import { KnockoutComponentBinder } from "../ko/knockoutComponentBinder";
import { Bag } from "../bag";
import { IModelBinder, IWidgetBinding, IWidgetHandler, IWidgetOrder, WidgetBinding, WidgetDefinition, WidgetEditorDefinition } from "../editing";
import { EventManager, Events } from "../events";
import { IInjector } from "../injection";
import { StyleCompiler, StyleManager } from "../styles";
import { IWidgetService, ViewModelBinder } from "../widgets";
import { ComponentFlow } from "../components";


const defaultWidgetIconClass = "widget-icon widget-icon-component";

export class WidgetService implements IWidgetService {
    private widgetEntries: Bag<WidgetDefinition> = {};
    private widgetEditorEntries: Bag<WidgetEditorDefinition> = {};

    constructor(
        private readonly widgetHandlers: IWidgetHandler<unknown>[],
        private readonly injector: IInjector
    ) { }

    private async getWidgetOrdersLegacy(): Promise<IWidgetOrder<unknown>[]> {
        const widgetOrders = new Array<IWidgetOrder<unknown>>();

        const tasks = this.widgetHandlers.map(async (handler: IWidgetHandler<unknown>) => {
            if (handler.getWidgetOrder) {
                const order = await handler.getWidgetOrder();
                widgetOrders.push(order);
            }
        });

        await Promise.all(tasks);

        return widgetOrders;
    }

    public async getWidgetOrders(): Promise<IWidgetOrder<unknown>[]> {
        const widgetNames = Object.keys(this.widgetEditorEntries);

        const orders = [];

        widgetNames.forEach(widgetName => {
            const definition = this.widgetEditorEntries[widgetName];

            if (definition.selectable === false) {
                return; // skip adding non-selectable widget to "Add widget" dialog
            }

            const handler: IWidgetHandler<unknown> = this.getWidgetHandlerByWidgetName(widgetName);

            const order: IWidgetOrder<unknown> = {
                name: widgetName,
                displayName: definition.displayName,
                category: definition.category,
                iconClass: definition.iconClass,
                iconUrl: definition.iconUrl,
                requires: definition.requires || [],
                createModel: handler.getWidgetModel
            };

            if (!order.iconClass && !order.iconUrl) {
                order.iconClass = defaultWidgetIconClass;
            }

            orders.push(order);
        });

        let legacyOrders = await this.getWidgetOrdersLegacy();

        // filtering out duplicates
        legacyOrders = legacyOrders.filter(legacyOrder => !orders.some(order => order.name == legacyOrder.name));

        return orders.concat(legacyOrders);
    }

    public getWidgetHandler(widgetBinding: IWidgetBinding<any, any>): IWidgetHandler<unknown> {
        let widgetHandler = this.getWidgetHandlerByWidgetName(widgetBinding.name);

        if (widgetHandler) {
            return widgetHandler;
        }

        if (!widgetBinding.handler) {
            return null;
        }

        return this.getWidgetHandlerByType(widgetBinding.handler);
    }

    private resolveComponent<TComponent>(component: TComponent | Function | string): TComponent {
        let componentInstance: TComponent;

        if (typeof component === "string") {
            componentInstance = this.injector.resolve(component);
        }
        else if (typeof component === "function") {
            componentInstance = this.injector.resolveClass(component);
        }
        else {
            componentInstance = <TComponent>component;
        }

        return componentInstance;
    }

    private getWidgetHandlerByDefinition(editorDefintion: WidgetEditorDefinition): IWidgetHandler<unknown> {
        return this.resolveComponent<IWidgetHandler<unknown>>(editorDefintion.handlerComponent);
    }

    private getWidgetHandlerByWidgetName(widgetName: string): IWidgetHandler<unknown> {
        const editorDefintion = this.widgetEditorEntries[widgetName];

        if (!editorDefintion) {
            return null;
        }

        return this.getWidgetHandlerByDefinition(editorDefintion);
    }

    /**
     * @deprecated Used to resolve handlers in legacy model.
     */
    private getWidgetHandlerByType(handlerType: any): IWidgetHandler<unknown> {
        if (!handlerType) {
            throw new Error(`Parameter "handlerType" not specified.`);
        }

        // legacy logic
        const widgetHandler = this.widgetHandlers.find(x => x instanceof handlerType);

        if (!widgetHandler) {
            throw new Error(`No widget handlers of type "${handlerType.name}" registered. Use "registerWidgetHandler" method in IWidgetService to register it.`);
        }

        return widgetHandler;
    }

    public getModelBinder<TModel>(widgetName: string): IModelBinder<TModel> {
        const widgetDefinition = this.widgetEntries[widgetName];

        if (!widgetDefinition) {
            return null;
        }

        return this.resolveComponent<IModelBinder<TModel>>(widgetDefinition.modelBinder);
    }

    public async getWidgetModel(widgetName: string): Promise<unknown> {
        const handler = this.getWidgetHandlerByWidgetName(widgetName);
        const widgetModel = await handler.getWidgetModel();

        return widgetModel;
    }

    public registerWidget(widgetName: string, widgetDefinition: WidgetDefinition): void {
        if (!widgetName) {
            throw new Error(`Parameter "widgetName" not specified.`)
        }

        if (!widgetDefinition) {
            throw new Error(`Parameter "widgetDefinition" not specified.`)
        }

        if (!widgetDefinition.componentFlow) {
            widgetDefinition.componentFlow = ComponentFlow.None;
        }

        this.widgetEntries[widgetName] = widgetDefinition;

        if (widgetDefinition.alternativeNames) {
            widgetDefinition.alternativeNames.forEach(widgetName => {
                this.widgetEntries[widgetName] = widgetDefinition;
            });
        }
    }

    public unregisterWidget(widgetName: string): void {
        delete this.widgetEntries[widgetName];
        delete this.widgetEditorEntries[widgetName];
    }

    public registerWidgetEditor(widgetName: string, definition: WidgetEditorDefinition): void {
        if (!this.widgetEntries[widgetName]) {
            throw new Error(`Widget "${widgetName}" is not registered.`);
        }

        if (definition.requires === undefined) {
            definition.requires = [];
        }

        if (definition.draggable === undefined) {
            definition.draggable = true;
        }

        if (definition.selectable === undefined) {
            definition.selectable = true;
        }

        this.widgetEditorEntries[widgetName] = definition;
    }

    public unregisterWidgetEditor(widgetName: string): void {
        delete this.widgetEditorEntries[widgetName];
    }

    public getWidgetDefinitionForModel<TModel>(model: TModel): WidgetDefinition {
        const widgetNames = Object.keys(this.widgetEntries);

        const widgetName = widgetNames.find(widgetName => {
            const definition = this.widgetEntries[widgetName];
            const binder = this.getModelBinder(widgetName)

            if (!!binder.canHandleModel) {
                return binder?.canHandleModel(model, widgetName)
            }

            return model instanceof definition.modelDefinition
        });

        return this.widgetEntries[widgetName];
    }

    public getModelBinderForModel<TModel>(model: TModel): IModelBinder<TModel> {
        const values = Object.values(this.widgetEntries);
        const definition = values.find(x => model instanceof x.modelDefinition);

        if (!definition) {
            return null;
        }

        return this.resolveComponent<IModelBinder<TModel>>(definition.modelBinder);
    }

    public async createWidgetBinding<TModel, TViewModel>(definition: WidgetDefinition, model: TModel, bindingContext: Bag<any>): Promise<WidgetBinding<TModel, TViewModel>> {
        const widgetName = Object.keys(this.widgetEntries).find(key => this.widgetEntries[key] === definition);

        if (!widgetName) {
            return null;
        }

        const widgetDefinition = this.widgetEntries[widgetName];
        const editorDefinition = this.widgetEditorEntries[widgetName];
        const viewModelBinder = this.resolveComponent<ViewModelBinder<TModel, TViewModel>>(widgetDefinition.viewModelBinder);

        if (!viewModelBinder.modelToState) {
            throw new Error(`View model binder "${viewModelBinder.constructor.name}" doesn't have "modelToState" method defined.`);
        }

        if (!viewModelBinder.stateToInstance) {
            throw new Error(`View model binder "${viewModelBinder.constructor.name}" doesn't have "stateToInstance" method defined.`);
        }

        const widgetBinding = new WidgetBinding<TModel, TViewModel>();
        const eventManager = this.injector.resolve<EventManager>("eventManager");

        // 1. Common
        widgetBinding.componentBinder = this.injector.resolveClass(widgetDefinition.componentBinder);
        widgetBinding.componentDefinition = widgetDefinition.componentDefinition;
        widgetBinding.model = model;
        widgetBinding.layer = bindingContext.layer;

        // 2. Widget definition
        widgetBinding.name = widgetName;
        widgetBinding.wrapper = widgetDefinition.componentFlow;

        if (widgetDefinition.componentBinder === KnockoutComponentBinder) {
            // Knockout doesn't replace top-level node
            widgetBinding.wrapped = widgetBinding.wrapper !== ComponentFlow.None;
        }

        // 3. Widget editor definition
        if (editorDefinition) {
            widgetBinding.displayName = editorDefinition.displayName;
            widgetBinding.selectable = editorDefinition.selectable;
            widgetBinding.draggable = editorDefinition.draggable;

            if (editorDefinition.componentDefinition) {
                widgetBinding.editor = <any>editorDefinition.componentDefinition;
                widgetBinding.editorComponentBinder = this.injector.resolveClass(<any>editorDefinition.componentBinder);
                widgetBinding.editorScrolling = editorDefinition.editorScrolling;
                widgetBinding.editorResizing = editorDefinition.editorResizing
            }

            if (model["styles"] && !model["styles"]["instance"]) {
                const handler = this.getWidgetHandlerByDefinition(editorDefinition)

                if (handler.getStyleDefinitions) {
                    const styleCompiler = this.injector.resolve<StyleCompiler>("styleCompiler");
                    const styleDefinition = handler.getStyleDefinitions();
                    styleCompiler.backfillLocalStyles(model["styles"], styleDefinition);
                }
            }
        }

        const widgetState = {};
        const styleManager: StyleManager = bindingContext?.styleManager;

        await viewModelBinder.modelToState(model, widgetState, bindingContext);

        // 4. Binding events
        widgetBinding.applyChanges = async () => {
            await viewModelBinder.modelToState(model, widgetState, bindingContext);

            if (bindingContext?.styleManager && widgetState["styles"]?.styleSheet) {
                bindingContext.styleManager.setStyleSheet(widgetState["styles"]?.styleSheet);
            }

            viewModelBinder.stateToInstance(widgetState, widgetBinding.viewModel);
            eventManager.dispatchEvent(Events.ContentUpdate);
        };

        widgetBinding.onCreate = (componentInstance: TViewModel): void => {
            if (!componentInstance) {
                throw new Error(`Parameter "instance" not specified.`)
            }

            if (styleManager && widgetState["styles"]?.styleSheet) {
                styleManager.setStyleSheet(widgetState["styles"]?.styleSheet);
            }

            componentInstance["widgetBinding"] = widgetBinding;

            viewModelBinder.stateToInstance(widgetState, componentInstance);
        }

        widgetBinding.onDispose = () => {
            if (widgetState["styles"]?.styleSheet) {
                styleManager.removeStyleSheet(widgetState["styles"]?.styleSheet);
            }
        };

        return widgetBinding;
    }
}