package tui

import (
	"errors"
	"fmt"

	"git.tordarus.net/Tordarus/buf2d"
	"github.com/gdamore/tcell"
)

type Screen struct {
	scr tcell.Screen
	buf *ViewBuffer

	stopCh   chan error
	redrawCh chan struct{}

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

	// KeyPressed is called every time a key or key-combination is pressed.
	KeyPressed func(event *KeyEvent) (consumed bool)

	// MouseClicked is called every time a mouse button was pressed.
	MouseClicked func(event *MouseEvent) (consumed bool)
}

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),
	}

	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()

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

func (s *Screen) onMouseClicked(event *MouseEvent) {
	if s.MouseClicked == nil || !s.MouseClicked(event) {
		s.Root.OnMouseClicked(event)
	}
	if event.Button != MouseButtonNone {
		s.Redraw()
	}
}

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

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

func (s *Screen) eventloop() {
	defer s.stopOnPanic()

	for evt := s.scr.PollEvent(); evt != nil; evt = s.scr.PollEvent() {
		switch event := evt.(type) {
		case *tcell.EventResize:
			go s.Redraw()
		case *tcell.EventKey:
			go s.onKeyPressed(event)
		case *tcell.EventMouse:
			go s.onMouseClicked(convertMouseEvent(event))
		default:
			s.StopWithError(errors.New(fmt.Sprintf("%#v", event)))
		}
	}
	s.StopWithError(errors.New("unknown error occured"))
}

func (s *Screen) drawloop() {
	defer s.stopOnPanic()

	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)
		}

		rw, rh := s.Root.Layout()
		s.Root.Draw(truncateBuffer(s.buf, rw, rh))
		drawBuffer(s.scr, s.buf)
	}
}

func (s *Screen) stopOnPanic() {
	if err := recover(); err != nil {
		s.StopWithError(fmt.Errorf("%v", err))
	}
}