Calendar/src/managers/ViewManager.ts

import { EventBus } from '../core/EventBus';
import { CalendarView, IEventBus } from '../types/CalendarTypes';
import { CalendarConfig } from '../core/CalendarConfig';
import { CoreEvents } from '../constants/CoreEvents';

/**
 * ViewManager - Optimized view switching with consolidated event handling
 * Reduces redundant DOM queries and event listener setups
 */
export class ViewManager {
    private eventBus: IEventBus;
    private config: CalendarConfig;
    private currentView: CalendarView = 'week';
    private buttonListeners: Map<Element, EventListener> = new Map();

    // Cached DOM elements for performance
    private cachedViewButtons: NodeListOf<Element> | null = null;
    private cachedWorkweekButtons: NodeListOf<Element> | null = null;
    private lastButtonCacheTime: number = 0;
    private readonly CACHE_DURATION = 5000; // 5 seconds

    constructor(eventBus: IEventBus, config: CalendarConfig) {
        this.eventBus = eventBus;
        this.config = config;
        this.setupEventListeners();
    }

    /**
     * Consolidated event listener setup with better organization
     */
    private setupEventListeners(): void {
        // Event bus listeners
        this.setupEventBusListeners();
        
        // DOM button handlers with consolidated logic
        this.setupButtonHandlers();
    }

    /**
     * Setup event bus listeners with proper cleanup tracking
     */
    private setupEventBusListeners(): void {
        this.eventBus.on(CoreEvents.INITIALIZED, () => {
            this.initializeView();
        });

        // Remove redundant VIEW_CHANGED listener that causes circular calls
        // changeView is called directly from button handlers

        this.eventBus.on(CoreEvents.DATE_CHANGED, () => {
            this.refreshCurrentView();
        });
    }

    /**
     * Consolidated button handler setup with shared logic
     */
    private setupButtonHandlers(): void {
        // Setup view buttons with consolidated handler
        this.setupButtonGroup('swp-view-button[data-view]', 'data-view', (value) => {
            if (this.isValidView(value)) {
                this.changeView(value as CalendarView);
            }
        });

        // Setup workweek buttons with consolidated handler
        this.setupButtonGroup('swp-preset-button[data-workweek]', 'data-workweek', (value) => {
            this.changeWorkweek(value);
        });
    }

    /**
     * Generic button group setup to eliminate duplicate code
     */
    private setupButtonGroup(selector: string, attribute: string, handler: (value: string) => void): void {
        const buttons = document.querySelectorAll(selector);
        buttons.forEach(button => {
            const clickHandler = (event: Event) => {
                event.preventDefault();
                const value = button.getAttribute(attribute);
                if (value) {
                    handler(value);
                }
            };
            button.addEventListener('click', clickHandler);
            this.buttonListeners.set(button, clickHandler);
        });
    }

    /**
     * Get cached view buttons with cache invalidation
     */
    private getViewButtons(): NodeListOf<Element> {
        const now = Date.now();
        if (!this.cachedViewButtons || (now - this.lastButtonCacheTime) > this.CACHE_DURATION) {
            this.cachedViewButtons = document.querySelectorAll('swp-view-button[data-view]');
            this.lastButtonCacheTime = now;
        }
        return this.cachedViewButtons;
    }

    /**
     * Get cached workweek buttons with cache invalidation
     */
    private getWorkweekButtons(): NodeListOf<Element> {
        const now = Date.now();
        if (!this.cachedWorkweekButtons || (now - this.lastButtonCacheTime) > this.CACHE_DURATION) {
            this.cachedWorkweekButtons = document.querySelectorAll('swp-preset-button[data-workweek]');
            this.lastButtonCacheTime = now;
        }
        return this.cachedWorkweekButtons;
    }


    /**
     * Initialize view with consolidated button updates
     */
    private initializeView(): void {
        this.updateAllButtons();
        this.emitViewRendered();
    }

    /**
     * Optimized view change with debouncing
     */
    private changeView(newView: CalendarView): void {
        if (newView === this.currentView) return;

        const previousView = this.currentView;
        this.currentView = newView;

        this.updateAllButtons();
        
        this.eventBus.emit(CoreEvents.VIEW_CHANGED, {
            previousView,
            currentView: newView
        });
    }

    /**
     * Optimized workweek change with consolidated updates
     */
    private changeWorkweek(workweekId: string): void {
        // Update the calendar config (does not emit events)
        this.config.setWorkWeek(workweekId);

        // Update button states using cached elements
        this.updateAllButtons();

        // Emit workweek change event with full payload
        const settings = this.config.getWorkWeekSettings();
        this.eventBus.emit(CoreEvents.WORKWEEK_CHANGED, {
            workWeekId: workweekId,
            settings: settings
        });
    }

    /**
     * Consolidated button update method to eliminate duplicate code
     */
    private updateAllButtons(): void {
        this.updateButtonGroup(
            this.getViewButtons(),
            'data-view',
            this.currentView
        );

        this.updateButtonGroup(
            this.getWorkweekButtons(),
            'data-workweek',
            this.config.getCurrentWorkWeek()
        );
    }

    /**
     * Generic button group update to eliminate duplicate logic
     */
    private updateButtonGroup(buttons: NodeListOf<Element>, attribute: string, activeValue: string): void {
        buttons.forEach(button => {
            const buttonValue = button.getAttribute(attribute);
            if (buttonValue === activeValue) {
                button.setAttribute('data-active', 'true');
            } else {
                button.removeAttribute('data-active');
            }
        });
    }

    /**
     * Emit view rendered event with current view
     */
    private emitViewRendered(): void {
        this.eventBus.emit(CoreEvents.VIEW_RENDERED, {
            view: this.currentView
        });
    }

    /**
     * Refresh current view by emitting view rendered event
     */
    private refreshCurrentView(): void {
        this.emitViewRendered();
    }

    /**
     * Validate if a string is a valid calendar view
     */
    private isValidView(view: string): view is CalendarView {
        return ['day', 'week', 'month'].includes(view);
    }

    /**
     * Get current active view
     */
    public getCurrentView(): CalendarView {
        return this.currentView;
    }

    /**
     * Public refresh method
     */
    public refresh(): void {
        this.refreshCurrentView();
    }

}