package ui

import (
	"errors"
	"fmt"

	"git.kirsle.net/go/render"
)

// Frame is a widget that contains other widgets.
type Frame struct {
	Name string
	BaseWidget

	// Widget placement settings.
	packs   map[Side][]*packedWidget // Packed widgets
	placed  []*placedWidget          // Placed widgets
	widgets []Widget
}

// NewFrame creates a new Frame.
func NewFrame(name string) *Frame {
	w := &Frame{
		Name:    name,
		packs:   map[Side][]*packedWidget{},
		widgets: []Widget{},
	}
	w.SetBackground(render.RGBA(1, 0, 0, 0)) // invisible default BG
	w.IDFunc(func() string {
		return fmt.Sprintf("Frame<%s>",
			name,
		)
	})
	return w
}

// Setup ensures all the Frame's data is initialized and not null.
func (w *Frame) Setup() {
	if w.packs == nil {
		w.packs = map[Side][]*packedWidget{}
	}
	if w.widgets == nil {
		w.widgets = []Widget{}
	}
}

// Add a child widget to the frame. When the frame Presents itself, it also
// presents child widgets. This method is safe to call multiple times: it ensures
// the widget is not already a child of the Frame before adding it.
func (w *Frame) Add(child Widget) error {
	if child == w {
		return errors.New("can't add self to frame")
	}

	// Ensure child is new to the frame.
	for _, widget := range w.widgets {
		if widget == child {
			return errors.New("widget already added to frame")
		}
	}
	w.widgets = append(w.widgets, child)
	return nil
}

// Children returns all of the child widgets.
func (w *Frame) Children() []Widget {
	return w.widgets
}

// Compute the size of the Frame.
func (w *Frame) Compute(e render.Engine) {
	w.computePacked(e)
	w.computePlaced(e)

	// Call the BaseWidget Compute in case we have subscribers.
	w.BaseWidget.Compute(e)
}

// Present the Frame.
func (w *Frame) Present(e render.Engine, P render.Point) {
	if w.Hidden() {
		return
	}

	var (
		S = w.Size()
	)

	// Draw the widget's border and everything.
	w.DrawBox(e, P)

	// Draw the background color.
	e.DrawBox(w.Background(), render.Rect{
		X: P.X + w.BoxThickness(1),
		Y: P.Y + w.BoxThickness(1),
		W: S.W - w.BoxThickness(2),
		H: S.H - w.BoxThickness(2),
	})

	// Draw the widgets.
	for _, child := range w.widgets {
		if child.Hidden() {
			continue
		}

		p := child.Point()
		moveTo := render.NewPoint(
			P.X+p.X+w.BoxThickness(1),
			P.Y+p.Y+w.BoxThickness(1),
		)
		child.Present(e, moveTo)
	}

	// Call the BaseWidget Present in case we have subscribers.
	w.BaseWidget.Present(e, P)
}