.setColumnFocus()
	}

	u.cardForm.setDoneFunc(doneFunc)
}

// initDeleteCardModal initialises the modal for deleting cards.
func (u *UI) initDeleteCardModal() {
	doneFunc := func(_ int, buttonLabel string) {
		if buttonLabel == "Confirm" {
			u.deleteFocusedCard()
			_ = u.refresh(true)
		}

		u.pages.HidePage(deleteCardModalPage)
		u.setColumnFocus()
	}

	u.deleteCardModal.SetText("Do you want to delete this card?").
		AddButtons([]string{"Confirm", "Cancel"}).
		SetDoneFunc(doneFunc)
}

// initQuitModal initialises the quit modal.
func (u *UI) initQuitModal() {
	doneFunc := func(_ int, buttonLabel string) {
		switch buttonLabel {
		case "Quit":
			u.shutdown()
		default:
			u.pages.HidePage(quitPage)
			u.setColumnFocus()
		}
	}

	u.quitModal.SetText("Do you want to quit the application?").
		AddButtons([]string{"Quit", "Cancel"}).
		SetDoneFunc(doneFunc)
}

// initView initialises the view window for displaying the card.
func (u *UI) initView() {
	doneFunc := func(key tcell.Key) {
		if key == tcell.KeyEsc {
			u.pages.HidePage(viewPage)
			u.view.Clear()
			u.setColumnFocus()
		}
	}

	u.view.setDoneFunc(doneFunc)
}

// newCard creates and saves a new card to the database.
func (u *UI) newCard(title, description string) error {
	args := board.CardArgs{
		NewTitle:       title,
		NewDescription: description,
	}

	if _, err := u.board.CreateCard(args); err != nil {
		return fmt.Errorf("unable to create card, %w", err)
	}

	_ = u.refresh(false)

	return nil
}

// editFocusedCard saves and edited card to the database.
func (u *UI) editFocusedCard(title, description string) error {
	cardID := u.focusedCardID()

	args := board.UpdateCardArgs{
		CardID: cardID,
		CardArgs: board.CardArgs{
			NewTitle:       title,
			NewDescription: description,
		},
	}

	if err := u.board.UpdateCard(args); err != nil {
		return fmt.Errorf("unable to edit card with ID: %d; %w", cardID, err)
	}

	_ = u.refresh(true)

	return nil
}

// getFocusedCard retrieves the details of the focused card.
func (u *UI) getFocusedCard() (board.Card, error) {
	cardID := u.focusedCardID()

	card, err := u.board.Card(cardID)
	if err != nil {
		return board.Card{}, fmt.Errorf("unable to retrieve the card with card ID %d, %w", cardID, err)
	}

	return card, nil
}

// deleteFocusedCard deletes the focused card from the board.
func (u *UI) deleteFocusedCard() {
	args := board.DeleteCardArgs{
		CardID:   u.focusedCardID(),
		StatusID: u.focusedStatusID(),
	}

	_ = u.board.DeleteCard(args)
}

// initColumns initialises the columns of the Kanban board.
func (u *UI) initColumns() error {
	u.flex.Clear()

	statusList, err := u.board.StatusList()
	if err != nil {
		return fmt.Errorf("unable to retrieve the list of statuses; %w", err)
	}

	columns := make([]*column, len(statusList))

	for i := range statusList {
		column := newColumn(statusList[i].ID, statusList[i].Name, u.boardMode)
		u.flex.AddItem(column, 50, 1, true)
		columns[i] = column
	}

	u.columns = columns

	return nil
}

func (u *UI) updateAllColumns() error {
	for i := range u.columns {
		if err := u.updateColumn(i); err != nil {
			return err
		}
	}

	return nil
}

func (u *UI) updateColumn(index int) error {
	if err := u.columns[index].update(u.board); err != nil {
		return fmt.Errorf("unable to update column; %w", err)
	}

	return nil
}

func (u *UI) shiftColumnFocus(movement boardMovement) {
	switch movement {
	case next:
		if u.focusedColumn == len(u.columns)-1 {
			u.focusedColumn = 0
		} else {
			u.focusedColumn++
		}
	case previous:
		if u.focusedColumn == 0 {
			u.focusedColumn = len(u.columns) - 1
		} else {
			u.focusedColumn--
		}
	}

	u.setColumnFocus()
}

func (u *UI) setColumnFocus() {
	u.SetFocus(u.columns[u.focusedColumn])
}

// refresh refreshes the UI.
func (u *UI) refresh(updateFocusedColumnOnly bool) error {
	if updateFocusedColumnOnly {
		if err := u.updateColumn(u.focusedColumn); err != nil {
			return err
		}
	} else {
		if err := u.updateAllColumns(); err != nil {
			return err
		}
	}

	u.setColumnFocus()

	return nil
}

// shutdown shuts down the application.
func (u *UI) shutdown() {
	u.closeBoard()
	u.Stop()
}

// boardMode returns the current board mode.
func (u *UI) boardMode() boardMode {
	return u.mode
}

// focusedCardID returns the ID of the card in focus.
func (u *UI) focusedCardID() int {
	focusedCard := u.columns[u.focusedColumn].focusedCard
	id := u.columns[u.focusedColumn].cards[focusedCard].id

	return id
}

// focusedStatusID returns the ID of the status (column) in focus.
func (u *UI) focusedStatusID() int {
	return u.columns[u.focusedColumn].statusID
}

// focusedStatusName returns the name of the status (column) in focus.
func (u *UI) focusedStatusName() string {
	return u.columns[u.focusedColumn].statusName
}