ui/screen/screen.go

package screen

import (
	"embed"
	"fmt"
	"io"
	"io/fs"
	"strings"
	"time"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/data/binding"
	"fyne.io/fyne/v2/theme"
	"fyne.io/fyne/v2/widget"
	"github.com/nicksnyder/go-i18n/v2/i18n"
	"gopkg.in/yaml.v2"
)

type ListItemTemplateFn func() fyne.CanvasObject
type ListDataItemRendererFn func(binding.DataItem, fyne.CanvasObject)
type ListItemRendererFn func(int, fyne.CanvasObject)
type ListLengthFn func() int
type ListItemHandlerFn func(widget.ListItemID)
type ClickHandlerFn func()
type CheckHandlerFn func(bool)
type DateSelectedHandlerFn func(time.Time)
type ValidationChangedHandlerFn func(error)

type UIElement struct {
	Object    fyne.CanvasObject
	Decorator fyne.CanvasObject
}

type ScreenHandler interface {
	RegisterElement(string, fyne.CanvasObject, fyne.CanvasObject)

	GetLocalizer() *i18n.Localizer
	GetIcon(string) fyne.Resource
	GetBinding(string) binding.DataItem
	GetValidator(string) fyne.StringValidator
	GetListItemTemplate(string) ListItemTemplateFn
	GetListDataItemRenderer(string) ListDataItemRendererFn
	GetListItemRenderer(string) ListItemRendererFn
	GetListLength(string) ListLengthFn

	GetOnListItemSelectedHandler(string) ListItemHandlerFn
	GetOnListItemUnselectedHandler(string) ListItemHandlerFn
	GetOnClickedHandler(string) ClickHandlerFn
	GetOnCheckChangedHandler(string) CheckHandlerFn
	GetOnDateSelectedHandler(string) DateSelectedHandlerFn
	GetOnValidationChangedHandler(string) ValidationChangedHandlerFn
}

type Screen struct {
	rootElement   *Element
	screenHandler ScreenHandler
}

func New(
	filesystem embed.FS,
	name string,
	screenHandler ScreenHandler,
) (scr *Screen, err error) {
	var bytes []byte
	var fh fs.File

	if fh, err = filesystem.Open(name); err != nil {
		err = fmt.Errorf("no screen definition found: %w", err)
		return
	}

	if bytes, err = io.ReadAll(fh); err != nil {
		err = fmt.Errorf("unable to read screen definition: %w", err)
		return
	}

	root := &Element{}
	if err = yaml.Unmarshal(bytes, root); err != nil {
		err = fmt.Errorf("failure parsing screen definition: %w", err)
		return
	}

	scr = &Screen{
		rootElement:   root,
		screenHandler: screenHandler,
	}
	return
}

func NewTemplate(
	filesystem embed.FS,
	name string,
	localizer *i18n.Localizer,
) (
	scr *Screen,
	handler *TemplateScreenHandler,
	err error,
) {
	handler = NewTemplateScreenHandler(localizer)
	scr, err = New(filesystem, name, handler)
	return
}

func (s *Screen) Initialize() (obj fyne.CanvasObject, err error) {
	if obj, err = s.rootElement.BuildUI(s.screenHandler); err != nil {
		err = fmt.Errorf("failed to build screen: %w", err)
		return
	}
	return
}

type TemplateScreenHandler struct {
	localizer   *i18n.Localizer
	elementsMap map[string]*UIElement
}

func NewTemplateScreenHandler(
	localizer *i18n.Localizer,
) *TemplateScreenHandler {
	return &TemplateScreenHandler{
		localizer:   localizer,
		elementsMap: make(map[string]*UIElement),
	}
}

func (d *TemplateScreenHandler) RegisterElement(
	name string,
	element fyne.CanvasObject,
	decorator fyne.CanvasObject,
) {
	d.elementsMap[name] = &UIElement{element, decorator}
}

func (d *TemplateScreenHandler) GetElement(name string) *UIElement {
	elem, ok := d.elementsMap[name]
	if !ok {
		return nil
	}
	return elem
}

func (d *TemplateScreenHandler) GetLocalizer() *i18n.Localizer {
	return d.localizer
}

func (d *TemplateScreenHandler) GetIcon(iconName string) fyne.Resource {
	if strings.HasPrefix(iconName, "theme.") {
		iconName := strings.SplitN(iconName, ".", 2)[1]
		return theme.DefaultTheme().Icon(fyne.ThemeIconName(iconName))
	}
	return nil
}

func (*TemplateScreenHandler) GetBinding(string) binding.DataItem {
	return nil
}

func (*TemplateScreenHandler) GetValidator(string) fyne.StringValidator {
	return nil
}

func (*TemplateScreenHandler) GetListItemTemplate(string) ListItemTemplateFn {
	return func() fyne.CanvasObject { return nil }
}

func (*TemplateScreenHandler) GetListDataItemRenderer(string) ListDataItemRendererFn {
	return func(binding.DataItem, fyne.CanvasObject) {}
}

func (*TemplateScreenHandler) GetListItemRenderer(string) ListItemRendererFn {
	return func(int, fyne.CanvasObject) {}
}

func (*TemplateScreenHandler) GetListLength(string) ListLengthFn {
	return func() int { return 0 }
}

func (*TemplateScreenHandler) GetOnListItemSelectedHandler(string) ListItemHandlerFn {
	return func(widget.ListItemID) {}
}

func (*TemplateScreenHandler) GetOnListItemUnselectedHandler(string) ListItemHandlerFn {
	return func(widget.ListItemID) {}
}

func (*TemplateScreenHandler) GetOnClickedHandler(string) ClickHandlerFn {
	return func() {}
}

func (*TemplateScreenHandler) GetOnCheckChangedHandler(string) CheckHandlerFn {
	return func(bool) {}
}

func (*TemplateScreenHandler) GetOnDateSelectedHandler(string) DateSelectedHandlerFn {
	return func(time.Time) {}
}

func (*TemplateScreenHandler) GetOnValidationChangedHandler(string) ValidationChangedHandlerFn {
	return func(error) {}
}