package ui

import (
	"embed"
	"errors"
	"fmt"
	"io/fs"
	"log"
	"strings"

	"gitea.hevanto-it.com/hevanto/ui/screen"
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/data/binding"
	"fyne.io/fyne/v2/theme"
	"github.com/nicksnyder/go-i18n/v2/i18n"
)

type screenType int

const (
	stScreen screenType = iota
	stDialog
)

type ScreenDefinition interface {
	fyne.Widget
	Initialize() (fyne.CanvasObject, error)
	RegisterResizeCallback(func(fyne.Size))
	RegisterMoveCallback(func(fyne.Position))
	AsContainer() *fyne.Container
}

// ScreenHandler represents the handler for a screen.
//
// It provides:
//   - The screen definition
//   - The localizer
//   - The screen controller
//   - Exported elements
//   - List item templates and renderers
//   - User interaction handlers
type ScreenHandler struct {
	screenDefinition ScreenDefinition
	localizer        *i18n.Localizer
	viewModel        BaseViewModel
	assetLoader      func(string) (fs.File, error)

	// Map of screen elements that got an id assigned
	exportedElements map[string]*screen.UIElement

	listItemTemplates     map[string]screen.ListItemTemplateFn
	listItemRenderers     map[string]screen.ListItemRendererFn
	listDataItemRenderers map[string]screen.ListDataItemRendererFn
	listLengths           map[string]screen.ListLengthFn

	onListItemSelectedHandlers   map[string]screen.ListItemHandlerFn
	onListItemUnselectedHandlers map[string]screen.ListItemHandlerFn
	onClickedHandlers            map[string]screen.ClickHandlerFn
	onCheckChangedHandlers       map[string]screen.CheckHandlerFn
	onDateSelectedHandlers       map[string]screen.DateSelectedHandlerFn
	onOptionSelectedHandlers     map[string]screen.OptionSelectedHandlerFn
	onValidationChangedHandlers  map[string]screen.ValidationChangedHandlerFn
}

// NewScreenHandler initializes a new ScreenHandler with the provided filesystem, screen name, ScreenController, and localizer.
//
// Arguments:
//   - filesystem: the embedded filesystem to access screen resources.
//   - screenName: the name of the screen to load.
//   - ctrl: the ScreenController for the screen.
//   - localizer: the i18n.Localizer for localization.
//
// Returns:
//   - h: the initialized ScreenHandler.
//   - err: an error if loading the screen fails.
func NewScreenHandler(
	filesystem embed.FS,
	screenName string,
	viewModel BaseViewModel,
	localizer *i18n.Localizer,
	assetLoader func(string) (fs.File, error),
) (h *ScreenHandler, err error) {
	return newScreenHandler(
		stScreen, filesystem, screenName, viewModel, localizer, assetLoader)
}

func NewDialogScreenHandler(
	filesystem embed.FS,
	screenName string,
	viewModel BaseViewModel,
	localizer *i18n.Localizer,
	assetLoader func(string) (fs.File, error),
) (h *ScreenHandler, err error) {
	return newScreenHandler(
		stDialog, filesystem, screenName, viewModel, localizer, assetLoader)
}

func newScreenHandler(
	screenType screenType,
	fileSystem embed.FS,
	screenName string,
	viewModel BaseViewModel,
	localizer *i18n.Localizer,
	assetLoader func(string) (fs.File, error),
) (h *ScreenHandler, err error) {
	h = new(ScreenHandler)

	h.viewModel = viewModel
	h.localizer = localizer

	switch screenType {
	case stScreen:
		h.screenDefinition, err = screen.New(fileSystem, screenName, h)
	case stDialog:
		h.screenDefinition, err = screen.NewDialogScreen(fileSystem, screenName, h)
	default:
		err = errors.New("Unsupported screen type")
	}

	if err != nil {
		err = fmt.Errorf("failure loading screen: %w", err)
		return
	}
	h.assetLoader = assetLoader

	h.exportedElements = make(map[string]*screen.UIElement)
	h.listItemTemplates = make(map[string]screen.ListItemTemplateFn)
	h.listItemRenderers = make(map[string]screen.ListItemRendererFn)
	h.listDataItemRenderers = make(map[string]screen.ListDataItemRendererFn)
	h.listLengths = make(map[string]screen.ListLengthFn)
	h.onListItemSelectedHandlers = make(map[string]screen.ListItemHandlerFn)
	h.onListItemUnselectedHandlers = make(map[string]screen.ListItemHandlerFn)
	h.onClickedHandlers = make(map[string]screen.ClickHandlerFn)
	h.onCheckChangedHandlers = make(map[string]screen.CheckHandlerFn)
	h.onDateSelectedHandlers = make(map[string]screen.DateSelectedHandlerFn)
	h.onOptionSelectedHandlers = make(map[string]screen.OptionSelectedHandlerFn)
	h.onValidationChangedHandlers = make(map[string]screen.ValidationChangedHandlerFn)
	return
}

// ScreenDefinition returns the screen definition for the ScreenHandler.
func (h *ScreenHandler) ScreenDefinition() ScreenDefinition {
	return h.screenDefinition
}

// RegisterElement registers an element with the ScreenHandler.
//
// This function is called for every element in the screen definition fow which
// an ID is defined.
func (h *ScreenHandler) RegisterElement(
	id string,
	elem fyne.CanvasObject,
	decorator fyne.CanvasObject,
) {
	h.exportedElements[id] = &screen.UIElement{Object: elem, Decorator: decorator}
}

func (h *ScreenHandler) LoadAsset(name string) (fh fs.File, err error) {
	fh, err = h.assetLoader(name)
	return
}

// RegisterListItemTemplate registers a ListItemTemplate with the ScreenHandler.
//
// Use this function to register the templates for the lists used in the
// screen definition.
func (h *ScreenHandler) RegisterListItemTemplate(
	name string,
	fn screen.ListItemTemplateFn,
) {
	h.listItemTemplates[name] = fn
}

// RegisterListDataItemRenderer registers a ListDataItemRenderer with the ScreenHandler.
//
// Use this function to register the renderers for the lists used in the
// screen definition.
func (h *ScreenHandler) RegisterListDataItemRenderer(
	name string,
	fn screen.ListDataItemRendererFn,
) {
	h.listDataItemRenderers[name] = fn
}

// RegisterListItemRenderer registers a ListItemRenderer with the ScreenHandler.
//
// Use this function to register the renderers for the lists used in the
// screen definition.
func (h *ScreenHandler) RegisterListItemRenderer(
	name string,
	fn screen.ListItemRendererFn,
) {
	h.listItemRenderers[name] = fn
}

// RegisterListLength registers a ListLength with the ScreenHandler.
//
// Use this function to register the lengths for the lists used in the
// screen definition.
func (h *ScreenHandler) RegisterListLength(
	name string,
	fn screen.ListLengthFn,
) {
	h.listLengths[name] = fn
}

// RegisterOnListItemSelectedHandler registers a OnListItemSelectedHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnListItemSelectedHandler(
	name string,
	fn screen.ListItemHandlerFn,
) {
	h.onListItemSelectedHandlers[name] = fn
}

// RegisterOnListItemUnselectedHandler registers a OnListItemUnselectedHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnListItemUnselectedHandler(
	name string,
	fn screen.ListItemHandlerFn,
) {
	h.onListItemUnselectedHandlers[name] = fn
}

// RegisterOnClickHandler registers a OnClickHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnClickHandler(
	name string,
	fn screen.ClickHandlerFn,
) {
	h.onClickedHandlers[name] = fn
}

// RegisterOnCheckChangedHandler registers a OnCheckChangedHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnCheckChangedHandler(
	name string,
	fn screen.CheckHandlerFn,
) {
	h.onCheckChangedHandlers[name] = fn
}

// RegisterOnDateSelectedHandler registers a OnDateSelectedHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnDateSelectedHandler(
	name string,
	fn screen.DateSelectedHandlerFn,
) {
	h.onDateSelectedHandlers[name] = fn
}

// RegisterOnOptionSelectedHandler registers a OnOptionSelectedHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnOptionSelectedHandler(
	name string,
	fn screen.OptionSelectedHandlerFn,
) {
	h.onOptionSelectedHandlers[name] = fn
}

// RegisterOnValidationChangedHandler registers a OnValidationChangedHandler with the ScreenHandler.
//
// Use this function to register the handler functions used in the screen
// definition.
func (h *ScreenHandler) RegisterOnValidationChangedHandler(
	name string,
	fn screen.ValidationChangedHandlerFn,
) {
	h.onValidationChangedHandlers[name] = fn
}

// GetBinding returns the binding with the given name.
//
// This function forwards the call to the controller. In the controller the
// required bindings should be mapped to the screen elements.
func (h *ScreenHandler) GetBinding(name string) binding.DataItem {
	return h.viewModel.GetBinding(name)
}

// GetValidator returns the validator with the given name.
//
// This function forwards the call to the controller. In the controller the
// required validators should be mapped to the screen elements.
func (h *ScreenHandler) GetValidator(name string) fyne.StringValidator {
	return h.viewModel.GetValidator(name)
}

// GetElement returns the UIElement with the given ID.
//
// This function allows you to retrieve the exported elements (given an ID in
// the screen definition). The UIElement contains the object and the decorator.
// Should no decorator be present, both point to the same widget. If a decorator
// is present it's advices to do hide and show operations on the decorator, and
// all other operators on the object.
func (h *ScreenHandler) GetElement(id string) *screen.UIElement {
	elem, ok := h.exportedElements[id]
	if !ok {
		log.Printf("element %s not found", id)
		return nil
	}
	return elem
}

func (h *ScreenHandler) ReplaceElementObject(
	containerId string,
	id string,
	newDecorator fyne.CanvasObject,
	newObject fyne.CanvasObject,
) {
	containerElement := h.GetElement(containerId)
	if containerElement == nil {
		return
	}
	containerObj := containerElement.Object.(*fyne.Container)

	element := h.GetElement(id)
	if element == nil {
		return
	}
	decorator := element.Decorator

	allObjs := containerObj.Objects
	replaced := false
	for i, obj := range allObjs {
		if obj == decorator {
			allObjs[i] = newDecorator
			replaced = true
			break
		}
	}

	if replaced {
		h.exportedElements[id].Decorator = newDecorator
		h.exportedElements[id].Object = newObject
	}

	containerObj.Refresh()
}

// GetLocalizer returns the i18n.Localizer used for localization.
func (h *ScreenHandler) GetLocalizer() *i18n.Localizer {
	return h.localizer
}

// GetIcon returns the icon with the given name.
//
// This handler only implements the default theme icons. If you wish to support
// other items, wrap this ScreenHandler and implement the loading of the icons
// yourself.
func (h *ScreenHandler) GetIcon(iconName string) fyne.Resource {
	if strings.HasPrefix(iconName, "theme.") {
		iconName := strings.SplitN(iconName, ".", 2)[1]
		return theme.DefaultTheme().Icon(fyne.ThemeIconName(iconName))
	}
	log.Printf("icon %s not found", iconName)
	return nil
}

// GetListItemTemplate returns the ListItemTemplate with the given name.
func (h *ScreenHandler) GetListItemTemplate(name string) screen.ListItemTemplateFn {
	fn, ok := h.listItemTemplates[name]
	if !ok {
		log.Printf("list template %s not found", name)
		return nil
	}
	return fn
}

// GetListDataItemRenderer returns the ListDataItemRenderer with the given name.
func (h *ScreenHandler) GetListDataItemRenderer(name string) screen.ListDataItemRendererFn {
	fn, ok := h.listDataItemRenderers[name]
	if !ok {
		log.Printf("list renderer %s not found", name)
		return nil
	}
	return fn
}

// GetListItemRenderer returns the ListItemRenderer with the given name.
func (h *ScreenHandler) GetListItemRenderer(name string) screen.ListItemRendererFn {
	fn, ok := h.listItemRenderers[name]
	if !ok {
		log.Printf("list renderer %s not found", name)
		return nil
	}
	return fn
}

// GetListLength returns the ListLength with the given name.
func (h *ScreenHandler) GetListLength(name string) screen.ListLengthFn {
	fn, ok := h.listLengths[name]
	if !ok {
		log.Printf("list length %s not found", name)
		return nil
	}
	return fn
}

// GetOnListItemSelectedHandler returns the OnListItemSelectedHandler with the given name.
func (h *ScreenHandler) GetOnListItemSelectedHandler(name string) screen.ListItemHandlerFn {
	fn, ok := h.onListItemSelectedHandlers[name]
	if !ok {
		log.Printf("list item selected handler %s not found", name)
		return nil
	}
	return fn
}

// GetOnListItemUnselectedHandler returns the OnListItemUnselectedHandler with the given name.
func (h *ScreenHandler) GetOnListItemUnselectedHandler(name string) screen.ListItemHandlerFn {
	fn, ok := h.onListItemUnselectedHandlers[name]
	if !ok {
		log.Printf("list item unselected handler %s not found", name)
		return nil
	}
	return fn
}

// GetOnClickedHandler returns the OnClickedHandler with the given name.
func (h *ScreenHandler) GetOnClickedHandler(name string) screen.ClickHandlerFn {
	fn, ok := h.onClickedHandlers[name]
	if !ok {
		log.Printf("clicked handler %s not found", name)
		return nil
	}
	return fn
}

// GetOnCheckChangedHandler returns the OnCheckChangedHandler with the given name.
func (h *ScreenHandler) GetOnCheckChangedHandler(name string) screen.CheckHandlerFn {
	fn, ok := h.onCheckChangedHandlers[name]
	if !ok {
		log.Printf("check changed handler %s not found", name)
		return nil
	}
	return fn
}

// GetOnDateSelectedHandler returns the OnDateSelectedHandler with the given name.
func (h *ScreenHandler) GetOnDateSelectedHandler(name string) screen.DateSelectedHandlerFn {
	fn, ok := h.onDateSelectedHandlers[name]
	if !ok {
		log.Printf("date selected handler %s not found", name)
		return nil
	}
	return fn
}

func (h *ScreenHandler) GetOnOptionSelectedHandler(name string) screen.OptionSelectedHandlerFn {
	fn, ok := h.onOptionSelectedHandlers[name]
	if !ok {
		log.Printf("option selected handler %s not found", name)
		return nil
	}
	return fn
}

// GetOnValidationChangedHandler returns the OnValidationChangedHandler with the given name.
func (h *ScreenHandler) GetOnValidationChangedHandler(name string) screen.ValidationChangedHandlerFn {
	fn, ok := h.onValidationChangedHandlers[name]
	if !ok {
		log.Printf("validation changed handler %s not found", name)
		return nil
	}
	return fn
}

func (h *ScreenHandler) RegisterResizeCallback(cb ResizeCallbackFn) {
	h.screenDefinition.RegisterResizeCallback(cb)
}

func (h *ScreenHandler) RegisterMoveCallback(cb MoveCallbackFn) {
	h.screenDefinition.RegisterMoveCallback(cb)
}