package tui

import (
	"fmt"

	"git.milar.in/milarin/adverr"
	"git.milar.in/milarin/buf2d"
	"git.milar.in/milarin/ds"
	"github.com/gdamore/tcell"
)

type Screen struct {
	EventTmpl

	scr tcell.Screen
	buf *ViewBuffer

	stopCh   chan error
	redrawCh chan struct{}
	started  bool

	modals ds.Stack[View]

	// Root is the root view which is currently shown on screen
	Root View
}

func NewScreen(root View) (*Screen, error) {
	scr, err := tcell.NewScreen()
	if err != nil {
		return nil, err
	}

	s := &Screen{
		Root:     root,
		scr:      scr,
		stopCh:   make(chan error, 1),
		redrawCh: make(chan struct{}, 1),
		modals:   ds.NewArrayStack[View](),
	}

	s.KeyPressed = CloseOnCtrlC(s)

	go s.eventloop()
	go s.drawloop()

	return s, nil
}

func (s *Screen) Start() error {
	err := s.scr.Init()
	if err != nil {
		return err
	}

	defer s.scr.Fini()
	defer close(s.redrawCh)

	s.scr.EnableMouse()
	s.started = true
	return <-s.stopCh
}

func (s *Screen) Stop() {
	s.StopWithError(nil)
}

func (s *Screen) StopWithError(err error) {
	s.stopCh <- err
}

func (s *Screen) onKeyPressed(event *KeyEvent) {
	if !s.modals.Empty() {
		s.modals.Peek().OnKeyPressed(event)
		return
	}

	if s.KeyPressed == nil || !s.KeyPressed(event) {
		s.Root.OnKeyPressed(event)
	}
	s.Redraw()
}

func (s *Screen) onMouseEvent(event *MouseEvent) {
	if event.Button != MouseButtonNone {
		defer s.Redraw()
	}

	if !s.modals.Empty() {
		s.modals.Peek().OnMouseEvent(event)
		return
	}

	if s.MouseEvent != nil && s.MouseEvent(event) {
		return
	}

	s.Root.OnMouseEvent(event)
}

func convertMouseEvent(original *tcell.EventMouse) *MouseEvent {
	x, y := original.Position()
	return &MouseEvent{
		Position:  P(x, y),
		Button:    convertMouseButton(original.Buttons()),
		Modifiers: original.Modifiers(),
	}
}

func (s *Screen) Redraw() {
	if s.started {
		s.redrawCh <- struct{}{}
	}
}

func (s *Screen) eventloop() {
	defer s.handlePanic("panicked while handling event")

	for evt := s.scr.PollEvent(); evt != nil; evt = s.scr.PollEvent() {
		switch event := evt.(type) {
		case *tcell.EventResize:
			s.Redraw()
		case *tcell.EventKey:
			s.startPanicSafeThread("panicked while handling key event", func() { s.onKeyPressed(event) })
		case *tcell.EventMouse:
			s.startPanicSafeThread("panicked while handling mouse event", func() { s.onMouseEvent(convertMouseEvent(event)) })
		default:
			s.StopWithError(fmt.Errorf("%#v", event))
		}
	}
}

func (s *Screen) startPanicSafeThread(errorMessage string, f func()) {
	go func() {
		defer s.handlePanic(errorMessage)
		f()
	}()
}

func (s *Screen) drawloop() {
	defer s.handlePanic("panicked while redrawing")

	for range s.redrawCh {
		w, h := s.scr.Size()

		if s.buf == nil || s.buf.Width() != w || s.buf.Height() != h {
			s.buf = buf2d.NewBuffer(w, h, DefaultRune)
		} else {
			s.buf.Fill(DefaultRune)
		}

		// draw root view
		rw, rh := s.Root.Layout()
		s.Root.Draw(truncateBuffer(s.buf, rw, rh))

		// draw modals
		for i := 0; i < s.modals.Size(); i++ {
			v := s.modals.PeekAt(i)
			mw, mh := v.Layout()
			v.Draw(s.buf.Sub(0, 0, iff(mw >= 0, mw, s.buf.Width()), iff(mh >= 0, mh, s.buf.Height())))
		}

		// draw buffer onto screen
		drawBuffer(s.scr, s.buf)
	}
}

func (s *Screen) handlePanic(msg string) {
	if err := recover(); err != nil {
		if e, ok := err.(error); ok {
			s.StopWithError(adverr.Wrap(msg, e))
		} else {
			s.StopWithError(adverr.Wrap(msg, fmt.Errorf("%v", err)))
		}
	}
}

func (s *Screen) OpenModal(v View) {
	s.modals.Push(v)
	s.Redraw()
}

func (s *Screen) CloseModal() {
	s.modals.Pop()
	s.Redraw()
}